388 



THE MUSCULAK SYSTEM. 



Vinculum breve 



FLEXOR DIGITORUM SUBLIMIS 



FLEXOR DIGITORUM 

 PROFUNDUS 



J 1 1 FIRST LUMBRICAL MUSCLE 



FIRST DORSAL INTER- 

 OSSEOUS MUSCLE 



EXTENSOR INDICIS 

 PROPRIUS TENDON 



EXTENSOR DIGITORUM 

 COMMUNIS TENDON 



2. Intermediate Layer. 



M. Flexor Digitorum Sublimis. The flexor digitorum sublimis occupies a 

 deeper plane than the four previous muscles. It has a threefold origin, from the 

 humerus, radius, and ulna. (1) The chief or humeral head of origin is from the 

 medial epicondyle of the humerus by the common tendon, from the ulnar collateral 

 ligament of the elbow, and from adjacent intermuscular septa. (2) The ulnar head 

 of origin is by a slender fasciculus from the medial border of the coronoid process of 

 the ulna, proximal and medial to the origin of the pronator teres (Fig. 348, p. 389). 



(3) The radial head of origin is from 

 the proximal two-thirds of the volar 

 margin of the radius by a thin fibro- 

 muscular attachment (Fig. 348, p. 389). 

 The muscle divides in the distal 

 third of the forearm into four parts, 

 each provided with a separate tendon 

 which goes beneath the transverse car- 

 Expansion of extensor tendon p al ligament, passes through the palm 

 of the hand, and enters the correspond- 

 ing digital sheath of a finger. At 

 the wrist the four tendons are arranged 

 in pairs, those for the middle and ring 

 fingers in front, and those for the fore 

 and little fingers behind, and are sur- 

 rounded by a mucous sheath, along 

 with the tendons of the flexor digi- 

 torum profundus, beneath the trans- 

 verse carpal ligament. In the palm 

 of the hand the tendons separate, and 

 conceal the deep flexor tendons and 

 lumbrical muscles. 



Within the digital sheath each 

 tendon is split into two parts by the 

 tendon of the flexor digitorum pro- 

 fundus ; after surrounding that tendon 

 the two parts are partially re-united on its deep surface, and are inserted, after 

 partial decussation, in two portions into the sides of the second phalanx. 



The vincula tendinum form additional insertions of the muscle. They consist 

 of delicate bands of connective tissue enveloped in folds of the mucous sheath, and are 

 known as the vincula longa and brevia. The vinculum breve is a triangular band 

 of fibres containing yellow elastic tissue (ligamentum subflavum), occupying the 

 interval between the tendon and the digit for a short distance close to the insertion. 

 It is attached to the front of the inter -phalangeal articulation and the head 

 of the first phalanx. The ligamentum longum is a long narrow band extending 

 from the back of the tendon to the proximal part of the palmar surface of the 

 first phalanx. 



Nerve-Supply. Median nerve (C. 6.). 



Actions. The muscle is a flexor of the elbow, wrist, metacarpo-phalangeal and firs 

 (proximal) interphalangeal joints. 



3. Deep Layer. 



M. Flexor Digitorum Profundus. The flexor digitorum profundus is e 



large muscle arising from the ulna, the interosseous membrane, and the deep fascia 

 of the forearm, under cover of the flexor digitorum sublimis and the flexor carp 

 ulnaris. Its ulnar origin is from the volar and medial surfaces of the bone in itoi 

 proximal two-thirds, extending proximally so as to include the medial side of th< 

 olecranon, and to embrace the insertion of the brachialis muscle into the coronoicfl 



' 



FIG. 347. THE TENDONS ATTACHED TO THE 

 INDEX FINGER. 



