spinalnervernas

Spinal nerves (spinalnervernas) are mixed peripheral nerves that arise from the spinal cord. Each spinal nerve is formed by the union of a dorsal root, which carries sensory information to the spinal cord, and a ventral root, which transmits motor signals away from the spinal cord. There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each nerve exits the vertebral column through an intervertebral foramen. In the cervical region, nerves C1–C7 exit above the corresponding vertebrae, C8 exits below C7, and all subsequent nerves exit below the same-numbered vertebra.

After exiting, the spinal nerve divides into dorsal and ventral rami. The dorsal ramus supplies the muscles and skin of the back, while the ventral ramus supplies the anterolateral trunk and the limbs. In the thorax, ventral rami become intercostal nerves; in other regions they contribute to major nerve networks known as the cervical, brachial, lumbosacral, and sacral plexuses. Spinal nerves carry different fiber types, including general somatic afferent and efferent fibers, as well as general visceral afferent and efferent fibers for certain targets.

Clinical relevance: nerve irritation or compression along a spinal nerve causes radicular pain and sensory changes in a dermatomal pattern corresponding to its distribution; motor signs may accompany weakness in the associated myotome. Common causes include disc herniation, spinal stenosis, or trauma. Knowledge of spinal nerve anatomy underpins diagnostic procedures, regional anesthesia, and neuromuscular rehabilitation.