298 THE CIRCULATORY SYSTEM. 



thus formed passes into the hand and gives origin to the 

 branches described under the ulnar artery. The presence and 

 size of this branch of the radial varies with the size of the ulnar 

 artery, it being smaller or absent as the ulnar is larger. It is 

 shown at m, Fig. 123. The radial artery (g) now turns 

 gradually dorsad and passes beneath the tendon of the extensor 

 brevis pollicis onto the dorsum of the hand. It passes over the 

 oblique groove on the dorsal surface of the base of the second 

 metacarpal beneath the tendon of the extensor carpi radialis 

 longus and passes between the bases of the second and third 

 metacarpals into the palm of the hand. Here it passes to the 

 ulnar side and anastomoses with the ulnar artery to form the 

 palmar arch. 



Branches of the Radial Artery. 



1. A. radialis recurrens (z). The radial recurrent arises 

 in the concavity of the elbow and sends a branch proximad to 

 the structures in the concavity; it then continues to the radial 

 side of the forearm at the elbow, supplying adjacent parts of 

 the brachialis (2), the extensor carpi radialis, and the extensor 

 communis digitorum. 



2. A, ulnaris recurrens (/). The ulnar recurrent arises 

 on the medial side of the tendon of the biceps and supplies 

 structures in the concavity of the elbow on the ulnar side, also 

 the pronator teres (5) and proximal ends of the flexor carpi 

 radialis and flexor profundis digitorum. 



3. Rami musculares. Muscular branches are given off 

 along the course of the artery, to adjacent muscles. A nutrient 

 artery to the radius leaves the radial artery about two centi- 

 meters distad of the supracondyloid foramen. 



4.. Aa interosseae (anterior (/) and posterior) are given off 

 usually separately between the origin of the ulnar artery and 

 the biceps tendon. Sometimes they arise as a common trunk 

 which soon divides. The posterior interosseous artery passes 

 distad, supplying the flexor muscles of the forearm. It also 

 sends a branch to the pronator teres. The anterior interos- 

 seous (/) may arise from the ulnar artery. It passes dorsad to 

 the interosseous membrane, on which it runs distad ; sends a 

 nutrient branch to the ulna, and then passes to the wrist in the 



