Which space lies between the arachnoid mater and pia mater and contains cerebrospinal fluid?

• A. Subdural space
• B. Epidural space
• C. Subarachnoid space
• D. Arachnoid mater

Answer: (C)

CSF circulates in a space that lies between two delicate membranes around the brain and spinal cord. This space, the subarachnoid space, sits between the arachnoid mater and the pia mater and is filled with cerebrospinal fluid, which cushions the CNS and helps maintain chemical stability. CSF is produced by the choroid plexus, flows through the ventricles, and enters this space where it can bathe the brain and spinal cord before being reabsorbed into the venous system. The other spaces mentioned are not the CSF-filled gap described: the subdural space is a potential gap between the dura and arachnoid; the epidural space lies between the skull or vertebrae and the dura; and the arachnoid mater is a membrane itself, not a space.