SUBCLAVIAN ARTERIES. 



SUBCIAVIAN ARTERIES. 



The subclavian artery is only the commencing portion of a long trunk 

 which forms the main artery of the upper limb, and which is artificially 

 divided for purposes of description into three parts the subclavian, 

 axillary, and brachial arteries. 



The subclavian artery, arising on the right side from the extremity of the 

 innominate stem, and on the left from the arch of the aorta, passes a short 

 way up into the neck, arches outwards over the pleura, and rests between 

 the scalenus anticus and scalenus medius muscles on the first rib. At the 

 outer border of the first rib it ceases to be called subclavian, and is con- 

 tinued into the axillary artery. 



Each subclavian artery is conveniently divided into three parts, the 

 first part extending from the origin of the vessel to the inner border of the 

 anterior scalenus muscle ; the second consisting of the portion of the vessel 

 situated behind that muscle ; and the third reaching outwards to the external 

 border of the first rib. In examining each of these portions in detail, it 

 will be necessary in the first part to give separate descriptions for the right 

 and the left sides, as there is a material difference in the anatomy of the two 

 vessels. 



THE FIRST PART OF THE RIGHT SVJBCLAVIAN ARTERY Commences close to 



the trachea, at the division of the innominate artery, behind the upper part 

 of the sterno-clavicular articulation, and ends at the inner margin of the 

 anterior scalenus muscle. Separating from the carotid artery, it arches up- 

 wards and outwards, and ascends above the level of the clavicle to an extent 

 which varies in different cases. It is deeply placed, being covered by the 

 platysma, the stern o-mastoid, the sterno-hyoid, and sterno- thyroid muscles, 

 and the deep cervical fascia. It is in contact with the pleura iuferiorly, and 

 is separated by an interval from the longus colli muscle behind. 



Relation to Veins. The subclavian vein lies lower than the first part of 

 the right subclavian artery, close under the clavicle. In its course to join 

 this vein, the internal jugular passes in front of the artery near the scalenus 

 muscle, as do also, near the middle line, the anterior jugular and a vertebral 

 vein. 



Relation to Nerves. The vagus nerve passes in front of the artery on 

 the inner side of the internal jugular vein, and its recurrent laryngeal 

 branch, turning round below the artery, ascends behind. Some cardiac 

 branches of the sympathetic nerve pass down over the artery. 



THE FIRST PART OF THE LEFT SUBCLAVIAN ARTERY arises from the upper 

 surface of the arch of the aorta, at the left end of its transverse portion, 

 and ascends to the margin of the first rib, behind the insertion of the anterior 

 scalenus muscle. It is, therefore, longer than the first part of the right sub- 

 clavian, and ascends at first almost vertically out of the chest, instead of 

 arching, like that vessel, outwards across the neck. It is at first overlapped 

 by the left lung, and is covered in front and on the left side by the pleura ; 

 it rests on the longus colli muscle, and lies, for a short space, in front of 

 the oesophagus (here deviating to the left side), and the thoracic duct. To 

 the inner or right side of the vessel are situated the left carotid and trachea, 

 and further up the oesophagus and the thoracic duct. 



Relation to Veins. The internal jugular vein is immediately before the 

 artery, where it turns outwards from the thorax, close to the scalenus 

 muscle ; and the left innominate vein is likewise anterior to it. 



