Spinal Nerves: Anatomy

Spinal nerves are mixed nerves that originate from the spinal cord.

A typical nerve begins as dorsal roots having sensory fibers and ventral roots containing motor fibers.

These roots merge, forming a spinal nerve that exits the vertebral column through the intervertebral foramen.

The spinal nerve further divides into a smaller posterior ramus and a large anterior ramus.

The posterior ramus serves the muscles and skin of the posterior side of the torso. In contrast, the anterior ramus serves the limbs, skin, and muscles of the anterior and lateral sides.

Tiny meningeal branches reenter the vertebral column to supply the vertebrae, associated ligaments, and spinal cord-associated blood vessels.

There are 31 pairs of spinal nerves, numbered according to the vertebrae they exit. These include eight cervical, twelve thoracic, five lumbar, five sacral, and one coccygeal nerve.

Except for T2 to T12, the axons of the anterior rami of the adjacent spinal nerves form networks or plexuses before innervating the body parts.

The major nerve plexuses include the cervical, brachial, lumbar, sacral, and coccygeal plexuses.