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Spinal nerve

German: Spinalnerv

1 Definition

The spinal nerves are the nerves that spring up from the spinal cord. They are part of the peripheral nervous system.

2 Anatomy

The spinal nerves develop in the spinal canal from the fila radicularia of the anterior and posterior nerve roots, which insert into the spinal cord, or leave the spinal cord, respectively. They are also called Radix anterior (anterior root) and Radix posterior (posterior root). In the posterior root, there is a dorsal root ganglion interpolated.

In the upper part of the spine, they leave the spinal canal immediately after that via the intervertebral foramina. In the lower part, they pass towards the caudal pole over a longer distance within the dural sac as cauda equina at first, before they leave the spinal canal.

2.1 Branches

Outside the spinal canal, the spinal nerves divide into 3-4 branches. One can differentiate between:

  • Anterior branch (also: ventral root): The anterior branch of the spinal nerves serves the sensitive and motor supply of the skin and muscles of the ventral side of the torso as well as - via plexus - of the skin and muscles of the limbs.
  • Posterior branch (also: dorsal root): The posterior branch of the spinal nerves serves the sensitive and motor supply of the skin of the back and the dorsal muscles.
  • Communicans branch (ramus communicans): It serves the forwarding of the visceroafferent and visceroefferent nerve fibers.
  • Meningeal branch: A recurrent branch that provides the sensitive innervation of the meninges, the facet joints, the periosteum of the spinal canal, and the posterior part of the anulus fibrosus of the intervertebral disc of the corresponding segments.

2.2 Number

In total, there are 31 paired spinal nerves. These nerves are mixed nerves that contain motor, sensitive, and vegetative components:

2.3 Plexus formation

In the region of the origins of the limbs, the anterior branches of the spinal nerves form so-called nervous plexuses. There, the nerve fibers of different spinal nerves mix and finally form nerves that contain parts of several spinal cord segments. These nervous plexuses comprise:

2.4 Particularities

Some branches of the spinal nerves have their own anatomical names. The dorsal root of the first spinal nerve for example is also called suboccipital nerve. The thickest branch of the dorsal root of the second spinal nerve is called major occipital nerve.

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