Spinal nerve

A spinal nerve (nervus spinalis), and spinal cord ( s ) called nerve, is associated on its front and rear root of one side of a specific spinal cord segment nerve. The spinal part of the peripheral nervous system. Between each two vertebrae a pair of spinal nerves exits the spinal canal. Humans have a total of (usually) 31 paired spinal nerves.

Number of spinal nerves

The naming of the individual spinal nerves corresponding to their spinal cord segment and also follows from the spinal regions from which they originate, they exit. The pair of top two spinal nerves exits just below the occipital, ie above the first cervical vertebra. Since the exiting below the seventh cervical vertebra Spinalnervenpaar (C8 ) is still associated with the neck region, there are eight cervical spinal nerves because in only seven cervical vertebrae. The further caudally following spinal nerves then carry the same names and numbers as the overlying vertebral body. Overall, therefore, arise when people usually

  • Neck: 8 cervical pairs of nerves, C1 - C8
  • Chest: 12 thoracic pairs of nerves, Th1 - Th12
  • Lumbar region: 5 lumbar pairs of nerves, L1 -L5
  • Sacral region: 5 sacral nerve pairs, S1 -S5
  • Tailbone area: (mostly) 1 kokzygeales pair of nerves, Co1

Deviations are not rare; may also occur in connection with malformations of the spine.

Shares of a spinal nerve

Spinal nerves are formed by combining each of efferent and afferent a nerve root that leave the spinal cord at various points and present initially still spatially separated in the spinal canal. This recognition goes to Charles Bell and François Magendie back ( Bell - Magendie law).

The afferent units transmit information from inside the body and from the body surface to the spinal cord. Their cell bodies lie in the dorsal root ganglion ( spinal ganglion ), which is located in the intervertebral foramen. Their axons pass through the dorsal root, Radix posterior ( in animals dorsal root ) in the gray matter of the spinal cord or the white matter to the brain where further processing takes place.

The leading to muscle motor efferent axons of the motor neurons. Their somata are located in the gray matter of the spinal cord. The motoneurons of a muscle are loosely grouped in the form of a spindle-shaped nucleus in the anterior horn of the spinal cord. The efferent fibers of a core can thereby escape through various nerve roots. Considered over the whole length of the spinal cord, these cores are the so-called motor core-column. In each segment, enter efferent axons of the ventral root, radix anterior / ventralis, from the spinal cord and unite with the incoming afferents to a common Spinalnervenstamm (truncus nervi spinalis).

In the field of thoracic and lumbar part of the spinal cord, there are also sympathetic root cells. They are located in the nucleus of the intermediolateral gray matter and also pull in the ventral root to the trunk nervi spinalis. Over a white connecting branch ( communicating branch albus) then they pull the sympathetic chain ganglia in which some of the fibers is switched to the so-called second neuron. The switched shares typically draw in a gray connecting branch ( communicating branch griseus ) back to a Spinalnervenstamm back.

In the field of cross- cord there is parasympathetic root cells. These efferents also draw on the common Spinalnervenstamm. They supply the lower abdominal and pelvic viscera.

Course outside of the spinal canal

The celiac nervi spinalis leaves the vertebral canal through the intervertebral foramen ( intervertebral foramen ) and then branches off into several branches on each:

  • Posterior ramus ( ramus dorsalis) for the supply of spine -related skin and muscles ( autochthonous back muscles ).
  • Anterior branch ( ramus ventralis ) for the supply of the skin and muscles of the spine far back, as well as the lateral and ventral parts of the body.
  • Communicating branch albus and communicating branch griseus visceroefferenter for routing and visceroafferenter information
  • Ramus meningeus for the innervation of spinal meninges

The area of ​​skin supplied by one spinal nerve is called a dermatome, the muscles supplied as myotome.

Plexus

Particularly in the area of the limbs origins form the anterior rami / ventral spinal nerve plexus ( plexus ) with their neighbors. Fibers can mix several spinal cord segments and in turn shapes nerves. Each of these Plexusnerven thus has interests held by several spinal cord segments. Hence it is only in case of failure of nerve root or spinal nerves does not lead to a complete paralysis ( paralysis ) of the muscles supplied, but only to a more or less pronounced loss of strength ( paresis ).

Nucleus (neuroanatomy) Sympathetic trunk Axonotmesis Integrated Authority File
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