Teres major muscle

Origin

The teres major muscle is a thick, flattened muscle located in the upper limb. It originates from the dorsal surface of the inferior angle of the scapula.

Insertion

Its muscle fibers course upward and laterally, terminating in a flat tendon that inserts into the medial lip of the intertubercular sulcus of the humerus. At the insertion site, the tendon lies posterior to the tendon of the latissimus dorsi, separated by a bursa for smooth gliding.

Innervation

The teres major muscle is innervated by the inferior subscapular nerve, which arises from the posterior cord of the brachial plexus (C5, C6). This nerve also supplies the lower half of the subscapularis muscle.

Blood supply

The muscle receives blood supply from the posterior circumflex humeral artery and the thoracodorsal branch of the subscapular artery.

Actions

The teres major muscle is primarily responsible for medial rotation and adduction of the humerus. It also aids in shoulder joint extension and works synergistically with the latissimus dorsi muscle, helping to stabilize the humeral head within the glenoid cavity during arm movements.