532 



THE BLOOD-VASCULAR SYSTEM 



Below it — that is, in its concavity — are the bifurcation of the pulmonary artery, the left 

 bronchus, the left recurrent (inferior laryngeal) nerve, the ligamentum arteriosum, the super- 

 ficial cardiac plexus, two or more bronchial lymphatic glands, and the reflexion of the 

 pericardium. 



The branches of the aortic arch are: — the innominate, the left common caro- 

 tid, and the left subclavian arteries. The innominate and left carotid arise close 

 together — indeed, so close that, when seen from the interior of the aorta, the 

 orifices appear merely separated by a thin septum. The left subclavian arises a 

 little less close to the left carotid. 



THE INNOMINATE ARTERY 



The innominate [a. anonyma] or brachio-cephalic artery (fig. 441), the largest 

 branch of the arch of the aorta, extends from near its commencement upward 

 and a little forward and to the right, as high as the upper limit of the right 

 sterno-clavicular joint where it bifurcates into the right common carotid and right 

 subclavian arteries. It lies obliquely in front of the trachea, and measures from 

 3.7 to 5 cm. (1| to 2 in.). 



Fig. 443. — The Thyreoidea Ima. (After Henle.) 



Right carotid artery 

 Right subclavian artery 



Innominate artery 

 Superior vena cava 



Left carotid artery 



Left subclavian artery 



) 



Pulmonary artery 



Relations. — In front f)f the artery are the manubrium, the origins of the sterno-hyoid and 

 sterno-thyreoid muscles, the right sterno-clavicular joint, and the remains of the thymus gland. 

 The left innominate vein crosses the root of the vessel, and the inferior thyreoid and thyreoidea 

 ima veins descend obliquely over it to end in the left innominate vein. The inferior cervical 

 cardiac branches of the right vagus nerve pass in front of it on their way to the deep cardiac 

 plexus. 



Behind, it lies on the trachea, crossing that tube obliquely from left to right, and coming 

 into contact above with the right pleura. 



To the right side are the riglit innominate vein, the right vagus, and the pleura. 



To the left side are the left common carotid, the remains of the thymus gland, the right 

 inferior thyreoid vein; and, liighcr, the trachea. 



The branches of the innominate artery are: — (1) The right common carotid; 

 and (2) the right subclavian. These arc terminal branches. There are usually 

 no collateral brandies from this vessel, but at times the thyreoidea ima may arise 

 from it. 



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