Ulnar Nerve |Upper Limbs|Anatomy

ULNAR NERVE

The ulnar nerve is so named because it runs along the ulnar side of the upper limb.

ROOT VALUE

Ventral rami of C8 and T1. It also gets contribution from ventral ramus of C7.

COURSE & RELATIONS

It is the continuation of the medial cord of brachial plexus in the axilla. It courses successively through four regions: axilla, arm, forearm and hand, where it terminates by dividing into superficial and deep branches. The course and relations of ulnar nerve in these regions are as follows.

Axilla: In axilla, the ulnar nerve lies between the axillary vein and the axillary artery on a deeper plane medial to 3rd part of axillary artery.

Arm: It enters the arm by running downwards on the medial side of the brachial artery in its proximal part. At the midarm (i.e. at the level of insertion of coracobrachialis), it pierces the medial intermuscular septum to enter the back of arm. Here it descends to run in a groove on the back of medial epicondyle of humerus, where it can be palpated.

Forearm: The ulnar nerve enters the front of forearm by passing between two heads of flexor carpi ulnaris. Here it lies on medial part of flexor digitorum profundus. It is accompanied by the ulnar artery on its lateral side in the lower two-third of forearm.

Hand: The nerve enters the palm by passing superficial to the flexor retinaculum and medial to ulnar artery. At the distal border of flexor retinaculum, it ends by dividing into superficial and deep terminal branches.

BRANCHES & DISTRIBUTION

In Axilla and Arm: No branches

In Forearm

• Muscular branches to supply:

~Flexor carpi ulnaris

~Flexor digitorum profundus (medial half)

• Palmar cutaneous branch: It arises at about midforearm and provides cutaneous innervation to skin of the hypothenar eminence.

• Dorsal cutaneous branch: It arises about 5 cm above the wrist and gives off dorsal digital nerves to supply sensory innervation to dorsal aspects of the medial 12 digits excluding their distal phalanges.

In Hand

• Superficial terminal branch, which supplies

~Palmaris brevis muscle

~Cutaneous innervation to medial one-third of palm and medial 11⁄2 fingers, including their nail beds.

• Deep terminal branch, which supplies:

~ Medial two lumbricals

~ Muscles of hypothenar eminence (abductor digiti minimi, flexor digiti minimi and opponens giti minimi)

~All the interossei (three palmar and four dorsal)

~Adductor pollicis

APPLIED ANATOMY

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