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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, [1] and has contributions from ventral roots of C6-C7 (lateral cord) and C8 and T1 (medial cord). [1] [2]
The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbricals. The ulnar nerve innervates the remaining intrinsic muscles of the hand. [3] [4] All muscles of the hand are innervated by the brachial plexus (C5–T1) and can be classified by innervation: [1] [4] [5]
In the human body, the carpal tunnel or carpal canal is a flattened body cavity on the flexor (palmar/volar) side of the wrist, bounded by the carpal bones and flexor retinaculum. It forms the passageway that transmits the median nerve and the tendons of the extrinsic flexor muscles of the hand from the forearm to the hand. [1]
In human anatomy, the main role of the carpal bones is to articulate with the radial and ulnar heads to form a highly mobile condyloid joint (i.e. wrist joint), [1] to provide attachments for thenar and hypothenar muscles, and to form part of the rigid carpal tunnel which allows the median nerve and tendons of the anterior forearm muscles to be ...
In the palm of the hand, the median nerve is covered by the skin and the palmar aponeurosis, and rests on the tendons of the Flexor muscles.Immediately after emerging from under the transverse carpal ligament the median nerve becomes enlarged and flattened and splits into a smaller, lateral, and a larger, medial portion.
The ulnar nerve is exclusively responsible for the innervations of the hypothenar eminence. Both nerves contribute to the innervations of the midpalmar group. [8] The innervation of these muscles by the median nerve is unusual, as most of the intrinsic muscles on the palm of the hand are supplied by the ulnar nerve.
The third and fourth lumbricals (most ulnar two) are innervated by the deep branch of ulnar nerve. [5] This is the usual innervation of the lumbricals (occurring in 60% of individuals). However 1:3 (median:ulnar - 20% of individuals) and 3:1 (median:ulnar - 20% of individuals) also exist.
It is innervated by the ulnar nerve in 50% of people and by both the median and ulnar nerves in 15%. The opponens pollicis originates on the tubercle of the trapezium and the flexor retinaculum. It is inserted onto the radial side of the first metacarpal. It opposes the thumb and assists in adduction. It is innervated by the median nerve. [6]