474 



THE ARTERIES 



the otlier vessel is tlien correspondingly small, (e) An extra coronary artery may arise from the 

 pulmonary artery. 



II. From tlie transverse part of the aortic arch are given off the innominate, 

 the left common carotid, and the left subclavian arteries. The innominate and 

 left carotid arise close together — indeed, so close that, when seen fr(^m 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 or brachio-cephalic artery (fig. 321), the largest branch of 

 the arch of the aorta, extends from near the commencement of the transverse por- 



FiG. 327. — Scheme of the Relations of the Innominate Artery. ("Walsham.) 



I, a little above origin ; II, a little below bifurcation. 



I 



CARDIAC NERVE 



RIGHT PyEVMO- 



GASTRIC SERVE 



Innominate artery 



RIGHT LUNG AND PLEURA 



Rir/ht innominate vein, 

 divided transversely 

 at its junctio7i with 

 the left innominate 

 vein 



Left common carotid artery 



Inferior thyroid vein 

 Inferior thyroid vein 

 Left innominate vein 



n 



RIGHT LUNG AND PLEURA 



RIGHT PNEUMO- 



GASTRIC NERVE 



Right innominate vein 



Innominate artery 



CARDIAC NERVES 



Left common carotid artery 

 Inferior thyroid vein 



Right sterno-hyoid and 

 Right sterno-thyroid muscles 



tion, upwards and a little forwards 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 an inch and a half to two inches in length (about 4 cm.). 



Relations. — In front of the artery (fig. 327) are the manultrium, the origins 

 of the sterno-hyoid and sterno-thyroid 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 thyroid veins descend obliquely over it to end in the 

 left innominate vein. The inferior cervical cardiac branches of the right pneumo- 

 gastric pass in front of it on their way to the deep cardiac plexus. 



Behind, it lies on the trachea, cx'ossing that tube obliquely from left to riglit, 

 and coming into contact al)Ove with the right pleura. 



To the right side are the right innominate vein, the right pneumogastric nerve, 

 and the pleura. 



