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Median nerve

 
Dental Dictionary: median nerve

n

One of the terminal branches of the brachial plexus that extends along the radial portions of the forearm and the hand and supplies various muscles and the skin of these parts.

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Sports Science and Medicine: median nerve
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The central of three nerves supplying the lower arm and hand. The median nerve runs in front of the elbow joint and passes the pronator teres muscle.

Medical Dictionary: median nerve
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n.

A nerve that is formed by the union of the medial and lateral roots from the medial and lateral cords of the brachial plexus and supplies the muscular branches in the anterior region of the forearm and the muscular and cutaneous branches in the hand.

Wikipedia: Median nerve
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Nerve: Median nerve
Nerves of the left upper extremity.gif
Diagram from Gray's anatomy, depicting the peripheral nerves of the upper extremity, amongst others the median nerve
Latin nervus medianus
Gray's subject #210 938
Innervates    Anterior compartment of the forearm (with two exceptions), Thenar eminence, Lumbricals, skin of the hand
From Lateral cord and Medial cord
MeSH Median+Nerve

The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus.

The median nerve is formed from parts of the medial and lateral cords of the brachial plexus, and continues down the arm to enter the forearm with the brachial artery.

It originates from the brachial plexus with roots from C5, C6, C7, C8, & T1.

The median nerve is the only nerve that passes through the carpal tunnel, where it may be compressed to cause carpal tunnel syndrome.

Contents

Course

Course in the upper arm and cubital fossa

After receiving inputs from both the lateral and medial roots of the corresponding cords of the brachial plexus, the median nerve courses with brachial artery on medial side of arm between biceps brachii and brachialis. At first lateral to the artery, 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, in front of the point of insertion of the brachialis muscle and deep to the biceps.

The median nerve gives off an articular branch in the upper arm as it passes the elbow joint.

Course and branches in the forearm

The median nerves arises from the cubital fossa and passes between the two heads of pronator teres. It then travels between flexor digitorum superficialis and flexor digitorum profundus before emerging between flexor digitorum superficialis and flexor carpi radialis.

The unbranched portion of the median nerve (which arises from the cubital fossa) innervates muscles of superficial and intermediate groups of the anterior compartment except flexor carpi ulnaris.

The median nerve does give off two branches as it courses through the forearm:

Branches in the 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 sends off several branches:

  • 1. Recurrent branch to muscles of the thenar compartment (the recurrent branch is also called "the million dollar nerve")[1]
  • 2. Digital cutaneous branches to common palmar digital branch and proper palmar digital branch of the median nerve which supply the:
    • a) lateral (radial) three and a half digits on the palmar side
    • b) index, middle and ring finger on dorsum of the hand

The median nerve supplies motor innervation to the first and second lumbrical muscles.

Distribution

Arm

The median nerve has no voluntary motor or cutaneous function in the (upper) arm. 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 medial two digits. The latter two muscles are supplied by the ulnar nerve.

The main portion of the median nerve supplies the following muscles:

Superficial group:

Intermediate group:

The anterior interosseus branch of the median nerve supplies the following muscles:

Deep group:

Hand

In the hand, the median nerve supplies motor innervation to the 1st and 2nd 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 side of the thumb, the index and middle finger, half the ring finger, and the nail bed of these fingers. The lateral part 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.

Injury

Injury of median nerve at different levels cause different syndromes.

  • Injury of this nerve at a level above the elbow results in loss of pronation and a reduction in flexion of the hand at the wrist.
  • Entrapment at the level of the elbow or the proximal forearm could be due to the pronator teres syndrome.
  • Injury to the anterior interosseous branch in the forearm causes the anterior interosseous syndrome.
  • Injury by compression at the carpal tunnel causes carpal tunnel syndrome.
  • Severing the median nerve can cause the hand of benediction.
  • In the hand, thenar muscles are paralyzed and will atrophy over time. Opposition and flexion of the thumb are lost. The thumb and index finger are arrested in adduction and hyperextension. This appearance of the hand is collectively referred as 'ape hand deformity'.[1]

Additional images

References

External links

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.


 
 

 

Copyrights:

Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Median nerve" Read more