OSTEOLOGY 



The Nasal Cavity (cavum nasi; nasal fossa). The nasal cavities are two irregular 

 spaces, situated one on either side of the middle line of the face, extending from the 

 base of the cranium to the roof of the mouth, and separated from each other by a 

 thin vertical septum. They open on the face through the pear-shaped anterior nasal 

 aperture, and their posterior openings or choanae communicate, in the fresh 

 state, with the nasal part of the pharynx. They are much narrower above than 

 below, and in the middle than at their anterior or posterior openings: their depth, 

 which is considerable, is greatest in the middle. They communicate with the 

 frontal, ethmoidal, sphenoidal, and maxillary sinuses. Each cavity is bounded 

 by a roof, a floor, a medial and a lateral wall. 



The roof (Figs. 195, 196) is horizontal in its central part, but slopes down- 

 ward in front and behind ; it is formed in front by the nasal bone and the spine 

 of the frontal; in the middle, by the cribriform plate of the ethmoid; and behind, 



Rostrum of sphenoid 



Crest of nasal bones 

 Frontal spine 



Space for triangular 

 cartilage of septum 



Crest of palatines 

 Crest of maxillce 



FIG. 195. Medial wall of left nasal fossa. 



by the body of the sphenoid, the sphenoidal concha, the ala of the vomer and the 

 sphenoidal process of the palatine bone. In the cribriform plate of the ethmoid 

 are the foramina for the olfactory nerves, and on the posterior part of the roof 

 is the opening into the sphenoidal sinus. 



The floor is flattened from before backward and concave from side to side. 

 It is formed by the palatine process of the maxilla and the horizontal part of 

 the palatine bone; near its anterior end is the opening of the incisive canal. 



The medial wall (septum nasi) (Fig. 195), is frequently deflected to one or other 

 side, more often to the left than to the right. It is formed, in front, by the crest 

 of the nasal bones and frontal spine; in the middle, by the perpendicular plate 

 of the ethmoid; behind, by the vomer and the rostrum of the sphenoid; beloiv, 

 by the crest of the maxillae and palatine bones. It presents, in front, a large, 

 triangular notch, which receives the cartilage of the septum; and behind, the 

 free edge of the vomer. Its surface is marked by numerous furrows for vessels 



