leptomeninges

The leptomeninges are the two innermost meninges, the pia mater and the arachnoid. These membranes surround the brain and spinal cord and, along with the dura mater, protect the central nervous system. The pia mater is a thin, vascular membrane that adheres directly to the surface of the brain and spinal cord. The arachnoid is a delicate, web-like membrane that lies over the pia mater, separated by the subarachnoid space. This space is filled with cerebrospinal fluid (CSF), which acts as a cushion and shock absorber for the central nervous system. The CSF also helps maintain constant pressure within the cranium and transports waste products away from the brain and spinal cord.1234