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MUSCLES OF THE THUMB. 



FIG. 232. 



exposure of most of the muscles of the hand. For the fin- 

 gers, extend the incision along the middle line of each. 



The muscles of the hand are arranged into those of the 

 thumb, the little finger, and its palmar and dorsal muscles. 



MUSCLES OF THE THUMB. 



The abductor pollicis (Fig. 227) arises from the anterior 

 annular ligament, trapezium, and scaphoides, thin and 



broad, and is inserted into the 

 radial side of the base of the 

 first phalanx of the thumb. 



Function. To draw the 

 thumb from the fingers. 



The opponens pollicis 

 (flexor ossis metacarpi polli- 

 cis, Fig. 232) arises from the 

 annular ligament and trape- 

 zium, tendinous and fleshy, is 

 beneath the last, and is in- 

 serted into the radial margin 

 of the metacarpal bone of the 

 thumb its whole length. 



Function. To draw the 

 thumb to the fingers. 



The flexor brevis pollicis (Fig. 232) arises by two heads, 

 the first fleshy from the anterior annular ligament, trape- 

 zium and scaphoides, and is inserted into the outer sesa- 

 moid bone and base of the first phalanx of the thumb. 

 The second head, which is internal and posterior, arises 

 from the os magnum and base of the metacarpal bone 

 of the middle finger, and is inserted into the inner sesa- 

 moid bone and base of the first phalanx of the thumb. 



FIG. 232 represents the muscles of the Hand, a Annular ligament, b b 

 Upper and lower attachments of the abductor pollicis. c Opponens pollicis. 

 d e Flexor brevis pollicis, its two bellies. /Adductor pollicis. gg Lumbricales. 

 h Point where the flexor profundus tendon passes through the flexor perforatus. 

 i Flexor longus pollicis. j Abductor minimi digiti. k Flexor brevis minimi 

 digiti. / Os pisiforme. m First dorsal interosseous. 



