THE MAXILLA 



103 



perforated by numerous small foramina for the passage of nutrient vessels. It 

 enters into the formation of the roof of the mouth. 



The antrum of Highmore (sinus maxillaris) is a pyramidal cavity hollowed 

 out of the body of the maxilla. It varies much in size. It is in most cases a 

 large cavity, but in some is very small. The apex of the antrum, directed outward, 

 is formed by the malar process; its base by the outer wall of the nose. Its walls 

 are everywhere exceedingly thin, and correspond to the orbital, facial, and zygo- 

 matic surfaces of the body of the bone. The floor is formed by the alveolar process 

 of the maxilla. The roof corresponds to the orbital plate. Its inner wall, or base, 

 presents, in the disarticulated bone, a large, irregular aperture (hiatus maxil- 

 laris), which communicates with the nasal fossa. The margins of this aperture 

 are thin and ragged, and the aperture itself in the articulated skull is much con- 



Bones partially dosing orifice of antrum 

 marked in outline. 



Ethmoid. 



Turbinated. 



Palate. 



Anterior nasal spine. 



Bristle passed 

 through anterior 

 palatine canal. 



FIG. 71. Left maxilla. Internal surface. 



tracted by its articulation with the ethmoid above, the turbinated bone below, 

 and the palate bone behind. 1 In the articulated skull this cavity communicates 

 with the middle meatus of the nasal cavity, generally by two small apertures 

 left between the above-mentioned bones. In the recent state usually only one 

 small opening exists, near the upper part of the cavity, sufficiently large to 

 admit the end of a probe, the other being closed by the lining membrane of 

 the sinus. 



Crossing the cavity of the antrum are often seen several projecting laminae of 

 bone, similar to those seen in the sinuses of the cranium; on its posterior wall are 

 the posterior dental canals, transmitting the posterior dental vessels and nerves to 

 the teeth. Projecting into the floor are several conical processes, corresponding 

 to the roots of the first and second molar teeth; in some cases the floor is perforated 

 by the teeth in this situation; projecting into the antrum from the roof is a ridge 

 corresponding to the infraorbital canal. 



1 In some cases, at any rate, the laerimal bone encroaches slightly on the anterior superior portion of the 

 opening, and assists in forming the inner wall of the antrum. 



