FLEXORS OF FINGERS 105 



dial nerve. Insertion. The (top of the) olecranon process of the 

 ulna. 



Action. It extends the forearm (opposing the biceps). 



Nerve. Radial. 



Note. The back of the triceps is covered at its lower portion by a fibrous 

 layer (aponeurosis) which receives many of the muscular fibers. In action, 

 the three heads swell while this fibrous layer remains flat. 



MUSCLES OF THE FOREARM 

 Anterior 



The superficial flexors. The medial epicondyle of the humerus 

 gives origin to a group of superficial muscles which flex the wrist 

 and fingers (Fig. 87). 



Flexor carpi radialis, or radial flexor of the wrist. Origin. 

 The medial epicondyle. Insertion. The base of the second 

 metacarpal bone (that of the index-finger). 



Nerve. Median. 



Flexor carpi ulnaris, or ulnar flexor of the wrist. Origin. 

 The medial epicondyle and dorsal border of the ulna. Insertion. 

 The base of the fifth metacarpal bone (after attachment to the 

 pisiform and unciform bones). 



Action of the two. To flex the wrist. 



Nerve. Ulnar. 



Flexor digitorum sublimis, or superficial flexor of the fingers. 

 Origin. The medial epicondyle, the upper extremity of the ulna, 

 and the shaft of the radius (the three long bones) Insertion. By 

 four tendons, one for each finger, on the second row of phalanges. 



Action. It flexes the second joints of the fingers, but not the 

 finger-tips. 



Nerve. Median. 



Deep flexors. The shafts of the bones give origin to the deep 

 flexors of the fingers and thumb, which act upon the third row of 

 phalanges. 



Flexor digitorum profundus, or deep flexor oj the fingers. Is underneath 

 the superficial flexor. Origin. The shaft of the ulna. Insertion. By four 

 tendons, on the third or last row of phalanges. 



Action. It flexes the finger-tips. 



