Final answer:
The radial nerve originates from the brachial plexus and innervates the posterior aspect of the upper limb, including motor functions for the elbow, wrist, and finger extension as well as sensory innervation to parts of the arm and hand.
Step-by-step explanation:
The radial nerve is a significant peripheral nerve of the arm that is responsible for innervating the posterior aspect of the upper limb. It originates from the brachial plexus, which is composed of spinal nerves C5 through C8 and T1. The radial nerve then travels down the posterior compartment of the arm, providing motor innervation to the muscles in the posterior upper arm responsible for extending the elbow as well as the muscles in the posterior forearm responsible for extending the wrist and fingers.
The radial nerve also provides sensory innervation to parts of the arm, specifically cutaneous sensation via sensory neurons located in the dorsal root ganglia. The radial nerve continues to travel down, passing the radial groove on the humerus and winding around the lateral side towards the anterior compartment of the forearm just posterior to the brachioradialis muscle and lateral to the radius bone. Its terminal branches include the posterior interosseous nerve, which continues to supply motor and sensory functions to the forearm, and superficial branch, which contributes to sensation over the back of the hand and digital extensor muscles of the fingers.