NERVUS MAXILLARIS 303 



aspect of the body of the maxilla. They contribute a few 

 fine filaments to the mucous membrane of the cheek and 

 to the gum, and then disappear* into the minute" posterior 

 alveolar foramina to supply the three molar teeth and the lining 

 membrane of the maxillary sinus. 



The middle superior alveolar nerve supplies the two 

 premolar teeth. It arises from the infra-orbital nerve, and 

 can be easily detected (if present as a separate branch) when 

 the parent trunk is gently raised from the floor of the infra- 

 orbital canal. It descends in a minute canal which traverses 

 the lateral wall of the maxillary sinus. 



The anterior superior alveolar nerve, much the largest of 

 the three alveolar branches, springs from the infra-orbital as it 

 approaches the anterior part of the canal. To bring it into 

 view raise the parent trunk from the floor of the canal, and 

 the branch will then be seen to enter a special bony tunnel 

 which traverses the maxilla in the anterior wall of the 

 maxillary sinus. The dissector should endeavour to open 

 up that canal with the chisel. After supplying a branch to 

 the mucous membrane of the lower and anterior part of 

 the nasal cavity, the anterior superior alveolar nerve divides 

 into branches for the incisor and the canine teeth. 



While traversing the maxilla, the three superior alveolar 

 branches communicate with one another, and form two 

 nerve loops (Fig. 113). Numerous twigs proceed from both 

 loops, and they communicate with one another to form a 

 fine plexus. It is from that plexus that the terminal fila- 

 ments to the teeth and gums take origin. 



Arteria Infraorbitalis. The infra - orbital artery is a 

 branch of the internal maxillary. It arises in the pterygo- 

 palatine fossa and accompanies the infra-orbital nerve. In 

 the face its terminal twigs anastomose with branches of the 

 external maxillary, transverse facial, and buccinator arteries ; 

 in the infra-orbital canal it gives some fine branches to the 

 contents of the orbital cavity, and also the anterior superior 

 alveolar artery which accompanies the nerve of that name, 

 and supplies the incisor and canine teeth, and the lining 

 membrane of the maxillary sinus. 



The infra-orbital vein joins the pterygoid plexus. 



