Has three heads, the medial branch is the most developed. The long head is at the caudal margin of the scapula; The lateral, medial, and accessory heads are at the shaft of the humerus. | Has three heads, the medial branch is the most developed. The long head is at the caudal margin of the scapula; The lateral, medial, and accessory heads are at the shaft of the humerus. |