The covering of the central nervous system is called meninges. The meninges are made up of three membranes or screens. These are-
(i) Dura Matter : The outer layer of meninges is called dura matter. The dura mater is bilayered in the brain and unilayered in the spinal cord. It contains veins and sinuses.
(ii) Arachnoid Matter : The second layer of meninges is called arachnoid matter. It is transparent and thin. Between the dura mater and the arachnoid mater lies the subdural space. It is filled with fluid
(iii) Pia mater: The innermost layer of meninges is called pia mater. It is thin, transparent and vascular. Between the arachnoid mater and the pia mater lies the subarachnoid space. It is filled with a fluid called Cerebro Spinal Fluid (CSF).