The spine is composed of 33 individual vertebrae that interlock to form a column. The spine consists of seven cervical, twelve thoracic, and five lumbar vertebrae, in addition to five fused vertebrae of the sacral region and four fused vertebrae forming the coccyx. Vertebrae are interconnected by joints for motion in the spine and discs separate them to provide for weight bearing and torsion. The entire length of the spinal column has a large central canal through which the spinal cord descends. The spine is designed to be incredibly strong, supporting the structures of the body and protecting the highly sensitive nerve roots of the spinal cord. The spine is also highly flexible, providing for mobility on different planes.