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The spinal canal, also known as the vertebral canal, is the cavity within the vertebral column that contains the thecal sac and spinal cord. The canal consists of a series of vertebral foramina (the holes at the center of the vertebra) linked with discoligamentous structures.
The spinal canal becomes progressively narrower from its superior opening at the foramen magnum to its inferior opening at the sacral hiatus 1. The canal itself is primarily formed by the vertebral foramen of adjacent vertebrae. Allowing for variation, the spinal cord occupies the superior two-thirds of the spinal canal and terminates at approximately the middle of the L1 vertebral body 2.
The canal has a typical shape depending on it's level:
- anterior: vertebral bodies, intervertebral discs, posterior longitudinal ligament
- posterior: ligamentum flavum lining the laminae
- lateral: vertebral pedicles 1
- spinal meninges
- spinal cord with its associated nerve roots and vessels (see blood supply of the spinal cord)
- epidural space