This is a nerve of considerable size; it is derived from the seventh and eighth cervical roots, and after crossing the subscapularis soon enters the interspace between that muscle and teres major. It then passes behind the shoulder joint, accompanied by the posterior circumflex artery, and distributes its branches to the teres minor deltoid, mastoido-humeralis, and ultimately reaches the integument in front of the arm.

Behind the shoulder it gives small twigs to the scapulo-humeralis posticus.