MEMCAL
Gift of
G.H. Evans, M.D.
ANATOMY AND PHYSIOLOGY
FOR TRAINING SCHOOLS AND OTHER EDUCATIONAL INSTITUTIONS
BUNDY
TEXT-BOOK
OF
ANATOMY AND PHYSIOLOGY
FOR TRAINING SCHOOLS AND OTHER EDUCATIONAL INSTITUTIONS
BY
ELIZABETH R. BUNDY, M. D.
MEMBER OF THE MEDICAL STAFF OF THE WOMAN'S HOSPITAL OF PHILADELPHIA; GYNECOLOGIST
NEW JERSEY TRAINING SCHOOL, VINELAND; FORMERLY ADJUNCT PROFESSOR OF
ANATOMY, AND DEMONSTRATOR OF ANATOMY IN THE WOMAN'S MEDICAL
COLLEGE OF PENNSYLVANIA; FORMERLY SUPERINTENDENT
OF CONNECTICUT TRAINING SCHOOL FOR NURSES
NEW HAVEN, ETC.
FOURTH EDITION REVISED AND ENLARGED
WITH A GLOSSARY AND 243 ILLUSTRATIONS 46 OF WHICH, ARE .PRIJNT^D I,N. COLORS
PHILADELPHIA
P. BLAKISTON'S SON & CO
1012 WALNUT STREET
COPYRIGHT, 1906, BY P. BLAKISTON'S SON & Co.
PRINTED, 1906. REPRINTED, 1907, 1909, 1910, 1911.
SECOND EDITION. COPYRIGHT, 1912, BY P. BLAKISTON'S SON & Co.
PRINTED, 1912.
REPRINTED WITH CORRECTIONS, 1913. REPRINTED SEPTEMBER, 1913.
THIRD EDITION. COPYRIGHT, 1914, BY P. BLAKISTON'S SON & Co.
PRINTED, 1914. REPRINTED WITH CORRECTIONS, OCTOBER, 1914.
REPRINTED. FOURTH EDITION.
COPYRIGHT, 1916, BY P. BLAKISTON'S SON & Co. PRINTED, 1916.
THE. MAPLE- PRESS. .YORK. PA
PREFACE TO THE FOURTH EDITION
The fourth edition of this book, like the two preceding ones, has been prepared with the hope that by certain changes and addi- tions, it will meet the still increasing demand for a text-book which shall present the subject of Physiology as well as Anatomy, in a manner both practical and available to the student.
To include these two large subjects under one cover, with the necessary brevity and still with sufficient clearness, is a task with difficulties of its own, but it is undertaken with the earnest endeavor to meet the demand created by present requirements as well as may be with the inevitable problem of selection or omission, which, however carefully considered, must remain a matter of judgment and experience.
The plan has been adopted in the descriptions — to emphasize those characteristics which are most essential and which may be most readily grasped and, by reason of practical application, remembered.
The original purpose of the author — to provide a special text- book of Anatomy — still remains in effect, since only by means of a knowledge of structure and form can an understanding of use or function be reached.
The student is referred to the Glossary for the meaning of unfamiliar terms, and to the lines of smaller type for various par- ticulars which may be found useful as experience indicates the need for reference.
The original illustrations drawn for this book are all retained and several new ones from other sources are added.
Again the author desires to express appreciation of suggestions and kind words from officials of schools where the book is in use.
PHILADELPHIA ELIZABETH R. BUNDY.
3;iU'J
PREFACE AND DEDICATION TO FIRST EDITION
The pupil-nurse in a training-school has very few hours at com- mand for the study of text-books, but it is hoped that she may find in this "Anatomy for Nurses" an aid to the acquirement of that knowledge of the human body which is essential to the full understanding of her important duties.
In preparing a book of this kind, the inevitable difficulty of selection, when dealing with a subject of such magnitude, is at once manifest. What appears from one point of view to be of minor interest, is from another paramount in importance; while in truth, no detail is of itself insignificant.
The author trusts that in the present work such matters as are not available for immediate use in the hospital ward may still be of value, to meet the growing need of the graduate-nurse as she finds herself developing with the practice of her profession. It was, in part, to meet this frequently expressed need that the work was
undertaken.
*********
Concerning the use of anatomic terms, indications point to the general adoption of the nomenclature accepted by the German Anatomical Society at the meeting of 1895, in Basle, Switzerland. The B. N. A., as it is called, will soon be in use among the younger physicians at least; therefore, many of the terms belonging to it are here introduced, and several tables are given which include names not found in the text.
The author gratefully acknowledges her indebtedness to Dr. Marie L. Bauer for valuable aid in the preparation of the book, and to Drs. Frances C. Van Gasken and J. William McConnell for assistance in the reading of proofs and for helpful suggestions.
The original illustrations, most of which are printed in colors, arerdrawn by Chas. F. Bauer.
To the members of the nursing profession, with cherished recol- lections of labors and responsibilities shared, this Text-book of Anatomy is dedicated.
ELIZABETH R. BUNDY. vii
CONTENTS
INTRODUCTORY
PAGE
Plan of study; anatomic terms; muscle, nerve, and connective tissues; epithelial tissues; gland structure; serous and mucous membranes; processes included in metabolism of the body; chemical elements and symbols i
CHAPTER I BONE TISSUE AND BONE CLASSIFICATION. ARTICULATIONS
Chemical composition of bone; structure of osseous tissue; marrow; medullary and nutrient canals; shapes and surfaces; periosteum; ossification; divisions of the skeleton; joint movements; reward n
CHAPTER II BONES AND ARTICULATIONS OF THE SKULL
Bones of the cranium; sutures and fontanelles; bones of the face; the mandibular joint; the skull as a whole; four larger fossae of the skull; the teeth; dentition; care of the teeth; clinical and obstetric notes 20
CHAPTER III BONES AND ARTICULATIONS OF THE SPINAL COLUMN AND TRUNK
The vertebrae; ligamenta flava; ligamentum nuchce; movements of spinal column; spinal curves; bones and articulations of the thorax; the pelvic girdle; sacro- sciatic ligaments; dorsal and ventral, or neural and visceral cavities; clinical and obstetric notes 39
CHAPTER IV BONES AND ARTICULATIONS OF THE EXTREMITIES
Bones of the upper extremity; pronation and supination; bones of the lower extremity; patella; Y -ligament, crucial ligaments; arches of the foot; com- parison of extremities; articular nerves; clinical and surgical notes; special notes 54
CHAPTER V COMPLETION, REPAIR AND PHYSIOLOGY OF BONES
Completion of long bones; the skeleton at different ages; bones in infancy; green- stick fracture; rachitis; spina bifida; process of repair; physiology of bone tissues; surgical and special notes '. 75
ix
X CONTENTS
CHAPTER VI
THE CONNECTIVE TISSUE FRAMEWORK AND SKELETAL MUSCLE
SYSTEM
Fascia, deep and superficial; inguinal ligament; bursae; structure of muscles; tendon and aponeurosis; origin and insertion; muscles of expression, of neck and thorax; abdominal muscles and linea alba; sheath of rectus, semilunar and transverse lines. Diaphragm; surgical and clinical notes; special points . 80
CHAPTER VII MUSCLES OF THE EXTREMITIES
Structure and action of muscles of upper extremity; axillary space; pronators and supinators; vaginal synovial membranes; annular ligaments; palmar fascia; muscles of lower extremity; popliteal space; annular ligaments; physiology of muscle tissue; muscle tissue a source of heat and electricity; tetanus; cramp; fatigue; clinical notes; special points; classification by action. . . . 101
CHAPTER VIII THE ORGANS OF DIGESTION
Alimentary tract or canal; glands of digestive apparatus; enzymes; saliva, alka- line; the stomach; gastric juice, acid; the intestine; intestinal fluids, alkaline; villi; ileo-colic valve; cecum and appendix; rectum and anal sphincters; peristalsis; liver and gall bladder; bile; the porta; notes, clinical and surgical . 130
CHAPTER IX PHYSIOLOGY OF THE DIGESTIVE ORGANS. FOOD. ABSORPTION
Four classes of foods in dietary; air as food; food combination; reasons for cook- ing food; digestion, mechanical and chemical; mastication, insalivation; gastric digestion (acid), chyme; intestinal digestion chyle; peristalsis; absorp- tion; clinical notes 153
CHAPTER X THE BLOOD AND CIRCULATORY ORGANS
Blood-corpuscles or cells. Erythrocytes and leucocytes; ameboid movements, diapedesis; plasma (alkaline); normal saline solution; arteries, capillaries, veins^bhe heart; chambers and valves of heart; endocardium; systole and diastole; the pulse; pericardium; course of blood through the heart; innerva- tion of the heart; surgical an d clinical notes; important notes 171
CHAPTER XI THE CIRCULATION OF THE BLOOD
Pulmonary vessels; aorta and branches; arteries of the head, of the upper ex- tremity; palmar arches; thoracic, abdominal and pelvic arteries; arteries of the lower extremity; veins, deep and superficial; jugular veins; azygos veins; superior vena cava; inferior vena cava; portal circulation; fetal circulation; collateral circulation; clinical and surgical notes 187
CONTENTS XI
CHAPTER XII PHYSIOLOGY OF THE BLOOD
Important functions of the blood; coagulation; formation of fibrin; coagulation- time; phagocytosis; opsonins and opsonic index; antibodies; hypodermo- clysis; transfusion; osmosis; blood pressure; hemorrhage and control of hem- orrhages; clinical notes', important notes 213
CHAPTER XIII THE LYMPH SYSTEM
Lymph spaces, capillaries, and vessels; lymph, origin; lymph glands or nodes; edema, effusion; thoracic duct; right lymphatic duct; principal nodes; the lymph stream; hyperemia, metastasis; physiology of lymph system; clinical notes 221
CHAPTER XIV THE RESPIRATORY ORGANS AND RESPIRATION
The respiratory tract; the nose, nares and choanae; the larynx; trachea, bronchi and bronchial tubes; ciliated epithelium; air cells; the lungs; the pleurae; respiratory movements; physiology of respiratory organs; ventilation; respiration and heat production; modifications of breathing; clinical notes. 231
CHAPTER XV ELIMINATION
Organs of elimination; the kidney; structure of the kidney; urinary bladder; ure- thral caruncle; physiology of the kidney; urine; excretion of urine; quantity and variations; importance of the process; nephritis; albuminuria; renal casts; malposition of kidney; floating kidney 244
CHAPTER XVI ELIMINATION (Continued)
The skin; structure of the skin; layers; epidermis and derma, or cuticle and corium; papillae; vascularity of skin; elasticity; sensibility; panniculus adipo- sus; glands of skin; appendages; hair; nails, structure of; physiology qj^skin; protective; excretory; organ of sense of touch; importance of perspiration; evaporation; diaphoresis 253
CHAPTER XVII MAMMARY GLANDS. DUCTLESS GLANDS OR ENDOCRIN SYSTEM
Structure of mammary gland; milk; colostrum; mammary abscess; ductless glands and internal secretions or autocoid substances; hormones, chilones; the spleen, structure and blood supply; leukemia; the pancreas structure and blood supply; adrenals, adrenalin; thyroid body; cretinism; thymus body an infantile structure; pituitary body or hypophysis; chromaflfin tissues. 260
XII CONTENTS
CHAPTER XVIII METABOLISM
Secretion and secreting organs; excretion and excreting organs; general metabo- lism; uses of food; values in metabolism; calorific value; diet charts; influ- ences effecting metabolim; animal heat; heat production; heat dissipation; range of normal temperature; preservation of heat 269
CHAPTER XIX THE NERVE SYSTEM
Two divisions of the nerve system, cerebro-spinal and sympathetic; the neuron, cell body and nerve fiber; cerebro-spinal division; gray and white nerve tissues; nerve centers; spinal cord and membranes; structure of spinal nerves; surgical and clinical notes 277
CHAPTER XX THE SPINAL NERVES
Anterior and posterior divisions; the cauda equina; cervical plexus, phrenic nerve; brachial plexus, radial, ulnar and median nerves; lumbar plexus, femoral nerve; sacral plexus, sciatic nerves 284
CHAPTER XXI THE BRAIN AND CRANIAL NERVES
Structure of brain, cortex and fibers; fissures; ganglia; internal capsule; cere- bellum; medulla oblongata; pons; crura; ventricles of brain; membranes of brain; cranial nerves; physiology of brain and cranial nerves; cerebral localization, surgical and clinical notes 299
CHAPTER XXII THE SYMPATHETIC DIVISION OF THE NERVE SYSTEM
Vertebral ganglia; cardiac and splanchnic nerves; cardiac and celiac (solar) plexuses; semilunar ganglia; functions of sympathetic nerves; vasomotor and reflex, presiding over visceral action; functions of nerve system as a whole; Important notes; Summary 316
CHAPTER XXIII THE SPECIAL SENSES
General and special sensation; the sense of smell, olfactory region; the sense of touch, touch corpuscles; the sense of taste, taste buds; the sense of hearing, external ear and auditory canal; middle ear or tympanum and auditory tube; internal ear or labyrinth; acoustic nerves 325
CONTENTS Xlll
CHAPTER XXIV THE SENSE OF SIGHT. THE VOICE
The sense of sight; structure of eyeball; myopia; hyperopia; astigmatism; range of accommodation; eyelids, lacrimal gland; associated movements; the voice; vocal cords; organs of speech 335
CHAPTER XXV THE PELVIC ORGANS
Organs of male pelvis; of female pelvis; the uterus; uterine or Fallopian tubes; the ovaries, ovulation; corpus luteum; menstruation; the menopause; the vagina and infra- vaginal portion of cervix uteri; the pudendum; the peri- neum; the testes and spermatic cord; peritoneum of pelvis; impregnation; decidual membranes; placenta; pregnancy; the lochia 346
CHAPTER XXVI A BRIEF STUDY OF IMPORTANT REGIONS
The head; the neck; thorax and thoracic viscera; abdomen, abdominal viscera and peritoneum; the ischio-rectal fossa; the axillary space; the ante-cubital space; Scarpa's triangle or the femoral trigone; Hunter's canal or the ad- ductor canal; the popliteal space; the inguinal rings and inguinal canal; the femoral rings and femoral canal; hernia; the extremities compared; review notes; points for compression of larger arteries of the body 360
CHAPTER XXVII REFERENCE TABLES
The systemic arteries; names of systemic arteries and veins according to the
B. N. A 379
Glossary 380
Index 401
ANATOMY AND PHYSIOLOGY
INTRODUCTORY
Anatomy deals with the structure of the body in its different parts; physiology teaches the uses or functions of those parts.
PLAN OF STUDY
We shall study first the framework of the body — the bones which give support to all other structures, with the joints by which they are held together, either loosely or firmly; and the muscles by which they are moved and still further connected.
Afterward will be presented the organs or viscera (which are enclosed in the two general cavities formed by the bones and muscles) with their nerve supply, and the system of vessels by which the entire body receives its nutriment. We shall see that all these parts are wrapped in delicate connective tissue, and held in place by bands and sheaths of the same substance. The mus- cles are stretched upon the bones, the firm layers and partitions of deep fascia bind them in place, the wrapping of superficial fascia keeps them warm and flexible, and the skin or integument makes an elastic and sufficient covering for the whole.
The study of the nerves by which these structures receive their stimulus, and the action and interaction of the various parts, will follow.
The organs of the special senses receive attention, and the last section is devoted to a review of the several regions of the body which, it is hoped, will prove interesting and profitable.
ANATOMIC USE OF TERMS
The anatomic position is that with the face toward the ob- server and the palms turned forward, and the terms anterior, posterior, right, left, etc., are to be understood with this position
2 ANATOMY AND PHYSIOLOGY
in mind. Thus, the anterior surface of the hand is always the palm; and, if we speak of any part as situated to the right we mean that it is nearer to the right side of the body which we are studying (which for convenience we will call the " subject")? but it has no relation whatever to the right side of the student. Of course the words superior and inferior are easily understood, but the use of the words medial and lateral (formerly internal and external) requires special mention. Imagine a line drawn through the middle of the head and trunk and striking the floor between the feet, thus dividing the body into right and left halves. This is called the median line. Any part or surface of one-half of the body is said to be medial to another part if it is nearer the median line while in the anatomic position, or lateral to another part if it is farther from the median line.
All of these terms once applied to a part of the body belong to it always. For example, the little finger is always medial to the others and the great toe is likewise medial, because these relations are established once for all while the subject is in the anatomic position. Likewise, the palm is the anterior surface of the hand even if it be temporarily turned backward.
The words exterior and interior are applied to the parts of the body which are on the surface or within, respectively.
Proximal means nearer to the head; distal, farther from the head. Thus we may speak of the proximal end of the finger, or the distal end of a toe, or the proximal end and distal end of an arm or a leg.
Certain words have been so long applied in a special sense in connection with anatomic relations and physiologic processes that usage has made them technical, that is, they have come to possess a professional meaning.
Hilum (literally a little thing) is applied to a place on the surface of an organ; a depression usually, where the vessels and nerves enter and leave it. Thus, we see the hilum of the kidney, of the lung, of the spleen. The hilum is always found on the medial or most protected surface of an organ. (In the case of the liver it is on the inferior surface and is called the porta or gateway.}
Sinus (literally a hollow or indentation) is applied in anatomy to a hollow or enlarged space within an organ, containing either air or fluid. Air sinuses are hollow spaces (almost enclosed), con-
TECHNICAL USE OF TERMS 3
nected with the nasal passages; these are cavities in the cranial and facial bones. Lymph sinuses are the spaces within lymph glands. They contain lymph (in some glands — blood). Sinuses containing fluid are large channels in the outer membrane of the brain — containing venous blood. Other blood sinuses are found in the heart. The sinus of the kidney is the hollow which is reached through the hilum which leads into it; this contains urine. In surgery a sinus is a narrow abnormal channel through the tissues (usually lined by or connected with an ulcerating surface). Center and periphery are so used (technically) in connection with the nervous system. The center is the cell or cells to which a nerve must belong and be connected with in order to be active. It need not necessarily be in the middle of a part — some of the most important centers are on the surface of the brain. The periphery is the location of the extremity of the nerve. Literally it signifies the outer boundary or the outside of a thing, but when used in connection with a nerve it refers to the end farthest from the cell or center, whether within or without the body.
Centrifugal nerves transmit from center to periphery (they are efferent). Centripetal nerves transmit from periphery to center (they are afferent}. Efferent vessels carry blood from organs; afferent vessels carry blood to organs.
Stimulus in physiology signifies any agency which causes a tissue or an organ to perform its function. A natural stimulus is a normal exciting cause and leads to normal action or function.
An element is, in chemistry, a substance which cannot be divided into other substances. The most important elements in the human body are comparatively few. They will be referred to, sometimes by name, sometimes by symbol. By agreement, certain letters stand for certain elements (usually the initials of their Latin names).
0 is the symbol for Oxygen
H is the symbol for Hydrogen
N is the symbol for Nitrogen
C is the symbol for Carbon
S is the symbol for Sulphur
Fe is the symbol for Iron (Ferrum)
P is the symbol for Phosphorus
K is the symbol for Potassium (Kalium)
Na is the symbol for Sodium (Natrium)
4
ANATOMY AND PHYSIOLOGY
(Combinations frequently used are C02 for carbon dioxide or "carbonic acid gas" H^O for water.}
Food principles are simple or compound substances, composed of one or several elements. They are broadly classed as, i. con- taining nitrogen , nitrogenous, 2. without nitrogen, non-nitrogenous, and 3. containing only mineral substances.
TISSUES AND MEMBRANES OF THE BODY
The simplest form of living matter is protoplasm. A living cell may be nothing more than a definite quantity of protoplasm (called cytoplasm or bioplasm) or it may be more complex, having a nucleus, when it is said to be nucleated, and it may have a nucleolus within the nucleus. A nucleated cell is capable of form- ing new cells by the division of its substance, the division always beginning in the nucleus.
Sometimes the cell is enveloped by a thin membrane called the cell wall.
FIG. i. — CONNECTIVE-TISSUE BUNDLES OF VARIOUS THICK- NESSES OF THE INTERMUSCULAR CONNECTIVE TISSUE OF MAN. X 240. — (Lewis and Stohr.}
Fat-cells
io a simple layer
FIG. 2. — ADIPOSE TISSUE. — (Lewis and Stdhr.)
Tissue. — Any collection of cells held together by intercellular substance is a tissue. The various tissues of the body are com- posed of cells (and intercellular substance) which are developed in special ways; for example:
Muscle tissue is composed largely of cells which are highly developed in the power to contract. Contractile tissues (list, p. 83).
CONNECTIVE TISSUE 5
Nerve tissue, of cells which are particularly sensitive to special kinds of stimulus.
Connective tissue is the fibrous soft framework of the entire body — the connecting structure by means of which all of its parts are held together. (Fig. i.)
Under this heading are included the following varieties: Fibrous tissue, a form of connective tissue containing slender
white fibers, closely packed together. Areolar tissue, containing the same kind of fiber cells loosely
woven into a network (often called cellular tissue). Adipose tissue, a variety of areolar tissue with cells containing fat. (Fig. 2.)
FIG. 3.— ELASTIC FIBERS. Xs6o. Very thick elastic fibers /, from ligamentum nuchaeof ox; b, connective-tissue bundles. — (Lewis and St'ohr.}
Elastic tissue, a form of connective tissue containing many elastic fibers, pale yellow in color. (Fig. 3.)
Osseous tissue, composed largely of cells having the power to utilize mineral substances of the blood in the formation of bone. (The intercellular substance is filled with min- eral matter.) (Figs. 7 and 8.)
Cartilage, a form of connective tissue with firm white elastic substance (intercellular substance) between its cells. Many cartilages are covered with a thin membrane called perichondrium, similar to the periosteum of bones (seepage 13).
ANATOMY AND PHYSIOLOGY
The principal varieties are:
Hyaline cartilage which has few cells and much intercellular sub- stance. (Fig. 4.) While fibro-cartilage which contains many white fibers, giving to it
additional strength.
Yellow or elastic fibro-cartilage which contains elastic fibers giving ad- ditional elasticity. Note. — Most bones are formed in cartilage. (See Ossification, page 14.)
Epithelial tissue forms the surface layers of the body both within and without. It is composed of layers of cells resting upon a base of the simplest possible substance, which holds the cells together and which bears vessels and nerves for their use. The form of epithelial cells varies with their location and use or func- tion. (Fig. 5.)
The epithelium of the exterior of the body is formed by flattened cells, arranged in few or many layers according to the degree of friction or pressure to which the skin of the part may be exposed. The covering thus formed varies therefore in thickness, from that of the delicate covering of the lips to the tough sole of the foot.
FIG. 4. — HYALINE CARTILAGE.— (Stohr.)
FIG. 5. — EPITHELIAL CELLS OF RABBIT, ISOLATED. Xs6o. i. Squamous cells (mucous membrane of mouth). 2. Columnar cells (corneal epithelium). 3. Columnar cells with cuticular border 5 (intestinal epithelium). 4. Ciliated cells; h, cilia (bronchial epithelium). — (Lewis and Stohr.}
The epithelium of interior surfaces is quite different. Its cells may be flattened, spherical, cuboid or columnar in shape and it is always moist. (All body surfaces are epithelial surfaces.)
In the lining of the air passages the epithelial cells are ciliated, that is, they bear tiny hair-like projections of their substance called cilia, which are in constant waving motion, always in the same direction, sometimes slow, sometimes rapid. (See p. 235.)
EPITHELIAL TISSUES 7
In the digestive organs the epithelial layer plays an important part in the formation of digestive fluids, and also in the absorption of digested food.
In the lining of closed cavities it assists in the formation of the fluids which they contain (example, the pleura}.
Included under this heading are (with brief notes of functions) : Gland tissue, where a layer of cells has the power to form a special substance from the blood. (Adenoid tissue resembles gland tissue.) (See p. 8.)
Mucous membranes, which line all interior surfaces to which air has access. Their special cells produce a clear thick fluid called mucus which keeps the surfaces moist.
Serous membranes, which line the closed cavities of the body. They are themselves closed sacs containing a clear thin fluid called serum which prevents the surfaces from rubbing together.
Synovial membranes, which line the interior of movable joints; they contain a thick fluid called synovia which like serum prevents friction.
The epithelial lining of the heart and blood-vessels, serous membranes, and lymph vessels, is called endothelium.
Clinical notes. — Mucous membranes are well supplied with blood-vessels and bleed freely when wounded, as seen in operations upon the nose and throat.
An accumulation of serum in the large serous membrane of the abdomen causes the condition called asciles (a variety of dropsy).
The processes of secretion and excretion are carried on through epithelial cells. (In specialized epithelial tissues.)
Secretion is the process of separating substances from the blood (generally in fluid form). Such substances if useful to the body are called secretions; if they are waste matters to be thrown off or eliminated, they are called excretions.
Secreting organs — mucous and serous membranes, all glands.
Excreting organs — lungs, kidneys, liver, cutaneous glands.
To summarize the functions of epithelial tissues — they are protective, secretory, excretory, absorptive.
An organic substance is a substance formed by living cells, whether they are single or arranged together in organs. Organic substances disappear in burning. Inorganic substances are mineral.
8 ANATOMY AND PHYSIOLOGY
An organ is any part of the body designed for a special func- tion or use; it may be composed of several kinds of tissue. An organ in the interior of the body (internal organ) is called a viscus (pleural, viscera). • Examples, heart, lungs.
A system is composed of a number of organs of similar structure. Examples, the muscular system, the nervous system.
An apparatus is composed of a number of organs of like or different structures, so arranged and associated that their action together will serve a special purpose. Example, the digestive apparatus.
Metabolism. — This term is used to express in one word the related processes of building up and breaking down which are constantly going on in all living cells.
The cell appropriates materials and combines them to perfect itself; in the exercise of its function it uses up some portion of its substance and so must be again built up, to be again pulled apart — in endless repetition.
Cell action in some tissues results principally in liberating heat and in body movement, as in muscles. In others it forms new compounds for other cells to use — for example, the liver cells form glycogen; the gastric glands secrete gastric juice, etc. Again, certain cells combine waste matters to get them into shape for other organs to excrete, for example, the formation of urea in the liver. In this way food materials are used for different purposes and worked over in different tissues until waste alone remains.
These examples (and many more which might be given) illustrate the metabolism which is constantly taking place in the body, and which will often be referred to in the text. (See pp. 166, 271.)
Structure of Glands: Since gland tissue is so important a factor of vital processes, a further description is warranted. It has already been stated that the epithelial layer is the active agent in the formation of new substances out of material derived from the blood. For the performance of this function, the epithelium is disposed in organs called glands.
The simplest gland is either a small tube, or a sac. The tubular gland may be divided into two or more portions forming a compound tubular gland. Tubular glands exist in the stomach, intestines, skin, etc.; in the skin they are coiled or convoluted at the extremity. (See Fig. 166.) A modification of the saccular gland is one which is composed of many small sacs arranged like
GLAND TISSUES 9
a bunch of grapes upon their stem — racemose gland. The salivary and pancreatic glands resemble this form.
The secretion of a true gland is discharged through a duct which opens upon some surface, either of the exterior or the in- terior of the body — for instance, the sweat glands open upon the skin, the gastric glands open upon the interior surface of the stomach, etc. All secretions which are discharged through ducts of glands are called external secretions. (For internal secretions see page 263.)
Lymphoid tissues are so called because they contain lymph cells supported in a network of retiform tissue. The faucial or
Excretory duct.
Secretory duct.
Intercalated duct.
End pieces.
FIG. 6 — DIAGRAM OF VARIOUS FORMS OF GLANDS. — (Lewis and Stohr.) The arrangement of ducts in D is that of the human submaxillary gland.
palatine tonsils are lymphoid in structure (page 133), as are also the lingual and thenaso-pharyngeal tonsils (page 135). (Ade- noids are hypertrophied naso-pharyngeal tonsils.)
Blood and lymph, although quite different in composition from others, still conform to the definition of a tissue and are called fluid tissues. They are each composed of an assemblage of small cells supported by intercellular substance; in this case, the inter- cellular substance is fluid instead of solid or semi-solid. In blood,
10 ANATOMY AND PHYSIOLOGY
the cells are blood corpuscles; in lymph, they are lymph corpuscles. The intercellular substances are blood plasma and lymph plasma. (Other fluids contain chemical substances only, in solution; cells appear in them incidentally.)
These tissues will be described more at length in Chapters X and XIII.
CHAPTER I
BONE TISSUE AND BONE CLASSIFICATION ARTICULATIONS
Bone tissue is conspicuously a hard tissue, due to the mineral or inorganic substances which it contains. They are mostly -phosphate and carbonate of lime and form two- thirds of the weigniroi an adult bone.
The remaining
one-third is composed of organic or animal substances, consisting of vessels, marrow, bone corpuscles, and gelatinous matter.
The mineral portion alone may be seen in a bone which has been burned (thus destroy- ing the organic substances). This leaves the bone still hard, but very brittle and easily crushed. The pale grayish color of a burned bone is noticeable, the result of the loss of all the marrow and blood .which it contained be- fore, and which gave it a pinkish tinge.
The organic portion of a bone may be shown by immersing it in dilute hydrochloric acid for a few days. The mineral salts will be thus dissolved out, leaving the flexible and elastic organic portion which still retains the shape of the bone. A long bone after the lime salts are removed in this way is said to be decalcified, and may be bent and twisted, or even tied in a knot.
By these experiments it is seen that the mineral matter gives hardness to a bone, while the animal matter gives flexibility and elasticity. The proportions of the two kinds of substance vary at different ages bones of a child are soft because they have not
This hardness is
FIG. 7. — VERTICAL Xhe SECTION OF A LONG BONE. — (Testut.}
12
ANATOMY AND PHYSIOLOGY
enough mineral matter to make them hard, while the bones of an aged person are brittle, because they no longer contain suffi- cient animal matter to keep them elastic.
The hardest part of any bone is at its surface; it is white in color like ivory, and is called compact bone tissue. The deeper part is porous, and is therefore called spongy tissue (also named cancellous tissue, because its appearance suggests lattice work). (See Fig. 7.)
Compact tissue is most abundant on the shafts of the long bones, which by their situation in the extremities are exposed to external violence, and therefore need especial strength for resist- ance. Since it is important that the bones be slender as well as strong, these two results are gained by packing the bone tissue as closely as possible.
Periosteum
Outer ground lamellae
Haversian canals
Haversian lamellae
Interstitial lamellae Inner ground lamellae
Marrow
FIG. 8. — FROM A CROSS-SECTION OF A METACARP OF MAN. X 50. The Haversian canals contain a little marrow (fat-cells). — (Lewis and Stohr.)
Cancellous tissue is more abundant in the parts of bones where extent of surface is desirable. For example, the enlarged ex- tremities of long bones are composed of cancellous tissue covered with a thin compact layer; thus they can give attachment to many tendons and ligaments, while the spongy character of the bone prevents excessive weight.
The marrow of bones is contained in the spaces of cancellous tissue (where it is thin and red) and in little canals running through the bone substance. Under the microscope may be seen small channels in the compact tissue called Haversian canals, which con- tain minute vessels and a little marrow. A large canal called the
PERIOSTEUM 13
medullary canal runs in the shaft of each long bone, containing firm yellow marrow and larger vessels.
Articular surface of bone is that portion which enters into the formation of a movable joint. It consists of a very compact tissue called the articular layer or articular lamella.
SURFACE MARKINGS OF BONE
Any inequality of the surface of a bone, whether it be an elevation or depression, or an opening, is called a "marking." The most prominent elevations often occur where the muscles are attached to the periosteum (owing partly to the calcification of these attachments); and the greatest enlargements of bones are at their extremities, where they form important joints.
A process is a decided projection; the larger processes are called tuberosities, small ones, tubercles.
A spine is usually a long or a sharp projection.
A crest is a prominent border; it may be rather broad.
A condyle is a rounded articular eminence.
A fossa is a depression or concavity.
A foramen is a hole through a bone.
PERIOSTEUM
There is no such thing as bare bone in the normal state; all bones are closely covered more or less completely with a strong fibrous membrane called periosteum. This membrane is essential to the life of the bone, rjecause many blood-vessels which nourish it lie in the periosteum until they become divided into minute branches which then enter the bone tissue.
The articular surface of bone is the only portion which is not covered with periosteum.
A bruise of sufficient violence will so injure the periosteum that it no longer serves for the purpose of nutrition, and that area of bone immediately underneath the injured membrane dies from want of food — becomes "dead bone" (the process is called necrosis}. The sensation imparted by a probe which touches dead bone is that of roughness, and is distinctly different from the feeling of sound bone with its smooth covering of periosteum.
14 ANATOMY AND PHYSIOLOGY
A similar membrane called endosteum lines the canal in the shaft of long bones. It bears the " nutrient" artery which, in the cavity of the shaft, divides into two branches running in the endosteum toward the two extremities.
The deep layers of the periosteum contain bone-forming cells. (See OSSIFICATION.)
CLASSIFICATION OF BONES ACCORDING TO SHAPE
According to differences of shape and arrangement of their tissue, bones are classified as long, short, fiat, and irregular. A long bone has always a shajf of compact tissue, and two enlarged extremities of cancellous tissue with a thin compact covering. The shaft is hol- low, containing yellow marrow, this cavity being called the medullary canal.
A short bone has neither shaft nor extremity; it is composed of cancellous tissue with a thin compact covering.
A flat bone is arranged in layers, two of compact tissue with one of spongy or cancellous tissue be- tween them.
An irregular bone conforms to no special defi- nition.
REMARKS. — In no part of anatomy is it more impor- tant that the student should learn the structures from the actual specimens than in the division called osteology. The bones are to be studied, not the book. It is supposed that with the bone in the hand the student will use the FIG. 9.— RIGHT book as a key, by means of which she will become ac- FEMUR ANTERIOR, quainted with the names of its parts and their uses. mE^ol E£pTiPHY- The habit of studying the human body itself rather than SES, AND SHAFT OR the description of it cannot be too soon nor too firmly
P'AP = YSIS- ~~ established. (Morns.)
OSSIFICATION
Ossification is the formation of bone from cartilage or mem- brane by the deposit of mineral substances, mostly salts of lime. Flat bones develop in membrane; others in cartilage.
OSSIFICATION 1 5
The deposit of mineral matter begins in small spots, forming centers of ossification which gradually increase in size until the entire bone is completed. Long bones have always three centers at first — one for the shaft, and one for each extremity — others appearing later, at different dates. (The extremities are named epiphyses, the shaft being the diaphysis) (see Fig. 9). The pTincipal parts of a bone are ossified separately, uniting with each other after all are developed. Ossification begins before birth in all bones except the coccyx, those of the carpus, and four in the tarsus; but many bones remain in two or more pieces during childhood and youth.
The periosteum of bone has an inner layer in which, also, the process of ossification goes on. Consequently, when it becomes necessary to remove a portion of bone, if it can be done without taking the periosteum away the bone will re-form. This has occurred many times, particularly in the case of the mandible.
The nutrition of bone. — Bones have a free blood supply from a network of small arteries in the periosteum. One special artery, larger than the others, enters the nutrient canal which leads to the interior of the shaft (this vessel is called the nutrient artery) .
THE HUMAN SKELETON
The skeleton of the body comprises 200 bones, as follows:
In the cranium 8
In the face 14
In the spinal column 24
In the pelvis 4
In the upper extremities 64
In the lower extremities 60
Ribs 24
Os hyoides i
Sternum. . i
200
These are joined together or articulated to form the hard, strong framework of the body — the natural skeleton.
In addition to these, there are four bones in each ear called ossicles, or "little bones," malleus, incus, stapes and so-called orbicular bone.
i6
ANATOMY AND PHYSIOLOGY
According to their location in the body they are classified as follows: Bones of the Head and Neck, Trunk, Extremities.
Head
Tibia Fibula
Tarsus
Metatarsus
Phalanges
FIG. 10. — BONY SKELETON. — (Holden.)
The bones of the head form the skull, which supports the face and the organs of special sense, and securely encloses the brain within its cavity. The bones of the neck connect the head with the trunk, and support the tongue and various other structures.
ARTICULATION OF BONES
The bones of the_trjmfc assist to form a cavity, divisible into three portions — the thorax, the abdomen, and the pelvis.
The bones of the four extremities contribute the solidity and strength which are necessary for their uses in various positions of the body.
ARTICULATIONS (ARTHROSES)
Articulations are formed when two or more bones are con- nected together, or when bone and cartilage are joined. They may be immovable or movable.
IMMOVABLE JOINTS (SYNARTHROSES)
In these the bones are held to- gether firmly by fibrous tissue, some- times by a thin layer of cartilage which becomes calcified in later life.
The best examples of immovable joints are found in the skull, where the flat bones are joined at their edges, forming sutures. (See page 20, Fig. 12.)
MOVABLE JOINTS (DIARTHROSES)
In these the bones are not closehi joined, but are loosely connected by ligaments which allow freedom of move- "ment between the surfaces. They are best studied in the extremities, where ™RES IN A MOVABLE JOINT.
. . (Diagrammatic.)
all varieties of movable joints are found.
. The essential structures in a movable joint are four in num- ber: Articular bone, articular cartilage, ligaments, synovial mem- brane with synovia.
The surfaces of bone which are to be connected together (articular surfaces) are made of a specially hard compact tissue called articular bone. It is smoother than other portions of the bone and easily recognized by the eye. It has no periosteum, but is covered by firm white hyaline cartilage — the articular cartilage.
1 1. — ILLUSTRATION ESSENTIAL STRUC-
1 8 ANATOMY AND PHYSIOLOGY
To hold the bones together, bands or cords of white fibrous tissue are provided, strong and flexible, but not elastic. They are called ligaments. The ligaments pass from one bone to the other on every side of the joint, like a capsule, completely enclosing it, and the capsule thus formed is lined by synomal membrane., so named because it secretes a fluid called s (the lubricating fluid or "joint-oil") which resembles in appear- ance the white of egg and prevents friction.
The synovial membrane not only lines the capsule but is attached to the margins of the articular cartilages.
Seven varieties of movement are allowed by these joints. They are:
Flexion, or bending.
Extension, or straightening.
Rotation, or rolling.
Circumduction, a free sweeping movement of the distal end of a limb in a circle.
Abduction, or moving away from a middle line.
Adduction, or moving toward a middle line.
Gliding (which explains itself).
Movable joints are classified according to the movements of
ividual joints, or by peculiarities of structure. The most important are the following:
Class. Motions. Example.
Hinge (ginglymus) Flexion and extension. . . . Elbow, Knee.
Ball and socket (Enar-
throsis) In all directions Shoulder, Hip.
Pivot (Trochoides) Rotation within a ring Head of Radius.
Rotation of ring around a
pivot A lias and axis.
Arthrodia Gliding Wrist joints.
There are other joints in which motion is so slight that they are not classed as movable, nor do they possess a cavity containing synovia. They have been well described by the term yielding. In these the bones are usually connected by fibro-cartilage discs. Examples are found in the joints of the pelvis (page 50) and in the spinal column (page 42). They are sometimes classified as slightly movable.
PECULIAR JOINTS 1 9
A variety of ball and socket joint is the condyloid, where the surfaces have an oval instead of a round outline; they allow all motions except rotation.
Another is the saddle-joint. Each surface has both a concavity and a convexity and each receives the other. (See page 63, Surgical Note No. 2.)
CHAPTER II BONES AND ARTICULATIONS OF THE SKULL
The skull includes the cranium and face.
BONES OF THE CRANIUM, 8
Frontal i Parietal 2
Occipital i Ethmoid i
Temporal 2 Sphenoid i
Frontal bone (os frontale) . — In the anterior part of the skull, shaped like a cockle-shell, and consisting of the frontal part, or forehead, the two orbital parts, and the nasal part. The frontal
GLABEL
ANTERIOR NASA SPINE
GNATHIO
BELION
MBDA
FIG. 12. — THE SKULL.— (Gerrish.)
part (squama frontalis) is flat in structure, and unites above with the parietal bones. This part is bounded below by a prominent border forming the two supraorbital margins. At the medial
FRONTAL AND OCCIPITAL BONES
21
third of each margin is a supra orbital notch (sometimes foramen) for the supraorbital nerve, artery, and vein. Just above the margins are the superciliary arches, which bear the eyebrows and mark the position of spaces in the frontal bone called the frontal sinuses. These sinuses begin to develop at the age of seven years and grow larger as time advances. They communicate with the nose, and contain air. The smooth space between the eyebrows is the glabella.
The nasal part is just below the glabella.
The orbital parts (or plates) of the frontal bone are so called because they are in the roof of the orbits, or eye-sockets; the space between these parts is occupied by the ethmoid bone and is called the ethmoid notch. Just underneath the lateral part of the superior margin of the orbit is a small fossa (the lacri- mal fossa), containing the'lacri- mal gland, where the tears are formed.
At birth the frontal bone is in halves — right and left — which become united in early life.
Occipital bone (os occipitale). — At the back of the skull and consisting of two portions: squamous (scale-shaped) and basal (Figs. 12 and 21).
The squamous portion (squama occipitalis) is flat in structure, triangular in shape, arid joined to the parietal bones. The most prominent point on the back of the skull is on this portion, and is called the occipital protuberance or inion.
TheJbasal portion bends forward, extending far enough toward the front to form the roof of the throat This portion presents a large opening called the foramen magnum (or great foramen), which transmits the spinal cord. At the sides of the foramen magnum are two smooth prominences, called the occipital condyles, which rest upon the first bone of the spinal column, whereby the nodding movement of the head is permitted.
FIG. 13. — FRONTAL BONE, SHOWING THAT IT ORIGINATES IN HALVES. —
(Morris.}
22 ANATOMY AND PHYSIOLOGY
The inner surface of this bone has broad grooves for the transverse sinuses (lateral sinuses); also one for the sagittal sinus (superior longitudinal sinus).
Temporal bones (ossa temporales). — Right and left; situated at the sides and base of the skull. (See Figs. 12 and 14.)
Each temporal bone consists of four portions — the squamous, the mastoid, the petrous, and the tympanic.
The squamous portion (squama temporalis) is flat, and presents the zygomatic process in the form of a ridge running forward in front of the ear to the cheek. Below the beginning of this process is the canal leading into the ear and called the external auditory meatus;
FiG; 14. — PARIETAL, TEMPORAL, AND SPHENOID BONES; POSTERIOR ASPECT. i, Body of sphenoid bone; 2, 2, greater wing and squamous portion of sphenoid bone; 3, 3, parietal bones; 4, 4, mastoid process of temporal bones. — (Sappey.) The occipital bone occupies the space outlined by these bones posteriorly.
just in front of that is the mandibular fossa, where the lower jaw- bone, or mandible, is joined to the temporal bone (Fig. 12).
The mastoid pprflon forms the prominence ^behind the ear and terminates in the mastoid process, which contains a number of grnan cavities, tne mastoid cells. They all communicate with the midoUe ear, and mastoid disease may therefore ioiiow' an iniection of the middle ear.
The inner surface of this portion shows the sigmoid groove for the transverse sinus.
PARIETAL AND ETHMOID BONES 23
The petrous portion is exceedingly hard, like stone, hence its name. A slender point of bone, called the styloid process, is seen on its lower surface; the carotid artery, on its way to the brain, passes through the carotid canal, which is in this portion.
The petrous bone contains the greater part of the ear; the internal auditory canal for the auditory nerve, or nerve of hear- ing, is on its posterior surface (seen within the skull).
The tympanic portion forms the greater part of the external auditory meatus, or canal.
Parietal bones (ossa parietales). — Right and left, situated at the top and sides of the head, and so named because they form the sides or walls of the skull. They are. flat in structure, and nearly square in shape; the four borders are called sagittal, squamous, frontal, and occipital (Figs. 12 and 14).
At the extremities of the borders are the angles — the frontal and occipital angles above, and the sphenoid and mastoid angles below. The most prominent point on the side of the skull is near the center of the parietal bone and is called the parietal eminence.
On the inner surface of this bone well-marked grooves are seen for the middle meningeal artery, and depressions for the convolutions of the brain.
Ethmoid bone (os ethmoidale). — Situated between the orbits and, therefore, m the upper part of the nose. (For illustration see pages 33, 34.)
It consists principally of two lateral portions formed of spongy bone, and containing the ethmoid cells or sinuses. These portions are called ethmoid labyrinths. They are in the walls of the nasal cavity and the cells open into it, therefore they contain air. The labyrinths are attached to the borders of the horizontal plate, which is situated in the roof of the nose and perforated for the passage of the nerves of smell.
The upper part of the nasal septum, which divides the nasal cavity into two parts, is formed by the vertical plate of the ethmoid, which hangs from the horizontal plate, and is, therefore, between the two labyrinths (Fig. 26).
Two of the turbinated bones (superior and middle) project from the medial surface of the labyrinths (Fig. 25). (For description of inferior turbinated bone see page 26.)
24 ANATOMY AND PHYSIOLOGY
Sphenoid bone (os sphenoidale) . — Immediately behind the ethmoid, to which it is joined. Its shape resembles a bat with the wings spread (Figs. 12 and 14). It consists of a body, wings, and two pterygoid processes. The body is joined to the ethmoid in front, and to the occipital behind. It is hollow, and its two cavities (called the sphenoid sinuses) communicate with the nose. The wings, two pairs — greater and lesser — extend outward from the body at about the level of the orbits. The optic foramen, for the optic nerve, is in the lesser wing.
The processes extend downward from the body, completing the back part of the sides of the nose.
Note. — The lateral extremities of the greater wings may be seen at the sides of the skull, between the frontal and temporal bones; the sphenoid is thus wedged in behind the face, between it and the other cranial bones. (The name sphenoid signifies wedge-tike.}
ARTICULATIONS OF THE CRANIUM
The joints of the cranium are called suturjgs. Most of them are formed by the interlocking of irregular edges of the bones held, firmly together by fibrous tissue between them. Sometimes the edges resemble saw-teeth in form, and then the suture is dentated or serrated. Sometimes the edges are smooth and overlap each other, and sometimes one fits between two others; but they are always immovable. (For illustration, see Fig. 12.)
The sutures which are most important for the nurse to recog- nize are those formed with three borders of the parietal bones. The two sagittal (or superior) borders, uniting with each other, form the sagittal suture; the frontal borders, uniting with the frontal bone, form the coronal suture, while the occipital borders, uniting with the occipital bone, form the lambdoid suture.
BONES OF THE FACE, 14
Nasal 2 Palate 2
Lacrimal 2 Inferior turbinated. . . 2
Zygomatic 2 Vomer i
Superior maxillary ... 2 Inferior maxillary, or
united, form the maxilla. mandible i
Nasal bones (os nasale, sing.). — Right and left. (Fig. 12.) They are flat in structure and form the bridge of the nose, being
THE MAXILLA
joined to each other in the median line of the face and to the frontal bone above.
Lacrimal bones (os lacrimale, sing.). — Right and left; small and thin, situated in the walls of the orbits, just under the ex- tremity of the supraorbital margin (Figs. 1 2 and 24). In this bone is the beginning of the canal in which the lacrimal duct runs con- veying the tears into the nose, thus preventing them from over- flowing the eyelids and running down the cheek.
Zygomatic bones (os zygomaticum, sing.). — Forming the promi- nences of the cheek (Fig. 12). They are especially noticeable in certain races, as the Chinese, for example, who have high " cheek bones."
Maxilla (or upper jaw-bone). — Situated in the front of the face, and composed of the two superior maxillary bones joined
Infraorbital foramen
Canine fossa
Nasal spine
Incisive fossa
Canine eminence
Articulates with zygo-
matic bone Posterior dental canals
Tuberosity
FIG. 15. — THE MAXILLA. — (Morris.}
together below the nostrils. It supports the cheeks, helps to form the nose and also the floor of the orbits. It consists of a body and several processes.
The body is hollow, the space being called the maxillary sinus or antrum of Highmore which opens into the side of the nasal cavity. In the lower border of the body the teeth are imbedded, the sockets of the large teeth being in the floor of the antrum, which explains how a diseased tooth may lead to antrum trouble.
The foramen on the surface of the body just below the orbit is called the infraorbital foramen. It is on a line with the supraorbital foramen of the frontal bone already mentioned.
26
ANATOMY AND PHYSIOLOGY
Processes. — The frontal process extends upward along the side of the nasal bone to join the frontal. The palate process is in the roof of the mouth, the bony part of the roof being called the hard palate. The alveolar process (or alveolus) is the thick border of bone in which the upper teeth are fixed. This process is very spongy and is sometimes broken in extracting a tooth. The zygomatic process joins the zygomatic bone to form the prominence of the cheek.
I Foramina and in- I cisive suture
Palate process
1 Palatine foramina J in a palate bone
FIG. 16. — THE HARD PALATE, OR ROOF OF THE MOUTH. — (Morris.}
Palate bones (os palatinum, sing.). — Right and left; shaped like the capital letter L, and placed behind the maxilla. The upright portion is in the side of the nose at the back; the horizontal portion lies in the floor of the nose, being at the same time in the roof of the mouth, and thus completing the hard palate (Fig. 2 1) .
Inferior turbinated bones (concha nasalis inferior, sing.). — Right and left; situated in the right and left walls of the nasal cavity below the superior and middle turbinated bones which belong to the ethmoid (Fig. 25). Each is composed of a thin plate of spongy tissue, having one edge rolled under like a shell (concha); they extend from front to back on the lateral wall of the cavity.
Clinical note. — Hypertrophy (or overgrowth) of the inferior turbinated bone is a frequent cause of obstruction to proper breathing.
Vomer. — A thin bone resembling a plowshare in shape, joined . above with the vertical plate of the ethmoid, and below with the
THE MANDIBLE
maxilla, thus forming the lower part of the septum of the nose. It is this part of the septum which is sometimes bent to one side, or "deflected," and it often presents a "spur" on one of its surfaces. (The vertical plate of the ethmoid and the vomer together form the bony septum, Fig. 26.)
Articulates with ethmoid
Groove for nerve
Articulates with hard palate
Ala
Posterior border
FIG. 17. — THE VOMER. — (Morris.}
Mandible (inferior maxillary, or lower jaw-bone, mandibula). — The only movable bone in the skull. It consists of a body having on either side a ramus (or branch) which is attached bv ligaments^ to the temporal bone.
The body is the lower portion, shaped much like a horseshoe with a thickened border (the alveolus] which bears the lower teeth.
FIG. 18. — THE MANDIBLE.
i, Body of bone; 2, ramus; 3, symphysis; 4, incisive fossa; 5, mental foramen; 7, depression for passage of facial artery; 8, angle of jaw; 10, coronoid process; n, condyle; 12, sigmoid notch; 13, alveolar border; a, incisors; b, bicuspids; c, canines; m, molars. — (Sappey.)
On each side is an opening called the mental foramen, which is in a line with the infraorbital and supraorbital foramina, already mentioned.
Each of these three openings transmits an important nerve, artery, and vein, bearing the same name as the foramen. See Surgical note, p. 308.
The ramus extends upward from the body, and ends in two processes, one of which is the condyle; it is this condyle which articulates with the temporal bone to form the temporo-maxillary joint.
28 ANATOMY AND PHYSIOLOGY
Clinical note. — Dislocation of this joint easily occurs if the mouth is opened too widely.
The angle of the jaw or mandible, is the posterior extremity of the lower border. The prominence of the angle differs in different people and at different ages.
ARTICULATIONS OF THE FACE
The bones of the face are all irregular, and many of them are very frail. They are fixed by sutures with one exception — that of the mandible which moves freely. (For description of a movable joint, see page 17.)
THE MANDIBULAR JOINT
The mandibular joint is a hinge-joint^ and the only movable joint in the skull. The action may be felt in front of the ear.
The bony surfaces are the condyle of the mandible and the mandibular fossa of the temporal bone. They are covered with
Capsule
FIG. 19. — MANDIBULAR JOINT. — (After Morris.)
cartilage and connected by ligaments forming a capsule, which is sufficiently loose to allow the condyle to glide freely in the fossa, back and forth or sidewise, as in opening and closing the mouth and masticating the food.
Surgical notes. — If the mouth be suddenly opened very widely, as in hearty laughing, dislocation easily results — that is,
THE CRANIUM 29
the condyles glide too far forward and slip in front of the fossa, making it impossible to close the mouth. To correct this con- dition (or " reduce the dislocation") press the jaw forcibly down- ward and backward with the thumbs placed upon the molar teeth. (First wrap the thumbs with a napkin to protect them, as the mouth will close suddenly.)
POINTS OF INTEREST IN CONNECTION WITH THE SKULL AS A WHOLE
THE CRANIUM
The cranium is a firm, strong case for the brain, composed largely of flat bones, the layers of these flat bones being called the
B REG MA
ANTERIOR NASA SPINE
PROSTHIO
GNATHI
BELION
MBDA
FIG. 20. — THE VERTEX AND SIDE OF THE SKULL. — (Gerrish.)
tables of the skull. The innermost table is very brittle and may be fractured by a blow which does not break the outer one, and owing to this brittleness it is called the vitreous, or glassy layer.
Observing the illustrations, or better, with the skull in the hand, the student may trace the frontal, two parietal, and occipital bones forming the vault of the skull, or the vertex; and at
30 ANATOMY AND PHYSIOLOGY
the sides the squamous and mastoid portions of the temporal bones and the tip of the great wing of the sphenoid.
Turning the skull upside down, observe the base. In the median line at the back is the basal part of the occipital bone, with the foramen magnum and the condyles on either side of it. In front of that are the body and processes of the sphenoid, and the roof of the mouth (or hard palate) bounded by the upper teeth. Tracing forward from the lateral part of the occipital
FIG. 21. — BASE OF SKULL.
i, 2, 3, Foramina and sutures in hard palate; 4, post-nasal spine; 5, nasal septum; 6, 7, 8, Q, 10, n, 12, pterygoid processes, and markings on sphenoid bone; 13, zygo- matic arch; 14, spheno-occipital suture; 15, 16, 17, 18, 19, 20, markings on tem- poral bone; 21, 21, condyles of occipital bone; 22, basal portion of occipital bone; 23, foramen magnum; 24, 25, crest and lines of occipital bone. — (Sappey.)
bone is the petrous portion of the temporal, with its sharp styloid process and round opening of the carotid canal; and in front of the temporal is the great wing of the sphenoid. The ethmoid may be seen through the posterior nares where the turbinated bones (better, shell-bones) are all visible.
Numerous openings or foramina pierce the base of the skull,
THE FACE
for vessels and nerves. The jugular foramen is just back of the carotid canal; through it the jugular vein leaves the skull to pass downward in the neck. The interior surfaces of all cranial bones show depressions for the convolutions of the brain.
THE FACE
(See Figs. 20, 24.)
Beginning with the forehead, note the two frontal eminences, and below these the superciliary arches with the glabella between them. Still lower, the supraorbital arches, with the nasal notch between them, to which the nasal bones are attached. Observe
FIG. 2 2.— SKULL OF NEW-BORN CHILD, SHOWING FRONTAL FONTANELLE. — (Edgar.}
FIG. 2 3. -^OCCIPITAL FONTANELLE. Both cuts show moulding of the head. — (Edgar.}
the lacrimal canal at the medial side of the orbit leading to the nasal cavity. Below the orbit, locate the infraorbital foramen on the surface of the maxilla and the mental foramen on the body of the mandible.
Remember that these three foramina transmit three very sensitive nerves, as follows: — The supraorbital nerve for the forehead, the infraorbital nerve for the cheek, and the mental nerve for the lower lip and chin. (Blood-vessels bearing the same names accompany these nerves.)
The prominences at the sides of the cheeks are made by the zygomatic bones. The openings of the nasal cavity are the
anterior nares, within which may be seen the septum, and the middle and inferior turbinated bones (shell bones).
32 ANATOMY AND PHYSIOLOGY
THE SKULL AT BIRTH
The bones are only partially developed, a considerable space between them being occupied by membrane (in some places, cartilage), and the frontal, bone is in two pieces.
Fontanelles. — The parietal and frontal bones are incomplete at the angles where their sutures meet, leaving a diamond-shaped space above the forehead where there is membrane only, and which is called the anterior or frontal fontanelle. The parietal and occipital bones also are lacking where their sutures meet, leaving a triangular soft spot called the posterior or occipital fontanelle, which is much smaller. These fontanelles are closed as the bones develop; the occipital in a few months, the frontal before the end of the second year.
Superciliary ridge
Glabella
FIG. 24. — THE ORBIT. — (After Morris.)
Obstetric note. — Owing to the fact that the bones are not firmly jointed, they can be made to overlap and thus adapt the shape of the Child's head to the passage which it must traverse during birth. This is called the moulding of the head (Figs. 22 and 23).
FOSS.E OF THE SKULL
The four large fossae of the exterior of the skull are the tem- poral, infratemporal, orbital, and nasal.
The temporal fossa (fossa temporalis). — The thinnest part
FOSS.E OF SKULL
33
of the skull (Fig. 20). It is bounded by the temporal ridge and the zygomatic arch, occupied by the temporal muscle, and covered by a strong membrane, called the temporal fascia, through which the motion of the muscle may be felt.
Infratemporal (or zygomatic) fossa. — At the side of the skull below the temporal fossa, from which it is separated by the zygo- matic arch (Fig. 20). It is covered by the ramus of the mandible, and occupied by two of the muscles of mastication, and also by a number of important arteries, veins, and nerves.
Concha superior
Sphenoidal sinus
Superior! meatus I
Concha media
Middle meatus
Palate bone Inferior meatus
Middle meatus
Concha inferior Probe emerg- ing from nasal canal
Ant. pala- tine canal
FIG. 25. — LATERAL WALL OF NASAL FOSSA OR CAVITY. — (Morris.}
Orbital fossa (or orbit). — containing the eye. It is shaped like a pyramid, the apex being at the back of the fossa. The large opening on the face is bounded by the margins of the orbit, having the frontal bone above, the maxilla below, and the zygo- matic bone on the lateral side.
The orbital plate of the frontal bone is in the roof of the orbit, and_the 3
34
ANATOMY AND PHYSIOLOGY
orbital plate of the maxilla in the floor. The lacrimal and ethmoid bones are in the medial wall; the sphenoid and zygomatic bones in the lateral wall.
The lacrimal canal begins in the lacrimal bone and runs down into the nose. The optic foramen, for the optic nerve, is at the apex of the fossa.
Nasal fossa. — Roof formed by nasal and ethmoid bones; floor by maxillary and palate bones; lateral watt by nasal, ethmoid,
FIG. 26.— THE BONY SEPTUM. Body of sphenoid immediately be- hind it. — (Morris.)
FIG. 27. — HYOID BONE, ANTERIOR
ASPECT.
i, i, Anterior or convex surface of body; 2, 2, greater cornua; 3, 3, junc- tion of greater cornua with body; 4, lesser cornua. — (Sappey.)
maxillary, and palate bones; septum by ethmoid and vomer (Fig. 26).
The openings on the face, or anterior nares, are bounded by the maxillary and nasal bones, and separated by the vomer. The openings into the throat or posterior nares are bounded by the sphenoid and palate bones, and separated by the vomer. Turbi- nated bones are seen on the lateral walls of the fossae.
Each nasal fossa communicates with four sinuses: the sphenoid, ethmoid, frontal, and maxillary. The sphenoid sinus opens into the upper and back part; the ethmoid, frontal, and maxillary (or antrum of Highmore) open at the side, lower down. The lacrimal canal also opens at the side near the floor.
The nasal fossae are lined with mucous membrane (the Schneiderian membrane) which is continued into all of the sinuses and the pharynx.
Clinical note. — Inflammation of this membrane may extend
THE TEETH 35
into any of the sinuses, causing sinusitis. If this occurs in the frontal region, a dull pain is felt over the eyes; if in the ethmoid region, a pain at the side of the nose and a change in the sound of the voice (nasal tone) are noted. The inflammation frequently extends into the antrum of Highmore.
The sense of smell resides in the upper part of the nose, the olfactory nerves coming down through the sieve-like plate of the ethmoid bone in the roof of the fossa.
BONES OF THE NECK
Hyoid (os hy aides). Seven cervical vertebrae.
The hyoid bone, or os hyoides. — Shaped like the letter U, situated in front of neck, about on a level with the chin, and sus- pended by ligaments and muscles from the styloid process of the temporal bone. The hyoid is not articulated to any other bone. It consists of a body and four cornua (or horns), and is designed to give attachment to the muscles of the tongue, and to others which connect it to the mandible above and sternum and clavicle below.
Seven cervical vertebrae. — The seven cervical vertebrae and their articulations will be described with the spinal column.
THE TEETH
A tooth is composed of dentine or tooth-bone, and consists briefly of a crown, a. neck, and a root.
Crown _____ a|_
. _,_ -Root
Cusp- Neck-
HI cav"y H
_ . 'Neck
i / ii mi
•Qngulum. "Crown
FIG. 28. — A MOLAR TOOTH IN SECTION AND A CANINE TOOTH. — (Morris.)
The crown is the exposed portion and is covered with hard white enamel. The root (connected with the crown by the neck) is concealed in the socket of the jaw and is covered with cement. The shape of the tooth varies from that of the flat incisor or cutting tooth, to the broad one for crushing and grinding.
36 ANATOMY AND PHYSIOLOGY
The incisors are the front teeth, f^nr in number in each jaw. They are used for biting and nittinfr the fond.
The cuspids (pointed) or canine teeth are situated next to the incisors; they also bite and masticate.
The bicuspids (two-pointed) or pre-molars, and the molars are for purposes of mastication.
The shapes of all are shown in the illustrations.
The teeth are hollow and contain tooth-pulp. This consists of a delicate meshwork of vessels and nerves entering at the point of the root, wrapped in connective tissue and filling the pulp cavity.
The upper teeth are imbedded in the alveolus of the maxilla, or upper jaw; the lower teeth in the alveolus of the mandible, or lower jaw.
Dentition : the Eruption of the Teeth
The teeth make their appearance in two sets, called temporary and permanent.
FIG. 29. — THE TEMPORARY TEETH. The rudiments of the permanent teeth are seen enclosed in the bones. — (Gorgas.)
The temporary teeth are twenty in number: their eruption or "cutting^ usually begins at about the seventh month and proceeds in following order:
Two lower central incisors at 7 months.
Two upper central incisors at 8 to 10 months.
Two upper lateral incisors at 9 to 1 2 months.
TEMPORARY TEETH
37
Two lower lateral incisors.* at 12 to 15 months.
Four first molars, i right, i left in each jaw.... at 12 to 15 months.
Four canines, i right, i left in each jaw at 16 to 22 months.
Four second molars, i right, i left in each jaw., at 24 to 30 months.
Twenty teeth in the temporary set at two and one-half years of age.
Thus, at one year of age the average child will have six teeth; at two years, sixteen; and the full number before it is three years old. Many exceptions occur, for example: the dentition of arti- ficially fed children may be delayed; and it is oftenest late in children affected by rachitis or " rickets."
The upper canines are known in the nursery as "eye-teeth"; the lower canines as "stomach teeth."
Clinical points.- — "Teething" or " cutting" of the temporary set occurs while the digestive tract is still in process of develop- ment and very easily disturbed; therefore special care should be
Incisors
Canine
Premolar
Molars
Wisdom tooth
Upper or max- illary teeth
P V
FIG. 30. — THE TEETH OF AN ADULT. — (Morris1 Anatomy.}
given to the child's diet both as to quality and quantity. Like- wise, the always delicate nervous system is at this time most easily irritated and excitement and fatigue should be avoided. These two points are equally important.
Meanwhile the permanent teeth are forming (Fig. 30). They gradually push toward the surface, cutting off the blood supply to the temporary teeth which become loose and fall out.
38 ANATOMY AND PHYSIOLOGY
The permanent teeth are thirty-two in number. At the age of six years the first permanent molar ("six-year molar") should appear; the others follow in order somewhat like the following:
Four first molars, i right, i left, in each jaw. ... at 6 years.
Eight incisors, 2 central, 2 lateral, in each jaw . . at 7 to 8 years.
Eight bicuspids, 2 right, 2 left, in each jaw at 8 to 10 years.
Four canines, i right, i left, in each jaw at 12 to 14 years.
Four second molars, i right, i left, in each jaw. . at 12 to 15 years.
Four third molars, i right, i left, in each jaw... . at 17 to 25 years. (The third molars are called "wisdom teeth.")
Thirty-two teeth in the permanent set at twenty-five years of age.
Clinical notes. — Caries, or decay of teeth, is due to bacterial action. This is favored by the accumulation of particles of food, the warmth and moisture of the mouth furnishing perfect conditions for the development of bacteria. Careful cleansing with brush or dental floss, or both, will prevent this and thus aid in preserving the teeth. Care is important in the use of brush or floss or toothpick, not only that the removal of injurious particles may be well done but in order to avoid wounding the mucous membrane which covers the gums, thus exposing them to bacterial invasion.
Recession of the Gums. — Any irritation (as by bacteria) of the gums may be followed by their recession, which exposes the dentine where it is not protected by enamel.
Sudden changes of temperature, as from hot to cold liquids, is injurious to the enamel. Acids, as ordinarily taken in food, have no special action upon the teeth, but sweets may do harm by their fermentation in a mouth where teeth are not kept clean.
The sockets of the teeth are lined wi'th periosteum (dental periosteum). It is reflected at the bottom of the socket to the root of the tooth and covers the cement; this portion is called the peri-cemental membrane (or periosteum).
Bacterial invasion of the gums may extend beneath the periosteum, caus- ing a chronic inflammation with suppuration, called pyorrhea alveolaris. Often the condition is painful, mastication is difficult and the teeth loosen and almost fall out of themselves.
CHAPTER III
BONES AKD ARTICULATIONS OF THE SPINAL COLUMN AND TRUNK
The bones of the spinal column are twenty-six in number. They are irregular and are arranged as follows, from above downward:
24 separate vertebrae
i sacrum, i coccyx.
7 cervical in the neck.
12 thoracic in the back.
5 lumbar in the loins.
in the pelvis.
A vertebra consists of a _body and an arch, joined, together to form a ring of Done with a space enclosed called the vertebraTforamen , which is occupied by the spinal cord. Trie bodies are composed of spongy bone, placed one above the other and held together by discs of fibrocartilage between them. In this way the solid and flexible portion of the spine is constructed.
The arch consists of two roots next to the body, antt two larkiriti which meet at the l)ack. ' There are seven processes on the arch of each vertebra — tour articular (two to form joints with the bone above, two for the bone below); two transverse (pro- j'ecting from the sides), and one spinou^ which projects backward. The row of spinous processes is felt by passing the finger down the back in the median line; that of the seventh vertebra is easily seen, and this bone is called the vertebra prominent.
39
FIG. 31. — VERTEBRAL COLUMN, LATERAL ASPECT.
1-7, Cervical vertebrae; 8-19, dorsal vertebras; 20- 24, lumbar vertebrae; A, A, spinous processes; B, B, articular facets of trans- verse processes of first ten dorsal vertebrae; C, auricu- lar surface of sacrum; D, D, foramina in transverse processes of cervical verte- brae— (Sappey.)
4O ANATOMY AND PHYSIOLOGY
POINTS or SPECIAL INTEREST
The cervical vertebrae present a foramen at the base of the transverse process, the transverse foramen, through which an artery runs to the brain, entering the skull through the foramen mag- num. (There are no transverse foramina in the dorsal or lumbar regions.)
Their spinous processes are cleft or bifid.
Transverse foramen Transverse process
Articular process
Lamina
Spinous process
Pedicle
FIG. 32. — CERVICAL VERTEBRA, SHOWING BIFID SPINOUS PROCESS. — (Morris.)
FIG. 33. — ATLAS, SUPERIOR SURFACE. i, Tubercle of anterior arch; 2, articular facet for odontoid process of axis; 3, posterior arch and posterior tubercle; 4, groove for vertebral artery and first cervical nerve; 5, transverse process1;- 6, transverse foramen; 7, superior articular process; 8, tubercle for attachment of transverse ligament. —(Sappey.)
FIG: 34. — Axis POSTERO-
SUPERIOR VIEW. i, Posterior surface of body; 2, odontoid proc- ess; 3» 3> superior articu- lar processes; 4, 4, inferior articular processes; 5,
5, transverse processes;
6, spinous process. —(Sappey.)
The first is called the atlas. It is a mere ring but has the usual number of processes (Fig. 33). The atlas is so named because it bears the weight of the skull (as Atlas, the fabled giant, bore the globe upon his shoulders).
The second is the axis. A strong process projects upward from its body forming a pivot for thlF ring-like atlas to revolve around. The pivot is called
THE SACRUM 4!
the tooth (or odontoid process) and is held in its place in the front part of the ring of the atlas (Fig. 33) by a strong ligament, which prevents it from pressing upon the spinal cord.
The thoracic vertebras are peculiar, in that their bodies present marks for the heads of ribs; also, they have long transverse and >inous processes.
FIG. 35. — A THORACIC VERTEBRA, SHOWING MARKS FOR HEAD OF RIB. — (Morris.}
Thejumbar vertebrae are the largest and strongest in 'the column, the bodies being conspicuously thicker than in the other regions, especially in the case of the fifth.
There are various other modifications of bones in the three regions — cervical, dorsal, and lumbar — which need not be mentioned here.
FIG. 36. — A LUMBAR VERTEBRA IN SECTION TO SHOW THE PRESSURE CURVES. —
(Morris.)
Sacrum. — An irregular bone formed by the consolidation of five incomplete vertebras, and joined to the last lumbar. Its genelal bliape lii that oi a curved wedge; it is placed with the base upward, and the concavity forward, forming the "hollow of the sacrum" A canal extends from the base to the apex, called the sacral canal, which is a continuation of the spinal (or neural) canal.
There are two sets of short canals, running from front to back through the sacrum. Seen from the front they present the an-
ANATOMY AND PHYSIOLOGY
terior sacral foramina; seen from the back, the posterior sacral foramina (both are for the passage of nerves) . The angle formed by the sacrum and the fifth lumbar vertebra projects sharply forward and is called the promontory.
Coccyx. — The terminal bone of the spinal column, and formed _of four very rudimentary vertebrae^ The base is Joined to the
sacrum ; the apex is directed downward and forward.^
FIG. 37. — SACRUM, ANTERIOR ASPECT. i, i, i, i, Bodies of sacral vertebrae with trans- verse lines of union; 2,2,2,2, anterior sacral foram- ina; 3, base; 4, auricular surface of lateral aspect; 5, its inferior portion; 6, articular surface of base; 7, notch for formation of last lumbar intervertebral foramen; 8, superior articular process of first sacral vertebra; 9, apex of sacrum; 10, cornu; n, notch for transmission of fifth sacral nerve. — (Sappcy.)
FIG. 38. — COCCYX, ANTE- RIOR ASPECT. i, Base; 2, 2, cornua; 3, second coccygeal vertebra;
4, third coccygeal vertebra;
5, fourth coccygeal vertebra;
6, fifth coccygeal vertebra. — (Sappey.)
THE ARTICULATIONS OF THE SPINAL COLUMN
The bodies of the vertebrae are connected by discs of fibro- cartilage which are placed between them. They serve not only lu luiiiiLil the vertebras but to give flexibility to the column, so that it may bend in any direction, and they also make it elastic. The bodies are further connected by fibrous bands on their anterior and posterior surfaces. (Slightly movable or yielding joints.)
The arches are connected by broad thin ligaments between the laminae, thus completing the spinal or neural canal, which conrtains the spinal cord. (These ligaments are an exception to the rule, in that they are elastic; they are called the ligamenta flava.) The articular processes are covered with cartilage and enclosed by capsules which are lined with synovial membrane, forming true movable joints. These are gliding joints. (Arthrodia.)
The only independent movements of the head are provided for
THE SPINAL COLUMN
43
hvthe arrangement of the atlas and axis. The nip-like arti'mlar processes of the atlas receive the condyles of the occipital hone fo, allow the nodding motion of the head. The occipital bone is held to the atlas by ligaments, and rotation of the atlas around the tooth of .the axis turns the head also, from side to side.
The ligamentum nuchse is a name given to a thick elastic band (not a true ligament) which stretches from the occipital protuberance to the seventh spinous process. It helps to sustain the weight of the head while bending forward, and is particularly well developed in the larger grazing animals.
From the seventh cervical down to the sacrum a supraspinous ligament is stretched, attached to all the spinous processes.
The movements of the spinal column are flexion, extension, lateral flexion, and rota- tion. Motion is freest in the cervical re- gion, and most restricted in the dorsal.
Clinical note. — The limited motion be- tween neighboring bones becomes a wide range in the column as a whole and may be increased by frequent and judicious ex- ercises.
THE SPINE AND THE SPINAL CURVES
The length of the spine is about 2 7 inches. The solid portion is a flexible and elastic column which bears the weight of the head and its delicate organs without giving them the full force of the jar caused by walking, running, etc. The flexibility of the column allows the whole body to move with freedom and grace, while the strength of the spine makes it suitable for the attachment of the extremities. The arches, connected by their ligaments, enclose the spinal or neural canal, which extends through the sacrum to
FIG. 39. — SPINE AND SPINAL CURVES. —{Sappey.}
44 ANATOMY AND PHYSIOLOGY
the base of the coccyx. Since the spinal canal contains the spinal cord there must be places of exit for the spinal nerves; these are found in the intervertebral foramina between the roots of the arches.
The spine has four curves: cervical, thoracic, lumbar, and sacral. These are normal curves.
The cervical and lumbar curves are concave posteriorly, as is seen to a slight degree in the back of the neck, and more plainly in the so-called " small of the back"; while the thoracic and sacral curves are concave anteriorly, to accommodate the organs in the thorax and pelvis.
These curves are caused by variations in the thickness of the bodies and cartilage discs. So-called "spinal curvature" is an excessive or abnormal curve. If anterior it is lordosis; if lateral, scoliosis; if posterior, kyphosis.
A lateral curve usually exists in the upper thoracic region, but this may be called accidental, as it is explained by the excessive use of one or the other arm.
THE TRUNK
INCLUDES THE THORAX, ABDOMEN AND PELVIS BONES OF THE THORAX
Sternum i
Ribs (costae) 24
Thoracic vertebrae 12
Sternum or breast-bone. — Placed in the front of the thorax. It is about 6 inches long, flat in shape and structure, and its two surfaces are called anterior and posterior. It has three divisions, the manubrium, the body, and the xiphoid appendix (Fig. 40).
The upper border of the sternum is notched — the sternal (or jugular) notch; the lateral borders give attachment from above downward to the clavicle and the cartilages of the first seven ribs. The xiphoid appendix is the lowest portion of the bone and gives attachment to some of the muscles of the abdomen. It remains cartilaginous until middle life.
Ribs (costtz). — Twelve in each side of the thorax, forming a series of movable elastic arches. They consist of a bony portion (the costal bone) and a flexible portion (the costal cartilage) . They are flat in structure, curved in shape.
THE RIBS
45
The posterior or vertebral extremity is the head, next to the head is the neck, and the remaining bony portion is the shaft. The inner surface of the shaft is marked by a groove at its lower border (the costal groove) in which the intercostal nerves and ves- sels run, being thus protected from external injury.
FIG. 40. — THE THORAX.
i, 2, Manubrium and body of sternum; 3, xiphoid appendix; 4, circumference of apex of thorax; 5, circumference of base; 6, first rib; 7, second rib; 8, 8, third, fourth, fifth, sixth, and seventh ribs; 9, eighth, ninth and tenth ribs, 10, eleventh and twelfth ribs; n, n, costal cartilages. — (Sappey.}
The first seven are called "true ribs," being connected in front with the sternum by their cartilages. The remaining five are "false ribs"; the eighth, ninth and tenth are connected in front, each to the one above; the eleventh and twelfth are not connected with anything in front, and are called "floating ribs."
Thoracic vertebrae. — Twelve in number; described with the bones of the spinal column.
46
ANATOMY AND PHYSIOLOGY
The seventh rib of the left side, inferior surface.
The costal groove is seen, to the borders of which the intercostal muscles are at- tached, thus completing a channel for in- tercostal vessels and nerve.
The tubercle is at the beginning of the shaft; the articular surface marked a is a part of the tubercle.
FIG. 41.— THE SEVENTH RIB. a, articular surface for transverse process; b, neck. — (Morris.)
THE THORAX 47
ARTICULATIONS OF THE THORAX
Sternum. — The three pieces (manubrium, body, and xiphoid appendix) are connected together by fibro-cartilages and anterior and posterior ligaments. After middle life they become united in one bone.
Ribs (costce). — The costal cartilages are connected in front to the sternum, or to each other, as already mentioned. The heads articulate with the bodies of two thoracic vertebrae. (Exceptions: the first, eleventh, and twelfth are each connected to one body.) Where the neck of the rib joins the shaft (marked by a tubercle) it rests against the tip of the transverse process of a vertebra behind
Head of rib
Articular surface of transverse process
Inter-articular liga- ment
FIG. 42. — HEADS OF RIBS ARTICULATING WITH TWO VERTEBRAE. — (After Morris.}
it, which thus forms a brace for it. All of these joints are enclosed by capsules and lined with synovial membrane, providing for the movements of the ribs in breathing, talking, etc. (Figs. 40, 42.)
Vertebrae.— Their joints have been described.
By the articulation of the ribs with the spine at the back and the sternum in front, the bony thorax is completed. It is shaped like a cone, flattened before and behind, and shortest in front (the sternum reaching only as low as the ninth dorsal vertebra). The intervals between the ribs are called the intercostal spaces.
The elasticity of the ribs and cartilages and their gliding joints give a yielding character to the thoracic walls to accommodate the movements of the lungs within.
48 ANATOMY AND PHYSIOLOGY
BONES OF THE ABDOMEN
The five lumbar vertebrae/ already described. BONES OF THE PELVIC GIRDLE
[ Hip bones 2
The bones are <j Sacrum i
I Coccyx i
Hip-bone (os coxce).< — Consisting of three parts which are entirely separate in the child. They are the os ilium, the os ischii, and the os pubis; they unite to form a cup-shaped cavity called the acetabulum, seen on the lateral surface of the bone. The acetabulum is the socket of the hip-joint (Fig. 43).
FIG. 43. — HIP-BONE, EXTERIOR. — (Morris.}
The os ilium is the highest part of the hip-bone and has a broad expanded portion called the wing (or ala). The medial surface of the wing is the iliac fossa, which is filled with the iliac muscle; the lateral surface is crossed by three curved lines (called the pos- terior gluteal, the anterior gluteal, and the inferior gluteal lines).
The superior border is called the crest. It can be easily felt, and the anterior extremity is known as the anterior superior iliac spine, more often called the spine of the ilium.
The os pubis is the anterior division of the hip-bone. It has
OS COX.E 49
a body and two branches, or rami. The body joins the ilium, the superior ramus has a short projection called the spine of the pubes, and the inferior ramus extends downward and backward to join the ischium, thus forming the upper part of the pubic arch. The two pubic bones join each other in the median line, forming the pubic symphysis (symphysis pubis).
Os ilium
Os pubis
Os ischii
Tuberosity
FIG. 44. — HIP-BONE, INTERIOR, BEFORE UNION OF PARTS. — (Morris.}
The os ischii (or the ischium), the lowest part of the hip-bone, has a sharp spine projecting backward, a tuberosity upon which the trunk rests in the sitting position, and a ramus which joins the pubic ramus to complete the pubic arch.
The ilium, ischium, and pubes united form the hip-bone (os coxae) . Two large notches are seen on the posterior border of the completed bone, separated by the spine of the ischium and called the sciatic notches. The upper one is the greater and the lower one is the lesser sciatic notch. In front of the acetabulum is the obturator foramen, the largest foramen in the skeleton. It is almost entirely closed by the obturator membrane, which is composed of white fibrous tissue.
THE ARTICULATIONS OF THE PELVIS
The two hip-bones unite with each other in front at the pubic symphysis, but the sacrum is between them in the back, having
4
5O ANATOMY AND PHYSIOLOGY
the coccyx attached to its apex, and thus the pelvic girdle is formed, usually called the pelvis (or basin). These joints have no cavity, and are only slightly movable, or yielding. There is a distinct disc of nbro-cartilage at the pubic symphysis.
Greater sacro- sciatic ligament
Lesser sacro-sci- atic ligament
Tendon of biceps muscle
FIG. 45. — GREATER AND LESSER SACRO-SCIATIC LIGAMENTS AND FORAMINA. — (Morris.)
Obstetric note. — The pubic symphysis and the sacro-iliac symphysis probably soften slightly during pregnancy. The sacro-coccygeal joint has limited motion until middle life advances, when it may become fixed.
Sacro-sciatic ligaments (Fig. 45). — Two strong bands are stretched between the sacrum and the ischium. They have no connection with any joints but are called the greater and the lesser sacro-sciatic ligaments. The greater (ligamentum sacro-tuberosum) extends from the borders of the sacrum and coccyx to the tuber osity of the ischium; the lesser (ligamentum sacro- spinosum) is placed immediately in front of it, extending from the sacrum and coccyx to the spine of the ischium. Thus are formed two foramina with the lesser ligament between them, the one above being called the greater sciatic foramen, and the one below the lesser sciatic foramen. (The sciatic nerves pass through the greater foramen.)
Poupart's ligament, or the inguinal ligament, may be felt like a tight cord stretched between the spine of the ilium and the spine of the pubis— "from spine to spine."
THE PELVIS 51
The Pelvis or Pelvic Girdle
False pelvis. — The upper part, between the wings of the ilia. It is broad and shallow.
True pelvis.^The lower part, bounded by the pubes in front, the ischia at the sides, and the sacrum and coccyx at the back. It is deeper and narrower.
The female pelvis has lighter bones, a wider pubic arch, and
FIG. 46— THE PELVIS.— (Morris.}
greater capacity than the male pelvis; the sacrum is less curved and the sacral promontory less projecting.
The limiting line or boundary between the false and the true pelvis is a curved line called the brim, and the space included is the inlet; the lower opening is the outlet. The inlet and the outlet are also known as the superior and inferior straits. The measurements or diameters of these straits in the female pelvis are as follows :
INLET (Edgar's Obstetrics)
Antero-posterior 1 1 cm.
(Symphysis to promontory.) Oblique \2\ cm.
(Ilio-pectineal joint to sacro-iliac joint.) Transverse 13! cm.
(Widest part of brim.)
5-
Am ore-posterior
(Sympbysis to tip of coccyx.) Transverse
(Between tuberosities.)
ii cm.
Fte. 47. — THE PELVIS. INLET,
>R STRAIT. — ($
i. Iliac fossa; 2, crest of ilium; 3, anterior-superior spine of ilium; 4, anterior- inferior spine of ilium; 5, ilio-pectineal joint; 6, 7, body and symphysis of pubes; S, acetabulum; o, tuber of isrhnim; 10, n, pubic arch: i:. spines of isclv. coccyx; 14, saooOiac joint; 15, is placed just above the promo: .
•-- :• •-- : ' • ' . -I".. .i:s
early in the second month.
The nucleus for the pubis appears about the end of the fourth month — -The nucleus for the ischium appears in the thud month
FIG. 48. — THE PELVIS of A FETUS AT BIRTH. TO SHOW THE THREE PORTI THE COKAL BOXES.— (Morris.)
THE DORSAL AXD VENTRAL CAVITIES OF THE BODY
By articulation of the bones of the head and trunk a framework is formed for two cavities, within which are situated the internal organs or viscera. (These delicate and important parts must be provided with surrounding structures which insure both their safety and efficiency.)
THE VENTRAL CAVITY 53
The cavities are called dorsal and ventral, or neural and visceral. Briefly speaking, they may be described as situated posteriorly and anteriorly to the solid part of the spinal column or bodies of the vertebrae.
The spinal canal is a part of the dorsal or neural cavity which extends into the interior of the skull, the bones of the cranium being modified vertebrae, and the cavity within them representing the uppermost or cranial part of the neural canal.
The dorsal or neural cavity contains the brain and spinal cord, well protected within firm, unyielding walls.
The mouth, neck, thorax, abdomen and pelvis inclose the ventral or visceral cavity, which is in front of the spinal column. The bony walls are very incomplete, especially in the abdomen. They are finished out by muscles; this arrangement allows the walls to be flexible and yielding in character, thus securing to the organs contained that freedom of movement which is necessary to their perfect action. The diaphragm (page 97) divides the ventral cavity into two portions, upper and lower; the pelvic floor (page no) completes the boundary below.
The ventral cavity contains the organs of respiration, circula- tion, digestion and reproduction; also the kidneys and bladder, which are organs of elimination.
Having studied the bones of the dorsal and ventral cavities or those of the head and trunk, we will proceed lin Chapter IV to those of the extremities.
CHAPTER IV
BONES AND ARTICULATIONS OF THE EXTREMITIES BONES OF THE UPPER EXTREMITY
The upper extremity, as the artist sees it, begins with the arm. The anatomist includes the shoulder as a part of the extremity. The bones are therefore as follows :
In the shoulder
j clavicula
In the forearm .
In the arm ........... humerus
radius
ulna
scaphoid
semilunar
cuneiform
pisiform
ist row.. .
In the wrist or carpus
2d row. .
8
In the hand.
trapezium
trapezoid
os magnum
unciform
J palm or metacarpus (metacarpal bones) 5 I fingers or digits (phalanges) 14
32
The names of -'carpal bones are given as follows in Spalteholz's Hand Atlas:
ist row — os naviculare manus. 2nd row — os multangulum majus. os lunatum. os multangulum minus.
os triquetrum. os capitatum.
os pisiforme. os hamatum.
Note. — The end of a bone which is nearest to the trunk is called the proximal extremity; the other end is the distal extremity. The same terms are applied to surfaces.
THE SHOULDER OR SHOULDER-GIRDLE
Scapula, or shoulder-blade (Fig. 49). — Placed at the upper part of the chest, behind the ribs (from the second to the eighth). It is flat and irregular in structure, and triangular in shape.
54
SCAPULA, CLAVICULA
55
The margins are called the superior, the vertebral, and the axillary; the angles, lateral, medial, and inferior. The inferior angle and vertebral border or margin usually project a little backward, sometimes very notably, making the so-called "winged scapula."
The anterior surface (costal surface) is called the subscapular fossa, and is filled with the subscapular muscle. The posterior or
dorsal surface is crossed by a rough ridge called the spine of the scapula which terminates in an important process, the acromion, overhanging the shoulder-joint.
Below and in front of the acromion is the coracoid process.
FIG. 49. — SCAPULA, POSTERO- FIG. 50. — CLAVICLE, INFERIOR ASPECT.
EXTERNAL ASPECT. ^ Longitudinal depression for insertion
i, Supraspinous fossa; 2, infra- of subclavius muscle; 2, rough impression
spinous fossa; 3, superior or coracoid for attachment of costoclavicular ligament;
border; 4, coracoid or suprascapular 3, 3, for attachment of coraco-clavicular
notch; 5, axillary or lateral border; ligaments; 4, 4, posterior border; 5, 5, an-
6, anterior angle and glenoid cavity; terior border; 6, facet for articulation with
7, inferior angle; 8, rough impression sternum; 7, facet for articulation with for long head of triceps; 9, medial or acromion. — (Sappey.}
spinal or vertebral border; 10, spine; n, smooth surface over which tra- pezius muscle glides; 12, acromion; 13, base of spine; 14, coracoid process. — (Sappey.}
The lateral angle presents a shallow depression called the glenoid cavity. This cavity forms the socket of the shoulder-joint.
Clavicula (or collar-bone, Fig. 50).— Long in shape, but having no medullary canal. It is curved like an italic letter / and placed horizontally across the front of the upper ribs. The medial ex- tremity articulates with the sternum and is therefore called the sternal extremity. The lateral extremity articulates with the acromion process of the scapula, and is called the acromial extremity.
Clinical note. — The weight and curves are increased by exercise, and both bones are usually more developed in men than in women.
ANATOMY AND PHYSIOLOGY
The clavicula is easily broken, especially in children, being fre- quently the seat of " green-stick " fracture. (See p. 77.)
The clavicula and scapula together form the shoulder-girdle, which is open at the back, but closed in front by the sternum placed be- tween the two claviculag.
THE ARM OR BRACHIUM
Humerus.- — Long in structure and shape, having a shaft with a medullary canal and two ex- w * * f tr entities.
The upper extremity (proximal extremity) includes the head, neck and tubercles.
The head articulates with the glenoid cavity of the scapula to form the shoulder-joint; the short, thick, anatomic neck joins the head to the shaft, and just below the neck are the greater and lesser tubercles for the attachment of muscles to abduct and rotate the arm. The lower extremity
FIG. 51.— LEFT curves slightly forward and presents two pro- HUMERUS, ANTE- RIOR ASPECT. jections at the sides called the medial and lateral
i, Shaft or body; epicondyles; the medial is the longer and conse-
2, head; 3, anatomic
neck; 4, greater tu- quently it is more frequently broken off. Be- bercle- 6* ^7*** ^ tween tne epicondyles are the articular surfaces markings for mus- for the elbow-joint, the trochlea for the ulna and
cles; 10, orifice for .
nutrient artery; n, the capttulum for the radius.
cWea^111!/ lateral The Shaft haS thre6 borders and three sur~
and medial epicon- faces like that of all long bones (on the fibula andmedial 'borfSS a fourth border and surface are described).
The anterior and medial borders run from the greater and lesser tubercles. In the upper part they are called the crests of the tubercles and the groove for the long tendon of the biceps muscle is between them (formerly called bicipital groove as the borders were called bicipital ridges).
The broad, shallow groove containing the radial nerve winds across the posterior surface.
Note. — The slender portion of the shaft just below the tubercles is called the surgical neck, because it is so often fractured.
ULNA, RADIUS
57
i"
FOREARM, OR ANTEBRACHIUM
* Ulna. — A long bone in structure and form, situated in the
medial side of the forearm (the ulnar side). The upper extremity presents two strongly marked processes — the olecranon, pro- jecting upward from the back and curving forward, and the coronoid, projecting forward from the front and curving upward. Thus these processes curve toward each other, and the cavity between them is the semilunar notch. It receives the trochlea of the humerus to form the elbow-joint. On the lateral side of the coronoid process is the radial notch, where the head of the radius lies.
The lower extremity is the head of the ulna, which lies in the ulnar notch of the ra- dius. There is a well-marked projection on this head called the styloid process.
The posterior border of the shaft is subcutaneous and may be traced down from the point of the elbow. The space between the radius and the ulna is called the interosseous space, and is occupied by an interos- seous membrane.
Radius.- — A long bone in structure and in form, situated on the lateral side of the forearm (the radial side).
The upper (or proximal) extremity is the head, which is depressed at the top to fit the capitulum of the humerus. Below the head is the neck, and below that, in front, is the tuberosity of the radius for the attachment of the biceps muscle of the arm. The lower (or distal) extremity of the radius is broad and thick, and is the largest bone in the formation of the wrist-joint.
On its lateral aspect is the styloid process. Run- ning across the upper half of its anterior surface is the oblique line, which is a part of the anterior border.
Special notes. — The head of the humerus is proximal and articulates with
FIG. 52.— LEFT ULNA AND RADIUS, ANTERIOR SUR- FACES.— (Sappey.)
i, Shaft or body of ulna; 2, semilunar notch; 3, radial notch occupied by radial head; 4, olec- ranon; 5,* coronoid process; 6, orifice for nutrient artery;
7, interosseous bor- ders with interos- seous space between;
8, head of ulna; 9, styloid process of ulna; 10, shaft or body of radius; n, 12, head and neck of radius; 13, tu- berosity of radius; 14, marking for mus- cle; 15, 16, lower ex- tremity and styloid process.
58 ANATOMY AND PHYSIOLOGY
the glenoid cavity of the scapula. The head of the radius is proximal and articulates with the humerus. The head of the ulna is distal.
The upper end of the ulna is its largest part, and an important bone in the elbow-joint. The lower end of the radius is the largest part, and important in the wrist-joint. Observe that in the long bones of the upper extremity the nutrient foramina are in the shafts and are directed toward the elbow-joint. They transmit nutrient arteries to nourish the bones.
CARPUS
The carpal bones (ossa carpi) are eight in numfygr. and are typical "slwrt tones. They are arranged in two slightly curved
rows — the first and second — with the con- vexity of the curves turned upward to- ward the radius, the first row articulating with it.
FIRST Row
Navicular (os namculare). — On the radial side of the wrist, named from its shape which resembles a boat, and marked by a tubercle.
FIG — BONES OF Semilunar (os lunatu m) . — Well named CARPUS, DORSAL SURFACE, from its half-moon shape.
Cuneiform (os triquetrum). — Very slightly resembling a wedge.
Pisiform (os pisiforme). — Resembling the half of a split pea, and placed in front of the cuneiform.
SECOND Row
Trapezium (os multangulum majus). — On the radial side, marked by a ridge.
Trapezoid (os multangulum minus). — The smallest of the carpal bones.
Os magnum (os capitatum).- — The largest, having head, neck, and body.
Unciform (os hamatum). — Named for its unciform or hook- shaped process.
When the carpus is seen from the front, four prominent points are to be noted, namely — the tubercle of the navicular and ridge
BONES OF THE HAND
59
of the trapezium, on the radial side; the pisiform bone and hook of the unciform on the ulnar side. These mark the boundaries of a deep groove where the long tendons of the ringers glide.
THE METACARPUS OR PALM
The five metacarpal bones (ossa metacarpalia) are long in shape but have no medullary canal. Each has a base, a shaft, and a head, the head being distal. The bases are articulated with the second row of the carpus, the heads with the first row of the phalanges. The first corresponds to the thumb, the second to the index finger, the third to the middle finger, the fourth to the ring finger, and the fifth to the little finger.
The spaces between them are inter- osseous spaces and are occupied by inter- osseous muscles.
Note. — The third metacarpal bone (of the middle finger) is the longest, and its head is the most prominent when the hand is clenched, as in making a "fist."
FIG. 54. — RIGHT HAND, PAL- MAR OR VOLAR SURFACE.
PHALANGES
These are the bones of the fingers and for thumb (digits). A finger has three, first, Carpus; 11-11, phalanges; 12, second and third; the thumb has two, first phalanges; 14, 15, ist and 2d and second. They are long in shape, but \sappey ^ of thumb-- without a medullary canal. Each has a
base, a shaft, and a head, the head being distal. The first row of phalanges includes those which are next to the metacarpal bones. The terminal phalanges (those of the third row) have each a horse-shoe-shaped border on the anterior surface for the support of the sensitive finger tip; because these bear the nails they are called the ungual phalanges.1
1 This description of the metacarpal bones and phalanges follows that of standard text-books. It would seem, however, more in accordance with the facts to con- sider the palm as composed of four metacarpal bones — one for each finger — and to give to the thumb three phalanges, since the bone commonly called the first metacarpal (or the metacarpal of the thumb) resembles those of the first row of the phalanges in both form and development.
6o
ANATOMY AND PHYSIOLOGY
Resume. — With the limb in the anatomic position, observe the groove for the biceps muscles on the front of the humerus, beginning between the greater and lesser tubercles. In the forearm, note that the ulna is the bone of the elbow-joint, while the radius makes the wrist-joint; that their shafts are parallel and the palm is turned forward, and the carpus curved to help in forming the hollow of the hand (or the "cup of Diogenes"), and that the thumb is on the radial side, and free.
ARTICULATIONS OF THE UPPER EXTREMITY
Sterno-clavicular, a gliding joint (arthrodia) . — This is the one joint by which the upper extremity articulates with the trunk.
Articular surfaces; on the upper angle of the manubrium and the sternal end of the damcula. Anterior and posterior ligaments
Inter-articu- lar ligament
Sterno-cos- tal joint
FIG. 55. — STERNO-CLAVICULAR JOINT. — (Morris.)
The inter-articular cartilage is shown in the joint of the right side; capsules shown
on the left side.
connect the bones, forming a capsule. (The joint is divided by a disc of fibro-cartilage into two cavities and there are two synovial membranes.)
Motions. — Gliding, by which the shoulder moves upward, downward, backward and forward.
Ligaments not connected with the joint but useful in preventing dislocation: — Thecosto-davicular, holding the clavicle to the first rib, and the conoid and trapezoid connecting it with the coracoid process of the scapula. (See Fig. 56.)
Acromio-clavicular. — A small gliding joint between the acromion process of the scapula and the acromial end of the damcula. It is enclosed by a capsule.
Shoulder-joint. — A ball-and-socket joint (enarthrosis) . Artie-
SHOULDER- AND ELBOW-JOINTS
6l
ular surfaces: the head of the humerus and the glenoid fossa of the scapula. The fossa is deepened by a rim of fibro-cartilage called the glenoid margin. The capsule is attached to the scapula around the margin of the glenoid fossa, and to the humerus around the anatomic neck. It is so loose that the head of the humerus will
Conoid ligament
Superior transverse
scapular ligament
Trapezoid ligament
Coraco-acromial ligament
Short head of biceps Subscapular tendon
Capsule of shoulder
Long tendon of biceps
FIG. 56. — ANTERIOR VIEW OF SHOULDER, SHOWING ALSO CORACO-CLAVICULAR AND CORACO-ACROMIAL LIGAMENTS. — (Morris.')
fall an inch away from the glenoid fossa by its own weight, if the surrounding muscles be removed; it contains a synovial mem- brane which covers the glenoid margin and folds like a sheath around the long tendon of the biceps muscle (Fig. 56).
Motions. — In every possible direction, as flexion, extension, ab- duction, adduction, rotation, and circumduction, with greater free- dom than any other joint of the body, because the socket is so shallow and the capsule is so loose.
Elbow- joint. — A hinge-joint (ginglymus) (Fig. 57).
Articular surfaces: the trochlea of the humerus in the semilunar notch of the ulna; the capitulum of the humerus in the depressed head of the radius.
62 ANATOMY AND PHYSIOLOGY
The ligaments — anterior, posterior, medial, and lateral — to- gether compose a large capsule. (They are attached to the humerus above the olecranon fossa at the back, and above the coro- noid and radial fossae in front.) The synomal membrane is extensive.
Annular ligament Tendon of biceps
Oblique ligament
Upper edge of inter- osseous membrane
Flo. 57. — MEDIAL VIEW OF THE ELBOW- JOINT .—(Morris.}
Motions. — The elbow-joint proper is capable of flexion and extension only, like all hinge-joints.
The radius and ulna are connected together at their extremities, making rolling joints (see p. 18); their shafts give attachment to an interosseous membrane of white fibrous tissue which almost fills the space between the bones.
Wrist- joint. — Between the forearm and the carpus, having a variety of gliding motions, but used principally as a hinge-joint. Articular surfaces: Above — the lower end of the radius and the triangular cartilage (or articular disc) ; below — the first row of carpal bones (not including the pisiform) . The ligaments — anterior pos- terior, medial, and lateral — enclose the joint like a capsule.
Motions. — Flexion, extension, and slight lateral bending (or from side to side) making abduction and adduction. (If the hand is bent far backward or over-extended, this is dorsal flexion.)
CARPAL, METACARPAL AND PHALANGEAL JOINTS
Surgical note. — The anterior ligament of the wrist-joint is remarkably strong and seldom torn; the lower end of the radius breaks instead, under sudden great force, as in Colics' fracture.
Carpal. — Eight bones arranged in two rows, bound firmly to- gether by short ligaments. Motions — Gliding only.
Metacarpal. — Five bones, articulated by their bases to the carpus, and by their heads to the digits. Head of first, belong- ing to thumb, is free; heads of others connected together by a transverse band. Motions — Slight gliding, except in case of the
Ulnar radio-ulnar ligament .
Ulnar collateral lig- ament of wrist Flexor carpi ulnaris
Radial collateral
ligament of wrist Volar radio carpal
ligament
Tendon of fl e x o r carpi radialis
Capsular ligament of first carpo-met- acarpal joint
FIG. 58.— ANTERIOR VIEW OF WRIST. — (Morris.}
thumb, which may be flexed or bent upon the palm; extended or straightened; abducted from hand; adducted toward hand.
Surgical note. — In the normal hand, a dislocation of the thumb is most difficult of reduction, because the metacarpal head and the base of the first phalanx are interlocked in such a manner as to form what is called a joint by reciprocal reception, or " saddle joint."
Phalangeal.- — Three bones in each finger, two in the thumb. Anterior, posterior, and lateral ligaments. Motions — Flexion and extension.
64
ANATOMY AND PHYSIOLOGY
Note. — In the completed hand, the fingers and the thumb can be moved from side to side, independently; that is, they can be spread apart (abduction) and drawn together' (adduction) (p. 18).
SUPINATION AND PRONATION
These are terms applied to certain movements of the ex- tremities. They are best seen in the forearm where they change the position of the hand.
The head of the radius rests in the radial notch of the ulna, held there by a circular band called the ring ligament (orbicular), and it can be rolled forward or backward, within the ring (a form of pivot joint) . Of course, the shaft moves at the same time, the lower end turning forward or backward around the head of the ulna, and the wrist and hand must accompany it. When the radius and the ulna are placed in the anatomic position, their shafts are parallel and the hand lies upon its back; this is supina- tipn. If the radius rolls forward, the shafts become crossed, and the hand lies upon its face; this is pronation.
Surgical notes. — Supination and pronation are very important movements. If they are prevented the hand loses much of its usefulness, therefore fractures of the shafts should not be set in the position of pronation, lest adhesions form between the crossed shafts, preventing supination.
BONES OF THE LOWER EXTREMITY
In the Thigh Femur i
In the Leg | Tibia
1 Fibula
Talus
Calcaneus
] Cuboid
In the Tarsus j Navicular bone. .
ist cuneiform... .
2d cuneiform. . .
3d cuneiform. . .
Metatarsus ....... Metatarsal bones 5
Toes or Digits Phalanges 14
Patella . , A sesamoid bone. i
ist row. . .
2d row. .
THE FEMUR
As given by Spalteholtz the names of tarsal bones are: —
Talus Calcaneus (os calcis)
ist row
Os cuboideum Os naviculare pedis Os cuneiforme I Os cuneiforme II Os cuneiforme III
2d row
THE THIGH
Femur. — The largest bone in the body.
Its upper extremity presents a nearly spherical head joined by a neck to the shaft, and resting in the acetabulum. At the
FIG. 59. — THE FEMUR, LEFT POS- TERIOR ASPECT.
i, i, Linea aspera; 2, 2, 3, divisions of linea aspera; 4, 4, divisions of linea aspera; 5, 6, head, and mark for liga- mentum teres; 7, neck; 8, 9, trochanter major; 10, trochanter minor; n, 12, lat- eral and medial condyles; 13, intercon- dyloid notch; 14, 15, lateral andjnedial epicondyles. — (Sappey.)
5
FIG
60. — LEFT TIBIA AND FIBULA, ANTERIOR ASPECT.
i, Shaft or body of tibia; 2, 3, me- dial and lateral condyles; 4, spine or intercondyloid eminence; 5, tubercle of tibia; 6, crest or shin; 7, 8, lower ex- tremity, and medial malleolus; 9, shaft or body of fibula; 10, upper extremity or head of fibula; n, lower extremity and lateral malleolus. — (Sappey.)
66 ANATOMY AND PHYSIOLOGY
junction of the neck and shaft are the two trochanters — the trochanter major on the lateral side, and the Irochanter minor on the medial and posterior side. The lower extremity presents two condyles projecting downward, the medial and the lateral. The medial is slightly longer, the lateral slightly broader of the two; the deep notch between them is called the intercondyloid notch or fossa. There is a projection from the side of each condyle called the medial and the lateral epicondyle.
The shaft has a prominent posterior border called the linea aspera. This divides lower down into two lines running to the condyles and enclosing a smooth triangular space called the pop- liteal space, or plane of the femur. The other borders are not plainly seen.
THE LEG (FiG. 60)
Tibia. — A long bone in the medial side of the leg. Its jipper extremity is the head, which presents two condyles, medial and • la lu crtT^having shallow depressions on the top to bear the condyles of the femur. Between these depressions is the inter- condyloid eminence, or spine of the tibia. The tuberosity of the tibia is a large elevation in front, just below the head. The lower extremity has a projection downward from its medial surface called the medial malleolus, which helps to form the ankle-joint.
The shaft has a prominent anterior border called the crest or shin, which is plainly felt under the skin. This border and the medial surface are both called subcutaneous because no muscles cover them.
Fibula. — A long bone, in the lateral side of the leg, slender and easily broken. Its upper extremity is the head, which has a short styloid process pointing upward. The lower extremity is the lateral malleolus, which helps to form the ankle-joint.
Note. — The space between the tibia and fibula is called the interosseous space, and is occupied by interosseous membrane.
The lower extremities of these two bones form the prominences at the side of the ankle known as the ankle-bones; they are the medial and the lateral malleoli, which, being subcutaneous, are especially exposed to blows.
Special notes.— Observe that the heads of al] three bones are proximal; that the fibula does not form any part of the knee-joint; that the nutrient foramina all run from the knee.
TALUS CALCANEUS
67
THE TARSUS (Fio. 61)
There are seven tarsal bones arranged in two irregular rows to form the arches of the foot, or instep.
FIRST Row
Talus (astragalus). — On the tibial side. Has a head, a neck, and a body; the body is received between the two malleoli to form the ankle-joint, and the head is turned forward toward the toes. It rests upon the calcaneus.
Calcaneus
Talus
Scaphoid, or navicular
First cuneiform
Tarsus
Metatarsus
Phalanges
FIG. 6 1. — BONES OF LEFT FOOT. — (Morris.}
Calcaneus (os calcis) or bone of the heel.* — The largest tarsal bone, it is under the talus (astragalus), and bears the weight of the entire body in the erect position. The tuber osity of the cal- caneus projects backward beyond the ankle, and gives attachment
68
ANATOMY AND PHYSIOLOGY
to the largest tendon in the body, the tendon of Achilles (tendo A chillis).
SECOND Row
Navicular (os namculare) . — On the tibial side, in front of the talus, articulating with its head.
Cuneiform bones (or wedge-shaped bones).- — In front of the navicular. They are three in number, first, second, and third.
Cuboid (os cuboideum). — It lies in front of the calcaneus.
THE METATARSUS
The five metatarsal bones in the foot resemble the metacarpal bones of the hand in their general characteristics, with some special developments; the inter osseous spaces between them are occupied by interosseous muscles.
PHALANGES
Fourteen in number, as in the hand, and arranged in a similar manner — two for the great toe, and three for each of the other toes.
A. B.
FIG. 62. LEFT PATELLA. FIG. 63.
A, ANTERIOR SURFACE; B, POSTERIOR SURFACE. — (Morris.)
Note.- — The great toe is in the medial border of the foot.
PATELLA
The patella is the largest sesamoid bone. It is triangular in shape, placed in front of the knee-joint, and held to the tuber- osity of the tibia by a strong band about three inches long — the
HIP-JOINT
69
Tendon of biceps muscle
Capsule
FIG. 64. — HIP-JOINT. — (Morris.)
Capsule Glenoid rim
Ca psule
FIG. 65. — LIGAMENTUM TERES. — (Morris.")
7O ANATOMY AND PHYSIOLOGY
so-called ligament of the patella. Its location while the body is erect is in front of the condyles of the femur, but in the sitting position it is in front of the lower ends of the condyles, and in kneeling it is beneath them.
ARTICULATIONS OF THE LOWER EXTREMITY
Hip-joint (ball-and-socket joint) (Enarthrosis) . Articular sur- faces: head of the femur, and the acetabulum deepened by the glenoid rim of the acetabulum (a rim of nbro-cartilage). The bones are directly connected by the ligamentum teres (or round ligament) within the joint, which is attached by one extremity near the middle of the head, and by the other to the bottom of the acetabulum (Fig. 65).
A capsule encloses the joint. It is strengthened by special bands of fibers extending to surrounding bones — one, the ilio- femoral from the ilium to the great trochanter, resembles an in- verted letter Y, and was formerly called the Y-ligament (also the ligament of Bigelow). The synovial membrane not only lines the capsule but invests the ligamentum teres.
Motions. — Free motion in every direction, like that of the shoulder.
Knee-joint (hinge or ginglymus joint) (Fig. 66). — Articular surfaces: the condyles of the femur, the head of the tibia, and the posterior surface of the patella. The two surfaces on the top of the tibia are shallow, but their depth is increased by semilunar fibro-cartilages attached around the borders, thus forming shallow cups for the condyles.
The femur and tibia are directly connected by two ligaments within the joint, which cross each other and are therefore called the crucial ligaments. (One passes from the front of the spine to the lateral condyle, the other passes from behind the spine to the medial condyle.) The patella lies in front of the condyles, being imbedded in a thick tendinous band about three inches long which continues to the tuberosity of the tibia. (This band is really the tendon of insertion for some thigh muscles, and is improperly called the ligament of the patella.} It serves as the anterior liga- ment of the joint but is at the same time the quadriceps extensor tendon, sometimes called the patellar tendon. There are distinct
KNEE-JOINT 71
medial and lateral ligaments, and some strong oblique bands at the back; and all are connected by a capsule which encloses the joint cavity.
The synovial membrane is very extensive (Fig. 66) ; it covers the crucial ligaments and semilunar cartilages.
Motions. — Flexion, extension, and very limited rotation of the leg.
Note. — The patella cannot be drawn upward under any circumstances. When the knee is flexed, it lies against the lower ends of the condyles, and in kneeling the condyles rest upon it. The elasticity of the great muscles to
Extension of synovial sac of knee upon femur
Tendon of quadriceps extensor, forming fibrous capsule of joint
Patella
- Pre-patellar bursa Condyle of femur (inner) Ligamentum mucosum
Fatty tissue
Synovial membrane re- flected off crucial liga- ments
Cut end of anterior cru- cial ligament Posterior crucial liga- ment
Fatty tissue between ligamentum patellae and synovial sac
Bursa beneath ligamentum patellae
Tibia
FIG. 66. — INTERIOR OF KNEE-JOINT. — (Morris.)
which the patellar tendon belongs, allows very free motion and at the same time keeps the patella always in place close to the condyles.
Bursse. — There are several small cavities called bursse, the use of which is to prevent friction in the tissue outside the knee-joint. They usually com- municate with the joint. The largest one is, however, subcutaneous, being in front of the patella between it and the skin. (Fig. 66 and page 82.)
72 ANATOMY AND PHYSIOLOGY
Surgical note. — This prepatellar burs a is subject to frequent pressure and easily becomes inflamed and enlarged, making the so-called "housemaid's knee."
Ankle-joint (Hinge- j oin t) . — Articular surfaces on the medial and lateral malleoli and the body of the talus. They are connected by anterior, posterior, and lateral ligaments.
The medial is often called the deltoid ligament, from its shape A like the Greek letter delta, and the lateral ligament is in three distinct bands, the anterior ', middle, and posterior.
Motions. — Flexion, extension, and slight abduction and adduc-
\\
Medial or deltoid ligament
Plantar ligaments
FIG. 67. — LIGAMENTS OF THE ANKLE-JOINT AND PLANTAR REGION. — (Morris.}
tion; also lifting the medial border, or eversion, and lifting the lateral border, or inversion.
Notes.— The trans-verse ligament is a special band behind the talus, connect- ing the two malleoli, to prevent backward dislocation of the foot in jumping, running, etc.
There is no motion of the lower extremity which corresponds to supination in the upper, the whole extremity being in the permanently pronated position, which brings the great toe toward the median line of the body, or on the medial border of the foot. (The thumb is on the lateral border of the hand.)
Tarsal joints. — An inter osseous ligament connects the talus to the calcaneus; it is the strongest one in the body. Short fibrous bands
ARCHES OF THE FOOT
73
connect the various tarsal bones to each other to complete the instep, and there is one elastic ligament upon which the head of the talus rests. It assists to prevent excessive jarring as the foot strikes the ground. (This is the only ligament containing elastic tissue in the extremities.)
Metatarsal. — Like the metacarpal, except that the heads are all joined together by a transverse band; the great toe is not free.
Phalangeal. — Like those of the hand.
Arches of the foot. — The principal arch is from the heel to the ball of the foot; a second one, the transverse, is equally im-
Tendo Achillia Talus Vessels and nerve
Scaphoid First cuneiform
First metatarsal
Calcaneus
Muscles of plartar region
FIG. 68. — MEDIAL BORDER OF RIGHT FOOT, SHOWING BONES IN POSITION. — (Morris.}
portant. The arteries and nerves in the sole of the foot are pro- tected from pressure by these arches, which are preserved not only by the ligaments and the shape of the bones, but by the tendons of certain muscles.
Practical points. — In walking the weight is transmitted principally through the talus, the navicular, and three cuneiform bones to the three medial toes, giving the "springy" step to the well-arched foot. In standing, it falls more upon the calcaneus, and is distributed through the cuboid to the two lateral toes as well.
RESUME
Comparing the joints in the upper and lower extremities, note that both the shoulder and hip are ball-and-socket joints; that
74 ANATOMY AND PHYSIOLOGY
the elbow and knee are hinge-joints, as are also the wrist and ankle; but whereas in the wrist extension is limited, in the ankle it is so free as to bend the top of the foot almost against the leg, becoming dorsal flexion, and is actually called flexion of the ankle- joint, the term extension being used to signify the act of straighten- ing the foot in a line with the leg.
The back of the hand and the top of the foot are both called the dorsum; the face of the hand is the palm or volar surface, and the sole of the foot is the plantar surface. The thumb is free; the great toe is bound with the others.
The following table of articular nerves is inserted in this place for convenient reference, when, in the care of painful joint affec- tions, the nurse may be interested to know the names of the par- ticular nerves involved.
NERVE SUPPLY TO THE PRINCIPAL JOINTS
Temporo-mandibular. . . Fifth cranial or trifacial.
Shoulder Suprascapular, subscapular, axillary.
Elbow Musculo-cutaneous (principally).
Wrist and hand Ulnar, median, deep branch of radial.
Joints of spinal column. Spinal nerves.
Hip Femoral, obturators, sciatic.
Knee Femoral, obturator, tibial, peroneal.
Ankle and foot Deep branch of peroneal, two plantar nerves.
CHAPTER V COMPLETION, REPAIR AND FUNCTIONS OF BONES
NOTES CONCERNING THE COMPLETION OF LONG BONES
In the humerus, radius, and ulna, the nutrient canals lead toward the elbow and the bones are completed here at an earlier date than at the wrist or shoulder. In the femur, tibia, and fibula, the nutrient canals lead away from the knee; and the bones are completed first at the hip and the ankle.
Surgical notes. — The time of union of the extremities and shafts of long bones is important from a surgical viewpoint. Thus, in the ends of bones at the elbow-joint the extremities join the shafts at about the seventeenth or eighteenth year; therefore, injuries near the elbow-joint before this age may cause a separation of the parts, called an epiphyseal fracture. The upper end of the humerus and lower ends of the radius and ulna unite with their shafts at about the twentieth year; therefore, in the case of an injury of the shoulder or wrist before this age the same possibility is borne in mind.
In the lower extremity certain differences are noted, since the nutrient arteries run differently. The bones are completed first at the upper end of the thigh, at about nineteen, and at the lower end of the leg at about eighteen or twenty years, while the knee is completed last, at between twenty and twenty-five.
, It is important for the nurse to understand something of the nature of the baby's skeleton. The general condition at certain periods of life is also of interest.
BRIEF SURVEY OF THE SKELETON AT DIFFERENT AGES
At birth:—
Head. Skull-bones have unossified borders and angles, there- fore, the membrane is soft at the fontanelles; the base of the skull is largely in cartilage, and the bones are slightly movable.
Face-bones small and very incomplete.
Spinal column Bodies of vertebrae partially ossified, with much carti- lage between them. Arches, each in two separate pieces or halves.
Pelvic-girdle Hip-bones (ossa coxae) in three pieces, well separated
by cartilage.
Sacrum partially ossified. Coccyx not at all ossified. Ribs Shafts only are bony.
75
76 ANATOMY AND PHYSIOLOGY
Sternum Presents a number of small centers, imbedded in cartil-
lage.
Upper extremity Shoulder-girdle ossified at acromial end of clavicula and
in body of scapula; other parts are cartilage. Long bones — Shafts partially ossified. Carpus — all bones entirely cartilaginous.
Lower extremity .. . Long bones — Shafts partially ossified; at the knee the
ends of the femur and the tibia have begun to ossify.
Tarsus — three bones (talus, calcaneus, and cuboideum)
have begun to ossify. The metacarpal, metatarsal and phalangeal bones have
thin lines of osseous tissue before birth. At age of 20 years Head
Hands
All completed.
Feet
Long bones All completed except tibia and fibula whose upper ends
are not yet united with the shafts.
Ribs 1
0, \ Are in two pieces each.
Sternum j
Shoulder-girdle Clavicula, sternal end still separate. Scapula soft at
borders and processes. Pelvic-girdle Hip-bones (ossa coxae) completed. Sacrum and coccyx
still in two or more pieces.
Spinal column All parts ossified.
At age of 25 years:. The skeleton is practically completed. The bones are
strong, and the proper proportions of animal and
mineral matter are preserved during adult life. The coccyx may unite with the sacrum in middle life,
thus modifying one of the diameters of the pelvic
outlet. In old age: There is no more growth. The supply of animal
matter decreases, and the bones become brittle so
that they may be easily broken.
POINTS OF PRACTICAL INTEREST CONCERNING THE BONES IN
INFANCY
First, the baby's bones are soft, and are still largely composed of cartilage. Second, since the process of ossification is going on continually, the proper shape of the cartilage should be preserved in order that the shape of the future bone may be normal. In infancy the skull bones are movable as well as soft, and the shape of the baby's head may be altered by pressure. Witness the Flathead Indians, who bind a board across the top of the infant's skull.
REPAIR OF BONE 77
The spine and the vertebral extremities of the ribs are com- posed largely of cartilage; it is therefore evident that not only should a young baby's back be supported, but the child should rest in a horizontal position, the spine being so soft that it cannot easily be held upright, even if the little muscles were strong enough to do this without fatigue.
The pelvis and hip. — During the first year or two both the sacrum and the coccyx are still in separate pieces, while the centers in the three portions of the hip-bones are well separated by cartil- age, leaving the acetabulum unossified; the head of the femur is also soft. Consequently, a thought only is needed to explain why the clothing about a baby's hips should leave them free from pressure.
Note.- — An advantage is derived from the softness of the skeleton during childhood, as the many jarrings and tumbles incident to the child's experience are far less injurious to the jelly- like frame than they would be to a harder one.
Green-stick fracture.- — Up to the age of four years the bones are sufficiently soft to bend rather than break, as an older bone would do under similar circumstances. Usually some of the fibers do break, but not the whole bone; this is called a green- stick fracture, because the bone behaves like a bough of green wood when forcibly bent.
Rachitis or rickets. — In this disease ossification is delayed, and the bones are more soft and yielding than usual until com- pletely ossified. The extremities grow larger and the shafts are often bent. When the mineral salts are finally deposited the bone is permanently misshapen. Rachitis is a disease of malnutrition from deficiency of mineral food.
Spina bifida. — In the formation of the vertebrae, the comple- tion of the arches and spinous processes occurs latest in the lower lumbar and upper sacral region. Sometimes it is not perfect, and the spinal canal is then left open. This condition is known as spina bifida and the membranes and fluid of the spinal cord pro- trude, forming a tumor upon the child's back. Spina bifida occurs rarely in other regions.
REPAIR OF BONE
When a bone is broken nature repairs it in her own way. First, more blood flows to the part; then a certain amount of
78 ANATOMY AND PHYSIOLOGY
animal matter like cartilage, appears about the fracture, forming a callus. This is soon hardened by deposit of mineral matter and the callus becomes bone, but the mark of fracture and repair will always remain. The callus will form and unite the ends of bone even if they are not well matched, but in this case deformity will result. If the callus does not harden the union is fibrous.
Surgical note. — " Setting" a fractured bone consists in placing the ends in proper position, or "apposition." This, nature can- not do, because the muscles above and below are pulling them out of place, therefore the skill of the surgeon is required for its accomplishment.
Practical point. — The nursing care of a fracture is directed to the end of keeping the bone supported in position, and as far as may be, perfectly quiet until the callus is hardened, so that the least possible deformity will remain. To accomplish this the nurse must not only have a knowledge of anatomy, but must exercise skill and judgment to an unusual degree.
PHYSIOLOGY OF BONE AND THE SKELETON
At first thought it would appear that not much could be said concerning the physiology of bone tissue, which is a finished prod- uct, the changes which it undergoes being directed solely to its own preservation. The ability of bone to repair injuries by utiliz- ing material from the blood is, however, a physiologic process; and the membranes which cover bony surfaces (periosteum outside, endosteum within medullary canals) have a well-defined function in the formation of bone tissues, already referred to. One of the most important functions of the body, namely: — pro- viding an origin for cells (or corpuscles) of the blood, belongs to the marrow of bones. Cancellous bone contains in its spaces thin red marrow (the "red bone marrow" of clinic use) in which red cells have their origin, while the medullary canals of long bones contain a firmer fatty marrow where many of the white cells of the blood have their beginning.
Taking a broad view, we find many points of interest in the bones and the skeleton which they comprise, some of which have already been touched upon. It is their mechanical physiology which is conspicuous and of great importance — they afford attach- ment to muscles; they enclose cavities; they sustain pressure.
THE ARTICULATED SKELETON 79
Their usefulness is due to their physical characteristics — for in- stance, the hardness of bones enables the framework which they com- pose to support the soft parts of the body, and in certain localities enables them to protect internal organs. An important example is the neural canal with its contents- — the brain and spinal cord.
Again, it is this same quality of hardness which enables the skel- eton to bear direct pressure and the body weight. Osseous tissue in certain bones — notably the femur and the os coxae — is especially arranged in lines of pressure for this purpose; namely, that super- imposed weight may be borne with the least strain upon the bone.
The relation between the shapes of bones and the arrangement of their two tissues has a direct bearing upon their usefulness and the convenience with which it is exercised. Examples are seen in the long bones- — their (comparatively) large extremities enter into the formation of joints; they also give attachment to many muscles which move the joints. Here, extent of surface is needed and cancellous bone is used with but a thin covering of compact, thus securing the necessary surface without undue weight. Their shafts give attachment to fewer muscles, but their position in the extremity exposes them to violence (applied transversely) and calls for endurance of strain. Hence, for these two reasons — first, that extent of surface is unnecessary; and second, that strength and endurance are demanded- — the compact tissue is appropriate. It also secures a convenient slenderness of bone where the bulk of muscle tissue is greatest.
By far the greatest variety of functions is seen in the articu- lated skeleton, whereby the movements necessary to the well-being of the individual are made possible by the character of the joints.
The movements of the trunk are limited, but sufficient for the needs of the organs which it contains; while those of the extremities are many and free. They may resist external force; they may themselves overcome opposing forces. They may be used as weapons of offense or defense. Facilities for transporting the body from place to place, or locomotion, are provided by the articulated bones of the lower extremities; and the power of the upper ex- tremities to perform a thousand necessary acts would not exist without a similar framework. These points have been mentioned already, and will be dwelt upon later in connection with the study of the muscular system.
CHAPTER VI
THE* CONNECTIVE TISSUE FRAMEWORK AND THE SKELETAL MUSCLE SYSTEM
THE FASCLE OF THE BODY AND MUSCLES OF THE HEAD AND TRUNK
Although present in every part of the body, the connective tissue is so conspicuously associated with the muscle system that a few facts of interest concerning this universal tissue are here reviewed, before commencing the study of the muscles.
For muscles it is a veritable -framework, as will be seen. In fibrous form it is conspicuous on their surfaces as sheaths, or as separating one from another; and in tendons. As delicate areolar tissue it invades them, bearing tiny vessels and nerves and forming tissue-spaces.
This it does in all organs — wrapping them, supporting their cells, and invading them to convey vessels and nerves. It fills in spaces between organs, and accompanies large vessels to and from them. It connects organs to each other; and everywhere it forms a network of tissue-spaces containing nutritive fluid obtained from the blood-vessels for the cells of the body.
If one could imagine that everything in the human body ex- cept connective tissue could be destroyed, the remaining portion would bear the same relation to the body that had been, as a skeleton leaf bears to a fresh green one.
THE FASCIAE OF THE BODY
The word fascia is applied to the connective tissue which surrounds various organs or lines cavities. Fascia is found in every part of the body, and we shall study here two varieties, which are associated with the muscles and skin. They are called the deep and the superficial fascia.
The deep fascia. — This is a firm layer of connective tissue with but small spaces between its fibers, therefore it is dense and
80
DEEP FASCIA
8l
tough. It is white and smooth, and seldom contains any fat. The deep fascia covers the muscles and binds them down, and also separates them into groups, thus forming intermus- cular septa. (Many muscle fibers arise from intermuscular septa.)
Special points. — The inguinal ligament (Fig. 79) is a band of the deep fascia between the spine of the ilium and the tubercle of the pubes. It feels like a cord from one bone to the other.
The fascia lata (broad fascia) is that
Great or long saph-
FIG. 69.— DEEP FASCIA OF THIGH FIG. 70.— SHOWING OVAL FOSSA. (Partial). 6, 7, 8, 10, 14, indicate por- The superficial fascia has been dissected tions of fascia lata. — (Sappey.) away, leaving cutaneous veins lying
upon deep fascia.
portion of the deep fascia which covers the muscles of the thigh; it is thicker and stronger than any other fascia of the body. It is attached to the hip- bones above and the leg-bones below. A portion which is especially tense 6
82 ANATOMY AND PHYSIOLOGY
and strong may be felt on the lateral side of the thigh, above the tuberosity of the femur, like a tight band attached to the tibia; it is called the ilio-tibial band. See page 113, tensor fascice latce.
The oval fossa or saphenous opening (Fig 70) in the fascia lata is an inch and a half below the medial portion of the inguinal ligament. It allows the long saphena vein to pass through to the femoral vein.
The lumbar fascia is not a part of the general deep fascia of the body, but belongs to the transversus muscle described on p. 96. It is attached behind to the lumbar vertebra, above to the last two ribs, and below to the crest of the ilium.
The superficial fascia covers the deep fascia. It lies immedi- ately beneath the skin in its whole extent and consists of loose- meshed connective tissue, arranged somewhat in layers, and con- taining the subcutaneous fat. It also imbeds the superficial or cutaneous arteries, veins, and nerves between its layers. In places where the fascia is thin, as on the back of the hand, the veins are easily seen. This fascia is closely connected with the skin, and they glide together over the deeper structures.
A bursa is a sac in the fascia which contains smooth fluid resembling synovia. Burs<z are found where much pressure or friction occurs between different structures. They act like water- cushions, thus saving the tissues from bruising or rubbing. The largest subcutaneous bursa is in the superficial fascia in front of the patella. It is called the prepatellar bursa (Fig. 66).
Surgical note. — When the prepatellar bursa becomes in- flamed and enlarged, it forms "housemaid's knee."
Sometimes bursae are placed underneath tendons or between muscles, and these deep ones may communicate with joints. There is a large one between the gluteus maximus and the tuber- osity of the ischium, and another between the same muscle and the great trochanter.
Note. — The transversalis and pelvic fasciae are found within the abdomen and the pelvis, respectively (see pages 100 and in).
MUSCLES, THEIR IMPORTANCE
The growth of bone and fashioning of joints has but prepared the way for more important ends to be accomplished.
The head and trunk protect and support the vital organs, but
MUSCLE STRUCTURE 83
the food and the air upon which their life depends come only through the aid of those constant workers, the muscles. All motion of any sort in the body, whether conscious or unconscious, is due to their action. If the motion is voluntary it is due to muscles which are controlled by the will, or voluntary muscles. Muscles which cannot be controlled by the will are involuntary; they are found in the internal organs of the body, or the viscera, and in the coats of vessels. All other muscles are voluntary, and since they are attached to bones they are called skeletal muscles.
Contractile tissues: — Muscular and ciliated epithelial cells. Striped skeletal muscle. Striped cardiac muscle. Unstriped visceral muscle.
STRUCTURE OF MUSCLES
Muscles consist chiefly of collections of red fibers, each fiber composed of little bundles of muscle-cells. All of these are wfappecTin connective tissue, bound together and enclosed in a sheath.
Transition zone.
FIG. 71.— LONGITUDINAL SECTION OF A PART OF A MUSCLE FIBER FROM. A HUMAN INTERNAL INTERCOSTAL MUSCLE, SHOWING ITS TRANSITION TO TENDON. X 750. — (Lewis and Stohr.)
Examining a muscle with care, we can strip off the sheath of connective tissue (epi-mysium) , and we shall find that it sends layers down into the muscle to form septa or partitions (peri-mysium) enclosing the bundles (or fasciculi) of which the muscle is made up.
With the aid of the microscope the fiber cells which compose the bundles are revealed, surrounded by still more delicate connective tissue (endo- mysium) .
Also, under the microscope the fiber cells of voluntary muscle tissue ap- pear striped, consequently voluntary muscle is said to be striped or striated. Involuntary fiber cells are plain — involuntary muscle is unstriped or non- striated. This sort of muscle is found in internal organs, whose work must go on continually without our conscious supervision.
84
ANATOMY AND PHYSIOLOGY
Exception. — The heart : which acts whether we will or not, although its muscle is striated.
In most cases the connective tissue is prolonged beyond the muscle into a white cord or band called a tendon, if the muscle is long and thick; or into a broad thin layer called an aponeurosis if the muscle is flat; and by these tendons and aponeuroses the
FIG. 72. — SHOWING EXTREMITIES OF MUSCLES. 2, Tendon. 5, Aponeuro- sis.— (Sappey.)
FIG. 73. — INTERCOSTAL MUSCLES. — (Morris.}
muscles are attached to bones and other organs. Sometimes the red fibers are attached directly to the parts which they move, but in by far the greater number the tendons are conspicuous (Fg. 72). Muscles are described as consisting of a body and two ex- tremities; the body or belly being the red contracting part which swells in action, while tendons (which are possessed by most of the
INTERCOSTAL MUSCLES 85
muscles) are simply strong white fibrous bands having no power to contract and no elasticity. This is equally true of the aponeuroses.
The attachments of the extremities are spoken of as the origin and the insertion. The extremity which is stationary while the other end moves, is the origin; the end which moves with the organ attached to it, is the insertion. The insertion is always pulled toward the origin when the muscle contracts.
The names of muscles are not applied according to a uniform plan, being some- times chosen because of location, as the intercostals (between ribs) or the epicranial muscle (upon the head), etc; or, the shape may determine the name, as orbicularis oris (ring muscle of the mouth) ; but of tenest the name signifies the action of the muscle. The original names are in the Latin tongue but the English translation is often used. The full Latin name includes the word musculus (muscle) which is quite com- monly omitted for the sake of brevity.
SKELETAL MUSCLES OF THE TRUNK1
Intercostal muscles. — In two sets, the
internal and the external, which occupy the intercostal spaces. The fibers run
obliquely from rib to rib, the internal
, , . FIG. 74.— THE FIGURES
fibers running upward and forward, the REFER TO THE SPINAL GROUP
external fibers running downward «»* *£^(&I ^5
forward. (Fig. 73.)
Action. — They move the ribs up and down in breathing and the various acts associated with it.
PRINCIPAL MUSCLES OF THE BACK
In the skeleton a broa^i groove exists on either side of the spinous processes, which is filled in its whole extent with many vertical muscles of different lengths, the use of which 'is to hold
1 Many skeletal muscles have their origin partly from the deep fascia covering them. The bony origins alone are given here, as a rule and only the more important of those.
86 ANATOMY AND PHYSIOLOGY
the spine in the erect position; also they assist to move it in various directions.
The erector spinae is the name given to this large group, which is bound down in its place by a thin layer of fibrous tissue called the vertebral aponeurosis. This muscle group extends from the skull to the lower part of the sacrum (Fig. 74) .
The action is most easily seen in the lumbar and dorsal regions? where it is not deeply covered with other muscles.
Nerves. — Posterior spinal.
The latissimus dorsi (broadest of the back, Fig. 75). — This muscle covers most of the erector spinae and a great portion of the back of the trunk.
Origin. — The spinous processes, from the sixth thoracic down to the end of the column. (Also the crest of the ilium and a few fibers from the inferior angle of the scapula.) Insertion. — The crest of the lesser tubercle of the humerus.
Action. — Principally to pull the arm backward and keep the scapula or shoulder-blade close to the chest; brought prominently into use in rowing a boat or when the body is suspended by the hands and an effort is made to draw it up.
Nerves. — Posterior spinal and long subscapular.
MUSCLES OF THE BACK OF THE NECK
These muscles move the head and neck. Only the most important are here described.
The splenius. — This muscle is in two portions, the splenius of the head (capitis) and the splenius of the neck (cervicis) .
Origin. — The spinous processes of the last cervical and first six thoracic vertebrae. Insertion. — Partly upon occipital and mastoid bones (splenius capitis) and partly .upon the transverse processes of the upper vertebrae (splenius cervicis).
Action. — The muscle of one side alone will rotate the head, twisting the neck. The muscles of both sides acting together simply pull the head back- ward or extend it and the neck.
Nerves. — Posterior cervical.
•
The trapezius covers the other muscles of the back of the neck, and also the upper portion of the latissimus dorsi. It is one of the largest muscles in the body (Fig. 75). T^e two muscles, right and left together make a large diamond-shaped sheet.
TRAPEZITS 87
Origin. — The occipital bone, the ligamentum nuchae, and the spinous processes of the thoracic vertebras. Insertion. — The spine of the scapula and lateral third of the clavicula.
Action. — With the shoulders stationary the trapezius acts upon the head to pull it backward or sideways. With the head station-
FIG. 75. — SUPERFICIAL AND MIDDLK MUSCULAR LAYERS o? JHE POSTERIOR ASPECT
OF THE TRUNK.— (Sappcy.)
i, Trapezius; 2, latissimus dorsi; 3, aponeurosis; 4, 5, 6, 8, 19, 20, different por- tions of latissimus dorsi; 9-12, deep muscles; 13, sterno-mastoid; 14, splenius; 15, elevator of scapula; 16, infraspinatus; 17, teres minor; 7, 18, teres major; 21, portion of anterior serratus; 22, 23, abdominal muscles; 24, 25, gluteus maximus; 26-30, deep muscles; 31, deltoid; 32, triceps.
ary it can elevate the shoulder-girdle and the whole upper ex- tremity with it. Both muscles together can draw the shoulders
88
ANATOMY AND PHYSIOLOGY
back. If the hands grasp a bar above the head these muscles will assist to draw the body up. The largest two of L the " climbing muscles'' are the latissimus dorsi and the trapezius. Nerves. — Spinal accessory and middle cervical.
Note. — Observe in the illustration its tendinous area, which remains flat during action of the muscle.
Fron tails
Ear muscles
Chin / muscles
Sterno-mastoid
FIG. 76. — MUSCLES or THE HEAD AND NECK. — (Morris.)
Clinical Note.- — Spasmodic action of the trapezius is often the cause of wry-neck, or torticollis, and this may be increased by spasm of the splenius.
MUSCLES OF EXPRESSION 89
MUSCLES OF HEAD, AND FRONT AND SIDE OF THE NECK.
The muscles of expression are those of the scalp and face. They are closely connected with the under surface of the skin, or with each other; they have no deep fascia over them, and there- fore their slightest contraction is shown on the face, thus varying the movements and lines of expression.
Epicranial muscle. — On the forehead and the top and back of the head — a broad thin muscle made up of two distinct parts with an aponeurosis between them. The posterior part is the occipitalis, taking origin from the curved line of the occipital bone and ending in the aponeurosis on the top of the head. The anterior part is the frontalis, having origin in the aponeurosis, and passing down over the forehead to the insertion in the tissues of the eyebrows.
Action. — Principally to lift the eyebrows, producing the trans- verse wrinkles across the forehead which express surprise. The skin is closely connected with this double muscle so that the contraction causes movement of the scalp. (Some people can move the scalp backward and forward by contracting the two portions alternately.)
The aponeurosis extends in a thin layer at the side over the temporal region, giving origin to certain small muscles which move the ear. The scalp and ear usually move together.
Nerve. — Seventh cranial (or facial}.
Levator. palpebrae (elevator of the eyelid). — Within the orbit. Origin. — At the apex of the orbit. Insertion. — In the upper lid. Action. — It lifts the lid and opens the eye.
Nerve. — Seventh cranial. See page 343 for other Orb tal Muscles.
Corrugator. — The muscle which wrinkles the eyebrow. Origin. — The frontal bone. Insertion. — The under surface of eyebrow.
Action. — It draws the brows downward and inward toward each other; it is the frowning muscle.
Nerve. — Seventh cranial.
Orbicularis oculi. — The ring-like muscle of the eyelid. It is attached to the medial border of the orbit. Some of its fibers are in the lid — the palpebral portion — while others surround the
go ANATOMY AND PHYSIOLOGY
lids like a broad flat ribbon, forming the circular or orbital portion, and bearing the eyebrows (Fig. 76).
Action. — When the palpebral fibers contract the lids cover the eyeballs lightly; when the circular fibers contract the lids are pressed against the ball.
Nerve. — Seventh cranial.
Orbicularis oris (ring muscle of the mouth). — Surrounds the opening of the mouth, constituting the larger portion of the lips. The fibers have only one bony attachment — on the maxilla, below the septum of the nose.
Action. — It closes the mouth.
The lips themselves are moved in various ways by muscles above and below them — the elevators and depressors of the lips (all supplied by the seventh cranial nerve).
Special points. — Most of the changes in the expression of the face are caused by the action of the ring muscles and of those which are attached to them. For example, the lifting of the eyelids by the frontalis expresses sur- prise. The wrinkling of the brows by the corrugators speaks disapproval or bewilderment. The risorius, or grinning muscle, draws the corners of the mouth outward. The sneering muscle lifts the nostril and lip together. Pleasure is expressed by the lifting of the angles of the lips upward and outward, while grief depresses them. (There are but three of the depress- ors, or grieving muscles, on each side, and six for the manifestation of hap- pier feelings.)
MUSCLES OF MASTICATION, FIVE IN NUMBER
The temporal muscle. — Occupying the entire temporal fossa. Origin. — The floor of the fossa, and the temporal fascia covering it. Insertion. — The coronoid process of the mandible.
Action. — It closes the mouth and draws the mandible or lower jaw-bone backward.
N ' erve.-^-Fifth cranial (or tri-facial).
The masseter.— At the side of the face (Fig. 78). Origin.— The zygomatic arch. Insertion. — The lateral surface of the ramus of the mandible.
Action. — It closes the mouth and moves the jaw forward slightly.
Nerve. — Fifth cranial.
RIBBON MUSCLES 91
The internal pterygoid. — In the infra-temporal fossa covered by the ramus of the mandible on which it is inserted.
Action. — It closes the mouth and moves the jaw forward and sideways.
External pterygoid. — Also in the infra-temporal fossa and inserted on the mandible.
Action. — It moves the jaw forward and sideways.
Nerve. — Fifth cranial.
Buccinator. — Origin, from both the maxilla and the mandible on the alveolar borders. The fibers approach each other, interlacing and running for- ward; some of them join the lip muscles, constituting the insertion (Fig. 78).
Action. — It helps to close the mouth, and keeps the food between the teeth during the act of mastication.
Nerves. — Fifth and seventh cranial.
Temporal
Buccinator
FIG. 77. — THE TEMPORAL MUSCLE. — (Morris.)
By the action of the first four muscles the food is divided and crushed, and also ground; the external pterygoid is especially a grinding muscle. The function or use of these four would be somewhat limited without the aid of the buccinator.
MUSCLES IN THE FRONT OF THE NECK
The ribbon muscles, thin and flat, connecting the larynx and hyoid bone above, with the sternum, rib, and clavicula below.
9 2 ANATOMY AND PHYSIOLOGY
They are the sterno-hyoid, the sterno- thyroid, and the omo-hyoid (a
double-bellied muscle with an intervening tendon, the inferior belly being attached to the upper border of the scapula, the superior belly to the hyoid bone, while the tendon between them glides through a loop of fascia attached to the clavicula).
FIG. 78. — MUSCLES IN FRONT or THE NECK.
"i, 2, 3, Digastric muscle; 4, stylo-hyoid; 5, mylo-hyoid; 6, hyo-glossus; 7, 8, 9, sterno-mastoid; 10, n, 12, 13, 14, ribbon muscles; 15, pharynx; 16, occipitalis; 17, ear muscles; 18, trapezius; 19, 20, splenius; 21, levator scapulae; 22, 23, scalene; 24, deltoid; 25, pectoralis major; 26, right platysma; 27, 28, lip muscles; 29, masseter; 30, buccinator. — (Sappey.}
Action of the three muscles. — They draw the hyoid bone and the larynx downward, and steady them.
Nerves. — Ninth cranial,, or hypoglossal.
The digastric is another double-bellied muscle (Fig. 78).
The posterior belly is attached to the mastoid process (medial surface) ; the anterior belly to the under surface of the mandible close to the symphysis. The intervening tendon glides through a loop of fascia connected with the hyoid bone.
Action. — It draws the mandible downward, and opens the mouth. (It is assisted by some other short muscles connecting the mandible to the hyoid bone.)
Nerves. — Fifth and seventh cranial.
STERNO-CLEIDO-MASTOID 93
The mylo-hyoid (Fig. 78) is a flat muscle which forms the floor of the mouth, being attached by one border to the inner surface of the body of the mandible, and by the other to the hyoid bone, which, it will be remembered, is on a level with the mandible.
Action. — It can draw the hyoid bone forward in the act of swallowing, thus keeping the larynx out of the way of the food.
Nerve. — Fifth cranial.
The platysma. — As the muscles of the back and side of the neck are covered by the trapezius, so those of the front and side are covered by the platysma, which is a broad thin sheet of muscular fibers attached above to the mandible and the fascia of the side of the face, and below to the deep fascia on the front of the shoulder (Fig. 76). Like the face muscles, it is not covered by deep fascia, and, since it moves the skin, it is like them a muscle of expression. It draws the angle of the mouth downward, and strong contractions of the muscle assist in causing an appearance as of one in a "great rage." The action of this muscle in grazing animals is displayed when used to shake off insects which alight upon the skin of the neck.
Nerve. — Seventh cranial.
The sterno-cleido-mastoid (Figs. 78). is the most conspic- uous muscle in the side of the neck. Origin. — By two divi- sions, one on the sternum (sternal, or medial origin), the other on the clavicula (clavicular, or lateral origin). Insertion. — The mastoid process and upper curved line of the occipital bone.
Action. — Principally to pull the mastoid process toward the sternum and clavicula. If the right muscle contracts the right mastoid process comes downward and forward and the chin turns upward to the left. If the left muscle contracts the left mastoid is pulled downward and forward and the chin goes upward to the right. Both muscles together simply bend the head forward, or flex it.
Nerves. — Spinal accessory (and cervical).
Clinical note. — The sterno-mastoid is another muscle which is sometimes the seat of spasmodic contractions, causing wry-neck, or torticollis.
Levator scapulae. — The elevator of the scapula is an important muscle in the side of the neck. Origin. — The upper three or four transverse processes. Insertion. — The medial angle of the scapula.
Nerves. — Cervical.
94
ANATOMY AND PHYSIOLOGY
THE ABDOMINAL WALL
The abdominal wall has no bones except the lumbar vertebrae, being mostly muscular and aponeurotic. Each lateral half is composed of one vertical muscle in front, next to the median line; another in the back, next to the spinal column; and. three well- developed layers having fibers of different directions, at the sides.
Rectus abdominis (Fig. 80). — This is the vertical muscle in front. Origin. — The body of the pubes. Insertion. — The ensi-
±3
FIG. 79. — ANTERIOR SURFACE OF THE ABDOMINAL WALL. *» 2> 3» 7 1 Pectoralis major; 4, external oblique; 5, serratus anterior; 6, latissimus dorsi; 8, xiphoid appendix; 9, 9, 15, aponeurosis of ext. oblique; 10, 14, linea alba; n, umbilicus; 12, transverse lines of aponeurosis; 13, 13, subcutaneous abdominal ring; 16, 17, 18, 19, refer to muscles of neck; 20, deltoid. — (Sappey.) Lower border of aponeurosis is inguinal ligament.
form appendix and the cartilages of the fifth, sixth, and seventh ribs. It is therefore narrow below and broad above, and its outer
ABDOMINAL MUSCLES 95
border is curved from the seventh rib down to the pubes. This is indicated in the fascia over the muscle by a distinct line called the semilunar line (linea semilunaris).
Action. — It compresses the abdominal organs.
Nerves. — Lower thoracic and first lumbar.
Quadratus lumborum. — This is the vertical' ^muscle at the back (Fig. 74). Origin. — The crest of the ilium. Insertion.— The lowest rib and transverse processes of the upper lumbar vertebrae. It occupies the space at the back of the trunk between the thorax and pelvis, being covered by the erector spinae and latissimus dorsi muscles.
m
FIG. 80. — INTERNAL OBLIQUE AND TRANSVERSE MUSCLES. i, Rectus abdominis; 2, 2, 3, 3, internal oblique and cut edge of its aponeurosis; 4, 4, cut edge external oblique; 5, 5, spermatic cords; 6, aponeurosis ext. oblique turned down; 7, rectus, upper part removed; 8, 8, 9, transversus muscle; 10, umbilicus; n, 12, linea alba; 13, serratus anterior; 14, 15, cut edge latissimus dorsi; 17, 17, external intercostal; 19, cut edge external oblique. — (Sappey.)
Action. — It draws the rib down and the spine to one side— lateral flexion of the trunk .
Nerves. — Lower Thoracic.
The three layers at the side and front consist of the obliquus externus or external oblique; the obliquus internus, or internal
96 ANATOMY AND PHYSIOLOGY
oblique; and the transversus muscles. They occupy the space between the eight lower ribs above, and the ilium and pubes below. Being broad and flat they do not possess tendons of the usual kind, but many of their muscle fibers terminate in layers of white fibrous tissue called aponeuroses, which continue to the median line, there blending with the layers from the opposite side. This produces a firm interlacing of white fibers called the linea alba or white line, stretched between the ensiform appendix above and the body of the pubes below. It is a very strong and impor- tant line, through which, a little below the middle, the umbilical cord passes in the fetus; this point in the linea alba is indicated by the umbilicus, or navel.
The external oblique (Fig. 79) is the outermost of the three layers. Origin. — The lower eight ribs. Direction of fibers, downward and forward. Insertion. — Some fibers on the crest of the ilium; others in an aponeurosis which passes to the linea alba.
Nerves. — Lower thoracic.
Special point. — The lower border of the aponeurosis of this muscle between the spine of the ilium and the spine of the pubes is firm and unyielding, easily felt, and important to be recognized; it is called the inguinal ligament (or Poupart's ligament).
The internal oblique (Fig. 80) lies underneath the external oblique. Origin. — The lumbar fascia, crest of the ilium, and lateral half of the inguinal ligament. Direction of fibers, upward and forward. Insertion. — Some fibers on the lower three ribs, others in the linea alba, and the lowest ones on the crest of the pubes.
Nerves. — Lower thoracic and first lumbar.
The transversus (Fig. 80) is the innermost of the three layers. Origin. — The lower six ribs, the lumbar fascia, crest of the ilium, and lateral half of the inguinal ligament. Direction of fibers, transversely across the side of the abdomen, toward the front. Insertion. — In the linea alba, and the crest of the pubes. On the pubes it is blended with that part of the internal oblique which is attached to the same bone, making the conjoined tendon.
Nerves. — Lower thoracic and first lumbar.
Action, of the three broad muscles. — They compress the
SHEATH OF RECTUS MUSCLE
97
abdominal viscera and expel the contents of those which are hollow.
The fibers from the inguinal ligament, of both internal oblique and trans- versus muscles, arch downward to the pubes.
SHEATH OF THE RECTUS ABDOMINIS (FIGS. 79, 80)
In the lower fourth of the linea semilunaris, the entire thick- ness is continued forward as one layer in front of the muscles. In the upper three-fourths the linea semilunaris divides into two layers which meet again in the linea alba; thus a compartment is formed to be occupied by the rectus muscle.
This is called the sheath of the rectus, with its anterior and posterior layers, the anterior layer being thickest and strongest in the lower part where the greatest strain would be brought upon it.
Linese transversae (transverse lines). — At three different levels above the umbilicus the anterior layer of the sheath is held down to the rectus muscle by fibers forming transverse lines.
Note. — The location of all these markings — the semilunar line, the white line, and the three transverse — may be seen on the surface of the body during the action of the muscles; and in a piece of statuary representing the trunk they should be plainly indicated (Fig. 79).
FIG. 81. — THE DIAPHRAGM. Dotted lines indicate descent in contraction. — (Holden )
ROOF OF THE ABDOMEN
The roof of the abdomen is the diaphragm; it has no floor of its own, the pelvic floor serving for both cavities (page no). The diaphragm. — This is a broad, thin, dome-shaped muscle 7
98 ANATOMY AND PHYSIOLOGY
separating the abdominal and thoracic cavities. The central portion is aponeurotic, serving for the insertion of the remaining or muscular portion.
Origin. — i. By two vertical bundles at the sides of the lumbar vertebrae. These vertical portions are the crura of the diaphragm. Their fibers turn forward, crossing and interlacing before they end in the central tendon. 2. From arches of lumbar fascia and the lower boundary of the thorax (seventh to twelfth ribs and xiphoid appendix) .
Insertion. — In a flat central tendon, shaped like a clover leaf, near the center of the dome. The lateral portion of the muscle arch is higher than the central, forming a cupola on each side.
FIG. 82. — THE DIAPHRAGM, INFERIOR SURFACE.
e i, 2, 3, Tendinous leaflets; 4, muscle fibers; 5, 6, 7, tendinous arches; 8, 10, fibers arising from vertebrae; n, aorta — a large artery; 12, esophagus, leading to stomach; 13, opening for vena cava. — (Potter's Compe'nd of Anatomy.}
Action. — When the diaphragm contracts it becomes flattened, pressing upon the abdominal organs; when it relaxes, it springs back to its dome-shape, as high as the fourth or fifth rib, pushing gently against the lungs. (See p. 121.)
Nerve. — Phrenic and lower intercostal.
Special points. — This muscle ^forms the floor of the thorax, and at the same time the roof of the abdomen (convex floor, concave roof). There are three openings in it at the back part for the
ILIO-PSOAS
99
passage of a large artery and vein — the aorta and vena cava, and the esophagus.
With the muscles thus far described the walls of the cavities of the trunk — dorsal and ventral — are completed (see page 52).
INTERIOR ABDOMINAL MUSCLES
The psoas major and iliacus. — These are two muscles within the abdomen (on the posterior wall) which pass out over the brim of the pelvis into the thigh.
Psoas major. Origin. — The sides of the lumbar vertebra?. Insertion. — Trochanter minor of the femur.
12
FIG. 83. — ABDOMINAL MUSCLES, INTERIOR.
i-5,"Psoas 'minor and major; 6, attachment of psoas major to trochanter minor, 7, 7, 8, 8, iliacus; 9, 9, cut tendon rectus femoris; 10, 10, obturator externus; 11-13 quadratus lumborum; 14, 14, transversus. — (Sappey.)
Iliacus. Origin. — The iliac fossa. Insertion. — With the psoas on the trochanter minor of the femur.
Action. — They act together as one muscle, the ilio-psoas, to flex the thigh, at the same time rotating it, so that the foot turns outward.
100 ANATOMY AND PHYSIOLOGY
Nerves. — Lumbar and femoral.
Surgical note. — Disease of the lumbar vertebrae resulting in pus causes psoas abscess. The pus often follows the muscle fibers downward and appears below the inguinal ligament.
(The psoas minor is a small muscle in front of the major.) The transversalis fascia is a layer of loose connective tissue which completely lines the muscles of the abdomen; it is continuous with the iliac fascia on the iliacus muscle and with the pelvic fascia below.
CHAPTER VII MUSCLES OF THE EXTREMITIES
The muscles of the extremities are frequently named for their use, and they may all be grouped according to their action; as flexors, to bend the joints over which they pass, and extensors to straighten them; pronators and supinators; abductors and adduc- tors; and rotators, inward or outward. Their origins are not only from bones, but from fascia, and the fibrous septa between them. This is true of most muscles to .some extent, but particularly so in the extremities.
The principal bony attachments only are given here.
MUSCLES OF THE UPPER EXTREMITY
SHOULDER MUSCLES
Supraspinatus. — On thedorsal surface ofthe_scapula. Origin. — The supraspinous fossa, the tendon passing over the head of the humerus to the insertion on the top of the greater tubercle.
Action. — It lifts the arm away from body (abduction) .
Infraspinatus. — Also on the dorsal surface of the scapula. Origin. — The infraspinous fossa. """Insertion. — The greater tu~ bercle of the humerus (below the supraspinatus) .
Action. — It rotates humerus outwa.r^l (the palm turns forward) .
Nerve, both muscles. — Suprascapular.
Teres minor. Origin. — The axillary border of the^scapula. Insertion. —
The greater tubercle, just below the infraspinatus.
Action. — It rotates humerus outward (palm turns forward}.
Nerve. — A xillary.
Teres major. Origin. — Near the inferior angle of the scapula (on axillary border. ) insertion. — The shaft of the humerus (crest of lesser Tuber- cle), joining the tendon of the latissimus dorsi and acting with4t (Fig. 84).
Action. — It draws the arm backward, and rotates it inward (the palm turns backward}". ' -"
Nerve. — Subscapular (lower] .
101
102
ANATOMY AND PHYSIOLOGY
Subscapularis (Fig. 86). Origin.— The subscapular fossa. Insertion. — The lesser tubercle of the humerus.
Action. — It holds the head of the humerus in place and rotates it inward (the palm turns backward) .
The deltoid (Fig. 85). — Is triangular in shape and forms a sort of cap over the shoulder- joint. Origin. — The_ spine and'
acromion of the scapula, and the lateral portion ol the clavicula. Insertion. — The jateral surface of the humerus at the middle of the shaft,
"on the deltoid tuberosity.
Action.- — Principally to elevate the humerus to a Horizontal position (acting with the supraspinatus, an abductor of the arm).
Nerve. — A xillary.
The
anterior
(Figs. 75, 85).— A large flat
and important muscle wicn lies between the scula'lin5
19.
FIG. 84. — MUSCLES OF THE SHOULDER
16% the thorax^ Origin.-— By
17 separate slips from eight ribs, _
on the front and side of the Thorax, insertion. — The ver- tebral Sdrder of the scamrfa^ It lies close to the side of the thorax, covering a con-
2, 3, 4, 5, Triceps; 6, attachment to siderable portion of the ribs t
olecranon; 7, anconeus;~8, 8, g,jieltoid (por- tion removed); 10, supraspinatus; n, infra- spinatus; 12, 13, two extremities of teres minor (intervening portion removed); 14,
and intercostal muscles. Three actions. — It holds
teres major; 15, latissimus dorsi; 16, 17, 18, the scapula firmly in plafo 19, muslces of forearm.-T^^.) and pulls it forward^ thus
pushing the arm ahead. If the shoulders are held firmly jt can_
elevate the ribs, assisting inspiration. It sustains the weight of
the body when resting upon hands and knees, as in creeps
Nerve. — Long thoracic or external respiratory.
PECTORAL MUSCLES
103
BREAST MUSCLES
Pectoralis major. Origin. — Clavicular portion, on the sternal end of the calvicula; sterno-costal portion, on the surface of the sternum and on six upper ribs. Insertion. — By a broad strong tendon on the shaft of the humerus, on the crest of the greater tubercle (Figs. 79, 85).
18 19 1R
10 11
FIG. 85. — MUSCLES OF ANTERIOR ASPECT OF THORAX.
1-5, Pectoralis major; 6, 9, pectoralis minor; 7, subclavius; 8, deltoid; 10, anterior portion of anterior serratus; u, external oblique; 12, 13, latissimus dorsi; 14, teres major. — (Sappey.)
Action.— It draws the arm to the front of the thorax, opposing the latissimus dorsi; thus it also is a " rowing" muscle.
Thepectoralis minor is -entirely covered by the major.
Origin. — From three upper riba^the second, third, and fourth. In- sertion.— Th^coracoid process of the scapula. Action. — It pulls the shoulder downward. It may pull ribs upward in labored breathing or forced inspira-
Nerves of both muscles. — Anterior thoracic.
Note. — When the whole body is drawn upward by the hands, as when hanging from a trapeze, the two pectorals, the trapezius and the latissimus are acting together.
The subclavius is a small muscle lying in the subclavian groove between the clavicula and first rib. It may elevate the ribs or depress the clavicula.
IO4
ANATOMY AND PHYSIOLOGY
ARM MUSCLES Anterior
Biceps brachii (a two-headed muscle). Origin. — The scapula: the long head above the glenoid fossa, and the short head on the cora-
coid process. Insertion. — By one tendon on the tuberosity of the radius (Fig. 86).
Nerve. — Musculo-cutaneous.
7-1:
FIG. 86. — MUSCLES OF THE ARM. 2, 3, 5, Biceps and bicipital fas-
cia; 4, attachment of biceps to tuber- osity of radius; 6, coracobrachialis; radial. 7, 8,^ insertion of pectoralis major; 9, latissimus cisis! (insertion); 10, teres major; n, subscapularis; 12, bra- chialis; 13, 14, two heads of tricepsr — (Sappcy.)
Note. — If the biceps brachii begins to contract while the hand is pronated, the first effect would be to pull the radial tuberosity around and place the hand in the supinated position, then flexion would follow; in other words, the biceps may act as both a supinator and flexor.
The coraco-brachiaKs. — A smaller muscle, close to the biceps. Origin. — The tip of^ the coracoid process. In- sertion.^nJe shaft of hum ems, medial side, opposite the deltoid.
Action. — It lifts the humerus forward^
Nerve. — Muscuio-vutaneous.
The brachialis. — Is underneath the biceps. Origin. — The anterior surface of the humerus. Insertion. — The tu- bercle of the ulna, just below the coro- noid process.
Action. — With the biceps it flexes the forearm.
Note. — This is a broad muscle and covers the front of the elbow-joint.
Nerve. — Musculo - cutaneous and
ARM MUSCLES Posterior FIG. 84
The trjflnpri hrnrhii „ (-} three- headed muscle). Origin. — The long head, on the scapula, just below the glenoid fossa; the medial and lateral heads on the pos- terior surface of the humerus, separated by the groove for
FLEXORS OF FINGERS 105
dial nerve. Insertion. — The (top of the) olecranpn process of the ulna.
Action. — It extends the forearm (opposing the biceps).
Nerve. — Radial.
Note. — The back of the triceps is covered at its lower portion by a fibrous layer (aponeurosis) which receives many of the muscular fibers. In action, the three heads swell while this fibrous layer remains flat.
MUSCLES OF THE FOREARM Anterior
The superficial flexors. — The medial epicondyle of the humerus gives origin to a group of superficial muscles which flex the wrist, and fingers (Fig. 87).
Flexor carpi radialis, or radial flexor of the wrist. Origin.— The medial epicondyle. Insertion. — The base of the second metacarpal bone (that of the index-finger).
Nerve. — Median.
Flexor carpi ulnaris, or ulnar flexor of the wrist. Origin.— The medial epicondyle and dorsal border of the ulna. Insertion.— The base of the fifth metacarpal bone (after attachment to the pisiform and unciform bones).
Action of the two. — To flex the wrist.
Nerve. — Ulnar.
Flexor digitorum sublimis, or superficial flexor of the fingers. Origin. — The medial epicondyle, the upper extremity of the ulna, and the shaft of the radius (the three long bones) . Insertion. — By four tendons, one for each finger, on the second row of phalanges.
Action. — It flexes the second joints, of the fingers, but not the finger-tips.
Nerve. — Median.
Deep flexors. — The shafts of the bones give origin to the deep flexors of the fingers and thumb, which act upon the third row of phalanges.
Flexor digitorum profundus, or deep flexor of the fingers. — Is underneath the superficial flexor. Origin. — The shaft of the ulna. Insertion. — By four tendons, on the third or last row of phalanges.
Action. — It flexes the finger-tips.
io6
ANATOMY AND PHYSIOLOGY
FIG. 87. — MUSCLES OF THE FOREARM. i, 2, 4, 4, 5, Muscles of arm; 3, tendon of insertion of biceps; 6, round pronator; 7, radial flexor of wrist; 8, 9, palmaris longus; 10, n, ulnar flexor of wrist; 12, 13, brachio-radialis; 14-18, muscles and ten- dons belonging td posterior of forearm; 19, 19, superficial flexor of fingers; 20, 20, 21, 21, tendons of the same, showing fissure; 22, 22, tendons of deep flexor com- ing through fissure to reach the third row of phalanges. — (Sappey.)
FIG. 88. — MUSCLES OF THE FOREARM,
DORSAL ASPECT.
i, Aponeurosis of triceps; 2, upper end of brachio-radialis; 3, 4, long radial extensor of wiist; 5, 6, short radial ex- tensor of wrist; 7, 8, 8, 9, 9, extensors of thumb; 10, 10, annular ligaments; n, 12, 12, common extensors of fingers; 13, 14, special extensors for index and little fingers: 15, 16, ulnar extensor of wrist; 18, ulnar flexor of wrist; 19, posterior border of ulna; 20, olecranon process of ulna; 21, media lepicondyle. — (Sappey.)
PRONATORS 107
Note. — Since the tendons of the superficial flexor stop at the second phalanges, while those of the deep flexor pass to the third phalanges, there is a fissure in each superficial tendon just before it ends, through which the deep tendon passes forward to the bone of the finger-tip (Fig. 87).
Nerves. — Median and ulnar.
Flexor pollicis longus, or long flexor of the thumb. — Origin. — The shaft of the radius (under flexor sublimis). Insertion. — The last phalanx of the thumb.
Action. — It flexes the tip of the thumb.
Nerve. — Median.
Note. — These tendons for the fingers and thumb lie in the deep groove on the front of the carpus. Friction between them is prevented by sheaths of synovial membrane — vaginal synovial membranes.
THE Two PRONATORS, THE ROUND AND THE SQUARE
Pronator teres, or round pronator (Fig. 87).
Origin. — The medial epicondyle, and a small slip from the ulna (coronoid process). It passes across to the lateral side of the radius, to the insertion at the middle of the shaft.
Nerve. — Median.
Pronator quadratus, or square pronator.
Origin. — The shaft of the ulna. Insertion. — The shaft of the radius. It lies just above the wrist and underneath the long muscles (close to the bones).
Nerve. — Median.
Action of the two pronators. — They rotate the radius so as to turn the palm downward (or backward).
One slender muscle, which is superficial to all, is the palmaris longus. It arises on the medial epicondyle and is attached below to the palmar fascia to keep it tense — a tensor of the palmar fascia.
Nerve. — Median.
Note. — It is understood that the muscles arising from the epicondyle have a common tendon of origin.
Practical point— Observe, by experimenting, that flexion and moderate pronation are naturally performed together, and are associated in the major- ity of the motions which are required of the upper extremity.
MUSCLES or THE FOREARM Posterior (Fie. 88.)
The lateral epicondyle of the humerus and the ridges above it give origin to the muscles which extend the wrist and fingers.
108 ANATOMY AND PHYSIOLOGY
Extensor carpi radialis longus, or long radial extensor of the wrist. Origin. — Lateral border and epicondyle of humerus. Insertion. — The base of the second metacarpal bone.
Nerve. — Radial.
Extensor carpi radialis brevis, or short radial extensor. Origin. —The lateral epicondyle. Insertion. — The base of the third metacarpal bone.
Nerve. — Deep branch of radial.
Extensor carpi ulnaris, or ulnar extensor of the wrist. — Origin. -The lateral epicondyle and dorsal border of the ulna. Inser- tion.— The base of the fifth metacarpal bone. Action of the three. — They extend the wrist.
Nerve. — Deep branch of radial.
Extensor digitorum communis, or common extensor of the fingers. Origin. — The lateral epicondyle. Insertion. — By four tendons, on the second and third rows of phalanges, in such a way that it can extend the bones of either row separately or both at the same time.
The little finger has a special extensor for its tip (extensor minimi digiti). The index finger also has a special extensor (extensor indicis), and the thumb has three — two for its phalanges, and one for its metacarpal bone. By forci- bly extending the thumb these three tendons are brought into view, the one for the tip of the thumb being at a little distance from the other two; thus they bound a little hollow which has been called the "anatomic snuff box."
Nerves of all. — Deep branch of radial.
THE Two SUPINATORS
The supinator. Origin. — The lateral epicondyle and upper end of the shaft of the ulna. It winds around the head and neck of the radius to the insertion on upper part of the shaft. This is the chief supinator; it is entirely covered -by other muscles.
Action. — It rotates the radius and turns the dorsum of the hand downward or backward.
Nerve. — Deep branch of radial.
The branchio-radialis (Fig. 87). Origin. — The lateral border of the humerus. Insertion. — The styloid process of the radius.
THENAR AND HYPOTHENAR MUSCLES IOQ
Action. — It assists in both flexion and supination of the forearm. (This muscle was formerly called the long supinator.) Nerve. — Radial.
Annular Ligaments
These are special bands of deep fascia holding in place those tendons which pass the wrist-joint. They include the tendons in canals through which they glide freely. Friction is prevented by synovial sheaths within the canals. The fascia which binds down the extensor tendons is the dorsal ligament of the wrist; that which confines the flexor tendons is the transverse ligament of the wrist.
MUSCLES OF THE PALM (Fie. 87)
There is a group of palmar muscles which move the thumb in various directions (flexion, abduction, adduction, and so on). They form the elevation called the thenar eminence, or the "ball of the thumb." A similar group for the little finger forms the hypothenar eminence.
They arise mostly on carpal bones and deep fascia and are inserted on first phalanges. In the hollow of the hand between these two eminences lie the long tendons, already described, on their way to the fingers; also some small muscles between them and beneath them.
The interosseous muscles fill the interosseous spaces. The action of the dorsal group is to spread the fingers apart (abduction) while that of the palmar group is to bring them together (adduction).
Note. — A line drawn from the middle of the wrist to the tip of the middle finger is called the median line of the hand. To abduct the fingers and thumb is to draw them away from this line — in other words, from the middle finger. To adduct them is to draw them toward the middle finger.
Nerves. — To the hypothenar muscles. — Ulnar. To thenar muscles. — Median and ulnar. To inter ossei. — Ulnar.
The muscles in the palm are covered by particularly dense, deep fascia called the palmar fascia, or palmar aponeurosis.
MUSGLES OF THE LOWER EXTREMITY The Pelvis— Interior
False pelvis. — The iliacus is the only muscle in the false pelvis; it is already described with the psoas major, page 99.
no
ANATOMY AND PHYSIOLOGY
True pelvis. — The piriformis and obturator interims. These muscles arise from the interior of the pelvis and pass out through the sciatic notches — the piriformis through the greater notch and the obturator internus through the lesser notch. They are inserted on the great trochanter and act to rotate it outward.
They are supplied by nerves which are branches of the sacral plexus.
They are short muscles but thick and very strong.
The floor of the pelvis consists of two flat muscles on either side, the levator ani and the coccygeus.
Sacrum
piriformis
Coccyx 1
Levator ani (di- vided below the "white line")
Space for obtu- rator internus
Rectum Prostate
Symphysis
Passage for glu- teal vessels and nerve
Piriformis
Passage for sci- atic and pu- dic vessels and nerve
Ischial ?pine
Coccygeus Cellular interval Levator ani
Capsule of pros- tate, and pu- bo- prostatic ligaments
FIG. 89. — INTERIOR AND FLOOR OF THE TRUE PELVIS. — (Morris.}
The origin is on the interior of the pelvic wall — that is, on the pubic bone and the spine of the ischium, and a line of fascia between the two points. Insertion. — The muscles meet each other in the median line, being also attached to certain pelvic organs (bladder and rectum in* the male; bladder, rectum,' and vagina in the female) and to the coccyx. Th'eir action supports the pelvic organs, espe'cially the rectum, and lifts them in various motions of the body, as in respiration.
Nerves. — From sacral nerves.
Special notes. — These two muscles form a concave floor like an inverted dome, which is the pelvic diaphragm. When this dome contracts it rises.
There are two openings in the pelvic floor for the bladder and rectum, and a third opening in the female pelvis for the vagina.
GLUTEUS MAXIMUS
III
The pelvic fascia is a continuation of the transversalis fascia which lines the abdomen and of the iliac fascia which covers the iliacus muscle. It covers the obturator muscle and its fascia and the muscles of the floor, and forms ligaments for the pelvic viscera.
THE PELVIS — EXTERIOR
Three gluteal muscles. — From the three gluteal lines of the os coxae and the spaces above them, arise three gluteal muscles.
Gluteus minimus. Origin. — The in- ferior line and space above it. Insertion. —The front of the great trochanter.
Action. — It abducts the thigh and ro- tates the femur slightly inward (so that the foot turns in).
Gluteus medius. Origin. — The an- terior or middle line and space above it up to the crest. Insertion. — The outer surface of the great trochanter.
Action. — Abduction of the femur and some rotation outward.
Nerve of both. — Superior gluteal.
Gluteus maximus. Origin.—
The posterior line and space behind it to the crest (also from the back of sacrum) . Insertion. — The back^ of great trochanter and the ridge below it, also the deep fascia, or fascia lata.
Action. — External rotation of the femur; it is also a powerful exten-
FIG. 90. — THE GLUTEUS MAXTMUS. (Fascia removed.) — (Sappey.}
sor of the hip-jonr| nTm6unting steps.
when one rises from the sitting position, or It also abducts the thigh.
Nerve. — Inferior gluteal.
Obturator externus. Origin. — The obturator membrane and bone around it. Insertion. — The fossa of the great trochanter. Action. — External rota- tion of the femur. (Fig. 83.)
Nerve. — Obturator.
112
ANATOMY AND PHYSIOLOGY
Practical point. — Observe the number of muscles for external rotation and note that the usual position of the foot is with the toes turned outward.
FIG. 91. — MUSCLES OF THE THIGH.
MUSCLES OF THE THIGH Anterior
On the front and the sides of the femur are the muscles which extend the Jeg^-four in number; they blend at their insertion and therefore constitute a four- headed muscle, the quadriceps femoris^ They are the rectus jemons, the vastus later alis, vastus medialis and the vastus intermedius.
Rectus femoris. Origin. — The an^ terior inferior spine pf tV>p j]jujn and the upper border of the acetabulum. The three vasti. Origin.' — On the linea as- pera and the three surfaces of the femur. Insertion of the four. — By one tendon passing in front of the knee^joml L6""the tubercle of me tibia. (It encloses the patella and has been improperly called the ligamentum patellae.)
Action. — They extend the leg as in walking, or with great force in kicking; these muscles also keep the patella in place during various positions of the knee.
Nerve. — Femoral.
The sartorius. — The longest muscle
i, 2, Iliacus aftd psoas; 3, . _ ,-
4, tensor fascia; lata;: 5, sar- in the body; it passes across the front
. the quadriceps. Origin.-Thejmte-
medialis; 9, gracilis; 10, ad- rior superior spine nf fh«* ilnirn Inser-
i r ~" ,.,.
. — me inner surface of the tibia,
just below the head.
Action.- — Since it passes across to the medial side of the thigh, and behind the medial epicondyle, it flexes the leg and at the
HAMSTRING MUSCLES
same time lifts it in such a way that when both legs are acted upon together, they are flexed and crossed, hence the name, signifying "tailor" muscle"
Nerve. — Femoral.
The tensor fasciae latae. — Is attached to the anterior part of the crest of the ilium between two layers of the fascia lata; it makes tense the lateral portion of the fascia which is connected with the tibia, or the ilio-tibial band. (This is felt like a strong cord above the lateral epicon- dyle.) It also rotates the thigh inward (Fig. 91).
Nerve. — Superior gluleal.
MUSCLES or THE THIGH
Posterior
The muscles are three in num- ber— the biceps femoris, semitendi- nosus, and semimembranosus (Fig.
93)-
The biceps femoris. Origin.—
head on trie Tuber of the is- chium, short head on the linea as- pera (lateral lip). Insertion. — The head of the fibula.
The ^emitendinosus and the semimembranosus also arise on the tuber of the ischium, and are inserted on the tibia, medial sur- face and back of head. (Their
names indicate their shape, one FIG. 92.— MEDIAL ASPECT OF THE i • j. • i if •, i THIGH AND PELVIS.
being tendinous m half its length, ,_ a> ^ 4_ Iliacus> psoas_ ol,tura. and the other aponeuro tic, or mem- tor, piriformis; 5, gluteus maximus; branous" ") 6' Sartorius5 7. gracilis; 8, semitendin-
osus; 9, semimembranosus; 10, n, Action.— These three muscles I2' tendons of sartorius, gracilis, and
semitendmosus; 14, tendon of semi- act together to flex the knee. membranosus — (Sappey.)
Nerve to the three. — Sciatic.
Notes.^ — They also assist the gluteus maximus to extend the thigh, as in rising from a chair. The biceps tendon may be feK
114
ANATOMY AND PHYSIOLOGY
Fascial insertion of gluteus maximus
Biceps
Vastus laterali s
Plan tans
Gastrocnemius
Soleus
Peroneus longus
S emi-membranosus
Semi-tendinosus
Gracilis
Tendon of semi-membranosus
Sartorius
Flexor digitorum longus
Tendo Achillis
FIG. 93. — POSTERIOR OF THIGH AND LEG AND HAMSTRING TENDONS. — (Morris.)
POPLITEAL SPACE
behind the lateral epicondyle; the two others, behind the medial epicondyle, making the borders of a deep space — the popliteal space, or ham. They are called "hamstring" tendons.
f Lateral side, biceps femoris.
Hamstring tendons.
Medial side
The popliteus is a flat muscle behind the knee- joint, forming part of the floor of the popliteal space.
The most important muscles in the me- dial side of the thigh are the four adductors (Fig. 94).
The adductor longus. Origin. — From the su- perior ramus of the pubes. Insertion. — The mid- dle of the linea aspera.
The adductor brevis. Origin. — Upper part of the pubic arch. Insertion. — The linea aspera be- hind and above the longus.
The adductor minimus. Origin. — The lower part of the pubic arch. Insertion. — The linea aspera, behind the brevis (upper part).
The adductor magnus. Origin. — Pubic arch and tuber of the ischium. Insertion. — Linea as- pera (behind the others), and medial epicondyle.
Action of the four.— They all adduct the femur (rotating it outward) and draw tfieT tnighs together as in horseback riding.
tferve to the four. — Obturator, and great sciatic to a portion of adductor magnus.
Note. — The magnus makes a broad sheet of mus- cle between the quadriceps which extends the knee, and the muscles on the back which flex it. The longest and strongest fibers of the magnus run between the tuber of the ischium and the medial epicondyle. They rotate the femur inward.
semitendinosus. semimembranosus. sartorius. gracilis.
FIG. 94. — ADDUCTORS. i, 2, 3, Femur, ilium, pubes; 4, external obtu- rator muscle; 5, 6, 7, 8, 9, 10, adductor muscles; n, 12, openings for ves- sels passing to back part of thigh. — (Sappey.)
MUSCLES OF THE LEG
Anterior
These muscles flex the ankle and extend \]\ The muscles in the front of the leg are between the tibia and the
1 Note. — These movements are dorsal flexion.
n6
ANATOMY AND PHYSIOLOGY
fibula; the medial surface of the tibia, having no muscles upon it, is caned subcutaneous.
The tibialis anterior. Origin. — The shaft and head of the tibia (lateral surface) and the interosseous membrane.
Insertion.' — The first cuneiform and first metatarsal bones.
Nerve. — Deep peroneal.
The peroneus tertius. Origin. — The shaft of the fibula (lower part) . Insertion. — The fifth metatarsal bone.
Action of the two.'— To flex the ankle. The tibialis acting alone lifts the medial border of the foot; the peroneus lifts the lateral border.
Nerve. — Deep peroneal.
The extensor hallucis longus, or lon^eo tensor of the great toe._ Origin. — The shaft of the fibula and the mterosseous membrane. Insertion. — The last phalanx of the great toe.
Action. — To extend the great_toe. ^
Nerve. — Deep peroneal.
The extensor digitorum longus, or long extensor of the toes. Origin.- — The shaft of the fibula and interosseous membrane (a few fibers from head of tibia). Insertion. — By four tendons on the second and third pha- langes of the four lateral toes, like the similar extensor of the fingers.
Action. — To extend the toes.
Nerve. — Deep peroneal.
Note. — These two muscles, since they pass
FIG. 95. — MUSCLES OF THE LEG, ANTERIOR.
i,Rectusfemoris;2, tibia; 3, tibialis ante- rior; 4, long extensor of toes; 5, long extensor of great toe; 6, peroneus tertius; 7, 8, "pieroneus^ JoHgUS, p. brevis;^cJ7*io, ta^Terar amh~medial heads, _gastrocnemiusi. n, short extensor oP toes; 12, annular liga- ment. — (Sappey.)
in front of the ankle-joint, flex it.
On the dorsum of the foot the extensor digitorum brevis has four slender tendons for the four medial toes.
Nerve. — Deep peroneal.
MUSCLES OF THE LEG
117
MUSCLES OF THE LEG
Posterior
These muscles extend the ankle and flex the toes; they all pass behind the medial malleolus. They are covered by the calf muscles.
The tibialis posterior. Origin. — Shaft of bath tibia and fibula and the interogseous membrane. Insertion. — Navicular and first cuneiform bones.
Action.— Extension of the ankle.
Nerve. — Tibial.
The long flexor of the great toe, or flexor hallucis lon- gus.— Origin.— ^hajt ot hbUla. 'Insertion. — Last phalanx of the great toe (Fig. 96}.
Nerve. — Tibial.
Long flexor of the toes, or flexor digitorum longus. — Origin. — Shaft of fibula. Insertion. — By four tendons on the last phalanges of the four lateral toes (Fig. 96).
Action of these two muscles. — Flexion of the tips of the toes.
^erve. — Tibial.
FIG. 96.— Mus-
LEG — LATERAL SIDE (Fie. 97)
Peroneus brevis. Origin. — Shaft of fibula. Insertion.— Base of fifth metatarsal bone. The tendon passes behind the lateral malleolus.
Peroneus longus. Origin. — Shaft of fibula. Insertion. — In the sole of the foot, first cuneiform and first metatarsal bones. Tlie tendon passes DLE LAYER. behind the lateral malleolus and crosses in the cle^V^T
sole to the medial border of the foot. toes dividing into
A ,. f , . four tendons; 3, ten-
Action of these two muscles. — They extend don of long flexor of
the ankle and lift the lateral border of the foot? f^k^ta/muscles'
Nene to both-Superficial peroneal. ""iEiTrslSfS
sheath of tendon of JNote. — As the tibialis anterior and pero- peroneus longus; n,
neus tertius flex the foot, so the tibialis pos- terior and peroneus brevis extend it.
Orthopedic note. — The P. longus makes a chord for the transverse arch of the foot, being the most important muscle to preserve that arch from being flattened.
n8
ANATOMY AND PHYSIOLOGY
CALF MUSCLES (FIGS. 93, 97)
Triceps surse, and plantaris.
The gastrjgcjififliius. Origin. — Bv two hea^s iust above the
i i "5^'^^r . i r
condyles of the femur.
Insertion. — On the calcaneus.
Note. — The two heads form the lower boundaries of the popliteal space.
The soleus is covered by the gas- trocnemius. ^Origin. — Medial border of the tibia and lateral border of the fibula. Insertion. — The os calcis, with trie above muscle.
Action of the two. — They join to form one muscle, the triceps surae (or triceps of the calf), which has the strongest tendon in the body, the tendo calcaneus (tendon of Achille^) by which they are attached to the os calcis, and, therefore, they lift the he'e^ If the muscles of both legs act at the same time, the whole body is lifted on the toes.
Nerve to both. — Tibial.
The plantaris. Origin.— With the outer head of the gastrocnemius. Insertion. — With the tendo calcaneus.
Note. — The belly is short and small; the
,9-itie
FIG. 97. — LATERAL ASPECT AND CALF or LEG.
i, 2, 3, 4, Lateral view, mus- cles passing in front of ankle; 5, 6, peroneus brevis and p. lon- gus (behind ankle) ;* 7, 8, soleus tendon is the longest in the body, and gastrocnemius; 9, hea3~Df
fibula! 10, biceps femoris; n, The calf muscles constitute a group
Ach^ms^^armula/li a.men° °f &reat Power> as bY them one lifts 16, 17, insertions of peroneus oneself to stand upon the toes, tertius and brevis; 18, short ex- ,_. . A £ 1^-
tensor of toes; 19, plantar mus- The sole of the foot, or plantar cle; 20, patella.— (Sappe)?.) region, resembles the palm of the
hand in having special groups of mus- cles for the great and little toes, with the long flexor tendons lying between them, and a dense fascia covering them. This is called the plantar fascia.
The nerves are medial and lateral plantar.
PHYSIOLOGY OF MUSCLES IIQ
Annular Ligaments
The tendons which pass from the leg to the foot are kept in place by special ligaments, anterior and lateral, and surrounded by synovial sheaths as in the wrists.
POINTS. — Eversion of the foot, or lifting the medial border, is done by the tibialis anterior.
Inversion. — Or lifting the lateral border, by the peroneus tertius, and peroneus longus.
Adduction. — By deep posterior muscles of the leg.
Abduction. — By lateral muscles of the leg.
RESUME.
Observe certain similarities and differences in the extremities. Extension of the elbow is accomplished by the three-headed muscle, the triceps. Extension of the knee requires a powerful four-headed muscle, the quadriceps.
The great toe is on the medial border of the foot, the thumb is on the lateral border of the hand. This is so because the terms medial and lateral are applied to the pronated position of the lower extremity and the supinated position of the upper extremity.
In the upper extremity the joints are all flexed in one direction, as though the limb might be rolled up. In the lower extremity they flex and extend alternately, as though the limb were folded back and forth.
STRUCTURE AND PHYSIOLOGY OF MUSCLES
A complete muscle is a complicated structure. It consists of:
First, the essential muscle substance in the muscle cells, p. 83.
Second, connective tissue wrappings and partitions.
Third, tendons or aponeuroses, or both.
Fourth, blood- and lymph-vessels in great abundance.
Fifth, muscle nerves.
The connective tissue supports all of the other structures and protects the muscle, preserving its shape and stability.
The tendons and aponeuroses provide a means whereby the attachment to other organs is kept within a small space.
EXAMPLE: The biceps of the arm contains many fibers, but the slender tendons of this muscle occupy only small areas upon the surface of the bones. The aponeurosis of that very powerful muscle, the quadriceps femoris, receives
120
ANATOMY AND PHYSIOLOGY
the insertion of the muscle fibers, and by this means only a narrow surface is required for insertion upon the bone. But for arrangements like these, the skeleton would of necessity be inconveniently large.
The blood-vessels bring the nutritive fluid which, in the tissue- spaces, bathes each little fiber, and is gathered up by the lymph- vessels. One-fourth of the blood in the body is in the muscles.
The nerves bring to each fiber its natural stimulus to action.
The work of muscle tissue is done in the fiber cell. This, when stimulated, contracts, bringing the two ends of the fiber nearer to each other, and naturally the fiber swells as it shortens. So with the myriad of fibers in a muscle; when they contract, the muscle swells and shortens (Fig. 98) illustrates the changes pro-
FIG. 98. — SHOWING CHANGE OF SHAPE IN CONTRACTION. — (Brubaker.)
duced). This results in motion, which appears as the organs attached are moved. One-third of the body weight is muscle tissue.
AlFskeletal muscles are so attached as to be tense, that is, they are just a little stretched, so that it is easier for them to act than not. (A cut across a muscle releases it from tension and leaves a gaping wound.) See p. 123, tension and tonus.
The actions of muscles are regulated by their attachments, and the function is often expressed in the name. If muscles or their tendons pass in front of a joint, for instance, causing flexion, they are frequently called flexors; or if they pass behind such joints, they may be called extensors; and so with other muscles and joints. Examples: Flexors of the wrist, extensors of the fingers, etc. Many other examples will occur to the student, as abductors, adductors, pronators, etc.
ACTION OF DIAPHRAGM 121
As the location determines the function of a muscle, so it often suggests the name, as the pectoralis major and minor, the inter- costals, etc. Sometimes the shape is named, as the orbicularis of the mouth or of the eyelids (orbicular muscles, or sphincters, surround and control openings.) Shape and location may together suggest a name sometimes, as the latissimus dorsi, the rectus abdominis (broadest of the back and straight of the ab- domen) and others, expressing or implying the function of the muscle.
One of the most useful and interesting muscles in the body is the diaphragm. Although a voluntary muscle in structure, it is asso- ciated with visceral action. (For general description see page 98.)
The special interest attending this muscle arises from its location as well as its structure. Situated between the great cavities of the trunk it acts upon the organs belonging to both. In contraction, it encroaches upon the cavity of the abdomen pressing upon abdominal organs, and thus aids in expelling the contents of abdominal and pelvic viscera. In this act (expulsion from abdomen or pelvis) it is fixed in contraction (holding the breath) so that other muscles can act efficiently. Examples: defecation, parturition. Ceasing to contract it returns to its inac- tive or dome-shape; and as this is accompanied by slight ab- dominal pressure upward, the effect upon the thorax is to shorten it, causing gentle pressure upon the lungs.
In contraction, therefore, it compresses the abdomen and enlarges the thorax; in relaxation, it enlarges the abdomen and compresses the thorax. This alternate enlargement and com- pression of the thorax explains its most important function — that of a breathing muscle, especially a muscle of inspiration.
Special points. — The lateral portions of the diaphragm are the most movable portions, being mostly muscular. Here the lungs rest upon the falling and rising floor, themselves alternately ex- panding and contracting. The heart lies upon the least movable portion — consequently the diaphragm supports the heart but does not press against it unless pushed up from below.
Similar functions pertain to another muscle constituting the floor of the pelvis (the levator ani and coccygeus taken together), which rises and falls with the displacement and functionating of abdominal organs. With the combined contraction of these two,
122 ANATOMY AND PHYSIOLOGY
and relaxation of the diaphragm, the whole body of abdominal and pelvic organs moves upward, and vice versa.
Passing to the consideration of more complicated movements. For respiration we must have the muscles of the thorax; for swallowing or deglution, the muscles of the tongue and throat; for speaking, those of the tongue and face.
The arms and hands become organs of prehension when by use of their numerous muscles they reach out to gather things in; the lower limbs are organs of locomotion, only because their muscles enable them to bear and transport the body from place to place. Even the ability to stand still is due to a balanced tension of mus- cles, which keeps the joints quiet.
Finally, various emotions may be expressed by muscle-action without a spoken word, both by changes of the face (referred to, .p. 88) and gestures of the body. Compare the erect posture of the person ready and alert, with the drooping figure of despond- ency or the lax one of indolence. Read the meaning of the firm, quick footstep, and contrast it with the uncertain and halting one. Note how the hand may welcome, or repel. Even the eye would be far less expressive were the iris immovable. Indeed, we might well see a literal meaning in the old adage — " Actions speak louder than words." Thus muscle action means much more than simple movement, and it all depends ultimately upon the specially developed attributes of the muscle cell — contractility, extensibility, elasticity.
And thus we find that all functions of the body depend in the beginning upon muscle action, as the heart itself is a collection of muscles influencing the entire body, since without circulation of blood all processes of life must cease.
Muscle Stimulus. — The action of skeletal muscles as we ordinarily see them, expresses the result of the response of muscle tissue to the natural and direct stimulus of nerves. (Nerve im- pulses1 originate in the brain and spinal cord in response to sense impressions, and will be studied in connection with the nervous system.) Certain other stimuli cause temporary muscle action — for example, the contact of acids (chemical], a sharp blow (mechan- ical), electricity, etc.
Allusion has already been made to the tension of muscles pro-
1 An unsatisfactory term, but in common use.
MUSCLE TONE 123
duced by the slight stretching of their attachments, as though the bones had outgrown them a very little. The tension is in itself a stimulus, and is increased by what is called normal muscle tone.
Slight contractions of fibers are continually going on, caused by various delicate stimuli — so delicate that we are not always conscious of them although the muscle is; these contractions constitute muscle tone (tonus) which is important in several ways. First, it holds the muscles ready for instant action, making labor easier; second, it maintains a steady, although slight, production of body heat; third, it assists the steady flow of circulating fluids —blood and lymph; and fourth, it maintains favorable conditions in internal organs for the processes of secretion and excretion.
Although unconscious of normal muscle tone, we can often recognize the increase of tone. One example is the effect of cold; shivering is an instance of exaggerated muscle tone (it is however somewhat complex). Again, some emotions — as fear, anger, joy, sorrow, surprise, etc., always increase muscle tone. The expression "all strung up" is in a sense accurate, if not elegant. Also, an attitude of sustained attention produces the same effect and is often prolonged to the verge of conscious fatigue. Some idea of the degree of energy exerted in maintaining increased tone may be derived from the feeling of languor which follows it; people often speak of feeling the "relaxation" after excitement.
In all of these conditions, the heart is quickened more or less; and, in short, whatever cause, mental or physical, increases the rapidity of the circulation, will contribute to an increase of muscle tone, by preserving nutrition and removing waste matters.
Diminished tone is the result of overuse or of poor nutrition — either of nerve or of muscle, or both- — the effect being a tired feeling, or manifesting itself in various ways, such as inability to work, physical and mental inefficiency, etc. The need of a "tonic," or to be "toned up," is a common complaint.
Rest is necessary for the restoration of muscle tissue after work, in the ordinary activities of life, and still more after excessive exercise, in order that the renewal of muscle plasma may be accomplished and a store of material laid up for further use. This cannot be brought about while the muscle is doing visible work.
124 ANATOMY AND PHYSIOLOGY
Massage is beneficial in conditions of nerve-muscle tire, because it improves the circulation while the patient is in a passive state, so that better nutrition is secured and accumulated waste re- moved, without the necessity for effort by the patient. (The same is true of bruises and sprains.) No bad results will follow moderate overuse, provided sufficient rest be promptly secured. The expression "a healthy tire" is a logical one, because by reasonable use a muscle grows, if suitable resting time is secured. Beyond a reasonable limit, however, overuse is injurious; the muscles work irregularly, perhaps painfully; nutrition declines; wastes accumulate, and the will is no longer in control. Writer's cramp is a familiar example.
,The various stations and postures of the body are made possible by properly adjusted muscle groups, which enable us to preserve our balance in different positions. It is here that the extensibility and elasticity of muscle tissue are of greatest impor- tance. Sitting and standing, as well as walking and running, are states of activity, whereby the flexor and extensor muscles (and associated groups) oppose each other in equilibrium. It is truly "hard work to keep still."
The activities of muscles and nerves are so closely associated that they cannot be well understood apart, and will be further studied in Chapters XX and XXI.
Rigor Mortis. — It is already stated that muscle fibers are composed of muscle cells ; the cell consists of muscle plasma encased in a delicate substance called sarcolemma. The plasma contains minute fibrils and various nutrient substances, mostly proteins (page 153). Upon the death of the body coagulation of muscle plasma occurs and certain proteins are separated from the plasma in the form of a clot. (Myosin and Myogen fibrins.) This coagulation results in a firm contraction of the muscle fibers, and a general rigidity, called rigor mortis. It appears first in the muscles of the lower jaw, and, advancing downward, gradually involves the upper extremities and the whole body.
In the case of chronic disease, or of defective blood supply, the rigor appears soon (it may be as early as fifteen minutes) and passes soon. After an acute disease it appears late and lasts longer.
The disappearance of rigor mortis is due to the formation of acids in the muscle fiber, which soften the fiber.
TETANUS, CRAMP, FATIGUE
MUSCLE TISSUE, A SOURCE or HEAT AND ELECTRICITY
Thus far we have considered only one result of muscle action; namely, the production of motion. Muscle tissue is built up of food derived from the blood — contraction means a using up of its substance, and the formation of waste products. These chemical processes are going on continually, and all chemical action is ac- companied by the production of heat. A muscle in action is there- fore a machine for producing body heat, and since the muscular system comprises so large a portion of the human body (weighing nearly three times as much as the bones), it is one of the chief sources of heat; for the double reason that it includes a great deal of tissue, and that it is more constantly at work than any other tissue in the body.
We all know that the body temperature rises during muscular exercise; as the vessels dilate, bringing oxygen for chemical action, heat is rapidly evolved and waste is swept away. (Blood- and lymph vessels carry both food and waste.)
In addition to other results of muscle activity, a slight current of electricity is produced, appreciable only by certain experiments.
MODIFICATIONS OF MUSCLE ACTION
Clinical notes. — Tetanus is a condition of the muscles in which the contractions are so rapid that the action appears to be con- tinuous; the stimuli come so rapidly that the fibers cannot perfectly relax.
It may be due to various causes: to drugs, as strychnine; to bacterial poisoning through invasion of wounds ; or to disordered conditions of the nerve system. It may be voluntary in char- acter; when one deliberately stiffens the body or any portion of it the rigidity thus occurring is tetanic.
Cramp is sudden involuntary contraction of muscle-fiber, spasmodic in character and so violent as to be exceedingly painful.
Convulsive movements or convulsions (spasms) are due to invol- untary and forcible action of several muscles or groups of muscles. The movements vary with the number of muscles involved.
Fatigue of muscle tissue follows prolonged use, evidenced by sensations of pain in the muscles themselves, probably due to an accumulation of waste matters when the muscle is not quite equal
126
ANATOMY AND PHYSIOLOGY
to the demands made upon it; repair does not keep pace with wear and the muscle becomes not only tired from overwork and lack of food but burdened with the poisons of fatigue.
LARGE MUSCLES CLASSIFIED ACCORDING TO THEIR MOST FREQUENT ACTION
REGION.
TRUNK
HEAD
SHOULDER ARM. .
FOREARM .
ACTION.
To enclose cavities and aid in respiration
To separate cavities and aid in respiration
Floor of trunk and aiding above muscles. .
To move spine and trunk
To extend head.
To flex head. . . To rotate head.
To lift shoulder
To pull shoulder backward To pull shoulder forward. .
To pull arm forward
To pull arm backward
To abduct (lift) arm
To adduct (pull downward) To rotate arm, supination To rotate arm, pronation To flex forearm. .
To extend forearm. . . To rotate, supination.
MUSCLES.
To rotate, pronation.
Intercostals. Quadratus lumborum. Obliquus externus. Obliquus internus. Transversus. Rectus abdominis.
Diaphragm.
Levator ani.
Coccygeus.
Abdominal group.
Erector spinae.
Ilio-psoas.
Erector spinae.
Trapezius.
Sterno-mastoids.
Trapezius.
Sterno-mastoid.
Trapezius.
Trapezius.
Anterior serratus.
Pectorals.
Latissimus dorsi.
Deltoid.
Suprascapular.
Pectorals.
Latissimus dorsi.
Infraspinatus.
Teres minor.
Subscapularis.
Teres major.
Biceps brachii.
Brachialis.
Brachio-radialis.
Triceps.
Supinator.
Biceps brachii.
Brachio radialis.
Pronator teres.
Pronator quadratus.
ACTION OF MUSCLE GROUPS
127
LARGE MUSCLES CLASSIFIED ACCORDING TO THEIR MOST FREQUENT ACTION— (Continued)
REGION.
ACTION.
WRIST.
HAND.
To flex wrist
To extend wrist.
To flex fingers.
To extend fingers.
MUSCLES.
To flex thumb
To extend thumb . .
THIGH,
To flex thigh
To extend thigh
(also to extend trunk)
To rotate outward.
LEG..
To rotate inward. .
To abduct. . To adduct.. To flex leg..
ANKLE
To extend leg .
Rotation outward. Rotation inward. . To flex ankle. .
FOOT.
To extend ankle. . To flex toes. .
To extend toes.
Flexor carpi radialis. Flexor carpi ulnaris. Extensor carpi radialis
(long and short). Extensor carpi ulnaris. Flexor digitorum (sub-
lim.).
Flexor digitorum (pro- fund.). Extensor digitorum
(com.). Extensors of index and
little fingers Thenar group. Three extensors of
thumb. Ilio-psoas. Gluteus maximus. Biceps femoris. Semitendinosus. Semimembranosus. Glutei-med. and min. Sartorius. Four adductors. Two obturators. Gluteus min. Tensor fasciae latae. Adductor magnus (long
fibers of). Three glutei. Four adductors. Biceps femoris. Semitendinosus. Semimembranosus. Sartorius. Quadriceps femoris (rec-
tus and three vasti). Sartorius. Biceps. Tibialis ant. Peroneus tertius. Tibialis post. Peronei (long and short). Flexor digitorum
(longus).
Flexor pollicis (longus). Extensor digitorum
(longus). Extensor hallucis
(longus).
128 ANATOMY AND PHYSIOLOGY
SPINAL NERVE SUPPLY TO PRINCIPAL MUSCLE GROUPS
REGION.
SIDE OF NECK.
THORAX AND SHOULDER
MUSCLES.
NERVE.
ARM, ANTERIOR
ARM, POSTERIOR
FOREARM, POSTERIOR.
FOREARM, ANTERIOR.
HAND.
ABDOMEN AND PELVIS.
Three scaleni muscles. Elevator of angle of scapula
Intercostal. . .
Diaphragm
Sacro-spinalis (erector
spinae)
Latissimus dorsi
Supra- and infraspinatus. . Subscapularis.
Teres major
Teres minor
Deltoid. .
Pectoralis major and minor Biceps.
Coraco-brachialis
Brachialis. .
Triceps
Supinators and extensors of wrist
Extensors of fingers
Pronators and superficial flexors
Flexor carpi ulnaris and deep flexors
(The deep flexor of fingers has also a branch from median.)
Thenar eminence (muscles of thumb)
Hypothenar eminence (muscles of little finger) . .
Interossei
Rectus and pyramidalis.
Quadratus lumborum.
External and internal ob- lique.
Transversus.
Psoas and iliacus
Levator ani.
Perineal muscles
Piriformis
Gluteus maximus
Gluteus medius and mini- mus.
Tensor fasciae latae
Obturators, external and internal. .
Cervical branches of bra- chial plexus. Intercostal. Intercostal and phrenic.
Spinal.
Long subscapular.
Suprascapular .
Subscapular. Axillary.
Axillary and ant. tho- racic. Ant. oracic.
Musculo-cutaneous. Musculo-cutaneous and radial.
Radial (musculo-spiral). Deep branch of radial.
Median. Ulnar.
Ulnar and median.
Ulnar. Ulnar.
Thoracic and lumbar.
Pudic.
Sacral plexus. Inferior gluteal.
Superior gluteal. Obturator.
NERVES OF SKELETAL MUSCLES
I29
SPINAL NERVE SUPPLY TO PRINCIPAL MUSCLE GROUPS.—
(Continued)
REGION.
MUSCLES.
NERVE.
THIGH Three adductors.
Gracilis. .
THIGH, ANTERIOR Quadriceps.
rectus. two vasti. crureus. .
THIGH, POSTERIOR. LEG, ANTERIOR. . . .
LEG, LATERAL. . .
Biceps. Semitendinosus.
Semimembranosus
Anterior muscles (exten- sors)
Peroneuslongus andbrevis
LEG, POSTERIOR Calf muscles.
Deep muscles (flexors).. . . FOOT Dorsum
Plantar region
Obturator (sciatic to portion of ad. mag.).
Femoral (anterior crural).
Sciatic.
Deep peroneal (anterior
tibial). Superficial peroneal
(musculo-cutaneous) .
Tibial nerve. Deep peroneal. Medial and lateral plan- tar.
CHAPTER VIII THE ORGANS OF DIGESTION
MOUTH, PHARYNX, ESOPHAGUS, STOMACH, AND INTESTINES
These, with the glands which secrete the digestive fluids, con- stitute the digestive apparatus.
ir \Saliuary Gland
--Esophagus
Spleen
- Lacteals
Large Jntestine* • -
Vermiform Appendix- ~
FIG. 99. — GENERAL SCHEME OF THE DIGESTIVE TRACT, WITH THE CHIEF GLANDS OPENING INTO IT; TOGETHER WITH THE LACTEALS ARISING FROM THE INTESTINE AND JOINING THE THORACIC DUCT. — (Landois.)
The alimentary tract or canal is a series of channels included within the organs named, constituting a long tube of mucous
130
DIGESTIVE FLUIDS, ENZYMES 131
membrane through which the food passes. The glands which secrete the digestive fluids open into this tract.
The digestive fluid of the mouth is saliva.
The digestive fluid of the stomach is gastric juice.
The digestive fluids of the intestines are intestinal juice, and pancreatic juice (assisted by bile).
Each of these fluids contains one or more of the peculiar sub- stances called enzymes.
An enzyme is a ferment which by its presence causes certain changes in other substances.
The enzymes of the digestive fluids cause the chemical changes in food which are necessary for its digestion.
The glands are
Salivary, opening into the mouth. Peptic, " stomach.
Intestinal, " " intestines.
Pancreas, small intestine.
Liver, " small intestine.
The tongue, teeth and glands are appendages of the alimentary canal.
THE MOUTH
The mouth, or oral cavity, is enclosed partly by muscles and partly by bones. The muscles are the lip muscles in front, the buccinator at the sides, and the mylo-hyoid in the floor. The bones are the maxilla and the palate-bones above, and the mandible below.
The roof of the mouth is called the palate ; the bony portion is the hard palate; the muscular portion attached to it is the soft palate or the velum palati (veil of the palate) . In the middle of the soft palate is the uvula, which is a small projection downward. All of these bones and muscles are in pairs, right and left.
Surgical note. — If, owing to lack of development they are not joined in the middle line, cleft palate results. The cleft may be partial or complete, and the divided upper lip is called harelip.
The oral cavity is lined with mucous membrane which is always moist in health. The part of the cavity between the lips and the teeth is the vestibule.
The mouth contains the teeth and the tongue.
The teeth are already described.
The tongue lies in the floor of the mouth with its base curved downward at the back and attached to the hyoid bone. It is composed of muscles, and covered with mucous membrane which
132
ANATOMY AND PHYSIOLOGY
forms a special fold underneath the tip of the tongue connecting it with the floor; this fold is called the frenum lingua. When the frenum is short we say the tongue is "tied."
A little clip with the scissors is often sufficient to free it, but this is done with care as an artery runs forward very near the frenum.
Septum .
Nostril
Anterior naris
Hard palate
Anterior palatine
arch
Recess Posterior palatine
arch
Tongue
FIG. ioo. — THE ORAL CAVITY. — (Deaver.)
The dor sum, or superior surface of the tongue, is covered with small projections called papilla, of three sizes— the vallate, the largest, forming a V-shaped row at the back; the fungiform, next in size, scattered over the surface but most numerous at the tip and sides, and bright red in color; and the filiform, the smallest, cover- ing the anterior two-thirds of the dorsum and borders (Fig. 101).
The tongue aids in mastication and swallowing, or deglutition. It is also an important organ of speech and the principal organ of taste.
THE MOUTH
133
Note. — The perception of bitter substances is plainer in the posterior portion, while sweet, sour, and salty substances are more quickly recognized in the anterior part and at the borders. The nerves of taste are in the papillae.
Some elevations of mucous membrane on either side of the base of the tongue form the lingual tonsils. (These are seen only with the aid of the laryngoscope.). They contain lymphoid tissue.
Parotid gland
Masseter muscle
Floor of mouth and sub , ,
maxillary duct / \m — -Hyoidbone
Submaxillary gland
(main portion is drawn backward)
FIG. 10 1. — SALIVARY GLANDS AND PAPILLA OF TONGUE. — (Morris.)
The mouth opens at the back into the pharynx, through the passage called the isthmus of the fauces. This passage is bounded by two folds on each side running downward from the soft palate and called the palatine arches, or pillars of the fauces. B etween the anter- ior and posterior arch of either side is the palatine tonsil,1 a gland- like body the use of which is not clearly understood2 (Fig. 100).
It presents small openings upon its surface leading into recesses or crypts which are surrounded by the follicles of the tonsils.
Clinical note. — Follicular tonsillitis is an inflammation of the mucous membrane and follicles in the crypts.
lFaucial tonsil.
2 The student may see all of these structures by examining her own mouth with the aid of a hand-mirror and a good light.
134 ANATOMY AND PHYSIOLOGY
Salivary glands. — The digestive fluid of the mouth is called saliva. It is secreted by the salivary glands, three in number on each side — the parotid, submaxillary, and sublingual (Fig. 101).
The parotid gland is situated in front of and below the ear, and has a duct about two inches long (Stenson's duct) which runs forward to open into the mouth opposite the second molar tooth of the upper jaw, piercing the buccinator muscle. It secretes an abundant watery fluid.
The surface line of Stenson's duct is drawn from the lobe of the ear to the middle of the upper lip.
The submaxillary gland lies under the angle of the jaw, open- ing into the floor of the mouth close to the f renum, by Wharton ys duct. It secretes a thicker fluid than the parotid gland.
The sublingual gland lies in the (anterior) floor of the mouth and opens under the tongue near the frenum, by several small ducts. This also secretes a thicker fluid.
The fluid which is constantly present in the mouth and com- monly called saliva, is a mixture of the secretion of the salivary glands and the mucous glands of the mouth.
The reaction of the saliva is alkaline. The enzymes or ferments of saliva are ptyalin and maltase. The average daily quantity of mixed saliva is 1400 gm.
THE PHARYNX
The pharynx, or throat, receives the food from the mouth. It occupies a space in front of the spinal column from the base of the skull to the fifth cervical vertebra, its roof being formed by the body of the sphenoid bone, joined to the occipital. The walls of the pharynx consist of three pairs of muscles called the constrictors— upper, middle, and lower, strengthened by a fibrous layer and lined with mucous membrane.
The illustration shows that the constrictors are flat muscles attached at the sides to the structures in front of the pharynx. Thus, from above down- , ward, their origin is on the pterygoid process, a special ligament, the mandible, side of the tongue, hyoid bone, thyroid and cricoid cartilages. The fibers all join a fibrous line, or raphe, at the back, which is suspended from the base of the occipital bone. This is their insertion.
By due contraction of these muscles the food is grasped and pressed downward into the esophagus. They are composed of striated or voluntary muscle fibers.
OPENINGS OF PHARYNX
135
The upper part of the pharynx is behind the nose and is called the nasal part, ornaso-pharynx. The middle part is behind the mouth and is called the oral part, or oro-pharynx. (It is this part which we see when looking directly into the throat.) The lower part is behind the larynx and is called the laryngeal part, or the laryngo-pharynx.
The openings of the pharynx are seven in number: the two choana (posterior nares) communicating with the nose; the two
Orbic. oris muscle
Special ligament
Mylo-hyo'd muscle
TTvoid bon
Thyro-hyoid
membrane ;
Thyroid cartilage
Cricoid cartilage Trachea
Esophagus
FIG. 102. — THE PHARYNX. — (Holden.)
auditory (Eustachian) tubes communicating with the ears, and the isthmus of the fauces, communicating with the mouth. Below, it communicates with the larynx (the opening being guarded by the epiglottis) and opens into the esophagus.
The food passes through the oro-pharynx and laryngo-pharynx, the naso-pharynx being an air-passage.
In the roof of the pharynx is a small mass of lymphoid tissue called the pharyngeal tonsil. If hypertrophied it forms an adenoid tumor or "adenoid"
THE ESOPHAGUS
The esophagus (Figs. 102, 99) begins at the lower end of the pharynx and extends downward in the neck in front of the spinal
136
ANATOMY AND PHYSIOLOGY
column, to pass into the thorax. It finally comes forward in front of the aorta, passes through the diaphragm, and terminates in the stomach. It is a tube about nine inches long, having two layers of muscles (circular within, longitudinal without) and lined
JJ
FIG. 103. — SHOWING SITUATION OF PHARYNX BEHIND NOSE, MOUTH, AND LARYNX
— (From Dealer's "Surgical Anatomy .")
a,~b, c, dj e, Turbinal bones and meatuses of the nose; g.i, tongue; h, posterior palatine arch; y, anterior palatine arch; k, hyoid bone;.;, mylo-hyoid muscle (floor of mouth); m, thyro-hyoid membrane; n, ventricle of larynx; p, q. r, sphenoid bone and sphenoidal sinus; v, hard palate; w, soft palate; x, uvula; z, tonsil; t, naso-pharynx; u, orifice of auditory tube; aa, oro-pharynx; dd, laryngo-pharynx; bb, epiglottis; ee, upper portion of larynx; gg, vocal bands; /, false vocal bands; hh, lower part of larynx; ii, cricoid cartilage; jj, trachea.
with mucous membrane. By contraction of the different muscles from above downward the food is passed along to the stomach.
The esophagus lies at first immediately behind the trachea. The upper part is composed of striated, or voluntary muscle like that of the pharynx; in the lower part the muscle is non-striated, or involuntary, like the stomach.
THE STOMACH 137
At the termination in the stomach, the circular fibers are most numerous, forming the cardiac sphincter which prevents the return of stomach contents.
The remaining organs of digestion are contained in the ab- dominal cavity, which is lined with a serous sac or membrane called peritoneum (see p. 367). These organs are developed from an original straight tube behind the peritoneum. Therefore, as they grow, they press forward against it and get a covering which is called their serous layer. Their muscular coats are all involuntary or unstriped muscle.
THE STOMACH
The stomach (gaster, Fig. 104) is in the epigastric region of the abdomen just below the diaphragm. Shape and size: like a curved flask, ten to twelve inches long and six to eight wide at the larger end, which is turned toward the left side. Average capacity: five pints in distention; two pints when moderately filled.
The stomach has two surfaces, two borders, two orifices and two extremities — cardiac and pyloric, with a pre-pyloric part between them.
The surfaces are the anterior — looking slightly upward; and the posterior — looking slightly downward.
The borders are usually called curvatures; the upper border is the lesser curvature (about five inches in length) ; the lower border is the greater curvature (about twenty inches in length) .
The left extremity is the expanded portion called ihefundus of the stomach (also the greater cul-de-sac) , and the cardiac end (from its nearness to the heart).
The right extremity is called the pyloric extremity. It is just below the liver.
The orifices are at the extremities. At the left is the esopha- geal orifice, guarded by the sphincter of the cardia; at the right is the pyloric orifice, guarded by the sphincter of the pylorus or "gate-keeper."
The coats or tunics of the stomach are four in number— mucous, submucous, muscular, and serous.
The mucous layer, or mucosa, is the innermost layer. It is pink in color but becomes bright red when food is present, from the increased blood-supply necessary for digestion. It lies in folds, or
138
ANATOMY AND PHYSIOLOGY
rugae, running from one extremity to the other — the longitudinal folds. This layer contains the gastric glands which secrete the gastric juice and pour it through their ducts into the stomach.
The submucous layer or submucosa is a network of connective tissue next to the mucous coat. It bears fine vessels, nerves and lymphatics, and connects the mucous and muscular tunics together loosely, so that when the stomach is distended the longitudinal folds simply disappear, without injury to the mucous membrane.
The muscular coat (or tunic] comprises three layers of non- striated muscle: internal, middle and external. The internal layer
Aorta
CeLac artery
Gastric artery
FIG. 104. — THE STOMACH AND SPLEEN. — (Morris.}
consists of oblique fibers (it is a thin layer and is mostly con- fined to the cardiac portion). The middle layer is a complete layer of circular fibers. They are most numerous at the ex- tremities of the stomach, where they form two ring-shaped bundles. One is the sphincter of the cardia, surrounding the lower end of the esophagus and the cardiac orifice of the stomach; the other is the sphincter of the pylorus, which is a strong ring-muscle diminishing the size of the pyloric orifice so that it is the narrowest portion of the alimentary tract (a half-inch, or 3 mm.). The ex- ternal layer consists of longitudinal fibers (fibers running length-
THE INTESTINE
139
wise) which are continued from the similar layer of the esophagus, and pass on to those of the intestine.
The serous coat (or tunic) is a portion of the great serous mem- brane of the abdomen, called the peritoneum (page 367). The two surfaces of the stomach are covered by different layers of per- itoneum which will be described elsewhere (Fig. in and p. 148).
The gastric glands are embedded in the mucosa. They are tubular in form, microscopic in size, and very numerous (their number is estimated at 5,000,000). They differ markedly in the two portions of the stomach. The cardiac glands secrete the diges- tive ferments, pepsin and rennin, while the pyloric glands secrete mucus also (Fig. 105).
The reaction of the gastric juice is acid (owing to hydrochloric acid). This acid is a natural but not a powerful antiseptic.
The position of the stomach is oblique, the pyloric end being on a lower level than the cardiac. It is also the movable end.
The location of the stomach is mostly in the epigastric region (Fig. 235). It is below the portion of the diaphragm which supports the heart; behind it are the largest artery and vein in the body — the aorta and the inferior vena cava. The pyloric end ex- tends under the liver in the right hypochondrium, while the cardiac end is in contact with the spleen in the left hypochondrium.
Clinical notes. — When the stomach is empty it tends to a vertical position when filled, it swings upward and forward to become again oblique. If much distended, as with gas, it embarrasses the action of the heart by pressure.
The infant's stomach is nearly or quite vertical and easily overflows; its capacity at birth is one ounce, reaching two ounces at about the end of a fortnight and eight ounces at ten or eleven months.
THE INTESTINE
The intestine or bowel begins at the pyloric orifice of the stomach and continues to the end of the alimentary tract. It is from twenty-five to thirty feet in length (Fig. 106).
FIG. 105. — SECTION OF PYLORIC GLANDS FROM HUMAN STOMACH. a. Mouth of gland leading into long, wide duct (&), into which open the terminal divi- sions, c. Connective tissue of the mucosa. — (After Pier sol.)
140
ANATOMY AND PHYSIOLOGY
Like the stomach, it is composed of four coats or tunics — mucous, submucous, muscular and serous.
The mucous coat is the glandular coat; that is, the glands which secrete intestinal juice are imbedded in the mucous coat, and their ducts open on its surface.
Vessels | of large intestine |
Cecum
Appendix
FIG. 106. — THE INTESTINES. — (Morris.) Large intestine thrown upward, small intestine drawn to left.
In addition, small gland-like bodies of lymphoid structure are scattered throughout this coat. They have no ducts. They are probably lymph nodules — the so-called solitary glands.
The submucous coat bears the fine vessels and nerves which supply the mucous coat. It connects the mucous and muscular coats together.
THE SMALL INTESTINE 141
The muscular coat comprises two layers (like the esophagus), an inner layer of circular fibers, an outer one of longitudinal fibers.
The intestine is divided into the following parts:
Duodenum f Cecum
( Ascending
Small intestine Jejunum Large intestine { Colon Transverse
( Descending
Ileum I Rectum
The Small Intestine
The small intestine is about twenty feet in length, and about two inches wide in its upper (widest) part. It extends from the stomach to the colon, beginning with the pyloric sphincter in the right hypochondrium and ending with the ileo-colic sphincter in the right iliac region.
The mucous coat of the small intestine forms circular folds (old name, valvulae conniventes) which are permanent, that is, they never disappear however widely the bowel may be distended. They serve to increase the area of mucous membrane for purposes of digestion and absorption (Fig. 108). This layer contains the intestinal glands.
The entire mucous coat is covered with tiny projections hair- like in. size (from 1/2 to i mm. long) called villi, which give it a velvety appearance (Fig. 107).
The villi are absorbing structures or absorbents. (They may be demonstrated in a good light by laying a piece of intestinal wall in a shallow tray of clear water; the water will float their free extremities.)
In the midst of each villus is a minute lymph capillary, surrounded by a fine network of blood-vessels and lymph spaces, the whole covered by a layer of the special epithelium of the intestine. Lymph vessels of villi are called lacteals because during digestion they contain a milky-looking fluid.
The muscular coat is in two layers — circular within, longitudinal without — pretty evenly distributed.
The serous coat covers all except a portion of the first division (see duodenum).
The duodenum is the first division of the small intestine
142
ANATOMY AND PHYSIOLOGY
(Fig. 109). It begins at the pyloric end of the stomach and is about ten inches long; curves upward, backward, to the right and downward, and then continues across to the left side of the
spinal column.
About four inches from the pylorus the mucosa presents an elevation — the bile papilla, where the common bile and pancreatic duct opens.
The circular folds of the mucous coat begin in the lower portion and are unusually large.
FIG. 107. — SECTION OF INJECTED SMALL FIG. 108. — CIRCULAR FOLD OR VAL-
INTESTINE OF CAT. VUL.E CONNIVENTES. — (Brinton.)
a, b. Mucosa. g. Villi. i. Their absorbent vessels, h. Simple follicles, c. Muscularis mucpsae. j. Submucosa. g£. Circular and longitudinal layers of muscle. /. Fibrous coat. All the dark lines represent blood- vessels filled with the injection mass. — (Piersol)
Note. — The inferior part of the duodenum is behind the peritoneum, this part has no serous coat.
The jejunum is the second division of the small intestine— so named because it is found empty. It possesses all of the char- acteristic structures: villi, circular folds, intestinal and solitary glands. It lies in the umbilical and the two lumbar regions.
The ileum is the third division of the small intestine — so named because of its frequent twisting. There is no definite
THE ILEUM
143
separation between the end of the jejunum and the beginning of the ileum.
The mill and circular folds are all found throughout the ileum.
The ileum ends in the right iliac region by opening into the large intestine. This orifice is doubly guarded; first, by two folds of mucous membrane strengthened by fibrous tissue, called the ileo-cecal valve; second, by a circular muscle called the ileo-colic sphincter; this is the more important of the two.
13
277
FIG. 109. — LIVER, PANCREAS, DUODENUM, SPLEEN AND KIDNEYS, i, 2, 3. Duodenum. 4, 4, 5, 6, 7, 7, 8. Pancreas and pancreatic ducts. 9, 10, n, 12, 13. Liver. 14. Gall bladder. 15. Hepatic duct. * 16. Cystic duct. 17. Common duct. 18. Portal vein. 19. Branch from the celiac axis. 20. Hepatic artery. 21. Coronary artery of the stomach. 22. Cardiac portion of the stomach. 23. Splenic artery. 24. Spleen. 25. Left kidney. 26. Right kidney. Section of pancreas to show ducts. Liver turned upward and stomach removed to show duodenum. — (Sappey.)
The secreting glands of the small intestine are embedded in the mucosa, and are found in every part. They are called the in- testinal glands or intestinal foLicles, or glands of Lieberkuhn. They are tubular in shape, and secrete the greater portion of the so-called intestinal juice. The ferments of the glands are erep- sin, iwuertase, maltase, etc. The reaction of the fluids is alkaline.
In addition to the above, there are small round bodies called solitary glands. They increase in size in the lower end of the ileum where they are grouped in oblong patches — the Peyer's
144 ANATOMY AND PHYSIOLOGY
patches (or agminated glands) the largest of which may measure three inches in length.
Clinical note. — The solitary glands (more especially the Peyer's patches) become inflamed and ulcerated in typhoid fever.
The Large Intestine
The large intestine is about five feet long and two and one-half inches wide in the widest part. It begins where the small intestine ends (in the right iliac region) , ascends through the right lumbar, crosses the abdomen in front of the small intestine, descends to the left iliac region, and thence down through the pelvis, ending in front of the coccyx. (See Regions of the Abdomen, p. 366.)
The mucous coat is smooth and rather pale. No folds are present, and no villi, but the solitary and tubular glands are numerous, like those of the small intestine.
The circular fibers of the muscular coat are evenly distributed, but the longitudinal fibers of the cecum and colon are arranged in three bands, placed at even distances apart. These bands are shorter than the tube itself, therefore they gather it into puffs which give the bowel a sacculated appearance. By this, the large bowel may be recognized at once, even should it be really small in actual size in some portion of its extent.
The serous coat covers the greater part of the large intestine; the exceptions will be noted later. (See p. 146, Surgical Note, The Rectum.)
The four divisions of the large intestine are the cecum, the colon, the sigmoid loop, and the rectum (Figs. 106, no).
The cecum, or first division , is a short pouch hanging below the level of the ileocolic valve and presenting the opening of the appen- dix vermiformis or appendix ceci. The three longitudinal bands of the muscular coat meet at the base of the appendix, which is a small tube three or four inches long, attached to the posterior wall of the cecum. It often turns upward, quite as often downward, and may lie transversely. It has all four coats, with intestinal and solitary glands, but is of no use.
Clinical note. — Owing to its small size any substance which enters the appendix is apt to be retained, and if it is of an injurious character it will cause appendicitis. This disease is more often caused by the action of
THE COLON
145
Small intestinal worms
harmful bacteria than the celebrated cherry-stone. have been found within the appendix.
The ilio-cecal valve consists of two folds of mucous membrane with muscle fibers between the layers. They are placed at the end
FIG. no. — THE LARGE INTESTINE.
The small intestine and its vessels are drawn to the right to show the sigmoid colon and the rectum. The transverse colon is thrown upward. — {Morris.)
of the ilium where it opens into the colon, and project toward each other, leaving only a slit-like passage.
The colon begins at the ilio-cecal valve. The first part, or ascending colon, passes upward in the right lumbar region. After making a bend under the liver — the right colic flexure (or hepatic flexure), it becomes the transverse colon, which hangs in a loop across the abdomen in front of the small intestine. Another bend occurs under the spleen, the left colic flexure (or splenic flexure) ; thence the descending colon passes downward in the left lumbar region to the left iliac fossa. Here it makes an S-shaped or sigmoid bend
146 ANATOMY AND PHYSIOLOGY
and becomes the so-called sigmoid colon. It then enters the pelvis to become the rectum.
Surgical note. — The ascending colon lies so close to the posterior abdominal wall that there is no peritoneum behind it, and the descending colon also is bare in a narrow strip at the back, consequently the surgeon may take advantage of this condition to open the colon without wounding the peritoneum, in the operation called lumbo-colotomy.
The rectum is about five to seven inches long, very distensible, and so called because it has no convolutions, but simply follows the curve of the pelvic wall, lying in front of the sacrum and coccyx. In the last inch or inch and a half it bends backward (perineal flexure) to pass the tip of the coccyx. This is the anal canal, and it ends at the opening called the anus (Fig. no).
The portion above the anal canal is the widest part — the rectal pouch.
The mucous membrane of the rectum is red, and usually pre- sents two or three special folds about two or three inches above the anus, called the rectal folds, or Houston's valves.
The largest, a permanent fold, is on the right side about two and one-half inches above the anus and called the third sphincter. Two smaller ones, not permanent, are on the left side, above and below the former.
The muscular coat has the two layers, circular and longitudinal. The peritoneal coat covers the front and sides of the upper part only.
The reaction of the fluids in the large intestine is alkaline.
Sphincters of the anus. — The circular fibers around the anal canal form the internal sphincter.
The external sphincter is a flat circular muscle just under the skin around the anus. (Its contraction causes the radiating lines in the skin.) The function of the sphincters is to guard and control the anus.
Clinical note. — The point of a syringe should be passed in an upward and forward direction through the anal canal, and then turned backward,
RESUME.
The alimentary tract begins with the mouth and ends with the large in- testine, passing through the head, neck, thorax, and pelvis. It is practically a long tube of mucous membrane surrounded by layers of muscle and held to them by connective tissue. The mucous membrane contains glands which secrete the digestive fluids. The muscle layers pass the food along, that it may be acted upon in all portions of the tract; and wherever free motion accom-
THE MESENTERY
panics the digestion of the food, a serous layer is added outside of all to prevent friction.
The digestive fluid of the stomach is acid; in all other parts it is alkaline.
Peristalsis is the name given to the peculiar motion of the stomach and intestine during the passage of their contents. The circular fibers compress the food and at the same time the longi- tudinal fibers shorten the tube. This action goes on from above downward, causing a sort of worm-like movement which is de- scribed as peristalsis, or peristaltic movement.
Liver
Gastro-hepatic omentum Stomach
Transverse colon
M esentery
Small intestine
Uterus
Epiploic foramen Pancreas
Duodenum
Transverse meso-colon Aorta
Rectum
Bladder
FIG. in — DIAGRAM OF A SAGITTAL SECTION or THE TRUNK, SHOWING THE RELA- TIONS OF THE PERITONEUM. — (Allen Thompson.}
The mesentery is the fold of peritoneum which holds the jejunum and ileum in place. This fold leaves the posterior ab- dominal wall at a line inclining downward to the right, about five or six inches long; but it includes twenty feet of intestine, and therefore it is like a very full ruffle twenty feet in length with a band of six inches. The vessels and nerves of the intestine lie between the layers of the mesenteric fold.
Any fold of peritoneum which connects a portion of intestine to the wall of the trunk is a mesentery. The meso-colon connects the colon with the abdom-
148 ANATOMY AND PHYSIOLOGY
inal wall; the meso-rectum connects the rectum with the pelvic wall; the large mesentery holds the ileum and jejunum to the posterior abdominal wall.
An omentum is a fold of peritoneum connected with the stomach. The greater omentum hangs from the greater curvature; the lesser omentum connects the lesser curvature with the liver (being called the gastrohepatic omentum); and the gastro splenic omentum connects the stomach and spleen. (Two layers of peritoneum pass from the under surface of the liver to the lesser curvature of the stomach, forming the lesser omentum. They then separate to enclose the surfaces of the stomach, making its serous coat. They come together again at the greater curvature and hang down in the shape of a large serous sac with double walls, the greater omentum, which hangs in front of the small intestine.)
Note. — The transverse meso-colon usually becomes adherent to the greater omentum (Fig. 112).
THE PANCREAS
The pancreas (Figs. 109, no) is a racemose gland, behind and below the stomach. It is about seven inches long and somewhat resembles a hammer in shape, the head being turned to the right and lying within the curve of the duodenum, the body crossing to the left, and the tail reaching the spleen. It consists of lobules, each with its duct; these unite to form the pancreatic duct which conveys the pancreatic fluid to the duodenum. The duct opens (with the common bile duct) into the duodenum about four inches from the pylorus (guarded by a valve) .
The three pancreatic ferments are amylopsin, trypsin and steapsin (for starchy proteid and fat) (see page 161).
THE LIVER
The liver (Fig. 112) is the largest abdominal organ, and the largest gland in the body. Its normal weight is between three and four pounds (1300 to 1700 grams). It is underneath the dia- phragm, in the right upper portion of the abdomen, the thin left lobe extending across the epigastric region above the stomach. Its general shape is that of a wedge, much thicker at the right side than the left, and with the thin edge turned forward. The upper surface is convex, and marked off by a ligament into two lobes, right and left. The lower surface is divided by five fissures into five lobes. The largest fissure is the transverse, the porta (or gate) for the passage of vessels,1 nerves and ducts.
1 Lymph vessels and hepatic artery. Hepatic veins take a different route.
THE LIVER
149
The substance of the interior of the liver is composed of hepatic cells, grouped in lobules, with a multitude of blood-vessels, lym- phatics and nerves, supported by connective tissue.
FIG. 112. — THE ABDOMINAL ORGANS. — (Gerrish, after Testut.) The liver is turned upward to show the inferior surface with the gall-bladder. The vessels entering and leaving the porta are also seen, the lesser omentum having been removed.
An hepatic lobule measures only about a millimeter (£s of an inch) in width. Between its cells there is a fine network of hepatic and portal blood- vessels, and lymph spaces; also bile passages. The blood-vessels empty into hepatic veins; the lymph spaces form lymph vessels, and the bile passages lead to small bile ducts which unite and reunite to form the hepatic ducts.
150 . ANATOMY AND PHYSIOLOGY
Five ligaments of the liver hold it in place attaching it to the diaphragm and abdominal wall — the round, the broad, the coronary, and two lateral.
The round ligament is a cord (the remains of the umbilical vein) inclosed in the broad, which, with the lateral and coronary, is of peritoneum. It is the broad ligament which connects the superior surface of the liver with the diaphragm and is therefore called the suspensory ligament. It also marks off the right from the left lobe on that surface. The principal support of the liver is by its connection with the diaphragm.
The liver secretes a yellow alkaline fluid called bile which is conveyed through the porta by two ducts, the right hepatic and left hepatic; these unite to form one, the hepatic duct proper, which is soon joined by the cystic duct from the gall-bladder.
The gall-bladder occupies a fissure on the inferior surface of the liver. It is a pear-shaped sac three or four inches long, of fibrous tissue and muscle fibers lined with mucous membrane and partially covered with peritoneum. It contains a variable quan- tity of bile (or "gall") in reserve. The only opening of the gall-bladder is for the cystic duct, which joins the hepatic to form the common bile-duct, or ductus communis choledochus (Figs. 109, 112).
Bile, as it flows from the gall-bladder, is a thick or viscid yellow fluid having sometimes a brown tinge, or it may be greenish. It is formed as a thin fluid in the cells of the hepatic lobules, from materials brought in the portal vein (which enters the liver at the porta). (See page 148.)
Its characteristic elements are bile salts, bile pigment, and cholesterol — a substance which is soluble only in normal bile. Any of these may be found in gall-stones; this is especially true of cholesterol.
Bile is discharged from the liver by the right and left hepatic ducts, thence into the hepatic duct proper, and the common bile duel or ductus communis choledochus, as already stated.
Note. — The production of bile is continuous; its flow into the intestine is intermittent. It appears in the duodenum only during the process of digestion; in the interval it is stored in the gall- bladder.
Notes. — The cystic duct is about i 1/2 inches long; the hepatic
THE SPLEEN 151
duct, 2 inches long; the common duct, 3 inches long. Just before it opens into the duodenum, the common duct expands into a little pouch called the ampulla of Vater. A gall stone may lodge in this place.
Clinical notes. — The liver is pressed downward by the movement (con- traction) of the diaphragm in inspiration, and can then be felt below the costal arch in front. During expiration it sJips upward with the rise of the diaphragm.
Gall stones may form in the gall-bladder or in any of the ducts. If in the gall-bladder they may exist for a long time without causing symptoms, the bile flowing into the intestine without obstruction; if in the cystic duct the symptoms are also deferred, but if in either the hepatic duct or the ductus communis, obstruction to the outflow promptly causes jaundice and other disorders, with distention of the gall-bladder. Inflammation of the gall- bladder is Cholecystitis, of the liver — hepatitis.
The mscidily of the bile is increased in inflammation of the gall-bladder and often clogs the ducts to the point of obstruction, as in jaundice.
THE SPLEEN
Although there are reasons for including the spleen in the list of duct- less glands it is decided to include the description of this organ in the present connection. It is a very important organ with a remarkably free blood supply, which suggests great activity for some purpose or purposes, and the only direct connection of the spleen with any other organ is by blood-vessels with the liver, but the significance of this is a matter of con- jecture at the present time.
The spleen (or lien) is situated at the left of the stomach, directly beneath the diaphragm by which it is entirely covered. It is oval in shape, convex on the lateral surface and concave on the medial, where a depression called the hilus is seen for the passage of vessels and nerves (Fig. 109).
The fibromuscular capsule which forms the surface of the spleen sends numerous septa into the interior, and within the spaces of the network thus formed the splenic pulp, is contained. This consists of blood which has escaped from the open terminals of numberless capillaries, of lymphoid cells and broken down red cells, coloring matter and particles of waste. Small col- lections of lymphoid cells around the capillaries may be seen upon section of the organ; they are the Malpighian bodies of the spleen; their function is obscure.
The splenic artery is the largest branch of the celiac axis and the consequent large blood supply gives a dark red color to the
152 ANATOMY AND PHYSIOLOGY
spleen. The peritoneal covering completely surrounds it, except to allow vessels and nerves to pass through the hilus.
The function of the spleen is not well understood, as both animals and human beings have been known to live in health after its removal, but its structure and the study of the blood of the splenic artery and splenic vein reveal the following facts:
The spleen pulp contains a vast number of white cells (chiefly lymphocytes) and many disintegrating red cells. It has a high percentage of iron, especially after chronic diseases. The blood in the vein which leaves it contains many more white cells than that in the artery which enters; also — many small red cells are present, some of which are still nucleated (newly formed). Two enzymes are found — one a uric-acid-forming enzyme.
From these observations the conclusions suggested are that the spleen gives birth to leucocytes; that it stores and works over the iron from broken-down tissues (including red cells); that it may assist to form red cells and that it forms uric acid from broken- down protein substances.
Clinical notes. — The elasticity of the capsule allows frequent variations in size, which in health are normal; it is always larger during digestion and smaller in fasting. In certain diseased conditions it is much increased in size, as in malaria; and notably in leukemia, which is characterized by an enormous increase in the number of white cells in the blood, as well as in the size of the organ itself. The significance of these variations in size is not yet explained.
CHAPTER IX
PHYSIOLOGY OF THE DIGESTIVE ORGANS. FOODS, DIGESTION, ABSORPTION
FOODS
The human body is a machine constantly in motion; therefore, its cells continually use up their force, and continually need renew- ing. The material for this renewal is supplied by the food which we eat. Substances classed as foods must be able to "repair waste and provide the raw materials for growth. All substances which have this power are foods. . . . Thus, water salts and oxygen are true foods" (Mathews). As the various parts of the body are composed of quite different tissues, so the food is of a mixed character.
The composition of the tissues includes four classes of food principles, as follows:
1. Proteins. 1
2. Carbohydrates (sugars and starches). \ organic.
3. Fats.
4. Mineral salts including water. inorganic. In the body :—
1. Proteins are found in all tissues, but most abundantly in — blood, as serum-albumin, fibrinogen, hemoglobin; lymph, as serum- albumin; muscles, as myosinogin; milk, as caseinogen.
2. Carbohydrates (sugars and starches) are found principally in — blood, as dextrose; liver and muscles, as glycogen;1 milk as lactose.
3. Fats are found principally in — milk, as an emulsion; nerves, lymph, blood cells; bones, a? marrow; subcutaneous fascia and adipose tissue around organs.
4. Mineral salts are found in all tissues and fluids of the body;
1 Glycogen is an animal starch formed within the body, the others are sugars. Dextrose, grape sugar and glucose have the same composition.
153
154 ANATOMY AND PHYSIOLOGY
in — bones and teeth especially, as lime salts; muscles, nerves, and blood, as potassium salts; all tissues, as sodium salts; red blood cells, as iron.
In the food :—
1. Proteins exist in — meats, as myosin and albumin; eggs, as albumin in the white, lecithin in the yolk; grains, as gluten; vegetables: peas, beans, corn, etc., as vegetable albumin.
2. Carbohydrates (sugars and starches) exist in — fruits, as dextrose and levulose; milk, as lactose; sugar cane, beets, etc., as cane sugar and saccharose; vegetables: peas, beans, potatoes, etc., as starch.
3. Fats exist in — milk, as an emulsion; corn, oats and other grains; eggs (the yolk) and all animal foods in varying quantities.
4. Mineral salts exist in — all foods (but must be added in bulk) ; water, the most important; vegetable, grains and protein foods, as phosphate of calcium ; meats and all animal food, as iron ; all foods, as sodium chloride or common salt.
Proteins must be supplied to all tissues; they are the tissue builders.
Carbohydrates (or sugars and starches) are utilized by liver and muscle, and are sources of heat and muscle energy.
Fats are needed for the marrow of bones, as protective cover- ings, and to fill in spaces between organs; also to preserve body heat as well as to produce it.
Mineral salts are necessary to life.
Water constitutes nearly three-fourths of the body weight, and is universally present, even in the hardest tissues, as the enamel of teeth. Its most important uses are: i. To hold in solution the nutritive principles of the food, that they may be absorbed. 2. To sweep away waste matters to organs which can secrete them. 3. To aid in regulating the temperature of the body.
Sodium chloride stands next in importance to water. It is necessary to the normal activities of the tissues. It contributes to the formation of hydrochloric acid for gastric juice.
Phosphate of calcium is needed by bones and teeth; it is the most abundant salt in the body, next to water.
Calcium is indispensable to normal blood.
Iron is a necessary element of red blood cells, in hemoglobin.
FOODS 155
Elements of Organic Food. — Sugar, starch and fat consist of carbon, hydrogen and oxygen (CHO). The proteins add nitrogen (CHNO) and a little sulphur (CHNOS). (The formula? are omit- ted, the symbols being sufficient for our purpose.) These ele- ments are all furnished in suitable quantities by the food as described, except oxygen. This is obtained in great measure from the air we breathe which consists of nitrogen and oxygen. Nitrogen simply dilutes the oxygen, being itself inactive in this combination.
In accordance with the definition of food given at the beginning of this chapter, we regard atmospheric air as an important source of food, since it provides the essential element oxygen, which constitutes about one fifth of the bulk of the air we breathe (see page 231). It passes from the lungs into the blood and is carried by the red cells to the tissues at large.
With the exception of oxygen (which is introduced through the lungs), food enters the system through the alimentary tract, being here prepared for the uses for which it is designed, by the process of digestion.
Different articles of food should be combined in such ways as to secure proper adjustment of food principles to body needs.
For example: with meats, vegetables should be served rather than milk or eggs.
Avoid a number of starchy vegetables in the same meal. For example: to potatoes, or rice, or hominy, add green vegetables, as string-beans, spinach, celery, etc.
There is good reason for adding butter to bread and oil to salad, as neither flour nor green things contain fat.
Milk is well combined with starchy food, having within itself both proteins and fat. Eggs can take the place of meat to a large extent; they may be combined with milk.
The shell or husk of grain contains certain mineral salts which are about our only source of silica for the hair and teeth; therefore — give whole grains to growing children.
Whole-wheat flour, and ripe beans or peas, contain protein in a vegetable form; ripe corn (cornmeat) contains more fat than other cereals, and protein as well.
All vegetables contain a varying amount of fiber which is indigestible, but which is beneficial, since it serves to prevent the
156 ANATOMY AND PHYSIOLOGY
concentration of waste matters in too small bulk for the action of the large intestine. Three reasons for cooking food are as follows:
Cooked starch is more easily digested than raw, for the following reasons: The change of starch into sugar requires that it should first be hydrated, that is, combined with water. It exists in gran- ules and each granule of starch has a covering of cellulose which is, in saliva, indigestible. In the process of cooking, the boiling water penetrates to the granule, uniting with it and causing it to free itself from the envelope. At once it can be acted upon by ptyalin if in the mouth, or amylopsin if in the small intestine. With raw starch, hydration goes on slowly or not at all. Imper- fectly cooked starch is unwholesome for the same reason.
Vegetables also should be thoroughly cooked both on account of the starch which they contain, and the fibrous material, which needs partial disintegration by heat.
Meats are more easily digested if cooked long enough to soften their connective tissue fibers. By heat these are converted into a gelatinous substance which can be disposed of by pepsin and trypsin.
Another advantage secured by the cooking of food, lies in the effect of the flavors thus developed, by means of which appetite is encouraged and the secretion of digestive fluids is stimulated.
Clinical note. — The "scraped beef sandwich, " so of ten ordered for patients, contains the substance of the muscle cell alone, which has been scraped away from the connective tissue fiber; it is easily digestible because it may at once be converted into peptone without the necessity for first digesting the tougher covering.
DIGESTION
Digestion is the process of so changing the food in the alimentary canal that its nutritive parts may be absorbed into the system.
The organs described in Chapter VIII are so connected and arranged that they receive and act in consecutive order upon the food, causing a series of changes which result in separating nutri- ment from waste and preparing it for absorption, expelling the waste from the system.
The process of digestion begins in the mouth and continues throughout the small intestine. The food is first divided into
DIGESTION 157
small pieces by means of the teeth. This is mastication. At the same time it is mixed with saliva; this is hydration and insalivation.
By the act of swallowing, the softened mass is passed into the pharynx and down through the esophagus to the stomach. This is deglutition. (The soft palate prevents it from going upward to the nose, and the epiglottis prevents it from entering the larynx.)
The stomach now takes charge. The mass is compressed and moved about by the layers of the muscular coat until it is thor- oughly saturated with gastric juice, and becomes a pale yellowish fluid called chyme. As fast as this is accomplished, the pylorus, or gate-keeper, allows it to go through into the duodenum, where it meets the intestinal and pancreatic juices, and bile.
Continuing through the small intestine it loses in increasing measure its fluid and nutritious portions, and in the large intes- tine it is still further reduced to waste alone, which is expelled from the body.
Mechanical Processes of Digestion
The passage of food through the several organs, as above outlined, represents the sum of the mechanical processes resulting from the peristaltic action of the muscles of the tract, which are al- ready described as consisting of layers of circular and longitudinal fibers surrounding the tube of mucous membrane. In addition to these, there is an entirely different set — the muscles of masti- cation, which move the mandible or lower jaw, and keep the food between the upper and lower teeth. Their action constitutes the first mechanical process of digestion; this is of great importance, because only when the food is in small fragments (or masticated) can the digestive juices have access to the whole mass.
Chemical Processes of Digestion
The first occurrence which follows the introduction of food is an increased flow of blood to the part and activity of the secreting cells as the food arrives, beginning with the secretion of saliva. In fact, the cells may begin to work beforehand, being stimulated by the thought of food. This is true of both saliva and gastric juice.
The chemical process of digestion is brought about by the action of digestive fluids in the mouth, stomach and
158 ANATOMY AND PHYSIOLOGY
intestines — or saliva, gastric juice, and intestinal fluids; it is greatly facilitated by the presence of enzymes in the fluids. En- zymes are organic substances which are the result of cell ac- tivity. Their composition is undetermined; we know them only by their works. The characteristic which makes them valu- able is their power to stimulate rapid changes in certain other substances by their presence alone, while they themselves remain unchanged. In this way, the smallest quantity of an enzyme may effect changes in a large amount of material. (See p. 165.)
In the mouth the mechanical process includes mastication and insalivation. By the teeth the food is divided, then crushed and ground; at the same time it is softened by saliva. The parotid saliva does most of this, being the most abundant; it is poured into the mouth just outside the upper second molar and thus it mixes at once with the mass as it is crushed and ground. Sub- maxillary and sublingual saliva contain much more mucin and lubricate as well as soften the food. The saliva also dissolves the sapid substances, in order that the nerves of taste in the tongue may appreciate them. One can neither taste nor swallow a per- fectly dry substance.
In the mouth the chemical process is the conversion of starch into sugar. The digestive fluid is saliva; the two enzymes are ptyalin (salivary diastase) and maltase. Ptyalin does most of the work — changing the starch molecule first into dextrin and then into maltose (and a little dextrose) . Not all the starch taken at one time is digested in the mouth for the reason that it leaves the mouth too soon. (If it is retained in the mouth for some time, especially if mastication be continued, the presence of the sugar thus formed will be evident to the taste.)
The digestion of starch requires an alkaline medium; ptyalin cannot act in acid fluids.
Saliva is alkaline.
Being masticated, insalivated and hydrolyzed (see p. 166), the food is now prepared for deglutition or swallowing, by which it is passed through the pharynx and esophagus into the stomach. The tongue presses against the hard palate, thus giving the bolus (as the prepared mass is called) an impulse toward the isthmus of the fauces; as it passes through this space the upper pharyngeal constrictor muscle grasps it and passes it on — then the middle and
GASTRIC DIGESTION 159
the lower constrictors in turn — and it enters the esophagus. (Meanwhile the soft palate has prevented it from going upward and the epiglottis from entering the larynx.)
The muscles of the pharynx and upper esophagus, although striped, are not absolutely under the control of the will; we may or may not choose to swallow, but once begun the act completes itself, being beyond our power to interrupt.
In the lower portion of the esophagus (about one-third) the muscles are of the unstriped variety (this is the first appearance of unstriped muscle in the alimentary tract, from this part on it has no other kind) . The normal movements of unstriped muscle are exactly suited to the requirements of the digestive process: they are deliberate and slow instead of forcible and sudden, in consequence of which they accomplish not only the passage but the softening of the food by the admixture of mucus and water, thus facilitating the contact of the digestive fluid with the whole mass. Through the cardiac sphincter of the esophagus it enters the stomach. It is first swept to the fundus, which serves as a storehouse while successive portions of the food are acted upon. In the stomach the mechanical process consists in the action of the muscle coats, which move the food about that it may be still more softened and thoroughly mixed with gastric juice. The contractions of the muscles of the stomach go on in a wave-like manner toward the pylorus, alternately constricting and relaxing the walls of the cavity.
In the stomach the chemical process consists in conversion of proteid foods into peptones and amino-acids. The digestive fluid is gastric juice. The enzymes are pepsin and rennin. These act upon proteins after they have been acidulated, and finally reduce them to peptones. (Some protein food may be absorbed as peptone but the greater part is reduced to still simpler forms, as amino-acids, etc.)
Pepsin cannot act in alkaline fluids; gastric juice is acid (hydro- chloric acid is essential).
In the digestion of meats, the acid softens the connective tissue fibers (which are already partially gelatinized by cooking) and thus prepares them for the action of the pepsin. Eggs are digested in the same manner but more easily, having so little connective tissue.
160 ANATOMY AND PHYSIOLOGY
Milk is first acted upon by rennin which sets free the albumin contained and brings out the casein from the caseinogen, in the form of a soft coagulum or curd. Pepsin then transforms both albumin and curd into peptone.
Clinical Note. — The curdled milk which a healthy baby regurgitates is a normal substance; the rennin has acted and it only needs the pepsin to com- plete its digestion.
The protein of vegetables is digested in the stomach after the cellulose fibers are softened by the acid. Starch may undergo some slight degree of change in the stomach by the action of the saliva which was mixed with it in the mouth, theptyalin re- maining active until the food becomes acidified.
Fats are freed from their connective tissue envelopes and float as little globules; they are not digested here (to any great extent — this is still uncertain) .
Note. — The mineral salts do not require digestion. They are already dissolved in the water for the purpose of entering into combinations in the tissues. The same is true of grape sugar (dextrose) .
When any portion of the stomach contents is sufficiently pre- pared by gastric digestion, the pyloric sphincter relaxes and the rather thick yellowish fluid called chyme passes through it into the duodenum and thence into the jejunum and ileum.
Chyme contains partially digested starch and proteins, as well as sugars, peptones, fats, water and mineral salts, gastric juice and some mucus.
The acidity of the chyme when it reaches the pylorus causes the con- traction of certain muscles of the stomach which open the sphincter and allow the flow of chyme into the duodenum, and thence into the ileum.
In the intestine the mechanical process is a continuation of the peristaltic movement of the stomach. The circular fibers, by fre- quent constrictions of the tube, divide the mass and force it along, at the same time preventing a too rapid passage. The longitudi- nal fibers assist, by a series of wave-like contractions.
The chemical process consists in the further digestion of pro- teins, sugars and starch; also the digestion of fats.
The intestinal fluid is a mixture of intestinal juice, pancre- atic juice and bile, therefore it contains several ferments or enzymes. It is most active in the duodenum.
INTESTINAL DIGESTION l6l
Intestinal juice (succus entericus) completes the digestion of proteins and sugar, also of starch. It is an alkaline fluid secreted by the small glands of the intestine, namely — the glands of Brunner and the follicles of Lieberkuhn or intestinal glands. It contains several enzymes, erepsin, maltase, invertase and others.
By erepsin the continuation of protein digestion is carried on, by maltase and invertase the maltose formed in the mouth from starch is converted into dextrose.
Pancreatic juice is an alkaline fluid secreted by the pancreas. Its enzymes are several in number, the most important being trypsin, amylopsin and steapsin. Trypsin completes the digestion of proteins already begun in the stomach, carrying it still further by splitting those peptones which were not absorbed, into amino- acids. (Trypsin digestion is important.)
Amylopsin (pancreatic diastase) acts like ptyalin (or salivary diastase) converting starch into dextrose. The principal digestion of starch is accomplished here.
Steapsin is the fat-splitting enzyme. Fats are probably freed from their connective tissue envelopes before reaching the intestine, and the steapsin splits them up into fatty acids and glycerine. These fatty acids combine with the alkali of the intestinal fluids to form soaps, which in solution are absorbable. (Also soaps can emulsify the fats which continue to arrive, that is, divide them into fine particles which will be suspended in the alkaline solution.)
What becomes of the soaps? Some are absorbed as such, some form an emulsion with other fats. An emulsion was long believed to be the only form in which fat was absorbed, and this is not yet disproven. At all events, fat still appears as a white emulsion called chyle in the absorbing vessels of the small intestine.
The third important constituent of intestinal fluid is bile. This is an alkaline fluid which enters the duodenum with the pancreatic juice by the opening at the bile papilla.
When the chyme enters the duodenum, the acid which it contains causes the opening of the valve of the common duct, and the bile flows into the duodenum. As soon as the chyme is made alkaline (by bile and intestinal fluid) the valve closes not to be again opened until another portion of acid chyme is received from the stomach.
The bile contains no digestive enzymes, ii
1 62 ANATOMY AND PHYSIOLOGY
What, then, are the uses of the bile which is poured into the in- testine with the pancreatic juice?
First, it is alkaline in reaction — the intestinal enzymes act in an alkaline medium. Second, it holds the soaps in solution, favoring their absorption. Third, it assists the fat-splitting func- tion of steapsin and dissolves fatty acids so that they may be absorbed. Fourth, it accelerates the digestion of fats. Fifth, it delays putrefaction in the intestines, probably — in part — by assist- ing peristalsis, and thus preventing stagnation of the whole contents.
Clinical note. — Experiment and observation prove that the presence of bile is necessary to nutrition. Without it a person may eat large quanti- ties of food and still lose weight.
The work of digestion is continued in the jejunum, and to a lesser degree in the ileum. By the absorption of digested food, the intestinal contents are diminished in quantity and changed in character, containing less water and approaching a firmer consistency.
After passing through the jejunum and ileum into the large intestine, some digestion may still go on by the action of the in- testinal juice which was incorporated with the mass, but the major portion of the contents of the colon consists of undigested remnants and waste.
From the foregoing we gather the following summary:
Proteins are digested in the stomach and intestine. The enzymes are pepsin and rennin, trypsin, and erepsin. Products of protein digestion, peptones and amino-acids.
Starches are digested in the mouth and the intestine. En- zymes— ptyalin in the mouth, and amylopsin in the intestine. Product, dextrose.
Sugars are digested in the mouth and intestine. Enzymes — maltase in the mouth, and maltase and imertase in the intestine. Final product, dextrose. Dextrose (glucose, grape sugar) and levulose taken with the food, do not require to be changed; they are already soluble and absorbable.
Fats are freed from their connective tissue in the stomach, and split or emulsified in the intestine. Products, glycerine and fatty acids, fat-emulsion.
STIMULI OF DIGESTIVE GLANDS 163
Vegetables are digested in the stomach so far as proteins are concerned, their connective tissue having been previously softened. Their starch and sugar content, and their oils — as above.
The best temperature for digestion is the normal temperature of the interior of the body, or about 100° Fahrenheit.
Clinical note. — The reason for abstaining from ice-water during digestion
is that the various ferments cannot do their work in a temperature of much less
than 100° F. (If people will eat ice-cream after dinner they should take it
slowly, that the whole process of digestion be not too long delayed by the
• necessity of waiting for the temperature to rise again to ioo°.)
Warm foods make less of a demand upon the vitality of the body than cold ones.
The activity of the digestive glands (like that of all others) is called forth by a stimulus of some sort conveyed to the gland cells by sympathetic nerves.
In the case of the salivary glands this stimulus is aroused by several things — first, by the presence of food in the mouth; second, by the introduction of substances which have an agree- able flavor or odor; third, by movements of the muscles of mas- tication; fourth, by the sensation of nausea; fifth, by the thought of food (which is a psychic stimulus). The salivary secretion is diminished in fevers and wasting diseases, also by certain psychic impressions — as fear, anger, anxiety, and the like. Everyone knows the dry mouth of strong emotion, especially if associated with apprehension.
The gastric glands respond in a similar manner; the presence of food in the stomach causes a strong flow, flavors and odors assist. Small amounts of bitter flavors in food increase it, aromatic substances have the same effect.
Clinical note. — These do not act at once; therefore aromatic or strongly flavored medicines should be given a quarter of an hour or more before meals in order to ensure the best result.
Water increases the flow. The habit of taking water before meals is a good one, but if taken immediately before the quantity should be small. Alcohol, like the bitters, also stimulates the flow of gastric juice.
The thought of food causes the psychic flow. Strong desire for food, or appetite, causes a psychic flow of very active juice within
1 64 ANATOMY AND PHYSIOLOGY
four and one-half minutes. The thought of distasteful food inhibits the flow of gastric juice, as do nauseous flavors and odors.
Clinical note. — The sense of distaste diminishes the flow of gastric juice, therefore it would seem wise to avoid forcing a patient to take more than the minimum necessary quantity of food while the distaste is marked.
Pepsin is sensitive to alkalies. Alkalies and malts may favor a flow of gastric juice, but if given during digestion, they destroy the pepsin.
Proteins always soften when treated with water, and become transparent before they can be dissolved; salty foods do not easily soften — they are not easily digested. This is the reason why it is well to precede the cooking of dry and salty foods by soaking in water.
The presence of ordinary fat delays digestion in the stomach, although a very finely divided fat, as in cream or the yolk of egg, may be there partially digested by a ferment called gastric steapsin.
An accumulation of stomach contents is embarrassing to the gastric juice, hence the advisability of deliberation when taking one's meals.
Note. — Hemoglobin is split by pepsin into hematin and a globin. The hematin gives the dark color to the blood which is vomited after gas- tric hemorrhage, and also to that which appears in f eces after intestinal hemorrhage. (Hemoglobin is contained in the red cells of the blood.)
The passage of food through the intestine is normally slow, and thus it is fully exposed to the surfaces of the circular folds of the mucous membrane. By the absorption of digested food the intes- tinal contents are diminished in quantity and changed in character, containing less water and approaching a firmer consistency. After passing through the ileo-colic sphincter into the large intestine there is little but waste remaining, undigested food forming the major portion. This collection of waste, liquids, coloring matter and undigested food is called f eces. The coloring matter is derived partly from bile, partly from food. (It may be modified by drugs ; for example, iron and bismuth give a black color to the feces.) (The odor is due to sulphuretted hydrogen and to skatol — it also is modified by food.) The consistency depends upon the amounts of water and mucus, approaching a liquid form when the intestinal
DIGESTIVE ENZYMES 165
contents are hurried through the tube before absorption can take place.
Defecation is the act of expelling the feces. The bowel muscles contract and the sphincter ani relaxes; the abdominal muscles assist by compressing the organs from above. The dietary which contains the largest proportion of waste material will leave the greatest quantity of feces and lead to more frequent defecation than one which is made up of digestible substances only. The peristaltic action of the bowel is made more effective by the pres- ence of a reasonable amount of matter to be acted upon.
Clinical notes. — Diarrhea is the passing of frequent loose or watery stools. It occurs when the contents of the small intestine are hurried along too rapidly by some irritating substance which causes excessive peristalsis and a leakage of the watery portion of the blood.
Constipation is caused by a too concentrated diet and slow peristalsis. Since bile is a natural stimulant to the muscles of the bowel, constipation is often associated with a torpid liver; it is also caused by lack of fluids in the bowel. Therefore this is one reason why water is an important food.
Origin of enzymes of the digestive fluids. — They are formed, usually, within the glandular cells of the organs which secrete the fluids. Sometimes, by the fusion of a substance derived from the cell with another called a pro-enzyme which it meets in the fluid.
For instance, the pancreas secretes two enzymes — amylopsin and steapsin. It also secretes trypsinogen, a pro-enzyme which unites with a special sub- stance in the intestine to form the enzyme try p sin. In the one case (that of amylopsin or of steapsin) the enzyme leaves the cells already formed, in the other (that of trypsin) it is formed outside of the cells.
As each digestive organ secretes its own fluid, so each fluid con- tains its special enzymes for special purposes. For instance, the enzymes or ferments of saliva cause rapid digestion of starches, but not of eggs or meat. Those of the gastric juice assist the digestion of eggs or meats, but not of starches.
While it would probably be possible to digest the foods by the use of chemical substances alone, as acids or alkalies, the process would require such a high temperature that the body could not endure it, and it would be so slow that we might starve while waiting. The presence of enzymes not only accelerates the process of digestion, but allows it to go on at the body temperature, hence their great importance.
1 66 ANATOMY AND PHYSIOLOGY
The nature of the changes which the food must undergo is, a separation or splitting into simpler bodies. Most food substances are complex and insoluble. The object of digestion is to convert them into simple and soluble substances which can be absorbed. In order to accomplish this, they must be not only mixed with water, which is a mechanical process, but combined with it or hydrolysed which is a chemical process. The digestive enzymes belong to the class called hydrolytic enzymes because they act by hydrolysis.
Hydrolysis means decomposing the water which is present and uniting its elements, H and O, with other substances (also in process of decomposition or breaking down by the action of the same enzyme).
According to Hammarsten, no glands in the body can work so rapidly, can produce so great a quantity of fluid in the same time as the salivary glands, not even the kidneys. Eight to four- teen times the weight of all the glands together may be produced within one hour.
Saliva has the power of splitting sulphureted hydrogen from the sulphur oils of onions, radishes, etc.
Clinical note. — Ptyalin exists in the saliva at birth but does not become active under three or four months of age.
SUMMARY
Digestion.- — Is the process of so changing the food that it may be absorbed.
Absorption.' — Is the process of taking up certain substances and conveying them to, the blood.
Circulation.' — Is the process of carrying the blood and other substances to every part of the body.
Assimilation.' — Is the process which goes on in the tissue cells whereby they make use of the food which is conveyed to them.
We have now to study the organs which distribute the products of digestion, and the composition of the food-bearing fluids — blood and lymph. Assimilation is nature's own secret, not yet revealed to the mind of man. This is a phase of metabolism.
ABSORPTION OF FOOD
Accompanying the digestion of food the absorption of nutritive principles takes place.
It is quite possible that some portion of the sugars is taken up by blood-vessels of the stomach, and it is probable that more or less
ABSORPTION OF FOOD
167
of the water and dissolved salts are here absorbed, but most of the stomach contents pass through the pylorus as chyme and are re- ceived by the duodenum to be acted upon by intestinal fluids and prepared for absorption. The mill (Fig. 113) are the absorbents which perform this function in the intestine. The epithelial cells with which they are covered take up and transmit the new sub-
FIG. 113. — SECTION OF INJECTED SMALL INTESTINE OF CAT. a. b. Mucosa. g. Villi. i. Their absorbent vessels, h. Simple follicles, c. Muscularis mucosae. j. Submucosa. g, 6. Circular and longitudinal layers of muscle. /. Fibrous coat. All the dark lines represent blood-vessels filled with the injection mass. — (Pier sol.}
stances into lymph spaces within the villus, from which they go either into the blood-vessels or lymph capillaries which the villus contains.
Water and mineral salts (dissolved in the water). — These must pass into the blood capillaries, thence into veins, and through them to the portal vein (page 167). By this they are taken to the liver.
Sugars pass by the same route, namely, blood capillaries and veins to the liver from the intestine.
1 68 ANATOMY AND PHYSIOLOGY
Peptones and their products, amino-acids, also find their way in the same manner to the portal blood and the liver, from the intestine.
Thus it appears that all proteins, sugars, water and salts pass through the liver. There, water and salts are used for various combinations; sugars are converted into glycogen to a great extent and stored for future use; and proteins furnish tissue food and materials for bile.
Glycogen. — This product of the action of liver cells upon carbohydrates is stored in the liver. When needed it is returned to the blood (as sugar again) and distributed to the tissues, notably to the muscles. Being readily oxidized it favors the rapid changes in muscles which result in motion. Therefore, it follows that sugar and starch are sources of muscle energy.
Lacteal s Blood vessels
%^w:;
FIG. 114. — LOOP OF SMALL INTESTINE WITH LACTEALS. — (Morris.)
Urea. — This is another substance which appears as a result of the activity of the liver cell. It is one of the final forms of waste derived from the metabolism of protein substances. It is a very poisonous waste and is elim- inated from the blood by the kidneys.
Having yielded materials for these functions, the remaining food substances are carried away from the liver by hepatic veins and finally into the general circulation, to be distributed to the tissues of the body.
There remain the fats: These, being transferred by the epithe- lial cells to the lymph-spaces, take the other route, in the form of an emulsion known as chyle. They pass into the lymph capillaries
ABSORBENT VESSELS
169
FIG. 115. — DIAGRAM SHOWING THE ROUTES BY WHICH THE ABSORBED FOODS REACH THE BLOOD OF THE GENERAL CIRCULATION (G. Bachman). I. i., Loop of small intestine; int.v., intestinal veins converging to form in part, p. v., the portal vein, which enters the liver and by repeated branchings assists in the formation of the hepatic capillary plexus; h. v., the hepatic veins carrying blood from the liver and discharging it into, inf. v. c., the inferior vena cava; int. L v., the intestinal lymph vessels converging to discharge their contents, chyle, into rec. c. the receptac- ulum chyli, the lower expanded part of the thoracic duct; th. d., the thoracic duct discharging lymph and chyle into the blood at the junction of the internal jugular and subclavian veins; sup. v. c., the superior vena cava. — (From Brubaker's Text- book of Physiology.')
170 ANATOMY AND PHYSIOLOGY
of the intestine (so-called lacteals), which open into the lymph vessels in the submucous coat. By these vessels the chyle finally reaches the thoracic duct and is carried to the blood, to be distrib- uted to the tissues of the body by way of the general circulation.
Osmosis
The forces which regulate absorption include the process of osmosis, which has been described as the passage of " diffusion streams" whereby solutions of different strengths or densities pass through animal membranes. This does not explain all that happens; it is recognized that certain very important chemical processes must be involved in the cell walls of the intestines, the nature of which is beyond our present understanding. We bid farewell to peptones and amino-acids in the intestinal canal and greet albumins and fats in the blood-vessels which leave it; we find solutions of soaps and fatty acids on the outside of the villus — emulsified fat in the lymph tube within.
The same forces by which the nutritive fluids were absorbed into the vessels, are again at work to effect their transference from the vessels to the tissues of the body.
In the tissues. — The solution of nutritive substances, having been carried by the blood-vessels to the minutest channels in the body, passes into the tissue spaces as lymph, which bathes the cells themselves, so that they may receive the material necessary for their action and upbuilding.
Different tissues appropriate their different foods, and each gives back the products of its own activities as tissue wastes, which in turn enter the blood to be carried to tissues which can make another use of them, or to organs which can dispose of them as excretions.
The next chapter will introduce the study of the blood, heart and blood-vessels, or the system of circulatory organs for dis- tributing the blood throughout the body.
CHAPTER X THE BLOOD AND CIRCULATORY ORGANS
THE BLOOD
The blood is the most important fluid in the body. It not only carries food to every part, but bears waste matters to those organs which can dispose of them in the form of excretions. It consists of a clear yellowish fluid called plasma and small round cells (invisible to the naked eye) called corpuscles (little bodies), which float in the plasma. The corpuscles are of two sorts, red and white.
FIG. 1 1 6. — CORPUSCLES OF BLOOD, AS SEEN UNDER THE MICROSCOPE. Four white ones are shown. The red ones have a tendency to form rows. — (Funke
and Brubaker.)
It is convenient to follow the usage common in clinical work and speak of them as red and white cells.
Blood has a characteristic odor which varies in different animals.
The temperature of the blood is about 100° F.
The reaction is alkaline.
The red cells (erythrocytes) are non-nucleated, flexible and elastic. They are very numerous, numbering 4,000,000 to 4,500,000 in a cubic centimeter. They measure about ^3 of an inch in diameter, and their shape has been usually described
171
172 ANATOMY AND PHYSIOLOGY
as that of a flattened sphere (Fig. 116). (They are oxygen- carriers.)
Note. — The illustration presents the appearance under the microscope of blood which has been removed for a time from the vessels and cooled. Careful studies under other conditions indicate that the living cells are slightly bell-shaped. In the early stage of formation they contain a nucleus.
The red cells are composed largely of hemoglobin held in a net- work or stroma of protoplasm. This itself is amber colored, but when a great number of cells are together as in a drop of blood,
FIG. 117. — WHITE CORPUSCLES PENETRATING CAPILLARY WALLS. — (Landois and Stirling.}
it gives the red hue to the fluid. The color varies with the quantity of oxygen in the cell, from bright scarlet with much oxygen to bluish red with little. Hemoglobin is a protein substance whose most important property is its power to combine with oxygen forming oxy-hemoglobin, and to give it up. It contains a minute quantity of iron in combination (hematin) which is neces- sary to life processes.
The origin of the red cells is in the red marrow of cancellous bone.
The white cells or leucocytes are of different sizes (the average size, about ^00 of an inch in diameter). They move more slowly in the plasma and are far less numerous, numbering only about 7500 in a cubic centimeter.
They are nucleated, flexible and elastic. Their shape is spher- ical (often irregular) , and they consist of a transparent material containing one or several nuclei and many fine granules of protein substances of several kinds. They also contain glycogen and enzymes.
THE LEUCOCYTES
173
The white cells frequently change their shapes by means of ameboid movements, that is, like the ameba, they thrust out portions of their substance and draw them back. They can send out little prolongations and draw floating particles to themselves, or they can wrap themselves around foreign substances.
They possess also the power of slipping (squeezing) through the walls of capillary vessels. This is called diapedesis (Fig. 117).
Of the several varieties of leucocytes the percentage of polymorpho- nuclear cells (nuclei of many shapes) is the largest.
The polymorphonuclear cells (oftenest called polynuclear) and the lymphocytes are called phagocytes, because they destroy bacteria by absorbing and digesting them. This process is called phagocytosis (to be referred to later on) (pp. 214 and 220).
The origin of the white cells is from two sources : the lymphocytes originate in lymph glands and other lymphoid tissues; the poly- nuclear leucocytes and others are developed from cells in the marrow of long bones. A third form of colorless cell is called a blood plate or platelet.
The platelets are very small, being barely one-half the size of the ordinary cells. They are similar to leucocytes; their origin is not understood, but they take an important part in the coagu- lation of blood.
The plasma is a thin watery saline fluid in which the corpuscles float. It contains both nutritive and waste matters in solution, and certain elements from which fibrin is derived, also enzymes (and certain extractives). Fibrin is essential to the production of a blood-clot, without which hemorrhage would never cease of its own accord. (Fibrin and corpuscles removed — serum remains.)
The substances dissolved in the watery portion of the plasma are :
Nutritive (derived from food) . .
Waste products (derived from tissue changes).
Mineral salts. Chiefly salts of
Proteins (chiefly)
Sugars Fats
Extractives
Sodium
Potassium
Calcium
( Serum-albumin Paraglobulin Fibrinogen Prothrombin (or Thrombogen)
Urea
Uric acid, etc.
174 ANATOMY AND PHYSIOLOGY
The serum-albumin is the great tissue builder. The fibrinogen is a fibrin maker (paraglobulin may assist, its use is not fully known).
Sugars and fats are tissue foods and sources of heat.
Mineral salts preserve the necessary alkalinity of the blood and assist in the formation of certain tissues (as bone). Sodium chloride (common salt) is the most abundant and to this is due the salinity of the blood.1 Salinity is an exceedingly important quality of plasma. It is essential to the interchange of fluids between the vessels and the tissues and to the maintenance of the rhythmic action of cardiac muscle. It is also necessary for the preservation of blood corpuscles. Pure water invades them (by osmosis) and so dilutes them that they swell and are de- stroyed. The salinity of plasma is the same as that of the cells, therefore no "diffusion streams" (or osmosis) can occur and the cells are safe. For Coagulation of Blood see p. 217.
THE CIRCULATORY ORGANS OF THE BLOOD
This system includes the heart and blood-vessels (arteries, capillaries and veins). They are the organs which contain the blood.
The heart is a pump. The arteries are elastic tubes which re- ceive the blood directly from the heart. The capillaries are small vessels into which the arteries lead, and the veins carry the blood from the capillaries back to the heart.
Arteries. — Vessels which convey the blood away from the heart. They are flexible tubes whose walls consist of three layers or coats — external, middle, and internal (or tunica adventitia, tunica media, and tunica intima). The external coat is composed of fibrous tissue to which the strength and toughness of the vessel is due; the middle is composed of elastic tissue and unstriped muscle fibers, giving to arteries their yielding and contractile chracter; the internal is thin and smooth and is a continuation of the lining of the heart. Arteries of medium size have most muscle tissue, while the larger ones have most elastic tissue. It is owing to their elasticity that arteries remain open when they are empty or cut across.
1 A "normal saline solution" contains salt in the proportion found in blood.
CAPILLARIES — VEINS 175
Note. — The internal coat is the only one which is continuous throughout the entire circulatory system.
Surgical note. — When a ligature is tied tightly around an artery the middle coat may be felt to break down under the cord, while the external one remains whole, owing to its toughness.
The arteries give off branches which divide and subdivide until the smallest ones can be seen only with the microscope — they are called arterioles. The arterioles lead to the vessels which are smallest of all — the capillaries.
Capillaries. — Vessels which receive blood from the arteries and carry it to the veins. They exist in nearly every part of the body, except cartilages, hair, nails, cuticle, and the cornea of the eye. Their walls have only the internal coat, a single layer of cells — endothelium. It is through this thin wall that the work of exchange is performed between the blood and the various tissues of the body, nutritive material being taken from the blood and certain waste substances being returned to it. To provide vessels for this exchange is the function of the capillaries. They are most numer- ous where most work is to be done, viz., in the lungs, skin, mucous membranes, liver, kidneys and glands.
Their average diameter is WFIO of an inch — just enough to permit the easy passage of the corpuscles. They are uniform in size, neither increasing nor diminishing in caliber.
Veins. — The vessels which gather the blood from the capil- laries and carry it to the heart; they are formed by the uniting of capillaries.
They are at first very small (called venules or venous radicles] but constantly grow larger by uniting with each other, although they often branch and reunite.
Veins, like arteries, have three coats, but their middle coat is neither so elastic nor so muscular, so that they are softer, and when empty or cut, they collapse. The inner coat of the veins presents, at intervals, semilunar folds, making pockets called valves, which allow the blood to flow toward the heart, but prevent it from setting backward freely. If the veins are very well rilled the location of the valves may be recognized by an appearance of puffing out at
170 ANATOMY AND PHYSIOLOGY
those points where they exist (Fig. 118), as the blood fills the pockets from above.
Blood-vessels possess nerves (the vaso-motors) which, by con- trolling the muscular coats, regulate the amount of blood flowing through them at a given time to the structures which they
supply. (An organ at work needs more blood
than an organ at rest.)
They also possess tiny blood-vessels in their walls, the vasa vasorum.
All blood-vessels have sheaths of connective tissue. In the case of the larger ones these are quite strong and sometimes inclose a vein, an artery, and a nerve together for protection.
THE HEART
The heart is a hollow muscular organ through which the blood passes, placed behind the ster- num and just above the central tendon of the FlG Iig _A diaphragm. Its average size is about five
VEIN LAID OPEN TO inches long by three and one-half wide, and two SHOW VALVES. , , ,r ,. ,
and one-half thick.
Note. — The muscle tissue of the heart te called the myocardium.
It is shaped like a cone, about five inches long and three and one-half inches wide, with the base turned upward toward the right shoulder and the apex pointing downward toward the left side. It is composed of several layers of muscle fibers which are peculiar, being involuntary and at the same time striped.
The cavity of the heart is divided by a septum into right and left portions, and as it lies in the body the right heart is nearly in front of the left. Each side consists of two chambers, an auricle (atrium) and a ventricle (ventriculum) (Fig. 120).
The auricles receive blood and pass it into the ventricles. Their walls are thin and flabby. The right auricle, or atrium, presents two large openings for the entrance of veins, and one for communication with the right ventricle. The veins are the superior vena cava from the head and upper extremities; the inferior
THE VENTRICLES
177
vena cava from the trunk and lower extremities. It also has a transverse fold on the posterior wall called the Eustachian valve or valve of the inferior vena cava, and a round depression on the septum between the two auricles (atria), called the oval fossa (fossa ovalis). The left auricle presents two large openings and several small ones for veins, and communicates with the left ventricle.
Posterior branch of right coronary ar tery
Auricular appendage Right coronary artery
Preventricular branch Right marginal branch
Posterior interventicu- lar branch of right coronary artery
r
\M^<
[RIGHT ^f
^VENTRICIL'E
Transverse branch of right coronary artery
Left coronary artery
Anterior interventricu- lar branch of left coronary artery
Left marginal branch
FIG. 119. — ANTERIOR SURFACE OF HEART. — (Morris.) The coronary arteries supply the substance of the heart.
The ventricles expel blood from the heart. They include the apex of the heart; their walls are thick and strong, the left one being the thicker and larger of the two. Certain muscle-fibers in the ventricles pass downward to wind around the apex of the heart and then turn upward; others are transverse, still others oblique; the arrangement causing the heart to harden in contraction, with a twisting motion from right to left and a forcible pressure against the chest wall. This is felt in the fifth interspace, at the left of the sternum and is called the cardiac impulse.
The muscle band of His (auriculo-ventricular bundle) is a name given to a bundle of muscle fibers which connects the auricles and ventricles; the contraction impulse is believed to travel from auricle to ventricle by these fibers.
12
178 ANATOMY AND PHYSIOLOGY
The interior of the ventricles is marked with a number of ridges or bands of muscle fibers (the trabeculce carnece), and certain of these are attached by tendinous cords to the valves of the heart. Each ventricle opens into a large artery, which conveys the blood away — the pulmonary artery from the right ventricle, the aorta from the left.
3"
FIG. 120. — INTERIOR or LEFT HEART. (Observe the difference in thickness of
the walls in auricle and ventricle.) — (Allen Thomson in Brubaker.) i, L. atrium or auricle; 2, division between it and ventricle; 3, wall of left ventricle; 4,_a band of muscle fibers severed; 5, other muscle bands; 6, a leaflet of mitral valve, with tendinous cords; 7, aorta (a large artery) laid open to show semilunar valves; 8, pulmonary artery (semilunar valves closed) ; 9, arch of aorta.
Note. — In the new nomenclature the name "atrium," or forechamber , is given to the main part of the auricle, and the word auricle applies to the auricular appendage alone.
Endocardium. — The lining of the heart. It is thin and firm, resembling serous membrane in appearance, and is continuous with the lining of the blood-vessels, thus making a perfectly
CARDIAC VALVES 179
smooth surface of endothelium throughout, for the current of blood in heart and vessels.
THE VALVES OF THE HEART
The valves of the heart are formed by folds of endocardium strengthened by fibrous tissue and attached to fibrous rings around certain orifices of the different chambers — two in the right heart and two in the left. The opening between the right auricle and ventricle, or tricuspid orifice, is guarded by the tricuspid valve, which is composed of three leaflets. It allows the blood to flow down into the ventricle but prevents it from flowing back. The opening between the left auricle and ventricle, or mitral orifice, is guarded by the bicuspid (or mitral) valve, composed of two leaflets,
FIG. 121. — VALVES OF THE HEART.
i. Right auriculo-ventricular orifice, closed by the tricuspid valve. 2. Fibrous ring. 3. Left auriculo-ventricular orifice, closed by the mitral valve. 4. Fibrous ring. 5. Aortic orifice and valves. 6. Pulmonic orifice and valves. 7, 8, 9. Muscular fibers (auricles removed). — (Bonamy and Beau.}
allowing the blood to flow down into the ventricle but not to return. (Both the tricuspid and mitral valves are connected to certain muscle bands of the ventricles by tendinous cords which control the motion of the leaflets, preventing them from flying upward too far when the ventricles contract.) (Fig. 120.)
The opening from the right ventricle into the artery which leaves it (pulmonary artery) , is guarded by three semilunar valves, which are half-moon shaped pockets called the pulmonary valves. Likewise the opening from the left ventricle into its artery (aorta) is guarded by three semilunar valves called the aortic valves (Fig. 121).
l8o ANATOMY AND PHYSIOLOGY
The semilunar valves allow the blood to flow in one direction only — that is, away from the heart.
FUNCTIONS OP THE CHAMBERS OF THE HEART
The auricles, having received blood from the veins opening into them (the right — blood from entire body; left — from lungs alone) gently contract together to send it down into the ventricles; quickly the • ventricles contract, forcibly and together, expelling blood into the two large arteries — the pulmonary carrying it to the lungs, the aorta to all parts of the body. This process is the systole of the heart; it occupies about eight-tenths of a second, perhaps a
FIG. 122. (DIAGRAM.)
The right auricle receiving blood and passing it through tricuspid valve into right ventricle, which is dilated (semilunar valves closed), — (Dalton in Brubaker.)
trifle more. Then comes the resting-time when the heart is dilat- ing and filling again, called the diastole of the heart.
One systole and one diastole together constitute a cycle of the heart.
During the systole of the auricles, the tricuspid and mitral valves are open and the semilunar valves are closed. During systole of the ventricles the tricuspid and mitral valves close, and the semilunar valves are open (Figs. 122,123). See Heart Sounds (closure of valves) .
The thickness of the ventricle wall is explained by the need for
THE PULSE l8l
sending blood to a distance, the greater thickness of the left being made necessary by the far greater work required of it.
The activity of the heart is unlike that of any other organ in its periods of working and resting. The nerve-muscle structure is so arranged that a series of rhythmic contractions at short intervals, goes on continuously day and night from the beginning of life to its close.
The systole of the ventricles corresponds to the "heart-beat." It occurs at perfectly regular intervals in health, the rate being
FIG. 123.
The right ventricle filled, contracts and expels blood through semilunar valves (tricuspid valve closed}. — (Dalton in Brubaker.)
from sixty to seventy per minute in men, and from seventy to eighty in women. The heart's action is more rapid in the upright position than in sitting or lying, and is increased by any exercise, however gentle. Excitement or emotion will quicken it at once, and it is always faster in children, being about one hundred and forty in the newly born and reaching an average rate of ninety to one hundred at the age of three years; ninety in youth, sev- enty in adults, and eighty in old age. The innervation of the heart is described on pages 185, 186.
The Pulse. — The effect of the heart-beat upon the current of the blood may be felt in the arteries, which are distended for an instant by the blood forced into them as the ventricles contract.
182
ANATOMY AND PHYSIOLOGY
This gives the effect of a beating in the arteries, which is called the pulse. The pulse-rate corresponds with the heart-beat; therefore, the rate and force of the heart's action are judged by means of the pulse.
The Heart Sounds
The action of the heart causes certain sounds, named the first and second. The first accompanies the sudden closure of the tri- cuspid and mitral valves, as the ventricles contract. It is the
UPPER ATTACHMENT OF PERICARDIUM
BRANCHES OF PUL MONARY ARTERY
AORTA--,
BRANCHES OF LMONARY ARTERY -PULMONARY ARTERY
DIAPHRAGM PERICARDIUM
RIGHT ATTACHMENT OF VENTRICLE PERICARDIUM TO DIAPHRAGM
DIAPHRAGM
FIG. 124. — The heart in situ. The pericardium has been cut open in front, and
reflected.— (Testut.)
systolic sound — caused by the systole of the ventricles. The sec- ond accompanies the sudden closure of the semilunar valves. It is the diastolic sound, occurring with the diastole of the ventricles. The first or systolic sound is the louder and larger, being due to the contracting of muscle fibers as well as to closure of valves. The second, diastolic sound is short and sharp, due to valve closure only. The two sounds are compared to the spoken words — lubb dupp.
THE PERICARDIUM l83
When the blood is forced into the elastic arteries by a contraction or beating of the heart it stretches them. When the contraction is ended, the wall of the artery recoils and there is a setting back of the blood for an instant toward the heart, but it is stopped by the closing semilunar valves, which thus make the second sound.
Clinical note. — If the valves of the heart' are rough, the sounds are changed by a "murmur." If they cannot close perfectly, a portion of the blood will flow backward instead of going forward, and this is regurgitation. This, also, changes the sound of a valve and causes a murmur.
The pericardium (Fig. 124). — A loose serous sac enclosing the heart. The layer which closely covers the heart, or the visceral layer, is the epicardium. It covers the aorta and pulmonary arte- ries for about one inch, then leaves them to become the parietal layer or lining of the fibrous sac which encloses the whole, and which is closely attached to the diaphragm below and the great vessels above. A small quantity of pericardial fluid prevents fric- tion between the surfaces, as the smoothly covered heart beats in the smoothly lined cavity; this increases in inflammation of the pericardium, or pericarditis, and it is sometimes necessary to remove it by tapping.
REVIEW. — PRINCIPAL POINTS OF INTEREST IN THE HEART RIGHT AURICLE
Openings of two large veins bringing blood from the body. Opening of coronary sinus bringing blood from the heart itself. Oval fossa and annulus ovalis (or oval ring). Eustachian valve (or valve of inferior vena cava). Tricuspid orifice with tricuspid valve.
RIGHT VENTRICLE
Tricuspid orifice and tricuspid valve. Opening for pulmonary artery, and pulmonary valves. Trabeculae carneae (fleshy bands), and the tendinous cords con- necting them with tricuspid valve.
LEFT AURICLE
Openings of three or four pulmonary veins. Mitral orifice with bicuspid (or mitral) valve.
1 84
ANATOMY AND PHYSIOLOGY
LEFT VENTRICLE
Mitral orifice and bicuspid valve. Opening for aorta and aortic valves.
Trabeculae carneae and the tendinous cords connecting them with the bicuspid valve.
THE COURSE OF THE BLOOD THROUGH THE HEART
Resume. — The blood enters the right auricle, passes down into the right ventricle, and out through the pulmonary artery to the
Left carotid artery
Left subclavia artery
Aorta
Pulmonary artery
Pulmonary veins from left lung
Left auricle
Coronary vessels
Anonyma
Superior vena cava
Pulmonary veins from right lung
Right auricle
Inferior vena cava
- Coronary artery
FIG. 125. — POSTERIOR SURFACE OF HEART. Pulmonary veins bringing pure blood to left auricle. — (Morris' Anatomy.)
lungs; it returns by the pulmonary veins to the left auricle, passes down into the left ventricle, and out through the aorta to every part of the body, from which it is returned by two large veins to the right auricle again.
CARDIAC NERVES 185
The course from the right ventricle through the lungs and back to the left auricle is called the pulmonary circulation (Figs. 125 and 1 60).
The course from the left ventricle through the entire body or " system" and back to the right auricle is called the systemic circulation or main circulation (Fig. 126).
Important notes. — Pure blood is carried from the heart through the systemic arteries to all tissues in the body to nourish them. This blood is called arterial blood; it is bright red in color. The term pure blood and arterial blood are used to signify one and the same thing.
Impure blood from the tissues of the body is returned to the heart by the systemic veins. It is called venous blood; it is purple-red or blue in color and contains waste matters. The terms impure blood and venous blood are used to signify one and the same thing.
The venous blood from the body is poured into the right side of the heart, from which the pulmonary artery conveys it to the lungs. Consequently the pulmonary artery is unlike others, because it carries venous blood from the heart; and the pulmonary veins are unlike others because they carry arterial blood to the heart.
Innervation of the heart. — As already mentioned, p. 176, the heart muscle or myocardium has a structure peculiar to itself. Anatomically its fibers differ from those of other muscles in size and arrangement; physiologically it is unlike any other striped muscle in the body, being involuntary although striped. Cardiac muscle responds to the stimulus brought by two sets of nerves, called accelerator and inhibitor nerves. By the accelerator nerves the rapidity of the heart-beat is increased; by the inhibitors it is slowed. These nerves are branches of the pneumogastric or vagus nerve. A long unsettled question is, whether in the absence of these, the heart would still beat under the chemical stimulus alone of tissue change. Years of experimentation and observation incline scientists to believe that this is possible.
The heart muscle of cold-blooded animals performs rhythmic contractions for several hours after removal from the body; to insure this action it is only necessary to keep it moistened in a mixture of calcium, potassium, and sodium salts in solution. The chemical action between this fluid and that within the cells is sufficient to produce contractions, following each other in rhythmic order.
So in life, an interchange of chemical products between lymph and cell contents may furnish a stimulus which keeps the heart in action, the
1 86 ANATOMY AND PHYSIOLOGY
function of the nerves being to accurately regulate the rate at which con- tractions.occur. This is the myogenic theory of the cause of the heart beat. Another theory, not so generally held, is the neurogenic, which assumes a special nerve system in the myocardium, acting automatically and regulated or modified by accelerator and inhibitor nerves as above described.
The velocity of the normal blood current is greatest in the larger arteries and least in the capillaries. It increases in the larger veins but never equals that in the arteries. The time required for the entire circuit from heart to heart again, is about twenty-eight seconds, or approximately, in the time of twenty-six to twenty- eight heart-beats.
The onward flow of the current, as it is expelled from the heart, is assisted by i, the elastic recoil of the arterial walls (after the stretching caused by the blood which is pumped into them with each systole), 2, the pressure of contracting muscles on the veins, forcing the blood toward the heart, 3, the intake of breath (or aspiration of the thorax) when the auricles are opened to receive blood, and 4, the valves of the veins which allow the blood to flow onward but not backward.
The act of aspiration is very closely associated with circulation; deep breathing alone will promptly quicken the action of the heart and, consequently, the velocity of the stream.
Variations due to emotion, excitement, etc., — have been al- luded to. Blood pressure will be considered in Chapter XII.
The total quantity of blood is estimated at about one-twelfth of the body weight Roughly speaking, it is distributed (in a state of rest) as follows: — one-quarter in the muscles, one-quarter in the liver, one-quarter in the heart, lungs, arteries and veins, one- quarter in other organs. Of course, during the activity of any spe- cial part of the body, as for example, in the digestive system — the proportions are changed, as the most active organs require most blood, leaving less for the others at that time.
CHAPTER XI THE CIRCULATION OF BLOOD
THE PULMONARY CIRCULATION
This is the circulation of the blood through the lungs, that it may become aerated or purified.
The pulmonary artery leaves the right ventricle, carrying impure blood, and soon divides into two branches, the right and left pulmonary arteries (one for each lung), which break up into a capillary network around the air cells. From this network veins arise which, by uniting, form two from each lung, making the four pulmonary veins carrying purified blood to the left side of the heart. They enter the left atrium.
THE SYSTEMIC CIRCULATION
This is the circulation of the blood through the entire body or "system/7 that it may nourish the tissues and organs (Fig. 126).
Arteries of the Systemic Circulation1
The aorta (Fig. 127), having received pure blood from the lungs, leaves the left ventricle, arches over the root of the left lung to the left side of the fourth thoracic vertebra, then (gradually coming to the front of the spinal column) passes down through the diaphragm, and ends by dividing at the fourth lumbar vertebra (a little below the level of the umbilicus). Thus it consists of three portions: the arch, the thoracic aorta, and the abdominal aorta.
The arch of the aorta extends from the heart to the body (lower border) of the fourth thoracic vertebra. It reaches almost as high as the sternal (or jugular) notch.
It may be felt in thin persons by pressing the finger tip down behind the bone.
1 The names of all of the arteries are given in tabular form on page 3 79. Only the principal ones are here described.
187
i88
ANATOMY AND PHYSIOLOGY
FIG. 126. — SCHEME OF SYSTEMIC CIRCULATION. Arteries colored red; veins, blue.
ARTERIES AND VEINS
189
RIGHT COMMON CAROTID
Jugular vein
Right lymph atic duct
Inferior vena cava
Abdominal vessels
LEFT COMMON CAROTID
Vagus nerve
Thoracic duct L. V. anonyma
FIG. 127. — THE AORTA, SHOWING THE THREE PORTIONS — (Morris.)
ANATOMY AND PHYSIOLOGY
Branches of the arch in their order:
Two coronary (right and left), .to heart muscle (Fig. 119).
[ Right subclavian to right
upper extremity. Right common carotid
right head and neck.
One left common carotid .... to left head and neck. One left subclavian ....... to left upper extremity.
One anonyma, i| inches long
to
Phrenic nerve Subclavian artery - Subclavian vein
Anterior intercostal branch
Branch of mammary
Common carotid
Internal jugular vein Subclavian vein Scalenus anterior muscle
— Sternum
I Perforating branches (supplying mam- mary gland)
Superior epigastric, running down from internal mammary
Inferior epigastric, running up from external iliac
FIG. 128.— SHOWING SUBCLAVIAN ARTERY AND TWO OF ITS BRANCHES (Thyroid axis and internal mammary). — (Morris.)
THE PRINCIPAL ARTERIES or THE UPPER EXTREMITY
The subclavian artery (Fig. 128) passes out over the first rib and under the clavicula (therefore subclavian) to the axilla, or armpit. The brachial plexus lies above it in the neck, and the
AXILLARY ARTERY
IQI
subclavian vein is in front of it. The right subclavian is a branch of the anonyma. Both subclavians end at the lower border of the first rib.
Branches. — The vertebral branch runs upward through trans- verse processes of the vertebrae to the brain.
The internal mammary branch runs downward inside the chest behind the costal cartilages into the abdominal wall. It distributes branches to the mammary gland and' to intercostal muscles.
FIG. 129. — SUBCLAVIAN AND AXILLARY ARTERIES. — (Testut.}
The thyroid axis is a short trunk ; it gives a branch to the thy- roid gland and others to the neck and shoulder.
An axis (artery) is a short vessel dividing at once into two or three.
The axillary artery (Fig. 129) is a continuation of the sub- clavian. It begins, therefore, where the subclavian ends — in the apex of the axilla, at the lower border of the first rib — and con- tinues through the axillary space.1
1 Axillary space, p. 368.
ANATOMY AND PHYSIOLOGY
Branches (thoracic, subscapular, circumflex.} — To all structures around the axilla. One, the lateral thoracic, gives arteries to the mammary gland.
The brachial artery (Figs. 129, 131) begins where the axillary ends, at the lower border of the axilla, or armpit, and extends
FIG. 130. — DEEP PALMAR ARCH.
Made by continuation of the radial artery. This is covered by the muscles of the thenar and hypothenar eminences.
downward in front of the arm (with the biceps muscle) to the bend of the elbow, where it divides into the radial and the ulnar arteries. Its branches supply the muscles of the humerus and the bone itself. (The median nerve lies next to this artery under the border of the biceps muscle.)
RADIAL AND ULNAR ARTERIES
193
Axillary artery
Lateral cord
Pectoral muscle
Median nerve Brachial artery
The radial and the ulnar arteries pass downward in the radial and ulnar sides of the fore- arm to the hands. The radial supplies the muscles in front of the radius, and winds to the back of the wrist to find its way to the palm by pass- ing forward between the first two metacarpal bones. It forms the deep palmar arch, which crosses the palm under the long tendons (Fig. 130).
The ulnar supplies the muscles in front of the ulna, and forms the superficial pal- mar arch, which crosses over the long tendons in the palm (Fig. 131).
Note. — The superficial arch crosses the palm opposite the level of the web of the thumb when put "on the stretch." The deep arch crosses about a finger- width nearer the wrist.
The digital arteries run in the sides of the fingers; they are branches of the superficial arch.
Clinical note. — The pulsation of the radial artery is easily felt above the wrist in front, next to the tendon of the radial flexor of the wrist.
Surgical note. — A direct com- munication exists between the deep and superficial arches, con- sequently severe hemorrhage easily occurs in the palm, since blood will flow from radial and ulnar arteries at one and the same time, and it is sometimes neces- sary to ligate both.
Ulnar nerve and
artery
adial nerve and artery
Branches to hand
FIG. 131. — AXILLARY, BRACHIAL, RADIAL AND ULNAR ARTERIES. SUPERFICIAL ARCH.
IQ4 ANATOMY AND PHYSIOLOGY
PRINCIPAL ARTERIES OF THE HEAD AND NECK
The common carotid arteries. — (Fig. 127). The right is a branch of the anonyma; the left is directly from the arch of the aorta. They proceed upward on either side of the trachea, with the internal jugular vein on the lateral side and the vagus nerve behind them. They carry the blood supply of the head and neck.
The common carotid divides at the upper border of the .thyroid cartilage into internal carotid for the interior of the head, and external carotid for the exterior of the head and the neck.
FIG. 132. — ARTERIES OF THE BRAIN. — (Morris.} Cerebral arteries pass from the base of the brain to all parts of the surface.
The internal carotid is deep in the neck; it runs up to the head and through the carotid canal into the cranial cavity.
Principal branches. — Ophthalmic, to eye and appendages, nose, and forehead. (The supraorbital artery is a branch of the ophthalmic.)
Middle cerebral to the brain, anterior cerebral to the brain (Fig. 132).
PRINCIPAL ARTERIES OF THE HEAD 195
Note. — The internal carotid makes four sharp turns after entering the carotid canal in the petrous bone, and by this means the force of the current in this large vessel is modified before it reaches the delicate tissues of the brain. The internal jugular vein and vagus nerve accompany it in the neck.
The external carotid artery supplies the face, and front of the neck and scalp (Fig. 133).
Principal branches. — Superior thyroid, to the thyroid gland and larynx. Lingual, to the tongue and tonsil. Facial (or external maxillary) to the face, soft palate and tonsil. Occipital, to the back of the head and neck.
FIG. 133. — FACIAL, TEMPORAL AND OCCIPITAL ARTERIES.
Clinical notes. — The external maxillary (facial) artery runs toward the bridge of the nose. It sends two labial arteries to the borders of the lips; the one in the upper lip supplies a branch to the septum of the nose, therefore, compression of the upper lip will sometimes stop "nose-bleed."
The lingual artery ends at the tip of the tongue, in a branch (ranine) which might be severed in cutting too freely for "tongue-tie."
Having given off its branches, the external carotid passes into the substance of the parotid gland and divides into the temporal and internal maxillary.
The temporal passes through the parotid gland and across the zygoma to the side of the head, supplying temporal branches to the scalp. The internal maxillary runs between the muscles of mas- tication (in the infratemporal fossa) to the deep parts of the face, including the nose and pharynx. The dental arteries are all de- rived from this vessel.
196 ANATOMY AND PHYSIOLOGY
Collateral Circulation. — An important descending branch of the occipital artery runs down under the deep muscles of the neck to unite with one de- rived from a branch of the subclavian, thus making a short route between the subclavian and the external carotid; the blood can flow in this indirect way to the head if the external carotid be ligated.
PRINCIPAL ARTERIES OF THE TRUNK
The thoracic aorta extends from the fourth dorsal vertebra to the diaphragm (Fig. 135).
Branches. — Intercostal, n pairs, to the intercostal spaces; bronchial to lung tissues;1 pericardial to pericardium; esophageal to esophagus, and mediastinal to glands and tissues between the lungs (in the mediastinum, p. 365).
Note. — These aortic intercostal arteries run rather more than half way to the front, in grooves under the borders of the ribs, accompanied by inter- costal nerves and veins to meet intercostal branches of the internal mammary.
The abdominal aorta extends from the opening in the dia- phragm to the body (lower border) of the fourth lumbar vertebra—
a little above the level of the umbilicus (Fig. 134).
Branches. — Phrenic to the diaphragm and lumbar (4 pairs) to the abdominal wall, sacral to sacrum and rectum.
Branches to viscera: The celiac artery, dividing into gastric, for the stomach; hepatic, for the liver;2 splenic (or lienal), for the spleen.
Superior mesenteric, to the small intestine and these parts of the large intestine, namely — cecum, ascending colon, transverse colon.
Inferior mesenteric, to the remainder of the large intestine, namely — descending colon, sigmoid colon, rectum.
Two renal arteries, to the kidneys.
Adrenal arteries, to the adrenal bodies.
The ovarian arteries, to the ovaries, or the spermatic arteries to the testes.
1 Bronchial arteries have very little to do with respiration; they are the nutrient arteries of the lungs.
2 The hepatic circulation is a double one: Both venous and arterial blood enter the liver. The portal vein (with products of digestion for the liver to work over) and the hepatic artery (with the oxygen with which this work is to be done) enter together through the portal fissure. (The venous blood of both leaves the liver by hepatic veins, page 209.)
ABDOMINAL AORTA
IQ7
The ovarian artery runs downward into the pelvis and passes between the layers of the broad ligament to the ovary (p. 201), freely supplying it and the Fallopian tubes. It ends by anasto- mosing with the uterine artery (Figs. 134, 138).
Cystic artery
Hepatic duct
Cystic duct
Common duct
Portal vein
Gastro-duodenal branch
Superior pyloric branch
Hepatic artery
Right suprarenal vein
Inferior suprarenal artery
Renal artery
Renal vein
Inferior vena cava Kidney
Right spermatic vein :— -
Right spermatic artery Quadratus lumborum
muscle
Right lumbar artery and left lumbar vein Ureteric branch of spermatic artery
Middle sacral vessels
Left lobe of liver
Esophagus , cut. Left phrenic artery
Right phrenic artery Superior suprarenal Gastric artery Inferior suprarenal Splenic artery
Left phrenic vein Left suprarenal vein Superior mesenteric artery
Kidney
Ureteric branch of rena
Left spermatic vein
Ureter
Left spermatic or ovarian artery
Inferior mesenteric artery Ureteric branch of spermatic
Ureteric branch of common iliac
Common iliac artery
External iliac artery Hypogastric
FIG. 134. — BRANCHES OF THE ABDOMINAL AORTA. — (Morris.) Note that the right common iliac is longer than the lejt.
The spermatic artery runs downward and along the brim of the pelvis to pass out through the inguinal canal with the spermatic cord; it continues downward in the scrotum to supply the testes.
Special notes. — The superior mesenteric lies between the layers of the mesentery. The inferior mesenteric lies partly in the left meso-colon; it
198
ANATOMY AND PHYSIOLOGY
terminates as the superior hemorrhoidal in the upper part of the rectum (Fig. 137).
The gastric artery follows the lesser curve of the stomach, and is frequently called the coronary artery. The hepatic and splenic both send large branches to the greater curve of the stomach, and also to the pancreas and duodenum before reaching the liver and spleen.
Superior vena cava
V. azygos major
Veins
Inferior vena cava
FIG. 135. — COURSE OF THORACIC AND ABDOMINAL AORTA. — (Morris.}
The abdominal aorta divides (bifurcates) at the lower border of the fourth lumbar vertebra into the right common iliac and the left common iliac (Fig. 134).
The two common iliac arteries diverge and when they reach the sides (right and left) of the lumbo-sacral joint, each divides into hypogastric (or internal iliac) and external iliac (see Fig. 134).
The hypogastric artery passes into the pelvis and gives off
PELVIC ARTERIES
199
branches which supply the parts within and without the pelvic wall, including the perineum, and all of the pelvic viscera except the ovaries. (Branches to the exterior of the pelvis pass through the sciatic and obturator foramin.)
Visceral branches. — Middle hemorrhoidal, to the rectum.
Vesical (two) to the bladder.
. Mesenteric
vein
Cecum
Appendix
Small in- testine
FIG. 136. — SUPERIOR MESENTERIC ARTERY AND VEIN. — (Morris.} Supplying the whole of the small intestine, and about one-half of the large intestine.
Uterine to the uterus. Vaginal (several) to the vagina.
The uterine artery (Fig. 138) passes between the layers of the broad ligament to the cervix of the uterus, then runs upward along
2OO
ANATOMY AND PHYSIOLOGY
the side of the body, supplying it freely with blood, and anastomos- ing with the ovarian artery.
The arteries of the organs in the lower part of the pelvis are numerous. There are: three (or four) vaginal arteries, three (or more) vesical arteries, three or more hemorrhoidal arteries, all derived from the hypogastric or its branches, except the superior hemorrhoidal which is the terminal portion of the inferior mesenteric.
Right iliac artery
Middle sacral
Colic artery
Iliac vein Sigmoid vessels
Superior hemorrhoidal
Rectum
FIG. 137. — INFERIOR MESENTERIC ARTERY. — (Morris.} Supplying a portion of large intestine only, ending as hemorrhoidal.
There are also two perineal arteries.
These all anastomose freely with each other and with other arteries, so that a wound in this region is followed by an abundant flow of blood from more than one vessel.
Note. — The hypogastric arteries in the fetus are large. After giving off their branches they turn upward to the umbilicus where
EXTERNAL ILIAC ARTERY
201
they leave the body of the child, and become the two umbilical arteries twining around the umbilical vein in the umbilical cord. After birth, these portions of the vessels no longer transmit blood but dwindle to fibrous cords lying close to the anterior abdominal wall (p. 356).
Uterine Branch to round branch ligament
Fimbriated extremity of Fallopian tube
Ovarian artery Branches of ovarian art.
Cervical
branch of
uterine artery
Uterine artery ypogastric artery
Vaginal arteries
Azygos artery of vagina
FIG. 138. — UTERINE AND OVARIAN ARTERIES.
(Uterine, a branch of hypogastric; ovarian, a branch of aorta. Note the location of the ureter. — (Morris.}
PRINCIPAL ARTERIES OF THE LOWER EXTREMITY
The external iliac distributes its branches almost entirely to the lower extremity. It is about four inches long and follows the brim of the pelvis to the inguinal ligament where it becomes femoral.
Collateral circulation. — The inferior epigastric branch of the external iliac anastomoses with the superior epigastric branch of the internal mammary, in the substance of the rectus muscle, thus making an indirect route from the arch of the aorta to the iliac vessels if the abdominal aorta or iliac artery be ligated.
202
ANATOMY AND PHYSIOLOGY
Anterior tibial nerve
Anterior tibial artery
• Gluteal n.
Sciatic n.
Popliteal artery Tibial n.
Peroneal n.
Ant. tib. artery
Tibial n.
Post. tib. artery
FIG. 139. — THE FEMORAL ARTERY. FIG. 140.— THE POPLITEAL ARTERY.
THE VEINS 203
The femoral artery (Fig. 139) is a continuation of the external iliac, passing through the femoral trigone and the adductor canal to the popliteal space,1 where it becomes the popliteal artery. Its branches supply the skin and fascia of the lower abdomen and external genital organs, and all structures of the front and sides of the thigh. The largest branch is called the deep femoral, which lies close to the medial side of the femur and gives three perforating branches to pass through the adductor magnus muscle and supply the back of the thigh.
Note. — The femoral vein is on the medial side of the femoral artery until it reaches the popliteal space.
The popliteal artery is a continuation of the femoral, beginning at the end of the adductor canal (the opening in the adductor magnus) and running through the popliteal space. Its branches supply the boundaries and floor of the space and the knee-joint; it divides into anterior and posterior tibial arteries (Fig. 140).
The anterior tibial (Fig. 139) comes forward between the tibia and fibula, supplying the front of the leg; it then becomes the dorsalis pedis (upon the dorsum of the foot) , ending between the first and second toes. The anterior tibial passes in front of the ankle-joint, with the long tendons of the toe muscles.
The posterior tibial (Fig. 140) supplies the back of the leg and sole of the foot. It lies between the calf muscles and the deep muscles, and runs behind the medial malleolus, dividing then into medial and lateral plantar arteries for the medial and lateral por- tions of the sole, or plantar region (Fig. 141)
The Veins
All veins2 run toward the heart.
Beginning as very small vessels formed by the union of capil- laries, they unite and reunite until they make two sets of larger vessels called the deep and superficial veins.
The deep veins accompany arteries, being enclosed in the same sheath with them, and receiving veins corresponding to the branches of these arteries. Arteries of medium size usually have
1 See p. 371, Popliteal Space.
8 The names of all of the veins are given in tabular form on page 379. Only the principal ones are here described.
2O4
ANATOMY AND PHYSIOLOGY
two companion veins (or venae comites) ; large ones have but one, and it sometimes bears a name differing from that of the artery. (Example — internal carotid artery, internal jugular vein.)
The superficial veins do not usually accompany arteries. They lie in the superficial fascia, gathering blood from skin and fascia, and many of them are called cutaneous. Very frequently the deep and superficial veins communicate, through short con- necting branches.
PRINCIPAL VEINS OF THE HEAD AND NECK
Deep. — From the deep face and cranial cavity; they empty into the internal jugular vein (Figs. 127, 145).
The internal jugular is a continuation of the transverse sinus (a venous channel inside the skull, which ends at the jugular fora- men). This vein lies on the lateral side of the internal carotid artery in the upper part of the neck, and further down at the side of the common carotid artery, with the vagus nerve between and behind them. (Fig. 127.) It ends by uniting with the subclavian vein. Superficial. — From the scalp, ear, and face, bearing the names of the arteries (usu- ally) ; they empty into the external jugular vein which opens into the subclavian.
There are many veins in the spongy bone be- tween the compact layers of cranial bones, and these communicate by emissary veins with the sinuses and also with the scalp veins.
FIG. 141. — DEEP AR- TERIES IN SOLE OF FOOT.
i, Medial plantar; 2, lateral plantar. — Holden.}
PRINCIPAL VEINS OF THE UPPER EXTREMITY
Deep. — From the hand and wrist; they form ulnar and radial veins (running with arteries of the same name) which unite to form brachial veins.
The brachial veins in turn unite to form the axillary, and the axillary becomes subclavian (Fig. 126).
SUPERFICIAL VEINS
205
FIG. 142. — SUPERFICIAL VEINS, UPPER EXTREMITY.
FIG. 143. — SUPERFICIAL VEINS, LOWER EXTREMITY.
206
ANATOMY AND PHYSIOLOGY
The external jugular vein empties into the subclavian at about the middle of the clavicula. It is easily seen through the platysma muscle.
Superficial. — From fore arm; groups of veins, both anterior and posterior, form two, called the basilic and cephalic, which empty into the axillary vein.
Median veins in front of the elbow con- nect the basilic and the cephalic (Fig. 142).
The subclavian, having gathered blood from the entire upper extrem- ity, unites with the internal jugular to form the anonyma vein; the an- onyma veins (right and left) unite to form the superior vena cava (Fig. 127).
The left anonyma vein is the longer of the two, since it must cross to the right side to join the right vein.
The Superior Vena Cava
The superior vena cava is formed by the union of the two anonyma veins. It lies on the right side of the arch of the aorta, and opens into the right atrium of the heart (Fig. 126).
Great
or long
saphena
vein
VEINS OF THE THORAX Blood from all of the intercostal veins (except in the first space) finally reaches the great azygos vein, which opens into the superior vena cava (Fig. 135, azygos major).
The blood of the heart itself is returned directly to the right atrium by a coronary vein called the coronary sinus. All other thoracic organs return their blood to azygos veins and these to superior vena cava.
FIG. 144. — SUPERFICIAL VEINS, ANTERIOR.
VEINS OF LOWER EXTREMITY
207
SUMMARY
The venous blood from all structures above the diaphragm (except the heart) is returned through the superior vena cava to the right heart (right atrium).
PRINCIPAL VEINS OF THE LOWER EXTREMITY
Deep. — From the dorsum of the foot the veins form the anterior tibial veins ; from the sole of the foot, the posterior tibial.
The tibial veins run upward in the leg and unite to form the popliteal, which con- tinues as the femoral, and these two veins receive others corresponding in name to the branches of the arteries which they accompany.
Superficial. — From the lateral part of the foot and leg, by the small saphena vein, to the popliteal (Fig. 143).
From the dorsum and medial part of the foot and leg by the great saphena vein to the femoral, passing through the oval fossa in the fascia lata, below the inguinal ligament (Fig. 144). The femoral vein becomes external iliac.
VEINS OF THE PELVIS AND ABDOMEN FIG. 145. — SHOWING
FORMATION OF THE LARGE The veins of the pelvic organs are VEINS.
large and numerous.
In the vaginal walls and around the subclavian; 5,6, int. and evt.
. f . . , . jugular veins; 8, inferior
lower end of the vagina, also in the rec- vena cava; 14, common iliac
turn especially, they form close networks or plexuses which when wounded bleed profusely. The veins of the anal canal are prone to become con- gested and assume a varicose condition constituting hemorrhoids. The pelvic veins empty into the hypogastric, and the hypo- gastric and external iliac veins unite to form the common iliac.
208 ANATOMY AND PHYSIOLOGY
The right and left common iliac veins unite to form the inferior vena cava (Fig. 134).
The Inferior Vena Cava
This is formed by the union of the two common iliac veins at the right side of the bifurcation of the abdominal aorta (p. 197)
FIG. 146. — SCHEME OF FORMATION OF PORTAL VEIN, BY VEINS FROM SPLEEN, STOMACH AND INTESTINES.
(level of the lower border of the fourth lumbar vertebra). It runs upward through the abdomen, on the right side of the aorta,
PORTAL CIRCULATION 2OQ
close to the spinal column, to pass through the diaphragm and enter the pericardium and right atrium of the heart.
From the abdominal walls the phrenic and lumbar veins open into the inferior vena cava.
From abdominal viscera the renal and adrenal veins open into the inferior vena cava.
The right ovarian and right spermatic veins open into the in- ferior vena cava; the left ovarian and left spermatic veins open into the left renal vein which carries their blood to the inferior vena cava.
The splenic (or lienal), gastric, and mesenteric veins form the portal vein, which is four inches long and enters the liver at the transverse fissure or porta (Figs. 112, 146).
THE PORTAL CIRCULATION
This is the circulation of venous blood through the liver. The portal vein bears the products of digestion from stomach and intestines; entering the liver at the porta or gate, it divides into branches which form an extensive network in its substance.
Having been distributed through these fine capillaries, the blood leaves the liver by the hepatic veins, which open directly into the inferior vena cava.
Vessels passing through the porta (or transverse fissure) of the liver:
Entering
Hepatic artery.
Portal vein.
Two hepatic ducts.
Lymphatics.
All of the hepatic veins leave the liver at the back, opening at once into a larger vein running to the heart (the inferior vena cava). The great quantity of venous blood which the liver contains gives to it its dark color.
SUMMARY
The venous blood from all structures below the diaphragm (except upper lumbar walls) is returned through the Inferior Vena Cava to the heart (right atrium).
THE FETAL CIRCULATION
The fetus is nourished by blood brought from the uterine (placental) arteries of the mother, through a special vessel called 14
210 ANATOMY AND PHYSIOLOGY
the umbilical vein. After circulating in the body of the child it is returned to the placenta by two special vessels called the umbilical arteries, branches of the hypogastrics. (They shrink to fibrous cords after birth, which may be seen on the interior surface of the abdominal wall.)
During intrauterine life the lungs do not contain air, therefore, the interchange of oxygen and carbon dioxid in the blood must be accomplished elsewhere. This also is brought about by means of the placental vessels.
Opening closed by tricuspid valve - Foramen ovale
Coronary sinus
Location of Eu-
stachian valve
FIG. 147. — INFANT'S HEART. Showing interior of right atrium. — (H olden.}
The plan of fetal circulation requires still other special pro- vision, namely:
The foramen ovale. — An opening in the septum between the two atria (Fig. 147). It closes after birth.
The Eustachian valve. — A fold of endocardium in the R. atrium (so placed as to direct the blood from the inferior vena cava through the foramen ovale). This remains after birth.
The ductus arteriosus. — A short trunk (1/2 inch long) which connects the pulmonary artery with the arch of the. aorta. This shrinks to a cord after birth.
The course of the blood is as follows: Arterial blood is brought through the umbilical vein which enters the body at the umbilicus, runs upward under the liver (giving branches to that organ) and terminates by opening into the inferior vena cava, just below the diaphragm. This blood flows at once into the right atrium of the heart, where it is guided by the Eustachian valve through
THE PLACENTA
211
FIG. 148. — THE FETAL CIRCULATION. — (Morris.}
212 ANATOMY AND PHYSIOLOGY
the foramen ovale into the left atrium; from there it passes into the left ventriculum and through the aorta, to be distributed.
The greater portion of this current goes to the head and upper extremities, from which it returns to the right atrium again and passes down into the right ventriculum; thence into the pulmonary artery, but not to the lungs (except a very small portion); it is delivered instead by the ductus arteriosus to the aorta (at a point where the arch begins to descend, and joins the small current already there, to supply the trunk and lower extremities.
The greater portion of this blood leaves the fetus before the lower extremities are reached, by way of the two umbilical arteries, and returns to the placenta for re-oxygenation; while that which does go to the lower extremities is later returned to the inferior vena cava to be again mixed with blood from the umbilical vein, on its way to the fetal heart.
The external iliac supplies the lower extremities before and after birth.
Notes. — The liver is the only organ to receive blood just as it comes from the mother; the baby's liver is very large. The head and upper extremities are next supplied, although with a slight admixture of venous blood (which came through the inferior vena cava) ; they are well developed. The pelvis and lower extremities receive but a small supply of venous with a slight admixture of arterial blood; they are not so well developed.
The placenta. — The placenta is formed in a portion of the lining membrane of the uterus, by an intricate arrangement of the uterine vessels of the mother with the umbilical vessels of the fetus. It is here that the umbilical arteries coming from the fetus end; and the umbilical vein going to the fetus arises. Here also the inter- change of gases and of waste and nutritive matter between fetal and maternal blood is carried on, in blood spaces of the placenta.
The umbilical cord connects the placenta and the fetus. It comprises the two arteries and the one vein, protected by a gelat- inous substance or " Wharton's jelly," in which they are embedded.
CHAPTER XII PHYSIOLOGY OF THE BLOOD
We have learned that the nutritious portions of the food are, after digestion, poured into the blood and circulated throughout the body; also that cell action results in waste which is returned to the blood. Again, that tissue changes are chemical in their nature and chemical action is accompanied by heat; this is imparted to the blood, which can in turn convey heat to other parts.
Here, then, are three important functions of the blood:
1. To convey food (including oxygen from the lungs) to the tissues.1
2. To convey waste (including carbon dioxide) from the tissues.
3. To equalize the body temperature. Add to these:
4. To provide water for dissolving waste substances to be removed from the body by skin, kidneys, lungs and intestine.
5. To be a medium for transporting internal secretions (page
263).
6. To furnish its own remedy for hemorrhage by bearing the factors of coagulation. (See page 217.)
(The blood is a source of water supply as well asfood supply for the body.)
The special functions of the blood cells have been outlined, namely: — The oxygen-bearing property of red cells and the phago- cytic power of the white.
Any irritation of the tissues is promptly followed by an increase in the blood and lymph supply of the part, and (if long continued) crowding of cells in the capillaries. The leucocytes put forth little prolongations of their substance which penetrate the vessel wall, and gradually the cells themselves work their way through. This causes a hardened or indurated condition which will soon disappear if not excessive, but with severe irritation the process goes on to inflam- mation (the cells crowding each other to death) and pus results.
It is due to the character of the capillary walls that the blood cells can migrate into the tissues (diapedesis). In case of bacterial
1 It must not be forgotten that oxygen plays an important part in tissue changes — hence the importance of the blood as an oxygen carrier.
213
214 ANATOMY AND PHYSIOLOGY
invasion, the leucocytes surround and absorb the offending organ- isms, thus protecting the body from the effects of their toxins. This they are doing continually because we are constantly taking bacteria of various sorts into our systems. So long as the number is not too great the phagocytes can take care of them; it is only when there are too many that they cannot be overcome.
Consisting as it does of a single layer of endothelial cells, the capillary wall also renders possible the interchange of fluids between the blood-vessels and the tissues. This interchange is accom- plished by the physical process of osmosis, which may be denned as the diffusion of two liquids or solutions through an intervening membrane.
Simple diffusion is the mixing of two liquids when poured together, to form a uniform solution.
Filtration is the passing of a liquid through a membrane or other substance for the purpose of removing some portion.
It is probable that all three processes go on in the tissues.
Clinical note. — Two methods of local treatment of inflammation are based upon the above-named conditions: (i) preventive; (2) remedial. By the application of ice to prevent the intensity of hyperemia which leads to destruction of the tissues, or by application of heat to cause dilation of sur- face vessels and relieve it. After tissue destruction has actually occurred ice is no longer useful.
References have been made to the salinity of the blood and normal saline solution, which is a solution of the same concentration as blood plasma. Several very important things are conditioned by the normal salinity of the blood: (i) The integrity of the corpuscles. They as well as plasma contain substances which give them a certain density. If the plasma were a fluid of lesser density, its watery portion would invade the corpuscle and injure or destroy it. If the plasma were of greater density, the water of the corpuscle would leave it and the cell would shrink. (The " diffusion streams " of osmosis would be set in motion in the effort to equalize the densities of cell and blood, the outer portion of cell protoplasm representing a membrane.) •
The subject of osmosis is considered on page 1 70.
Hypodermoclysis. — This is the injecting of a watery solution of certain salines into the fascia under the skin, for the purpose of adding fluid to the blood, by absorption from the tissue. From the preceding paragraph one understands why the fluid injected must be a normal — or physiologic salt solution — that is, it must be of the same density as the blood plasma. (The normal salt solution, better — physiologic salt solution, must con- tain nine-tenths of i per cent, of salines.)
BLOOD TRANSFUSION 215
3. Transfusion of physiologic salt solution, or injecting directly into a vein. A more serious measure. Here the blood stream is invaded at once and good or bad effects are caused promptly. Accuracy is essential, that the injected fluid should be exactly of the right density and that nothing else whatever should enter the vein, lest clot formation occur.
Why are saline fluids introduced into the vessels? (i) To restore volume to the blood and maintain proper tension in the ves- sels, thus assisting the action of the heart; (2) to secure the tis- sues from loss of water and injuries due to disturbances in osmotic pressure; (3) to insure the distribution of normal red cells; (4) to dilute the poisons which are not eliminated during processes of disease, as in uremia.
Direct transfusion of blood is accompanied by a special danger because it is possible that the blood cells of one individual may act injuriously upon those of another, causing disintegration or hemolysis of red cells. (See Glossary.)
The blood of the donor (the person who gives it) may be hemolytic to that of the patient; that is, it will cause hemolysis of the patient's cells. Still more to be avoided is the situation where the patient's blood is hemolytic to that of the donor. Fortunately this accident need no longer occur, since laboratory tests can be made which will insure the selection of a donor whose blood will agree with that of the patient.
Blood transfusion is resorted to after severe hemorrhage, also in certain diseases, as leukemia, in which the red cells are dimin- ished in number.
Rapidity of heart action does not necessarily move the blood any faster through the vessels, as the rapid heart is frequently a weak heart. Also the short cardiac cycle signifies that the diastole is shortened; the chambers cannot receive as much blood; conse- quently, less is sent out.
Another effect of the weak and rapid heart is to deprive it of proper resting time. It wears itself out.
Quite different is the normal acceleration of heart action in the course of muscular exercise; this really sends the blood more abundantly through the body. The auricles are well filled, the ventricles contract forcibly and the cardiac cycle, although short, is efficient.
Variations in the blood flow are influenced in the vessels by
2l6 ANATOMY AND PHYSIOLOGY
i)aso-motor nerves. By vaso-dilators the arterioles are enlarged, allowing a free passage of blood ; by the vase-constrictors they are made smaller, thus cutting down the quantity of blood in a given area. A certain balance of tone in the blood-vessel system is neces- sary to proper action of the heart and to the process of osmosis.
The moving blood current exerts a certain amount of pressure upon the vessel walls; this (in health) is normal blood pressure- estimated by the experienced touch, but far more accurately by instruments designed for the purpose, whereby the pressure in an accessible artery is recorded upon a graduated scale. The instru- ment is the sphygmomanometer of which there are various designs.
Blood pressure is increased by an increase in the effort of the heart, or in the resistance in front of it, or in the volume of the blood. On the other hand, pressure is diminished by diminished heart force, diminished resistance, diminished volume.
Arterial pressureis illustrated by the force of the stream spurting from the mouth of a severed artery. In a small vessel this is an in- terrupted force, giving the appearance of throbbing or beating in the stream. Venous pressure causes the blood to well up in a wound rapidly but with a steady flow. Capillary blood simply oozes.
The cause of blood pressure is the resistance in front of the, stream resulting from the constantly diminishing size of the arter- ies, reacting to the attempt to drive the blood through them.
Clinical note. — In the processes which lead to arterio-sclerosis the middle coat of the artery is affected, the loss of elasticity being the first element of failure. Long-continued high pressure is a common cause of arterio-sclerosis since it calls for increasing action of the muscle and elastic fibers in the tunica media and at last tires them out. The elasticity of the vessel wall is gone; it can no longer preserve normal tone; connective tissue thickening follows and stiffens the artery. Later, a uniform hardness may be caused and brittleness, of which a common result is rupture and hemorrhage. This may occur at any place, often in the brain, often in the muscles of the lower extremities.
Arterio-sclerosis also interferes with the interchange between the blood and lymph and the normal metabolism in the tissues.
A physiologic or normal high pressure is caused temporarily by a quickening of the circulation, as in vigorous muscle exercise: by nervous excitement, as fright, anger, joy, etc.
Pathologic or abnormal high pressure may be caused by poisons, either swallowed, or retained in the system from tissue waste, as
COAGULATION OF BLOOD
217
in fevers, or renal or thyroid disease. Low pressure is observed in conditions of depression, or in muscle exhaustion, or after exhaust- ing illness; in warm surroundings, etc., etc.
Blood pressure is easily influenced by the use of drugs. For example, nitro-glycerin lowers it by dilating the arterioles; strych- nia raises it by contracting them; these are familiar examples. Many more might be cited.
Hemorrhage is the escape of blood in quantity, from an injured vessel. Arterial hemorrhage flows in a forcible stream, bright scar- let in color; if from a small vessel it will be pulsating or intermit- tent in force; if from a vessel of medium size, the blood will gush with a sudden spurt which carries to a rather surprising distance.
Venous hemorrhage presents a steady flow of darker hue, rapidly accumulating in a wound.
Capillary hemorrhage is persistent oozing.
Coagulation of Blood
Blood which is exposed to the air at the usual temperature is seen to separate into distinct portions — a red, jelly-like mass and a transparent straw-colored layer which is thinner. The dark mass
FIG. 149.— DIAGRAM TO ILLUSTRATE THE PROCESS OF COAGULATION, i. Fresh blood, plasma and corpuscles. 2. Coagulating blood (birth of fibrin). 3. Coagu- lated blood (.clot and serum). — (Waller.}
is the coagulum, consisting of fibrin with corpuscles entangled in it. The fibrin is essential — no fibrin, no coagulation. The straw-col- ored layer above it is serum, which is plasma bereft of its fibrin and corpuscles (Fig. 149). This same process may occur at the mouth of a blood-vessel which has been cut or ruptured, if the stream be not too forcible, and it is nature's way of stopping the flow.
The serum, or clear, alkaline layer above the clot, contains aO of the constituents of plasma except fibrin and corpuscles. The proteins, sugars and fats in their various forms, in combina-
2l8 ANATOMY AND PHYSIOLOGY
tion with substances which were discarded by the tissue cells, are all represented, dissolved in the water of the serum.
It is serum which is found in the peritoneum, pleura, pericardium and other serous-membrane cavities, and which fills the raised cuticle when a blister " draws." Serum is the basis of exudates and indurations. Gases are absorbed by serum, carbon dioxide chiefly, with a little nitrogen and oxygen.
Fibrin by itself is a colorless, sticky protein substance, fibrous and elastic. It may be obtained from freshly drawn blood by whipping it with a glass rod or more quickly with small twigs. (This leaves a red fluid called defibrinated blood.)
Formation of fibrin. — Fibrin is derived from the fibrinogen of the blood by the action of an enzyme called thrombin.
Source of thrombin. — It is assumed that something has hap- pened to so affect the leucocytes and blood plates that they have liberated a special enzyme, thrombokinase, which causes the split- ting off of thrombin from the pro-thrombin of the blood. The rest follows: — thrombin acts upon fibrinogen, fibrin is formed, the cor- puscles are entangled, and coagulation is accomplished.
Diagram of change from fluid to coagulated blood.
Cor- I Red Red cells
puscles \ White (and platelets) . White cells
Fluid blood
Plasma
Thrombokinase I
f Prothrom- Throm- bin J bin.
Fibrinogin.
Fibrin
Coagu- lum.
Coagu- lated blood.
[ Serum Serum
The formation of thrombin takes place only in the presence of calcium salts. (Further than this, the salts are not essential to coagulation.)
For these processes to go on it is necessary that some unusual condition be present. As has been said, normal coagulation takes place upon expos- ure to the air. In order that the blood may be exposed to the air, the vein or artery which contains it must be wounded, the blood flowing over the injured tissues.
So simple a change from the normal condition as this, is evidently "unusual" enough to cause the liberation of thrombokinase from the leu- cocytes and blood plates and appearance of thrombin, and the rougher the edges of the wound or the more uneven the surface over which the blood flows, the more rapidly does coagulation take place.
But (we are told) if an artery or vein be opened in a clean cut with a sharp knife and the blood received in an oiled tube under oil (thus prevent- ing any possibility of friction), no coagulation follows; while the same blood poured into an unoiled tube can be made to coagulate rapidly.
CONTROL OF HEMORRHAGE 2IQ
The time required for coagulation is a matter of some im- portance from the clinical standpoint. The average normal co- agulation time of undisturbed blood is from two to four minutes for the beginning of the process and seven to eight for its com- pletion; these figures vary under certain circumstances. If the blood is received in a cool vessel without disturbance, coagulation takes place slowly, the corpuscles sink in the plasma, the red cells (being heavier) falling to the bottom while the white ones form a reddish gray layer immediately above, or a "buffy coat" as it is called, so that the clot appears in layers. Blood from inflamed tissues coagulates after this manner.
Does blood ever coagulate without exposure to the air; that is, within the vessels of the living body? Yes, in certain abnormal conditions. If the lining of the vessel wall is diseased or rough- ened, or injured — as by application of ligatures, or in the presence of bacteria, or when a foreign body is floating in the blood stream, —these all favor coagulation within the vessels. High body temperature and various chemical substances have a similar effect, —the presence of oxygen as well, or the admission of air.
If air finds it way into a vessel forming an air embolus, there is danger that it will induce coagulation upon reaching the uneven surfaces of the heart if not before. This is an unusual accident, but a possible one, consequently great care should be exercised when filling and using a hypodermic syringe. (The double accident of piercing a vein and injecting air would have to occur in order to do harm of this sort.)
Arterial blood coagulates more easily than venous. A stationary clot within a vessel is a thrombus; a moving clot is an embolus. A portion of a thrombus may be swept off in the stream as an embolus and, lodging at some distant point, will become a thrombus there.
Clinical note. — Phlebitis is inflammation of a vein. The blood within the vein coagulates, and the vein feels like a hard cord.
Coagulation does not occur in the blood of the capillaries nor within perfectly normal vessel walls in health, nor in blood with a deficiency of calcium salts.
A clot within a blood-vessel resembles the true coagulum but is not identical with it, being largely composed of platelets with fewer threads of fibrin. The white clot found in the heart at autopsy is mostly fibrin.
Control of hemorrhage. — Nature's way is by coagulation at the mouth of the vessel. To favor this, we seek to i. slow the current: by rest, by elevation of the bleeding part, by compression
220 ANATOMY AND PHYSIOLOGY
of the artery from which the blood comes (as a tourniquet applied above the wound), by compress and bandage over the wound. 2. To cause contraction of the vessels: by applying heat — hot water 118 to 1 20 — in a rapid stream if available, otherwise in hot com- presses, or cold — ice is best; by the use of adrenalin, and possibly by styptic solutions which cause a coagulum by chemical action. (Among domestic remedies, vinegar has a reputation.)
For internal hemorrhage, if of the head or upper part of the body elevate head and shoulders moderately, command rest. If in the pelvis or lower part of the body, elevate the foot of the bed, protect from excitement, secure rest. If from the lungs, elevate shoulders, forbid speaking.
In case of sudden and profuse bleeding, when the vessels are rapidly emptying themselves, bandage limbs to secure tension by driving the blood into a smaller area, and to lessen the demand upon the heart; prepare for hypodermoclysis, saline transfusion or blood transfusion.
Since capillary blood does not coagulate direct pressure and time are required for the control of capillary hemorrhage.
Opsonins and the opsonic index. — It is believed that the phago- cytic action of white cells is regulated by the presence in the blood of chemical substances (still undescribed) called opsonins, by which invading bacteria are prepared for absorption and digestion by the phagocytes. The measure of the power thus residing in the blood is expressed as the opsonic index. The opsonic index is high or low, according to the number of bacteria which the opsonins may assist the cells to dispose of.
There is some reason for thinking that a special opsonin exists for each kind of bacterium.
In addition to opsonins the blood contains enzymes, also various antibodies and immune bodies, which either protect the body from specific infections, or assist in overcoming invasions which have already occurred (see p. 214). Each separate poison or bacterium has its own antibody. The so-called internal secretions are also carried by the blood (p. 263).
CHAPTER XIII THE LYMPH SYSTEM. LYMPH CIRCULATION
The lymphatic system comprises an extensive arrangement of lymph vessels or lymphatics, and lymph nodes (or glands} — both deep and superficial (Fig. 150).
This system pervades the entire body for the circulation of lymph — a nutritive fluid derived from the blood. It is by this means that foods which have been absorbed from the digestive organs and poured into the blood are separated out for the use of the tissues and conveyed to them.
Lymph spaces. — Between the cells and collections of cells of every tissue, except cuticle, hair and nails, are found minute tissue spaces or lymph spaces, communicating freely with each other. There are also spaces around the smallest blood-vessels and nerves (called respectively perivascular and perineural spaces) . These all communicate with the beginnings of lymph-capillaries (just how, is disputed).
Lymph capillaries. — These resemble blood capillaries in that they have but a single coat (of endothelium). They permeate the tissues in every direction, forming a close network, from which lymph vessels or lymphatics originate by the uniting of small channels to form larger ones (as veins originate) .
Lymph vessels. — Are delicate and transparent, but have three flexible coats. (One elastic, two nbro-muscular.) They are pro- vided with valves, formed by folds of the lining at very short inter- vals, which give the appearance of beading to the vessels. This arrangement allows the lymph to flow toward the heart but pre- vents it from moving in the other direction.
The lymph vessels of the intestines have been called lacteals because of their milky appearance during the process of digestion, the whitish color being due to the presence of fat globules trans- mitted by the lymph capillaries of the villi. This fat-bearing lymph is called chyle.
221
222
ANATOMY AND PHYSIOLOGY
Within the tissues of the body the lymph vessels are too small to be seen by the naked eye, but they unite again and again to form larger ones (although still very small) which in some places may be seen entering or leaving glands, until finally two remain — the right lymphatic duct and the thoracic duct, which have a diameter of 3 or 4 mm.
FIG. 150. — LYMPHATIC VESSELS AND NODES. i and 2 are portions of the THORACIC DUCT. — (Sappey.}
Lymph is a transparent watery saline fluid with lymph cor- puscles floating therein. It contains nutritive substances for the tissues and waste matters derived from them.
The description of plasma applies very well to lymph, always keeping in mind that lymph is more watery and carries lymph cells while plasma bears blood cells; lymph coagulates but slowly and not so firmly, with a pale clot because of the absence of red cells.
The origin of lymph is primarily from the blood. The walls of the blood-capillaries allow a transudation of thin plasma or serum
THORACIC DUCT 223
into the tissue spaces, and this is the source of its nutritive principles. Waste matters are added as the result of the activities of the tissues themselves; they represent the "tissue waste" This fluid, con- veyed by lymph-capillaries to lymph-vessels, is carried to lymph glands, where it gathers the lymph corpuscles which float in it.
Lymph nodes or lymph glands are small round or oval bodies of a reddish color, varying in size from that of a pin head to a small bean, and intersecting the lymph vessels in certain regions of the body. They are numerous in the neck, axilla and groin, also in the thorax and abdomen.
A lymph gland is invested with a thin but firm capsule (fibro- muscular) which sends septa or partitions into the interior, to support the gland substance in small compartments. The gland (lymphoid or adenoid} substance lies loosely in this capsule and in the compartments, leaving spaces for the passage of lymph around the different portions and around the whole. It contains great numbers of young corpuscles, which are added to the lymph stream as it washes through the gland, and appear later as the lymphocytes of the blood.
Lymph is brought to the glands by afferent lymph vessels, usually several for each gland. After flowing through the various spaces in and around the gland substance, it leaves by efferent vessels, which unite to carry the stream on its way toward the large veins.
A specimen taken from an e/erent vessel and examined under the micro- scope will show a greater number of lymphocytes than one taken from an afferent vessel.
The largest lymph vessel is called the thoracic duct (p. 189). It is about 1 8 inches long, having an average diameter of a small goose-quill. It begins at the second lumbar vertebra, in a little pouch called the receptacle of the chyle (or receptaculum chyli) and runs up behind the aorta, through the diaphragm. It then con- tinues upward through the thorax to the level of the seventh cer- vical vertebra, where it arches over to open into the left sub- clavian vein (at the junction with the left internal jugular). Thus the lymph and chyle join the current of venous blood on its way to the heart for circulation and distribution.
The right lymphatic duct is a short vessel, a half inch in length, which opens into the right subclavian vein at the junction
224 ANATOMY AND PHYSIOLOGY
with the right internal jugular. Through this channel lymph alone joins the venous blood on its way to the heart.
Note. — The cavities of serous membranes, as peritoneum, pleura, pericardium and others, belong to the system of lymph- spaces, but of a special kind. They are surrounded by capillaries which communicate with them by tiny openings in the membrane, called stomata.
Like the venous blood current, lymph flows toward the heart. After the lymph vessels are formed and receive their contents from the tissues, they take a fairly independent course. The larger glands are found in the neighborhood of veins as a general rule but not in the same sheath; knowing the situation of the glands and bearing in mind that the actual lymph stream flows from the tissues toward the heart, their course is easily traced and is of interest and importance as a swollen lymph node gives a clue to the possible location of the cause.
SITUATION OF THE PRINCIPAL GROUPS OF NODES OR GLANDS
BELOW THE DIAPHRAGM
Lower extremity. — Popliteal, in the popliteal space, inguinal (important) at the oval fossa and along the inguinal ligament (Fig. 152).
Pelvis: External and internal iliac, with the external and internal iliac vessels.
Abdomen: Mesenteric, between the layers of the mesentery (about 150); lumbar, in front of the aorta and vena cava. These are numerous.
ABOVE THE DIAPHRAGM
Upper extremity. — Epitrochlear , above the internal epicondyle; axillary, under the axillary walls, and clavicular, along the sub- clavian vessels (Fig. 150).
The axillary glands are superficial, under the borders of the muscle boundaries; and deep around the axillary vessels. These are very important.
Head: Occipital, below the occiput; auricular, behind the ear; parotid, upon the parotid gland; submaxillary , under the angle of the jaw (Fig. 150).
NODES OR GLANDS
225
Lymph-nodes
Small saphena vein
Lymph- nodes
Lymph- nodes
FIG. 1 5 1 . — THE LYMPHATICS AND LYMPH-NODES OF THE LOWER EX- TREMITY, POSTERIOR.
FIG. 152. — THE LYMPHATICS AND LYMPH-NODES OF THE LOWER Ex~ TREMITY, ANTERIOR.
226 ANATOMY AND PHYSIOLOGY
Neck: Superficial cervical, near the external jugular vein; deep cervical, with the large vessels (carotid arteries and internal jugular vein.) (Important.)
Thorax: Mediastinal, with the vessels in the mediastinum;1 bronchial, with bronchial tubes and vessels — these are numerous.
Lacteals
Veins
FIG. 153.—! LACTEALS AND MESENTERIC GLANDS. — (Morris.}
COURSE OF THE LYMPH STREAM
BELOW THE DIAPHRAGM
Knowing the location of the glands, and remembering that lymph flows toward the heart, the course of the stream is easily understood.
From the lower extremity up through popliteal, saphenous, and inguinal glands to the external iliac, and thence to the lumbar glands.
From the buttock and anterior parts of the genital organs to the inguinal, external iliac, and thence to the lumbar glands.
In the deeper parts of the genital organs to the internal iliac, and thence to the lumbar glands.
From the pelvic organs or viscera to the internal iliac, and thence to lumbar glands.
The ovaries, tubes, and fundus of the uterus send their lymph directly to the lumbar glands, instead of first through the internal iliac.
From the abdomen, lymph from the abdominal walls flows to lumbar glands (sometimes indirectly), also from the kidneys and adrenals to the lumbar glands.
1 See page 365, The mediastinum.
LYMPHATICS OF THE MAMMARY GLAND
227
From intestines through mesenteric glands to the thoracic duct; from all remaining abdominal organs to the thoracic duct (except upper surface of the liver).
All lymph which flows through lum- bar glands runs to the thoracic duct, and through it to the left subdavian vein.
Note. — The lymphatics in the mesen- tery, coming from the small intestine, convey not only lymph but chyle also, which is light in color and gives to them a milky appearance, therefore their name, lacteals (Fig. 153).
ABOVE THE DIAPHRAGM, LEFT SIDE
From the left upper extremity through axillary and subdavian glands to the deep cervical glands, thence to thoracic duct.
From left head and neck, superficial : face and scalp, to occipital, submaxillary, superficial cervical, and then deep cervical glands. Deep : face, throat and neck, to deep cervical glands and thence to thoracic duct.
From the left thorax, walls and vis- cera (including left half of heart), to thoracic duct.
ABOVE THE DIAPHRAGM, RIGHT SIDE
From the right upper extremity
through axillary, subdavian, and deep cervical glands, to the right lymphatic duct (p. 228).
From the right head and neck through occipital, submaxillary, superficial and deep cervical glands, to right lymphatic duct.
From the right thorax, walls and vis- cera (including right half of heart), to right lymphatic duct.
Lymphatics of the mammary
gland. — Most of these empty into FlG- i54-— LYMPHATICS AND NODES
_ . OF UPPER EXTREMITY.
superficial and deep axillary glands;
a few pass through the chest wall to mediastinal glands; those
228 ANATOMY AND PHYSIOLOGY
of the nipple and areola of the two sides communicate with each other.
SUMMARY AND FUNCTIONS
The right lymphatic duct gathers lymph from the right upper extremity, right head, neck, thorax and thoracic viscera, and the upper surface of the liver.
The thoracic duct gathers lymph from all other parts of the body — that is, the left side above the diaphragm, and all parts below the diaphragm, except the upper surface of the liver. The two ducts empty into the two subclavian veins, and thus the lymph joins the blood current.
The Flow of the Lymph Stream. — This is maintained by the same forces which are concerned in the flow of blood in the veins — (i) the aspiration of the thorax; (2) the intermittent pressure and relaxation of surrounding muscles throughout the body; (3) the constantly lowering resistance in front of the stream as the vessels grow larger; (4) probably by the action of muscle-fibers in the walls of lymph vessels and the assistance of the numerous valves, by which they hold what they receive, never allowing the stream to fall back. Add to these general forces the special influence of the peristaltic movements of the alimentary tract; these must cause a rhythmic closing and opening of the lymph vessels which are the most active of any in the body, and in consequence, a large volume of lymph containing the products of digestion, is set in motion.
Clinical notes. — Certain conditions of disease in an organ or tissue are followed by enlargement of the nearest glands which receive lymph from that part. If the disease be not arrested, the glands next in order will suffer, and the next, and the next.
Disease of the mammary gland will cause swelling, first, of the superficial glands under the border of the pectoral muscle, and later of the deep axillary and clavicular glands. Mediastinal glands are sometimes affected when the upper portion of the gland is diseased.
Disease of the tonsils will affect the submaxillary and cervical glands.
Disease of the pharynx, the cervical glands.
Disease of the larynx will affect the cervical glands, and may affect the mediastinal and bronchial glands.
Disease of the upper extremity will cause swelling of the axillary glands.
Disease of the lower extremity will affect the saphenous group and the inguinal.
EDEMA EFFUSION 229
Disease of the external genital organs and lower end of vagina will affect the inguinal glands along the inguinal ligament.
Disease of the neck of the womb (cervix uteri) will affect iliac glands, while disease of the body of the womb (fundus uteri), or of ovaries or tubes, will affect lumbar glands.
The transmission of the causes of disease from one organ to another by the lymphatics is called metastasis; it is often seen to follow a malignant growth.
The lymph itself, as we have seen, is the medium between the blood and the tissues. It is only through the lymph that the blood can feed the tissues and receive the products of their metabolism. The thinness of the capillary wall allows this interchange between blood plasma and the lymph in the spaces around the vessels. The one place of exception is in the lungs. There, oxygen from the air passes directly into the capillary blood and Co2 from the blood, directly into the air of the lungs.
The process of osmosis has already been mentioned, in con- nection with food absorption and in considering the physiology of the blood (pages 170 and 214). It is by the forces included under this name that the nutritive substances circulating in the blood are delivered to the tissues and wastes are at the same time removed from them.
Clinical notes. — Edema is an accumulation of lymph in the tissue spaces. We have seen that an interchange between the blood and lymph capillaries is continually going on, the blood providing lymph, the tissues receiving it, abstracting nutriment and adding waste. This is not all returned to the capillaries, a portion is left in the spaces to be carried by lymph vessels to the two lymph ducts which convey it to certain large veins.
Should this balance of interchange be disturbed, the effect is evident at once. Whether the supply be too abundant or the outflow be obstructed the same result would follow — the tissues would be overwhelmed with fluid, causing edema.
Inflammation of serous membranes, if severe, results in the accumulation of lymph or serum in their cavities — this is an effusion.
Inflammation in the tissues themselves causes a local excess of lymph derived from the increased quantity of blood or hyperemia, induced by local irritation. The accumulation of excess lymph constitutes induration or hardening.
Hyperemia is evident to the eye when near the surface, by the redness and heat which it causes. The vessels become so crowded with cells that the blood can move with difficulty. Serum and corpuscles make their way through the vessel walls and fill
230 ANATOMY AND PHYSIOLOGY
the lymph spaces, which are still more crowded by the lymph with its corpuscles held back in the hardened tissues. If the invading microorganisms which have set up all the trouble are not too numerous, the phagocytes aided by opsonins will dispose of them. Then they and the entire accumulation in the tissues — remnants of cells and bacteria, fluids, etc., will be removed by way of the regu- lar lymph channels as the swelling subsides.
Clinical note. — The nurse becomes very familiar with the treatment of this condition of induration; for example — by the use of hot douches to assist the removal of a pelvic "exudate" by improving the circulation in the region and in this way favoring absorption. (A pelvic exudate is usually situated in the broad ligaments of the uterus.)
SUMMARY OF FUNCTIONS OF THE LYMPH SYSTEM
By the lymph, to present to the tissues their proper nutriment and to receive the waste products of their metabolism.
By the lymph spaces, to transmit the nutritive fluid from the blood to the tissues, and waste matters from the tissues to the blood.
By lymph capillaries and vessels, to convey lymph to the blood in the large veins.
By lymph nodes or glands, to give origin to lymphocytes, and to filter out and retain poisonous or injurious substances from the lymph stream.
CHAPTER XIV
PULMONARY RESPIRATION AND RESPIRATORY
ORGANS
Respiration is the term used to express the interchange of gases between the blood and the surrounding tissues, the gases being oxygen and carbon dioxide.
Pulmonary respiration takes place in the capillary system of the lungs. The interchange is between the blood and the atmosphere, or external air; hence, the process in the lungs is called external respiration.
The exchange which takes place in the capillaries of the tissues elsewhere is, on the other hand, called internal respiration. As this depends entirely upon the intake of oxygen by the lungs and the removal of carbon dioxide in the same organs, the use of the word respiration without qualifying, has come to signify pulmonary or external respiration, commonly termed breathing.
Inspiration is the act of drawing air into the lungs; expira- tion is the act of expelling it. An inspiration and an expiration together constitute a pulmonary respiration.
By air is meant the atmospheric air by which we are surrounded. It consists principally of the two gases, oxygen and nitrogen, one hundred parts by weight of air containing a little more than twenty of oxygen and a little less than eighty of nitrogen, or, in the pro- portion of one of O to four of N, roughly speaking. It is the oxygen which is the essential part of inspired air.
The respiratory organs are the nose, pharynx, larynx, trachea, bronchial tubes, and lungs, with the thorax and its muscles, in- cluding the diaphragm; and the pulmonary blood-vessels. These organs constitute the respiratory apparatus and they include the respiratory tract, which is a series of channels or air-passages at the termination of which the air comes into contact with the respiratory epithelium.
The nose. — -The external nose is a framework of bone, cartilage and skin. The dorsum is formed by the meeting of the lateral
231
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ANATOMY AND PHYSIOLOGY
surfaces in the median line. Each lateral surface terminates below in the wing of the nose — ala nasi. The alae are flexible and move- able. The part that is supported by the nasal bones is the bridge of the nose. The nostrils are the expanded portion; they contain no bones, but small plates of cartilage instead, which are moved by little muscles, therefore, they may be expanded or contracted.
Immediately within the margins of the nostrils are the vestibules; each vestibule terminates within the tip of the nose in a small pouch, the ventricle. The nostrils and vestibules of the right and left sides are separated by thin cartilages forming a mobile septum (columna).
JJ
FIG. 155 — .NASAL CAVITY ANDN ASO-PHARYNX. — (From Dealer's Surgical Anatomy.} b, Superior turbinal; a, superior meatus; c, middle turbinal; s, middle meatus; d, inferior turbinal; «, inferior meatus; g, i,j, tongue; k, hyoid bone; p, q, r, sphenoid bone and sphenoidal sinus; t, naso-pharynx; v, hard palate (floor of nose). The remaining references are explained in another chapter (p. 136).
Their internal margins are provided with stiff hairs to arrest particles of foreign substance in the inspired air.
The cavity of the nose is divided into the right andjeft cavities
THE LARYNX 233
or fossa by a partition called the septum, the anterior portion of the septum being formed by the triangular cartilage of the nose, the remaining portion by bones — the vomer and the vertical plate of the ethmoid (Fig. 26). The openings upon the face are the nares (anterior nares) and those at the back (looking into the nasopharynx) are the choance (posterior nares) .
On the lateral wall of each nasal cavity are three turbinated bones or shells (conchae), and three spaces or passages directly underneath them, named as follows: the superior meatus (or passage) beneath the superior concha (or shell) ; the middle meatus beneath the middle concha; and the inferior meatus beneath the inferior concha (Fig. 25). The upper part of each fossa is the olfactory part; all below that is the respiratory part.
Breath is the air from the lungs with all that it contains; breathing, then, is producing air which has been passing through the lungs.
The nasal cavities and all of the sinuses which communicate with them are lined with mucous membrane, which by the mucus on its surface, prevents the drying effect of the air upon the pas- sages, arrests foreign particles, and moder- ates the temperature of the air on its way to the lungs. As an organ of respiration, the nose is important because nasal respira- tion moistens, filters and warms the air we FIG. 156.— CILIATED EPI- breathe. TBSLTU*.— (Stirling.
The mucous membrane of the nasal fossae is called the Schneiderian mem- brane. It is ciliated in the respiratory part. In the olfactory part the olfactory cells are found, which receive the impressions leading to the sense of smell. For the nose as an organ of the sense of smell, and of voice, see pp. 326 and 345.
THE PHARYNX
The pharynx is the space behind the nose, mouth, and larynx. Its use is to transmit air from the nose, and food from the mouth. As an air-passage it is included with the respiratory organs. (The air passes from the nose through the pharynx to the larynx.)
THE LARYNX
The larynx is situated below the hyoid bone, in front of the pharynx, and projects slightly forward in the neck. It is con-
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ANATOMY AND PHYSIOLOGY
structed of fibre-cartilages connected with each other by ligaments and lined by mucous membrane. The largest fibre-cartilage is the thyroid, which forms the prominence of the larynx known as "Adam's apple." Below the thyroid is the cricoid cartilage, shaped like a seal ring, and placed with the broad part at the back, where two small pyramid-shaped cartilages rest upon it; they are the aryte- noids. These are all connected by gliding joints. (Other cartilages, very minute, are not mentioned.)
The epiglottis is a leaf-shaped flexible cartilage extending upward from the thy- roid in front, and resting against the base of the tongue. During swallowing this is bent backward over the entrance of the larynx by the action of small muscles, to allow the food to pass over it into the esophagus. (For the Larynx, the Organ of the Voice, see page 344.)
FIG. 157. — INTERIOR OF LARYNX (LEFT SIDE RE- MOVED) . — (Sappey) .
2, Epiglottis; 5, so-called "false vocal cord"; 9, vocal band; 13, thyroid cartilage; 14, arytenoid cartilage. The other figures refer to parts not mentioned in the text.
THE TRACHEA
The trachea is a flexible tube about one -inch in diameter and four and one- half inches long, extending downward from the larynx to the level of the fourth thoracic vertebra. It is fibrous and elastic, and stiffened with rings of cartilage which are incomplete at the back; unstriped muscle fibers take their place, constituting the tracheal muscle.
The tracheal muscle makes the tube soft where the esophagus lies next to it,_and by the action of its fibers varies the size of the trachea.
The trachea divides into two branches called bronchi. The right bronchus is one inch long; the left is two inches long (it passes under the arch of the aorta) .
The bronchi divide into branches called bronchial tubes which subdivide again and again until the smallest tubes, called bron- chioles, are formed. These lead to the spaces called alveoli, and the air cells clustered about them.
THE LUNGS
235
The bronchi and larger bronchial tubes are like the trachea in structure, consisting of fibrous and elastic tissue with incomplete rings of cartilage. In the smaller tubes the rings become irregular plates or discs, and in the bron- chioles the cartilage is absent altogether. The walls are here very thin and contain circular muscle fibers (non-striated), the bronchial muscle.
The entire tract from the trachea down to the air cells is lined with mucous membrane, bearing ciliated epithelium (Fig. 156) as far as the smallest tubes.
Thyroid cartilage
Cricoid cartilage
Left bronchus
FIG. 158. — LARYNX, TRACHEA, AND BRONCHI. — (Morris, modified from Bourgery.)
p The cilia of the air passages are fine hair-like projections from the surface; they have a waving motion, exerted forcibly in a downward direction.
THE LUNGS
The lungs are two in number, right and left, situated in the right and left sides of the thorax, occupying the space enclosed by the ribs (not that portion between the sternum and the spinal column). They resemble a flattened cone in shape, the apex
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ANATOMY AND PHYSIOLOGY
extending one inch above the clavicle, the base resting upon the diaphragm. The right lung is broader and shorter than the other,
but it has three lobes, upper, middle, and lower. The left lung has two lobes.
Note. — The left lung is narrower than the right and does not cover the apex of the heart, otherwise it would be exposed to the motion of the "heart beat."
The lung substance consists of branches of the bronchi and their divi- sions down to the bronchioles, and the spaces terminating in air-cells. These structures are surrounded by blood- vessels, nerves, and lymphatics, grouped together in lobules, supported by fine
FIG. 159. — CLUSTERS OF AIR-CELLS. — (Hoi den, from Kolliker.)
fibre-elastic tissue and wrapped in pleura.
Each bronchiole terminates in a lobule.
The root of the lung is composed of the large bronchial tubes, blood- vessels, and nerves (Fig. 160).
The bronchial tubes are the primary divisions of the bronchi; the blood-vessels are — first, the bronchial ar- teries for the nutrition of the lung substance; second, the pulmonary arteries which form a fine network of capil- laries around the air-cells, third, the bronchial and pul- monary veins. They enter and leave the lung at the hilum — a depression on the medial surface.
FIG. 1 60. — THE LUNGS WITH HEART BETWEEN THEM.
THE PLEURAE
Each lung is covered (except at the root) by a thin transparent sac of serous membrane called the pleura. One side of this sac is
THE PLEURA 237
closely applied to the lung, forming the pulmonary pleura; the other side fits as closely to the ribs, forming the costal pleura. Within the sac is a small quantity of serous fluid (secreted by the endothe- lium of the pleura), which prevents friction when the ribs move and the lungs expand or contract.
Although the bony thorax is bounded above by the first rib, the thoracic cavity extends an inch above the rib on each side, bounded by an expansion of the costal pleura and lodging the apex of the lung.
R. mammary artery
L. phrenic nerve
m ma ^Mom^BHH I^MI <m
R. phrenic nerve
FIG. 161. — THE PLEURAL SACS.
The dotted lines indicate the pleural sacs, with space between the layers.
(H olden.)
Clinical note. — If the pleura becomes inflamed the quantity of fluid diminishes and the surfaces rub together, causing acute pain and a fine crackling sound as of friction. This condition is pleuritis or pleurisy.
Resume. — In respiration, or the act of breathing, the inspired air enters the nasal chambers, passes through the naso-pharynx, oro-pharynx, larynx, trachea, bronchi, bronchial tubes, and bron- . chicles, to the alveoli and air-cells or air vesicles.
THE PHYSIOLOGY OF THE RESPIRATORY PROCESS
The function of the respiratory apparatus is first, to accom- plish an interchange in the lungs between the oxygen of the air and carbon dioxide of the blood, in other words — to bring nutri- ment to the blood and to remove waste from it.
238 ANATOMY AND PHYSIOLOGY
We have seen how the blood returns from the digestive organs laden with food which is to be distributed throughout the body, where the products of digestion are made over in the tissues by a series of changes in which oxygen plays an essential part. The source of the oxygen for this purpose is the air we breathe. It passes through the air vesicles and the capillary walls into the blood, thence into the lymph spaces and tissue cells.
The gas called carbon dioxide (resulting from tissue action) is brought by the blood to the lungs; passing through the capillary walls and the air vesicles, it is exhaled in the breath and thus re- moved from the body. Consequently, respiration is a process not only of nutrition but of elimination as well.
This interchange is accomplished in part by the physical process of diffu- sion of gases. (The epithelium of the air vesicles is thought to have a special function to this end, and is called respiratory epithelium:}
By inspiration we take air, with its oxygen, into the lungs; by expiration we expel it with carbon dioxide, small quantities of ammonia and organic waste matter, and moisture.
This important process is made possible by the movements of the thorax as follows:
In inspiration. — The external intercostal muscles elevate the ribs and spread them apart, increasing the width of the chest ;j the diaphragm contracts, pulling down its central tendon and thus increasing the depth of the chest; the lungs expand and receive the in-drawn air. This is the active phase of a respiration.
In expiration. — The ribs fall easily back into place, assisted by internal intercostals and abdominal muscles; the diaphragm relaxes, returning to its dome shape, and the air is pressed out. This is the passive phase of a respiration.
These acts are performed, in health, with regularity, that is, rhythmically. The number of respirations in a moment varies from about 40 in the newly born to 18 in the adult. Normal respiration is slowest when one is lying down or when sleeping. The rate is increased during physical exercise or by emotion, and in visceral inflammations, as pneumonia, pleurisy, peritonitis, etc., also in fevers generally.
1 The Pectoralis Major and some others assist in deep breathing or forced inspiration.
RESPIRATION 239
Average respiratory rate at different ages:
At one year 30
" six years 25
" twelve years 20
Soon after this age, the normal proportion between the number of respirations and the pulse rate, is as one to four.
Nasal breathing is the natural method of introducing air into the respiratory passages; mouth breathing is obstructed breathing and unnatural. The obstruction is oftenest found in the naso- pharynx, due to adenoid growths or hypertrophy of the naso- pharyngeal tonsil. Enlarged tonsils obstruct the oro-pharynx; a deflected septum (p. 27) or hypertrophied turbinal bone may encroach upon the nasal passages. In all of these conditions mouth breathing is called to the aid of defective nasal breathing.
Nasal breathing favors the development of the air sinuses or resonance chambers which communicate with the nose. (See The Voice, p. 344.)
Important note. — Mouth breathing leaves the chambers undeveloped, the voice has a decidedly nasal quality and, owing to the flattening of the facial surface of the maxilla (because the antrum is small) the alveolar process is unduly prominent. (Many bad effects of mouth breathing might be cited if space and time were available.)
The normal respiratory sound has been well compared to the rustling of leaves when the gentlest of breezes is blowing through them.
The tidal volume of air is that which constitutes a respiration without effort. The air which is added by an effort of inspiration (or by forced inspiration) is complemental air. That which is expelled by effort in addition to a normal expiration, is reserve air. A certain volume always remains in the depths of the cells in order to prevent their entire collapse — this is called residual air; it is changed gradually and constantly.
The organs concerned in respiration must be obedient to a- con- trolling nerve center common to them all, in order that they may act together for the one purpose. This is called the respiratory center; it is situated in the brain (in the oblongata).
240 ANATOMY AND PHYSIOLOGY
Normal respiration is, as we have seen, a rhythmic process; that is, the demand for oxygen is met by the act of inspiration; this demand satisfied, the passive chest walls sink back into posi- tion and the lungs retract, but only for an instant; another demand is followed by another inspiration and the passive expiration, regularly repeated ad infinitum.
What causes the respiratory center to make this demand? It is believed that the CO% in the blood, which is flowing to the lungs from the heart, is the normal direct excitant of the center. Many facts in our experience are explained by this theory; e.g., after several deep breaths the blood is rich in oxygen and one is content to suspend respiration, but after a few seconds the oxygen is con- sumed, the blood is charged with GO2 and the act of inspiration is at once stimulated.
The same theory is advanced to explain the cause of the new- born infant's first inspiration. With the cessation of the blood stream from the mother, oxygen is lost, C02 accumulates and inspiration follows.
In infancy and youth the rapid tissue changes of the growing body cause, in the same manner, a higher rate of respiration than in adult life. So with muscle exercise, which sends the blood coursing through the body to gather its load of C02.
Whatever causes rapid circulation causes rapid breathing. This is the explanation of the increased respirations of fever.
Reflex stimuli of the respiratory center are without number; the whole sensory apparatus affects it. Exposure to cold (low temperature of the air) or sudden contact with a cold body, for example the chill of cold water, causes a gasp or forced inspiration, which is soon followed by rapid breathing. (The sudden contact of the baby's body with the surrounding air is probably a power- ful excitant to the first respiration, perhaps the principal one, and often has to be aided by cold sprinkling.) Sharp recurring pain, emotions of pleasure, anger, surprise, etc., all have a similar effect.
Slowing of respiration follows an accumulation of O; after a few deep breaths one may refrain from inspiration for a time (for -from 40 seconds upward) according to training, the blood using the residual air after the O of the tidal and complemental supply is exhausted.
Warmth disposes to moderate breathing; a sense of physical
RESPIRATION AND BODY HEAT 241
comfort does the same; reflex stimuli are absent, the system is relaxed and all processes slow down.
The breathing of normal sleep is slow and regular. Depressing emotions tend to diminish the frequency and disturb the rhythm of respiration. (Witness the "long breath" and frequent sighing of the morbidly depressed person.)
In certain cerebral and other conditions, the respiratory center seems to be dulled, so that it responds sluggishly or irregu- larly, as in meningitis and apoplexy; also in disease of the myocardium.
Action of Drugs. — Certain drugs are called respiratory stimu- lants. Among the best known are strychnine and atropine. Others are respiratory depressants: as opium (in sufficient dose), ether, chloroform, and many others.
Respiration is one of those involuntary processes in the body which we may voluntarily regulate. We may, whenever we choose, modify the rate and depth of respirations, breathing slowly or rapidly, deeply or superficially at will. We may even cease to breathe for a time, because the residual air always present will sus- tain the demand for oxygen temporarily, although soon we lose con- trol and respiration will proceed with or without any effort of ours.
Respiration contributory to body heat by providing oxygen for tissue change in all parts of the body.
Muscle tissue is constantly at work; by rapid oxidation the muscles generate much heat, but only so long as the respiratory organs keep pace with the demand for rapid breathing.
It is natural to breathe more rapidly as well as more deeply on a cold day, because a low temperature of the surrounding air stimulates (reflexly) the various activities of the body to meet the call for warmth, and the respiratory process must be among the first to respond. (The subject of body heat is considered in Chapter XVIII.)
The tissues which are most active require most oxygen. Con- sequently we can create a demand and obtain a supply by volun- tary muscle exercise in good air, thus feeding the blood and through it the viscera where also much heat is generated, and the entire body, with this most important element for tissue change.
Summary. — Respiration is a nutritive process, an eliminative process and a contributing source of body heat.
16
242 ANATOMY AND PHYSIOLOGY
SPECIAL MODIFICATIONS OF RESPIRATORY MOVEMENTS
Rapid breathing is called hyperpnea.
Temporary cessation of breathing is called apnea.
Labored breathing is dyspnea.
Dyspnea follows any interference with the interchange of gases in the lungs. It may be caused by diminishing the entrance of oxygen, or by increasing the CO2. It is usually due to imperfect circulation in the pulmonary vessels.
Asphyxia is the condition resulting from a complete cutting off of oxygen, or an excessive increase of carbon dioxide. It may be sudden or gradual, but if unrelieved, ends only in death.
The change of color noted in the face of one suffering from dyspnea, and still more from asphyxia, is due to the accumulation of carbon dioxide in the blood.
In Cheyne-Stokes breathing, a period of apnea is followed by respirations which are at first faint and shallow, then gradually increase in depth and rate until they become either normal or exaggerated, when they either cease abruptly or decline to another period of apnea. This may occur many times in succession, but is seldom constant. It is seen in the sleep of a patient with fatty heart, sometimes in the sleep of children apparently well; often in apoplexy.
Stertorous breathing is characterized by a loud snoring sound; it is unconscious and sometimes labored.
The production of artificial respiration is attempted by imitat- ing Nature's method. (See p. 238.) By elevating the arms the thoracic walls are spread, the lungs follow, air is drawn in. De- pressing the arms against the thorax presses the walls down, the lungs are compressed, air is expelled. In this manner not only is the air current set in motion in the lungs, but an additional stimu- lus is created by the expanding and subsiding of the lung cells. When expanded they call for expiration to relieve them, and when collapsed they demand inspiration to fill them. This is a physio- logic stimulus which is believed to be constantly felt by the lung tissue in health.
Internal respiration will be studied under Metabolism. Chapter XVIII.
VENTILATION
243
Ventilation. — The subject of ventilation is a broad one, since so many factors enter into the problem of securing it. The rate at which air should be renewed is influenced by the number of people in a room, also by the occupations carried on therein, as can be easily understood. Even in small rooms the quantity of air may be sufficient, if a constant current of renewal be secured. The well-known morning " closeness" of the air of a sleeping room is due to the fact that in the quiet of the night the ordinary air- currents are not present. It is the lack of oxygen rather than the excess of carbon dioxide which is felt and which is in reality the more serious.
Important Note. — The importance of fresh air in sufficient quantity cannot be over-estimated. One thousand cubic feet of space for each adult (equal to a room 10 feet in height, length and breadth), renewed about three times hourly, is not too much.
CHAPTER XV ELIMINATION. ORGANS OF ELIMINATION.
THE KIDNEYS
Having studied the Digestive, Circulatory and Respiratory Organs, or organs of nutrition, we will next consider those which are active in the removal of waste from the system or the Organs of Elimination. They are the kidneys, skin, liver and lungs, and to a lesser extent, the intestinal canal.
Of these, the kidneys alone are specially constructed for the function of elimination only. The skin, although mainly an organ of excretion (or elimination), has other uses beside (as will be seen in succeeding pages).
The liver and the lungs are included under this heading — the liver, because certain waste products are contained in the bile; the lungs, because they are agents for the removal of carbon dioxide. The intestinal tract is the avenue by which the gross waste material of the food is expelled, and at the same time it is the main avenue of entrance into the system of nutritive material. Therefore the lungs, liver, and intestine are found in both lists of organs, nutritive and eliminative.
THE KIDNEYS
The kidneys (renes) are the most important organs of excretion. They separate certain waste matters from the blood, in a definite form for removal from the body; this is their special function.
They are situated for the most part in the posterior lumbar region, just in front of the quadratus lumborum muscles, extending from about the tenth rib to within two or three inches from the crest of the ilium. They are shaped like a bean, about four or five inches long and one and one-half inches wide, with the concave border, or hilus, turned toward the spinal column; and they are imbedded in fat behind the peritoneum. This is the fatty capsule; outside of it a thin layer of fascia extends across both kidneys, being attached to the fascia in front of the lumbar muscles and lumbar spine. It is called the renal fascia.
244
STRUCTURE OF KIDNEY
245
The other abdominal organs are in front of or above and below the kidneys, so the natural result of this arrangement is that they are stationary, the only stationary organs in the abdomen, the others all move in respiration, digestion, defecation, micturi- tion, parturition.
The kidney is hollow, the cavity within being called the sinus. It is covered by & fibrous capsule which also lines the sinus.
Left kidney
Left ureter
Right ureter
FIG. 162. — THE KIDNEYS. (Morris.}
Structure. — A kidney is a mass of minute tubes, the uriniferous tubules lined with epithelial cells, which perform the real work of the organ. At the beginning of each is a bulb-like enlargement, indented to form a deep hollow (Bowman's capsule, Fig. 163) which encloses a tuft of renal capillaries. The capsule and vessels together constitute a Malpighian or renal corpuscle. As the tubule leaves the bulb it twists and turns many times and is called the convoluted tubule. It has a network of blood-vessels around it. The convoluted tube finally becomes straight, and at last several straight ones unite to form a collecting tube which opens into the sinus.
Malpighian corpuscles and convoluted tubes occupy most of the portion of the kidney near the surface, forming the cortex
246
ANATOMY AND PHYSIOLOGY
(or cortical portion). The straight or collecting tubes are grouped together into pyramids, pointing toward the interior and forming
the medullary portion. The apex of each pyramid pro- jects into the sinus, pre- senting the openings of sev- eral collecting tubes -(Fig. 164).
The cells which line this system of tubes do the work of excreting the urine from substances in the blood, thus relieving it of poisonous elements which would surely cause death if allowed to remain.
The urine is conducted from the kidney to the blad- der through the ureter, a slender musculo-fibrous duct about twelve inches
long, the upper end of which is enlarged and called the pelvis of the kidney. (It occupies the sinus.) It has a thin layer of muscle fibers and is lined with mucous membrane. The two ureters extend into the true pelvis to the base of the bladder, where they terminate about one inch apart.
The Urinary Bladder is the receptacle and reservoir for the urine and is situ- ated in the pelvis just behind the pubic bones; between them and the rectum in the male pelvis, between them and the vagina and uterus in the female pelvis. It is a non-striated muscular sac, lined with mucous membrane which lies in ir- regular folds when the sac is empty, but becomes smooth when it is filled. It has a covering of peritoneum above and posteriorly but not in front. The upper portion of the bladder is the summit or vertex; the
FIG. 163. — SCHEME OF THE RENAL OR MALPIGHIAN CORPUSCLE.
i. Interlobular artery. 2. Afferent vessel. 3. Efferent vessel. 4. Outer wall. 5. Inner wall. 6. Glomerulus. 7. Neck of tubule.— (Stohr.}
FIG. 164. — SECTION OF KIDNEY.— (Potter.}
THE URETHRA
247
lower part is the base or fundus. There are three openings in the bladder wall, two for the entrance of urine and one for expelling it.
The urine enters through the two ureters (Fig. 162) or ducts of the kidney, which, having reached the pelvis, proceed below the broad ligaments (Fig. 138)) to run forward and enter the base of the bladder, there discharging the urine.
The opening for the escape of the urine is called the internal
Bladder Uterus
Urethra
Vaginal orifice
Anus (rectum distended)
FIG. 165. — PELVIC ORGANS, FEMALE PELVIS. — (Holden.) Dotted lines indicate peritoneum.
orifice. It leads into a canal called the urethra which ends at the external orifice (or meatus), and through it the urine is expelled from the body. The internal orifice is guarded by circular muscle fibers forming a sphincter — the sphincter vesica (sphincter of the bladder). The part where the internal orifice is located is often called the neck of the bladder.
The openings of the ureters are about one inch from the internal orifice, and the same distance apart, thus these three openings mark the corners of a triangle at the base of the bladder, called the trigone.
The urethra is a fibro-muscular canal lined with mucous mem- brane. It begins at the internal orifice of the bladder, ends at the external orifice or meatus urinarius, and conducts the urine from the body.
248 ANATOMY AND PHYSIOLOGY
The length of the male urethra is from seven to eight inches.
The female urethra is about one and one-half inches long and 1/4 in wide, but is very distensible. It curves slightly downward toward the external meatus.
Clinical note. — The catheter should pass a little upward after entering the urethra (Fig. 165).
A urethral caruncle is an exceedingly painful little tumor projecting from the urethral mucous membrane. It is a collection of sensitive blood-vessels and nerves.
When empty the bladder lies entirely in the pelvis, but if it contains more than eight ounces it begins to rise into the abdo- men. It has been known to extend as high as the umbilicus.
Surgical notes. — Since the peritoneum covers the vertex and a portion of the posterior surface only, the bladder may be entered in front through an incision just above the symphysis pubis without wounding the peritoneum.
Cystitis is inflammation of the bladder.
PHYSIOLOGY OF THE KIDNEYS AND ACCESSORY
ORGANS
This consists in the removal of waste substances from the blood in the form of urine and expelling it from the body.
The process of excretion in the kidney is one of filtration and secretion. The kidney has a large blood supply through the renal artery, which enters at the hilum and divides at once into several branches. The capillaries from these arteries are very numerous. They enter first the capsule of the Mal- pighian body as afferent vessels and form a cluster or tuft there (the glomerulus) from which the water and salts are filtered out and pass into the tubule. They then leave the capsule as efferent vessels and twist themselves about the convoluted tubules, whose epithelial cells select (secrete} the organic substances — urea, uric acid and others. These are washed down, by the watery solution coming from the capsule, to the collecting tubes of the pyramids and there discharged into the pelvis of the kidney, as urine; the amount of urine excreted varies greatly, but in the adult, in health, averages 48 ounces or 3 pints daily; it is directly affected by the quantity of fluid which the person drinks, the amount of perspiration formed and in other ways.
Children excrete more than adults in proportion to the body size, averaging nearly one-half of the adult quantity at the age of five years. This is probably due to the fact that their dietary contains more fluid, also their metabolism or tissue change is more rapidly carried on, creating more waste material proportion- ately, to be eliminated.
URINE 249
Clinical note. — Renal colic is caused by the attempt to pass a stone or calculus through the ureter.
Urine is excreted more rapidly in the middle of the day, from one to two o'clock, and after waking from sleep; less rapidly between two and four in the afternoon.
Micturition is the act of expelling the urine from the bladder (clinically, it is often called urination). The contraction of certain muscles of the bladder wall opens the sphincter vesicce and the urine escapes through the urethra.1
Although under the control of the will after a preliminary period of education, micturition is sometimes involuntary, con- stituting enuresis or urinary incontinence. This may be due to the presence of irritating substances in the urine which affect the mus- cles of the bladder, or to too great concentration, or simply to an excessive quantity of fluid, or to lack of control by the nervous system — or various causes of a reflex character.
Retention of urine means accumulation in the bladder owing to inability to expel it. This may be due to one or more of several causes: lack of muscle tone and feeble contracting power; nervous contraction (closure) of the sphincter; impaired sensibility of vesical nerves; loss of spinal nerve control; obstruction at the neck of the bladder, etc. This inability may be so complete that the bladder becomes entirely filled and the sphincter can no longer act; the urine dribbles away and the condition is one of ll retention with overflow" from inability of the bladder to contract.
Suppression of urine means inability of the kidney to act; no urine is excreted.
Urine is a watery fluid of amber color, somewhat heavier than water (the normal specific gravity is 1010-1020), with a charac- teristic odor, and having the temperature of the body at the time of voiding. Its reaction is normally acid. This is due to the character of the diet of man, which in most cases contains more or less of animal food. Certain salts (acid phosphates) derived from this mixed diet cause the acidity of the urine. It is more marked in the morning before food is taken. With a diet of vegetables and cereals the reaction is neutral or, perhaps, alkaline.
The coloring matter is derived from bile pigments; it is deep or
1 All sphincters are opened in this manner — by action of the walls of the cavity which they guard.
250 ANATOMY AND PHYSIOLOGY
pale, as the urine contains less or more water. The weight is due to the salts contained, both organic and inorganic (or mineral) and this also is modified by the amount of water. Both water and salts vary markedly with the dietary of the individual.
Clinical notes. — The color and odor may both be modified by drugs or by articles of food. (For example, turpentine causes the odor of violets, while that imparted by asparagus is well known.) Urine containing blood cells is smoky in appearance; and every nurse knows what methylene blue will do.
The most important substance to be excreted in the urine is urea. This represents the absolutely useless material remaining from protein foods. It is prepared for excretion in the liver. It is a substance which if allowed to accumulate in the system becomes a deadly poison, causing death by uremia.
Uric acid is protein waste in another form and smaller quantity. Phosphates of sodium, potassium and calcium are present normally, also other mineral salts, sodium chloride (common salt) being the most abundant.
Water is necessary for the solution of all these solids. This varies in quantity in many systemic conditions. Increased activity of the lungs and skin, for example, removes water from the blood and thus makes the urine scanty but more dense and very acid.
Two sets of causes affect the quantity of urine: i. those which increase or diminish blood pressure in the kidney; 2. those which influence the secretory activity of the cells which line the tubules. Increased blood pressure increases the flow of water and salts (in the glomeruli) ; toxic substances (organic waste) stimulate the excretory function of the cells in the tubules.
The importance of the kidneys is shown by the fact that the daily quantity of urine normally produced, equals the excretion of the lungs, skin and intestinal tract together.
The average amount of solids in the body (to be excreted) does not vary greatly, but the quantity of water ingested varies constantly and the specific gravity changes with the water supply.
The quantity and the specific gravity bear a pretty constant ratio to each other. As a rule, the abundant urine is light in weight (low specific gravity}. Conversely, the scanty urine is dense and heavy (high specific gravity}. A notable exception is the urine of diabetes mellitus, which is very abundant and at the same time has high specific gravity, owing it to the sugar content.
NEPHRITIS, RENAL CASTS 251
Whatever increases blood pressure increases the amount of urine; many diuretic medicines act in this manner. Muscle exercise not only increases blood pressure, but stimulates the secreting cells by the toxic substances which arise normally from rapid metabolism and are carried to the kidney by the quickened circulation.
Nervous excitement and hysteria cause an abundant pale urine. Cold weather and moist air both discourage the activity of the skin —therefore, they increase the action of the kidneys.
On the other hand, if the system rids itself of water in other ways, as by excessive perspiration, diaphoretic medicines, hot packs, etc., the urine will be diminished, but it will have a high specific gravity.
Clinical notes. — i. The toxic substances which are present in the blood in fevers are abnormal to the kidney and modify its action so that the urine is scanty and dense.
2. Nephritis is inflammation of the kidney. In one form (acute Bright' s disease) it causes a scanty and dense urine; in another and chronic form an abundant dilute urine. (When waste ceases to appear we know that the cells are not secreting.)
3. Certain poisons which are swallowed (bichloride of mercury for example) cause such intense irritation of the cells in the tubules that they are seriously injured and may be destroyed.
4. Renal casts. (Tube Casts.} — Irritation of the kidney struc- ture so changes its tissue that plastic material from the blood exudes into the tubules and is there moulded into their shape, forming casts. Hyaline casts are transparent (being the simplest form). Granular casts show a more advanced stage of trouble. Epithelial casts have epithelial cells added; urate casts are common in rheumatism and tonsillitis, etc., etc.
5. Casts signify renal congestion, always; if persistent they indicate inflammation.
6. Albuminuria, or the presence of albumin in the urine, is also an evidence of congestion or of disease. It is often temporary, disappearing with the disappearance of the cause, which may be fever, the inhalation of ether, the use of alcohol, etc.
7. Albumin is often due to conditions outside of the kidney
252 ANATOMY AND PHYSIOLOGY
tissue. It is seen in anemia (chronic) ; with the presence of pus, or accompanying the admixture of vaginal discharge.
Important notes. — Specimens for complete urine analysis should represent the activity of the kidneys during twenty-four hours, as the composition of the urine varies during exercise and rest, in fasting or when food is taken, and so forth.
It will often be the duty of the nurse to test the chemical re- action by the use of litmus paper. Acidity is due to kidney con- ditions; alkalinity to bladder conditions (usually). (The reaction is influenced by drugs.)
Polyuria is excessive secretion of urine.
Oliguria is diminished secretion — scanty urine.
Hematuria is the secretion of bloody urine.
Hemoglobinuria is the secretion of urine which contains the colored portion (hemoglobin) of disintegrated red blood cells.
Glycosuria is the secretion of urine containing grape sugar or glucose.
ABNORMAL POSITIONS OF THE KIDNEY
A kidney may develop in some unusual location ; if it is fixed in that position it is called a misplaced kidney.
A floating kidney is one which develops in an unusual location but is not fixed in that position. It then has a covering of peri- toneum (meso-nephron) like that of other abdominal organs and moves freely.
A movable kidney is one developed in the proper place, but either through loss of the fatty capsule, or relaxation of tissues generally, it moves in its capsule of fascia. It makes excursions upward and downward following the movements of the diaphragm and may be palpated. It may become quite displaced and even fixed in the abnormal position constituting a dislocated kidney.
During development the kidney consists of lobules which later become fused into a uniform structure; persistence of this lobu- lated arrangement (infantile kidney) may be observed at autopsy. This is not important.
Occasionally one kidney may be absent. Sometimes two kid- neys are fused into one, making an arched or horse-shoe kidney.
CHAPTER XVI ELIMINATION
THE SKIN
The skin, or integument, is the elastic and protective covering of the body. It covers the entire exterior surface and is continuous at the orifices of the body with the mucous membranes of the interior surfaces. It consists of two layers, a deep one called the
FIG. 166.
Showing the layers of the skin (greatly magnified), with the sweat glands and oil glands, and a hair in its follicle. (Brubaker.)
corium, also the cutis vera or true skin, or derma, and a superficial one called the epidermis or cuticle.
The corium or "true skin" (cutis vera) is a vascular, elastic and sensitive layer, red and soft; resting upon a loose subcutaneous tissue. Its deep^portion is well supplied with vessels and nerves
253
254
ANATOMY AND PHYSIOLOGY
(tactile cells) supported by a fibrous and elastic network (reticular layer) which contains non-striated muscle fibers and fat. In this layer are the blood-vessels, nerves and lymphatics which are exceedingly numerous.
Tiny projections called papilla rise from this network portion, many papilla containing special nerve-endings called touch cor- puscles. They all contain at least a single loop of blood-vessels. Some contain several loops — these are vascular papilla. They
are arranged in rows form- ing ridges which are circular on the front of the finger tips. It is a remarkable fact that no two fingers or toes are alike in this respect, hence the thumb- or finger-mark is a means of identification. Its value is never lost, even in old age, as these ridges are permanent.
The papillae constitute a "papil- lary layer." There are still other nerve endings in the corium for different sensations. These are nerve papillae.
The epidermis (or cuticle) completely covers the corium. It consists of layers of cells of varying character and thickness. The deeper cells are soft and nucleated, but near the surface they become flat and dry, until finally they are mere tiny scales. It has no vessels and scarcely any nerves, consequently it is not sensitive and does not bleed. It is this which comes away after the action of a blister.
The color of the skin depends partly upon the blood supply and more upon pigment or coloring matter, which is deposited in the deep layers of the epidermis (and the superficial layers of the derma). The pigment varies in different people and races.
In all races, the color is deeper in exposed portions of the skin (face and hands), about the arms, axillae, and the areolae of the mammary glands. It is lighter than elsewhere on the palms and soles of the colored races. Exposure to heat as well as light deepens it.
FIG. 167. — TACTILE CELLS FROM SNOUT OF PIG. a. Tactile cell. m. Tactile disc. n. Nerve-fiber. — (Stirling.')
CHARACTERISTICS OF SKIN 255
Clinical notes. — The insensitive and bloodless character of the epidermis or cuticle is plainly demonstrated in the dressing of a blister, when it is incised to allow the escape of serum which has accumulated between it and the corium or true skin. Again, the fact of the pigment deposit in the deep layers of the epidermis is shown when the blister is on the skin of a colored person; the pigment comes away with the elevated epidermis.
The surface of the epidermis is continually wearing away and new layers of epithelial cells are exposed, to become dry and scaly, and to be shed in their turn. It varies in thickness according to the degree of friction, or pres- sure, or exposure which it encounters. Witness the palms of the hands and the soles of the feet, the back of the neck and shoulders, the scalp, and — in contrast — the thin skin of the flexor surfaces of joints, the groins, medial surfaces of limbs, etc. (It is in these latter locations that inunctions are given.)
The vascularity of the skin is evident from the free flow of blood after the slightest cut. There are two special networks (rete) of capillaries, one just beneath the true skin, and one at the bases of the papillae.
The elasticity of the skin is demonstrated when a cut is made through the corium. The edges retract and some effort is required to bring them together again. The elasticity is due not only to the elastic fibers in the deep layer of the corium, but to muscle fibers, small though they be.
The sensibility of the skin is very marked. Nerve-ends exist in the corium for various sensations, a few fibrils being connected with the deep layer of the epidermis. (See The Skin as the Organ of Touch, p. 327.)
The greater portion of the skin is loosely connected to the parts beneath it by subcutaneous areolar tissue (see p. 5), so that it is movable. When this contains fat it is called the panniculus adiposus. There is no fat under the skin of the scrotum, eyelids or posterior surface of the external ear.
(The skin of the scalp is not very movable, except as the entire structure is moved by the epicranial muscle.)
The glands of the skin are in the corium; their ducts pass through the epidermis to open upon the surface. They are of two kinds — the sebaceous glands and the sweat glands (sudoriferous glands) .
The sebaceous glands are found in the skin of all parts of the body except the palms and soles. They are most numerous upon the face. They produce an oily substance called sebum which
256 ANATOMY AND PHYSIOLOGY
renders the skin soft and pliable. Their ducts open into the de- pressions (follicles) for the roots of hairs, consequently they pre- serve the softness and glossiness of the hair.
Ear wax, or cerumen, is secreted by specialized glands in the auditory canal (ceruminous glands) .
Note. — The vernix caseosa which is found upon the skin of the new-born child is an accumulation of sebaceous matter which has served to protect the skin from the effect of long submersion in the amniotic fluid. .
The sweat glands (sudoriferous glands) are found in the skin of the entire body. Each gland consists of a coiled tube embedded in the corium, with a duct opening upon the surface; these ducts open upon the ridges made by the rows of papillae. With an ordinary magnifying glass the droplets of sweat may be seen.
The sweat or perspiration is a thin watery fluid (highly acid, but saline to the taste), containing a number of substances in solu- tion, derived from the vessels in the network of the corium. The most important are salt, phosphates, urea and carbon dioxide.
It is estimated that the 2,000,000 or more glands secrete nearly a liter of perspiration daily, in health. The process goes on con- tinually; when the rate of excretion is moderate and uniform we are not aware of it, because the moisture is removed in various ways as soon as formed — this is insensible perspiration. When the removal does not keep pace with the production, the accumu- lation on the skin becomes sensible perspiration.
APPENDAGES OF THE SKIN
The appendages of the skin are the glands already described, the nails and the hairs.
The nails are hard but elastic structures belonging to the cuti- cle (being modifications of its epithelium). They give protection to, and add power and ease in using the digits. The body of the nail lies upon a bed of corium called the matrix, from which it grows; if the matrix be destroyed the nail is lost and no new one will grow in its place. The root of the nail is embedded in a fold of skin; the white semicircle at the root is called the lunula (little moon).
Clinical note. — The body of the nail adheres firmly to the true skin. Much force is required for its removal.
THE HAIRS 257
The hairs also belong to the cuticle. They are distributed over the greater part of the surface of the body, being conspicuous on the scalp by their size and length.
A hair consists of a root and a shaft. The bulb or (enlargement of the) root rests upon a minute hair papilla in the bottom of a depression called a hair follicle.1 The nerves and blood-vessels do not run beyond the papilla.
The shaft extends outward from the root, and contains the pigment which decides the color of the hair.
The main body of the shaft consists of fibrous or cortical sub- stance. In this is the pigment of dark hairs, but only minute air spaces in white hairs. In all coarse hairs except those of the scalp, and in the roots of most hairs, a central pith or medulla exists within the fibrous substance. The shaft is covered with a cuticle of flat scales which overlap each other.
The hairs lie obliquely on the skin but may be made to stand erect by the contraction of a tiny muscle bundle placed at the root of each one. These are the erectors of the hairs. It is their action which gives the appearance called "goose-flesh." The softness and the gloss of hair are due to the oil which is poured into the follicles by the oil glands.
Note. — The fine hair on the skin of the new-born child is called lanugo. It begins to grow at about the fifth month of intra-uterine life, and wears away soon after birth, although some remains permanently.
The hairs which border the eyelids are called cilia. The hairs of the eyebrows are super cilia. Those of the nostrils are vibrissa; of the head, capili; of the beard, barba.
PHYSIOLOGY OF THE SKIN
The skin has a triple function. It is the protective covering of the body; an organ of excretion and an organ of the special sense of touch. Also, it aids in regulating body temperature.
As a protective it is mechanical only; the insensitive layers receiving first the impressions of external forces — heat, cold, blows, etc., diminish their effects on deeper and sensitive ones.
As an organ of touch it is referred to on page 327.
1 In the case of curly hair the opening of the follicle leads inward in a curved or spiral direction.
17
258 ANATOMY AND PHYSIOLOGY
Its most important function is to secrete perspiration. Per- spiration is a clear watery fluid consisting of a solution of certain waste products of metabolism (tissue waste), in other words, water and solids. It is acid in reaction; saline to taste. The quantity excreted by a healthy active person in twenty-four hours has been estimated as one quart.
Although the amount of solids in the perspiration is small, it is enough to relieve the system if the kidneys are disabled, or to embarrass it if retained. Urea is one of the substances contained in perspiration, and in diseased conditions of the kidneys the skin is able to excrete an increased quantity of urea.
The removal of tissue waste is, however, not the only important use of perspiration. By bringing water to the surface of the skin, it is a most efficient agent for regulating the temperature of the body. Muscle exercise, for example, which increases heat production, is accompanied by increased activity of the sweat glands, and the consequent evaporation of water carries off the excess of heat generated in the muscles. Again, high temperature of the sur- rounding atmosphere causes dilatation of the cutaneous vessels, and more perspiration and consequent evaporation. Conversely, a cold atmosphere stimulates the cutaneous vessels to contract, and stops the production of sensible perspiration. All of this activity is, of course, a response to the controlling force of nerve centers which regulate blood supply, and stimulate secretory action.
Clinical note. — From these facts one may understand why it is so impor- tant to conserve the surface temperature of a patient with nephritis, or with diminution of urine from any cause, by the use of blankets and warm clothing; and to increase it oftentimes by the use of hot baths, packs, etc.
In health the quantity of perspiration is modified by the die- tary, particularly by the amount of liquid taken, and the kind of liquid; also by the character of clothing, the season of the year, temperature of the atmosphere, etc.
It may be noted that the activities of the skin and kidneys alternate with change of season; in summer when the skin is active the urine is scanty. In winter, when the skin is inactive the urine is free.
Drugs which increase the production of perspiration are called diaphoretics. Aconite and sweet spirits of nitre are familiar exam-
ACTIVITIES OF THE SKIN 259
pies. Hot drinks and muscular effort assist diaphoresis. Nervous excitement, as fear, pain, nausea, produces the same effect. The toxins of certain diseases also cause excessive perspiration, as in the nocturnal sweating of tuberculosis, the crisis of pneumonia, and other instances.
In fevers, cutaneous vessels are dilated, but the nerve stimulus to cell action is dulled and the skin remains dry.
Some other diseases have a similar effect; loss of water by colliquative diarrhea (characterized by profuse liquid stools) leaves the skin dry. In diabetes mellitus a very troublesome symptom is dryness of the skin with pruritus or itching (and a tendency of the connective tissue to break down in boils).
The effect of baths upon the skin is to abstract heat, improve the tone of cutaneous structures, and favor the action of the glands.
In renal diseases, activity of the skin is to be promoted; in fevers, activity of the kidneys, as well as of the skin.
The skin has a slight degree of absorbent action in the areas where it is thinnest; this power is utilized for inunctions.
Clinical note. — The skin should be well rubbed until it is warm and quite dry of perspiration or oil before applying a medicine by inunction, in order that the circulation of cutaneous vessels may favor absorption. Animal oils are more easily absorbed by the skin than vegetable oils.
SUMMARY
The skin is protective, excretory, an organ of special sense, of heat regulation and — to a moderate extent— of absorption.
CHAPTER XVII MAMMARY GLANDS. DUCTLESS GLANDS
THE MAMMARY GLANDS
The mammary glands are placed between two layers of super- ficial fascia in front of the thorax, occupying a space between the third and sixth ribs, inclusive. They are covered by a layer of adi- pose tissue and lie between two layers of superficial fascia. They
Aerol a — A^fe
FIG. 168. Showing enlarged milk ducts during lactation. — (Morris.}
consist of little tubes, lined with milk-secreting cells and grouped in small lobules, held together by connective tissue imbedded in adipose. The lobules unite to form lobes, 18 or 20, each with its own duct, thereby constituting a complete gland in itself; these 1 8 or 20 milk ducts (lactiferous ducts) approach the nipple and open at its summit. The nipple is surrounded by a ring of darker modified skin called the areola. A few small elevations are seen on the areola; they are called the glands of Montgomery.
260
COMPOSITION OF MILK 261
Frequently, prolongations of mammary tissue extend laterally from the gland toward the border of the axilla, sometimes they are found near the sternum.
The function of the mammary gland is the secretion of milk. This is a true secretion; the cells of the tubules forming a new sub- stance from materials brought by the blood, which, although not utilized in the body where it is formed, is not only useful but capable of sustaining life.
Note. — The presence and activity of the ovaries seem to be essential to the proper development of the mammary gland.
Milk is a bluish-white fluid consisting of clear plasma (milk plasma) holding nutritive substances in solution and floating myriads of oil globules, to which it owes its white color. It is a natural emulsion. The variety of nutritive substances contained in it is sufficient for the development of the body of the infant.
Human milk is amphoteric.1
The contained proteins are peculiar to milk and form a soft flaky curd in the process of digestion. They are several in number, the most important being caseinogen, from which casein is derived in the process of digestion. (Cow's milk forms a tough curd in digesting. It contains more casein but less sugar and less fat. It is nearer acid than human milk.)
The sugar of milk is lactose (probably absorbed as such — does not require digesting). The salts are the various salts found in foods and the body tissues, the most abundant being compounds of calcium, potassium and sodium.
The water and salts are derived directly from the blood by filtration; the special proteins and lactose are secreted by the cells of the tubules. (Lactose is found nowhere but in milk, the same is true of lact-albumin — they are special secretions of the mammary glands.)
Average percentage of fat, sugar and proteins in milk as given by Holt:
Colostrum Human milk Cow's milk
Fats 2.04 3-5 3.5
Sugar 3.74 6-7 4.3
Proteids.. 5.71 1-2.25 4
1 Amphoteric. Neither acid nor alkaline, acting on both red and blue litmus paper.
262 ANATOMY AND PHYSIOLOGY
During pregnancy the areola acquires a deeper color (which is permanent) and the glands of Montgomery are enlarged.
At this time the blood supply of the gland increases, the glands become large, and changes occur in the lining of the tubules, which result in the secretion of milk. This is perfected soon after the end of pregnancy.
The first fluid which is drawn from the breast is called colos- trum; it is yellow (from the presence of colostrum corpuscles), alkaline, rich in proteins and salts but not in sugar nor in fat. ' It contains a substance which acts as a laxative for the infant.
The secretion of milk is influenced by the diet of the mother and may be modified in both quantity and quality by food selection. A still greater effect is produced by the condition of her nervous systems; it is well known that fright or anger, or intense emotion, may so affect the milk as to make it injurious to the infant. Fatigue, worry, loss of sleep, etc., are all to be avoided by the nursing mother.
Human milk contains a small quantity of starch splitting (amylolytic) enzyme; it is possible, therefore, to exert some effect upon the starch content of barley water in the food of the young infant so that some nourishment may be gained from it.
The milk may differ in the two breasts of the same person.
Menstruation is accompanied by a diminution of lactose and an increase of fat and casein.
The milk of the pregnant woman is poor in quality, especially in fat.
Clinical note. — Certain drugs taken by the mother will be eliminated through the milk in sufficient degree to affect the child; as beer, or bromides, salines and other cathartics; strychnia, arsenic, etc.
Surgical note. — Mammary abscess is caused by infection through a break or fissure in the skin of the nipple, the pus form- ing between the lobes of the gland. Post-mammary abscess is in the fascia behind the gland.
THE DUCTLESS GLANDS OR THE ENDOCRIN SYSTEM
This system includes the ductless glands and the chromaffin tissues.
THE ^PANCREAS 263
These are the organs which resemble glands but have no ducts. They are supplied with sympathetic nerves, and possess many lymphatics and blood-vessels; the secretions which they produce are internal secretions and are carried in these vessels. The most important ductless glands are the spleen, adrenal bodies and certain portions of the pancreas, in the abdomen; thyroid, para- thyroid, and ^thymus bodies in the neck; pituitary body (or hypophysis) in the cranial cavity. To these may be added the ovaries (also the carotid, parasympathetic and coccygeal bodies).
The cells of the chromaffin tissues are found in the interior of the adrenal bodies and in certain small groups which are ranged along the abdoninal aorta.
Each of the structures of the endocrin system bears a relation to one or more of the others which is not yet perfectly understood.
Their secretions have never been obtained for examination but there is abundant evidence that they exist.
The name autocoid substances has been proposed for the active agents in these secretions. It is believed that there are two kinds of autocoid substances: the hormones, which stimulate activity in tissues to which the blood carries them, and the chalones, which inhibit or prevent activity where they are carried. Each member of the endocrin system has its own special autocoid substance.
So little is understood of the action of these various organs that descriptions are necessarily brief.
THE PANCREAS
In addition to the digestive ferments of the pancreas it produces another and highly important substance, which either disposes of sugar in the blood, or is associated with the glycogenic function of the liver, or both. This is supposed to be the special function of groups of cells called "islands of Langerhans" which are embedded in the substance of the pancreas. They resemble glands but have no ducts; they are surrounded by a network of capillaries and their internal secretion is transmitted by these vessels.
The blood supply to the pancreas is very free, being derived from the hepatic, splenic and superior mesenteric arteries. This indicates the importance of the gland.
264 ANATOMY AND PHYSIOLOGY
Clinical notes. — Disease of the pancreas is accompanied by the appearance of an excessive amount of sugar in the urine, or diabetes mellitus of a severe character.
Removal of pancreas, if complete, causes the same result which, however, may be prevented by transplantation of a piece of pancreas tissue under the skin.
THE SPLEEN
It is believed (but not proven) that the cells of the splenic pulp contain an enzyme which aids in the digestion of protein foods, through its action upon the pancreas, by furnishing hormones to stimulate the production of protein-digesting enzymes in the pan- creatic juice.
THE ADRENAL BODIES
The adrenals (suprarenal capsules), are two small gland-like bodies resting on the upper extremities of the kidneys, hence their name. They are triangular in shape, yellowish in color, and have many blood-vessels and nerves. The superficial portion of the adrenal body is the cortex or cortical portion. It is this part which is in some way, neces- sary to life.
The interior portion, enclosed by the cortex, is the medulla, or medullary por- tion; this is one of the chromaffin tissues, and it is thought that the internal secretion is here formed. The adrenal bodies are important organs, as it is found that when they are removed death follows soon, but their use is not yet fully understood. It has, however, been determined that the internal secretion, epinephrin, acts through RESTING UPON THE KID- sympathetic nerves on plain muscle fibers and the heart; its effect is to cause contrac- tion of small arteries, thus increasing blood pressure, at the same time slowing the rate of the heart beat. Because of this, epinephrin or adrenalin is an important agent in checking hemorrhage by local application, as in operations upon the throat or nose.
A solution of epinephrin or adrenalin given by hypodermic in- jection is used to relax the spasm of bronchiole muscle fiber in
THYROID BODY
asthma. It will also shorten the coagulation time of blood (tem- porarily). It inhibits contraction of the stomach and intestine, also of bladder and uterus.
In the disease called " bronzing of the skin," or Addison's disease, these bodies are found to be changed.
THE THYROID BODY
The thyroid body is situated in the anterior part of the neck (Fig. 170).
It has two lateral lobes lying close to the upper portion of the trachea and connected by a middle portion called the isthmus.
Median portion of crico- thyroid membrane
Crico-thyroid muscle
Thyroid isthmus
Lateral lobe of thyroid body
FIG. 170. — THYROID BODY. — (Morris.}
These lobes are about one and one-fourth inches wide, and extend about two inches upward along the sides of the larynx. A middle lobe may exist, extending upward from the isthmus in front of the larynx.
The substance of the thyroid body is made up of closed sacs containing a thick semifluid substance (colloid substance). They are surrounded by many capillaries; the thyroid arteries being four in number, the blood supply is very free. It is supported in its position by fibrous attachments to the sides of the larynx and also to the fascia behind the trachea.
Clinical note. — If the thyroid body becomes very much enlarged it does not freely glide upward and downward with the larynx in the act of swallow-
266 ANATOMY AND PHYSIOLOGY
ing as, normally, it should do; if it is fixed by adhesions or by excessive growth it exerts traction upon the larynx and trachea which is visible during the movements of swallowing.
The function of the thyroid body is important but not well explained. It is observed that the development of both mind and body is arrested if the thyroid be absent, or if it does not itself develop in childhood; this condition is known as cretinism.
Degeneration or complete removal, in adult life, is followed by excessive growth (but imperfect development) of connective tissue and skin elements, or myxedema, and a gradual deterioration of mental power. These effects may be prevented by leaving a small portion of the gland in place or by transplanting it. . From these and other clinical observations it is evident that the internal secretion of this body exercises an important influence upon nutrition. It stimulates cardiac action, increases blood pressure, and restrains a tendency to obesity.
Clinical notes. — Simple enlargement of the thyroid body constitutes goiter, which is said to be frequent in certain countries where the drinking water contains much lime.
Exophthalmic goiter is a diseased condition of the thyroid body with the following symptoms: Enlargement and pulsation of the thyroid, rapid heart action, tremor, and protrusion of the eyeballs.
THE PARATHYROID BODIES
The parathyroid bodies are small bodies situated above and laterally to the thyroid, two on each side. They have an abundant blood supply. Their function is not explained but it is now known that their removal is soon followed by convulsive affections, tremor, etc., suggesting the presence of an irritant in the blood which did not exist before. Consequently it may be that their internal secretion is able to neutralize certain toxic substances formed elsewhere, and capable of causing death.
Both parathyroid and thyroid bodies contain iodin in combina- tion with some other substance.
THE THYMUS BODY
The thymus body (Fig. 171) is an organ of fetal and infantile life, situated below the thyroid, being mostly in the thorax and ex-
PITUITARY BODY
267
tending downward to the pericardium. It is two and one-half inches Jong at the age of two- years, but dwindles slowly from that time on, leaving very perceptible remnants only, during adult life. A persistent thymus is one of the features of the condition known as infantilism. It has been thought that its secretion lowers blood pressure.
Thyroid
Small intestine
Bladder
Trachea
- Thymus
Lung
Right auricle
Right ventricle
Stomach
Part of transverse colon
Hypogastric artery
FIG. 171. — VISCERA AT BIRTH. NOTE THE THYMUS BODY, THE SIZE OF THE LIVER AND THE LOCATION or THE BLADDER AND THE HYPOGASTRIC ARTERIES. — (Morris after Rudinger.)
THE PITUITARY BODY
The pituitary body (Fig. 193) (hypophysis cerebri) is included among ductless glands. It rests in the sella turcica of the sphenoid bone. By investigation it has been learned that degeneration of this body in the adult is the probable cause of the disease called acro- megaly, which is characterized by an overgrowth or hypertrophy of the bones of the face and extremities. Should this occur in young children or while the bones are still developing, over-growth of the skeleton or gigantism will result. Certain conclusions have
268 ANATOMY AND PHYSIOLOGY
been founded upon this association, presupposing that it produces an internal secretion which regulates the growth of bones. It also increases the force of cardiac action and general blood pressure. It is found to stimulate the contraction of unstriped muscle fiber, as in the uterus, and has been used for that purpose. Its influence upon metabolism is still under investigation. Its removal is fol- lowed by atrophy of the generative organs.
Clinical note. — Hypertrophy or tumor of the pituitary body or hypophysis causes blindness by pressure upon optic nerve fibers.
The carotid bodies are placed behind the common carotid artery just at the point where it bifurcates. Use unknown. The para-sympathetic bodies one to four in number, lie in front of the third and fourth lumbar vertebrae. Use unknown. The coccygeal body lies in front of the lowest part of the coccyx. Use unknown.
CHAPTER XVIII METABOLISM
We have now studied the various organs which form secretions, or substances which may be either devoted to a special use in the body, or expelled as of no further use. These latter are known as excretions.
SECRETION
Following, is an enumeration by way of review, of the principal organs whose secretions are used in the body, with a partial list of their functions:
First. — The epithelial cells of all surface membranes and cavities should be included:
Those of mucous membranes, secreting mucus.
Those of serous membranes, secreting serum (as in the pleural, pericardial and peritoneal cavities, and the subdural and sub- arachnoid spaces of brain and spinal cord).
Those of synovial membranes, secreting synovia. The secreting cells of glands come next.
The salivary, gastric and intestinal glands and pancreas secrete saliva, gastric, intestinal and pancreatic juices.
The liver secretes bile (and forms glycogen).
The mammary glands secrete milk.
The lacrimal glands secrete tears.
The sebaceous glands secrete sebum. Of the secretions of so-called ductless glands, or endocrin system.
That of the pancreas influences glycogen-processes in the liver.
That of the adrenal bodies increases blood pressure (contracting arterioles) and retards the rate of cardiac action, also favors the formation of sugar in the body.
That of the thyroid body influences tissue metabolism, increases cardiac action, and diminishes obesity.
That of the parathyroids destroys toxins in the blood (or inhibits their formation?).
269
270 ANATOMY AND PHYSIOLOGY
That of the pituitary body (or hypophysis) restrains growth of osseous tissue and influences metabolism, establishing a tolerance for sugars.
That of the ovary is associated with the function of the mam- mary gland and the uterus, and influences the action of vaso- motor nerves of the systemic circulation. This internal secretion is furnished by the corpus luteum (p. 349).
In addition to the above may be mentioned:
The spleen and lymph glands which supply white cells to blood
The marrow of bones which supply red cells to blood.
The testes which produce spermatozoa.
The secretions of the organs named, serve various purposes, aiding or influencing nutrition, or assisting in the formation of other substances.
EXCRETION
Excretions. — These are the substances which must be elimi- nated from the body.
All tissue action uses up some material, leaving a varying rem- nant of waste matter which cannot be utilized — like the ashes from a fire. These wastes appear either dissolved in water as urine and perspiration, or in the form of gas or vapor.
Tissue waste may be reduced ultimately to comparatively few substances, the most important being urea, carbon dioxide, various salts and water. Urea is most abundant in urine, C02 in exhaled air, and all of these in small quantity in perspiration.
Therefore, the organs of elimination are:
The kidneys, which excrete urine.
The skin, which excretes perspiration.
The lungs, which exhale carbon dioxide, organic matters, am- monia and water.
To these may be added the liver and the intestinal canal.
The liver excretes waste matters with the bile and forms urea.
The intestinal canal .excretes small quantities of tissue waste (gases, water, mucus, etc.).
GENERAL METABOLISM
We have studied the framework of the body with its various connections and adaptations, its coverings and its cavities, the
METABOLIC PROCESSES 271
organs by which it is fed and the wear and tear of its machinery continually made good, as it is nourished and sustained — a living organism.
The combined processes of up-building and breaking down — in the living body — constitute metabolism. A well-equipped labora- tory presents facilities for illustrating the actual chemical changes which take place, but only in the living cell are they metabolic.
Attention has been directed to the four classes of substances composing the body tissues, and the corresponding food-substances supplied to them in the dietary. We have seen that these foods are presented to the body in compounds more or less complex (most of them insoluble) and we have traced (briefly) their changes in the system from the time of ingestion to their disposition in the tissues or their expulsion as excreta. It remains to review them from the standpoint of their value in metabolism.
All foods must subserve one or more of three purposes, namely: —to evolve heat; to release energy ; to repair waste.
Proteins, being reduced by digestion to simpler forms (peptones and amino-acids) are absorbed and appear reconstructed in muscles, blood, lymph and milk, mainly (in all tissues actually), where by their nitrogenous portion they contribute to the " betterment of cell conditions'' and compensate for wear and tear everywhere in the body; by their non-nitrogenous elements they evolve heat and create energy.
Protein wastes (or excreta) take the form of urea — uric acid and compounds — ammonia — excreted through the kidneys.
Carbohydrates, taken as sugar or converted into that form, are absorbed and circulated, stored in liver and muscle as glycogen to appear when needed as sugar again — to be oxidized for the pro- duction of heat and energy or stored as fat. Their excreta are CO2 and water.
Fats, after digestion, are distributed for use in many parts, their oxidations evolving heat and motion, or are stored in sub- cutaneous fascia, marrow, between viscera, etc. Their excreta are CO2 and water.
Mineral Salts and water are absorbed together in solution and distributed to aid in the formation of various tissues throughout the body.
It thus appears that all foods contribute to body heat and
272 ANATOMY AND PHYSIOLOGY
energy, by entering into the up-building of the tissues which are quickly used up for those purposes ; while the proteins have in addi- tion as their principal function, the construction of body tissues of a more permanent character.
These changes are largely dependent upon the combination of oxygen with food or tissue compounds. "The essential source of heat and mechanical work developed in the animal organism is to be found in the oxidations" (Hammarsten). But behind these are the enzymes; in nearly all active tissue cells the changes begin with their action. Certain oxidizing ferments make the first splitting of complex substances, afterward the union with oxygen follows.
In digestion processes we have seen that the first change is associated with a splitting of and union with the elements of water (H20). The enzymes which set this change in motion are hydro- lytic enzymes.
FOOD VALUES
By study and experiment it is found that the proper propor- tions of proteins, carbohydrates and fats in the human dietary are as follows: — proteins one-fifth, fats one-fifth, carbohydrates three-fifths. Since in the body, heat and mechanical work are produced in company, the degree of heat evolved by work is taken as the measure of force to be supplied by food, or the measures of food value.
The heat unit of measurement is called the calorie (large calorie), which signifies the amount of heat required to raise one kilo of water to i°C.
A food which when burned will do this has a calorific value of one degree, that is, it is graded at one calorie in value.
The following are estimated averages of calorific values.
Proteins one gram yields 4 . to 4. i calories.
Carbohydrates one gram yields 4.1 calories.
Fat one gram yields 9 . 3 calories.
The average working man of 20 kilos weight, needs a ration of 30-40 calories for each kilo.
The average resting man of 20 kilos weight, needs 30 cal. per kilo. The average sleeping man of 20 kilos weight, needs 25 cal. per kilo.
Upon the basis of calorific values various diet tables have been
FOOD VALUES
273
made, by the use of which the needs of individual patients can be met. The following, for typhoid patients (enteric fever), is selected from a set of such diet charts prepared by Dr. Frances C. Van Gasken and Dr. Mary P. Rupert for use in the Woman's Hospital of Philadelphia.
TABLE A
|
Portion. |
Food. |
P. |
F. |
C. |
Calories. |
|
•2 nints |
Milk (whole) . |
c;i |
e 4 |
66 |
Q7C |
|
i pint. . |
Meat broth |
20 |
.5 |
89 |
|
|
? |
EgKS. . , |
24 |
16.5 |
24O |
|
|
i nint |
Lemon or orange jelly. . |
8 5 |
12 . <; |
72 |
|
|
3 oz |
JMilk sugars |
I r |
7? |
2Jtf |
|
|
103 |
71 |
143-5 |
I696 |
TABLE B
|
Admissible. |
Grams. |
p. |
F. |
C. |
Approxi- mately 200 C. |
|
|
8 oz |
Gruel (with milk) |
(200) |
4 |
4 |
12 |
« |
|
2 tablespoons |
Rice well cooked |
(r0) |
2 |
•JQ |
it |
|
|
4. oz . |
Junket 4~ sugar |
(31) |
, |
II |
tt |
|
|
•? oz |
Custard |
(80) |
r |
2 |
IO |
n |
|
2 tabelspoons . . . |
Ice cream |
(25) |
1 |
7 |
9 |
n |
|
I OZ . |
Cocoa |
(25) |
C |
7. c |
t( |
|
|
Cognac |
2C |
« |
||||
|
Black coffee |
225 c.c. |
,. |
||||
From Table B, articles may be selected at discretion. The total calorific value of food for each twenty-four hours should reach the following averages :
Febrile period
Proteids. . . . 300 cal.
Fats 405 cal. Convales-
Carbohy- drates i>3oo cal.
cent period
Proteids. . . . 480 cal.
Fats 540 cal.
Carbohy- drates 1,260 cal.
Total 2,005 cal.
Total 2, 280 cal.
274 ANATOMY AND PHYSIOLOGY
Animal Heat. — An internal temperature of about 100° F. is necessary to the normal activity of the body tissues. This, the tissues themselves can accomplish with proper materials in the form of food, and oxygen for the chemical work, the latter being supplied in the air we breathe.
The great source of animal heat is in the most active tissues— muscles and glands; the heat produced in these is equalized in all tissues by the circulating fluids.
The kind of food which is eaten has a direct effect upon the production of heat; protein substances yield more than starchy foods, while fats yield more than proteins and starches together.
The ingestion of food causes a rise of temperature, due both to the chemical and mechanical work of the digestive organs. This rise is normal.
As the body is continually generating heat so it is continually losing it in various ways — by radiation to the surrounding atmos- phere, by conduction to the clothing, by evaporation from the lungs and skin, etc., etc.
In cold weather heat production is desired. This can be accom- plished by selecting heat-generating foods, by taking hot foods and by muscle exercise; the heat thus generated can be conserved by clothing the body in materials which prevent radiation and con- duction, as wool or silk. In hot weather heat production is to be avoided and heat dissipation is sought; this is facilitated by the selection of starchy and protein foods, taking cool drinks and wear- ing lighter garments, as cotton or linen.
For. health and comfort it is necessary that a proper* internal relation be maintained between heat production and heat dissipation. For this, the body possesses its own self-regulating mechanisms; for example, muscle exercise produces heat, but the associated activity of the sweat glands so favors heat escape, that the injuri- ous effect of excessive body heat is prevented. Again, the viscera concerned in digestion (notably the liver) generate much heat; by the blood it is carried to the cooler extremities.
A high temperature of the surrounding atmosphere so affects the nerve centers, that the respiratory function is stimulated and evaporation from the lungs increased, at the same time activity of the skin is very marked and evaporation of perspiration follows.
RANGE OF TEMPERATURE 275
These natural processes of mutual accommodation result in preserving a necessary uniform temperature of the body, which makes it independent, within reasonable limits, of external sur- roundings. The normal temperature, 98.4° F., is maintained so long as the proper balance is preserved between heat production and heat escape. Elevation of temperature is caused when produc- tion is too rapid or dissipation is too slow. Very high temperature indicates excessive metabolism and impaired dissipation. (Another result of excessive metabolism is seen in the wasting of the body in fevers, as typhoid fever.)
Subnormal temperature indicates diminished tissue change or metabolism, suggesting impairment of vitality. (A temperature of 77° F. is followed by death, as cell activity cannot go on in a temperature so low.)
Range of normal temperature. — The normal adult tempera- ture is 98 . 4° F. in the axilla, in the mouth slightly higher. It is a degree higher in the rectum.
During early life when metabolism is active it is slightly higher than in later years. In old age it is often a degree higher than in middle life.
A difference of a degree is noted, in health, between the tem- perature of early morning and evening, for example, at 5 A. M. and
5 P- M-
Average range of body temperature for different ages :
In infancy 99~99 • 5
At puberty 99
In adult life:
Axillary 98 . 4
Oral 98.8
Rectal 99 . 2
Practical Conclusions and Clinical Notes
The temperature of a patient should be taken before a meal, or after digestion, not during it.
In cold weather hot foods containing fats are appropriate for the generation of heat; in hot weather starchy foods and cool drinks are in order.
Alcohol causes a temporary sense of warmth by quickening the circulation, but this is followed by dilation of the surface capillaries
276 ANATOMY AND PHYSIOLOGY
and a consequent radiation of heat. The use of alcohol before exposure to a low temperature should be avoided, unless some very reliable measure is taken for preventing surface radiation.
Muscle exercise is accompanied by dilation of surface vessels and escape of heat; this continues for some time after the exercise has ceased, therefore, care should be taken to guard against too great loss of heat and a consequent "cold" due to chilling of the surface, especially when exposed to a draft of air.
The fact that the body loses heat rapidly by conduction, should warn the nurse against putting cold garments on a delicate patient, and especially against placing a patient in a cold bed. Remember that the body of the patient must furnish the heat to warm the bed and this makes an unnecessary demand upon vitality already impaired by illness.
Small animals need more heat relatively than large ones because their surface is greater in proportion to their bulk, conse- quently they radiate more heat. During the first three days of the infant's life its metabolism falls; it then begins to rise and reaches the normal average for its size after about two weeks.
Practical point.- — Wrap the new-born child and the young infant more warmly than it seems to need. Remember that it is not yet able to manufacture sufficient heat to keep it comfortable.
Influence of work upon metabolism — it accelerates the proc- esses, with increased consumption of oxygen and elimination of carbon dioxide.
Influence of light — similar in effect (although slight in degree) because light stimulates muscle and tissue tone.
Influence of darkness — It retards metabolism from absence of surface stimuli.
CHAPTER XIX THE NERVE SYSTEM
CEREBRO-SPINAL AND SYMPATHETIC DIVISIONS, NERVE TISSUES AND THE SPINAL CORD
The preceding chapters have been devoted to the study of many organs grouped into systems for different purposes. Of some we can say that their functions are exercised consciously and under voluntary control; others are so exercised to a partial extent only; as the muscles of the extremities and those of respira- tion. Still others are absolutely beyond our control — as the heart, the stomach and intestine, and others. We are, therefore, pre- pared to find in the nerve centers of the body, a wonderful plan for providing nerve force that shall stimulate the activities of these widely differing organs, and at the same time bring them into one harmonious whole.
The body functions are classified as voluntary and involuntary, so the nerve system is arranged in two divisions— belonging respectively to voluntary and involuntary processes, the first being called the cerebro- spinal division; the second, the sympathetic division.
NERVE TISSUES
The foundation cells of which nerve tissues are composed are microscopic in size and called neurons. A neuron consists of a nucleated cell body, an axon, and terminal divisions.
The cell body has short branches called dendrites, one of which (sometimes two) grows -longer to form the axon or axis cylinder which becomes a nerve fiber.
Note. — The term nerve cell is often used to signify the cell body of a neuron.
When the axon is invested with a sheath, or medulla, it is a medullated nerve fiber, and such are found in voluntary muscles and all sensitive parts of the body. Axons without sheaths are
277
278
ANATOMY AND PHYSIOLOGY
known as non-medullated nerve fibers, and such are found in in- voluntary muscles and in the walls of internal organs.
Structures composing a medullated nerve fiber:
1 . The axon or axis-cylinder.
2. Medulla or myelin (white substance of Schwann).
3. Neurilemma, a transparent membrane inclosing the myelin (sometimes absent).
Dendrites
Nerve cell
Axon -
A medul- lated fiber
Medullated • fiber
Nerve cell
FIG. 172.
FIGS. 167, 168.— NERVE CELLS.-
FIG. 173- -(Brubaker.}
Structures composing a non-medullated nerve fiber:
1. The axon or axis-cylinder.
2. Neurilemma (sometimes absent).
Medullated nerves are found in voluntary muscles, skin, mucous and serous membranes, joints and special sense organs. They constitute the main portion of the Cerebro-spinal Division.
Non-medullated nerves are found in glands, vessels, hollow viscera, and muscle fibers at roots of hairs. They constitute the main portion of the Sympathetic Division.
The axons or nerve fibers terminate in fine branches, which connect them either with various organs or with the dendrites of other cell bodies, as the case may be.
For want of more accurate language, we say that impulses are
NERVES AND NERVE CENTERS 279
transmitted through fibers either to or from cell bodies. If to the body, the fiber and cell constitute an afferent neuron (afferent, bearing toward); if from the cell body the neuron is efferent (efferent, bearing away) . Afferent nerves are centripetal; efferent nerves are centrifugal.
Important to remember. — The cell body is necessary to the life of the fiber; if separated from the cell body the fiber will die.
The distinguishing characteristics of nerve tissue are sensitive- ness or irritability and conductivity.
THE CEREBRO-SPINAL DIVISION OF THE NERVE
SYSTEM
The brain and spinal cord with their nerves constitute the cerebro-spinal system, and since the brain and cord contain the largest and most important centers, this is often called the central nerve system (Fig. 174).
Nerve tissues in the cerebro-spinal system appear to the eye as of two kinds, gray and white. The gray tissue, commonly called "gray matter," is composed of cell bodies and their branches. The so-called " white matter" is composed of medullated fibers belonging to the cells.
A nerve (of the cerebro-spinal system) consists of many fibers bound together; it resembles in appearance a white cord and may be so small as to be distinguished with difficulty, or as large as a child's finger — like the great sciatic nerve.
A nerve is constructed after the same plan as that of a muscle. A connect- ive tissue sheath, (epi-neurium) sends partitions (peri-neurium) between bundles of fibers, and a delicate membrane (endo-neurium) surrounds each fiber.
Nerves divide into branches which may interlace with others or join them in a common sheath, but no fiber ever unites with another. Each one con- tinues throughout the length of the nerve of which it forms a part.
Nerve centers are the gray cell bodies to which nerves belong, and which are necessary to the life of the fibers.
This term is commonly used to signify a collection of cells whose fibers form nerves having a special function, or which pre- side over a group of movements. (A definite collection of gray cells is also called a ganglion.) Motor nerves transmit motor impulses from centers to muscles, while sensory nerves transmit
1 For description of the Sympathetic Division see page 316.
280
ANATOMY AND PHYSIOLOGY
impressions from the various parts of the body to the centers which receive them. We commonly speak of motor nerves as running down, and sensory nerves as running up, referring them to the spinal cord or brain.
THE SPINAL CORD
The spinal cord lies within the spinal canal in the spinal column, being continuous with the brain. It is a round white structure about seventeen inches long, ex- tending from the atlas to the second lum- bar vertebra, where it ends in a slender ter- minal filament which continues to the end of the canal. The thickness is about half an inch, being greater in the lower cervical and lower dorsal regions, making the cervical and lumbar enlargements where nerves are given off for the extremities. It presents a median fissure in front and another at the back, marking off its right and left halves. Other fissures divide each half into anterior, lateral, and posterior columns or tracts.
A transverse section will show that the interior of the cord is grayish in color in- stead of white, and this portion is largely made up of the gray cell bodies and their branches, arranged in masses which are con- tinuous throughout the length of the cord.
The section will also show that the area occupied by the gray portion roughly re- sembles two crescents (one in either side), connected together across the middle. The extremities of the crescents are called the anterior and posterior horns.
A canal, called the central canal, runs through the center of the gray portion. It may be traced throughout the length of the cord but is easily seen only in the upper part. It contains cerebrospinal fluid.
The white portion consists of the bundles or tracts of the cord (often called columns, the name tract being applied to divisions of
FIG. 174.— THE BRAIN AND SPINAL CORD. — (Quain, after Bourgery.)
THE DURA MATER
28l
the columns) . There is a general division into three in each half— the anterior, lateral, and posterior tracts. The fibers in the anterior and a portion of the lateral tracts are connected with the cells of the anterior horn. They conduct motor impulses. The fibers in the posterior and a portion of the lateral tracts are connected with the posterior horn, and conduct sensory impressions.
All three columns contain associating A fibers which connect different parts of the cord with each other. These are im- portant.
MEMBRANES OF THE SPINAL CORD
The pia mater. — A delicate membrane which bears the blood-vessels and is very closely applied to the surface of the cord (the vascular membrane of the cord).
The arachnoid (web-like). — Outside of the pia mater, this has been classed among serous membranes because its epithelium secretes a fluid like serum; it is a single fibro-serous sheet of membrane (not a closed sac) which surrounds the cord loosely. The fluid within it (cerebro-spi- nal fluid) protects the cord from friction and vibrations.
The dura mater. — A strong white fibrous membrane, tubular in shape, in ! which the cord is loosely suspended. It is attached above to the margin of the foramen magnum.
The space between the dura and the arachnoid is the subdural space; that between the arachnoid and pia is the subarachnoid space; they contain cerebro-spinal fluid. The subarachnoid space is largest in the lower portion. (The fluid in this space mixes with that of the central canal through a small opening in the pia, at the base of the brain.)
The membranes are also called the meninges, and their blood- vessels are the meningeal vessels. Spinal meningitis is inflamma- tion of the meninges of the cord.
FIG. 175. — THREE SECTIONS
OF SPINAL CORD. A, Cervical region; B, thoracic region; C, lumbar region; p, posterior horn; a,
282
ANATOMY AND PHYSIOLOGY
Surgical note. — The operation of lumbar puncture is for the purpose of opening the dura and arachnoid and drawing off a certain quantity of cerebrospinal fluid.
SPINAL NERVES
A spinal nerve is a collection of motor and sensory fibers connected with the spinal cord by two roots — an anterior root running from the motor cells and tracts and a posterior root running to the sensory tracts and cells.
The two roots become imbedded in one sheath at the intervertebral foramen which transmits the nerve from the spinal canal.
Note. — The "ganglion of the root" is a small ganglion on the posterior root where the true root fibers arise.
The ganglion contains the cell-bodies of fibers in the posterior roots; they are neces- sary to the life of these roots. Two axons belong to each ganglion cell; one becomes part of a spinal nerve and ends in a sensitive part of the body (skin, mucous membrane, muscle tissue and lining of joints) ; the other forms a fiber of the posterior root of the same spinal nerve, and enters the cord to become associated with cells of both posterior and
FIG. 177. — MEMBRANES OF SPI- NAL CORD.
i, Dura mater; 2, arachnoid; 3, post, root of nerve; 4, ant. root 'of nerve, divided; 5, pia mater; 6, linea splendens. — (Morris, after Ellis.}
anterior horns. (The fibers of the anterior roots arise in the cells of the anterior horns.)
Clinical note. — Since the spinal nerves contain both motor and sensory fibers, they are called mixed nerves; and since the antero-lateral divisions of the cord are motor tracts, and the postero-lateral divisions are sensory tracts, we can understand how injury in one region will cause paralysis of motion, and injury in the other will cause paralysis of sensation; while injury of a mixed nerve will cause loss of both motion and sensation in the parts to which the nerve belongs.
The next chapter will present the spinal nerves. Certain points of interest in connection with their structure and arrange- ment are here indicated by way of preparation for the study.
It will be noted that the spinal nerves are mixed nerves. That is, they are connected with both ventral and dorsal columns of the cord and contain both motor and sensory fibers until they have
TERMINAL BRANCHES OF NERVES 283
made several divisions, when certain of the sensory fibers are no longer found in the same sheath with the others, but are grouped into nerves which belong to sensitive surfaces.
The terminal branches of all nerve fibers differ with their func- tion. The fibrils of motor spinal nerves end as tiny expanded plates (end plates) which are applied to muscle fibers. (See Fig. 178.) Those of sensory spinal nerves are modified for the purpose of receiving impressions from skin, mucous membranes, joints, periosteum and, to a lesser extent, from muscle and bone tissues.
Sensory nerve-fiber.
Nerve-fiber bundle.
FIG. 178. — MOTOR NERVE-ENDINGS OF INTERCOSTAL MUSCLE-FIBERS OF A RABBIT. Xi5o.—(Siohr.)
The terms origin and distribution are employed in the description of indi- vidual nerves. When applied to motor nerves they are used appropriately and are easily understood, but in connection with sensory nerves it must be remembered that their origin or nerve beginning is by the "terminal branches. " The impulse transmitted by sensory nerves is aroused by the stimulus of impressions on these "branches" and received by the central cell; while that of a motor nerve originates in the central cell, to be transmitted to a muscle where it is really distributed.
In describing mixed nerves it is necessary to conform to custom and speak of the whole nerve as arising by its central connections and as being distributed at the periphery (by which is meant the place where its function is manifested) .
By the above it is evident that the conductivity of the tissue is specialized in the axon fibers; the sensibility in the terminals and cell bodies. The chemical changes in these parts are supposed to be the origin of nerve impulse or nerve force.
CHAPTER XX
Cervical
12 Thoracic
5 Lumbar
5 Sacral
FIG. 179. — DIAGRAM or SPINAL NERVES.
THE SPINAL NERVES
There are thirty-one pairs of spinal nerves. They leave the spinal canal at the intervertebral foramina in the differ- ent regions and are named accordingly.
Cervical. . Thoracic . . Lumbar. .
Sacral
Coccygeal .
8
12
5 5
i
The first cervical, emerging above the atlas, is called the suboccipital.
The cauda equina. — The'spinal cord, being 17 inches long, reaches only to the second lumbar vertebra, therefore the nerves emerg- ing through the foramina below this level must have lain in the canal for some distance before leaving it, especially those which appear in the lowest or pelvic region. If the canal be opened at the back and the cord lifted out, these long nerves are seen hanging from it in a crowd, suggesting the appearance of a horse's tail, the "cauda equina," which there- fore is composed of the lumbar, sacral, and coc- cygeal nerves while they are still in the neural canal. The terminal filament extends down- ward in their midst.
All spinal nerves divide at once into posterior and anterior divisions, both di- visions containing motor and sensory fibers (Fig. 181).
The posterior divisions send nerves to posterior regions of neck and trunk; the anterior divisions (communicate with the sympathetic system, and then) send nerves to anterior and lateral regions of 284
NERVE PLEXUSES
the neck and trunk, and to the upper and lower extremities.1 In all regions except the thoracic, the anterior divisions interlace with each other to form plexuses before giving off nerves.
A nerve plexus is a network formed by branches of several main nerves which have different central connections. (See p. 296.) From the plexus other nerves proceed to their separate distributions.
A nerve made up of fibers which have been part of a plexus conveys impulses to or from several different parts of the spinal cord.
The most important plexuses are:
The cervical plexus (formed by the upper four cervical nerves).
The brachial plexus (formed by the lower four cervical and first thoracic nerves).
The lumbar plexus (formed by the upper three and part of the fourth lumbar nerves).
The sacral plexus (formed by the lower lum- bar, and upper three and most of fourth sacral nerves).
The larger nerves only are described in the text. Resumes are added for reference.
For nerves supplying the joints see page 74.
FIG. 1 80. — CAUDA EQUINA. — (Morris.}
FIG. 181. — SHOWING DIVISION OF NERVE.
i, Dura mater; 2, arachnoid; 3, ganglion of post, root; 4, ant. root; 5, space containing spinal fluid; 6, post, division of nerve. — (H olden.)
1 The communicating branches to sympathetic ganglia are of great importance, serving to connect the cerebro-spinal and sympathetic division into one great nerve system. (They are the white rami communicantes.)
286
ANATOMY AND PHYSIOLOGY
CERVICAL NERVES
Posterior divisions. — These send branches to the back of the head as well as muscles and skin of the neck. Largest posterior branch. — The great occipital (from second cervical), to supply the scalp.
Anterior divisions. — The upper four form the cervical plexus. The lower four enter the brachial plexus.
FIG. 182. — THE PHRENIC NERVES, RIGHT AND LEFT, RUN DOWNWARD ON EITHER SIDE OF THE GREAT VESSELS AND THE HEART. — (After Morris.)
The cervical plexus. — Most of the branches of this plexus supply muscles of the neck (front and side). One exception is the great auricular (auricularis magnus) which supplies the external ear. Another is the—
Most important nerve of this plexus, the phrenic. — It passes downward through the thorax (between the lung and heart) to supply the diaphragm (Fig. 182). Its importance is due to the fact that the diaphragm is one of the principal breathing muscles,
THE BRACHIAL PLEXUS 287
and the nerve has for that reason been called the "internal respira- tory nerve of Bell." (Sir Charles Bell was a famous anatomist in former times.)
The brachial plexus.- — This plexus is so named because most of its branches supply muscles of the upper extremity (including the shoulder) and those connected with it.
First important branch, given off in the neck — the long thoracic. It passes downward along the side of the thorax to supply the an- terior serratus muscle (p. 102). This muscle is used in forced res- piration and -the nerve has been called therefore the "external respiratory nerve."
The greater part of the branchial plexus is situated in the axilla; most of its branches are given off there
f supraspinatus Branches: Suprascapular. to < . f
{ mfraspmatus
Three large cords: Lateral, medial, posterior. Branches of the cords:
From lateral cord: Thoracic, to pectoral muscles.
Musculo-cutaneous, to biceps and brachialis (and
their integument). Upper root of median nerve. From medial cord : Lower root of median nerve.
Thoracic, to pectoral muscles. Cutaneous, to integument of forearm. Ulnar, to ulnar muscles.
f subscapularis, teres major, From posterior cord: Subscapular to < latissimus dorsi (the long sub-
( scapular}.
Axillary, to deltoid and teres minor. Radial, to posterior of forearm and hand.
The three large nerves derived from the brachial plexus are:
The ulnar from the medial cord.
The median from the medial and lateral cords.
The radial from the posterior cord.
The ulnar nerve runs downward in the medial side of the arm, passes behind the medial epicondyle into the forearm, and ends in the palm (Fig. 183).
In the forearm it supplies: Flexor carpi ulnaris.
Flexor digitorum (profundus) partially. In the hand it supplies: Interossei.
Little finger muscles.
Thumb muscles (one and a half).
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ANATOMY AND PHYSIOLOGY
Axillary artery
Suprascapular nerve and artery
Median nerve Brachial artery
Lateral cord
Pectoral muscle
Ulnar nerve and
artery Radial nerve and
artery
Branches to hand
Deep branch
of radial
nerve
Post, interosse- ous nerve
FIG. 183. — BRACHIAL PLEXUS AND AN- TERIOR NERVES.
FIG. 184. — THE RADIAL NERVE.
MEDIAN AND RADIAL NERVES 289
The median nerve runs downward in the arm, close under the border of the biceps muscle. It then passes in front of the elbow joint into the forearm, and continues between the layers of flexor muscles to the palm.
In the forearm it supplies: Flexor carpi radialis.
Flexor digitorum (sublimis).
Flexor digitorum prof undus (partially).
Pronators. In the hand it supplies: Thumb muscles (except one and a half).
The radial nerve passes to the back of the arm, winding across the humerus in the radial groove, under the triceps muscle (Fig.
184).
Just above the elbow it divides into two branches, the deep and superficial branches of the radial nerve.
The superficial branch is a cutaneous nerve. It runs downward in the radial side of the forearm to supply integument of the hand and fingers, posteriorly.
The deep branch passes to the back of the forearm, lying under cover of extensor muscles, all of which it supplies.
Branches of the radial nerve:
In the arm: To the triceps.
To brachio-radialis.
To brachialis (partially). Branches of the deep branch of the radial nerve:
In the forearm: To the extensor carpi radialis (long and
short).
To the extensor digitorum (communis).
To the extensor of index ringer.
To the extensor of little finger.
To the extensors of the thumb.
To the Supinators.
Resume.- — The general distribution of the muscle nerves arising from the brachial plexus, is to deep muscles of the neck and the external respiratory muscle (anterior serratus); to shoulder and axillary muscles; arm, forearm and hand.
The three long muscular nerves derived from the brachial plexus are the ulnar nerve from the medial cord, running down behind the medial epicondyle into the forearm and hand (supplying ulnar muscles, little finger muscles and the interossei, and a part of the thumb group) ; the median nerve from the medial and lateral cords, 19
290
ANATOMY AND PHYSIOLOGY
running down along the medial border of the biceps muscle into the forearm, to end in the palm (supplying the biceps and brachial muscle, all of the flexors of the forearm except on the ulnar side, and most of the thumb muscles) ; the radial nerve from the pos- terior cord, running in its groove to the front of the lateral epicon- dyle, and dividing into the deep and superficial branches of the radial nerve. By the radial and its deep branch all of the posterior mus- cles of the arm and forearm are supplied.
Nerves of the skin of the hand.^Front of the thumb, index, middle, and one-half of the ring finger, the median nerve. Back of thumb, index, middle, and one-half of ring finger, the superficial
FIG. 185.— DORSAL SURFACE OF LFFT HAND. — (Morris.)
FIG. 1 86. — AN INTERCOSTAL NERVE. — (H olden.)
branch of the radial nerve. Both front and back of little finger and one-half of ring finger, the ulnar nerve.
Points of interest. — The ulnar nerve, in the arm, is with the inferior pro- funda artery and passes behind the medial epicondyle (it may be easily felt in the groove behind the epicondyle, where pressure causes a sensation of pain and tingling as far as the little finger). In the forearm it is on the ulnar side of the ulnar artery and they pass in front of the wrist.
The median nerve, in the arm, is with the biceps muscle and brachial artery, and they pass in front of the elbow; in the forearm, it lies between the deep and superficial muscles and passes with their tendons in front of the wrist.
The radial nerve, in the arm, lies in the groove for the radial nerve be- tween two heads the triceps muscle, with the superior profunda artery, and comes to the front of the elbow.
Its superficial branch, in the forearm, is on the radial side of the radial artery; it winds around behind the wrist-joint.
THORACIC NERVES
2-91
The deep branch of the radial nerve is in the back of the forearm with the dorsal interosseous artery; they do not extend below the wrist.
(For the distribution of nerves to the principal joints, see page 74.)
THORACIC NERVES (FIG. 186)
There are twelve pairs of thoracic nerves :
Posterior divisions: — These send branches to muscles and skin of the back.
Anterior divisions. — These form the intercostal nerves; the first assists in the formation of the brachial plexus. All run in the grooves under the borders of the ribs, supplying in- IJ tercostal muscles, also the skin over the muscles. The lower ones also supply upper abdominal muscles and skin. They accompany intercostal arteries.
LUMBAR NERVES
There are five pairs of Lumbar Nerves.
Posterior divisions. — These send branches to muscles of the back; and skin of the back, hip, and sacral region.
FIG. 187.— THE FEMORAL NERVE.
i, Femoral nerve; 2, 3, small , . . . nerves from lumbar plexus; 4, 5.
Anterior divisions.— The up per three 5,7,8,9,10, n, n, branches of and a portion of the fourth form the femoral "erve; I2> «'. *3> M,
long saphenous nerve and its lumbar plexus. The remainder of the branches; 15, obturator nerve; 16,
23, external cutaneous nerve.—
fourth and the whole of the fifth form
the lumbo-sacral cord (Fig. 187).
The lumbar plexus.— This plexus lies within the abdomen, in the substance of the psoas muscle. Its branches supply abdominal walls, and front and sides of the thigh (also integument of both regions). They are all given off in the abdomen.
Branches: the principal are:
ANATOMY AND PHYSIOLOGY
Ilio-hypogastric, cutaneous to hypogastrium, and over the ilium (dorsum). Inguinal, to internal oblique and transversus muscles. Genito-femoral, to round ligament of uterus, cremaster muscles of spermatic cord.
Obturator, to the external obturator and the four adductors. Femoral, to the quadriceps muscle (rectus and three vasti).
The femoral nerve (anterior crural} is the largest branch of the lumbar plexus. It passes under the inguinal ligament, from the abdomen, into the thigh (on the lateral side of the femoral artery), and breaks up at once into branches — cutaneous and muscular, for the four large divisions of the quadriceps extensor muscle and the integument which covers them.
The long saphenous branch of the femoral nerve is the longest nerve in the body, running nearly the whole length of the extrem- ity; it supplies integument only, on the medial side of the leg and foot.
The lumbo-sacral cord passes into the pelvis to unite with sacral nerves and to form the sacral plexus.
SACRAL NERVES
Posterior divisions. — These send branches to muscles and skin of the back of the pelvis.
Anterior divisions. — The upper three, and greater part of the fourth, join the sacral plexus.
The sacral plexus.- — The branches of this plexus supply the muscles within and around the pelvis, the posterior part of the thigh, and the entire leg and sole of the foot.
Branches: (All leave the pelvis through the great sciatic foramen.)
Gluteal, two (superior and inferior} to glutei muscles.
Pudic, to the levator ani, rectum (sphincter ani), perineum, and external genital organs. (Reenters the pelvis through small sciatic foramen.)
Small sciatic, to posterior thigh and external genital organs. This is a cutaneous nerve.
Great sciatic, to posterior thigh, and entire leg and foot (except medial border) muscles and skin.
The great sciatic nerve is the largest nerve in the body. It leaves the pelvis by way of the great sciatic notch and runs down- ward between posterior thigh muscles to the popliteal space, where it divides into tibial and common peroneal nerves (Fig. 188).
SCIATIC NERVE
2Q3
The only portion of the great sciatic nerve which is not covered by muscles, lies in the deep groove between the great trochanter of the femur and the tuberosity of the ischium.
Branches:
In the thigh.— To the Biceps, Semitendinosus. Semimembranosus. Calf muscles.
The division of the great sciatic nerve occurs in the upper part of the popliteal space. The tibial nerve (internal popliteal) runs down through the popliteal space (with the popliteal artery and vein) to the leg. It then descends under cover of the calf muscles to the ankle; below the medial mal- leolus it divides into medial and lateral plantar nerves.
Branches:
In the leg. — To the Tibialis posticus. Flexor digitorum (longus). Flexor hallucis.
In the foot. — By medial plantar, to great toe muscles and interossei.
By lateral plantar, to muscles of little toe.
The tendons of the tibialis and two long flexors of toes pass behind the medial malleolus. They extend the foot.
The common peroneal nerve (external popliteal) winds around the neck of the fibula to the front of the leg, and divides into the deep peroneal and superficial pero- neal nerves.
The deep peroneal (formerly anterior tibial) descends to the ankle, and ends on thedorsum of the foot between the first and second toes.
•Gluteal n.
Sciatic n.
' Popliteal artery • Tibial n.
Peroneal n.
Ant. tib. artery
Tibial n.
Post. tib. artery
FIG. 188.— THE SCIATIC NERVE.
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ANATOMY AND PHYSIOLOGY
Branches:
In the leg. — To the Tibialis anticus. Extensor hallucis. Extensor digitorum (longus). Peroneus tertius.
In the foot. — Extensor digitorum (brevis).
The tendons of these muscles pass in front of the ankle-joint. They flex the foot.
The superficial peroneal (musculo-cutaneous) runs downward in the substance of the peroneal muscles to the foot.
Branches:
Muscular. — To the Peroneus longus, peroneus brevis.
Cutaneous. — To dorsum of foot.
Their tendons pass behind the lateral malleolus. They extend the foot.
Tibialis posterior Cruciate ligament
Tibialis posterior
Tibialis anterior
Tendo Archillis
Flexor digitorum
longus -^ Posterior tibial
artery Tibial nerve
Flexor digitorum longus
FIG. 189. — RELATIONS OP PARTS BEHIND THE MEDIAL MALLEOLUS. — (Heath.}
Points of interest. — The superior gluteal nerve, with the superior gluteal artery; the sciatic nerve, with the sciatic artery; and the pudic nerve, with the pudic artery, all pass out from the pelvis through the great sciatic for amen; the pudic nerve and artery return through the small sciatic foramen.
The obturator nerve and the obturator artery pass through the obturator foramen.
The femoral nerve passes under the inguinal ligament on the lateral side of the femoral artery.
THE COCCYGEAL PLEXUS
The remaining sacral nerves and the coccygeal nerve communi- cate in a small plexus, which is important in that it sends branches to the viscera of the pelvis .
NERVE REFLEXES
2Q5
Summary
The spinal nerves are distributed to all skeletal muscles and integument except those of the front of the head, face, and chin. Through sympathetic connections they also supply secreting cells of glands and walls of viscera.
FUNCTIONS OR PHYSIOLOGY OF THE SPINAL CORD AND SPINAL NERVES
The spinal cord is so intimately connected with the brain by conducting fibers in the tracts, that it is impossible to explain all of its functions without referring to the brain, but certain ones
{sp.c.
FIG. 190. — DIAGRAM SHOWING THE STRUCTURES INVOLVED IN THE PRODUCTION OF
REFLEX ACTIONS. — (G. Bachman.)
r.s., Receptive surface; af.n., afferent nerve; e.c.t emissive or motor cells in the anterior horn of the gray matter of the spinal cord, sp.c; ef.n., efferent nerves dis- tributed to responsive organs, e.g., directly to skeletal muscles, sk.rn., and indi- rectly through the intermediation of sympathetic ganglia, sym. g., to blood-vessels, &.fl.,'and to^glands, g. The nerves distributed to viscera are not represented.
may be exercised independently, and a few of these will be con- sidered briefly in this connection.
The spinal cord a center for reflex action. This is one of the most important of its functions and the simplest form of nerve and muscle action. Acts which may be performed without thinking of them are reflex, also those which are performed independently of the will although with perfect consciousness.
296 ANATOMY AND PHYSIOLOGY
For example, we shiver with cold, or tremble from excitement; these are purely reflex acts of which we may be conscious although we are unable to control them; the action of the heart is some- times very evident to the senses, as in palpitation, etc., but beyond our power to regulate.
In each lateral half of the cord the cell tissue is grouped in crescents. Fibers in the posterior tracts transmit sensory impulses from various parts of the body to cells in the posterior horns of the crescents. Fibers in the anterior tracts transmit motor impulses from cells in the anterior horns to various parts of the body (their axons arise in cells of the anterior horns) (Fig. 190).
Here we have the simple reflex arc, or the apparatus for reflex muscle action. — A sensory or afferent nerve receives an impression, and transmits a series of impulses to the spinal cord. These are received by a cell which in its turn is stimulated, and liberates energy to be conducted by a motor or efferent nerve to a muscle, and the muscle contracts; or to a gland— the gland secretes; or to a vessel wall — the caliber is changed. These acts are comparatively simple.
Most muscle activities, however, are complex, requiring the combined action of several organs; in these cases many motor cells and nerves must be stimulated, and this is accomplished by means of additional neurons within the cord, whose fibers associate the activities of different regions. For instance, an unsuspected blow upon the hand is followed instantly by a drawing back of the hand and arm — most of the muscles of the upper extremity will have been called into action; in other words, many motor cells (in the lower cervical region of the cord) have been stimulated to a sudden liberation of energy, showing the effect of one stimulus when conducted by connecting fibers to many cells in the cord.
Walking was in the beginning a purely voluntary act, but the centers which control it become, by education, independent,. and it takes its place among the reflexes. So with piano-playing, and many other acts.
The complicated motor response is provided for by the arrangement known as a nerve plexus, which is formed by interlacing branches of nerve trunks. An illustration is seen in the brachial plexus, where five large trunks are reduced to three while passing under the shoulder joint; then, by branching and interlacing, the fibers are so arranged that each nerve contains fibers
TENDON REFLEXES 297
from two or three of the main trunks proceeding from the plexus and is dis- tributed to a group of muscles acting in harmony.
Tendon reflex. — A familiar example of tendon reflex is the "knee jerk" or patellar reflex. This may be elicited by striking the patellar tendon when partly stretched. The impression thus produced quickly reaches the motor cells which innervate the quadriceps muscle, and the leg is slightly and suddenly extended. (There are several tendon reflexes.)
Skin reflex. — Irritation of the sole of the foot causes the plantar muscles to contract, a plantar reflex. Scratching the skin of the side of the abdomen causes contraction of abdominal muscles, abdominal reflex. (There are other skin reflexes.)
The spinal cord contains centers for controlling the tone of vessel walls or vascular tone. Also for stimulating the action of secreting glands, and for muscle action of viscera. These functions are exercised through the sympathetic ganglia with which it is widely connected; they will be referred to in Chapter XXII.
Finally, it contains centers which influence (or control) certain processes of nutrition — trophic centers.
It appears at once that the spinal cord is able, from the wide distribution of its nerves, to provide for most of the activities of the body.
Taken as a whole it may be regarded as a great common center of sensation and motion; and because of many connecting fibers running upward, downward, and transversely, it can combine and to some extent regulate the functions of many different parts, so that systematic groups of movement, or series of movements, may be executed by organs more or less distant in the body.
In other words, the spinal cord can to some extent coordinate the functions of the spinal nerves and skeletal muscles.
To repeat the functions of the spinal cord, they are to preside over:
1. Reflex action.
2. Muscle tone.
3. Vessel tone.
4. The action of secreting glands.
5. Nutrition (trophic action).
6. Coordination of skeletal muscles.
2p8 ANATOMY AND PHYSIOLOGY
These may all be exercised independently of the brain, by cells in the posterior and anterior horns with their sensor and motor nerve connections. (Other functions will be mentioned in connec- tion with those of the brain.)
The function of the spinal nerves is to connect all parts of the body (except face, chin and anterior part of head) with the spinal cord, for the purpose of conducting sensor and motor impulses to and from the cord.
NERVE STIMULUS
In referring to motor nerves we have thus far mentioned their natural stimulus only, that is — the impulse generated by a sensor or motor cell. The electric current applied to a motor nerve in any part of its course will excite its activity, showing in muscle contrac- tion, etc. This is an artificial stimulus, and the most powerful one known.
CHAPTER XXI THE BRAIN AND CRANIAL NERVES
The cerebro-spinal or central nerve system comprises the Brain and Spinal Cord with their nerves. The spinal cord and its nerves are already described in Chapters XIX and XX.
The brain1 is ovoid in shape, composed of gray cells and white fibers, situated within the cranial cavity and continuous through the foramen magnum with the spinal cord.
FIG. 191. — THE EXTERNAL SURFACE OF THE BRAIN. — (Deaver.)
The surface consists of gray cells and their branches and is called the cortex of the brain, while the interior is white, with several ganglia imbedded within it.
The surface or cortex of a well-developed brain is marked by many fissures, separating curved ridges called convolutions (or gyres), the number and depth of which correspond with the degree of development, the brain of a new-born child being comparatively smooth.
1 A review of pages 277 and 278 is recommended before studying the description of the brain.
299
3oo
ANATOMY AND PHYSIOLOGY
The white portion is composed of white fibers. They run in many directions. Some connect the different main divisions of the brain; others run from one part of the cortex to another; others still, in great number, connect the brain and spinal cord (Fig. 192). Taken together, they make up the mass of the brain itself.
The brain has four principal parts, the cerebrum, cerebellum, medulla oblongata, and pons Varolii.
FIG. 192.
The letters mark white fibers. They connect the cortex with other parts, also different parts of cortex together. Many fibers are seen to pass through the basal ganglia. The Roman numerals indicate nerves. — (Brubaker, after Starr.}
The cerebrum is the largest division and occupies nearly the whole cranial vault. It is divided into two hemispheres, right and left, by a longitudinal fissure. At the bottom of this fissure white fibers are seen to pass from one side to the other, thus forming a transverse commissure, connecting the hemispheres, and called the corpus callosum (Fig. 193). Each hemisphere is marked off by specially deep fissures, into lobes, the principal ones being the frontal, parietal, occipital, and temporal. The principal fissures between the lobes are: the fissure of Rolando between the frontal and parietal; the parieto-occipital, between the parietal and occi-
THE BASAL GANGLIA
3OI
pital; and the fissure of Sylvius, between the temporal lobe below and the frontal and parietal above it.
Important note. — The fissure of Rolando is often called the central fissure, and the convolutions in front of and behind it, are called the central convolutions (anterior and posterior central).
Within the white substance of the hemispheres are the largest ganglia in the brain, and since they are situated near the base, they are called basal ganglia. They are the optic thalamus, the lentiform nucleus, and the caudate nucleus (Fig. 195). The white
FIG. 193. — MEDIAN SURFACE OF A HEMISPHERE, SHOWING THIRD AND FOURTH VENTRICLES; ALSO THE CORPUS CALLOSUM DIVIDED, AND THE STRUCTURE OF THE CEREBELLUM WITH THE PONS IN FRONT OF IT. THE PITUITARY BODY is SUSPENDED FROM THE FLOOR OF THE THIRD VENTRICLE. — (Deaver.)
matter between the optic thalamus and the other two, constitutes the internal capsule. Here are the fibers which connect centers in the cortex with those in the spinal cord; hence the great importance of the internal capsule.
The white fibers of the cerebrum are classified in three groups: i. those which connect different parts in the same hemisphere, or association fibers; (Fig. 201) 2. those which connect parts in one hemisphere with similar parts in the other, or commissural fibers; 3, those which connect the cortex with the ganglia of the brain and spinal cord, or projection fibers (Fig. 192 shows projection fibers of the right half of the brain).
The hemispheres are not solid, but each encloses a cavity called the lateral ventricle, shaped like the italic letter / with a
302
ANATOMY AND PHYSIOLOGY
projecting arm (laterally and downward). The extremities of the ventricle are called horns; the anterior horn being in the frontal lobe, the posterior horn in the occipital, and the lateral or descend- ing horn in the temporal lobe. The great ganglia of the brain are in the floor of the lateral ventricles (hence called basal ganglia).
The lateral ventricles are named like the hemispheres — right and left.
(There are certain other basal ganglia which are important, although smaller in
size.)
The cerebellum, or little brain, also consists of white matter covered .6 with gray. It has two hemispheres which are not definitely separated like the hemispheres of the cerebrum, but are connected by a median por- tion called the vermis, or worm. The convolutions are but slightly curved and are called ridges, and the furrows (or sulci) are very deep; a section shows that they are so arranged as to resemble the branches of the tree called arbor mta, (Fig. 193).
The cerebellum is situated in the
FIG. 194. — PONS AND MEDULLA, ANTERIOR SURFACE.
i, 2, 3, Structures belonging to cerebrum; 4, crura of cerebrum; 5,
pons varolii; 9, 10, n 13, 14 cerebellar fossae of the occipital bone.
lateral surface and membranes of
medulla; 7, pyramid; 8, decussa- The medulla oblongata, although
median' ES^USr, *%$* SitUated ™Mn ^ Cram'Um ^ fr°nt nerves; 28, 29, ist and 2 d spinal of the foramen magnum), is the up-
nerves.— (Sappey.) " , ^
per enlarged portion of the spinal cord and, like it, is white externally and gray within.
Its anterior columns are called the pyramids or pyramidal tracts, and consist of motor fibers passing downward from the brain. Most of the fibers of each pyramid cross to the opposite side, appearing to interlace in the median fissure, the decussation of the pyramids, to form the crossed pyramidal tract; the others pass downward as the direct pyramidal tract and cross, a few at a time, at lower levels in the cord. Thus it is that motor fibers coming from one side of the brain pass to the other side
VENTRICLES OF BRAIN 303
of the cord, and this is the explanation of paralysis of one side of the body, following injuries of the other side of the brain.
The posterior columns of the medulla contain sensory fibers going upward to the brain, while the lateral tracts contain both motor and sensory fibers (like the cord). Most of the sensory fibers also cross at different levels.
The medulla contains centers for the most important nerves of the body — respiratory, cardiac, vaso-motor, etc.
The pons Varolii, or bridge of Varolius, is situated in front of the medulla, below the cerebrum and cerebellum, and so named because fibers run through it from all three of the other parts of the brain, as though it were a bridge between them. It, also, is white externally and gray within, and is not unlike the cord, although in a still more modified form than the medulla.
Two large nerve bundles are seen diverging from the anterior border of the pons, the crura of the cerebrum (often called peduncles). They contain all of the motor and sensory fibers of the cerebrum which pass between the pons and the cord. The fibers to and from the cerebellum form peduncles of the cerebellum (smaller in size).
THE FIVE VENTRICLES OF THE BRAIN (Fig. 195)
The five ventricles are different portions of one cavity, which is continuous with the central canal of the spinal cord. The two lateral ventricles have been mentioned. The third ventricle is between them, and the fourth ventricle is behind the third, being in the medulla and pons; some of the most important nuclei or centers of the body are imbedded in the floor of the fourth ventricle.
Each lateral ventricle communicates with the third through an opening called the foramen of Munro; the third communicates with the fourth through the aqueduct of the cerebrum (aqueduct of Sylvius), a slender canal in the crura and pons; and the fourth ends in the central canal of the cord. These spaces are therefore continuous, and they contain cerebro-spinal fluid.
The so-called fifth ventricle is not a portion of the general cavity — not a true ventricle. It is a narrow space in front of the third, having no opening whatever.
Clinical notes. — Hydrocephalus is caused by an accumulation of fluid in the ventricles, enlarging them and pressing upon the brain substance, and
304 ANATOMY AND PHYSIOLOGY
subsequently upon the bones of the skull. It is very likely to occur in children who have rachitis, or " rickets."
By a foramen in the arachnoid membrane, the ventricular cavities and central canal communicate with the subarachnoid space, allowing cerebro- spinal fluid to flow through all of these parts. (See p. 281), Arachnoid.
Surgical note. — Because of this, the operation of lumffar puncture may relieve the pressure of hydrocephalus.
A similarity in structure and arrangement of parts is plainly evident in the brain and spinal cord. Recall the cord — a collection of nerve fibers,
FIG. 195. — THE VENTRICLES, SHOWING BASAL GANGLIA IN THE FLOOR OF THE LATERAL VENTRICLES. — (Hirschfeld and
a, Anterior portion of corpus callosum; ft, caudate nucleus; c, location of lentiform nucleus; d, optic thalamus; h, i, quadrigeminal bodies; g, third ventricle; o, fourth ventricle; p, medulla. The fifth ventricle is in front of e.
the greater number running up or down, but with many passing from one side to the other; a central canal surrounded by collections of "gray matter"; two lateral halves connected by transverse commissural fibers.
These parts may all be traced in the brain. The central canal extends through the medulla and pons into the cerebrum, expanding into a general ventricular cavity. Gray matter (ganglia) lies close to this canal, even pro- jecting into it. The white fibers are here, but they diverge on every side, and many take new directions; also the halves of the brain are connected by transverse (commissural) fibers (the corpus callosum). The brain has one
THE DURA MATER 305
part not found in the cord (and a most important part), viz., a covering of "gray matter," or cortex.
THE MEMBRANES OF THE BRAIN
These are three in number, the pia mater, arachnoid, and dura mater, like those of the cord, and continuous with them.
The pia mater fits closely to the brain, following all convolu- tions and uneven surfaces; it is necessary to the life of the brain, as periosteum is to bone, and for the same reason — it bears the blood- vessels which nourish it.
The arachnoid lies close to the pia but stretches across the furrows, leaving subarachnoid spaces for cerebro-spinal fluid as in the spinal cord. The largest spaces are at the base of the brain where the greatest irregularities of surface are found.
The dura, firm, white and tough, covers the others loosely and lines the entire skull, taking the place of periosteum. It has a number of meningeal arteries branching in its substance, for its own nourishment and the nourishment of the skull bones (since it is their internal periosteum). It sends layers between the large divisions of the brain — one between the hemispheres of the cere- brum is called the falx cerebri, and one stretched over the cere- bellum is called the tentorium cerebelli. They support the weight of portions of the brain in different positions of the head.
The dura also presents several large veins called sinuses which collect the blood from the brain. The largest are the sagittal (longitudinal) running from front to back in the median line, and the two transverse sinuses (lateral) right and left which end in the internal jugular vein at the jugular foramen.
Surgical note. — The transverse or lateral sinus lies partly in a deep groove on the mastoid bone (sigmoid groove) and this adds to the gravity of operations in the mastoid region.
Clinical note. — Inflammation of the membranes is meningitis. When affecting the dura it is p achy meningitis; when it is of the pia and arachnoid, it is leptomeningitis.
THE CRANIAL NERVES
There are 12 pairs of cranial nerves. They are seen at the base of the brain and leave the skull through various foramina in
306
ANATOMY AND PHYSIOLOGY
the cranial bones. Some are nerves of motion, some of sensation and some are mixed (Fig. 196). They are named as follows:
1. Olfactory. 7. Facial.
2. Optic. 8. Acoustic or auditory.
3. Oculo-motor. 9. Glosso-pharyngeal.
4. Trochlear, or pulley nerve. 10. Vagus, or pneumo gas trie.
5. Trifacial, or trigeminus. u. Spinal accessory.
6. Abducens. 12. Hypoglossal.
First, olfactory
Third, oculo-motor Fourth, pathetic
(trochlear) Fifth, trifacial Sixth, abducens Seventh, facial Eighth, auditory
Ninth, glosso-pharynxal
Tenth, vagus
Eleventh, spinal accessory
Twelfth, hypoglossal
FIG. 196. — BASE OF BRAIN AND CRANIAL NERVES, SHOWING RELATION OF THE PONS MEDULLA, AND CEREBRUM. — (Monat and Doyen; Brubaker.)
The first, or olfactory (Fig. 196), is the nerve of smell. Being sensory it is traced toward the brain.
Minute nerves from the upper part of the nasal mucous membrane (olfactory region), pass up through the sieve-like plate of the ethmoid bone and enter the olfactory bulb; from the bulb, a soft band of fibers called the olfactory tract proceeds to the brain; most of them finally reach the temporal lobe, where they end in the center for the sense of smell, or olfactory center.
The second, or optic (Fig. 197), is the nerve of vision, begins in the retina.
It
The retinal fibers are gathered to form the nerve, which passes through the optic foramen into the cranial cavity. The two optic nerves meet above the body of the sphenoid bone and most of the fibers cross each other there,
THE TRIFACIAL NERVE 307
forming the optic commissure (or chiasm), and then proceed to certain ganglia, from which the visual impressions are conveyed to the visual centers of the occipital lobes. (Fig. 194, 16, optic chiasm.)
The third, or oculo-motor (Fig. 197), is the mover of the eyes. It proceeds from the base of the brain and enters the orbit, to sup- ply four of the muscles of the eyeball, and also the elevator of the upper lid. (Eye muscles thus supplied: Superior, inferior, and internal recti, and inferior oblique. See p. 343, orbital muscles.)
By the action of the first three the eye is turned upward, downward and inward; the inferior oblique turns it upward and outward.
a 7 10 v
FIG. 197. — NERVES OF THE ORBIT.
i, Optic nerve; 2, Oculo-motor (3d) ; 5, abducens (6th). Other figures mark various branches. 10, Ciliary ganglion. — (Sappey.)
The third nerve supplies also the circular fibers of the iris which contract the pupil of the eye, and the accommodation muscle — by which the eye is focussed for viewing objects at different distances.
The fourth, or trochlear nerve, is so called because the tendon passes through a loop of fascia and bends around like a rope on a pulley or trochlea. It supplies the muscle which rolls the eye downward and outward (the superior oblique muscle).
The fifth, or trifacial (trigeminal), is the great sensory nerve of the face, nose and throat. Some motor fibers for muscles of mastication accompany the sensory fibers and the nerve is described as having two roots; sensory and motor.
The sensory root has a large ganglion, semilunar (or Gasserian) ganglion, and in front of this it is in three divisions, called the ophthalmic, maxillary, and mandibular nerves. The ophthalmic nerve lies in the orbit ; it is the nerve of sensation of the structures contained therein; also of the eyelids and side of the nose. The maxillary nerve appears at the infraorbital foramen. It is the nerve of sensation for the upper teeth and the cheek and temple. The
308 ANATOMY AND PHYSIOLOGY
mandibular nerve is in the infratemporal fossa, and is the nerve of sensation for the lower teeth and structures of the lower jaw. The motor root joins this branch to supply the muscles of mastication.
The nerve of the sense of taste, called the lingual (or gustatory}, accom- panies the mandibular nerve, from the anterior two-thirds of the tongue.
Surgical notes.— Facial neuralgia is sometimes so severe and intractable that the semilunar ganglion is removed by the surgeon. This interferes with sensation of the face, but not with motion.
Three sensitive points on the face where three sensory branches of the trifacial pass through foramina are: the supraorbital foramen, for the supra-
FIG. 198. — THE DISTRIBUTION OF THE THREE DIVISIONS OF THE FIFTH NERVE. —
(Leidy.)
orbital branch of the ophthalmic; the infraorbital foramen for the infra- orbital branch of the maxillary; the mental foramen for the mental branch of the mandibular. Section of these nerves is sometimes done for facial neuralgia.
The sixth, or abducens, is a motor nerve, supplying the external rectus muscle, which turns the eye outward, or abducts it.
The seventh, or facial (Fig. 199), is a motor nerve. It passes through the channel in the petrous bone called the facial or Fallopian canal (which brings it close to the middle ear). Emerg- ing from the skull it passes forward through the parotid gland, and divides into many branches supplying all the muscles of expression.
ACOUSTIC NERVE
309
Clinical note. — If this nerve is paralyzed, the side of the face supplied by the injured nerve droops and is useless, and the eye fails to close. The face will be drawn toward the «w-injured side by muscles supplied by the opposite nerve; this is plainly seen if the patient smiles, or attempts to whistle.
The eighth, or auditory (acoustic), is a sensory nerve. It has two portions — the cochlear, or proper nerve of hearing, and the vestibular, or nerve of equilibration. Both pass from the internal ear through the internal auditory canal to the medulla. (See p. 333, Nerves of the Internal Ear.)
FIG. 199. The figures mark the branches of the seventh or facial nerve. — (Holdcn.)
The ninth, or glosso-pharyngeal, is a mixed nerve. The motor fibers pass from the medulla through the jugular foramen and supply the muscles of the tongue and pharynx, as its name suggests. The sensory fibers convey sensations of taste from the tip and back part of the tongue. Bitter things are especially appreciated by the glosso-pharyngeal.
The tenth, or vagus (pneumogastric), is a mixed nerve. It is traced from the medulla through the jugular foramen.
Branches. — Laryngeal to larynx; pharyngeal to pharynx; car- diac to the heart; pulmonary to the lungs; and others, indirectly, to the stomach, liver, spleen, and intestines.
It regulates the action of the heart and the act of swallowing;
3io
ANATOMY AND PHYSIOLOGY
it is the sensory nerve of the air passages from the larynx down, and of the alimentary tract from the pharynx down.
The eleventh, or spinal accessory, is traced from the medulla through the jugular foramen, with the ninth and tenth. It supplies the sterno-mastoid and trapezius muscles with motor nerves. (A portion of it is accessory to the vagus.)
The twelfth, or hypo-glossal (under the tongue), supplies the muscles of the tongue and those connecting it with the jaw and hyoid bone; also the ribbon muscles in front of the neck.
Summary
The nerves of the cerebro-spinal system are distributed to all voluntary muscles, and to all sensitive structures, as skin, mucous membranes, lining of joints, and periosteum. They are the nerves of conscious life.
CRANIAL NERVE SUPPLY TO CERTAIN MUSCLE GROUPS
|
Region. |
Muscles. |
Name. |
|
Head |
Of scalp and face |
Facial or 7th |
|
Of tongue |
Hypo-glossal or i2th |
|
|
Of mastication — temporal, masseter, buccinator, two pterygoids |
Trigeminal or 5th |
|
|
The digastric assists in mas- tication |
5th and 7th |
|
|
Of the orbit — inferior ob- lique, levator palpebrae, su- perior rectus, inferior rectus, internal rectus |
Oculo-motor, or 3d. |
|
|
external rectus |
Abducens or 6th |
|
|
superior oblique . |
Trochlear, or 4th. |
|
|
Neck, lateral |
S terno-mastoid. |
|
|
Neck, posterior |
Trapezius |
S. accessory or nth. |
|
Neck, anterior |
Ribbon muscles, also the tongue . |
Hypo-glossal or i2th |
|
Pharynx. Larynx. Esophagus |
Vatrus or loth |
|
|
Pharynx and Larynx |
Have also fibers from |
Glosso-pharyngeal, or |
|
9th. |
Certain associated movements of the orbital muscles are of interest. The central connections are so arranged that the external rectus of one eye and the internal rectus of the other move together;
CEREBRAL LOCALIZATION
both eyes turn in the same direction — right or left. The two internal recti, guided by a convergence nucleus, act together when the eyes are directed toward a near object. At the same time the pupil narrows and the ciliary muscle seeks to adjust the range of vision (see p. 338).
FUNCTIONS OR PHYSIOLOGY OF THE BRAIN AND CRANIAL NERVES
The cerebrum presides over all conscious acts, and recognizes all sensations. The anterior portion of the frontal lobes is said to be the region of mental activity or the seat of the intellect.
CONCRLTE CONCEPT
FIG. 200. — THE AREAS AND CENTERS OF THE LATERAL ASPECT OF THE HUMAN HEMICEREBRUM.— (C. K. Mitts.)
The cerebrum not only is the seat of volition, directing the purposive movements of the body, but it also exerts a controlling force, both accelerating and inhibitory, upon many reflex acts which originate as involuntary in their nature. The partial con- trol of respiratory movements has been already alluded to; laugh- ing, weeping, micturition, defecation, and many other acts may be included in the same class.
Cerebral Localizations. — Connections between cortical areas and certain parts of the body have been noted, and their control
312 ANATOMY AND PHYSIOLOGY
over those parts has been demonstrated (Figs. 200, 202). Among them are the centers for face muscles and for the upper extremity, in the anterior central convolution; the centers for articulate speech in the lower convolutions of the frontal lobe. Likewise the centers for the special senses are fairly well known — as for vision and memory in the occipital lobe ; for taste in temporal; for touch in the parietal; and for hearing and smell in the temporal and frontal.
These centers are all connected directly or indirectly, by a complicated system of association fibers (Fig. 201), so that by their various impressions and nerve impulses they are constantly acting with or upon each other.
Illustration. — The faculty of speech implies many previous mental acts. The mind must know and recall the names of things in order to mention them; it must have seen or heard things in order to describe them and to have learned the words which ex- press these conceptions. It may do all this and still be silent, until these many factors are brought to work together under the influence of the center for articulate speech which, as seen in the diagram, is in close connection with those for the larynx, tongue and face muscles. It is this center which determines when these muscles shall be used for speaking instead of for other purposes.
The first use of the faculty of speech probably represents the attempt to reproduce a sound; next the impression of something seen, itself having a sound of its own or a name. Gradually a feeling may come to find expres- sion and so on through the endless line of impressions and memories, the education of the speech-controlling center goes on; auditory, visual, sensory- motor and other centers all contributing to this end.
This is one illustration from many which might be cited, of the value of association fibers. In general terms it may be stated that the most highly organized brain has the greatest number of association fibers, whereby the intellectual faculties of judgment, reasoning and the will are developed.
The centers which govern skeletal muscles belong to the convolutions marked motor and cutaneous in Figs. 200 and 202. Tracing from below upward — the larynx, tongue, face, hand, arm and shoulder, foot, leg and thigh are represented on the lateral surface, in the central convolutions border- ing the Rolandic fissure; while other thigh centers and those for trunk, are found on the medial surface bordering the longitudinal fissure.
Note that a large portion of the cortex is devoted to complex
THE CEREBELLUM
aQ tivities based upon mental pursuits and the acts or states of mind connected with them.
Clinical notes. — These several localizations furnish a guide to the under- standing of various disturbances of the nerve system, since irritation of a given area may cause disordered muscle action in the part which it controls, or, by pressure (as in hemorrhage or apoplexy] the power of motion may be lost (paralysis). The same symptoms may follow softening of the cerebral tissue, the growth of tumors, etc. By carefully observing the condition of the muscles affected, one can often determine the location of a brain lesion. Disturbances of hearing, vision, sensation, etc., likewise indicate the seat of disease or injury.
FIBRES PROPRI&
SUPERIOR LONGITUD- INAL FASCICULUS STRIA TERMINALS \ OF THALAMUS
CINGULUM
UNCINATE FASCICULUS
INFERIOR LONGITUDINAL FASCICULUS
FIG. 201. — ASSOCIATION FIBERS. — (Morris.}
The function of the cerebellum is to associate or coordinate the actions of muscle-groups for the accurate performance of special movements. This is most conspicuously shown in maintaining the equilibrium of the body, whether standing or walking. Injury to the cerebellum results therefore in vertigo and dizziness, in loss of the power to keep one's balance, and of the ability to walk without staggering.
The medulla oblongata contains many important governing centers. Among them are the circulatory and the respiratory centers; these are situated near each other and together they
314 ANATOMY AND PHYSIOLOGY
constitute the "vital knot." Consequently this part of the nerve system presides over processes of the body which are necessary to life itself, and when one remembers that the motor and sensory fibers which connect the brain and cord all pass through the medulla, it is easy to understand that injury here produces far- reaching results.
The pons varolii is associated with the medulla in its cranial nerve connections; most of its fibers are conducting paths between the other parts which lie in the cranial cavity.
FIG. 202. — THE AREAS AND CE.NTERS OF THE MESIAL ASPECT OF THE HUMAN HEMICEREBRUM.— (C. K. Milk.}
The cranial nerves connect parts of the head and face, also certain muscles of the neck, with the brain. Through the vagus (or pneumogastric) nerve — the heart, lungs and digestive organs possess cranial connections.
The vagus nerve and action of the heart.— The nerve muscle action of the heart is peculiar to itself both in structure and function. The fibers of its tissue, or myocardium, are without sarcolemma and entirely involuntary in action. Again, although involuntary, they are striped] they are also short, broad and branched to form a inuscle network — just such a structure as will insure vigorous action within a limited range of motion. This action is probably to a large degree independent, since
THE VAGUS NERVE AND RESPIRATION 315
the heart possesses ganglionic centers in its own substance from which it is supplied directly with nerve force. This rhythmic and apparently independent action is regulated by the inhibiting or restraining influence of the vagus nerve upon the cardiac nerves. When from any cause the heart is over-stimulated the vagus fibers of the cardiac plexus slow it down, thus guarding it from the exhaustion which follows overwork. The vagus also inhibits over-action of the vaso-constrictors preventing excessively high blood pressure. Therefore, it is an important agent for preserving the balance of force to be exerted between the heart and blood- vessels.
The vagus and the process of respiration. — This process is modified by the vagus nerve, probably through its influence upon the respiratory center in the brain. The digestive organs (from pharynx down) contain vagus fibers; their function is not perfectly understood, they are probably sensory.
CHAPTER XXII
THE SYMPATHETIC DIVISION OF THE NERVE SYSTEM
We have thus far considered those nerve actions which are associated with consciousness, Although some may be performed in a purely reflex manner, all may be exercised voluntarily.
The Sympathetic Division is concerned with involuntary processes only. Nerve stimulus between the central nerve system and internal organs, and to all involuntary muscle fibers, is con- veyed through sympathetic nerves.
The nerve tissues of this division are mostly gray, a large majority of the fibers being non-medullated, that is, they have no white sheath. This division of the nerve system consists of many ganglia connected together with nerve trunks, and of nerves which connect the ganglia with various organs.
About twenty- two pairs of sym- pathetic ganglia are arranged in two chains situated at the sides of the vertebrae, and connected below in front of the coccyx. These are the FIG. 203.— TERMINATIONS OF vertebral or central ganglia (Fig. 204). NERVE-FIBRES IN THE GLAND- The pre-vertebral ganglia are situ-
A. Cells of the parotid gland of ated in tne cavities of the body—
a rabbit. B Cells of the mam- thoracic, abdominal and pelvic; these mary gland of a cat in gestation.
—(Doyon and Morat.} are intimately connected with the
viscera.
The vertebral ganglia are named according to their location. They are cervical, thoracic, lumbar, sacral and coccygeal. They all receive communicating branches from spinal nerves, and send gray fibers to join spinal nerves and enter the spinal cord. (Gray and white communicating branches or rami communicantes .)
The branches or nerves belonging to these various ganglia in- terlace in close networks, forming plexuses which follow the course of arteries, supplying their walls and the viscera to which they run. They also supply the cells of glands.
316
SYMPATHETIC GANGLIA
317
CERVICAL PLEXUS
Spinal accessory nerve
J SUPERIOR CERVICAL < GANGLION OF 8YM- I PATHETIO
MIDDLE CERVI- CAL GANGLION
.. INFERIOR CERVI- CAL GANGLION
LUMBAR GANGLIA
FIG. 204. — LEFT SYMPATHETIC GANGLIA SHOWING COMMUNICATIONS WITH SPINAL
NERVES.— (Testut.)
318 ANATOMY AND PHYSIOLOGY
Special branches from cervical ganglia accompany arteries to the head, larynx, pharynx, thyroid body, and heart.
Special branches from thoracic ganglia accompany arteries to lungs and esophagus in the thorax; stomach, liver, spleen, and other viscera in the abdomen. (The branches passing through the diaphragm to the solar plexus and abdominal viscera are called splanchnic nerves — three on each side.)
Special branches from lumbar ganglia accompany arteries to kidneys and pelvic organs.
Special branches (or nerves) from the sacral ganglia accompany arteries to the pelvic organs.
The most important plexuses are the cardiac and the pulmon- ary in the thorax, the celiac (solar) in the abdomen, and the hypo- gastric in the pelvis (Fig. 205).
The cardiac plexus lies underneath and behind the arch of the aorta. Its branches supply the heart and lungs, following the coronary and pulmonary arteries.
The celiac (or solar) plexus is in the abdomen, in front of the aorta, at the beginning of the celiac artery. It contains two large ganglia — the right and left celiac (semilunar) ganglia. This plexus controls the vessels and the muscular coats of the abdominal viscera; it has been called the abdominal brain. Thus it may be understood how a severe blow over the plexus would produce a very widespread and serious result.
The hypo-gastric plexus is in front of the fifth lumbar vertebra and divides to form the right and left pelvic plexuses, which are distributed to all of the pelvic viscera (along with branches from the sacral ganglia and lumbar-spinal nerves).
Notes. — Cardiac nerves from the cervical ganglia descend to the thorax, entering the cardiac plexuses and supplying the heart and lungs. Certain branches from the thoracic ganglia form splanchnic nerves which descend to the abdomen, entering the celiac plexus and celiac ganglia, and supplying digestive organs. Certain nerves from the lumbar ganglia descend to the hypo-gastric plexus to enter the pelvic plexuses, supplying pelvic organs.
FUNCTIONS OR PHYSIOLOGY OF THE SYMPATHETIC
NERVES
The work of organs supplied with sympathetic nerves is per- formed involuntarily and unconsciously save in its results. Vis-
SYMPATHETIC PLEXUSES
319
Gtroical nerve
* Otic ganglion
-/ Connections with Vagus £ Glotso-pJiajyngeal to form f/iaryngeal plexus.
Submafillary ganglion.
, Connections with Vaou.s and
Recurrent laryngeal nerves.
"> Xeft Pulmonary plexui
CARDIAC PLEXUS
Middle \ Cardiac nerves f Inferior
*v Abdominal Aortic plexu»
mpocAsmic PLEWS
Coccygeal neroe
Ganglion Coccygeum impar
FIG. 205.— PRINCIPAL GANGLIA AND PLEXUSES OF THE SYMPATHETIC SYSTEM.—
(Morris.)
320 ANATOMY AND PHYSIOLOGY
ceral muscles, secreting cells, vessel walls, are all under the immediate domain of the sympathetic ganglia and nerves, whose motor and sensory fibers are parts of the great nerve system of the body, through communicating branches.
Certain facts indicate a communication between the brain and sympathetic nerves, for instance, the thought of food causes a flow of saliva; think of a lemon — salivary cells are stimulated. Fright or anxiety may inhibit or prevent the secretion of saliva; or inter- fere with digestion through a similar effect upon other digestive fluids; and it is well known that the secretion of milk is greatly modified by mental or emotional influences.
So with general mso-motor action. We all know the blanched face of fright or mental shock; the flush of joyous excitement; or the blush of embarrassment. All of these are sympathetic reflexes of psychic origin. In the case of secretion of digestive fluids, the psychic flow follows the thought of food at once; after that comes the secretion caused by the presence and contact of food in the different parts of the alimentary tract.
Again the effect of vaso-motor action may be seen when intense cold is applied to the skin. The cutaneous vessels contract, the blood is driven out, the skin becomes white. The opposite condi- tion is caused by heat — the vessels dilate, the blood flows in and the skin is red.
By alternate action of the two kinds of vaso-motor nerves (vaso-dilators and vaso-constrictors) , the blood supply is adapted to special and varying needs of different parts of the body, and the balance of pressure preserved in their vessels.
When an organ has work to perform its vessels dilate and the necessary blood is supplied. When the work is finished the vessels return to their usual size (their vessel tone being restored by vaso- constrictors).
The process of digestion, for example, requires that there should be much blood in many organs; the same is true of general muscular exercise. Consequently, to exercise violently after a full meal is a mistake, because the muscles would deprive the digestive organs of the extra blood which they need, and an attack of indigestion might follow; at best, digestion would be delayed. It would be better to delay the exercise.
Many examples might be given and will probably occur to the
FUNCTIONS OF NERVOUS SYSTEM 321
mind of the student, of the interactions of different parts of the sympathetic system.
These are the processes which must go on more or less continu- ously. Some may be suspended temporarily, as gland secretions, or digestion, or the formation of excretions, but they never entirely cease without causing the death of the individual.
SUMMARY
The sympathetic nerves supply all involuntary muscles, the coats of blood-vessels and the cells of secreting glands. They are the nerves of unconscious life, as the cerebro-spinal nerves are the nerves of voluntary and conscious life.
SUMMARY OF THE FUNCTIONS OF THE NERVE SYS- TEM AS A WHOLE
We have now concluded the study (briefly) of the entire nerve system, and we have seen how intimately its various parts are con- nected. Only through a knowledge of these connections can the functions of the system be understood.
It must be remembered that all parts of the head and body have at least two central representations.
Sensory nerves (representing visceral muscle, certain mucous membranes, etc., and sense organs), enter the cord and proceed as far as the posterior horns, whence another cell body and its axon receive and carry the impulse to the cortex of the brain.
Motor cortical cells of the brain prolong their axons (nerve fibers) only as far as the cord (the medulla oblongata is the upper portion of the cord). There they meet certain other cells in the anterior horns, where their message is taken to be carried by these second axons to skeletal muscles.
Different parts of the spinal cord are associated one with another by conduction fibers, and the cord is connected with the brain above by many more, running upward or downward through the medulla and pons. (On the inferior surface of the brain we see these fibers as crura or peduncles of the cerebrum and cere- bellum; they are finally connected with the gray cells of the cortex.)
21
322 ANATOMY AND PHYSIOLOGY
In the spinal cord and Us nerves we find the apparatus for reflex action which appears in so many phases — as muscle contraction, muscle tone, vessel tone, etc. The spinal cord, then, is a great reflex center, a conducting pathway, and an organ of coordination of skeletal muscles.
Included in the medulla are centers for still more important re/Zexes: the respiratory center; the cardiovascular center or center for heart-action and vessel tone combined; the heat regulating center; deglutition center, and others. Certain functions which these centers control may be modified by the will; for example, the respiratory act — we may take a long full breath or a short and shallow one; breathe rapidly or slowly, at will. Deglutition is still nearer to the realm of voluntary movements — only when food reaches the esophagus, is the act of deglutition purely reflex. (Here is the first appearance of unstriped muscle in the digestive tract.)
Going higher we find the cerebellum presiding over the coordi- nation of conscious and voluntary movements, through its connec- tion with the cortex of the cerebrum on one hand, and the pons, medulla and cord on the other. Also upon the cerebellum depends the maintenance of body equilibrium. For this it is necessary that the semicircular canals of the internal ear should be normal and in perfect connection with the cerebellum. Other sensory connec- tions also contribute to the exercise of this function; for example, to walk unaided without vision is possible, but not in a straight line; or, to walk with feet benumbed is difficult, more so to stand motionless; showing that the cerebellum is stimulated to the coordination by which equilibrium is maintained, by more than one sort of stimulus, probably by many.
We balance the body in equilibrium without conscious sensa- tion unless we voluntarily direct our attention to the subject. It is the disturbance of equilibrium which we feel.
Going still higher, we find in the cerebrum the perfecting of the plan for bringing the whole sentient and moving organism into the domain of consciousness and the will. This is by means of the connections of the cerebrum through the pons, medulla, and cord and their nerves, with every part of the body from which afferent impulses come, and to which efferent impulses may be transmitted.
The importance of these connecting fibers cannot be over- estimated; without them the body would be a disjointed affair.
NERVES OF SKELETAL MUSCLES C.S.C.
323
-$.
FIG. 206. — DIAGRAM SHOWING THE RELATION OF SKELETAL, MUSCLE AND NERVE
TISSUES — (G. Bachman.)
f.a. Bones of the forearm representing the skeletal tissue; e.j. the elbow joint, the fulcrum of the lever formed by the bones of the forearm; W. a weight acting in a downward direction and representing the passive force of gravity; sk.m. a skeletal muscle acting in an upward direction and the source of the active power to be applied to the lever; sp.c. transection of the spinal cord showing the relation of the white and the gray matter; m.c. a motor cell in the anterior horn of the gray matter; ef.n. an efferent nerve-fiber connecting the motor cell from which it arises with the skeletal muscle and contained in the ventral roots of the spinal nerves; af.n. an afferent nerve-fiber arising from the ganglion cell along its course and connecting the skin, s., on the one hand with the spinal cord on the other hand and contained in the dorsal roots of the nerves; c.s.c. coronal section of the cerebrum
324 ANATOMY AND PHYSIOLOGY
Concerning the reception and originating of ideas, the exercise of thinking — in other words, intellectual processes — we know only that these activities certainly depend for their normal manifestation upon a normal cerebrum. A well-developed cere- brum has good convolutions and deep furrows, and white fibers in good connection with its several parts. These indicate mental power, being of more importance than the mere size of the brain. The brain of the infant possesses all of the interior parts, as ganglia, etc., but the cortex is almost smooth. The cortical cells are immature and many axons have not become sheathed. With the growth of the child and quickening of the mind, the convolu- tions and furrows appear and develop; the cortical cells mature and the white fibers become sheathed. (The brain fiber does not conduct impulses before its sheath is complete.)
The number of association fibers (Fig. 201) is an index of the mental power of a brain. Large association areas signify a large expanse of cortex with power to register, remember and compare a multitude of sensations from various sources — and the ability to reason about them and form opinions concerning them.
The sympathetic division of the nerve system is the medium of communication (through communicating branches) of nerve impulses between the cerebro-spinal system and the organs con- cerned in involuntary processes, notably those connected with nutrition and growth, through control of secreting cells and vessel tone.
showing the relation of the gray to the white matter; v.c. a volitional or motor cell; d.a. a descending axon or nerve-fiber connecting the volitional cell from which it arises with the motor cell in the spinal cord; s.c. a sensor cell; a.a. an ascending axon or nerve-fiber connecting a receptive cell from which it arises (not shown in the dia- gram) with the sensor cell in the gray matter of the cerebrum. The nerve-fibers which pass outward from the spinal cord to the glands, blood-vessels, and the muscle walls of the viscera, have for the sake of simplicity been omitted from the diagram.
CHAPTER XXIII
THE SPECIAL SENSES
GENERAL SENSATION
In studying the structure and functions of the nerve system, we learn that sensory stimuli are received in every part of the body by afferent nerves, and conducted to sensory cells in the spinal cord ; there they either evoke a muscle response of reflex character, or are transmitted by connecting tracts to the brain, where the result is conscious sensation of some sort: as, for example, of tem- perature— whether of the surrounding air, or of bodies which we touch; or of other conditions — whether an object is hard or soft, wet or dry, rough or smooth, etc., etc. These are common and definite sensations of external things and by these external sensa- tions we gain knowledge of the world about us.1
Others there are which are definable in general terms only, and are not definitely located, although plainly felt. For in- stance, we are hungry, or thirsty, or tired; after pain we have a sense of relief, etc., the route for stimulus and response in these matters is through visceral and vaso-motor nerves and their spinal and cerebral connections, and by these internal sensations we gain acquaintance with our individual selves. For example, hunger is the recognition of a lack of food in the tissues; thirst, of a lack of fluid. Fatigue is the sensation caused by over- loading the tissues with waste products of metabolism (fatigue poisons).
Other mechanisms in the body are adapted to a more definite class of sensations, by which we learn to know still more exten- sively, the world in which we live; these are called the organs of the special senses.
1 We do not now refer to cranial nerves in which the arrangement is similar but more intricate.
325
326 ANATOMY AND PHYSIOLOGY
SPECIAL SENSATION
The special senses are: smell, touch, taste, hearing and sight. The organs concerned are the nose, the skin, the tongue, the ear and the eye.
It is understood that all consciousness of sensation is based upon the final reception of sensory impressions by the brain. So far as a " sense " may be said to reside anywhere, it resides in the brain, for without it there are no senses as we know them.
THE SENSE OF SMELL
The nose is the organ of the sense of smell. In the nasal chambers is a layer of special cells — olfactory cells — supported by a basement membrane, forming the Schneiderian membrane (or pituitary membrane). The upper part only of the nose is the olfactory region. Here the sensory nerves arise which proceed through the foramina in the cribriform plate or the roof of the nose, to the brain.
In quiet respiration most of the air passes in and out through the lower parts of the nasal chambers, diffusing gradually into the upper parts. Although most odors are readily perceived as soon as one comes into the atmosphere containing them, a slight odor is better appreciated by means of an effort to draw the air through the olfactory region, in other words, a sniff. More of the odorous particles are thus brought into contact with the olfactory cells, and the impressions made upon them are transmitted by the delicate olfactory nerves through the cribriform plate to the olfactory bulbs and thence by the olfactory tracts to the olfactory center in the temporal lobe of the brain.
The sense of smell is valued for the pleasurable sensations which it affords, as an adjunct to the sense of taste, and as a sentinel to warn us of danger when in the vicinity of irritating or poisonous gases, etc.
Clinical notes. — It may become greatly impaired in catarrhal affections of the nasal mucous membrane, and is sometimes lost temporarily or per- manently after an attack of influenza, congestion and consequent dryness of the olfactory membrane (as in coryza or "cold in the head") always diminish the acuteness of smell. The degree of development of this sense in lower animals is remarkable; they readily "scent danger."
MUSCLE SENSE
327
f«0pffi!BIHHi
- —
THE SENSE OF TOUCH
The skin and the mucous membrane of the mouth constitute the organ of the special sense of touch (all mucous membranes are sensitive to temperature and pain, but only that of the mouth is sensitive to touch).
The special nerve endings are situated in the deeper layers, in- cluding the hair follicles, and the papillae. Upon their number and nearness to the surface depends the acuteness of this sense. An area covered by thick layers of epidermis is not so sensitive as one where it is thin; and vice versa.
There are several forms of nerve end- ings: tactile cells, for common sensations, found throughout the skin in the deeper layers, hair follicles, and papillae; touch cor- puscles, also in the papillae and especially numerous in the palm and finger tips, where sensation is particularly acute; other forms in muscles and tendons; others still, for the perception of heat and cold or temperature sense, etc., etc. These all belong to the
sensory nerves of the cerebro-spinal nerve
^^ system.
The sense of touch includes many va- &
rieties of impressions by means of which FIG. 207.— TOUCH-COR- . , P ,. . PUSCLE OF MEISSNER AND
we may judge of surroundings, and gain WAGNER.
the necessary knowledge concerning the b. Papilla of cutis. d. external world whereby we can adjust our- N-ve-fiber *»£?£ selves to its conditions. Several of these touch-corpuscles, g. Cells
,,,.., of Malpighian layer. —
are included in the term muscle sensa- (From Stirling.} tions"; they constitute the muscle sense.
By this we become aware of many things, as the direction of movements of our own bodies, whether active or passive; of the postures of the body or its parts; (this knowledge we apply to the maintenance of balance). Also, by muscle sense we estimate the degree of force felt by the impact of a moving body, or of a blow received or given (this last is closely related to the apprecia-
328 ANATOMY AND PHYSIOLOGY
tion of weight). The faculty of stereognosis depends upon the exercise of muscle sense (it is the recognition of articles by hand- ling them, thus awakening memories of objects previously known) . Simple contact evokes no sensation without a certain degree of pressure; touch and pressure are therefore closely related; with increased pressure comes the impression of weight. If pressure is sufficiently increased, pain will be felt, which is due to the disturbance of nerves more deeply situated.
Again, a touch imparts also a sensation of place, the place where it occurs; therefore the sense of touch includes the place sense.
THE SENSE OF TASTE
F \ G 2 0 8 _ The tongue is spoken of as the organ of taste, TASTE-BUD FROM since it bears the taste buds. The sense of taste
ClRCUMVALLATE , .,...,
PAPILLA OF A CHILD. may De regarded as a specialization of the sense The oval struc- of touch and the two mechanisms somewhat
ture is limited to the rpcPrnhlA
epithelium (e) lining reS6I]
the furrow, en- The nerve endings (belonging to the 5th
upon the adjacent an<^ 9tn cranial nerves) which are developed
connective tissue for this purpose are scattered over the surface
(f); o, taste-pore
through which the of the tongue, and in (certain of) the papillae,
- also in the Palate and palatine arches (possibly
cous surface.— sometimes in the pharynx). They are found in
(A ]lcY ilPY^OL )
small oval bodies called taste buds, which are in direct connection with the gustatory nerves.
In order to excite the nerves of taste, substances must be either already in solution or soluble by the saliva; a perfectly dry sub- stance may be felt by the tongue, and its temperature, etc., will be appreciated, but it cannot be tasted. Although all flavors may be recognized in all parts of the tongue, some are more keenly appreciated in one portion than another; for example: the bitter flavors are more plainly tasted in the posterior region, while per- ception of sweets is more marked in the anterior parts. The borders seem to apprehend acids more quickly than the dorsum.
Touch, temperature, and smell are all associated with taste. If a substance is too hot the sense of taste is overcome by the
THE EXTERNAL EAR 329
sense of pain. Many people who have been deprived of the sense of smell (by disease or injury) assert that they no longer possess the sense of taste, or that, if present, it is greatly impaired.
THE SENSE OF HEARING
The organ of the sense of hearing is the ear. It has three divisions: external, middle, and internal (Fig. 210).
The external ear is that part which is on the outside of the skull, it includes the auricle and the auditory tube. The expanded portion, mostly of cartilage covered with skin, is the auricle; the
Fossa-iirli -SMi- Fossa
Lobule
FIG. 209. — THE EXTERNAL EAR.— (Morris.)
deepest depression is the concha, and the opening at the bottom of the concha leads to the external auditory canal (or meatus).
This auditory canal is one and one-quarter inches in length, formed partly by the cartilage of the auricle and partly by the temporal bone. It curves slightly upward, and then downward and forward. It is lined with skin which bears stiff hairs in the outer portion, and contains the glands which secrete "ear wax" (ceruminous glands). It is important to remember the length and direction of this canal.
The membrane at the end of the canal is called the membrana tympani, or membrane of the drum. It is a fibrous membrane
330
ANATOMY AND PHYSIOLOGY
covered with very sensitive skin on the outer surface, and mucous membrane within (Fig. 210).
The middle ear is the tympanum, or drum. It consists of a small cavity in the petrous bone, on the inner side of the membrane of the drum. Its height is barely half an inch, and the other measurements are smaller still. It contains the little bones and forms the beginning of the auditory tube.
The auditory (or Eustachian) tube begins in the wall of the middle ear and ends as a roll of cartilage opening into the pharynx.
The tympanum is really an air chamber, since it communicates
S emicircular canals
Drum membrane
Cochlea Cavity of tym- panum or drum
\
Parotid gland
Styloid process
Internal carotid artery
Auditory tube
FlG. 210.-
-THE EAR.— (Morris.)
with the throat by the auditory (or Eustachian) tube, and both tube and tympanum are lined with a continuation of the same mucous membrane. An opening at the back of the tympanum leads into the mastoid antrum, and through this, inflammation of the middle ear frequently extends to the mastoid cavities.
Note.— The mucous membrane of the pharynx is continued through the auditory tube into the tympanum, and through that into the mastoid cells. Swelling of this membrane may occlude
THE INTERNAL EAR
331
the tube and thus prevent its normal function, which is the trans- mission of air to and from the tympanum and the equalization of air-pressure on the two surfaces of the tympanic membrane, (the external surface at the end of the auditory canal and the internal surface within the tympanum).
Clinical. — Certain muscle fibers of the pharynx are so arranged that in the act of swallowing the auditory canal is opened. This fact is taken advantage of in passing the Eustachian catheter into the tube.
Two openings lead from the tympanum to the internal ear— the oval or vestibular window and the round or cochlear window.
The round window is closed by a membrane called the secondary membrane of the tympanum. The oval window is closed by a fibrous layer and the base of the stirrup bone (p. 333).
FIG. 211. — BONY COCHLEA.
i. Ampulla of superior semi- circular canal. 2. Horizontal canal. 3. _ Junction of superior and posterior semicircular canals. 4. The posterior semicircular canal. 5. Foramen rotundum. 6. Foramen ovale. 7. Cochlea. —(Brubaker.}
FIG 212. — i. Utricle. 2. Succule. 3. Vestibular end of cochlea. 4. Canalis reuniens. 5. Membranous cochlea. 6. Membranous semicircular canals. — (Brubaker.}
The internal ear is a cavity more deeply situated in the petrous bone. It is extremely complicated, consisting of semi- circular canals, vestibule, and cochlea, and well named the labyrinth. There are three semicircular canals placed at right angles to each other; the cochlea resembles a snail- shell in form, and the vestibule is between them.
The cochlea and the vestibule both communicate with the tympanum, the cochlea by the round or cochlear window; the vesti- bule by the oval or vestibular window.
The illustration (Fig. 211) shows the shape of the osseous labyrinth cut from the petrous bone. Observe the three semi-
332 ANATOMY AND PHYSIOLOGY
circular canals each with bulb-like extremity, or ampulla, opening into the vestibule. (Two are joined together at one extremity, leaving five openings for the three canals.)
Observe the two windows, round and oval in the vestibule wall, open in the dried bone, as in the illustration, but closed in life by the lining membrane of the internal ear.
The cochlea is a spiral canal winding two and one- half turns about a central stem of petrous bone (the modiolus). It is divided into three canals or scala, reaching from base to apex of the spiral. In one of these the membranous cochlea lies; of the two others, one opens into the vestibule and the other ends at the round window, separated from the tympanum by the secondary membrane.
The internal ear has a fibro-serous lining which contains a clear watery fluid called perilymph.
Lying in the perilymph and bathed by it is the membranous labyrinth having all parts and shapes of the osseous labyrinth.
Fig. 212 shows the membranous labyrinth which lies within the bony labyrinth, surrounded by perilymph. It contains a fluid called endolymph which bathes the fine nerve-fibers of the auditory nerves.
Note the membranous semicircular canals, with their ampullae , membraneous cochlea and the two portions of the membranous vesti- bule. Within these (called the saccule and utricle), the ampullae, and the cochlea, the terminal fibers of the auditory nerve are distributed.
Ossicles. — A chain of three ossicles (or little bones) is sus- pended across the tympanum — the malleus, incus, and stapes. The malleus (ox hammer) is attached by the handle to the membrane of the drum, the incus (or anvil) comes next, and then the stapes (or stirrup) with its base fitting the oval window of the middle ear. Any vibration of the membrane of the tympanum is at once trans- mitted by this chain of bones across the tympanum, to the oval window.
The base of the stapes occupies the oval window (fenestra ovalis); its movements are transmitted to the perilymph and through this to the membranous labyrinth, thence to the endolymph within it and the auditory nerves.
AUDITORY NERVES 333
Nerves of the internal ear. — There are two distinct mech- anisms in the internal ear; one for the sense of hearing, the other to serve as an organ of equilibration. So there are two separate nerves, included under the one name — auditory. Both are auditory in the sense of being connected with the ear; both are purely sensory and both are called into action by the stimulus of mechanical vibration, but here the likeness ends. They differ in their terminals and their central connections. We shall speak of them as the cochlear nerve and the vestibular nerve.
The cochlear nerve is the true nerve of hearing. Its terminal fibers are found in highly specialized epithelial cells in the mem- branous cochlea (and one ampulla) ; there they receive impres- sions transmitted by the vibrating chain of bones.
By these fibers the cochlear nerve
is formed. It passes through the llICutf^«Mr UMALLEUS
internal auditory canal into the cranial cavity and disappears in the medulla. Its fibers end in nuclei situated in the medulla, from which STAPES the impressions brought by them are conveyed finally to the auditory area in the temporal lobe (superior FIG. 213.— BONES OF THE EAR.— temporal convolution).
The terminal fibers of the vestibular nerve are found in the special cells within the membranous vestibule and ampulla of the semicircular canals. From thence they are gathered to form the nerve; it leaves the petrous bone in company with the cochlear nerve and enters the medulla. The cortical centers for this nerve are in the cerebellum. It is not concerned in hearing but is neces- sary to the power of preserving equilibrium in standing, walking, etc. The person in whom this nerve has been destroyed cannot walk steadily and is not subject to seasickness.
The vestibular nerve filaments are thought to be stimulated when vibrations of the endolymph are caused by changes in the position of the head. This seems to be established clinically. Through wide association with other nerves, changes in the position of the body also affect this nerve. The vestibular nerve fibers end in nuclei situated in the medulla, from which impressions brought by them are conveyed to the centers in the cerebellum.
334 ANATOMY AND PHYSIOLOGY
SUMMARY
The function of the external ear is to gather and direct the sound waves to the membrane of the tympanum. (The ceruminous glands and hairs of the auditory canal protect the membrane from foreign bodies floating in air currents.)
The function of the middle ear or tympanum is to transmit the vibrations thus caused, by the chain of bones to the oval window.
The function of the internal ear is to receive and transmit these impressions to the brain (the perilymph and endolymph modify the force of the vibrations as well as transmit them) . If they are received by the cochlear nerve, they are conducted to the auditory area in the temporal lobe of the cerebrum. If by the vestibular nerve, they are conducted to the cerebellum.
Associated nerves and functions. — Many coordinated move- ments are associated with the sense of hearing.
Listening causes a local increase of tension in the muscles which affect the position of the eyes and head; very intent listening is accompanied by a steadying or stiffening of the skeletal muscle system, and also an instinctive slowing or stopping of respiration. A sudden noise at one side causes an involuntary turning of the head toward the location of the sound.
The associations of the vestibular nerves are very wide. They include not only the nerves of muscles which move the face and head, but the pneumogastric or vagus, and centers in the anterior and lateral tracts of the cord in its whole length, whereby the muscle-sense nerves of the body are all referred to the cerebellum. In this manner, many different muscle groups are associated and coordinated in harmonious body movements which we are under constant necessity to perform in the common activities of life.
CHAPTER XXIV
THE SENSE OF SIGHT. THE VOICE
The eye is the organ of sight. It is situated in the orbital fossa resting in a collection of adipose tissue from which it is separated by the capsule of Tenon. This is a thin fascia surround- ing the greater part of the eyeball, and making a " flexible pocket" or lymph space in which the ball can be freely moved. The eye is a sphere or globe having at its surface three layers called the coats .or tunics of the eye — namely the solera and cornea (fibrous) , forming the outer coat, the choroid and iris (vascular), forming the middle coat, and the retina (nervous) — the inner coat. They
Retina
Choroid
Sclera —
Cornea
Iris
Ciliary processes
Lymph canal Ciliary muscle
FIG. 214.— A SECTION OF THE EYE.— (H olden.)
i, Anterior chamber; 2, posterior chamber. The aqueous humor occupies the two
chambers.
contain three transparent structures — the aqueous humor, crystal- line lens and vitreous body.
The sclera is the "white of the eye." It is dense and tough, protecting the more delicate structures within. One-sixth of the surface of the ball in front is occupied by the cornea instead of the sclera, and this also is dense and tough, but transparent for the admission of light. It contains no blood-vessels, but many tiny lymph-spaces. It is the most prominent part of the eyeball,
335
336 ANATOMY AND PHYSIOLOGY
and its convexity may be seen by looking across an eye from the side. The junction of the cornea with the sclera resembles the fitting of a watch-crystal in its case.
The portion of the sclera which is visible when the eyelids are separated, and also the cornea, are both covered by a thin mem- brane called the conjunctiva; it is a modified mucous membrane, bearing blood-vessels which can be seen, especially if a little dilated.
The choroid. — The middle coat, next to tne sclerotic, is neither dense nor tough, but is made up of fine tissue fibers bearing a very delicate and close network of blood-vessels. It is the vascular coat of the eye, and lines the sclera only, not the cornea. Many pigment cells are contained in the choroid coat, giving to it a deep brown color so that it makes a dark chamber of the eye.
Sclera
FIG. 215. — THE CHOROID AND IRIS. — (H olden.}
The iris. — There is no choroid behind the cornea. Its place is supplied by the iris, which resembles in its shape a circular curtain attached by its edge to the choroid, and having a round aperture in the center called the pupil or the "star of the eye." The iris contains a network of fine vessels and pigment cells, varying in color according to the amount of pigment. (Blue eyes have least, black eyes most.) It has muscular fibers arranged in two sets — circular, or ring fibers, and so-called radiating, or straight fibers. The circular fibers surround the pupil. Thus, when they contract, as in a bright light, they diminish its size. The straight fibers run from the outer border of the iris toward the pupil, and
THE OPTIC NERVE 337
therefore when they contract they draw upon the margin to enlarge the opening. Briefly, the pupil is contracted by the circular fibers, and dilated by the straight or radiating fibers, thus the amount of light admitted within the eye is regulated.
The retina is the innermost coat, of many layers, within the choroid. This is a very delicate structure in which are the be- ginnings of the optic nerve fibers. It is the coat which is essential to vision — no retina, no vision. The outermost layer of the retina is the one which contains the rods and cones, or the visual cells. Like the sclera and choroid, the retina is incomplete in front. When first exposed to the air (in the dissection of an eye) it is clear and shining in appearance, presenting an opalescent play of color with a general violet tinge, due to the "visual purple" contained in delicate pigment cells.
From the cells in the retina delicate fibers are prolonged and gathered together to form the optic nerve, which pierces the choroid and the sclerotic, passes through the optic foramen of the orbit, and thence back to the brain. The optic disc is the spot where the optic nerve leaves the retina; it is situated a little to the nasal side of the center of the retina (Figs. 214,216). Of course the optic disc is not a portion of the retina proper, and no sense of vision is stimulated here. It is rather an area where the nerves and vessels are transmitted through the other coats of the eyeball.
The macula lutea is a spot in the center of the retina opposite the mid- point of the normal pupil. In the center of this spot is a depression called thefovea centralis which is the center of vision; only the cone-shaped visual cells are here present.
The vitreous body is glass-like, as its name signifies, both in appearance and transparency. It consists of a jelly-like substance contained in a hyaloid membrane within the three coats. It trans- mits and directs the rays of light to the retina; also it aids in pre- serving the shape of the eyeball (Fig. 214).
The crystalline lens is situated immediately in front of the vitreous body, in a shallow depression like a cup on the anterior surface. It is a double convex lens with a capsule, both perfectly transparent so that light may pass through, and it is able to converge the rays of light so that they will fall correctly upon the retina.
The lens is behind the iris, the margin of the pupil resting
22
338 ANATOMY AND PHYSIOLOGY
lightly upon it. It is held in place by delicate fibers which form a suspensory ligament; this is normally a little tense, exerting a slight but constant pressure upon the eyeball.
The ciliary muscle is in the interior of the eyeball, around the junction of the choroid and iris, thus lying a little farther forward than the border of the lens. By its action it draws the suspensory ligament forward, releasing the lens from pressure; thus it modifies the shape of the lens; by this arrange- ment the eye is able to accommodate itself to the different distances of sur- rounding objects. This is the process of accommodation. To "paralyze the accommodation" is to make the ciliary muscle powerless, so that the eye cannot try to see near objects, as it always does unconsciously, in its normal condition. Atropin will do this.
Clinical notes. — Inflammation of the iris, or iritis, may cause adhesions to
Macula ^ "W^^SS Retinal vessel s
FIG. 216. — THE RETINA AS SEEN WITH THE AID OF THE OPHTHALMOSCOPE. — (Morris.}
the lens unless the margin of the pupil be drawn away. This is the reason for the use of atropin, which weakens the circular fibers while it stimulates the straight ones, or, in other words, dilates the pupil.
Cataract is a thickening of the lens which makes it opaque and gives it a milky appearance. The remedy is excision or removal of the lens, after which a convex lens of glass in front of the eye gives a good degree of vision. A cataract is in an eye, not over it, and must be taken out, not off.
Aqueous humor and chambers of the eye. — The space be- tween the cornea and the lens is partially divided by the iris into two portions — the anterior and posterior chambers of the eye. They contain a thin clear fluid, called the aqueous humor, which floats the iris and aids in preserving the shape of the cornea (Fig. 214).
Note. — The rays of light which fall upon the retina must first pass through the media (or structures which direct their course) in the following order: the cornea, aqueous humor, crystalline lens, and
MYOPIA, HYPEROPIA 339
vitreous body. Should any one of these media lose its transparency, vision would be impaired or perhaps lost.
The correct retinal image is the object for which these struc- tures are designed. In order that this may be formed, the rays of light which are reflected from a wide area of surrounding objects must be made to converge and meet on the retina, from which the stimulus thus received is conveyed to the brain by the optic nerve. Rays of reflected light go toward the eye from every direction and by concentrating those which enter the pupil upon the retina, a small inverted image is formed which is recognized by the brain as representing the objects so pictured in their proper size and position.
This concentration of rays of light is accomplished by the refractive (or bending) media of the eye: the cornea, aqueous humor,
FIG. 217. — MYOPIA. FIG. 218 — CORRECTION or MYOPIA BY
Parallel rays focus at F, cross and A CONCAVE LENS. — (Brubaker.)
form diffusion-circles; divergent rays from A focus on the retina. — (Bru- baker.)
crystalline lens and vitreous body, in order. Each medium refracts (or bends) the rays more and more toward a common center or focus. The denser the media or the more convex the surface, through which the light rays pass, the greater the change in their direction (the shorter the focus).
In the normal or emmetropic eye the focus is at the retina and a clear image is formed. In the myopic or "near-sighted" eye it falls in front of the retina, either because some surface (cornea or lens or both) is too convex or the eye is too long, and the rays of light from all except near objects, converge in front of the retina. The remedy is a concave lens of glass to counterbalance the excessive convexity or length. (See Figs. 217 and 218.)
In the hyperopic or "far-sighted" eye, the focus would fall behind the retina; the surface of the cornea or lens is not convex enough or else the eye is too short. The rays of light are not sufficiently bent to meet upon the retina and the remedy is a
34O ANATOMY AND PHYSIOLOGY
convex lens of glass to provide for the lack of convexity. (See Figs. 219 and 220.)
In the condition known as astigmatism, the surfaces are ir- regularly curved and they form a distorted image; the attempt to correct this requires a constant effort which is very injurious to the eye. The remedy is a lens of glass with counter-balancing irregularities.
Emmetropia is the condition of the normal eye.
Myopia is near-sightedness.
Hyperopia is far-sightedness. (This is congenital.)
Astigmatism may be described as crooked-sigh tedness.
Presbyopia is the far-sightedness of age (an acquired condition), the tissues of the eyeball having lost their flexibility and resilience.
The perception of color, or color vision, has not been quite
FIG. 219. — HYPERMETROPIA. PAR- FIG. 220. — CORRECTION OF HYPER-
ALLEL RAYS FOCUSED BEHIND THE METROPIA BY A CONVEX LENS. —
RETINA. — (Brubaker.) (Brubaker.)
clearly explained; consequently, we cannot state definitely the cause of defective color vision, or color blindness. This is not blindness to all colors, but usually to red or green.
It is supposed that certain different chemic substances in the retina are peculiarly sensitive to ether vibrations of different degrees of rapidity, whereby impulses of a corresponding nature awaken in the brain the sensa- tion of the various colors. In color blindness it is not difficult to imagine that some of these sensitive chemic substances may be absent, thereby making it impossible for the eye to perceive the corresponding color stimulus.
Range of accommodation. — By this is meant the distance from the nearest to the farthest point at which an object can be seen clearly. One can experiment for one's self with any small object, as for example, with a pencil. By holding it very near to the eye and gradually moving it away, the point will be found where the image of the pencil is clear; this is the near point of accommodation (punctum proximum oj vision). Moving it still
REFRACTING MEDIA OF EYE 341
farther away, a point will be found where it can no longer be seen clearly. This is the far point (punctum remotum). The distance between these points is the measure of the range of accommodation.
RESUME.
The sclera is protective; the cornea is protective and refractive. The aqueous humor preserves the shape of the cornea and flexibility of the iris and also refracts rays of light. The iris regulates the amount of light admitted, contracting in strong light and when viewing near objects. It is relaxed and inactive in the absence of light. (An active dilatation is caused in certain conditions through stimulation of the radiating fibers.)
The crystalline lens refracts the rays of light which enter the eye.
The ciliary muscle, by drawing the suspensory ligament for ward, releases the lens from pressure, so that it becomes more convex and accommodates light-rays from near objects. (Ordinarily, the lens, prevented by the ligament from assuming its greatest convexity, is in the position to transmit light from more distant objects to the retina.)
The vitreous body preserves the shape of the globe and is also refractive.
The choroid and iris (meal tract) constitute the dark chamber of the eye.
The retina is the sensitive nerve layer.
APPENDAGES OF THE EYE
The eyebrows, resting upon the superciliary ridges, or eleva- tions caused by the frontal sinuses (p. 21), serve to extend the protection given by the orbit.
The eyelids (or palpebrae,) attached to the margin of the orbits are necessary for the protection of the eye. They have five layers, —skin, smooth and thin; fascia — thin and delicate; muscle — the palpebral portion of the orbicular muscle; fibrous — containing a stiff plate of connective tissue, the tarsal plate; and mucous — the layer which lines the lid (conjunctiva).
The conjunctiva (or conjunctival sac) is the sensitive mucous membrane which is attached to the margins of the lids to line them
342
ANATOMY AND PHYSIOLOGY
and to cover the front of the eyeball. The portion which lines the lids is the palpebral conjunctiva, that which covers the ball is the bulbar or ocular conjunctiva.
The tar sal glands are in the tarsal plates; their oily secretion
Superior lacrimal gland Inferior lacrimal gland
Ducts from superior gland
Upper eyelid partly divested of skin
Upper punctum
Lacrimal sac, near its fundus
Common duct, formed by junction of upper and lower ducts
Lower punctum
Naso-lacrimal duct
FIG. 221. — LACRIMAL APPARATUS. — (Morris.)
prevents the lids from adhering to each other. (They are called Meibomian glands.}
The angles formed by the extremities of the eyelids are the medial and the lateral angles (inner and outer canthi). At the medial angle, each lid presents a small elevation, the lacrimal
FIG. 222. — THE MUSCLES OF THE EYEBALL. — (Holden.) \ A small section of the upper eyelid is shown.
papilla, with a minute opening (punctum) where the tears enter a small canal which leads to the lacrimal sac; from the lacrimal sac they flow through the nasal duct to the nasal cavity.
The eyelashes, or cilia, are kept soft and flexible by an oily
THE LACRIMAL GLAND 343
substance secreted by their own oil glands in the margin of the lids. The cilia of the upper lid curve upward, those of the lower lid curve downward; they never interlace. They guard the eye from foreign bodies — as coal dust, etc., floating in the surrounding air.
The space between the margins of the eyelids is called the inter p alp ebral slit (palpebral fissure). It varies with the action of the lids; the opening and closing of the slit is done by the upper lid mainly, the lower one moving but very little. (Muscles — orbicularis closes, levator palpebrce opens . (See p. 89.)
Lacrimal gland. — The gland which secretes the tears. It is situated in the lacrimal fossa of the frontal bone, beneath the lateral end of the orbital arch, and has several ducts for the dis- charge of the tears under the upper eyelid. The tears flow across the eyeball and bathe the conjunctiva, washing away the dust and other fine particles of foreign substances, which would be injurious if allowed to attach themselves to the conjunctiva. They are con- ducted by tiny canals (canaliculi) into the lacrimal sac and nasa> duct (see Fig. 221) thence to the nasal fossa. Being a thin saline solution they are unirritating to mucous membranes.
Clinical note. — The conjunctiva is supplied with blood-vessels most of which are invisible except when they become congested. In active inflammation or conjunctivitis they are so enlarged as to give the membrane a bright red color.
Motions of the eyeball. — The eyeball is moved by six slender muscles, which have their origin at the apex of the orbit and their insertion upon the sclera at a little distance from the cornea. These are the orbital muscles.
The superior rectus rolls the ball upward. (Third nerve.) The inferior rectus rolls the ball downward. (Third nerve.) The internal rectus rolls the ball inward. (Third nerve.) The external rectus rolls the ball outward. (Sixth nerve.) The superior oblique rolls the ball downward and outward. (Fourth nerve.)
The inferior oblique rolls the ball upward and outward. (Third nerve.)
Clinical note. — If these muscles are well balanced the pupil is directed straight forward while they are at rest, but if they are of quite unequal strength the eye will be turned habitually in some special
344
ANATOMY AND PHYSIOLOGY
direction. This condition is called squint or strabismus, or "cross-eye." It oftenest happens with either the internal or external rectus.
The muscles of the iris and the ciliary body are the ocular muscles.
Associated movements are of interest in connection with the eye. The central connections are so arranged that the external rectus of one eye moves with the internal rectus of the other; the internal recti of the two eyes act together when they are directed toward a near object. The act of convergence is asso- ciated with contraction of the pupil and ac- commodation. It is easily understood that fixing the eye upon a near object is not a simple act : — the circular fibers of the iris, the ciliary muscle and the internal recti are all called into action. (The far-sighted eye is doing this work constantly; it is there- fore important to relieve this strain of overwork by well-fitted lenses.)
FIG. 223. — INTERIOR OF LARYNX (LEFT SIDE RE- MOVED).— (Sappey.)
2, Epiglottis; 5, so-called "false vocal cord"; 9, vocal band; 13, thyroid cartilage; 14, arytenoid cartilage.
text.
THE VOICE
The voice, by which we establish most frequent communication with the outside world, is a special endowment for the ex- pression of ideas awakened in conscious- ness by the senses. It is therefore not inappropriately considered in this con- nection.
The larynx is the organ of the voice.
(The larynx, lips, tongue and teeth are the organs of speech.) A brief description of the larynx is given on page 234, of tongue and teeth, pp. 132, 35.
The structures which are specially concerned in the production of the voice, in addition to the cartilages described, are the vocal bands (also known as vocal cords, and true weal cords). These are stretched across the larynx from front to back, being attached to the thyroid cartilage anteriorly and the two arytenoid cartilages posteriorly, thus dividing the cavity into upper and lower portions (Fig. 223).
ORGANS OF SPEECH 345
The arytenoid cartilages are shaped like a triangular pyramid with a curved apex. They rest upon the cricoid cartilage and form with it movable joints having ligaments and synovial membranes. These are gliding joints. They allow the rotation of the arytenoids upon the articular facets of the cricoid.
The vocal bands are composed of fibrous and muscle tissue covered with mucous membrane. The space between them is the glottis.
Small muscles, belonging altogether to the larynx, control the position and tension oj the weal bands by their action on the arytenoid cartilages to which the bands are attached, thus producing the different tones of the voice as the breath passes between them. Tense bands and a narrow glottis are necessary for a high note. Lax bands and a wide glottis are the conditions for a low note.
Above them are two membranous folds, one on either side, formerly called false weal cords.
Note. — It has been generally taught that the voice is caused by vibrations of the vocal bands, but accurate observations by Miss Alice Groff, of Phila- delphia, and other investigators, have proved that this is not the case, the voice-sounds being like those of a horn rather than a stringed instrument.
With the aid of lips, tongue, and teeth, the voice sounds are so modified that speech becomes possible, and with it the expression of ideas, and communication between individuals.
The various air sinuses which communicate with the nasal fossae act as resonance chambers. They give to the voice an agree- able quality of tone, which is in marked contrast to the sound produced when the air current cannot enter these chambers, as in coryza (when the mucous membrane is so swollen as to prevent free admission, to the sinuses, thus causing the nasal tone) .
CHAPTER XXV THE PELVIC ORGANS
IN THE MALE PELVIS. IN THE FEMALE PELVIS.
The rectum. The rectum.
The urinary bladder. The urinary bladder.
The prostate gland. The uterus.
The ovaries, and uterine tubes.
The vagina.
The Rectum is already described (page 146).
The Bladder is the receptacle and reservoir for the urine and is situated in the pelvis just behind the pubic bones.
It is described with the urinary organs (p. 246).
In the male pelvis the bladder is in front of the rectum and in contact with it for a short distance in the lower part. Above this point the peritoneum dips between the two organs forming the recto-vesical pouch (p. 352, Fig. 227).
The prostate gland is situated at the base of the bladder, im- mediately in front of the rectum and surrounding the first portion of the urethra.
In the female pelvis the relations of the bladder are different. The base is immediately in front of the lower portion of the uterus and upper portion of the vagina, the urethra lying close to the vaginal wall. The peritoneum which dips between the bladder and uterus forms the utero-vesical pouch.
v-X "
THE UTERUS AND APPENDAGES
These constitute the internal generative organs. The appendages are the uterine (or Fallopian) tubes and the ovaries.
THE UTERUS
The uterus, or womb, is situated between the bladder and the upper part of the rectum. It is a hollow organ shaped somewhat like a pear, about two and one-half or three inches long, and one
346
STRUCTURE OF THE UTERUS
347
and one-half inches wide at the larger end, which is called the fundus and is placed uppermost.
The uterus is composed of non-striated muscles, arranged in three layers and lined with mucous membrane bearing ciliated epithelium. Its walls are about three-eighths of an inch thick. It consists of two portions, the body and the neck or cervix, the body being a little longer of the two.
POSTERIOR SURFACE OF BODY OF UTERUS I
TTtero-ovarian ligament OVARY
FALLOPIAN TUBE
Broad ligament
Inf undlbul urn FJmbria Broad ligament
Vaginal walls
FIG. 224. — UTERUS AND APPENDAGES, POSTERIOR. — (Morris.}
The body is flattened, but is more convex at the back than in front; the cervix is round.
The cavity of the uterus corresponds to the general shape of the organ, being triangular in the body and round in the cervix. At the upper angles of the body are the openings which lead into the uterine or Fallopian tubes. Between the body and the cervix is the internal os, the opening at the lower extremity of the cervix being called the external os, which is bordered by the anterior and posterior lips. The uterus is covered with peritoneum, except in front of the cervix.
348
ANATOMY AND PHYSIOLOGY
When the uterus receives an impregnated ovum its function is exercised in protecting and nourishing the growing embryo until it becomes a fully developed fetus. The mucous membrane thickens to form a bed for the embryo, and becomes a part of the placenta or " afterbirth." The muscle fibers grow in size and
number and the weight increases from the origi- nal ounce and a half to one or more pounds.
The function of the uterus is concluded with the expulsion of the fetus and placenta. It then contracts rapidly, and the process of invo- lution softens and dis- charges the remains of tissue which is no longer
FIG. 225.— THE UTERUS. needed. (See p. 358,
Showing cavity and attachment of vagina. — 7 7 • \
Morris.} lochta.)
Position. — Thefundus of the uterus is normally inclined somewhat forward, while the os externum looks downward and backward. If the fundus turns too far forward this is anteversion; if it inclines backward, retr aversion.
A bend may exist where the neck joins the body. This is flexion. When the body is bent forward, this is anteflexion; when backward, retroflexion.
THE UTERINE TUBES (FALLOPIAN TUBES)
The uterine tubes (Fallopian tubes) two in number (Fig. 224), extend outward from the upper angles of the uterus; they have a fibre-muscular structure and are lined with mucous membrane. Each tube is about four inches long. At the beginning it is only large enough to allow the passage of a small bristle, but it becomes larger toward the end, expanding into a trumpet-shaped extremity called the infundibulum, which is fringed or fimbriated, and which is connected with the ovary below by a slender band (or fimbria).
The function of the uterine tube is to convey the ovum from the ovary to the cavity of the uterus.
THE OVARIES
The ovaries, two in number, lie on either side of the body of the uterus, each one being connected to it by a short cord called
OVULATION 349
the ovarian ligament. An ovary is about three-quarters of an inch long, a half-inch wide, and shaped like an almond (Figs. 224, 226).
The ovaries are covered with peritoneum (except at the border where vessels enter and leave).
Structure of the ovary. — A collection of connective- tissue fibers enclosing many vessels and nerves, and a multitude of little ovisacs (egg sacs) called Graafian follicles. These follicles are at first microscopic in size, but when developed they may be seen by the naked eye. Each one contains an ovum, or egg.
Ovulation. — As the follicle with its ovum grows in size it approaches the surface of the ovary, and when it is mature the sac ruptures and the ovum escapes, to be taken by the uter- ine tube to the uterus, from which it is discharged through
the vagina, usually with a quan- FIG. 226. — OVARY WITH MATURE r 11 j GRAAFIAN FOLLICLE ABOUT READY TO
:ity c RuRST.—(Ribomont-Dessaignes-Lewis.)
The function of the ovary
(ovulation) begins with puberty, which is the maturing of the pelvic organs and mammary glands. It is usually established at about fourteen years of age (earlier in warm climates, later in cold). From that time the development of at least one ovum occurs in (about) every twenty-eight days until the menopause is established.
Menstruation is the periodical discharge of blood from the uterus. The mucous membrane thickens and sheds its superficial cells, which are renewed after the flow ceases. This probably accompanies ovulation. When an impregnated ovum reaches the uterus menstruation is suspended.
The cessation of menstruation is the menopause or climacteric. It often occurs at about forty-five years of age and may be as late as fifty or over. It is followed by gradual atrophy of the generative organs.
Corpus luteum is the name given to a yellow substance which forms in the ruptured Graafian follicle. It ordinarily shrinks and disappears within a month. Immediately after the rupture the follicle fills with blood; this forms the corpus hemorrhagicum, changes to the corpus luteum and this in
350 ANATOMY AND PHYSIOLOGY
turn is succeeded by a whitish spot called the corpus albicans. If conception has taken place, the corpus albicans is not formed. The corpus luteum persists, grows larger and remains present until the end of pregnancy.
The ovary has been included in the list of ductless glands. Its internal secretion is not discovered, but there is undoubted clinical evidence that the corpus luteum contains at least one autocoid substance, .since many of the sequelae which follow the removal of the ovaries are prevented by the use of extract of corpus luteum (or lutein). By this means the system is supplied with something of which it had been deprived. (The medicinal extracts are made from the ovaries of swine.)
THE VAGINA
The Vagina is the muscular canal extending from the uterus to the surface of the body, where it terminates at the vaginal orifice (Figs. 165, 224).
It is situated between the base of the bladder in front and the lower portion of the rectum behind, from which organs it is separated by connective tissue septa (vesico-vaginal, and recto- vaginal septa). It curves slightly forward, is four inches long in its posterior wall and about two and three-quarter inches in the anterior. It has two layers of muscles, strengthened by fibrous tissue and lined by mucous membrane which lies in transverse folds. The columns of the vagina are two median ridges, one on the anterior and one on the posterior wall, extending throughout their length.
The vagina is attached to the cervix of the uterus at a little distance above the external os (about half an inch in front and three-quarters of an inch at the back); therefore the examining finger may feel the cervix projecting into the canal. This is the infra-vaginal portion of the cervix (Fig. 224, 227). The portion of the vagina which is attached to the cervix is thefornix (or roof) .
Note. — The urethra lies close to the anterior vaginal wall, feeling like a thick cord in the septum between the two canals (the urethro-vaginal septum).
LIGAMENTS OF THE UTERUS
The uterus is sustained in the pelvis by folds of peritoneum which connect it to the pelvic walls and to the bladder and rectum. The principal ones are the broad ligaments (Fig. 224).
LIGAMENTS OF THE UTERUS 351
The broad ligaments are folds of peritoneum extending laterally from the sides of the uterus, like wings, to the sides of the pelvic cavity. Each fold encloses the uterine tube, ovary, and round ligament of its own side.
The round ligaments are two muscular and fibrous cords, which extend from the angle of the uterus lateralward and for- ward through the inguinal canal, to be attached to the tissues upon the pubic bone. They aid in preserving the normal position of the uterus with the fundus forward. This position is still further secured by utero-sacral ligaments, which connect the junction of the cervix and body of the uterus with the second and third pieces of the sacrum, thus holding the cervix back. (They pass one on either side of the rectum.)
THE EXTERNAL GENERATIVE ORGANS
The pudendum muliebre (vulva) .• — The name given to the parts situated in front of the pubic arch of the female pelvis. They are:
The mons veneris, a cushion of adipose and fibrous tissue in front of the body of the pubic bone.
The labia majora. — Two folds of skin containing adipose and loose connective tissue, continuous in front with the mons, and joined together posteriorly by a fold of skin called the posterior commissure, about an inch in front of the anus. (The depression in front of this commissure is the fossa navicularis .)
The space between the labia majora is the pudendal cleft.
The labia minora. — Two folds situated between the labia majora, about one-half as long, and joined anteriorly in the hood of the clitoris. B etween them is the space called thevestibule. (They sometimes unite posteriorly in a thin fold called the frenulum.)
The clitoris. — A small body, somewhat less than an inch in length, nearly covered by the hood. It contains many vessels and nerves. The extremity is called the glans of the clitoris; the hood is normally free from the glans and if adhesions form they should be separated, since they are a source of nervous irritation.
The vestibule. — A triangular space below the clitoris, and between the labia minora. In the middle of the vestibule is the orifice of the urethra, or external meatus.
Below the vestibule is the orifice of the vagina, or vaginal orifice,
352
ANATOMY AND PHYSIOLOGY
partially closed by a circular fold of mucous membrane called the hymen.
The ragged edges left by rupture of the hymen are called carunculcR myrtiformes. An imperforate hymen is one which extends entirely across the vaginal orifice, closing it altogether. A, little way, laterally, from the middle of the hymen are the openings of the ducts of the glands of Bartholin, one on either side (or vulvo-vaginal glands). Not infrequently they become infected and swell rapidly, forming an abscess.
THE PERITONEUM OF THE PELVIS
The peritoneum of the pelvis (Fig. 227) is a portion of the general peritoneum. It lines the pelvic walls, covers the rectum (except the lowest 'part) and other pelvic organs, and the floor.
Liver
Gastro-hepatic omentum
Stomach- Transverse colon Mesentery
Small intestine
Uterus —
Bladder
Epiploic foramen Pancreas
Duodenum
Transverse meso-colon Aorta
Rectum
FIG. 227. — DIAGRAM or A SAGITTAL SECTION OF THE TRUNK, SHOWING THE RELA- TIONS OF THE PERITONEUM. (Allen Thompson.)
In the male pelvis it dips between the rectum and bladder forming the recto-vesical pouch.
In the female pelvis it forms a utero-vesical pouch in front of the
THE PERINEUM
353
uterus, and a utero-rectal pouch behind it. It also extends over the tubes, ovaries, and round ligaments at the sides, thus making the folds called the broad ligaments, which connect the uterus with the sides of the pelvic cavity.
The utero-rectal pouch is the pouch of Douglas (or Douglas's cul-de-sac). It is the lowest part of the peritoneal cavity, ex- tending down an inch or more behind the vagina.
Note. — The pelvis of the infant (see Fig. 48), is undeveloped and the pelvic organs lie partly in the abdomen. As growth advances they are fi- nally contained in the pelvis, at about the fourteenth year.
Perineum.— The name perineum properly signifies the parts bounded by the out- let of the pelvis, but we gen- erally apply it to the portion in front of the rectum.
In the female perineum, the part between the lower ends of the vagina and rectum is the perineal body. This is FlG 228._SHOWING^;TIS
a triangular body composed DEFERENS SUSPENDED BY SPERMATIC CORD.
r .... i. —(Holden.)
of connective tissue and adi- pose, the base of the triangle being covered by skin and measuring about one inch, between the vulva and the anus. It contains several muscles, some of which are connected with the sphincter ani.
The perineum is distensible, and stretches to a remarkable extent during labor.
From the male perineum a pouch of skin and fascia is suspended, called the scrotum. The fascia contains scattered muscle fibers and is called the dartos.
The scrotum contains the testes which are two in number, the right and the left. They consist essentially of minute tubes in which the seminal fluid is secreted, and which open into larger ones leading to the duct of the testis, or the ductus defer ens.
The function of the testis is the formation of spermatozoa (or s per mid) from the cells which line the tubes. 23
354 ANATOMY AND PHYSIOLOGY
The spermatozoon is the male germinal cell (often called the sperm celt). It is carried by the seminal fluid through the ductus defer ens to the urethra from which the fluid is discharged.
The ductus deferens passes upward from the testis through the subcutaneous ring and the inguinal canal, then down into the pelvis and beneath the bladder, where it runs forward to enter the urethra.
The spermatic cord. — The testis is suspended in the scrotum by the spermatic cord, which reaches from the abdominal inguinal ring to the bottom of the scrotum, and contains the cremaster muscle. Contraction of the cremaster muscle lifts the testis and draws it upward in the scrotum (Fig. 228).
Descent of the Testis. — During fetal life the testis is situated in the abdominal cavity, just below the kidney, but it slowly descends to pass through the inguinal canal, reaching the subcutaneous ring at about the eighth month, and at birth it should be in the scrotum. It may descend more slowly, or may be arrested at any point, but usually finds its place in time.
In the scrotum it is surrounded by a double sheath of the peritoneum (tunica -vaginalis) which accompanied it, and which became shut off from the great peritoneal sac as the subcutaneous ring closed around it. It is a serous sac, having visceral and parietal layers.
In caring for the male infant it is important to note the condition of the foreskin (or prepuce). This is a fold of skin which covers the glans penis. It should be sufficiently loose to be easily drawn back, or retracted, in order that careful cleansing of the parts may prevent accumulations of sebaceous mate- rial, or smegma. If this is not done, irritation is caused by retained substances and also by adhesions which are apt to form.
Circumcision is cutting off the foreskin (literally — cutting around}.
Hydrocele is a collection of serous fluid in the vaginal tunic of the testis.
Impregnation. — The entrance of the spermatozoon into the ovum causes impregnation or conception. The spermatozoon reaches the ovum after passing through the vagina and uterus into the uterine tube; it is here that conception usually occurs, in an ovum which has entered the tube on its way to the uterus. The head (or nuclear part) of the sperm cell unites with the nucleus of the ovum to form one new or "parent cell." By division of its substance this cell forms many new ones (all contained within the wall of the parent cell), each composed of the united original elements. A series of rapid changes follows and a re- arrangement
THE DECIDUA
355
of the new cells into three layers, from which the different parts of the body of a new being and the membranes which envelop it, will develop. When the impregnated ovum reaches the uterus it finds extensive preparations already made for its reception. Instead of being washed away by menstrual fluid, it is deposited in a soft bed of the thickened mucous lining of the uterus which has developed an increased growth and new features for the purpose. As this membrane will be discarded after the birth of the child, it is called a true decidua, or decidua vera (Fig. 229.)
The impregnated ovum becomes attached to the mucous membrane usually near the fundus (see Fig. 230). This area of
FIG. 229. — THICK- ENED LINING OF A PREGNANT UTERUS.
Showing decidua vera, decidua serotina and beginning of the reflexa. — (Dalton.)
FIG. 230.— THICKENED LINING OF A PREGNANT UTERUS.
Showing decidua reflexa. — (Dalton.)
fixation becomes the decidua serotina. A portion of the decidua vera rises on every side of the ovum and thus forms a third decidua, the decidua reflexa which finally encloses it. As the ovum grows and the fetus develops to fill the uterine cavity, the decidua reflexa becomes fused with the decidua vera and together they are dis- charged in the lochia. The serotina becomes a part of the placenta.
The decidua vera is the uterine decidua.
The decidua reflexa is the ovular decidua. (Together these two disappear in the lochia.)
The decidua serotina is the placental decidua.
356
ANATOMY AND PHYSIOLOGY
Right innominate vein
Superior vena cava Right pulminary artery
Inferior vena ca
Left branch of portal vein Ductus venosus
Umbilical vein Portal vein
Right branch of portal vein
Umbilical vein Umbilical arteries
Umbilical artery
Left innominate vein
Arch of aorta Ductus arteriosus Left pulmonary artery
Descending aorta
Superior esenteric artery
Splenic vein
Superior mesenteric vein
Inferior mesenteric artery
Left common iliac artery
Hypogastric artery
External iliac artery
FIG. 231. — THE HEART, WITH THE ARCH OF THE AORTA, THE PULMONARY ARTERY, THE DUCTUS ARTERIOSUS, AND THE VESSELS CONCERNED IN THE FETAL CIRCULATION.— (Morris.) (From a preparation of a fetus in the Museum of St. Bartholomew's Hospital.
THE PLACENTA 357
The fetus is enclosed in the amniotic sac which is formed by the fusion of two membranes (amnion and chorion) derived from layers of the original cell. It is often called "the membranes."
It contains amniotic fluid — a clear saline solution in which the fetus floats. The placenta is developed in the outer layer of the sac (chorion).
Clinical note. — It is sometimes possible to separate the two layers of mem- brane to a partial extent.
The placenta is a mass of uterine and fetal blood and lymph vessels, held loosely together. The vessels of the decidua serotina are branches of the uterine arteries, which form thinly covered loops called mill. These are received between similar villi of the fetal vessels, forming the placenta. The blood of these two sets of vessels is separated only by the thinnest of membranes, so that the respiration (or exchange of O and COz) of the infant is thus provided for,1 the impure blood arriving from the fetus by two arteries (right and left hypogastric) and returning purified to the fetus by one vein, the umbilical (Fig. 231).
Point of interest. — The function of these vessels is similar to that in the lungs of extra-uterine life, where the right and left pulmonary arteries carry impure blood to the lungs and pulmonary veins carry pure blood to the heart.
Note. — The placenta is not within the amniotic sac. The fetal surface is smooth, a part of the sac itself; the maternal or uterine surface is irregular, dark red and friable (easily separated into its original masses of vessels and connective tissue called cotyledons).
Pregnancy or gestation is the condition in which these proc- esses are going on. It begins with conception and ends with the expulsion of the fully developed fetus from the uterus, or parturition.
The normal duration of pregnancy is 280 days or ten lunar months. During the first five months the growth is very rapid; the length of the fetus increases from one centimeter in the first month to twenty-five in the fifth (about 10 inches). After the fifth month the growth advances steadily but not so rapidly. The average length at birth is about fifty centimeters, and the average weight 2737 grams, or 7 1/3 Ibs.
The growth of the uterus to accommodate the growing fetus
has been alluded to. The great blood supply required for all
these changes is provided by the uterine and ovarian arteries which
are normally very large in proportion to the size of the organs.
1 By processes of diffusion and osmosis as in the lungs.
358 ANATOMY AND PHYSIOLOGY
Fig. 138 illustrates the way in which they are disposed in order to provide for the increasing area to be supplied and for the growth of the fetus. Their tortuous course provides for a greatly increased distribution to constantly enlarging organs without undue stretching of the vessels.
During the first three or four months (according to different authorities) the fetus is known as the embryo.
Expulsion of the fetus during the first three months constitutes abortion; from the fourth to the sixth months, it is called mis- carriage. After six months it is possible for a strong fetus to go on developing after expulsion (although exceedingly uncommon at that date) ; therefore, from that time until term (the end of 280 days) expulsion constitutes premature delivery. The delivery of the child is usually preceded by the escape of amniotic fluid.
The quantity of amniotic fluid is about one liter. Its use is to provide against injury from sudden jars or blows during pregnancy, to allow freedom of movement on the part of the fetus, to preserve the flexibility of the skin of the fetus, and at the time of parturition to aid in the dilatation of the cervix of the uterus as it fills a pouch of the amniotic sac which is forced down by uterine contractions.
Soon after the expulsion of the child, the placenta is separated from its attachment to the uterus by the contracting walls and later is expelled, with the ruptured and emptied sac.
The placental site is now bare and bleeding. Large blood spaces or sinuses are still open, left by the detachment of the pla- centa, although rapidly closing if the uterus becomes well con- tracted.
Clinical note. — The great advantage of a well-contracted uterus is, that it guards against two possible dangers: (i) That of hemorrhage from the open vessels; (2) (and even more serious if possible) that of infection through this wide open surface. The latter is the reason for such scrupulous care which is demanded in the nursing of obstetric cases.
The lochia. The combined decidua vera and decidua reflexa soften, disintegrate and come away from the uterus (with the blood which is oozing from the interior) as lochia. The discharge is known at first as the lochia rubra; then, when it is thinner, as the lochia serosa. Third and lastly, when the disintegrated tissue cells
PLACENTA PREVIA 359
and leucocytes give the discharge a creamy white appearance, it is called the lochia alba.
Placenta previa. — Wherever the ovum attaches itself the de- cidua serotina develops to form the maternal part of the placenta. Should the implantation of the ovum be so low as to encroach upon the internal os, it causes a placenta previa.
Ectopic Gestation. — If an impregnated ovum begins to develop at any point outside the uterus this constitutes an extra-uterine or ectopic gestation. Men- struation ceases as in a normal pregnancy and a decidua vera begins to form, but is often shed at two or three months. Very infrequently the develop- ment of the ovum and fetus goes on to term, when delivery must be by abdom- inal section, but the usual course is rupture of the containing part and inter- nal hemorrhage, necessitating an operation of emergency.
In all extra-uterine or ectopic pregnancies the descriptive name is derived from the abnormal location, as tubal, ovarian, etc., etc.
The child-bearing age begins at puberty or the time of develop- ment of the generative organs and the establishment of ovulation and menstruation. It continues until the climacteric or menopause which marks the cessation of menstruation.
CHAPTER XXVI A BRIEF STUDY OF IMPORTANT REGIONS
THE HEAD AND NECK
The scalp. — Observe the larger arteries — the supraorbital in front, the temporal and posterior auricular at the sides, and occipital at the back — that their general course is upward toward the vertex, and therefore a bandage may be so adjusted around the head as to cut off the blood supply to a great extent.
The nerves have similar names and take a similar course.
The tense temporal fascia covers the temporal muscle above the zygoma.
THE FACE
The main artery, external maxillary (or facial), runs obliquely upward toward the side of the nose; its course is tortuous, so that the play of the facial muscles will not interfere with the passage of the blood current. The facial vein is lateral to the artery and not very close to it. Pulsation of the artery may be felt where it crosses the lower border of the mandible, about one inch in front of the angle.
The external carotid artery bifurcates in the substance of the parotid gland in front of the ear, forming the temporal and internal maxillary arteries. The pulsation of the temporal is felt as it crosses the zygoma, and both here and over the external maxillary on the border of the mandible, the character of the heart's action may be appreciated while the patient is under the influence of ether.
The motor nerves (facial nerve) come through the parotid gland and radiate on the side of the face, transversely toward the nose, upward toward the eye and forehead, and downward toward the neck.
Sensory nerves, branches of the trifacial (trigeminus) , appear at
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STRUCTURES OF THE NECK 361
the three foramina mentioned elsewhere — supraorbital, infra- orbital and mental — the three particularly sensitive spots in the front of the face.
Practical note. — The tongue muscles and the floor of the mouth (mylo-hyoid muscle) are both connected with the mandible. Therefore, if the jaw be held forward and upward, it will control the position of the tongue when the muscles are relaxed, as under ether. Hence, the necessity for this precaution, to prevent the tongue from falling back into the throat.
FIG. 232. — SUPERFICIAL VESSELS OF HEAD.
THE NECK
The skin of the back of the neck is very tough and the fascia very dense. These facts account for the pain of inflammation here, due to the consequent pressure upon the rather numerous nerves, as in carbuncle.
The spine of the seventh cervical vertebra is always easily felt. This is the vertebra prominens.
The two sterno-cleido-mastoid muscles are conspicuous at the side of the neck, situated near each other at their origin, and di- verging above. The thyroid cartilage of the larynx projects in front — the so-called Adam's apple. The external jugular vein runs from behind the ear downward toward the middle of the clavicle, and is covered by the pla'tysma muscle. It is sometimes selected for the operation of "bleeding," or phlebotomy, and the incision
362 ANATOMY AND PHYSIOLOGY
to expose the vein is made across the muscle fibers, because by their retraction the 'Vessel is well uncovered (Fig. 76).
The sternomastoid and trapezius are the muscles affected in the commonest form of wry-neck or torticollis, which is usually due to spasm of the muscles.
THE TRIANGLES OF THE NECK
These are spaces between certain muscles, as follows: In front of the ster no-mas toid is an anterior triangle divided by the superior
FIG. 233. — TRIANGLES OF THE NECK.
C, Carotid triangle; M, muscular triangle; O, occipital triangle; S, subclavian triangle; D, digastric triangle.
belly of the omo-hyoid into two, called the carotid and muscular triangles; behind the sterno-mastoid is & posterior triangle divided by the inferior belly of the omo-hyoid into two, called the occipital and subclavian triangles.
In the muscular triangle is the common carotid artery, with the internal jugular vein on the lateral side of it, and the vagus nerve behind them both.
In the carotid triangle the same structures are found, but
THE THORAX 363
here the artery divides, forming the external and internal carotid arteries at about the level of the upper border of the thyroid cartilage, or "Adam's apple."
Surgical note. — The carotid is called the triangle of election because, since the vessels are near the surface, the surgeon would naturally choose, or elect, this place for the operation of ligation. In the muscular triangle the vessels are more deeply placed and covered by the lower portion of the sterno-mas- toid. Ligation of the artery would be done here only under necessity, so it is called the triangle of necessity.
Occipital triangle. — The occipital artery and nerve run through this triangle.
Subclavian triangle. — Most important structures are sub- daman artery and vein, brachial plexus, and phrenic nerve.
Clinical note. — Pressure in this triangle, close to the clavicle, will be felt by the nerves of the brachial plexus. Pressure downward and backward close* to the sterno-mastoid will compress the subclavian artery against the first rib. Its pulsation is plainly felt.
Submaxillary triangle. — This is a small space marked off from the carotid by the digastric muscle. It contains the submaxillary gland and external maxillary artery.
THE THORAX AND THORACIC VISCERA
The bony thorax is narrow above and broad below, but the proportions are reversed in the completed human body by the presence of the large muscles which connect the upper extremity with the thorax.
Observe the transverse ridge on the sternum, marking. Itihe, func- tion of the first and second pieces (the manubrium and the body). The second rib joins the sternum at this ridge (Fig. 234).
The boundaries of the completed thorax are the spinal column at the back, the sternum in front, and the ribs at the sides, with the intercostal muscles in the intercostal spaces and the diaphragm in the floor. It is covered behind by the muscles of the back, while the anterior serratus is on the side and the pectoral muscles are in front. The shoulder blades are placed behind the thorax.
The intercostal arteries and nerves are protected from injury , by their position under the borders of the ribs. A stab- wound would have to be directed upward to reach them.
All muscles which are attached to the ribs are muscles of res-
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ANATOMY AND PHYSIOLOGY
piration, the intercostals having considerable power, but the dia- phragm being most important. When it contracts it is depressed, increasing the depth of the thoracic cavity, while the other muscles broaden the cavity by lifting the ribs, and thus room is made for expansion of the lungs in inspiration. As the ribs fall and the diaphragm ceases to contract, it rises, returning to its dome shape, and thus the air is pressed from the lungs in expiration. These
FIG. 234.— THORACIC AND ABDOMINAL VISCERA, ANTERIOR. — (Deaver.)
two acts complete a respiration, or an act of breathing, which occurs normally about eighteen times in a minute. If respiration is very difficult other muscles are called into play, as in asthma, when the struggle for breath is so great that " forced inspiration" is necessary.
The erector spinae muscles are always on duty, to steady the spine in order that the ribs may have a point of departure.
The cardiac impulse is felt (sometimes it may be seen) between
THORACIC AND ABDOMINAL VISCERA 365
the fifth and sixth ribs, half way between the sternum and the nipple line.
The mammary gland covers the front part of the spaces from the third to the fifth ribs. It lies between layers of the superficial fascia in front of the pectoralis major muscle.
The superior opening transmits the trachea, esophagus, and important vessels and nerves. The floor (or diaphragm) has three openings — one for the passage of the aorta and thoracic duct, one for • the inferior vena cava, and one for the esophagus and vagus nerves.
The thoracic viscera are the esophagus, trachea and bronchi, lungs, and heart. The esophagus lies close to the spinal column, and the trachea is in front of the esophagus, dividing into the large bronchi, whose branches are the bronchial tubes. The heart and large vessels are in the anterior and middle part of the thoracic cavity (Fig. 234).
The heart is wrapped in the pericardium, and each lung is wrapped in a pleural sac which is placed between the lung and the chest wall. An incision through that part of the wall which is bounded by the ribs would pierce the costal pleura and open the pleural cavity. A wound of the lung would injure the pulmonary pleura.
The large nerves in the thoracic cavity are the vagi, lying close to the esophagus, the sympathetic, whose branches form cardiac and pulmonary plexus, and the two phrenic nerves, right and left, running down on either side of the pericardium to the diaphragm.
The mediastinum is the space between the lungs. In it all of the thoracic viscera except the lungs are situated.
THE ABDOMEN, ABDOMINAL VISCERA, AND PERITONEUM
The boundaries of the completed abdomen are the spinal column and quadratus lumborum muscles at the back, the hip-bones below, the rectus muscles in front, and the broad fiat muscles at the side. The diaphragm is its roof. The transversalis fascia lines the cavity, and the peritoneum is within the fascia, held to it by areolar tissue called subperitoneal or subserous tissue.
On the anterior surface of the abdomen observe the outline made by the lower ribs, between the thorax and abdomen, the two sides meeting in the subcostal angle just below the sternum. The
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ANATOMY AND PHYSIOLOGY
scrobiculus cordis, or pit of the stomach, is a slight depression at the very point of the subcostal angle, caused by a weak spot in the attachment of the abdominal muscles. If the abdomen is greatly distended, the depression disappears. The linea alba is between the two rectus muscles, and the semilunar lines (or line<z semi- lunares) are at the sides of the recti. The transverse lines (linea transversce) may be seen when the recti contract.
The subcutaneous inguinal ring is just above the tubercle of the pubic bone; the abdominal inguinal ring is a half inch above the
Tip of ensiform cartilage Costal border
Upper horizontal plane
Lower horizontal plane A, at level of tubercles of iliac crest
Lower horizontal plane B, at evel of anterior iliac spines
Vertical plane A, from middle of Pou part's ligament
Vertical plane B, at outer border of rectus (semi- lunar line)
Summit of symphysis pubis
FIG. 235. — DIAGRAM OF THE ABDOMINAL REGIONS. — (Morris.)
middle of the inguinal ligament. The conjoined tendon is behind the subcutaneous ring.
The abdominal muscles and skin are supplied by the lower intercostal and first lumbar nerves.
The regions of the abdomen are outlined in the following manner: Imagine a horizontal plane passing through the ab- domen at the level of the tenth costal cartilage, and another at the level of the anterior superior spine of the ilium. These would divide it into three portions — upper, middle, and lower. Then imagine two vertical planes passing through the middle point of the inguinal ligament on either side, and dividing each of these three portions into three regions, making nine in all.
THE PERITONEUM 367
The middle region is called the umbilical, having the umbilicus on the anterior surface. Above that is the epigastric, and below it is the hypogastric. At the sides of the epigastric region are the right and left hypochondriac. At the sides of the umbilical region are the right and left lumbar; and at the sides of the hypogastric region are the right and left iliac, or inguinal.
The abdominal viscera are the stomach, intestines, liver, spleen, pancreas, kidneys, and adrenal bodies. The great vessels are at the back. The sympathetic ganglia are at the sides of the vertebrae, with the celiac and other plexuses situated on the large vessels.
The kidneys are behind all of the other viscera, and the ureters run down close to the posterior wall of the abdomen on their way to the bladder.
The receptaculum chyli, or beginning of the thoracic duct, is in front of the second lumbar vertebra. The inferior vena cava lies on the right side of the aorta.
The principal organ in the epigastric region is the stomach; in the right hypochondriac, the liver; in the left hypochondriac, the spleen. The umbilical region is occupied mostly by small intestines. The right and left kidneys are in the two lumbar regions, with the ascending colon in front of the right, and the descending colon in front of the left kidney. The cecum and appendix are in the right inguinal region; the bladder, in the hypogastric.
Each region contains portions of several viscera in addition to those named. Scarcely any organ save the spleen and cecum can be said to belong to but one region.
The peritoneum is a closed sac of serous membrane like a water-bag, which is placed between the abdominal wall and abdominal viscera. It is practically in front of the viscera, and tucked in around them at the sides. One side of the sac is closely applied to the abdominal wall, and is called the parietal peritoneum, while the other side is fitted to the viscera, and called the visceral peritoneum. Normal peritoneum is perfectly transparent, and the viscera are plainly seen through the visceral layer. The peritoneal cavity contains a little serous fluid and nothing else.
An incision in the abdominal wall, including the parietal per- itoneum, opens the peritoneal cavity. An incision into one of the organs involves also the visceral peritoneum, with these exceptions:
368 ANATOMY AND PHYSIOLOGY
The posterior surface of the liver.
The posterior surface of the ascending colon. The kidneys.
The transverse portion of the duodenum. The front of the bladder behind the symphysis. These parts have no serous layer.
The lowest portion of the peritoneal cavity is in the pelvis, extending down about three and a half inches in front of the rectum. In the female this is called the recto-uterine fossa, or pouch of Douglas. In the male it is the recto-vesical fossa.
The folds of the peritoneum which are connected with the stomach are called omenta (p. 148).
The folds which connect the intestines to the abdominal wall are called mesenteries (p. 147).
The folds which connect other organs to the abdominal or pelvic walls are called ligaments. Those for the bladder are called vesical ligaments.
The ligaments of the liver are the broad, the round, the coronary, and the two lateral ligaments, which connect it to the diaphragm and the anterior abdominal wall.
Sometimes certain little pockets, or fossae, exist in the perito- neum, behind the different portions of intestine. If a loop or knuckle of bowel slips into one of these fossae it may press its way through it and pass behind the peritoneal sac. This is a retro- peritoneal hernia.
THE ISCHIO-RECTAL FOSSA
This is a space between the ischium and the rectum. It is filled with loose connective tissue and adipose, and a few vessels and nerves are therein contained. The skin of the buttock forms the floor of the fossa; the lower part of the rectum is the medial wall; the fascia of the obturator muscle forms the lateral wall.
Surgical note. — If infection occur in this region, a very large abscess might result, the pus burrowing freely in the loose tissues. Ischio-rectal abscess is often caused by internal fistula.
THE AXILLARY SPACE
The axilla is the armpit. Its shape is that of a pyramid, with the apex under the shoulder-girdle at the level of the first rib, the base of the pyramid being the floor of the space and composed of the
STRUCTURES IN AXILLARY SPACE
369
skin and fascia crossing from the thorax to the arm. The walls of the space are formed by muscles — the serratus (principally) on the medial wall, covering the ribs; the long tendon of the biceps in its groove on the lateral wall; the pectoral muscles in the anterior wall, and the subscapularis, latissimus dorsi and teres major in the posterior wall.
The importance of this space is due to the large vessels and nerves, and the lymph nodes, which are found in it. The vessels are the axillary artery and vein; the nerves are the brachial plexus and branches. A chain of superficial lymph nodes lies under the border of the pectoralis major, and a collection of deep ones is grouped around the large vessels; there are also a few near the posterior wall.
Axillary artery
THE ANTE-CUBITAL SPACE
A triangular space in front of the elbow-joint.
Boundaries. — The brachio-radialis, pronator teres, and an
imaginary line connecting the two epicondyles.
Important structures.— Biceps tendon, brachial artery and veins, median nerve. The
Median nerve Brachial artery
Lateral cord
FIG. 236. — AXILLARY SPACE. Axilla laid open by division of anterior wall.
FIG. 237.— ANTE-CUBITAL SPACE
Pronator muscle divided to show
ulnar artery.
artery is between the tendon and the nerve, lying on the brach- ialis muscle. Tendon on lateral side of artery — T-endon, A-rtery, N-erve. The artery divides here.
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SCARP A' s TRIANGLE (TRIGONUM FEMORALE)
This triangle is on the front of the thigh. The base is formed by the inguinal ligament, the lateral border by the upper half of the sartorius, the medial border by the adductor longus, and the apex by the crossing of these two muscles on the medial side of the thigh at about the middle.
Femoral artery Femoral nerve Femoral vein
Deep branch
FIG. 238. — STRUCTURES IN SCARPA'S TRIANGLE; PORTION or SARTORIUS REMOVED.
FIG. 239. — POPLITEAL SPACE. — (Holden.)
a, Biceps; b, peroneal nerve; c, plantaris;
d, lateral head of gastrocnemius; e, semi-
tendinosus;/, semimembranosus ; g, gracilis;
h, sartorius; i, medial head of gastrocnemius.
The most important structures in the triangle are the femoral artery and vein lying side by side, in a line from the middle of the ' base to the apex. The femoral nerve and branches are on the lateral side of the artery.
Order of structures as they pass under the inguinal ligament. V-ein, A-rtery, N-erve, the vein being medialward.
INGUINAL AND FEMORAL CANALS 371
HUNTER'S CANAL (ADDUCTOR CANAL)
This is a passage from the front of the thigh around the medial side to the posterior, beginning at the apex of Scarpa's triangle and ending in the popliteal space by an opening in the adductor magnus muscle. The femoral artery passes through this canal, with the femoral vein on the medial side of the artery. The long saphenous nerve is sometimes within the canal and sometimes outside it.
THE POPLITEAL SPACE
This is a deep diamond-shaped space behind the knee-joint. Its floor is formed, from above downward, by the popliteal surface of the femur, the posterior ligament of the joint, and the popliteus muscle. The boundaries of the upper half of the space are made by the biceps tendon on the lateral side, and the semitendinosus and semimembranosus on the medial side. The boundaries of the lower half are the lateral and medial heads of the gastrocnemius. These muscles are all very prominent, making the space deep. The popliteal space owes its importance to the large vessels and nerves which it contains — the popliteal artery, the popliteal vein, and tibial and common peroneal nerves. They are all deeply situated, the artery being the deepest, and are imbedded in adipose tissue and covered with strong fascia, being thus well protected.
THE INGUINAL RINGS AND INGUINAL CANAL
There is an opening in the aponeurosis of the external oblique muscle just above the pubic bone, which is called the subcutaneous inguinal ring, being under the skin in the inguinal region.
There is an opening in the transfer salis fascia, half an inch above the mid-point of the inguinal ligament. This is called the abdominal inguinal ring, opening into the abdominal cavity in the inguinal region. The passage from one ring to the other is the inguinal canal.
The internal oblique and transversus muscles form the conjoined tendon immediately behind the subcutaneous ring, and their lower muscle fibers arch over the canal, forming its upper boundary.
THE FEMORAL RING AND FEMORAL CANAL
The femoral ring (annulusfemorale) is a weak place in the pelvic wall, under the inguinal ligament, where the femoral vessels do not
372 ANATOMY AND PHYSIOLOGY
occupy the whole of the space in their sheath. It is on the medial side of the vein, bounded medially by Gimbernat's ligament (which is at the medial extremity of the inguinal ligament) and closed by transversalis fascia only, which at this spot is called the crural septum (septum crurale).
The femoral canal extends downward from this ring about three-quarters of an inch in the sheath of the femoral vessels.
HERNIA
Hernia is denned as a tumor formed by the protrusion of con- tents of a cavity through its wall. This may occur at any weak place in the wall, but is most frequent in the region of the inguinal or femoral canals.
If any structure slips accidentally through the inguinal canal it forms an inguinal hernia, which most commonly contains a loop of bowel. To replace the bowel or other structure is to reduce the hernia. If the loop cannot be replaced, the hernia is irreducible; and should it become so distended as to interfere with the circula- tion, it is strangulated.
In direct inguinal hernia the contents of the tumor have passed directly through the conjoined tendon and subcutaneous ring. In indirect inguinal hernia the contents of the tumor have passed through the whole length of the inguinal canal — that is, first the abdominal ring, then the canal, then the subcutaneous ring.
Umbilical hernia occurs at the umbilicus; ventral hernia at any other part of the abdominal wall, except one or both rings.
Diaphragmatic hernia occurs at a weak or defective point in the diaphragm where an abdominal structure may press its way into the thorax.
In femoral hernia the bowel or other structure passes through the femoral ring into the femoral canal and pushes its way through the femoral sheath at the oval fossa, or saphenous opening.
Femoral hernia is more common in women — inguinal hernia in men.
THE EXTREMITIES COMPARED
Both extremities are servants of the head and trunk. The lower, being fashioned for bearing weight and also for walking or running, are organs of locomotion, transporting the body from place to place as necessity or convenience may dictate; while the
THE EXTREMITIES COMPARED
373
upper are organs of prehension, since they can reach forth and secure various things which are required for the use of the body.
Flexion of the arm is accomplished by a two-headed muscle — the biceps; flexion of the thigh by a double muscle, the ilio-psoas. Extension of the elbow is accomplished by a three-headed muscle, the triceps; extension of the knee requires a powerful four-headed muscle, the quadriceps.
We have learned to apply the terms medial and lateral to the body while in the ana- tomical position, in which the forearm is supinated; therefore the thumb is said to be on the lateral border of the hand, but the leg cannot be supinated, and the great toe lies on the medial border of the foot
Observe that the toes of civilized man are freely flexed and extended, but have no other independent motions. They are slightly affected by the action of plantar muscles, but the foot has lost the suppleness it might have had without wearing shoes. The fin- gers, however, can all be moved sideways; the me-
Ulnar nerve and artery Radial nerve and artery
Branches to hand
FIG. 240. — THE FOREARM, ANTERIOR.
dian line of the hand is a line drawn to the tip of the middle finger, and the digits are said to be abducted or adducted, according as their motion is from or toward this line.
The freedom and mobility of the thumb add very greatly to the usefulness of the hand in grasping, carrying, etc. If the fingertips approach each other, the hand falls into a gently curved position forming a cup, the "cup of Diogenes." If the hand be closed forcibly with the thumb holding the fingers against the palm, it becomes a solid irregular mass, the "fist," and so an ever-available weapon of offense or defense.
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ANATOMY AND PHYSIOLOGY
Suprascapular nerve and artery
The shoulder (and whole upper extremity) is pulled forward
by the action of the anterior serratus on the shoulder blade,, and if this motion is accom- panied by a sudden forcible extension of the arm and fore- arm, that is " striking out from the shoulder."
REVIEW NOTES CONCERNING THE EXTREMITIES
The upper extremity— From the shoulder down, the anterior surface is the flexor surface, and the posterior is the extensor surface of the extremity.
Arm. Anterior. — The bi- ceps muscle, with the median nerve and brachial vessels on its medial border. Posterior. —Triceps muscle, with radial nerve in the groove between the two humeral heads.
Forearm. Anterior (Fig. 240). — Superficial flexor mus- cles and the round pronator from the internal epicondyle. Deep flexor muscles from shafts of the radius and ulna, and median nerve between the su- perficial and deep groups. Posterior. — Extensor muscles and the short supinator from the external epicondyle. La- teral or radial side, brachio- radialis from the external epicondylar ridge.
br
Posterior interosseous
FIG. 241.— THE ARM AND FOREARM 'POSTERIOR.
STRUCTURES IN THE PALM 375
The hand. Palm. — Observe the thenar eminence of thumb muscles; the hypothenar eminence of little-finger muscles, and between them the hollow of the hand, where the long flexor tendons lie. The deep palmar arch is underneath the tendons; the superficial arch lies upon them; the strong palmar fascia holds the tendons in a compartment lined with synovial membrane. Dor sum. — The extensor tendons are plainly seen. The radial artery may be felt in the " anatomic snuff-box" (between two of the extensors of the thumb as it winds around the first metacarpal bone to reach the deep palm).
The long flexor and extensor tendons of the fingers may be plainly felt and seen at the wrist.
The lower extremity. — The inguinal ligament stretches from the spine of the ilium to the tubercle of the pubes.
The femoral artery, femoral vein, and femoral nerve pass under the ligament, the artery lying on the psoas muscle. Their order from the medial side outward is V-ein, A-rtery, N-erve.
From the hip down, the anterior surface is alter- nately flexor and extensor
The posterior surface is exactly the reverse.
Flexor for hip. Extensor for knee. Flexor for ankle. Extensor for toes. Extensor for hip. Flexor for knee. Extensor for ankle. Flexor for toes.
Thigh. — Anterior- and sides of the femur are covered by the quadriceps muscle, which extends the knee. The sartorius muscle crosses from the anterior spine of the ilium to the middle of the medial side of the thigh and down to the tibia, and when it con- tracts it makes a depression rather than an elevation, because it binds the soft tissue under it. Posterior. — The biceps, semi- membranosus and semitendinosus muscles flex the knee; they are hamstring muscles, making the upper boundaries of the popliteal space. The medial side of the thigh is occupied by the adductor muscles, with the obturator nerve and vessels.
Leg. Anterior. — The medial surface of the tibia is called sub- cutaneous because it is not covered by muscles; the long saphenous nerve and vein extend the whole length of this surface.
The anterior tibial muscles occupy the neighboring surfaces of
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ANATOMY AND PHYSIOLOGY
Sciatic nerve
Anterior tibial nerve
Peroneal nerve
I Ant. tib. artery
Tibial nerve Post. tib. artery
FIG. 242.— THE FEMORAL ARTERY. FIG. 243.— THE SCIATIC NERVE.
FEMORAL AND SCIATIC NERVES 377
the tibia and fibula, and their tendons all pass in front of the ankle-joint to flex it (dorsal flexion). The lateral side of the leg is occupied by the peroneus longus and brevis whose tendons pass behind the lateral malleolus to extend the foot. They are ac- companied by the superficial peroneal nerve which supplies them (ant. tibial nerve).
The long tendons for the toes are plainly visible on the dorsum or top of the foot, and also those of the short flexor, which has four tendons belonging to the four medial toes.
Posterior. — The calf muscles, which lift the heel, completely cover the deep muscles whose tendons pass into the sole of the foot behind the medial malleolus to extend the foot.
The deep, or posterior tibial muscles, lie between tibia and fibula bound down by the deep transverse fascia of the leg.
The large nerves for the lower extremity are the femoral and the sciatic.
The femoral comes under the inguinal ligament into Scarpa's triangle and immediately breaks up into branches which supply the structures of the thigh, the long saphenous nerve being the only branch to go below the knee. It runs all the way to the medial border of the foot.
The sciatic comes through the great sciatic notch, descending between the great trochanter and the tuber of the ischium into the back of the thigh, to divide at the popliteal space into the tibial and the common peroneal nerves. The tibial nerve continues under the calf muscles and into the plantar region. The peroneal nerve winds around the head of the tibia to the front of the leg, sending the deep peroneal branch to the anterior muscles, and dorsum of the foot.
LOCATION OF LARGE VESSELS AND NERVES IN THE EXTREMITIES
The vessels and nerves are so placed as to be in the least possible danger from pressure or blows. For example, the axillary vessels and brachial plexus are deep in the axilla; the brachial vessels and median and ulnar nerves are on the least exposed side of the arm, and they pass in front of the elbow-joint where the motion of the joint will not interfere with them. So in the fore-
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arm, the radial and ulnar arteries and nerves are protected by muscles. At the wrist they also pass into the hand on the flexor surface.
The large nerve which passes behind the humerus, the radial nerve, is covered by the thick triceps muscle and winds to the front of the bone to pass the elbow-joint on its way to the forearm.
The femoral vessels and nerves are in the fold or flexure of the groin, and they wind around the femur to reach the flexor surface of the knee. Both anterior and posterior tibial arteries are well protected by muscles — the posterior tibial especially — which is under the calf muscles and the transverse fascia of the leg. As it passes the ankle-joint it lies under strong ligaments on the medial side of the joint, where it would not be put on the stretch during any natural movement of the foot nor exposed to blows. Again, the large arteries of the hand are in the palm, while those of the foot are in the sole.
POINTS FOR COMPRESSION or LARGER ARTERIES
The temporal, on the zygoma.
The external maxillary, on the lower border of the mandible.
The subclavian on the first rib, behind the clavicle (downward and backward).
The axillary, on the humerus, in the lower part of the axilla.
The brachial, on the humerus, under medial border of the biceps muscle.
The radial and ulnar, on the bones of same name, in the lower part.
The femoral, against the ramus of the pubic bone, just below the inguinal ligament.
Note. — The subclavian artery is crossed by the scalenus anticus muscle which divides it into first, second, and third por- tions. The axillary artery is crossed by the pectoralis minor muscle, which divides it into first, second, and third portions. The common carotid artery is crossed by the omo-hyoid muscle; the portion below the muscle is in the muscular triangle of the neck; the portion above is the carotid triangle.
CHAPTER XXVII REFERENCE TABLES
379
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ANONYMA JA.caroti CAROTIS COMMUNIS SINISTRA |
SUBCLAVIA SINISTRA. THYREOIDEA SUPERIOR LINGUALIS MAXILLARIS EXTERNA |
PHARYNGEA ASCENDENS |
AURICULARIS POST ERIOR OCCIPITALIS deep brat |
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COMMUNICANS POSTERIOR . . . Connects CHOROIDEA |
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THE SYSTEMIC VI <* veins. ESSES} tperfictal veins, v. basilica empties into v. cephalica empties into |
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GLOSSARY
Abdomen. From a word meaning to conceal. The abdomen contains or conceals the
abdominal organs. Abduction. From a Latin word meaning to lead from. The abducens muscle leads, or
turns, the eye from the median line. Acetabulum. A small vessel or cup for vinegar. The name given to the round
depression or cavity of the hip bone or os coxae, for the head- of the femur. Acid. Sour. Acids redden blue litmus paper. Accommodation. The adjusting or focussing of the eye for vision at different
distances.
Acromegaly. A disease characterized by over-growth of the face and extremities. Acromion. From Greek words meaning summit and shoulder. The process of bone
at the highest point of the shoulder. Adduction. Leading toward.
Adenoid. Resembling a gland or aden. A gland-like growth in the naso-pharynx. Adipose. Fatty. Fat.
Afferent. Bearing toward. Afferent vessels enter organs. Ala. A wing. (Plural, ala). Alimentary. Pertaining to food or aliment, as, the alimentary tract, which contains
the food until it is digested.
Alkaline. Opposite of acid. An alkali turns red litmus paper blue. Alveolus. The border of the jaw bone, named for the cavities which contain the
teeth. (Alveolus^ a little hollow.)
Ameba. A one-celled, jelly-like living being, which constantly changes its form. Ameboid movements. Movements which cause a change of form, like those of the
ameba.
Amphoteric. Like both. Applied to fluids which possess certain qualities resem- bling both alkalies and acids. Amyloid. Starchy or starch like.
Amylopsin. The starch-digesting ferment of pancreatic fluid. Anastomosis. The opening of one vessel into another. Literally — to bring to a
mouth.
Ancon. The elbow. Anconeus, a muscle of the elbow-joint. Annulus. A little ring. (A nnulus ovalis, the oval little ring of the heart.) Anonyma. Without a name.
Antebrachium. The forearm. From ante, before, and brachium, the arm. Antecubital. Applied to the space in front of the elbow. From ante, before, and
cubit, the forearm.
Antrum. A cave. The hollow in the maxilla is called the Antrum of Highmore. Aorta. The largest artery in the body. Apnea. Suspension of breathing.
Aponeurosis. A layer of strong white fibrous tissue (meaning from a tendon). Aqueous. Watery, from aqua, water. Arachnoid. Like a spider's web, for fineness. One of the membranes of the brain
and spinal cord. Areolar. Having little spaces. Arterio-sclerosis. Hardening of the arteries. Artery. A vessel carrying blood away from the heart. Arthrosis. A joint or articulation. Arytenoid. Shaped like the mouth of a pitcher. Assimilation. The taking up of nutriment by the body tissues, in such a manner
that it becomes a part of them. Asphyxia. A condition in which the blood is deprived of oxygen.
389
3QO GLOSSARY
Atlas. A fabled giant who bore the globe upon his shoulders. The first cervical
vertebra, upon which the skull rests. Atrium. A hall, a chamber of the heart where blood enters. Atrophy. Wasting. From a Greek word signifying want of nourishment. Auricular. Shaped like, or belonging to, an ear or auricle. Axis. The second cervical vertebra. Named because of the pivot around which the
atlas revolves (like a wheel around an axis). Axone. An axis. The essential part of a nerve fiber.
Azygos. Without a yoke. The name of certain vessels which are not in pairs. Biceps. Having two heads, as the biceps femoris; biceps brachii. Bicuspid. Having two points or cusps. A bicuspid tooth. Bone corpuscle. A formative cell of bone tissue. Brachialis. Belonging to the arm, or brachium. Bronchus. An air tube. (Plural, bronchi.} The smallest air tubes are called
bronchioles.
Buccinator. From a word meaning trumpet. The blowing or trumpeting muscle. Bursa. Literally, a purse. The burses are small sacs containing fluid and found in
the fascia under skin, or muscles, or tendons. Calcaneus. The heel bone. The tendo calcaneus, or tendo Achillis, is attached to
the calcaneus. Calculus. A stone-like body formed in some fluid of the body. Renal calculus, in
the kidney; biliary c., in the gall-bladder, etc. Callus. A thickened portion of the skin. The material thrown out (provisional
callus) for the repair of fractured bone, to become the permanent callus when
the bone is completely ossified.
Cancellous. Resembling lattice work. A cancellous or spongy bone. Canine. Resembling a dog. Canine teeth, like a dog's teeth. Canthus. The angle at the meeting of upper and lower eyelid; plural canthi. Capillary. Resembling a hair in size. (Capillus, a hair.) Capitellum, or capitulum. A little head, an eminence on the lower extremity of the
humerus.
Capsule. A structure which encloses an organ or part. (The capsule of a joint.) Carbo-hydrate. A substance composed of carbon and water; sugars and starches. Cardiac. Belonging to the heart or cardia. Caries. Decay of bone. Carious, decaying. Carotid. The name of the large arteries of the neck, once thought to cause sleep.
From a Greek word meaning to produce sleep. Caruncle. A small soft projecting tumor. Urethral caruncle, a minute tumor of the
urethral mucous membrane, made up mostly of nerves and vessels. Casein. The proteid or cheesy part of milk. Cast. An albuminous structure moulded in tubular form. Cauda equina. A horse-tail. The name given to the bundle of spinal nerves in the
lower portion of the spinal canal.
Cecum. Blind. The blind pouch at beginning of the large intestine. Celiac (cceliac). Pertaining to the celia or belly. Center. In the nerve system, a center is a collection of gray cells. The central
nerve system comprises the brain and spinal cord, which contain the large nerve
centers. Central convolutions contain a majority of motor centers. Centrifugal. Referring to a force which is exerted from the center outward; a
_ centrifugal nerve conducts impulses from a center. Centripetal. Applied to a force which seeks a center; a centripetal nerve conducts
impulses to a center. Cerebellum. Little brain. Cerumen. The wax of the ear. (Cera, wax.) Cervix. Neck. Cervical, belonging to or resembling a neck. Choana. A funnel. The choana are the posterior openings from the nose into the
pharynx. ,
Choroid. Like the chorion, which is a fetal membrane bearing blood-vessels. Cicatrix. A scar. It is formed of fibrous connective tissue.
Cilia. Eyelashes. Ciliated, having tiny hair-like projections, as ciliated epithelium. Ciliary. The ciliary region of the eye presents radiating lines, caused by folds of the
tissues composing it (ciliary processes}.
GLOSSARY 391
Circumduction. Leading around. This is the motion made when a part is moved
around in a circle, one end being stationary. The extremities, the digits and
the head, may be circumducted.
Circumflex. To bend around. Circumflex arteries wind around the arm or thigh. Circumvallate. Walled around. The circumvallate papillae at the base of the
tongue are encircled by a ridge.
Clavicle. The clavicula, which resembles a very ancient key. Climacteric. Literally, the round of a ladder. Any time of life when the system is
believed to undergo marked and permanent changes; usually applied to the
time of the cessation of menstruation. Coagulation. From coagulare, to curdle. The clotting of blood. Coagulum, a
blood clot. Coccyx. A cuckoo's beak. The bone at the end of the spinal column, named from
its shape. Cochlea. A conch-shell. A cavity of the internal ear resembling a snail-shell in
form. Collateral. From words meaning side and together. Collateral circulation is secured
by the union of branches of two vessels, whereby the main current of fluid may
be carried by this side route if necessary. Colliquative. Literally — a melting together. Colliquative stools are profuse and
watery. Commissure. A placing together. A commissure connects two parts of an organ,
as the commissures of the brain. Communis. Common. Applied to a muscle whose tendons are common to several
organs.
Concha. A shell.
Condyle. A knuckle. A rounded eminence of bone.
Conjunctiva. Connecting. The mucous membrane which connects the under sur- faces of the eyelids. Conoid. Shaped like a cone. Convoluted. Twisted. Co-ordinate. From words meaning together, and to order or regulate. Co-ordination
is the systematic acting together of several parts. Coracoid. Like a crow's beak. The coracoid process of the scapula. Corium. Leather. The deep portion of the skin from which leather is made. Cornea. Horny. The tough transparent membrane in the anterior of the eyeball. Cornua. Plural of cornu, a horn.
Coronal or coronoid. Pertaining to, or resembling a crown. Coronary. The coronary arteries encircle the base of the heart. Corpus callosum. The transverse commissure of the cerebral hemispheres. Corpuscle. A little body. A blood cell. Malpighian corpuscle, a structure in the
kidney. Lymph corpuscle, a cell formed in a lymph gland. Corpus luteum. Yellow body. The substance formed in a ruptured Graafian
follicle of the ovary.
Cortex. Bark. The superficial layer, as the cortex of the brain. Costal. Relating to a rib or costa.
Coxae. Plural of coxa, the hip; also the genitive form, as os coxes, the bone of the hip. Cranium. The part pf the skull which contains the brain. Crest. A ridge of bone, either on a surface or at the border. Cretinism. The condition of a cretin or undeveloped person, both mentally and
physically.
Cribriform. Resembling a sieve.
Cricoid. Like a ring. The cricoid cartilage of the larynx is shaped like a seal ring. Crucial. Like a cross. The crucial ligaments cross each other. Crural. Belonging to or like the lower extremity, from crus, a leg; as the crural
nerve, the crura (or legs) of the diaphragm. Cystic. Relating to a cyst, or a sac containing fluid (cystic duct). A cystic ovary has
cysts developed from its substance. Deglutition. The act of swallowing. Deltoid. Shaped like the Greek letter delta, A. Dental. From dens, a tooth, belonging to a tooth. Dentated. Having points which resemble teeth. Dentition. The eruption or "cutting" of the teeth.
3Q2 GLOSSARY
Diapedesis. A jumping through. The passing of blood cells through the walls of
capillaries.
Diaphoretic. A remedy which increases the amount of perspiration. Diaphragm. A wall across a space. The muscle which separates the cavity of the
thorax from that of the abdomen. Diaphysis. The greater part of the shaft of a bone. Diarthrosis. A movable joint. Diastole. A Greek word meaning a drawing apart. The dilation of the chambers of
the heart.
Digastric. Double bellied as the digastric muscle. Digit. A finger or toe. Distal. Farthest from the head or trunk. Diuretic. A remedy which increases the quantity of urine. Dorsal. Belonging to the dorsum, or back.
Duodenum. Meaning twelve. The duodenum is twelve finger-widths long. Dura mater. Hard mother. The fibrous outer membrane of the brain and spinal
cord.
Dyspnea. Difficult breathing.
Edema. Swelling caused by effusiori of serous fluid into areolar tissues. Efferent. Bearing from. Efferent vessels leave organs.
Effusion. An abnormal pouring out (or secreting) and collection of fluid in the body. Element. A substance which cannot be divided into simpler substances. Eliminate. From words meaning without the threshold. To excrete substances
which are useless. Embryo. The ovum and structures belonging to it constitute the embryo, until the
fourth month of intrauterine life. Endo-. Within. Endocardium, within the heart. Endothelium, the epithelium of
the interior of circulatory organs. Endomysium. The sheath of a muscle-fiber. Endpsteum. The lining of medullary canals in long bones. Ensiform. Sword-shaped. The appendix of the sternum. Enteric. Pertaining to the enter on or intestine, as enteric or typhoid fever. Enzyme. Any ferment in a digestive fluid. Epi. Upon, as epi-condyle, epidermis, epiglottis. Epimysium. The connective-tissue muscle sheath. Epiphysis, A part of a bone which is formed independently, and joined later to
complete the whole bone. Epithelial. Pertaining to epithelium.
Epithelium. The uppermost or superficial layer of cells of a body surface. Erythrocyte. A red cell of the blood. A red corpuscle. Esophagus. From a Greek word meaning to carry food. The esophagus transmits
food from pharynx to stomach.
Ethmoid. Sieve-like. The ethmoid bone has many openings on its surface. Eversion. Turning outward. To evert an eyelid is to fold it back so as to expose the
interior surface.
Excretion. A waste substance to be removed from the body. The process of re- moving waste from the tissues.
Extension. Stretching out or extending. (Bending backward is over-extension.) Exudate. A collection of material which has filtered through the walls of vessels into
surrounding tissues. Falciform. Sickle-shaped. Falx. A sickle. Fascia. A band; plural, fascia. The tissue which binds organs or parts of organs
together. Fauces. From the Latin word faux, the throat. Isthmus of, the space bounded by
the soft-palate, tonsils and tongue. Pillars of, the folds connecting the soft
palate with the tongue and pharynx. (The tonsil is between the pillars of
either side.)
Femoral. Belonging to the femur or thigh bone. Fetus. After the fourth month, the embryo becomes the fetus. Fibrin. A proteid substance of the blood which causes coagulation. Filiform. Thread-like in shape, slender; as filiform papillae of the tongue. Fimbria. A fringe; fimbriated, having a fringe-like appearance.
GLOSSARY 393
Fissure. A cleft or groove, as a fissure of the brain surface.
Fistula. A pipe. A tube-like passage caused by disease.
Flava. Plural of flavus, yellow. Applied to elastic ligaments which contain yellow
elastic tissue.
Flexion. Bending. Flexure, a bend.
Follicle. A very small sac (or bag) containing a secretion. Fontanelle. A little spring. A membranous spot in the infant's skull; the name
suggested by the rising and falling caused by the child's respirations. Foramen. A hole. Plural, foramina. Fossa. A depression or concavity. Fourchette. A little fork. Fovea. A small pit. Thefovea centralis is a tiny depression in the macula lutea of
the retina. Frenum. A curb or bridle. The frenum lingua is the fold of mucous membrane
attaching the tongue to the floor of the mouth. Fundus. The base.
Fungiform. Shaped like a fungus or mushroom. Fusiform. Spindle-shaped.
Ganglion. A knot. (Plural, ganglia.} ^ A collection of nerve cells. Gaster. The stomach. Gastric, belonging to the stomach or gaster. Gastrocnemius. The belly of the leg. The prominent muscle of the calf of the leg. Genioglossus. Belonging to the chin and tongue. Genu. A knee.
Glabella. A little smooth space. The smooth space between the eyebrows. Gladiolus. A little sword. The body of the sternum. Gland. A collection of cells which can form a secretion or an excretion. Glans. The head of the clitoris or penis.
Glenoid. Having the form of a shallow cavity. Belonging to a cavity. Glossopharyngeal. Belonging to the tongue and pharynx. Glottis. The upper opening of the larynx. Epiglottis, the leaf-shaped cartilage
upon the upper border of the larynx. Glucose. Grape sugar. Dextrose. Gluteus. Belonging to the gluteus or buttock. Glycogen. A white substance formed principally in the liver. Sometimes called
animal starch.
Gustatory. Associated with the sense of taste. Gyre. From gyrus, a circle. A convolution (referring to the convolutions of the
brain).
Haversian. Name applied to the tiny canals in bone tissue, from the English anato- mist Havers.
Hepatic. Belonging to the liver or kepar. Hemoglobin. The oxygen-carrying substance of red blood cells, to which their color
is due.
Hemolysis. Destruction of red blood cells. Hemorrhoidal. From a word meaning flowing with blood. Pertaining to a hemor-
rhoid or pile. Hilum. Literally, a little thing. Applied to the depression where vessels enter and
leave an organ.
Hormones. Chemical substances (character unknown), formed (probably) in duct- less glands, and conveyed by the blood to other organs, to influence thei
activity.
Hyaline. Resembling glass. Hyaloid has a similar meaning. Hydration. Saturating with water. Hydrocephalus. A collection of fluid either within the ventricles or outside of the
brain.
Hyoid. U-shaped, as the hyoid bone. Hypertrophy. Over-growth. Derived from two Greek words meaning too much
nourishment. Hypochondrium. Under the cartilage. The hypochondriac region is under the
cartilages of ribs. (Hypo- under.)
Hypodermoclysis. Injection of fluid under the skin — in quantity. Hypogastric. Under the stomach. Hypoglossal. Under the tongue.
394 GLOSSARY
Hypothenar. Under the palm or sole. The eminence on the medial side of the
palm or the sole. Ileum. A roll or twist; the portion of small intestine which appears rolled or
convoluted.
Ilium. The upper portion of the hip-bone or os coxa. Incisor. A cutting instrument. The front teeth are incisors. Index. Indicator. The first finger named from its common use. Induration. Hardening of the tissues. Infra. Beneath.
Infundibulurn. A funnel-shaped space or part. Inhibition. The restraining or stopping of normal action. Inguinal. Belonging to or near to the thigh or inguen. Inlet. The superior opening or brim or strait of the pelvis. Innominatum'. Unnamed. Inorganic. A term applied to certain substances, mostly mineral,"found in all organs
but not produced by them. Instep. The bend of the foot, dorsal aspect.
Inter. Between, as intercostal, between ribs; intercellular, between cells, etc. Inversion. A turning in, as inversion of the eyelashes; inversion of the foot. Invertin. The ferment of intestinal juice. Involution. The changing back to a former condition, of an organ which has fulfilled
a function, as the involution of the uterus after parturition.
Iris. A circle or halo of colors. The colored circle behind the cornea of the eye. Ischium. The lowest part of the hip-bone or os coxes.
Jejunum. Empty. The third portion of the small intestine, usually found empty. Jugular. Belonging to the neck orjugulum. Kidney or ren (plural, renes). An important organ of elimination or excretion, in
which the urine is formed. Labium. A lip. (Plural, labia).
Lacrimal. Having to do with tears or lacryma, as the lacrimal gland. Lacteal. Like milk (from lac, milk). The lacteals are lymph- vessels which carry the
milky-looking chyle. Lactose. Milk sugar.
Lambdoid. Resembling the Greek letter lambda, X. Lamella. A little plate, or thin layer. Lamina. A plate or layer. Larynx. The part of the air-passage extending from the base of the tongue to the
trachea.
Latissimus. Broadest. Latissimus dor si, broadest of the back. ^ Lens. A glass or crystal curved and shaped to change the direction of (or refract)
rays of light.
Lentiform. Shaped like a lens. Leptomeningitis. Inflammation of the thin membranes of the brain — the arachnoid
and pia mater.
Lesion. The effect of an injury, or of disease, in a tissue. Leucocyte. A white cell of the blood or lymph. Leucocytosis, an increase in the
number of leucocytes.
Levator. A lifter. Levatar palpebrce, lifter of the eyelid. Linea. A line. Linea alba. A white line. Linea aspera. A rough line. Lingual. Belonging to the tongue or lingua. Lobule. A little lobe. Lumbar. Belonging to the loin or lumbus. Macula. A spot. Macula lutea, yellow spot. Major. Greater or larger. Malar. Belonging to the cheek or mala. Malleolus. A little hammer. The two malleoli are the lower extremities of tibia
and fibula.
Mammary. Pertaining to the breast or mamma. Mandible. Derived from mandere, to chew. The lower jaw-bone. Manubrium. A handle. The first part of the sternum. Masseter. A chewer. One of the muscles of mastication or chewing.
GLOSSARY 395
Mastitis. Inflammation of the breast.
Mastoid. Shaped like a breast.
Maxilla. The jaw-bone. Applied to the upper jaw-bone.
Meatus. A passage.
Medial. Toward the middle line.
Median. Middle, as the median line of the body.
Mediastinum. From Latin words meaning to stand in the midst. The space in the
middle of the thorax. Medulla. Marrow.
Medullary. Pertaining to, or like, marrow. The medullary canals contain marrow. Meninges. Membranes. Membranes of the brain and spinal cord. Mental. From the Latin word mens, the mind. Mental. From the Latin word mentum, the chin. Mesentery. From two Greek words, meaning middle and bowel. (The mesentery
connects the bowel with the posterior abdominal wall.) Metastasis. From a Greek word meaning to transpose. Minimus. Least or smallest. Minimi digiti, of the smallest digit. Minor. Lesser.
Mitral. Resembling a miter in outline.
Molar. Like a mill-storie or mola. The molar teeth grind the food. Mucous. Containing or resembling mucus.
Mucus. A thick clear fluid secreted by the cells of mucous membranes. Naris. The nostril. (Plural, nares.) Navicular. Boat-shaped, as the navicular bone.
Necrosis. The death of a portion of tissue, while still surrounded by living structures. Neural. Pertaining to nerves. The neural axis is the spinal cord. The neural
canal is the spinal canal. The neural cavity contains the brain and spinal cord. Neuron. A single nerve cell with its branches. Nucha. The nape of the neck.
Nucleolus. A smaller nucleus within the nucleus of a cell. Nucleus. A small round body near the center of a cell. The most important part
of a nucleated cell. Neuron. A unit of the nerve tissues. It consists of cell body or center, axon and
terminal divisions. Nutrient. Nourishing.
Nutrition. The process of nourishing the cells of living tissues. Olecranon. The large process at the upper end of the ulna. The head of the elbow. Occipital. Belonging to the back of the head, or the occiput. Odontoid. Resembling a tooth in shape. Omentum. A fold of peritoneum connected with the stomach. Omos. The shoulder. Omo-hyoid, belonging to shoulder and hyoid bone, as the
omo-hyoid muscle.
Ophthalmic. Belonging to the eye or ophthalmos. Ora serrata. The serrated or toothed margin of the retina. Orbicular. Ring-shaped. A ligament which resembles a little circle. Organ. A structure designed for a particular function or use. Organic substances
are formed in, or by, organs.
Os. A bone. (Plural, ossa.) Ossicle, a little bone. Os. A mouth. (Plural, ora.) Osseous. Bony.
Ossification. The formation of bone. Osteology. The science which treats of bones.
Ostium venosum. A venous door. The door or opening from an atrium to a ven- tricle in the heart, for the passage of venous blood. Outlet. The inferior opening or strait, of the pelvis. Ovum. An egg. (Plural, ova.}
Palpebra. An eyelid. Palpebral fissure, the Assure between the eyelids. Pancreas. From words meaning all and flesh. Pancreatic fluid digests ail foods. Papilla. A Latin word meaning a nipple. A soft conic eminence. Parietal. Resembling a wall (paries').
Parotid. Near the ear. The parotid gland is around the external ear. Parturition. The act of bringing forth, or giving birth to, young. Patella. A little pan. The sesamoid bone in front of the knee-joint; the "knee
pan."
396 GLOSSARY
Pectoral. Connected with the breast, as pectoral muscles. Pedicle. A little foot. Peduncle has a similar meaning. Pelvis. A basin. The cavity in the lowest part of the trunk. Pericardium. Around the heart. Perichondrium. Around cartilage.
Perimysium. The connective tissue around small bundles of muscle fibers. Perinea!. Pertaining to the perineum, that region of the body in front of the anus. Periosteum. Around bone.
Peristalsis. From two Greek words, meaning around and constriction. The intes- tinal movements which propel the food. Peritoneum. From two Greek words, meaning around and to stretch. The serous
membrane around abdominal organs. Peroneal. Relating to the fibula or perone. Peroneal nerves supply muscles on the
fibula.
Petrous. Hard, like a rock. Phagocyte. White blood-cells having the power to take micro-organisms into their
substance and to digest them. Phalanges. Plural of phalanx, a body of troops drawn up closely together. The
fingers and toes. Pharynx. That part of the food passage which connects the mouth and esophagus.
The upper part is the naso-pharynx, an air passage.
Phlebotomy. Cutting a vein. The operation of bleeding or venesection. Phrenic. Pertaining to the phren or diaphragm, as, the phrenic nerves. Pia mater. Tender mother. The delicate membrane which bears the blood-vessels
of brain and cord. Pigment. Coloring matter.
Plantar. Belonging to the sole of the foot or planta. Plasma. Something moulded. The name given to the fluid portion of the blood,
from which tissues are formed. Lymph plasma, the fluid portion of lymph.
Muscle plasma, the fluid portion of the contents of a muscle cell. Platysma. Broad. Platysma muscle. Pleura. A side. The name of the serous membrane which lines the thorax and
covers the lungs. Plexus. A network. An arrangement of vessels and nerves which appear to be
woven together.
Pneumogastric. Belonging to the lungs and stomach. Pollicis. Genitive form of pollex, the thumb. Polymorphonuclear. Having nuclei of various shapes. Poples. The ham; a space behind the knee (popliteal space). Popliteal. Belonging to the poples or back of the knee. Porta. A gate. The portal vein enters the porta or gate of the liver. Prehension. Taking hold of.
Pre-molar. Applied to the teeth which stand immediately in front of the molars. Process. In anatomy, a projection. Pronation. Literally, bending forward. The position of the hand when the thumb
is toward the body. The act of turning the hand face downward, or in the
prone position. Prostate. From Greek words meaning to stand before. The prostate gland is in
front of the neck of the bladder.
Protoplasm. A simple gelatinous cell substance. Bioplasm. Protuberance. A knob-like projection. Proximal. Near the head or trunk. Psychic. Pertaining to the mind. Pterygoid. Wing-shaped. Pubes. The anterior portion of the os coxae. Pulmonary. Pertaining to the lung or pulmo. Quadriceps. Four headed. Rachitis. From two words meaning spinal column and inflammation. A disease in
which the bones are deficient in lime salts. Radius. A rod or spoke. The lateral bone of the forearm. Ramus. A branch, as the ramus of the mandible. Raphe. A seam. The union of two parts in a line, like a seam.
GLOSSARY 397
Reaction. Response to a stimulus or test. The iris reacts to the stimulus of light.
Urine reacts to the litmus test.
Reflex action. The simplest form of nerve response.
Receptaculum chyli. Receptacle of the chyle, the beginning of the thoracic duct. Recession. Withdrawal, as the margin of the gums from the teeth. Rectus. Straight, as rectus muscles. Rectum has the same meaning. Recurrent. Running back. Recurrent arteries turn back. Renal. Pertaining to the ren or kidney. Retina. A net. The complicated nerve coat of the eye.
Rigor mortis. Rigidity of death. The muscular stiffness which occurs after death. Rugae. Folds. (Plural of ruga.) Wrinkles. Saccharose. Cane sugar. Sacral. Relating to the sacrum, or bone which protects the pelvic organs which
were held sacred by the ancients.
Sagittal. Like an arrow — straight. The straight suture of the skull. Saline. Salty.
Saliva. The mixed secretions of glands of the mouth and salivary glands. Saphenous. Manifest or plainly seen. The large superficial vein on the medial
side of the lower extremity and the longest vein in the body. Sartorius. From the Latin sartor, tailor. The "tailor muscle." Sciatic. Ischiatic. Pertaining to the ischium.
Sclerotic. Hard. The sclerotic is the tough fibrous coat of the eye; the sclera. Scrobiculus cordis. Literally, pit of the heart. The little depression at the end of
the sternum. The "pit of the stomach."
Sebaceous. Applied to the glands which produce the oil or sebum of the skin. Secretion. A substance either nourishing or useful, formed by glandular cells. Septum. A partition. (Plural, septa.)
Serous. Of the nature of serum, a thin watery fluid derived from the blood. Serrated. Having teeth like the border of a saw. (The border of the serratus ant.
muscle is thus.)
Serum. A watery fluid separated from blood.
Sesamoid. Resembling a grain in form. Applied to small nodules of bone some- times found in tendons. Shaft. The main portion of a long bone. Sigmoid. Curved like the letter S. As the sigmoid (or transverse) sinus; the
sigmoid colon. Sinus. A curve, or a hollow. A bone sinus contains air. An abnormal passage
opening on the surface of the body is sometimes called a sinus. Soluble. That which can be dissolved or made into a solution. Specific gravity. The weight of a substance, judged in comparison with an accepted
standard. In the case of urine, the standard is an equal volume of distilled
water — at greatest density. Sphenoid. Wedge-shaped. Sphincter. A muscle which closes an orifice. Splanchnic. Pertaining to the viscera or internal organs. Squamous. Shaped like a scale. Steapsin. The pancreatic ferment which digests fats. Stereognosis. The faculty of recognition of objects by handling them. Sternum. Breast bone.
Stimulus. That which excites activity or function. Striated. Striped.
Styloid. Pointed, like the stylus, which was used in ancient times for writing. Sub. Under.
Subcutaneous. Under the skin. Submucous. Under mucous membrane. Subserous. Under serous membrane. Sudoriferous. Bearing sweat, as sudoriferous glands. (Sudoriparous has the same
meaning.) Super. Above.
Superciliary. Above the eyelashes.
Supercilium. The eyebrow, or prominence above the eyelashes. Supination. The attitude of one lying on the back. The position of the hand when
the little finger is next to the body, or when lying upon the back.
398 GLOSSARY
Supra. Above.
Sural. Belonging to the calf or sura, as the sural muscles.
Surgical neck. The constriction below the head of a long bone at the narrowest portion of the shaft. The anatomic neck is the constriction (however slight) immediately next to the head, between it and the shaft. The surgical neck of the humerus and the anatomic neck of the femur are best examples.
Suture. A seam. (Latin, sutura.) The joints of the cranium are sutures.
Symphysis. A growing together, as the symphysis of the mandible.
Synarthrosis. An immovable joint.
Synovia. A fluid resembling the white of an egg, found in joint cavities and vaginal synovial membranes.
Systole. A Greek word meaning contraction. The contraction of the chambers of the heart.
Talus. The ankle bone upon which the tibia rests.
Tendo Achillis. The tendon of Achilles. The tendon of calf muscles attached to the calcaneus or heel bone by which Achilles was held when his mother sub- merged him in the river Styx, to render him invulnerable. Only the heel remained un-wetted.
Tentorium. A tent. The tentorium cerebelli (of the cerebellum) covers the cere- bellum.
Teres. Round. (Ligamenlum teres — round ligament.)
Testes, or Testicles. The glandular bodies which secrete semen.
Thalamus. A Greek word meaning a bed. The optic thalamus is in the base or bed of the brain.
Thenar. Relating to the palm or sole. Hypothenar — under the palm or sole — applied tothe eminences on the side corresponding to the little finger or toe.
Thorax. The chest. The portion of the trunk which contains the heart and lungs.
Thyroid or thyreoid. Shield shaped.
Torticollis. Twisted neck, wry neck.
Trabeculae. Little beams. (Plural of trabecula.} The cross bands of connective tissue which support soft structures — as in the spleen.
Transudation. The passing of fluid through a membrane, as of the blood serum through the walls of vessels.
Trapezium. A four-sided symmetrical figure. Trapezoid, resembling a trapezium, but not symmetrical. Trapezius, applied to a muscle of the back.
Triceps. Three headed.
Trigone. A space or surface having three angles or corners.
Trochanter. From a word signifying a wheel. (The muscles which are attached to the trochanters roll the femurs.)
Trochlea. A pulley. A trochlear surface is a grooved convexity, as the trochlea of the humerus.
Trypsin. The ferment of the pancreas which digests proteids.
Tuber. A swelling or bump.
Tubercle. A small projection like a swelling.
Tuberosity. A large projection on a bone.
Tumor. A swelling of soft tissues.
Turbinated. Rolled, like a scroll.
Tympany. The condition caused by inflation of intestines with gas, so that they sound hollow upon percussion, like a tympanum or drum.
Ulna. A cubit; the elbow. The longer bone in the medial side of the forearm. ^
Umbilicus. From a Latin word, umbo, the name of the elevated or depressed point in the middle of an oval shield.
Ungual. Belonging to the nail or unguis.
Urea. A substance representing the chief nitrogenous product of tissue waste.
Ureter. The duct of the kidney, which conveys urine to the bladder.
Urethra. The passage through which urine is expelled from the bladder.
Uvula. From uva, a grape, or cluster of grapes (which hangs down from the branch where it grows).
Vaginal. Like a sheath.
Vagus. From vagare, to wander.
Vallate. Situated in a cavity which is surrounded by a ridge.
Valvulae conniventes. Little valve-like folds. Seen on the mucous coat of the small intestine.
GLOSSARY 399
Vascular. Having many blood-vessels.
Vaso -motor. Literally, vessel-mover. Applied to the nerves which dilate blood- vessels or contract them, or vaso-dilators and vase-constrictors.
Velum. Veil. Velum palati, the veil, or soft hanging portion of the palate or roof of the mouth.
Vena cava. A large hollow vein.
Venesection. Cutting a vein. "Bleeding" or phlebotomy.
Ventral. Toward the front of the body, as the ventral cavity.
Ventricle. Literally, a little belly. From the Latin venter. A cavity in the brain, or in the heart.
Vermiform. Worm-shaped.
Vertebra. From a Latin word meaning to turn. Certain movements of the verte- brae turn the body from side to side.
Vertex. The crown of the head.
Vestibule. A cavity of the internal ear through which stimulating impulses are transmitted to auditory and vestibular nerves.
Villus. A hair (pi. villi). The villi of the intestine are hair-like in shape and belong to the mucous coat.
Viscus. An internal organ of the head or trunk. (Plural, viscera.)
Vitreous. Glassy. The vitreous humor resembles glass in appearance. The vitreous layers of the skull are brittle like glass.
Volar. Belonging to the palm or vola.
Xyphoid. Sword-shaped. The third piece of the sternum is the xyphoid or ensiform appendix.
Zygoma. A yoke. The arch of bone at the side of the face formed by zygomatic processes of frontal and maxillary bones.
INDEX
Abdomen, abdominal organs, 365, 367
regions of, 366
Abdominal brain (Solar Plexus), 318 Abdominal wall, 94 Absorption, 166, 169 Accommodation, 338 Acetabulum, 48 Acromegaly, 267 Adipose tissue, 4, 5 Adrenal bodies, 264 Air or atmosphere, 23 1
air cells, 236
tidal volume, 239 Alimentary canal, 130 Ameboid movements, 173 Anatomic position and use of terms, i Animal heat, 274 Antrum of Highmore, 25 Aorta, 187, 189 Apnea, 242 Aponeurosis, description of, 84
vertebral, 86 Apophysis, 15
Appendix ceci (vermiformis), 144 Aqueduct of Sylvius (of cerebrum),
303
Aqueous humor, 338 Arachnoid of brain, 305
of cord, 281
Arbor vitae, 302 (illus. 301) Arches of foot, 73
of hand, 192, 193
of vertebrae, 39
palatine, 133
superciliary, 21
supraorbital, 20
zygomatic, 33 Areolar tissue, 5 Arm, bone of, 56
muscles of, 104
Arterioles and arteries, 174, 175 Arterio-sclerosis, 216
26 401
Articular surface, 13 Articulations or joints, 17
of cranium, 24
of face, 28
of lower extremity, 70
of pelvis, 49, 50
of spinal column, 42
of thorax, 47
of upper extremity, 60 Ascites, 7 Asphyxia, 241 Assimilation, 166 Associated movements, 344 Atlas, 40
Auditory tube (Eustachian), 330 Auricle of heart, 176 Axillary space, 368 Axis (artery), 191
(bone), 40 Axon, 278
Bifurcation of aorta, 198 Bile, 150 Bioplasm, 4 Bladder, urinary, 246 Blood, 171
circulatory organs of, 174
coagulation of, 217
pressure, 216 Bone, articular, 13
markings, 13
nutrition, 15
repair of, 77
tissue, ii Bones, completion of, 76
in infancy, 75
shapes of, 14
structure of, 1 1 Brain, 299
fissures of, 300 Brain hemispheres, 300
lobes of, 300
402
INDEX
Breast (mammary gland), 260
muscles of, 103 Bronchi, 234 Bronchial muscle, 235 Bursa (plural, burses}, 71, 82
prepatellar, 72
Callus, 78
Canal, adductor, 371
anal, 146
auditory, 329
carotid, 23
central (of cord), 303
femoral, 371
Haversian, 12
Hunter's (or adductor), 371
inguinal, 371
internal auditory, 23
medullary, 14
nasal (or lacrimal), 34
neural, 53
nutrient, 15
semicircular, 331, 332
spinal (neural or dorsal), 43, 53 Cancellous or spongy tissue, 12 Capillaries, 175 Capitulum (capitellum), 56 Capsule, Bowman's, 246
internal, of brain, 301
of joints, 1 8
of lens, 337
of Tenon, 335 Carbohydrates, 153 Cardiac impulse, 177 Carpus, 58
meta, 59 Cartilage, 5
articular, 17
costal, 44
fibro-, semilunar, 70 sterno-clavic., 60 triangular, 62 Cartilages of larynx, 233 Cauda equina, 284 Cavities of body, 53
dorsal or neural, 53
ventral or visceral, 53 Cecum, 144 Cell body (nerve), 277 Cell, description, 4
Centers, brain (illus.), 311, 314
nerve, 279
of ossification, 15 Central fissure, 301 Cerebellum, 302 Cerebral localization, 311 Cerebro-spinal fluid, 280
system, 279
Cerebrum, 300, 322, 324 Cervical nerves, 286 Cervix uteri, 347 Chambers of eye, 338 Cheyne-Stokes breathing, 242 Choroid coat of eye, 336 Chyle, 161, 168, 222 Chyme, 160 Cilia, of air passages, 233, 235
of eyelids, 343 Ciliary muscle, 338 Circular folds (intestine) 142 Circulation (def.), 166
collateral, 195, 200, 380-385
fetal, 209, 211, 356
portal, 208, 209
pulmonary, 185, 187
systemic, 185, 187, 188 Circumcision, 354 Clitoris, 351
Coagulation of blood, 217 Coccyx, 42 Cochlea, 331, 333 Colon, 145 Colostrum, 262 Compact bone tissue, 1 2 Compression of arteries, 378 Condyle (def.), 13 Condyles, occipital, 21
of femur, 66
of mandible, 27
of tibia, 66 Conjoined tendon, 96 Conjunctiva, 336-341 Connective tissue, 5 Coordination, 297, 322 Corium of skin (cutis vera),
253
Cornea, 335
Corpus callosum, 300, 301 (Illust.) Corpuscle of blood, 171, 172, 173 of kidney (Malpighian), 245
INDEX
403
Corpuscle of skin (touch), 254, 327
of spleen, 263 Corpus luteum, 349-350 Cortex of adrenal body, 264
of brain, 299
of kidney, 245 Cranium, 20, 29 Crest (def.), 13
of ilium, 48 Crura of cerebrum, 303
of diaphragm, 98 Crystalline lens, 337 Cutis vera (skin), 253
Dartos, 353
Decidual membrane, 355
Defecation, 165
Deglutition, 158
Dendrite, 277
Dentition (eruption of teeth), 36
Diameters of pelvis, 52
Diapedesis, 173
Diaphragm, 97, 121
of pelvis, no Diaphysis, 15 Diastole of heart, 180 Digestion, 156 Digestive fluids, 131 Duct, common bile, 150
cystic, 150
hepatic, 149, 150
pancreatic, 148
right lymphatic, 223, 228
Stenson's, 134
thoracic, 223, 228
Wharton's, 134 Ductus arteriosus, 210
communis choledochus (or common bile duct), 150
deferens (vas def.), 354 Duodenum, 141, 142 Dura mater, brain, 305
cord, 281 Dyspnea, 242
Ear, 329 Edema, 229 Elastic tissue, 5 Elimination, organs of, 244
Endocardium, 178 Endosteum, 14 Endothelium, 7 Enzymes (def.), 131, 165 Epicardium, 183 Epicondyle of femur, 66
of humerus, 56 Epidermis, 254 Epiglottis, 233 Epiphysis, 15 Epithelium, 6, 7
ciliated, 6, 233
respiratory, 230, 233 Erythrocyte (red cell), 171 Esophagus, 135, 136 Eustachian tube (auditory), 330 Excretion, 270 Expiration, act of, 238 External genital organs, 351 Extremities compared, 372 Eye, 335 Eyebrows, 341 Eyelids, 341
Face, bones of, 24
muscles of, 89, 90, 91
vessels and nerves, 360 Fallopian or uterine tubes, 348 Falx cerebri, 305 Fascia of body, deep, 80
iliac, in
lata, 8 1
lumbar, 82
palmar, 109
pelvic, in
plantar, 118
superficial, 82
temporal, 90
transversalis, 100, in
transverse of leg, 377 Fatigue poisons, 126 Fats, 153, 154 Feces, 164 Fibrin, 218 Fibrous tissue, 5 Fissure of Rolando (central), 300
of Sylvius, 301
transverse of liver (porta), 148 Floor of mouth, 131
404
INDEX
Floor of pelvis, no
of thorax, 98 Fontanelles, 32 Food, absorption of, 166
values, 272 Foods, 153
carbohydrates, fats, proteids, 153,
154, i55 Foot, eversion of, 119
inversion of, 119 Foramen, infraorbital, 31
intervertebral, 44
jugular, 31
magnum, 21
mental, 31
Munro, 303
obturator or thyroid, 49
optic, 34
ovale, 210
sciatic, 50
supraorbital, 21
transverse, 40
vertebral, 39 Forearm, bones of, 57
muscles of, 105 Foreskin (prepuce), 354 Fossa (def.), 13
glenoid, 55
intercondyloid, 66
ischio-rectal, 368
lacrimal, 21
mandibular, 22
navicularis, 351
ovale (heart), 177 (thigh), 82
subscapular, 55 Fossae of skull, 32 Frenum linguae (bridle of tongue), 132
Gall bladder, 150 Ganglia, basal, 301
-semilunar, 318
sympathetic (autonomic), 316 Ganglion, 279
Gasserian, 307
root of spinal nerve, 282 Gastric juice, 139 Glabella, 21
Gladiolus (body of sternum), 44 Glands of Bartholin, 352
Glands, ceruminous, 256, 329
digestive, 131
ductless, 262
Peyer's (or patches), 144
lacrimal, 343
lymph, 223
mammary, 260
Meibomian (tarsal), 342
prostate, 346
salivary, 134
sebaceous, 255
structure of, 8
sudoriferous, 256
tissue, 7 Glottis, 345 Graafian follicle, 349 Greenstick fracture, 56, 77 Glycogen, 168
Hair, 257
Hamstring tendons, 114, 115
Hearing, 329
Heart, 176
cycle of, 1 80
diastole of, 178
function of chambers, 180
muscle, 176
nerves of, 185
sounds, 182
systole of, 180
tendinous cords of, 1 78
valves of, 179 Hematin, 172 Hemoglobin, 172 Hemorrhage, 217
control of, 219
Hemorrhoidal arteries, 198, 199, 200 Hernia, 372
retro-peritoneal, 368 Hilus or hilum, 2
of kidney, 244
of lung, 236
of spleen, 151 Hip-bone (os coxae), 48 Housemaid's knee, 82 Hydrocephalus, 303 Hymen, 352 Hyperemia, 229 Hyperpnea, 242 Hypodermoclysis, 214
INDEX
405
Hypophysis cerebri, 267 Hypothear muscles, 109
Ileum, 142, 143 Ilium (os), 48 Inflammation, 229 Inguinal rings, 371 Inorganic substances of bone, n Insertion of muscles, 85 Inspiration, act of, 238 Instep (arches of foot), 73 Intercellular substance, 4 Intermuscular septa, 81 Interosseous spaces, 57, 66 Intestine, 139
large, 144
small, 141 Iris, 336 Isthmus of fauces, 133
Joint or articulation, 17 immovable, 17 motions of, 18 movable, 17 yielding, 18
Kidney, floating, 252 Kidneys, 244
Labia majora, 351
minora, 351
Labyrinth (ear), 331, 332 Lacteals, 168, 227 Lanugo, 257
Large vessels and nerves (location), 377 Larynx, 233 Leucocytes, 172, 173 Leukemia, 152 Ligament, annular, 109, 119
of Bigelow (Y) ileo-femoral, 69
broad, 350
crucial, 71
deltoid, 72
elastic, 42, 73
Gimbernat's, 372
inguinal (Poupart), 50, 81, 96
of liver, 150
orbicular, 64
of patella, 70, 112
sacro-sciatic, 50
Ligament, suspensory of lens, 337
transverse of ankle, 72 Ligaments of uterus, 350 Ligamentum nuchae, 43
teres, 69, 70 Linea alba, 96
aspera, 66
semilunaris, 95 Lineae trans versae, 97 Liver, 148 Lochia, 358
Lumbo-sacral cord, 291 Lungs, 235 Lymph, 170, 223
capillaries, 221
corpuscles, 223
nodes (lymphatic glands), 223
origin of, 222
spaces, 221
vessels, 221 Lymphatic ducts, 223 Lymphocytes, 223 Lymphoid tissues, 9, 223
Malleolus, lateral, 65
medial, 65 Manubrium, 44 Marrow, 12 Mastication, 157 Meatus, external auditory, 329
of nose, 33, 233
of urethra, 247, 351 Median line, 2 Mediastinum, 365 Medulla (of brain), 302, 322 Medullary canal, 14 Medullated fibers, 277 Membranes, 7
of brain, 305
mucous, serous, synovial, 7
of spinal cord, 281 Menopause (climacteric), 349 Menstruation, 349 Mesentery, 147 Metabolism, 8, 270 Metastasis, 229 Micturition, 249 Milk, 261 Mons veneris, 351
406
INDEX
Motions of eyeball, 343 Moulding of head, 32 Mouth (oral cavity), 131
breathing, 239
Movable joint, description of, 17 Muscle band of His, 177
cell, 83, 122
tissue, 83, 119 Muscles, action of, 126
modifications, 125
of abdomen, 94-97
of back, 85
of breast, 103
of face (or of expression), 89-91
of head and neck, 86, 93
of lower extremity, 109
of mastication, 90
of pelvis, 109, no, in
of upper extremity, 101
ribbon, 92
stimulus of, 122
structure of, 83,
tension of, 120, 122 Myocardium, 176
Nails, 256 Nares, 34, 233 Nasal breathing, 239 Nasopharynx, 135 Necrosis (of bone), 13 Nerve centers, 279
cylinder, 278
plexus, 285
supply to joints, 74 to muscle groups, 128
tissue, 277 Nerves, cervical,. 286
coccygeal, 294
cochlear, 333
cranial, 305
femoral, 292
lumbar, 291
motor, 279, 321
optic, 337
phrenic, 286
pneumogastric, 309
sacral, 292
sciatic, 292
sensory, 281,
Nerves, spinal, 284
thoracic, 291 Neurilemma, 278 Neuron, 277 Nose, 231 Notch, ethmoid, 21
intercondyloid, 65
radial, 57
sciatic, 49
sternal or jugular, 44
supraorbital, 21
Notes clinical, blood-vessels, 214, 216, 219
bones, 28, 34, 37, 38, 43, 56
digestive organs, 133, 139, 144 146, 151, 152
kidney, 248, 249, 250, 251
lymph system, 228, 229, 230
muscles, 88, 125
nerve system, 282, 303, 305, 309,
3i3
pelvic organs, 350, 357
regional, 363
respiratory, 237
skin, 255, 256, 258, 259
special senses, 326, 331, 338, 343
spleen, 152
Notes obstetric, 32, 50 Notes practical and special, blood-ves- sels, 172, 175, 185, 193, 195, 197,
200, 212
bones, 57, 58, 66, 71, 73, 76, 78
muscles, 81, 90, 98, 103, 112, 121
regional, 361 Notes surgical, abscess, 100, 262
blood-vessels, 175, 193
bones, 28, 63, 72, 75, 78
digestive organs, 146
kidney, 248
muscles, 82, 117, 131, 262
nerves, 282, 304, 305, 308
regional, 363, 368 Nucleus and nucleolus, 4
caudate, 301
lentiform, 301 Nutrient artery, 15
Obturator membrane, 49 Olfactory region, 326
INDEX
407
Omentum, 148
Opsonic index, 220
Optic commissure (chiasm), 307
disc, 337
thalamus, 301 Orbit, 33
Organ and organic substance, 7, Origin of blood cells, 172, 173
of muscles, 85 Os coxae or hip bone, 48 Osmosis, 170, 214, 229 Osseous tissue, 5, n Ossicles, 332, 333 Ossification, 14 Ovary and ovum, 348, 349 Ovulation, 349
Palate, hard, 26, 131
soft, 131
Palm, or metacarpus, 59 Pancreas, 148, 263 Papilla of hair, 257
of skin, 254
tongue, 132 Parathyroids, 266 Patella, 68
Peduncles of brain, 303 Pelvic floor, no
girdle, 51
organs, 346 Pelvis, 51 Pepsin, 139 Peptones, 159, 160 Pericardium, 183 Perichondrium, 5 Perineal arteries, 200 Perineum, 353 Perineurium, 279 Periosteum, 13 Peristalsis, 147 Peritoneum, 367 Peri vascular spaces, 221 Perspiration, 258 Peyer's patches, 144 Phagocytes, 173, 214, 230 Phagocytosis, 173 Phalanges, 59 Pharynx, 134, 233 Physiology of blood, 213
Physiology of bone, 78
of brain, 311
of cord, 295
of digestive organs, 153
of kidneys, 248
of lymph system, 228, 230
of muscle, 119
of nerve system, 321
of ovary, 349
of respiratory organs, 237
of skin, 257
of sympathetic nerves, 318, 321
of uterus, 348, 357, 358 Pia mater of brain, 305
of cord, 281 Pillars of fauces, 133 Pituitary body (hypophysis), 267 Placenta, 212, 357
previa, 359 Plasma, 171, 173 Pleura, 236 Plexus, 285
brachial, 287
cardiac, 318
celiac, 318
cervical, 286
hypogastric, 318
lumbar, 291
pulmonary, 318
sacral, 292 Pons varolii, 303 Popliteal plane, 66
space, 114, 371 Porta of liver, 148 Portal vein, 209 Pouch of Douglas, 353 Pregnancy, 357 Process (def.) 13
acromion, 55
alveolar, 26, 27
articular, 39
coracoid, 55
coronoid, 57
frontal, 26
mastoid, 22
odontoid, 40
olecranon, 57
palate, 26
pterygoid, 24
408
INDEX
Process, spinous, 39
styloid, 23 of fibula, 66 of radius, 57 of ulna, 57
transverse, 39
unciform, 58
zygomatic, 26 Promontory, 42 Pronation, 64 Proteids, 153, 154 Protoplasm, 4 Ptyalin, 134, 158 Puberty, 349 Pubic arch, 49
symphysis, 49 Pudendum, 351 Pulse, 181 Pylorus, 138 Pyramids and tracts (medulla), 302
decussation of, 302
Rachitis, 77
Receptaculum chyli, 223 Reciprocal reception, 63 Rectum, 146 Reference tables, 379 Reflex, abdominal, 297
action, 296
patellar, 297
plantar, 297
skin, 297
tendon, 297 Rennin, 139 Respiration, 231
artificial, 242
external, 231
influence of drugs, 241
internal, 231
modifications of, 242
rate of, 238, 239
stimuli, 240, 241
variations, 240, 241, Respiratory sounds, 239 Retina, 337 Ribs, 44 Rigor mortis, 124
Sacrum, 41 Saddle joint, 19, 63
Saliva, 134
Sartorius or "tailor muscle," 112
Scalp, 360
Scarpa's triangle, 370
Schneiderian membrane, 233, 326
Sclera, 335
Scorbiculus cordis, 366
Scrotum, 353
Secreting organs, 7, 269
Secretions, 7, 269
internal, 263, 269 Semilunar notch, 57 Septum, 34
intermuscular, 81 nasal, 34, 232 Serum, 217. 218 Sheath of rectus, 97 Shoulder girdle, 56 Sigmoid groove, 22, 305 Sight, 335 Sinus (def.), 2 ethmoid, 23 frontal, 21 of kidney, 245 maxillary, 25 sagittal, 22 sphenoid, 24
transverse (lateral), 22, 204 Sinusitis, 35 Skeleton, 15
at different ages, 75 Skin, 253
Skull, as a whole, 29 at birth, 32 completion of, 75 points of interest, 29 Smell, 326 Special senses, 325 Speech, 312, 345 Spermatic cord, 354 Sphincter, anal, 146 cardiac, 138 ileo-colic, 143 pyloric, 138 vesical, 247 Spina bifida, 77 Spinal canal, 42, 43 column, 43 cord, 280, 321, 322
INDEX
409
Spinal curves, 44 Spine (def.), 13
intercondyloid, 65
of ilium, 48
of ischium, 49
of pubes, 49
of scapula, 55
of tibia, 65
Splanchnic nerves, 318 Spleen, lien, 151, 264 Spongy or cancellous tissue, 12 Sternum, 44 Stomach (gaster), 137
of infant, 139 Straits of pelvis, 51 Summary, cerebro-spinal nerves, 310
functions of cranial nerves, 314
nerve system, 321
return of lymph, 228
return of venous blood, 207, 208
spinal nerves, 295 Supination, 64 Sutures, 24
Sympathetic (autonomic) nerves, 316 Symphysis pubis, 49, 50 System (def.), 8
Tactile cells, 327 Tables of skull, 29 Tarsus, 67
meta, 68 Taste, 133, 328 Teeth, 35
eruption of, dentition, 36 Temperature of body, 274, 275 Tendinous cords, 198 Tendon of Achilles or tendo calcaneus,
68, 118
Tendons, 84, 85 Tentorium cerebelli, 305 Terminal filament, 280 Testes, 353
Thenar eminences, 109 Thorax, 363 Thrombin, 218 Thymus body, 266 Thyroid (thyreoid) body, 265 Tissues, 4
contractile, 83
Tissues, fluid, 9 Tissue spaces, 80 Tongue, 131, 132 Tonsil, 133
lingual, 133
palatine, 133
pharyngeal, 135 Touch, 327 Trachea, 234 Triangles of neck, 362 Trigone, bladder, 247
femoral, 200, 370 Trochanters, 66 Trochlea, 56 Trophic centers, 297 Trunk, 17, 44
Tuber ischii (tuberosity), 49 Tuberosity of calcaneus, 67 Tympanum, 330
Umbilical artery, 201
cord, 212
vein, 210 Umbilicus, 96 Urea, 249 Ureter, 247 Urethra, 247 Urethral caruncle, 248 Urination (micturition), 249 Urine, 249
Uterine tubes (Fallopian), 348 Uterus, 346 Uvula, 131
Vagina, 350
Vaginal sy no vial membranes, 107
Valve, Eustachian, of heart, 210
Houston's, 146
ileo-cecal, 145 Valves of heart, 179
of veins, 175 Vasa vasorum, 176 Vaso motor nerves, 320 Vein, jugular, 204
portal, 209
umbilical, 209, 210 Veins, 203
azygos, 206
structure, 175
410 INDEX
Velum palati, 131 Vitreous layer (cranial bones), 29
Vena cava inferior, 208 Viscera, abdominal, 367
superior, 206 thoracic, 365
Ventilation, 243 "Vital knot" (nceud vital), 314
Ventricles of brain, 303 Vocal bands and voice, 345
of heart, 177 Vola, palm, 74. Vermis (of cerebellum), 302
Vertebrae, 39, 40, 41 Wharton's jelly, 212 Vertebral aponeurosis, 86
Vertex of skull, 29 Xyphoid appendix, 44 Vestibule (ear), 331
(pudendum), 351 Y-ligament, 70 Villi, 141, 142
Vitreous body, 337 Zygoma (process), 22
31199 tomy and