Ulnar nerve arises from the inner cord of the brachial plexus. It lies between the axillary artery and vein, and passes down on the inner side of the brachial artery in front of triceps. In the lower half of the arm it passes behind the internal intermuscular septum with the inferior profunda artery lying anterior to the inner head of triceps, and reaches the interval between the internal condyle of the humerus and the olecranon process. It enters the forearm between the two heads of flexor carpi ulnaris and passes down between it and flexor profundus digitorum on the inner side of the ulnar artery. It passes into the hand over the anterior annular ligament on the radial side of the pisiform bone, and divides beneath palmaris brevis into its terminal branches.

Branches

There are none in the upper arm.

In the forearm: Articular to the elbow-joint.

Muscular to flexor carpi ulnaris and the inner half of flexor profundus digitorum.

Cutaneous

Palmar supplies the skin over the ulnar side of the wrist, the hypothenar eminence, and ulnar side of palm. Dorsal supplies the skin on the ulnar side posterior surface of wrist and hand, the little finger and ulnar side of third finger.

In the hand: Muscular to palmaris brevis. It then divides into terminal branches superficial and deep.

Superficial

Cutaneous to anterior surface of little finger and ulnar side of third finger.

Deep

Muscular to all the muscles of the hand except those supplied by the median nerve.