THE ARTERIES 



633 



The Arteries 



There is no common brachiocephalic trunk (anterior aorta) . Two large ves- 

 sels arise from the convexity of the aortic arch; these are the brachiocephalic and 

 left brachial arteries. The brachiocephalic gives off the two carotid arteries, no 

 common trunk being present. It frequently also supplies the posterior thyroid 

 artery. Tlu^ intrathoracic branches of the brachial arteries are as follows: 



A common trunk gives off the dorsal, subcostal, and superior cervical arteries. 

 The dorsal artery passes out in front of the first rib, and the superior cervical 

 through the first intercostal space. The latter is relatively small. 



The vertebral artery may arise either in front of or behind tlie trunk above 

 mentioned; in the latter case it crosses the inner face of the trunk. It passes along 



Fig. 485. — Arteries of Thoracic Cavity and Part of Neck of Dog. 

 a. Aortic arch; a', thoracic aorta; 6, brachiocephalic artery; c, left brachial artery; d, rf, common carotid 

 arteries; e, vertebral artery; /, dorsal artery; g, deep or superior cervical artery (usually given off from a com- 

 mon trunk with /); h, extrathoracic part of /; i, subcostal artery; k, inferior cervical artery; /, descending 

 branch of k; m, ascending branch of k; n, internal scapular; o, acromial; p, superficial cervical; q, s, extrathoracic 

 part of left brachial; r, external thoracic; /, internal thoracic; t' , asternal; t", anterior abdominal; ii, perforating 

 branch of t; f, anterior mediastinal (thymic) ; w, ventral intercostals; a-, bronchial; 2/, ccsophageal; 2/', dorsal 

 intercostals; z, descendmg branch of left coronary artery; z' , circumflex branch of same; /, oesophagus; 2, 

 trachea; 2', bronchi; 3, first rib (sawn off); 4, right ventricle; 5, left ventricle; 5', left auricle; 5", pulmonary 

 artery (cut off); ff, diaphragm; 7, S, 9, last three cervical vertebrcc; 10, thymus. (After Ellenberger, in 

 Leisenng's Atlas.) 



the neck in typical fashion to the third cervical vertebra and divides into three 

 branches. Tht^ largest of tliese supplies the muscles in this region, compensating 

 for the absence of branches of the superior cervical artery. The second passes 

 between the second and third cervical vertebrae into the vertebral canal and unites 

 with the opposite artery and a branch of the occipital artery to form the basilar. 

 The third branch is the small continuation of the parent trunk; it passes to the 

 wing of the atlas and anastomoses with the occipital. 



The inferior cervical artery gives off the superficial cervical which ascends in 

 front of the suj)raspinatus. 



The internal thoracic artery is large and sends perforating branches to the 

 pectoral mammary glands. 



