PRONATOR TERES 



397 



head of the triceps and the flexor carpi radiahs. (2) The ulnar, deep or accessory, head arises 

 bv an aponeurotic band attached to the inner border of the coronoid process medial to the 

 tendon of the brachiaUs. Between the humeral and ulnar heads is a fibrous arch beneath 

 which the median nerve passes. , , , • ^ ■, ■ -f „ 



Structure and insertion.— The fibre-bundles of the humeral head are inserted ma penmform 

 manner on a tendon which begins near the middle of the belly of the muscle on the superfacial 



YiG_ 371. — Front of the Forearm: Second Layer of Muscles. 



Brachio-radialis 



Muscles of first layer 



BrachiaUs 



Flexor digitorum sublimis 



Extensor carpi radialis longus 

 Supinator 



Brachio-radialis 



- Flexor pollicis longus 



_Abductor pollicis longus 



i Extensor pollicis brevis 



Flexor carpi ulnaris 



Flexor carpi radialis 

 Palmaris longus 



surface along the radial border. The tendon gradually becomes broader ^''"ds about the volar 

 surface of the radius, and is inserted into the middle third of it^^^teral sui-^^ace 1 he att^ach 

 ment of fibre-bundles continues nearly to this insertion The fibre-bundles ^^ th^.^^XimeT^ 

 form a slender fasciculus which is inserted into the radial side of the deep surface of the humeral 



^^^%erve-supply.-By a branch derived from the median nerve before it Pf ^f ^^f^^^^^^J^^ellv 

 heads of the muscle. The nerve enters the proximal part of the middle ^^ird °f the main be y 

 of the muscle on its deep surface near the radial border. The branch *« f ^^^iXumeTal S^^ 

 enters this portion of the muscle somewhat proximal to its fusion with the humeral neaa. 

 The nerve fibres arise from the sixth and seventh cervical nerves. 

 Action. — To pronate and flex the forearm. 



