250 



THE VASCULAR SYSTEMS 



divides into two primary branches, the right vessel running in 

 the posterior and the left in the anterior, interventricular, and 

 auriculo ventricular grooves. 



The innominate (brachiocephalic) artery is the largest branch. 

 It arises in front of the left carotid, and runs obliquely to the 

 right sternoclavicular joint, where it divides into the right 

 common carotid and right subclavian. 



FIG. 40 



Vein azygos major. 

 Rigid 

 pulmonary veins, j 



Right ' 

 innom. vein. 



Rigid subclav. / 

 Right common carotid. 



Left subclav. 



Inferior thyroid. \ 



T .. f . . Left common carotid. 



Left innominate rein. 



Relation of great vessels at base of heart, seen from above. (From a preparation 

 in the Museum of the Royal College of Surgeons of England.) 



Relations. In front, manubriumsterni, sternohyoid and thyroid 

 muscles, thymic remains, left innominate and right inferior 

 thyroid veins, inferior cervical cardiac nerve from the right 

 vagus; behind, trachea and pleura; right sidc^ pleura, right 

 vagus, right phrenic nerve, and the right innominate vein; left 

 side, remains of the thymus and trachea. The left carotid 

 artery as it leaves the arch is behind and to the left of this vessel. 

 The innominate regularly gives off no branches. Occasionally, 



