MUSCLES OF THE SHOULDER 



375 



Nerve - Supply. The 



muscle is supplied by the 

 supra-scapular nerve (C. 5. 6.). 

 Action. The supraspin- 

 atus assists the deltoid in ab- 

 ducting the arm from the side. 



... SERRATUS ANTERIOR 



.SUBSCAPULARIS 

 SUPRASPINATUS 

 I PECTORALIS 



/MINOR 



Coracoid 

 process 



Triceps brachii 

 (long head) 



the horizontal position. In this movement it is aided by the supraspinatus and infraspinatus. 

 The anterior (clavicular) portion of the muscle assists the pectoralis major in drawing the arm 

 forwards, while the posterior portion draws it backwards. 



M. Supraspinatus. the supraspinatus arises by fleshy fibres from the supra- 

 spinous fossa (except near 

 the neck of the bone) and 

 from the deep fascia over 

 it (Fig. 329, p. 368). 



It is directed laterally 

 under the trapezius muscle, 

 the acromion and coraco- 

 acromial ligament, to be 

 inserted by a broad thick 

 tendon into the most 

 proximal facet on the 

 larger tubercle of the 

 humerus, and into the 

 capsule of the shoulder- 

 joint (Fig. 336, p. 376). 



SER-' 



RATUS ANTERIOR 



LATISSIMUS DORSI 



TERES MAJOR ^.*"^j 



CORACOBRACHTALIS* ^*'~ 



BICEPS (short head) 



TERES MAJOR 

 BICEPS (long head) >' 

 PECTORALIS MAJOR--' 



M. Infraspinatus. The infraspin- 

 atus arises from the infra-spinous fossa 

 of the scapula (excepting near the neck 

 of the bone and the flat surface along 

 the axillary margin) and from the thick 

 fascia over it (Fig. 337, p. 376). 



The fibres of the muscle converge to 

 the neck of the scapula ; and are inserted 

 by tendon into the middle facet on the 

 larger tubercle of the humerus, and into 

 the capsule of the shoulder-joint (Fig. 

 336, p. 376). A bursa separates the 

 muscle from the neck of the scapula, and 

 in a minority of cases communicates with 

 the synovial cavity of the shoulder-joint. 



The supraspinatus and the upper part 

 of the infraspinatus muscles are concealed 

 by the trapezius, acromion, and deltoid. 

 They cover the neck of the scapula, the 

 transverse scapular artery, and supra- 

 scapular nerve, and the capsule of the 

 shoulder-joint. 



Nerve-Supply. Supra-scapular nerve. 



Action. The muscle assists the deltoid in 

 abducting and drawing back the arm at the 

 shoulder-joint. 



DELTOID-- 



TRICEPS 

 BRACHII 



BICEPS 

 BRACHII" 



Medial inter- 

 muscular septum 



BRACHIALIS 



Biceps tendon.. J 



SUPINATOR 



MUSCLE' 



fclil 



BRACHIORADIALIS. 



FLEXOR CARPI 

 RADIALIS' 



PRONATOR TERES --! 



FIG. 335. MUSCLES OF POSTERIOR WALL OF 

 LEFT AXILLA AND FRONT OF ARM. 



M. Teres Minor. The teres minor 



is a small muscle, arising by fleshy fibres 

 from the proximal two-thirds of the flat 

 surface on the dorsal aspect of the 



axillary margin of the scapula, and from fascial septa separating it from the infra- 

 spinatus and teres major muscles (Fig. 337, p. 3*76). 



Lying alongside the lateral border of the infraspinatus, it is inserted, under cover 

 of the deltoid, by a thick flat tendon, into the most distal of the three facets on the 



