The spine is made up of 33 bones or vertebrae. The vertebrae have two main functions. One is to provide anchorage for muscles so that we can move as the brain dictates to those muscles. The other is to provide protection to the spinal cord.
The Neural Tube
The central nervous system and spine develops between the 14th and 23rd day after conception. Spina bifida occurs when the neural tube fails to close correctly. The vertebrae also fail to close in complete rings around the affected portion of the spinal cord. This leaves a gap posteriorly (at the back), involving one or more vertebrae. The fault may occur in one or more of the vertebrae but it is most common around waist-level.