24 TOPOGEAPHICAL ANATOMY OF 



A. CIRCUMELEXA HUMERI ANTERIOR. — The anterior humeral circum- 

 flex artery leaves the axillary as this vessel lies upon the teres major. 

 Piercing the coracobrachial muscle, to which it supplies branches, the 

 artery is chiefly expended in the biceps. A feeble anastomosis with 

 twigs from the posterior circumflex may be demonstrated. 



A. BRACHiALis. — From its origin at the distal border of the teres 

 major, the brachial artery follows a course that causes it to cross the 

 line of the humerus very obliquely and approach the flexor aspect 

 of the elbow joint, where it ends in the median artery. 



In its course the artery lies in a groove formed at first by the 

 coracobrachial muscle and the medial head of the triceps, and later by 

 the biceps and the humerus. The median nerve follows the anterior 

 border of the artery, while the brachial vein lies behind it. The medial 

 surface of the brachial artery is in contact in succession with the 

 humeral part of the deep pectoral and the sternocostal part of the 

 superficial pectoral. 



The following are the collateral branches of the brachial artery : — 



1. A. profunda hrachii. — The deep artery of the arm arises 

 opposite the edge of the teres major, i.e. immediately the axillary 

 artery becomes the brachial. Several large branches are at once dis- 

 tributed to the triceps and the tensor of the antibrachial fascia; while 

 one branch accompanies the radial nerve between the long and medial 

 heads of the triceps, and will be examined at a later stage of the 

 dissection. 



It is not rarely the ease that the deep artery of the arm is double. 



2. Ramus muscularis. — A muscular branch, which may be double, 

 enters the distal part of the biceps. 



3. A. collateralis ulnwris. — The collateral ulnar artery arises from the 

 brachial just as this vessel reaches the distal border of the medial head 

 of the triceps. Following the border of this muscle, under cover 

 of the tensor fasciae antibrachii, it passes into the forearm in company 

 with the ulnar nerve. 



4. A. nutritia humeri. — The nutrient artery of the humerus 

 springs either from the brachial close to its termination or from the 

 collateral ulnar near its commencement. It immediately enters the 

 nutrient foramen of the humerus. 



5. A. collateralis radialis. — The collateral radial artery leaves the 

 brachial at an acute angle a short distance proximal to the elbow joint. 

 It lies at first between the humerus and the biceps, and then between 

 the bone and the brachialis muscle, where it comes into relation with 

 the radial nerve. The two structures, with one or, possibly, two veins, 

 enter the forearm by crossing the flexor aspect of the elbow joint. 



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