Median Nerve Anatomy, Function & Location

Describe The Median Nerve Under The Following Heads

1. Median Nerve Root value,

2. Median Nerve Branches, and

3. Median Nerve Applied Anatomy.

Answer:

1. Median Nerve Root value:

The median nerve has lateral and medial roots. The Lateral root is the continuation of the lateral cord of the brachial plexus and has C5, C6, and C7 fibers. The medial root is derived from the medial cord and has C8 and T1 fibers.

1. Course and relations: The lateral and medial roots clasp 2nd part of the axillary artery and lie on the respective sides.

2. In the axilla

1. The medial root crosses the 3rd part of the axillary artery from the front. It joins the lateral root, and the nerve is formed on the lateral side at the lower border of the axilla.
2. It enters the arm. It then passes vertically down lateral to the brachial artery.
3. In the middle of the arm, it crosses the brachial artery from the front.
4. It remains on the medial side of the brachial artery in the lower part of the arm.
5. It courses between the biceps brachii and brachialis.
6. In the cubital fossa, it crosses the ulnar artery from medial to lateral.

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

Note:

The symbol  ” ”  at the end of the nerve signifies the cutaneous branch

3.In the cubital fossa

1. It is the most medially important structure of the cubital fossa.

2. It passes between two heads of pronator teres.

3. The relations in the lower part of the cubital fossa from superficial to deep are

1. Superficial head of pronator teres
2. Median nerve
3. The deep head of the pronator teres
4. Ulnar artery.

4. In the forearm

It runs distally in the midline of the forearm.
It is closely attached to the deep surface of the flexor digitorum superficialis muscle.
It passes between the superficial and deep muscles of the forearm.
It is accompanied by the median artery (branch of an anterior interosseous artery).

5. In the wrist

1. Above the wrist, the nerve comes close to the surface between the tendons of

1. Flexor carpi radialis, and
2. Flexor digitorum superficialis.

2. It lies deep and partly lateral to the tendon of the palmaris longus.

3. It passes deep to the flexor retinaculum, surrounded by 10 tendons. These are

1. Four superficial flexor tendons of digits,
2. Four deep flexor tendons of digits,
3. A long deep tendon of the thumb, and
4. A tendon of the radial side of the wrist.

4. After giving recurrent branch, it divides into

1. Lateral, and
2. Medial branch.
3. The lateral branch subdivides into three palmar digital branches, which supply the

1. The skin of both sides of the thumb, and
2. Radial side of the index finger.

The branch to the index finger provides a muscular branch to 1st lumbrical.

4. The medial branch is subdivided into two common palmar digital nerves. The lateral common digital nerve gives a branch to 2nd lumbrical.

5. Median nerve gives the anterior interosseous nerve which accompanies the anterior interosseous artery and supplies

1. Flexor pollicis longus,
2. Pronator quadratus, and
3. Lateral 1/2 of flexor digitorum profundus.

2. Median Nerve Branches:

They are grouped as branches in the

1. Arm,

2. Cubital fossa,

3. Forearm, and

4. Hand.

5. In the arm, it gives

Sympathetic filaments to the brachial artery, and a twig to the Elbow joint.

6. In cubital fossa, the median nerve gives a branch to pronator teres. After emerging from the pronator teres, it supplies

1. Flexor carpi radialis,
2. Palmaris longus, and
3. Flexor digitorum superficialis

7. In the forearm, gives off

1. Anterior interosseous nerve

2. Palmar cutaneous branch

3. Anterior interosseous nerve: It descends on the interosseous membrane up to the wrist. The nerve ends in the anterior part of the capsule of the wrist and carpal joints.

It is a sensory branch to these joints. Before the nerve ends, it supplies

1. Radial 1/2 of flexor digitorum profundus,
2. Flexor pollicis longus, and
3. Pronator quadratus.

4. Palmar cutaneous branch: It arises about 5 cm proximal to the wrist, and pierces the deep fascia just superficial to the flexor retinaculum. It supplies the skin of the thenar muscles.

7. Hand: It divides into lateral and medial.

1. Lateral, and

2. Medial branches

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

3. The lateral branch is muscular. It is short and stout. It recurves around the distal border of the flexor retinaculum to supply the three thenar muscles, namely

1. Abductor pollicis,
2. Superficial head of flexor pollicis brevis, and
3. Opponents policies.

4. Medial branches are cutaneous. They are three in number. They are palmar digital branches.

1. The 1st two supply the skin of

1. Sides of the thumb,
2. Its web, and
3. The distal part of the dorsal surface.

Various positions of hand, muscles involved, and tests carried out for muscle testing

2. The 3rd supplies the skin of

1. Radial side of the index finger, and
2. 1st lumbrical muscle.

3. Median Nerve Applied anatomy:

1. Injury above the elbow joint: The cause of injury is mainly by supracondylar fracture of the humerus.
2. Injury at the middle of the forearm: Flexor digitorum superficialis is paralyzed leading to a condition called “Pointing index finger”.
3. At wrist: The main cause is compression of the median nerve in the carpal tunnel.

Clinical manifestations of compression of the median nerve in the carpal tunnel

1. It is a nerve in humans and other animals in the upper limb.
2. It supplies the opponens pollicis muscle which brings the opposition of the thumb.
3. The median nerve is called the peripheral eye because it provides sensory innervations to lateral 3 1/2 digits which are used to see the thinness and texture of cloth. It is better appreciated by hand through palpation than with vision.
4. It is also called the eye of the hand because the loss of sensations over the thumb and index finger renders the hand virtually useless in buttoning a coat or a shirt.
5. To be concise and precise about the median nerve, we can say.

 

It is called the ‘median nerve’ because it passes down the middle of the front of the arm. It is one of the 5 main nerves of the upper limb originating from the brachial plexus.

It supplies most of the flexor muscles of the forearm and only three muscles, and two lumbricals in the hand.

It is cutaneous to the flexor surfaces, and nails of 3 1/2 digits and a corresponding area of the palm.

It is worth noting that right from its formation, the median nerve enjoys dancing from medial to lateral and vice versa. It literally forgets to give branches in the arm except for the sympathetic branch to the artery and the articular branch to the elbow joint.

I emphasize this piece of information because it is very important to answer the MCQs based on the relations of artery and nerve in the arm and cubital fossa.

In the forearm, it slips between superficial and deep groups of flexor muscles of the forearm and sleeps on the mattress formed by flexor digitorum profundus and blanketed by flexor digitorum superficialis-the muscles of the forearm.

It is interesting to note that here it is accompanied by its fellow brother, i.e. median artery, a branch of the anterior interosseous artery.

Please remember,

It is the nutrient artery to the median nerve.

The anterior interosseous nerve is the nerve of the deep flexor muscles of the forearm.

Apart from the above muscles, it supplies the interosseous membrane and periosteum of the radius and ulna.

Friends, it is important to note here some of the additional features of the common digital nerve.

The lateral common digital nerve supplies 2nd lumbrical.

The medial branch of the common digital nerve gives a communicating branch to the common digital branch of the ulnar nerve.

The pulp pads of the index finger and middle finger are exclusively supplied by the median nerve. Such areas are autonomous sensory areas.

Lastly, the median nerve does give articular branches to the wrist joint-metacarpal-phalangeal and interphalangeal branches.