The spinal cord lies within the spinal canal, formed by the vertebral bodies and the bony arch formed by the pedicles and laminae (see M6).
The cord and its terminal nerves, the cauda equina, lie within the dural sac, a tough membranous structure filled with cerebrospinal fluid bathing and protecting the cord.
The spinal cord itself ends at the level of the first lumbar vertebra, but nerve roots travel inside the dural sac to exit at lower levels; these roots form the cauda equina (”horse’s tail”).
Blood supply comes from the segmental branches of the aorta, traveling along the nerve root to emerge as the anterior spinal artery running in the front midline of the cord; there are two parallel vessels along the back surface of the cord. There is also a generous venous plexus within the canal.