294 HEAD AND NECK 



THE GREAT VESSELS AND NERVES 

 OF THE NECK. 



As soon as the dissection of the infratemporal and the 

 submaxillary regions is completed the dissector should turn 

 to the study of the external carotid artery and its relations. 



Arteria Carotis Externa. The external carotid is one 

 of the two terminal branches of the common carotid. It 

 commences therefore at the level of the upper border of the 

 thyreoid cartilage, opposite the disc between the third and 

 fourth cervical vertebrae ; and, after running upwards and 

 posteriorly to the level of the neck of the mandible, it 

 terminates, between that portion of bone and the upper part 

 of the antero-medial surface of the parotid gland, by dividing 

 into two terminal branches, the superficial temporal and the 

 internal maxillary. At its commencement it lies anterior and 

 medial to the internal carotid ; and it is called external not 

 on account of its relation to the internal carotid, but because 

 it is distributed mainly to the parts on the exterior of the 

 skull. It is at first comparatively superficial in the upper 

 part of the carotid triangle ; next it passes under cover of the 

 lower part of the postero-medial surface of the parotid and the 

 posterior belly of the digastric and the stylo-hyoid muscles. 

 At the upper border of the stylo-hyoid it enters a groove in 

 the medial border of the parotid, through which it passes to 

 the upper part of the antero-medial surface of the gland, 

 posterior to the neck of the mandible, where it terminates. 



Relations. As it lies in the carotid triangle it is covered 

 by the skin, superficial fascia and platysma, branches of the 

 nervus cutaneus colli and the cervical branch of the facial 

 nerve, and the deep fascia. Beneath the deep fascia it is 

 crossed superficially by the common facial and lingual veins 

 and the hypoglossal nerve ; and, at the upper end of the 

 triangle, it is concealed by the lower end of the parotid gland 

 and it is crossed from behind forwards by the posterior facial 

 vein. After it leaves the carotid triangle it is overlapped by 

 the angle of the mandible, and is crossed by the posterior 

 belly of the digastric and the stylo-hyoid. At its termina- 

 tion it is concealed by the upper part of the parotid and is 

 crossed by branches of the facial nerve. 



