The spine is made up of a column of 24 vertebrae that are stacked on top of one another and form a protective bony covering for the spinal cord and provide the framework and support for the body. Between the vertebrae lies the intervertebral disc. The disc is the shock absorber of the spine and is composed of an inner gelatinous layer called the nucleus pulposus and the outer layer called the annulus fibrosus. The outer layer is tough and helps the intervertebral disc to withstand pressure from the wear and tear of daily life.
Between the vertebrae of each spinal segment are the facet joints. These are the joints connecting the back of the spine. It is the alignment of facet joints that allow for mobility of the spine.
Along the side of each vertebrae are openings that allow for the passage of nerves directly from the spinal column. These nerve bundles provide motor and sensory function to all areas of the body. Each exiting nerve bundle typically affects only a certain region of the body. For example, a nerve bundle exiting from the neck will provide nerve function for the upper extremities, while a nerve bundle exiting from the lower back will provide nerve function to the lower extremities. Typically, the function of each nerve bundle follows a particular path or pattern in the body.