328 HEALTH AND DISEASE 



MUSCLES OF THE FORE EXTREMITY 

 EXTERNAL SCAPULAR REGION 



Supraspinatus. This muscle lies on the outer surface of the scapula 

 or blade-bone, the anterior half of which it covers. 



Origin. From the whole of the outet surface of the scapula in front 

 of its spine, and from the spine itself. 



Insertion. Below this muscle ends in two short tendons, which become 

 inserted into the inner and outer tubercle on the head of the humerus 

 respectively. The large tendon of the biceps passes between them. 



Action. To extend the humerus on the scapula. 



Infraspinatus. A fleshy muscle covering the posterior half of the 

 external surface of the scapula. 



Origin. From the entire outer surface of the bone behind the central 

 ridge or scapular spine. 



Insertion. By two short tendons, one into the outer tubercle of the 

 humerus, the other into the upper part of the ridge beneath it. A synovial 

 bursa intervenes between the latter and the external tubercle over which it 

 plays. 



Action. It abducts the humerus or upper arm and rotates it outwards. 



The Deltoid Muscle. A short muscle on the outer aspect of the 

 shoulder and arm. 



Origin. By a broad sheet of tendon from the scapular fascia, and from 

 the posterior or dorsal angle of the scapula. 



Insertion. Into the external tubercle of the humerus. 



Action. To flex the humerus on the scapula and rotate it outwards. 



Teres Minor. Situated beneath the muscle last described. 



Origin. From the posterior border, and the lower part of the outer 

 surface of the scapula. 



Insertion. Into the lower part of the bony ridge beneath the outer 

 tubercle of the humerus. 



Action. To abduct the arm and rotate it outwards. Acting with the 

 teres major, it bends the upper arm on the scapula. 



INTERNAL SCAPULAR REGION 



Subscapularis. A broad, flat muscle covering over the internal face 

 of the scapula or blade-bone, where it is lodged in a hollow or "fossa", 

 which it fills. 



Origin. From the internal surface of the scapula. 



