The central spinal canal (or vertebral foramen) is first described at the different levels of the spine with its contents and the reserve space around the dura surrounding the cord to evaluate the dimensions (diameters or surface of the spinal canal). The lateral recess is then described in detail with the intervertebral foramen which together form the root canal. All these spinal canals, whatever the level, have an anteroposterior diameter which decreases in extension and increases in flexion. The fate of the various spinal canals is finally described in the case of lumbar disc herniation, degenerative spondylolisthesis or isthmic lysis, and asymmetrical discopathy, both in isolation or as part of lumbar scoliosis.