The spinal nerves are peripheral nerves arising from each side of the spinal cord. There are 31 pairs of spinal nerves, and they represent the spinal part of the peripheral nervous system (PNS).
The spinal nerves include the following structures:
- trunk of spinal nerve,
- spinal ganglion (sensory),
- anterior ramus of spinal nerve,
- posterior ramus of spinal nerve,
- communicating branch of spinal nerve,
- meningeal branch of spinal nerve.
The spinal nerves can be grouped according to the corresponding segments of the spinal cord and vertebrae:
- cervical nerves (8 pairs),
- thoracic nerves (12 pairs),
- lumbar nerves (5 pairs),
- sacral nerves (5 pairs),
- coccygeal nerves (1 pair).
The anterior rami of the spinal nerves and their branches form major nerve networks called nervous plexuses, including:
- cervical plexus,
- brachial plexus,
- lumbar plexus,
- sacral plexus,
- anococcygeal plexus.
However, the anterior rami of most of the thoracic spinal nerves do not form a plexus, instead they are called the intercostal nerves and they run along the intercostal spaces.