THE SUBCLAVIAN ARTERY. :,! 



md gives off the deep cervical branch : a small spinal artery fre- 

 quently comes from this part of the trunk. On the left side the 

 irigin of this vessel is usually from the first part of the artery, a 

 ittle internal to the scaleuus anticus. 



If there is a branch present on the third part of the artery, and third 

 t is commonly the posterior scapular : if more than one, the part 

 nternal mammary, the stiprascapular, or the thyroid axis may 

 >e added. 



The LEFT SUBCLAVIAN ARTERY arises from the arch of the aorta, Left 

 nsteud of from an innominate trunk, and ascends thence over the 



irst rib in its course to the upper limb. With this difference on differs much 



two sides in the origin of the suljclavian the one vessel gubclavUn 

 leginning opposite the sterno-clavicular articulation, the other in 

 he thorax it is evident that the length and relations of the part 

 )f the artery on the inner side of the scalenus anticus must also 

 Lifter on the two sides. 



First part. The part of the artery internal to the anterior scalenus in the first 

 s much longer on the left than on the right side. It ascends nearly part : 

 -ertically from its origin to the level of the first rib, and then bends 

 omewhat abruptly outwards over the top of the lung. On leaving 

 he chest it is deeply placed in the neck, near the spine and the 

 i-sophagus, and does not rise usually so high above the first rib as 

 he right subclavian. 



Between the artery and the surface are structures like those on relations to 

 he right side, viz., the integuments with the platysma and deep 

 fascia, and the steriio-mastoid, hyoicl, and thyroid muscles. To the 

 inner side are the oesophagus and the thoracic duct, the latter 

 arching forwards above this part of the artery ; and the pleura is in 

 contact with the outer and posterior surfaces. Its relations lower 

 in the chest are described in the dissection of the thorax (p. 468). 



Veins. The internal jugular and vertebral veins, as well as the veins ; 

 jeginning of the innominate, are in front of this part of the artery. 



Xerves. The pneumo-gastric nerve lies parallel to the vessel position of 

 instead of across it as on the right side ; and the phrenic nerve ne 

 crosses over it close to the scalenus. Accompanying the artery are 

 ;he cardiac branches of the sympathetic, which course along its 

 inner side to the chest. 



The second and third parts of the artery and its branches are Rest of 

 essentially the same as on the right side. 



BRANCHES OF THE SCBCL AVIAN. 1. The vertebral artery is Vertebral 

 generally the first and largest branch of the subclavian, and arises ne ^ y m 

 Torn the upper and posterior part of the trunk. Ascending between 

 the contiguous borders of the scalenus anticus and longus colli 

 muscles, this branch enters the foramen in the transverse process of 

 :he sixth cervical vertebra, and is continued upwards to the skull 

 through the foramina in the other cervical vertebrae. Before the 

 artery enters its aperture it lies behind the internal jugular vein, and 

 is crossed by the inferior thyroid artery (fig. 2 1 3). It is accompanied 

 by branches of the sympathetic nerve, and supplies small muscular 

 offsets. Its farther course and distribution will be given afterwards. 



D.A. Q Q 



