228 



The Subclavian Artery 



THE SUBCLAVIAN ARTERY 



On the left side the subclavian arises from the left end of me 

 transverse part of the aortic arch, a little to the left of and behind the 

 left common carotid. Thence it ascends through the superior medias- 

 tinum (p. 154), and, arching over the apex of the pleura, passes behind 

 the scalenus anticus, just as it does on the right side. 



Relations of the first part of the left subclavian. It is much 

 longer and more vertical than that of the right. It has in front the 

 manubrium with the origin of the sterno-mastoid, and sterno-hyoid 

 and thyroid, a little of the left lung and pleura intervening. As the 

 artery ascends a little posterior to the left carotid the internal jugular 

 vein and vagus, descending along the outer side of the thoracic part of 

 the carotid, are on an anterior plane to the subclavian. The vertebral 

 and the subclavian vein, the beginning of the left innominate vein, 

 and the phrenic nerve, which has slipped down from the front of the 

 anterior scalene, are also in front. 



Behind are the oesophagus and thoracic duct, and the longus colli. 

 The left carotid and the trachea are to the right side ; and as the 

 subclavian ascends it has the oesophagus also to the right. Because the 

 thoracic duct hooks forwards to the confluence of the jugular and sub- 

 clavian veins it lies close on the inner side of the artery. 

 The lung and pleura are to the outer side. 



As already remarked (p. 184), aneurysm of the innominate artery is 

 of common occurrence, because that vessel receives much of the shock 

 of the contraction of the left ventricle ; on the other hand, dilata- 

 tion of the first part of the 

 subclavian is very rare. 



The right subclavian 

 artery springs from the 

 innominate, behind the 

 sterno-clavicular joint, and 

 runs outwards and a little 

 upwards to the inner border 

 of the scalenus anticus, 

 where the second part 

 begins. It courses (first 

 part) above the level of the 

 clavicle, and, being some- 

 what horizontal, its rela- 

 tions are anterior, posterior, 



I'lan of branches of right subclavian artery. (GRAY.) . . . _ . 



superior, and inferior. 



In front are the sterno-mastoid, sterno-hyoid, and sterno-thyroid ; 

 the internal jugular and vertebral veins, the pneumogastric and 

 phrenic nerves, and cardiac branches of the sympathetic. 



