Ulnar nerve

A major nerve of the upper limb

Diagram of the brachial plexus

The ulnar nerve is one of the major nerves of the upper limb. It is part of the brachial plexus and is responsible for innervating several muscles in the forearm and hand, as well as providing sensation to the skin of the hand.

Anatomy

The ulnar nerve originates from the brachial plexus, specifically from the medial cord, which contains fibers from the C8 and T1 nerve roots. It travels down the arm, passing posterior to the medial epicondyle of the humerus, where it is superficial and can be palpated. This location is commonly referred to as the "funny bone" because striking the nerve here can cause a tingling sensation.

Anatomy of the ulnar nerve

In the forearm, the ulnar nerve travels between the flexor carpi ulnaris and the flexor digitorum profundus muscles. It provides motor innervation to the flexor carpi ulnaris and the medial half of the flexor digitorum profundus. The nerve then enters the hand through Guyon's canal, a fibro-osseous tunnel at the wrist.

Function

The ulnar nerve is responsible for both motor and sensory functions. In the hand, it innervates the hypothenar muscles, the adductor pollicis, the interossei muscles, and the medial two lumbricals. These muscles are crucial for fine motor control and grip strength.

Muscles of the forearm

Sensory innervation by the ulnar nerve includes the skin of the medial one and a half fingers (the little finger and half of the ring finger) and the associated palm area.

Clinical significance

The ulnar nerve is susceptible to injury at several points along its course. Common sites of injury include the elbow, where it can be compressed in the cubital tunnel, and the wrist, where it can be compressed in Guyon's canal.

Zones of Guyon's canal syndrome

Cubital Tunnel Syndrome

Cubital tunnel syndrome occurs when the ulnar nerve is compressed at the elbow. Symptoms include numbness and tingling in the ring and little fingers, weakness in the hand, and pain in the elbow.

Guyon's Canal Syndrome

Guyon's canal syndrome, also known as ulnar tunnel syndrome, results from compression of the ulnar nerve at the wrist. It can cause similar symptoms to cubital tunnel syndrome, but the location of the compression is different.

Related pages

• Brachial plexus
• Cubital tunnel syndrome
• Guyon's canal
• Nerve injury

Nerves of the left upper extremity

See also

• Median nerve
• Radial nerve
• Peripheral nerve injury