470 ARTERIES. 



SECOND AND THIRD PARTS OF THE STJBCLAVIAN ARTERY. (Fig. 274.) 



The second portion of the subclavian artery lies behind the Scalenus Anti- 

 cus 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 integument, Platysma, Sterno-mas- 

 toid, cervical fascia, and by the phrenic nerve, which is separated from the 

 artery by the Scalenus Anticus muscle. Behind, it is in relation with the Middle 

 Scalenus. Above, with the brachial plexus of nerves. Below, with the pleura. 

 The subclavian vein lies below and in front of the artery, separated from it by 

 the Scalenus Anticus. 



PLAN OF RELATIONS OF SECOND PORTION OF SUBCLAVIAN ARTERY. 



In front. 



Scalenus Anticus. 

 Phrenic nerve. 

 Subclavian vein. 



-,-. , 

 BflOW. 



Brachial Plexus. I Second portion.) Pleura. 



lick ind. 

 Pleura and Middle Scalenus. 



The third portion of the subclavian artery passes downwards and outwards 

 from the outer margin of the Scalenus Anticus to the lower border of the first 

 rib, where it becomes the axillary artery. This portion of the vessel is the 

 most superficial, and is contained in a triangular space, the base of which is 

 formed in front by the Anterior Scalenus, and the two sides by the Omo-hyoid 

 above and the clavicle below. 



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

 the platysma, deep fascia ; and by the clavicle, the Subclavius muscle, and the 

 suprascapular artery and vein; the clavicular descending branches of the cer- 

 vical plexus and the nerve to the Subclavius pass vertically downwards in front 

 of the artery. The external jugular vein crosses it at its inner side, and receives 

 the suprascapular and transverse cervical veins, which occasionally form a 

 plexus in front of it. The subclavian vein is below the artery, lying close 

 behind the clavicle. Behind, it lies on the Middle Scalenus muscle. Above it, 

 and to its outer side, is the brachial plexus, and Omo-hyoid muscle. Below, it 

 rests on the outer surface of the first rib. 



PLAN OF RELATIONS OF THIRD PORTION OF SUBCLAVIAN ARTERY. 



In front. 

 Cervical fascia. 



External jugular, suprascapular, and transverse cervical veins. 

 Descending branches of cervical plexus. 

 Subclavius muscle, suprascapular artery, and clavicle. 



Above. ( Subclavian \ Selov). 



Brachial plexus. ( Th *S ion . ) First rib. 



Omo-hyoid. 



\ 



Behind. 



Scalenus Medius. 



Peculiarities. The snbclavian arteries vary in their origin, their course, and the height to 

 \vhich they rise in the neck. 



