Subscapularis muscle
The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint. Structure The subscapularis is covered by a dense fascia which attaches to the scapula at the margins of the subscapularis' attachment (origin) on the scapula. The muscle's fibers pass laterally from its origin before coalescing into a tendon of insertion. The tendon intermingles with the glenohumeral (shoulder) joint capsule. A bursa (which communicates with the cavity of the shoulder joint via an aperture in the joint capsule) intervenes between the tendon and a bare area at the lateral angle of the scapula/the neck of the scapula. The subscapularis (supraserratus) bursa separates the subscapularis is from the serratus anterior. Origin It arises from its medial two-thirds of the costal surface of the scapula, the intermuscular septa (which create ridges upon the scapula), and the lower two-thirds of the groove on the axillary border (subscapular fossa) of the scapula. Some fibers arise from tendinous laminae, which intersect the muscle and are attached to ridges on the bone; others from an aponeurosis, which separates the muscle from the teres major and the long