UPPER EXTRIMITIES NERVE

Anatomy of Nerves of Upper Extremity

Median Nerve

Formation, Course, and Relations

• The median nerve is formed by the union of the medial and lateral cords of the brachial plexus.
• It passes through the arm, elbow, and forearm, and ends in the hand.
• It is accompanied by the brachial artery in the arm and is often medial to it.
• At the elbow, it is deep to the pronator teres and is then superficial to it.
• In the forearm, it is lateral to the flexor digitorum superficialis and flexor digitorum profundus.
• In the hand, it passes between the flexor digitorum superficialis and flexor digitorum profundus.

Branches and Distribution

• Branches: anterior interosseous nerve, recurrent branch, palmar cutaneous branch, and motor branches to muscles in the forearm and hand.
• Distribution: muscles of the forearm ( flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus, pronator teres, flexor carpi radialis, and palmaris longus), and skin of the palmar surface of the thumb and index and middle fingers.

Applied Anatomy

• The median nerve is responsible for sensation in the palmar surface of the thumb, index, and middle fingers.
• It is also responsible for flexion of the wrist, thumb, and fingers.

Ulnar Nerve

Formation, Course, and Relations

• The ulnar nerve is formed by the union of the medial cord of the brachial plexus and a branch from the posterior cord.
• It passes through the arm, elbow, and forearm, and ends in the hand.
• It is lateral to the brachial artery in the arm and is then medial to it.
• At the elbow, it is superficial to the flexor carpi ulnaris.
• In the forearm, it is lateral to the flexor digitorum profundus.

Branches and Distribution

• Branches: muscular branches to the biceps and brachialis, and cutaneous branches to the medial aspect of the forearm and hand.
• Distribution: muscles of the forearm (flexor carpi ulnaris and pronator quadratus) and skin of the medial aspect of the hand.

Applied Anatomy

• The ulnar nerve is responsible for sensation in the medial aspect of the hand.
• It is also responsible for flexion of the wrist and fingers.

Radial Nerve

Formation, Course, and Relations

• The radial nerve is formed by the union of the posterior cord of the brachial plexus and a branch from the lateral cord.
• It passes through the arm, elbow, and forearm, and ends in the hand.
• It is lateral to the brachial artery in the arm and is then posterior to it.
• At the elbow, it is lateral to the triceps brachii.
• In the forearm, it is deep to the brachioradialis and extensor carpi radialis brevis.

Branches and Distribution

• Branches: muscular branches to the triceps and extensor carpi radialis brevis, and cutaneous branches to the back of the arm and forearm.
• Distribution: muscles of the forearm (extensor carpi radialis brevis, extensor carpi radialis longus, and extensor digitorum) and skin of the back of the arm and forearm.

Applied Anatomy

• The radial nerve is responsible for sensation in the back of the arm and forearm.
• It is also responsible for extension of the wrist and fingers.

Musculocutaneous Nerve

Formation, Course, and Relations

• The musculocutaneous nerve is formed by the union of the lateral cord of the brachial plexus and a branch from the medial cord.
• It passes through the arm and ends in the forearm.
• It is lateral to the brachial artery in the arm.
• At the elbow, it is deep to the biceps brachii.

Branches and Distribution

• Branches: muscular branches to the biceps and brachialis, and cutaneous branches to the lateral aspect of the forearm.
• Distribution: muscles of the forearm (biceps and brachialis) and skin of the lateral aspect of the forearm.

Applied Anatomy

• The musculocutaneous nerve is responsible for sensation in the lateral aspect of the forearm.
• It is also responsible for flexion of the elbow.

Axillary Nerve

Formation, Course, and Relations

• The axillary nerve is formed by the union of the posterior cord of the brachial plexus and a branch from the lateral cord.
• It passes through the axilla and ends in the arm.
• It is lateral to the axillary artery in the axilla.
• At the shoulder, it is deep to the deltoid.

Branches and Distribution

• Branches: muscular branches to the deltoid and teres minor, and cutaneous branches to the lateral aspect of the arm.
• Distribution: muscles of the shoulder (deltoid and teres minor) and skin of the lateral aspect of the arm.

Applied Anatomy

• The axillary nerve is responsible for sensation in the lateral aspect of the arm.
• It is also responsible for abduction of the shoulder.

Diagrams

The nerves of the upper extremity can be visualized as follows:

• Median nerve: -------------------------
  • Forearm: -------------------------
  • Hand: -------------------------
• Ulnar nerve: -------------------------
  • Forearm: -------------------------
  • Hand: -------------------------
• Radial nerve: -------------------------
  • Forearm: -------------------------
  • Hand: -------------------------
• Musculocutaneous nerve: -------------------------
  • Forearm: -------------------------
• Axillary nerve: -------------------------
  • Shoulder: -------------------------

Note: The above diagrams are simplified representations of the nerves and their distribution.

Flowcharts

The relationships between the nerves and other structures can be visualized as follows:

• Median nerve:
  • brachial artery → pronator teres → flexor digitorum superficialis
  • flexor digitorum profundus → palmar cutaneous branch
• Ulnar nerve:
  • brachial artery → flexor carpi ulnaris
  • flexor digitorum profundus → cutaneous branches
• Radial nerve:
  • brachial artery → triceps brachii
  • extensor carpi radialis brevis → cutaneous branches
• Musculocutaneous nerve:
  • biceps brachii → brachialis
  • cutaneous branches → lateral aspect of the forearm
• Axillary nerve:
  • deltoid → teres minor
  • cutaneous branches → lateral aspect of the arm