Radial Nerve Anatomy Diagram

Radial nerve pathway

The radial nerve is a crucial peripheral nerve of the upper limb. It originates from the posterior cord of the brachial plexus and has roots from C5 to T1. It serves both motor and sensory functions, innervating muscles in the arm and forearm and providing sensation to parts of the hand and arm. It splits into several nerve branches.

The radial nerve begins in the axilla, situated posterior to the axillary artery. It exits the axilla into the upper arm through the triangular interval, supplying branches to the long and lateral heads of the triceps brachii. It is initially separated from the radial artery in the upper one-third of the forearm. It then descends down the arm within the radial groove of the humerus, wrapping around the humerus laterally and supplying a branch to the medial head of the triceps brachii. Accompanied by the deep branch of the brachial artery, the nerve travels anterior to the lateral epicondyle of the humerus through the cubital fossa. At the forearm, it splits into two terminal branches: the deep branch (posterior interosseous nerve) and the superficial branch.

In the arm, the radial nerve innervates the triceps brachii, which extends the arm at the elbow. In the forearm, the deep branch of the radial nerve innervates the extensor muscles, including the brachioradialis and extensor carpi radialis longus, aiding in wrist and finger extension and forearm supination. The posterior interosseous nerve continues to innervate the remaining posterior forearm muscles.

The radial nerve provides cutaneous innervation through several branches:

• Lower lateral cutaneous nerve of the arm: Innervates the lateral aspect of the arm.
• Posterior cutaneous nerve of arm: Innervates the posterior surface of the arm.
• Posterior cutaneous nerve of the forearm: Innervates the middle posterior forearm.
• Superficial branch: Innervates the dorsal surface of the lateral three and a half digits and the associated dorsum of the hand.

Injury to the radial nerve can result in radial nerve palsy, characterized by wrist drop and sensory deficits in the radial nerve's distribution area.

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