The meninges are the brain’s protective outer covering made of three membranes. They surround the brain and spinal cord, helping protect the central nervous system and enclosing cerebrospinal fluid.
From the outside inward, the three layers are the dura mater, arachnoid mater and pia mater. The dura is tough and relatively thick. The arachnoid has a web-like structure, and the subarachnoid space beneath it contains cerebrospinal fluid and many blood vessels. The pia mater is a delicate layer that closely follows the brain’s surface.
The meninges also form specialized structures such as dural venous sinuses, which help drain blood from the brain. Inflammation of these membranes is called meningitis, a potentially serious condition caused by infections or other agents.
The meninges are not the same as the blood–brain barrier. The barrier is a selective property of blood vessels and supporting cells, whereas the meninges are anatomical coverings.