THE FACE, MOUTH AND PHARYNX 



179 



The hypoglossal nerve is found in the anterior end of the 

 wound as it lies in the angular interval between the two bellies 

 of the digastric (p. 145). The incision is carried down through 

 the deep fascia till the posterior belly of the digastric and the 

 submaxillary gland are exposed. This part of the hypoglossal 

 nerve is chosen by the surgeon because a long segment is required 

 to minimise any strain on the subsequent anastomosis. Further, 

 the nerve is easily found in this part of its course, whereas, at a 

 higher level, it lies more deeply, and its isolation would involve 

 considerable risk of injury to the internal jugular vein. The 

 nerve is cut through and withdrawn from under cover of the 

 posterior belly of the digastric. This necessitates section of the 



Upper joint cavity 

 Discus articularis \ 

 Lower joint cavity \ 

 Capsule \ 



Tuberculum articulare 



Mastoid process 



Styloid process 



FIG. 53. Section through the Mandibular Joint. 



branch of supply to the thyreo-hyoid and, perhaps, of the ramus 

 descendens hypoglossi. The proximal extremity of the hypo- 

 glossal nerve is then turned up over the posterior belly of the 

 digastric and united to the distal portion of the facial nerve, 

 which is turned down to meet it. 



In similar cases the (spinal) accessory nerve may be united 

 to the facial. It is found .at the anterior border of the sterno- 

 mastoid (p. 135). 



Temporo-Mandibular Joint. At this joint the condyle of 

 the mandible articulates with the mandibular (glenoid) fossa 

 of the temporal bone, which is limited posteriorly by the tym- 

 panic plate and in front by the articular tubercle (eminentia 

 articularis). The capsule, which is loose and so permits of free 

 movement, is attached to the margins of the cartilage-covered 



