SUBCLAVIAN 



507 



layer of deep fascia, and by the scalenus anticus. The phrenic nerve — which, in 

 consequence of its oblique course downwards and inwards, crosses a i)ortion of 

 both the first and second part of the subclavian — is separated from the second 

 portion by the scalenus anticus muscle as is also the subclavian vein which courses 

 on a someAvhat lower plane. 



Behind the artery are the apex of the pleura and lung, and a i)ortion of the 

 scalenus medius; also the structure known as Sibson's fascia. 



Above is the brachial plexus. 



Below are the pleura and lung. 



One branch only — the superior intercostal — is, as a rule, given off from this 

 portion of the subclavian; occasionally the posterior scapular artery arises from it. 



THE THIRD PORTION OF THE SUBCLAVIAN ARTERY 



The third portion of the subclavian artery extends from the outer margin of 

 the scalenus anticus muscle, downwards and outwards to the outer border of the 



Fig. 341. — The RmHT Subclavian Artery. 



Scalenus medius 



Scalenus anticus and 



ou it phrenic nei-ve 



Traiisrerxt' ri nicul 



artery 



Suprascapular artery 



Siihclavian artery 



CORD OF BRA CHIA L 

 I'LEXVS, GfViyO 

 OFF .VrsCVLO- 

 CUTAXEOUS AXn 

 OUTER HEAD OF 

 MEDIAN NER VES 



Axillary artery 



MrSCVLO-SPIRAL 

 XER VE 



Thyroid axis 

 Internal jugular vein 



Right common carotid 



artery 

 rXEFMOGASTRIC 



XERVE 

 Coiionericement of 



iiiiioniinate vein 



.'Subscapular and two circumflex arteries 



first rib. It is more superficial than either the first or second portions; it is in rela- 

 tion with less important structures, and as a rule gives off no l)ranch, and for these 

 reasons is the part selected when practicable for the ap})lication of a ligature. It is 

 the longest of the three i)ortions of the sul tclavian artery, and lies in a triangle — the 

 subclavian triangle — lioundcd by the sterno-mastoid, the omo-hyoid. and the 

 clavicle. 



Relations. — In front it is covered by the skin, superficial fascia, platysma, cla- 

 vicular branches of the descending portion of the superficial cervical plexus of nerves; 

 anterior layer of deep fascia which descends from the omo-hyoid to the clavicle; 

 and the posterior layer of deep fascia which descends from the omo-hyoid to the 

 first rib and is prolonged inwards over the scalenus anticus and phrenic nerve. 

 Between the two lavers of fascia is a variable amount of cellular tissue and f:it, and 



