Skull and Hyoid 229 



complete canal or foramen by the lachrymal bone, and this bone articulates with the 

 maxilla along the posterior border of the notch as well as along the nasal process. 



The facial surface (Fig 184) of the body, antero-external, is rather concave from 

 the presence of the malar process and the canine fossa, above which, and about one- 

 third of an inch below the orbital margin, is the anterior opening (infraorbital foramen) 

 of the infraorbital canal. The surface is directly continuous below with that of the 

 alveolar process, which presents ridges and depressions corresponding with the position 

 of the fangs of the teeth : the front surface of the body is bounded internally by the 

 sharp margin of the nasal opening, but the alveolus is continued below this to the middle 

 line to meet its fellow and to carry the incisors, and it presents here an anterior concavity, 

 the incisive or myrtiform fossa. This part of the alveolus, frequently termed the 

 premaxilla, is continuous behind with the palatine process, and is limited above by the 

 lower margin of the nasal orifice, which is produced centrally into a nasal spine. The 

 incisive slip of the Orbicularis oris takes origin from the incisive fossa. 



The facial surface is covered in its upper part by fibres of Orbicularis palpebrarum, 

 over the alveolar portion by mucous membrane and Orbicularis oris and Buccinator, 

 and between these two areas by small facial muscles passing to the upper lip : the 

 Levator anguli oris arises below the foramen, and the Levator labii superioris above 

 the foramen, both under cover of the orbicular fibres of the lower lid ; while the Levator 

 anguli oris alaeque nasi and Compressor naris take origin further in near the root of the 

 nasal process. 



The posterior or postero-external surface (Fig. 184) is separated from the one last 

 described by the prominent lower border of the projection that supports the malar, 

 but the alveolar process is carried continuously to the back of the bone below this 

 projection and affords origin to Buccinator. The posterior surface is rounded and forms 

 the front wall of the fossa that lies deep to the zygoma and below the inferior temporal 

 crest and outside the outer pterygoid plate : the fossa is termed the zygomatic or 

 infratemporal, and is occupied by the External Pterygoid and, superficial to this, by the 

 tendon of the Temporal muscle and the coronoid process of the mandible which receives 

 this tendon. The inner part of the posterior surface, however, is in front of the ptery- 

 goid region of the sphenoid, and therefore constitutes the front wall of the spheno- 

 maxillary fossa. This fossa is closed below by the tuberosity of the palate bone fitting 

 in between the maxilla and the pterygoid plates, so that a rough area for this tuberosity 

 is visible on the lower and inner part of the posterior surface of the maxilla. The 

 tuberosity of the palate is always completely interposed between the two bones, and the 

 maxilla never articulates here with the sphenoid, although the suture lines between 

 the various elements are not as a rule visible on the complete skull. Impressions made 

 on the bone by certain of the structures leaving the fossa can be easily seen : thus, the 

 posterior dental and alveolar vessels and nerves reach foramina on the back aspect of the 

 bone, the commencement of the infraorbital groove is seen above, and the posterior 

 palatine groove, completed by the palate bone, is apparent low down on the back and 

 inner aspect of the body in front of the area for the tuberosity of the palate. 



The upper margin of the posterior surface corresponds with the posterior 

 margin of the orbital surface and thus forms the lower boundary of the spheno- 

 maxillary fissure, which therefore opens from the orbit into the zygomatic fossa 

 in its outer part but into the spheno-maxillary fossa in its inner part : the 

 spheno-maxillary fossa can be looked on as an inward extension, behind the jaw, of 

 the zygomatic fossa. 



The rounded part of the posterior surface is sometimes referred to as the " tubero- 

 sity " of the maxilla. 



