Please tell me about the median nerve of the hand.

The median nerve actually innervates more than just the hand. This nerve actually emanates from the brachial plexus, which is formed by ventral nerve branches or rami from spinal nerves C5-C8, and T1. These rami are mixed nerves (contain sensory and motor fibers). The median nerve supplies most muscles of the anterior forearm, such as the pronator teres, flexor carpi radialis (FCR), flexor digitorum superficialis (FDS) and the lateral half of the flexor digitorum profundus (FDP). The median nerve innervates the skin of the lateral two-thirds of the palm and the fingers.

Damage to the median nerve presents the following signs: numbness, tingling, and pain in the palm and fingers. Movement of the thumb is also weakened, and the patient may be unable to pronate forearm (palm facing down). The patient may also be unable to flex the wrist. One condition, carpal tunnel syndrome, results from compression of the median nerve within a space known as the carpal tunnel (actually, a passage formed anteriorly by the flexor retinaculum or transverse carpal ligament and posteriorly by the carpal bones). The compression may result from trauma or edema, or from continuous repetitive activities involving flexion of the wrist, such as playing an instrument or typing on a keyboard.

References:

Tortora, GJ & NP Anagnostakos. 1990. Principles of Anatomy & Physiology, 6th ed. Harper & Row. pp. 370-75.