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SECTION I
THE NOSE AND PARANASAL SINUSES

J. F. Birrell

CHAPTER 1                   ,,'.*.

ANATOMY AND PHYSIOLOGY^: *

THE EXTERNAL NOSE

The external nose is shaped as a triangular pyramid with its root above and its
base directed downwards, and perforated by two nostrils or anterior nares,
separated by a median septum. The free angle of the external nose is the apex,
connected to the root by the dorsum, the upper part of which is termed the
bridge. Each side of the external nose ends in a rounded eminence, the ala
nasi, which forms the outer boundary of the nostril or anterior naris. The
skin over the apex of the nose is thick and adherent, and contains many
sebaceous glands. The external framework is osseous and cartilaginous. The
nasal bones form the bridge, and each is united above with the frontal bone
and laterally to the frontal process of the maxilla. Four paired cartilages—the
lateral, the greater alar, the lesser alar and the vom,erqnasal---:and one
unpaired cartilage—the septal—complete the external fiaHeworEf and their
inter-relationship is shown in Figs. 1 and 2.

The chief muscles acting upon the external nose are the compressors and
dilators of the ala nasi, and are supplied by the facial nerve. In confirmed
mouth breathers the dilators tend to atrophy from disuse so that the anterior
nares become narrow and slit-like.

Blood supply to the external nose derives from the external maxillary and
ophthalmic arteries, while venous drainage is through the anterior facial and
ophthalmic veins, the latter being a tributary of the cavernous sinus.
Lymphatic drainage follows the anterior facial vein and opens into the
submandibular glands, but other lymphatics drain into the pre^auricular
glands.                                                                                  ~^ ~"

THE NASAL VESTIBULE

This is the name given to the entrance to the nasal cavity, within the nostrils.
It is lined by skin which contains hair follicles, and it ends at the muco-
cutaneous junction. The part between the two nasal vestibules, containing
the anterior end of the nasal septum, is called the columella.

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