The spinal canal is a hole that runs lengthwise down the center of the vertebral column. The spinal cord and the meninges (coverings around the spinal cord) pass through the spinal canal. The spinal canal also contains fat and blood vessels, as well as the spinal nerve roots.
The front part of the spinal canal is bordered by the back of the vertebral bodies, which includes the back of the intervertebral discs. The back part of the canal is bordered by the ring of bone on the back of the vertebra.
Ligaments (strong bands of connective tissue that hold bones together) also form part of the spinal canal. The ligamentum flavum is a ligament located in the spaces between the lamina of the vertebrae. This ligament contributes to part of the back of the spinal canal. (It also helps protect the disc from injury by limiting the spine's ability to bend forward.)
The posterior longitudinal ligament runs down the back side of the bodies. It helps bind the vertebrae into one long unit. Similar to the ligamentum flavum, the posterior longitudinal ligament plays a role in protecting the discs from injury.