Thecal sac, dural sac | |
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Anatomical terminology |
The thecal sac or dural sac is the membranous sheath (theca) or tube of dura mater that surrounds the spinal cord and the cauda equina. The thecal sac contains the cerebrospinal fluid which provides nutrients and buoyancy to the spinal cord.[1] From the skull the tube adheres to bone at the foramen magnum and extends down to the second sacral vertebra where it tapers to cover over the filum terminale. Along most of the spinal canal it is separated from the inner surface by the epidural space.[2] The sac has projections that follow the spinal nerves along their paths out of the vertebral canal which become the dural root sheaths.[3]