Median nerve

Synonyms

Mittelarmner

Medically: Nervus medianus

Median nerve

definition

The median nerve is an important arm nerve. He gets his name from the fact that he runs in the middle of the arm on the way from the armpit to the wrist in relation to the remaining two large arm nerves, Nervus Ulnarius and Nervus Radialis.
It consists of fibers that carry sensitive information from the skin and joints to the spinal cord and brain ( sensitive afferents ) and motor fibers that send impulses from the brain to the arm muscles (motor efferents).

origin

The median nerve is one of many nerves in the brachial plexus, the brachial plexus .
The spinal cord nerves from the cervical spinal cord (C5-C8) immediately after emerging from the spinal cord assemble to form this bundle of nerves called the brachial plexus ( brachial plexus ).
From this bundle of nerves all the nerves that supply the arm come out.
The nerves of the nerve bundle ( brachial plexus ) are called:

  • Short branches:
    N.subscapularis, N. thoracodorsalis, N. medialis and lateral medialis, N. cutaneus antebrachii medialis, N.intercostobrachialis;
  • Long branches:
    N.musculocutanes, N. axillaryis, N. radialis, N. medianus, N. ulnaris

Overview and classification

A nerve contains fibers that carry sensory impulses back from the skin and the joints to the brain ( afferents ) and at the same time fibers that send impulses from the brain to the muscles (efferents).
On its way from the armpit to the fingers, the median nerve is protected by muscles.

Anatomy and course

nervus medianus

The median nerve runs from the armpit to the palm, where it divides into individual branches for the fingers. The nerve root on the arm nerve plexus in the armpit is called the "median fork". In the upper arm, the nerve above the brachial artery ( A.brachialis ) in the pit of the upper arm flexor ( medial sulcus bicipitalis ) pulls to the middle of the elbow.
From there he pulls protected between the two heads of a forearm muscle ( M.pronator teres ) to the forearm. There, again protected by muscle groups, he pulls between the superficial and the deep flexor muscles of the forearm to the wrist.
To reach the palm of the hand, the nerve pulls the tendons of the fingers through the carpal tunnel (flexor retinaculum ). Once in the palm of the hand, it divides into fibers that feed the muscles and into sensitive branches.

Physiology (motor skills)

The median nerve is responsible for controlling the muscles of the forearm and fingers. Especially for bending in the elbow joint and wrist. In addition, for the flexion of the fingers and inward rotation (pronation) of the forearm.
The main muscles supplied are:

  • Inverting muscle ( M.pronator teres ): flexion in the elbow joint, inward rotation of the forearm;
  • Superficial digital flexor flexors ( flexor digitorum superficialis ): flexion of the wrist and of the finger base and middle joints, flexion in the elbow joint;
  • Deep flexor digitorum ( flexor digitorum profundus ): flexion of the wrist and the finger base, middle and end joints of the second and third fingers (4th and 5th fingers are driven by the N. involaris);
  • Long thumb flexor ( M.flexor pollicis longus ): flexion in the base of the thumb and the ankle.

Other muscles supplied by the median nerve:

  • Wrist- side tilter ( M. flexor carpi radialis ),
  • Long hollow muscle ( M.palmaris longus )
  • Square inward turner ( M.pronator quadratus ).

Physiology (sensitivity)

The feeling of the palm of the thumb, the index finger, the middle finger and half the ring finger are conveyed via the median nerve. In addition, the feeling of the finger back in the area of ​​the end links of the index finger, the middle finger and the half ring finger end link.

damage

The median nerve can be damaged at various points in its course. The best known is the "carpal tunnel syndrome". The nerve is narrowed as it passes through the carpal tunnel on the wrist (flexor retinaculum ). There are tingling sensations and pain in the area of ​​the sensitive supply area in the palm of the hand.
The "Pronator-Teres syndrome" arises when pressure on the nerve between the two heads of the inward- turning muscle ( M. pronator teres ). It comes to a medusa for the typical "Schwurhand": in the attempt to clench a fist, thumb, index finger and middle finger can not bend, while ring and small fingers can bend. Another characteristic of such damage is a positive "bottle sign": it is impossible to tightly enclose a bottleneck by hand. If other nerves are damaged in addition to the median nerve, it can also lead to complete brachial plexus plexus.


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