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2                    THE NOSE AND PARANASAL SINUSES

THE NASAL CAVITY

The lateral wall of each nasal cavity is convoluted in appearance due to the
three conchae or turbinates (Fig. 3). The superior and middle conchae
constitute the medial surface of the lateral mass of the ethmoid bone. The
inferior concha* is a separate bone attached to the maxilla. Each concha*
overhangs a channel or meatus corresponding in length to the concha 
beneath which it is situated. All three reach forwards from the posterior

Fig. 1. The external nose. 1, Nasal bone; 2, Frontal process of maxilla; 3, Lateral cartilage; 4, Cartilage
of septum; 5, Accessory cartilage; 6, Greater alar cartilage; 7, Lateral^erus; 8, Medial cms.

aperture of the nose, called the posterior naris or choana. The superior
meatus is confined to the posterior third of the lateral wall of the nasal
cavity; the middle meatus runs forward about two-thirds of its length; and
the inferior meatus extends the whole length of the lateral wall of the cavity.
The space above the superior concha is called the spheno-ethmoidal recess.
Between the three conchae and the nasal septum, which separates the two
nasal cavities, is a space called the olfactory cleft.

The ineatuses are of clinical importance in respect of their contents. The
nasolacrimal canal opens into the anterior end of the inferior meatus.
Communication between the paranasal sinuses and the nasal cavity takes
place through openings, or ostia, in the middle and superior meatuses. The
frontal, anterior ethmoidal and maxillary sinuses open into the middle