THE AXILLA R Y ARTER Y 



641 



Musculo- 

 apiral nerve. 



The alar thoracic is a small branch which supplies the nodes and areolar 

 tissue of the axilla. Its place is frequently supplied by branches from some of 

 the other thoracic arteries. 



The subscapular (a. Subscapularis), the largest branch of the axillary artery, 

 arises opposite the lower border of the Subscapularis muscle, and passes down- 

 ward and backward along its lower margin to the inferior angle of the scapula, 

 where it anastomoses with the long thoracic and intercostal arteries and with the 

 posterior scapular branch of the trans- 

 verse cervical, and terminates by sup- 

 plying branches to the muscles in the 

 neighborhood. About an inch and a 

 half from its origin it gives off a large 

 branch, the dorsalis scapulae. 



The dorsalis scapulae (a. circumflexa 

 scapulae) is generally larger than the 

 continuation of the subscapular. It 

 curves around the axillary border of the 

 scapula, leaving the axilla through the 

 space between the Teres minor above, 

 the Teres major below, and the long 

 head of the Triceps externally (Fig. 

 458), and enters the infraspinous fossa 

 by passing under cover of the Teres 

 minor, where it anastomoses with the 

 posterior scapular and suprascapular 

 arteries. In its course it gives off two 

 branches: one (infrascapular) enters the 

 subscapular fossa beneath the Subscap- 

 ularis, which it supplies, anastomosing 

 with the posterior scapular and supra- 

 scapular arteries; the other is continued 

 along the axillary border of the scapula, 

 between the Teres major and minor, 

 and, at the dorsal surface of the inferior 

 angle of the bone, anastomoses with the 

 posterior scapular. In addition to these, 

 small branches are distributed to the 

 back part of the Deltoid muscle and the 

 long head of the Triceps, anastomosing 

 with an ascending branch of the superior 

 profunda of the brachial. 



The circumflex arteries wind around 

 the surgical neck of the humerus. The 

 posterior circumflex (a. circumflexa hum- 

 eri posterior) (Fig. 458), the larger of 

 the two, arises from the back part of the 

 axillary opposite the lower border of 



the Subscapularis muscle, and, passing backward with the circumflex veins and 

 nerve through the quadrangular space bounded by the Teres major and minor, the 

 scapular head of the Triceps and the humerus, winds around the neck of that bone 

 and is distributed to the Deltoid muscle and shoulder-joint, anastomosing with the 

 anterior circumflex and acromial thoracic arteries, and with the superior profunda 

 branch of the brachial artery. The anterior circumflex (a. circumflexa humeri ante- 

 rior) (Figs. 458 and 460), considerably smaller than the preceding, arises nearly 



41 



Inferior 

 profunda. 



Anastomotica 



mayiiu. 



FIG. 461. The brachial artery. 



