Ulnar Nerve

Origin

The ulnar nerve is the main nerve of the hand. It is one of the branches of the brachial plexus which arises from the medial cord and consists of nerve fibers from the anterior rami of the seventh and eighth cervical and first thoracic nerves (C7, C8, and T1).

Course

In the axilla, the ulnar nerve lies between the axillary artery and vein. It descends on the medial side of the brachial artery up to the level of insertion of the coracobrachialis, where it pierces the medial intermuscular septum and enters the posterior compartment of the arm. It is accompanied by the superior ulnar collateral vessels.

At the elbow, the ulnar nerve passes behind the medial epicondyle of the humerus where it can be palpated with a finger. It enters the forearm by passing between the two heads of flexor carpi ulnaris muscle and lies on the medial part of flexor digitorum profundus. It is accompanied by the ulnar artery in lower two thirds of the forearm. The ulnar nerve gives two muscular and two cutaneous branches in the forearm.

At the wrist, the ulnar nerve lies between the flexor carpi ulnaris and the flexor digitorum superficialis. The nerve enters the palmar aspect of the hand by passing superficial to the flexor retinaculum and lateral to pisiform bone. Here it is covered by a superficial slip of the retinaculum (volar carpal ligament). At the distal border of retinaculum, the nerve terminates by dividing into its superficial and deep branches.

Branches

Muscular branches of the ulnar nerve are given to medial half of flexor digitorum profundus and flexor carpi ulnaris. Cutaneous innervation of the ulnar nerve is supplied by the dorsal and palmar branches of the ulnar nerve. The ulnar nerve terminates by dividing into a superficial and a deep branch below the flexor retinaculum.

Supplied Structures

The muscular branches of the ulnar nerve supply the medial half of the flexor digitorum profundus, flexor carpi ulnaris, palmaris brevis, and most of the intrinsic muscles of the hand.

Cutaneous sensory innervation of the ulnar nerve supplies the skin on:

- the medial one third of palmar aspect of the hand (via the palmar branch);

- the adjacent sides of ring and little fingers (via palmar digital branches of ulnar nerve);

- the medial half of the dorsum of the hand;

- the dorsal aspect of the medial two and a half fingers (via dorsal digital branches of ulnar nerve).

List of Clinical Correlates

—Ulnar nerve injuries (Moore, Dalley and Agur, 2013)

—Ulnar claw hand

References

Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2013) Clinically Oriented Anatomy. Clinically Oriented Anatomy 7th edn.: Wolters Kluwer Health/Lippincott Williams & Wilkins.