174 THE HEAD AND NECK 



(i) The buccinator (long buccaT) nerve supplies the posterior part 

 of the cheek, and (2) the mental nerve, which is the terminal 

 branch of the inferior alveolar, supplies the skin overlying the 

 body of the mandible. In severe neuralgia the mental nerve 

 can be exposed by an incision through the outer side of the gum 

 just beneath the lower premolars. The lower part of the wound 

 is retracted downwards, and the nerve is found as it leaves the 

 mental foramen. When the pain also affects the gums and 

 teeth the nerve is twisted out in order to destroy, if possible, 

 the inferior dental plexus within the canal. 



(3) The auriculo-temporal nerve supplies the skin in front of 

 the ear, and extends upwards to the vertex. In addition, it 

 supplies the skin of the upper part of the auricle and the integu- 

 ment which lines the external acoustic meatus and covers 

 the membrana tympani. On this account foreign bodies in 

 the meatus and chronic inflammatory conditions of its walls 

 commonly cause referred pain over the side of the head. 



The remainder of the auricle and the skin over the angle 

 of the mandible are supplied by the great auricular nerve (C. 2 

 and 3). 



Congenital cutaneous naevi on the face (" port wine stains ") 

 map out very accurately the areas supplied by one or more 

 divisions of the trigeminal. 



The External Maxillary (Facial) Artery (p. 122) crosses 

 the inferior border of the mandible just in front of the masseter 

 (i inches from the angle of the mandible), and its pulse can 

 readily be felt in that situation. It then runs upwards and 

 forwards over the bone and the buccinator to a point half an 

 inch lateral to the angle of the mouth, and from there to a point 

 a little behind the ala nasi. Thereafter it ascends to the medial 

 palpebral commissure (inner canthus), where it anastomoses 

 with the terminal branches of the ophthalmic artery. In this 

 situation, therefore, there is an anastomosis between the internal 

 and external carotid arteries. In the lower part of its course 

 the artery is covered by the platysma and the risorius, which 

 blend with one another in the lower part of the face. Near the 

 angle of the mouth it becomes quite superficial, but at a higher 

 level it is crossed by the zygomaticus and by the muscle which 

 elevates the upper lip. The course of the vessel is very tortuous, 

 so that it is not affected by the free movements of facial 

 expression. 



A free anastomosis occurs between the vessels of the two 



