The teres major muscle is one of the six muscles within the scapulohumeral muscle group. The muscle is located on the underside of the upper arm, in the area between the shoulder and elbow. It has a flat shape and is supplied with nerves from the lower subscapular nerve. The arteries supply blood and oxygen to the muscle. The muscle is located near the teres minor muscle, which is the primary muscle found surrounding the rotator cuff. The teres major starts just below the armpit and stops at the top of the humerus, the large bone of the upper arm. It is considered a medial rotator and helps control certain movements of the humerus. The muscle helps the latissimus dorsi in moving the humerus back and down when extended, and also stabilizes the upper portion, or head, of the humerus.