652 



DISSECTION OF THE ORBIT. 



and 



temporal 



offsets. 



Orbitalis 

 muscle. 



Dissection 

 in spheno- 

 maxillary 



; 



Superior 



maxillary 



nerve. 



in floor of 

 orbit. 



Infraorbital 

 vessels. 



SZB 



r max- 

 y nerve 



passes to 

 face 



through 



infraorbital 



canal. 



Its branches 

 are to 

 orbit ; 



to the nose 

 and palate ; 



to the 

 hinder teeth 

 and cheek ; 



The temporal branch ascends in a groove in the bone on the outer 

 wall of the orbit, and after being joined by a filament from the 

 lachrymal nerve, passes into the temporal fossa through the temporal 

 canal in the malar bone : it is then directed upwards between the 

 temporal muscle and the skull, and perforates the temporal fascia 

 near the orbit (p. 50-1). 



Orbitalis muscle. At the lower and outer angle of the orbit this 

 thin layer of unstriped muscle is sometimes well seen. The fibre 

 cross the spheno-maxillary fissure, being attached to the edges, and 

 are pierced by the temporo-malar nerve. 



Dissection. The contents of the orbit having now been removed, 

 with the exception of the temporo-malar nerve, which is to be 

 preserved if possible, the whole of the outer wall is to be cut 

 away and the greater wing of the sphenoid chipped away so as to 

 open up the spheno-maxillary fossa. Only an osseous ring should 

 be left round the superior maxillary division of the fifth nerve 

 where it issues from the skull through the foramen rotundum, and 

 the exposure of the nerve as it crosses the fossa to pass on to the 

 floor of the orbit will be completed by removing the fat. In the 

 fossa the student seeks the following offsets, the orbital branch 

 entering the cavity of the orbit, branches to Meckel's ganglion which 

 descend in the fossa, and the posterior dental branch along the back 

 of the upper jaw. 



To follow onwards the nerve in the floor of the orbit, the contents 

 of the cavity having been taken away, the bony canal in which it 

 lies must be opened to its termination on the face. From the 

 infraorbital canal the anterior and middle dental branches are to 

 be traced downwards for some distance in the bone. The infra- 

 orbital vessels are prepared with the nerve. 



The SUPERIOR MAXILLARY NERVE (fig. 231) commences at the 

 Gasserian ganglion, and leaves the cranium by the foramen rotun- 

 dum. The course of the nerve is almost straight to the face, across 

 the spheno-maxillary fossa, and along the orbital plate of the upper 

 maxilla through the infraorbital canal. Issuing from the canal by 

 the infraorbital foramen, where it is concealed by the elevator of the 

 upper lip, it ends in infraorbital or facial branches which radiate to 

 the eyelid, nose, and upper lip. 



After the nerve comes to lie on the floor of the orbit it is called 



the INFRAORBITAL NERVE. 



BRANCHES. a. The orbital or temporo-malar branch ( 4 ) has already 

 been described. 



b. The spheno -palatine branches ( 3 ) descend from the nerve in 

 the fossa, and supply the nose and the palate ; they are con- 

 nected with Meckel's ganglion, and will be dissected with it 

 (SECTION XIII., p. G73). 



c. The posterior dental branch ( 5 ) leaves the nerve near the upper 

 jaw. It enters a canal in the maxilla, and supplies branches to 

 the molar teeth and the lining membrane of the antrum ; near the 

 teeth it joins the middle dental nerve. Before entering the canal 



