202 HEAD AND NECK 



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. 



To its medial side lies the wall of the pharynx with the 

 external and internal laryngeal branches of the superior 

 laryngeal nerve intervening in the region of the carotid 

 triangle. The medial relations, at a higher level, will be 

 seen to greater advantage at a later stage, when the styloid 

 process is detached and displaced. They are the pharyngeal 

 branch of the vagus, the stylo-pharyngeus, the glosso-pharyngeal 

 nerve, and the styloid process or the stylo-hyoid ligament. 

 Those structures lie to its medial side as they pass obliquely 

 between it and the internal carotid, which has gradually 

 attained a plane posterior and medial to that in which the 

 external carotid lies. 



In the whole of its extent the external carotid is accom- 

 panied by numerous sympathetic nerve fibres,, derived from 

 the upper cervical sympathetic ganglion ; they constitute the 

 external carotid plexus, which distributes offsets along all the 

 branches of the artery. 



Branches. The branches of the external carotid artery are 

 the superior thyreoid, the lingual, and the external maxillary, 

 from its anterior aspect ; the occipital and the posterior 

 auricular, from its posterior aspect ; the ascending pharyngeal, 

 from its medial side ; and the superficial temporal and the 

 internal maxillary are its terminal branches. 



Arteria Thyreoidea Superior. The superior thyreoid 

 artery arises, within the carotid triangle, from the anterior 

 aspect of the external carotid close to its origin. It runs 

 downwards and forwards, under cover of the omo-hyoid, 

 sterno-hyoid, and sterno-thyreoid muscles, to the apex of the 

 corresponding lobe of the thyreoid gland, where it ends by 

 breaking up into three terminal branches. 



The following branches proceed from it : 



Hyoid. 

 2. Superior laryngeal. 



4. Crico-thyreoid. 



5. Terminal glandular. 



3. Sterno-mastoid. 



Ramus Hyoideus. The hyoid branch is a small twig, which 

 springs from the superior thyreoid in the carotid triangle. 

 It runs along the lower border of the hyoid bone, under cover 

 of the thyreo-hyoid muscle, and anastomoses with its fellow 



