Medial cutaneous nerve of the arm
Lying anterior to the vessels this small nerve pierces the deep fascia in the upper part of the arm and supplies the skin on the front and medial side of the upper part of the arm. It is the smallest branch of the brachial plexus, and arising from the medial cord receives its fibers from the eighth cervical and first thoracic nerves. It passes through the axilla, at first lying behind, and then medial to the axillary vein, and communicates with the intercostobrachial nerve.
The medial cutaneous nerve of the arm supplies the skin of the back of the medial third of the arm.