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Components of a Spinal Nerve

As part of the peripheral nervous system, spinal nerves provide communication between parts of the body and the central nervous system. There are 31 pairs of spinal nerves that are grouped by the region of the spine from which they originate. There are eight pairs of cervical spinal nerves, 12 pairs of thoracic spinal nerves, five pairs each of lumbar and sacral spinal nerves, and one pair originating from near the tailbone. Each spinal nerve is made up of a dorsal and ventral root; dorsal and ventral branches; paravertebral ganglion; and in the thoracic and lumbar regions, a visceral branch.

  1. Dorsal Root

    • The dorsal root, also called the posterior or sensory root, of a spinal nerve conducts impulses from parts of the body to the central nervous system. It extends from the spinal cord, the part of the central nervous system that begins at the brainstem and extends through the spine, and merges with the ventral root, forming a spinal nerve. The nerve then passes through the vertebral canal via the intervertebral foramen of the vertebrae.

    Ventral Root

    • The ventral root sends impulses from the central nervous system to its corresponding parts of the body. It is also called the anterior or motor root.

    Dorsal Branch

    • Depending on the region of the spine, each spinal nerve splits into three or four branches. The dorsal branch is present in spinal nerves of all regions. This branch supplies nerves to the skin and muscles of the back side of a person's body.

    Ventral Branch

    • The ventral branch of a spinal nerve is also present in all regions of the spine. This branch reaches forward and supplies nerves to the muscles and skin of the front side of the body.

    Visceral Branch

    • The visceral branch, which is present only in the nerves of the thoracic and lumbar regions of the spine, supplies nerves to internal organs. Because of this responsibility, this branch is part of the autonomic nervous system.

    Paravertebral Ganglia

    • The paravertebral ganglia run perpendicular to all of the spinal nerves, forming a chain of nerves. They also help to regulate the visceral ganglia that control internal organ processes.

    Meningeal Branch

    • The meningeal branch of a spinal nerve curves back around and reenters the intervertebral foramen and the vertebral canal, supplying nerves to the meninges--a protective membrane that covers the brain and spinal cord--blood vessels, vertebrae and intervertebral ligaments of the spine.

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