306 HEAD AND NECK 



the stylo-pharyngeus, and the styloid process, which separate 

 it from the postero-medial surface of the parotid gland. It 

 will be noted also that three nerves and two arteries cross the 

 vessel superficially, viz. : 



1. The occipital artery. 



2. The posterior auricular artery. 



1. The hypoglossal nerve. 



2. The glosso-pharyngeal nerve. 



3. The pharyngeal branch of the 



vagus nerve. j 



The hypoglossal, as already noted, crosses it in the carotid 

 triangle ; the other nerves cross it under cover of the posterior 



Thyreo-hyoid membrane Sterno-hycid 



PHCa Thyreo-hyoid 



Processus vocahs x ^ Thyreoid cartilage 



Arytaeno.d cartilage 



Platvsna 



Scalenus anterior \ Sympathetic trunk 



Longus colli Vertebral artery 



FIG. 123. Transverse section through the Neck at the level of upper 

 part of Thyreoid Cartilage. 



belly of the digastric. The occipital artery crosses it at the 

 level of the lower border of the posterior belly of the digastric, 

 and the posterior auricular at the level of its upper border. 



The relationship of the external carotid artery to the 

 internal carotid is a varying one. At first the external 

 carotid lies antero-medial to it ; but soon, owing to its in- 

 clination posteriorly, it comes to lie directly superficial to the 

 internal carotid. The following structures intervene between 

 the two vessels : 



1. Styloid process. 



2. Stylo-pharyngeus muscle. 



3. Glosso-pharyngeal nerve. 



4. Tharyngeal branches of vagus 



and sympathetic. 



5. A portion of the parotid gland. 



Posterior to the internal carotid is the longus capitis (O.T. 

 rectus capitis anticus major) and the sympathetic trunk ; 

 postero-laterally are the glosso-pharyngeal, the vagus, the 

 accessory and the hypoglossal nerve ; and still more laterally 



