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Spinal Anatomy - Part 4

Spinal Nerves

A network of thirty-one pairs of nerves continue throughout the body from the spinal cord. These nerves are responsible for controlling all sensation and movement within the body by communicating messages to and from the brain.

Within each spinal nerve are two roots:

  • Ventral - transmits motor impulses from the brain
  • Dorsal - transmits sensory impulses to the brain

These two roots fuse together and form the spinal nerve, which runs through the spinal canal alongside the spinal cord, until it reaches the intervertebral foramen. After the nerve exits the foramen, it branches out, each branch containing both motor and sensory elements. The smaller branch (posterior primary ramus) turns back, or toward the posterior, to provide nerves to the skin and muscles to the posterior of the body. The bigger of the two (anterior primary ramus) takes a different path, toward the front of the body. It supplies the skin and muscles of the front of the body, creating the largest amount of the major nerves.

Similar to the vertebrae, the spinal nerves are numbered. The numbers correspond with the vertebra above where the nerve exits ( the foramen)from the spinal canal. For instance, the 8 spinal nerves in the cervical spine are C1-C8, the 12 thoracic nerves are T1-T12, the lumbar spinal nerves are L1-L5, and the 5 sacral spinal nerves are S1-S5. Lastly, there is 1 cocygeal nerve.

A Dermatome pattern (a striped pattern across the body which shows which nerve is associated with sensory and motor control in that area) indicates which spinal nerves are responsible for feeling or pain in specific areas of the body. Doctors can determine the location of a problem within the spine based upon the area of pain, or weakness in the muscle. Sciatica most often is caused by a pinching or injury to the L4-S3 nerve.

Coverings and Voids of the Spine

The membranes that cover the spine are the same as the membranes which cover the brain: the meninges. “Meningitis” refers to an inflammation of the meninges. These membranes are:

  • Pia Mater
  • Arachnoid Mater
  • Dura Mater

Attached to the spinal cord is the inner membrane, or the pia mater. The next membrane is the arachnoid mater. The resilient dura mater is the outer membrane. In between these membranes are voids, or spaces, which are used in diagnostic or treatments of conditions.

The cerebrospinal fluid (CSF) is contained in the subarachnoid space which surrounds the spinal cord, and is situated between the pia and arachnoid mater. Most often, a lumbar puncture will be located in the subarachnoid space while sampling or testing CSF while performing a myelogram or injecting contrast dye for X-Ray visibility during a procedure.

The space between the dura mater and bone is called the epidural space. Numbing agents like epidurals and medications like steroids, are injected into the epidural space.

Dr. Badlani

Dr. Badlani is dedicated to educating our patients about their condition, to provide a complete understanding of the spine and how they can help heal themselves with exercise, therapy, and all, including minimally invasive, surgical and non-surgical options. Contact us today for a full evaluation if you are experiencing back pain or discomfort.