Synonyms
Middle arm Medical: Median nerve
Definition
The median nerve is an important arm nerve. It takes its name from the fact that, in relation to the other two major arm nerves, the ulnar and radial nerves, it runs largely in the middle of the arm on the way from the armpit to the wrist. It consists of fibers that transport sensitive information from the skin and joints to the spinal cord and brain (sensitive afferences) and of motor fibers that send impulses from the brain to the arm muscles (motor effects).
The median nerve is one of many nerves that make up the brachial plexus, the brachial plexus. The spinal nerves from the cervical medulla of the spinal cord (C5-C8) join together immediately after exiting the spinal cord to form this nerve bundle, which is called the brachial plexus. All nerves supplying the arm emerge from this nerve bundle.
The nerves of the brachial plexus are called :
- Short branches: N. subscapularis, N. thoracodorsalis, Nn. pectoralis medialis and lateralis, N. cutaneus antebrachii medialis, Nn. intercostobrachiales
- Long branches:N. musculocutanes, N. axillaris, N. radialis, N. medianus, N. ulnaris
A nerve contains fibers that transport sensitive impulses from the skin and joints back to the brain (afferences) and at the same time fibers through which impulses are sent from the brain to the muscles (efferences).
On its way from the armpit to the fingers, the median nerve is protected by muscles. The median nerve runs from the armpit to the palm, where it divides into individual branches for the fingers. The nerve root at the plexus in the armpit is called the “medianus fork”.
On the upper arm, the nerve above the brachial artery (A. brachialis) in the pit of the humeral flexor muscle (Sulcus bicipitalis medialis) moves to the middle of the elbow. From there, it travels between the two heads of a forearm muscle (M. pronator teres ) to the forearm. There, again protected by muscle groups, it moves between the superficial and deep flexor muscles of the forearm to the wrist.
To reach the palm, the nerve with the tendons of the fingers passes through the carpal tunnel (Retinaculum musculorum flexorum). Once it reaches the palm, it divides into fibers that supply the muscles and sensitive branches. The median nerve is responsible for controlling the muscles of the forearm and fingers.
Especially for bending in the elbow joint and wrist. It is also responsible for bending the fingers and for the inward rotation (pronation) of the forearm. The most important muscles supplied are: Other muscles supplied by the N. medianus:
- Inversion muscle (M. pronator teres): Bending in the elbow joint, inward rotation of the forearm;
- Superficial finger flexors (M. flexor digitorum superficialis): Bending of the wrist and the finger base and middle joints, bending in the elbow joint;
- Deep finger flexion (M. flexor digitorum profundus): Flexion of the wrist and the base, middle and end joints of the 2nd and 3rd fingers (4th and 5th fingers are controlled by the ulnar nerve);
- Long thumb flexor (M. flexor pollicis longus): Bending in the base and end joint of the thumb.
- Wrist side flexor (M. flexor carpi radialis),
- Long palmar muscle (M. palmaris longus)
- Square inward twist (M. pronator quadratus).
The feeling of the palm of the thumb, index finger, middle finger and half ring finger is conveyed via the median nerve.
In addition, the feeling of the back of the fingers in the area of the end phalanges of the index finger, middle finger and half ring finger end phalange. The median nerve can be damaged at various points in its course. The best known is the “carpal tunnel syndrome“.
Here, the nerve is constricted as it passes through the carpal tunnel at the wrist (Retinaculum musculorum flexorum). The result is a tingling sensation and pain in the area of the sensitive supply area in the palm. Pronator teres syndrome is caused by pressure damage to the nerve between the two heads of the inward twisting muscle (pronator teres muscle).
It results in a “swearing hand” typical of the median nerve: when trying to clench a fist, the thumb, index finger and middle finger cannot be bent, while the ring and little finger can be bent.A further characteristic for such a damage is a positive “bottle sign”: it is impossible to enclose a bottle neck firmly with the hand. If, in addition to the median nerve, other nerves are also damaged, a complete brachial plexus paralysis can also occur.
