284 



THE CIRCULATORY SYSTEM. 



then passes to about the level of the larynx without giving off 

 branches; here it gives off the superior thyroid (r) on the 

 ventral side and one or more muscular branches (e) on the 

 dorsal side. One or two centimeters further craniad it gives.,, 

 oft on the dorsal side the internal carotid {g) and the occipital 

 artery {/). The main artery now takes the name external 

 carotid (w). 



Branches of the common carotid: 



Fig. 119. — Common Carotid Artery and Intern /vi. Jugular Vein. 

 a, common carotid artery; b, internal jugular vein; c, superior thyroid artery; d, 

 cervicalis ascendens artery; e, lary;e muscular branches; J, occijiital artery; g, in- 

 ternal carotid; h, branch to larynx; /', lingual artery;/, external maxillary; /', sujie- 

 rior labial; /, inferior labial; vi, external carotid; n, internal maxillary; o, posterior 

 auricular; /, superficial temporal. I, M. sternohyoideus; 2, M. sternothyreoideus; 

 3, M. geniohyoideus; 4, M. genioglossus; 5, M. constrictor pharyngis medius; 6, M. 

 constrictor ])liaryngis inferior; 7, M. longus capitis; 8, M. digastricus; 9, M. mas- 

 seter; 10, M. scalenus; II, M. levator scapulce (cut); 12, M. levator scapulae ven- 

 tralis (cut); 13, M. splenius; 14, trachea. 



1. A. thyreoidea ima. — The inferior thyroid is a small 

 artery which arises either from the common carotid near its 

 origin, or from the innominate before the origin of the carotid. 

 It passes craniad on the trachea as far as the thyroid gland, 

 giving branches to the trachea and cesophagus. 



2. A. thyreoidea superior (r). — The superior thyroid leaves 

 the carotid opposite the thyroid cartilage and passes mediad 

 and caudad, sending branches to the thyroid gland, and the 



