Which upper extremity nerve is responsible for thumb opposition?

The nerve responsible for thumb opposition is the median nerve. This function is primarily mediated by the opponens pollicis muscle, which is innervated by the median nerve. Thumb opposition is essential for grasping and manipulating objects as it allows the thumb to touch the tip of the other fingers. It is a critical action for many fine motor tasks and dexterity in the hand.

In the context of other nerve functions, the ulnar nerve influences movements of the little finger and some intrinsic hand muscles, while the radial nerve primarily serves the back of the arm and forearm, facilitating extension of the elbow, wrist, and fingers. The musculocutaneous nerve is mainly responsible for innervating the flexor muscles of the arm. None of these nerves directly contribute to the opposition of the thumb, highlighting the specific role of the median nerve in this function.