Teres major muscle

The teres major muscle is a muscle of the shoulder that connects the scapula (shoulder blade) to the upper arm at the humerus bone just beyond the armpit region.

The teres major muscle is surrounded by the teres minor and the latissimus dorsi muscles.

Action
The teres major muscle controls the adduction of the arm - the movement of bringing the arm in toward to the body. It helps medially rotate the arm, or being able to draw elbow in and away from the side of the body. It also extends the arm at the shoulder allowing the arm to reach forward.

Origin
The teres major originates on the lower scapula, at the lower lateral border and inferior angle.

Insertion
The teres major inserts on the upper arm, at the medial lip of the intertubercular groove of the anterior humerus.

Innervation
The teres major is innervated by the posterior cord of the lower subscapular nerve (C5 and C6).