Cross-Sectional Anatomy of the Spinal Cord. (a) Relationships to the vertebra, meninges, and spinal nerve. (b) steal of the spinal cord, meninges, and spinal nerves, (c) cross section of the liar spinal cord with spinal nerves The spinal cord and brain are enclosed in three fibrous membranes called meninges. They separate the soft tissue of the CNS from the bones of the vertebrae and skull. From superficial to deep, they are the dura mater, arachnoid mater, and pia mater