258 



APPLIED ANATOMY. 



convexity outward. If the arm is placed straight out away from the body, the artery 

 is straight. If the arm is abducted above the level of the shoulder, the artery again 

 becomes curved but with its convexity downward. 



The line of the artery is straight only when the arm is out from the body, when 

 its course is represented by a line drawn from the middle of the clavicle to the 

 anterior surface of the elbow, midway between the two condyles. It passes down 

 along the inner side of the coracoid process and the coracobrachialis muscle about at 

 the junction of the anterior and middle thirds of the axilla. It is divided into three 

 parts by the pectoralis minor muscle (Fig. 270). 



First Portion. The first portion of the axillary is usually stated to be 2.5 cm. 

 (i in.) in length, and for surgical purposes we may accept this as a working basis. 



A. H. Young has pointed out that, with the arm out from the body, the upper 

 border of the pectoralis minor is nearly or quite level with the lower border of 

 the first rib, but the muscle leaves the side of the chest to go to the coracoid 

 process and that makes an interspace, more than 2.5 cm. long, above its upper edge 



Pectoralis major 

 Deltoid 



Biceps 



Coracobrachialis 



Groove for axillary vessels and nerves 

 Long head of triceps muscle 



Teres major and latissimus dorsi muscles 



FIG. 270. Line indicating the course of the axillary artery. 



and between it and the lower edge of the subclavius muscle, in which the artery can 

 be ligated. In the first portion the axillary artery above the pectoralis minor lies 'too 

 deep to be compressed, being on a lower level than the pectoralis major, therefore 

 it is better to compress the subclavian above the clavicle. 



Branches. The first portion of the axillary gives off two branches, the superior 

 thoracic and the acromiothoracic (thoraco-acromialis) (Fig. 271). 



The stiperior thoracic comes off posteriorly and winds around behind the axillary 

 vein to supply the under surface of the pectoralis minor, intercostal muscles, serratus 

 anterior, and side of the chest. It is a small vessel. 



The acromiothoracic (thoraco-acromialis^) is a short large trunk which comes off 

 anteriorly, winding around the edge of the pectoralis minor and piercing the costo- 

 coracoid membrane to divide into four branches: an acromial, to the acromion 

 process; a humeral, which follows the cephalic vein between the deltoid and pecto- 

 ralis major; a pectoral, which supplies the under surface of the pectoralis major and 

 gives branches to the mammary gland; and a clavicular, to supply the subclavius 

 muscle. 



Relations. Posteriorly, the artery lies on the first intercostal space and 

 muscle, the second and part of the third serrations of the serratus anterior, the pos- 

 terior thoracic nerve (or external respiratory of Bell), and the internal anterior 

 thoracic nerve to the pectoralis minor and major. 



