THE POSTERIOR SCAPULAR REGION 465 



The Subscapularis (m. Subscapularis) (Fig. 349) is a large triangular muscle 

 which fills up the subscapular fossa, arising from its internal two-thirds, with the 

 exception of a narrow~mkfgm along the internal border, and the surfaces at the 

 superior and inferior angles which afford attachment to the Serratus magnus; 

 it also arises from the lower two-thirds of the groove on the axillary border of the 

 bone. Some fibres arise from the tendinous laminae, which intersect the muscle, 

 and are attached to ridges on the bone; and others from an aponeurosis, which 

 separates the muscles from the Teres major and the long head of the Triceps. 

 The fibres pass outward, and, gradually converging, terminate in a tendon, 

 which is inserted into the lesser tuberosity of the humerus and into the. neck of 

 the humerus just behind this tuberosity and in front of the capsular ligament 

 of the shoulder-joint. The tendon of the muscle is in close contact with (he 

 anterior part of the capsular ligament of the shoulder-joint, and glides over a large 

 bursa (bursa m. subscapular is), which separates if from the base of the coracoid 

 process. This bursa communicates with the cavity of the joint by an aperture in 

 the capsular ligament. 



Relations. Its deep surface forms a considerable part of the posterior wall of the axilla, 

 and is in relation with the Serratus magnus, Coracobrachialis, and Biceps, the axillary vessels 

 and brachial plexus of nerves, and the subscapular vessels and nerves. By its superficial sur- 

 face, with the scapula and the capsular ligament of the shoulder-joint. Its lower border is con- 

 tiguous to the Teres major and Latissimus dorsi. 



Nerves. It is supplied by the fifth and sixth cervical nerves through the upper and lower 

 subscapular nerves. 



Actions. The Subscapularis rotates the head of the humerus inward; when the arm is 

 raised, it draws the humerus forward and downward. It is a powerful defence to the front of 

 the shoulder-joint, preventing displacement of the head of the bone. 



5. The Posterior Scapular Region (Figs. 351, 352). 



Supraspinatus. Teres minor. 



Infraspinatus. Teres major. 



Dissection. To expose these muscles, and to examine their insertion into the humerus, 

 detach the Deltoid and Trapezius from their attachment to the spine of the scapula and acromion 

 process. Remove the clavicle by dividing the ligaments connecting it with thejxjracoid process, 

 and separate it at its articulation with the scapula; divide the acromion process near its root 

 with a saw. The fragments being removed, the tendons of the posterior Scapular muscles will 

 be fully exposed. A block should be placed beneath the shoulder-joint, so as to make the 

 muscles tense. 



The supraspinatus fascia (fascia supraspinata) is a thick and dense membranous 

 layer, which completes the osseofibrous case in which the Supraspinatus muscle 

 is contained; it affords attachment, by its deep surface, to some of the fibres of 

 the muscle. It is thick internally, but thinner externally under the coraco- 

 acromial ligament. 



The Supraspinatus muscle (m. supraspinatus) occupies the whole of the supra- 

 spinous fossa, arising from its internal two-thirds and from the strong fascia 

 which covers the surface of the muscle. The muscle fibres converge to a tendon 

 which passes across the upper part of the capsular ligament of the shoulder-joint, 

 to which it is intimately adherent, and is inserted into the highest of the three 

 facets on the greater tuberosity of the humerus. 



Relations. By its superficial surface, with the Trapezius, the clavicle, the acromion, the coraco- 

 acromial ligament, and the Deltoid; by its deep surface, with the scapula, the suprascapular 

 vessels and nerve, and upper part of the shoulder-joint. 



The infraspinatus fascia (fascia infraspinata) is a dense fibrous membrane, 

 covering in the Infraspinatus muscle and attached to the circumference of the 



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