340 



THE MUSCLES 



Nerve-supply. — From the outer and inner cords of the brachial plexus (through 

 the sixth cervical nerve), by a branch from the palmar division of the median 

 nerve, which, after passing under the anterior annular ligament, goes upwards and 

 outwards to enter the upper part of the deep aspect of the muscle near its ulnar 

 border. 



Action, — (1) To al)duct, and (2) to flex the first phalanx of the thumb. As 

 the bones of the thumb are in a diflferent plane to those of the fingers, this move- 

 ment will draw the thumb forwards and at the same time slightly inwards. By its 



Fig. 283.— The Deeper Muscles of the Palm of the Haxd. 



Abductor minim 

 digiti 



Flexor sublimis 

 digitorum 



Flexor brev 

 luinirai dig 



Flexor profundus 

 digitorum 



Extensor ossis metacarpi pollicis 

 Flexor carpi radialis 

 Extensor brevis pollicis 



Abductor pollicis 

 Opponens pollicis 



Abductor 

 pollicis 

 Flexor brevis 

 pollicis 



insertion into the aponeurosis of the extensor longus pollicis, this muscle will heli) 

 (3) to extend the last phalanx of the thumb. 



Relations. — Superficially, the thenar fascia, and the superficialis \o\ve artery, 

 which usually perforates the muscle; deeply, the outer head of the flexor brevis 

 pollicis and the oi)})onens pollicis. 



Variations. — As already mentioned, it receives occasional slips from tlie radial extensors of 

 the carpus and the extensor ossis metacarpi polUcis. It freriuently receives a thin muscular sHp 

 from the skin (tvor the trapezium ; it may also be supplemented by the opponens pollicis or a small 

 slip from the styloid process of the radius. 



