The human spine is the upright longitudinal axis of the body and consists of 26 vertebrae (7 cervical, 12 thoracic, 5 lumbar and sacrococcygeal). The vertebrae have different shapes but are generally the same, including vertebral bodies, pedicles, foramina, plates, and small joints. Each vertebral body is separated by an intervertebral disc that acts as a cushion. The intervertebral disc consists of a central nucleus pulposus and a surrounding annulus fibrosus. The intervertebral disc is a tissue that is susceptible to injury and degeneration. The discs, bone tissue, ligaments and muscle tissue work together to support the stability of the spine. The posterior foramina of each vertebra are interconnected to form a top-to-bottom spinal canal through which the spinal cord or cauda equina passes. The spinal cord carries the nerve connections to the brain and trunk. The nerve roots branch out from the spinal cord and are responsible for the nerve connections between the spinal cord and the trunk and viscera. There are 31 pairs of nerve roots that control muscle movement, skin sensation and reflexes in different areas. Spinal disorders often involve the spinal cord and nerve roots. This can lead to muscle weakness, sensory paralysis, and in severe cases, incontinence and even paralysis.