Median nerve
The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has contributions from ventral roots of C5-C7 (lateral cord) and C8 and T1 (medial cord). The median nerve is the only nerve that passes through the carpal tunnel. Carpal tunnel syndrome is the disability that results from the median nerve being pressed in the carpal tunnel. Structure. The median nerve arises from the branches  from lateral and medial cords of the brachial plexus, courses through the anterior part of arm, forearm, and hand, and terminates by supplying the muscles of the hand. Arm. After receiving inputs from both the lateral and medial cords of the brachial plexus, the median nerve enters the arm from the axilla at the inferior margin of the teres major muscle. It then passes vertically down and courses lateral to the brachial artery between biceps brachii (above) and brachialis (below). At first, it is lateral to the artery and lies anterior to the shoulder joint; it then crosses anteriorly to  run medial to the artery in the distal arm and into the cubital fossa. Inside the cubital fossa, the median nerve passes medial to the brachial artery. The median nerve gives off an articular branch to the elbow joint. A branch to pronator teres muscle arise from the median nerve immediately above the elbow joint. Forearm. The median nerve continues in the cubital fossa medial to the brachial artery and passes between the two heads of the pronator teres, deep to the bicipital aponeurosis (aponeurosis of biceps) and superficial the brachialis muscle. It crosses the ulnar artery (branch of brachial  artery) while being separated by the deep head of the pronator teres. It then travels between the flexor digitorum superficialis (above) and flexor digitorum profundus (below). The median nerve is accompanied by the median artery (a branch of anterior interosseous artery) during this course. Then, about 5 cm above the flexor retinaculum (wrist), it emerges between the flexor digitorum superficialis (medially) and the flexor carpi radialis (laterally) into the hand. The main trunk of the median nerve innervates the superficial and deep groups of the muscles in the anterior compartment of the forearm with the exception of flexor carpi ulnaris . The median nerve does this by giving off two branches as it courses through the forearm: The median nerve also gives off sensory and other branches in the forearm. The palmar cutaneous branch of the median nerve arises at the distal part of the forearm. It supplies sensory innervation to the thenar eminence of the palm and the central palm. Articular branches are given to the elbow joint and proximal radioulnar joint. Vascular branches supply the radial and ulnar arteries. Meanwhile, a communicating branch is given to the ulnar nerve. Hand. The median nerve enters the hand through the carpal  tunnel, deep to the flexor retinaculum along with the tendons of flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. From there, it is divided into recurrent muscular branch and digital cutaneous branch: Variation. The naturally occurring anomalies of the median nerve are: Function. The median nerve is the main nerve of the front of the forearm. It supplies the muscles of the front of the forearm and muscles of the thenar eminence, thus controlling the coarse movements of the hand. Therefore, it is also called "labourer's nerve". 3. The median nerve has no voluntary motor or cutaneous  function in the brachium. It gives vascular branches to the wall of the brachial artery. These vascular branches carry sympathetic fibers. Forearm. It innervates all of the flexors in the forearm, except flexor carpi ulnaris and that part of flexor digitorum profundus that supplies the fourth and fifth digits. The latter two muscles are supplied by the ulnar nerve (specifically the muscular branches of ulnar nerve). The main portion of the median nerve supplies these muscles: Superficial group: Intermediate group: The anterior interosseus branch of the median nerve supplies these muscles: Deep group: Hand. In the hand, the median nerve  supplies motor innervation to the first and second lumbrical muscles. It also supplies the muscles of the thenar eminence by a recurrent thenar branch. The rest of the intrinsic muscles of the hand are supplied by the ulnar nerve. The median nerve innervates the skin of the palmar (volar) side of the index finger, thumb, middle finger, and half the ring finger, and the nail bed. The radial aspect of the palm is supplied by the palmar cutaneous branch of the median nerve, which leaves the nerve proximal to the wrist creases. This palmar cutaneous branch travels in a separate  fascial groove adjacent to the flexor carpi radialis and then superficial to the flexor retinaculum. It is, therefore, spared in carpal tunnel syndrome. Clinical significance. Injury. Injury of median nerve at different levels causes different syndromes with varying motor and sensory deficits. At the shoulder. Above the elbow At the elbow Within the proximal forearm: Anterior interosseous syndrome At the wrist Within the wrist: Carpal tunnel syndrome