Nerve supply of the human arm

Nerve Supply of the Human Arm

The nerve supply of the human arm is a complex network that is essential for motor function and sensory perception. The nerves of the arm originate from the brachial plexus, which is a network of nerves formed by the anterior rami of the lower four cervical nerves (C5-C8) and the first thoracic nerve (T1).

Brachial Plexus

The brachial plexus is divided into five main sections: roots, trunks, divisions, cords, and branches. Each section plays a crucial role in the innervation of the arm.

• **Roots**: The roots of the brachial plexus are the anterior rami of the spinal nerves C5, C6, C7, C8, and T1.
• **Trunks**: These roots combine to form three trunks: the upper trunk (C5-C6), middle trunk (C7), and lower trunk (C8-T1).
• **Divisions**: Each trunk splits into an anterior and a posterior division.
• **Cords**: The divisions regroup to form three cords: lateral, medial, and posterior.
• **Branches**: The cords give rise to the major nerves of the arm.

Major Nerves of the Arm

The major nerves that arise from the brachial plexus and supply the arm include:

• **Musculocutaneous nerve**: This nerve arises from the lateral cord and innervates the biceps brachii, brachialis, and coracobrachialis muscles. It is responsible for flexion of the elbow and supination of the forearm.

• **Axillary nerve**: Originating from the posterior cord, the axillary nerve innervates the deltoid and teres minor muscles, and provides sensation to the skin over the deltoid region.

• **Radial nerve**: Also from the posterior cord, the radial nerve innervates the triceps brachii and the extensor muscles of the forearm. It is crucial for extension of the elbow, wrist, and fingers.

• **Median nerve**: This nerve arises from both the lateral and medial cords and innervates most of the flexor muscles in the forearm, as well as the thenar muscles of the hand. It is responsible for flexion of the wrist and fingers, and pronation of the forearm.

• **Ulnar nerve**: Originating from the medial cord, the ulnar nerve innervates the flexor carpi ulnaris and the intrinsic muscles of the hand. It is responsible for fine motor control of the fingers.

Clinical Relevance

Injuries to the nerves of the arm can lead to significant functional impairment. For example, damage to the radial nerve can result in "wrist drop", while injury to the ulnar nerve can cause "claw hand". Understanding the nerve supply of the arm is crucial for diagnosing and treating such conditions.

See Also

• Peripheral nervous system
• Anatomy of the human arm
• Brachial plexus injuries

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2013). Clinically Oriented Anatomy. Lippincott Williams & Wilkins.
• Standring, S. (2015). Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences.