Ulnar Nerve – Anatomy

 Describe The Ulnar Nerve Under The Following Heads

1. Ulnar Nerve Root value,
2. Ulnar Nerve Course and Relations,
3. Ulnar Nerve Course in hand,
4. Ulnar Nerve Branches, and
5. Ulnar Nerve Applied Anatomy.

Answer:

Ulnar Nerve Introduction:

It is the most commonly affected nerve in leprosy in the upper limb. It is also called the ‘musician’s nerve’ because fine movements of the hand are required to play musical instruments.

These are executed by small muscles of the hand which are innervated by the ulnar nerve. It is the nerve of the flexor muscles present on the medial side of the forearm, most of the intrinsic muscles of the hand, and skin on the medial side of 1 1/2 fingers.

1. Ulnar Nerve Root value:

It is the largest branch and direct continuation of the medial cord of the brachial plexus. The root values is C7, C8, and 1st T nerve. It picks up additional C7 fibers in the axilla, usually from the lateral cord.

Read And Learn More: Anatomy Notes And Important Question And Answers

2. Ulnar Nerve Course and Relations:

The structures in the course and relation of the ulnar nerve begin with the letter (M)

1. The medial cord of the brachial plexus lies on the medial side of 2nd part of the axillary artery.
2. The ulnar nerve lies medial to 3rd part of the axillary artery.
3. It also lies medial to the brachial artery.
4. In the middle of the arm, it pierces the medial intramuscular septum along with the superior ulnar collateral artery.
5. It enters the posterior compartment and lies on the medial head of the triceps. It passes behind the medial epicondyle of the humerus and is received by flexor carpi ulnaris.
6. It lies on the medial ligament of the elbow joint and rests on the medial side of the flexor digitorum profundus under a thin blanket of flexor carpi ulnaris in the upper 2/3rd of the forearm.

3. Ulnar Nerve Course in the hand:

It divides the flexor retinaculum into superficial and deep branches.

1. The superficial branch runs distally beneath palmaris brevis.
2. The deep branch is accompanied by the deep branch of the ulnar artery and passes in between the abductor digit minimi and flexor digit minimi then passes through the substance of the opponent digit minimi.
3. It passes down to the interossei, grooves the distal border of the hook of the hamate, and arches deeply in the palm within the cavity of the deep palmar arch.

4. Ulnar Nerve Branches:

Distribution of ulnar nerve

 

Note:

1. The symbol ” ” at the end of the nerve signifies the articular branch
2. The symbol ” ” at the end of the nerve signifies the cutaneous branch

5. Ulnar Nerve Applied anatomy:

1. The ulnar nerve is palpated behind the medial epicondyle of the humerus. This is thickened and is cord-like in Henson’s disease.

2. Ulnar nerve is damaged

1. At the elbow joint due to
2. Damage in the cubital tunnel is formed by the tendinous arch connecting 2 heads of flexor carpi ulnaris. The ulnar nerve is often entrapped in this tunnel and this entrapment of the ulnar nerve in the cubital tunnel is called cubital tunnel syndrome. It results in radial deviation of the hand.
3. Pressure on the ulnar nerve as it passes along the ulnar groove. It produces funny sensations along the medial border of the forearm, hypothenar surface, and little finger. Hence ‘the humerus’ is called “funny bone”.
4. At the wrist joint by the compression of the volar carpal ligament and palmaris brevis muscle. Guyon’s canal and volar ligament
5. Here all intrinsic muscles of the hand are paralyzed resulting in a typical claw hand (ulnar claw).
6. There is a hyperextension of the metacarpophalangeal joint of the ring and a little finger and flexion of the interphalangeal joint. This is because of paralysis of the interossei and lumbrical.
7. There is also a loss of sensations on the medial 1 1/2 fingers.
8. There is a loss of adduction of the thumb, as the adductor pollicis is paralyzed.

Pulp Space

 

Applied Anatomy:

1. Infection of pulp space is called whitlow, which is associated with severe throbbing pain due to increased tension in spaces.
2. The abscess is drained by lateral incision and breaking all septa. In neglected cases, it may lead to avascular necrosis of the terminal phalanx.

Contents Of Thenar Space

1. Tendons:

1. Flexor digitorum superficialis of index finger,
2. Flexor digitorum profundus of index finger,
3. Flexor pollicis longus, and
4. 1st lumbrical.

2. Vessels:

1. Arteria princeps pollicis, and
2. Arteria radialis indicis.

3. Nerves of the thumb and index finger.

Muscles Of Thenar Space

1. Flexor pollicis brevis,
2. Abductor pollicis brevis, and
3. Opponents policies.

Nerve Supply Of Muscles Of Thenar Space

All muscles of thenar eminence are supplied by the median nerve except the deep head of the flexor pollicis brevis which is supplied by the deep branch of the ulnar nerve.

Palmar Spaces

Palmar spaces

Extensor Expansion Of Little Finger

Muscles inserted in extensor expansion of little finger

Extensor Expansion Of Ring Finger

Muscles inserted in extensor expansion of ring finger

Posterior Interosseous Nerve

Posterior Interosseous Nerve Introduction:

It is a deep terminal branch of the radial nerve and arises in front of the lateral epicondyle.

1. Posterior Interosseous Nerve Peculiarity:

It bears a pseudoganglion.

2. Posterior Interosseous Nerve Course and Relation:

The nerve appears in the back of the forearm by piercing the supinator muscle and winds around the lateral side of the radius.

3. Posterior Interosseous Nerve Branches:

1. Before piercing the supinator

Extensor carpi radialis brevis, and
Supinator.

2. After piercing the supinator, the following branches are given

1. Muscular branches

Short branches to

1. Extensor digitorum,
2. Extensor digiti minimi, and
3. Extensor carpi ulnaris.

Long branches are divided into

1. Medial set, which supplies
2. Extensor pollicis longus, and
3. Extensor indices.

Lateral set, which supplies

1. Abductor pollicis longus, and
2. Extensor pollicis brevis.

2. Articular branches to

1. Wrist joint,
2. Inferior radioulnar joint, and
3. Intercarpal joints.

3. Sensory branches

1. Interosseous membrane,
2. Radius, and
3. Ulnar.