134 



EXTERNAL CAROTID. 



tious vessels of the arteries are called vasa vasorum,^ and their 

 nerves are derived from the sympathetic. 



AORTA. 



The aorta arises from the lefl; ventricle, and arches backwards 

 and towards the left side. This arch^ ^ frequently has an enlarge- 

 ment, which is called its sinus ; under it passes the right branch of 

 the pulmonary artery. — The descending aorta^ while passing through 

 the thorax is termed thoracic^ and while passing through the abdo- 

 men, abdominal. 



The coronary arteries are the first branches of the aorta, and are 

 distributed to the heart, through the grooves between the auricles 

 and ventricles. They arise just beyond the semilunar valves. 



The Inriominata* This artery arises from the arch of the aorta, 

 is an inch and a half in length, ascends obliquely towards the right 

 side in front of the trachea, and behind the sterno-clavicular articula- 

 tion, divides into the right carotid and right subclavian. (Fig. 115.) 

 The right carotid^ ascends the neck as far nearly as the hyoid 

 bone, where it divides into the external and internal carotids. 



The left carotid}^ ari- 

 Fig. 116. ses from the arch of the 



aorta, ascends the neck 

 and divides as the right. 

 Each primitive carotid is 

 on the inner side of the in- 

 ternal jugular vein, with 

 which and the par va- 

 gum nerve it is included 

 in a sheath. (Fig. 115.) 



EXTERNAL CAROTID. 



It ascends perpendi- 

 cularly from the bifurca- 

 tion, an d passing through 

 the deep portion of the 

 parotid gland it divides 

 into the internal maxil- 

 lary'^ and temporal.^^ 



Superior thyroid^^ 

 arises near the root of the 

 external carotid and is its 

 first branch ; it pursues a 

 curved course and is dis- 

 tributed to the thyroid 

 gland, after giving off' a laryngeal branch. (Fig. 116.) 



