Teres major - Musculus teres major
Origin: Posterior aspect of the inferior angle of the scapula
Insertion: Medial lip of the intertubercular sulcus of the humerus
Artery: Subscapular and circumflex scapular arteries
Nerve: Lower subscapular nerve (segmental levels C5 and C6)
Action: Internal rotation of the humerus
The Teres major is a thick but somewhat flattened muscle, which arises from the oval area on the dorsal surface of the inferior angle of the scapula, and from the fibrous septa interposed between the muscle and the Teres minor and Infraspinatus; the fibers are directed upward and lateralward, and end in a flat tendon, about 5 cm. long, which isinserted into the crest of the lesser tubercle of the humerus. The tendon, at its insertion, lies behind that of the Latissimus dorsi, from which it is separated by a bursa, the two tendons being, however, united along their lower borders for a short distance.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).