516 THE BLOOD-VASCULAR SYSTEM. 



Beneath. 

 Pleura. 



Recurrent laryngeal nerve. 



/ 



Behind. 



Recurrent laryngeal nerve. 



Sympathetic. 



Pleura and apex of lung. 



FIRST PART OF THE LEFT SUBCLAVIAN ARTERY (Fig. 280). 



The left subclavian artery arises from the end of the arch of the aorta, 

 opposite the fourth dorsal vertebra, and ascends nearly vertically to the inner 

 margin of the Scalenus anticus muscle. This part of the vessel is, therefore, 

 longer than the right, situated deeply in the cavity of the chest, and directed 

 nearly vertically upward, instead of arching outward like the vessel of the 

 opposite side. 



It is in relation, in front, with the pneumogastric, cardiac, and phrenic nerves, 

 which lie parallel with it, the left carotid artery, left internal jugular and vertebral 

 veins, and the commencement of the left innominate vein, and is covered by the 

 Sterno-thyroid, Sterno-hyoid, and Sterno-mastoid muscles ; behind, it is in relation 

 with the oesophagus, thoracic duct, inferior cervical ganglion of the sympathetic, 

 and Longus colli ; higher up, however, the oesophagus and thoracic duct lie to its 

 right side ; the latter ultimately arching over the vessel to join the angle of union 

 between the subclavian and" internal jugular veins. To its inner side are the 

 oesophagus, trachea, and thoracic duct; to its outer side, the left pleura and lung. 



PLAN OF RELATIONS OF FIRST PORTION OF LEFT SUBCLAVIAN ARTERY. 



In front. 



Pneumogastric, cardiac, and phrenic nerves. 

 Left carotid artery. 

 Thoracic duct. 



Left internal jugular, vertebral, and innominate veins. 

 Sterno-thyroid, Sterno-hyoid, and Sterno-mastoid muscles. 



Inner side. / \ 



TraoVipfl ^ eft - I Outer side. 



JLTacnea. Subclavian 



(Esophagus. I Artery. I Pleura and left lung. 



Thoracic duct. \ / 



Behind. 



(Esophagus and thoracic duct. 

 Inferior cervical ganglion of sympathetic. 

 Longus colli. 



SECOND AND THIRD PARTS OF THE SUBCLAVIAN ARTERY (Figs. 283, 298). 



The Second Portion of the Subclavian Artery lies behind the Scalenus anticus 

 muscle; it is very short, and forms the highest part of the arch described by that 

 vessel. 



Relations. It is covered, in front, by the skin, superficial fascia, Platysma, 

 deep cervical fascia, Sterno-mastoid, and the Scalenus anticus muscle. On the 

 right side the phrenic nerve is separated from the second part of the artery by the 

 Anterior scalene muscle, while on the left side the nerve crosses the first part of 

 the artery immediately to the inner edge of the muscle. Behind, it is in relation 

 with the pleura and the Middle scalene. Above, Avith the brachial plexus of 

 nerves. Beloiv, with the pleura. The subclavian vein lies below and in front of 

 the artery, separated from it by the Scalenus anticus. 



