158 



OSTEOLOGY 





boundaries of three cavities, viz., the roof of the mouth, the floor and lateral 

 wall of the nose and the floor of the orbit; it also enters into the formation of two 

 fossse, the infratemporal and pterygopalatine, and two fissures, the inferior orbital 

 and pterygomaxillary. 



Each bone consists of a body and four processes zygomatic, frontal, alveolar, 

 and palatine. 



The Body (corpus maxilloe). The body is somewhat pyramidal in shape, and 

 contains a large cavity, the maxillary sinus (antrum of Highmore). It has four 

 surfaces an anterior, a posterior or infratemporal, a superior or orbital, and. a 

 medial or nasal. 



Surfaces. The anterior surface (Fig. 157) is directed forward and lateralward. 

 It presents at its lower part a series of eminences corresponding to the positions 

 of the roots of the teeth. Just above those of the incisor teeth is a depression, 

 the incisive fossa, which gives origin to the Depressor alse nasi; to the alveolar 

 border below the fossa is attached a slip of the Orbicularis oris; above and a little 



Med. palp, lig 



DILATATOR NARIS POSTERIOR 



Incisive fossa 



'Alveolar canals 



Maxillary tuberosity 



Premolars 

 Fio. 157. Left maxilla. 



Outer surface. 



lateral to it, the Nasalis arises. Lateral to the incisive fossa is another depression, 

 the canine fossa; it is larger and deeper than the incisive fossa, and is separated 

 from it by a vertical ridge, the canine eminence, corresponding to the socket of 

 the canine tooth; the canine fossa gives origin to the Caninus. Above the fossa 

 is the infraorbital foramen, the end of the infraorbital canal; it transmits the infra- 

 orbital vessels and nerve. Above the foramen is the margin of the orbit, which 

 affords attachment to part of the Quadratus labii superioris. Medially, the anterior 

 surface is limited by a deep concavity, the nasal notch, the margin of which gives 

 attachment to the Dilatator naris posterior and ends below in a pointed process, 

 which with its fellow of the opposite side forms the anterior nasal spine. 



The infratemporal surface (Fig. 157) is convex^ directed backward and lateral- 

 ward, and forms part of the infratemporal fossa. It is separated from the anterior 

 surface by the zygomatic process and by a strong ridge, extending upward from 

 the socket of the first molar tooth. It is pierced about its center by the apertures 

 of the alveolar canals, which transmit the posterior superior alveolar vessels and 

 nerves. At the lower part of this surface is a rounded eminence, the maxillary 



