104 



ANATOMY AND PHYSIOLOGY 



ARM MUSCLES 



Anterior 



Biceps brachii (a two-headed muscle). Origin. The scapula: 

 the long head above the glenoid fossa, and the short head on the cora- 



coid process. Insertion. By one 

 tendon on the tuberosity of the 

 radius (Fig. 86). 



Nerve. Musculo-cutaneous. 



Note. If the biceps brachii begins 

 to contract while the hand is pronated, 

 the first effect would be to pull the 

 radial tuberosity around and place the 

 hand in the supinated position, then 

 flexion would follow; in other words, 

 the biceps may act as both a supinator 

 and flexor. 



The coraco-brachialis. A smaller 

 muscle, close to the biceps. Origin. 

 The tip of the coracoid process. In- 

 sertion. The shaft of humerus, medial 

 side, opposite the deltoid. 



Action. It lifts the humerus forward. 



Nerve. Musculo-cutaneous . 



The brachialis. Is underneath the 

 biceps. Origin. The anterior surface 

 of the humerus. Insertion. The tu- 

 bercle of the ulna, just below the coro- 

 noid process. 



Action. With the biceps it flexes 

 the forearm. 



Note. This is a broad muscle and 

 covers the front of the elbow-joint. 



N erve. Musculo - cutaneous and 

 radial. 



FIG. 86. MUSCLES OF THE ARM. 



* 2 i 3 S Biceps and bicipital fas- 

 cia; 4, attachment of biceps to tuber- 

 osity of radius; 6, coracobrachialis; 

 7, 8, insertion of pectoralis major; 

 9, latissimus dorsi (insertion) ; 10, teres 

 major; n, subscapularis; 12, bra- 

 chialis; 13, 14, two heads of triceps. 

 (Sappcy.) 



ARM MUSCLES 

 Posterior FIG. 84 



The triceps brachii (a three- 

 headed muscle). Origin. The long head, on the scapula, just 

 below the glenoid fossa; the medial and lateral heads on the pos- 

 terior surface of the humerus, separated by the groove for the ra- 



