Arachnoidea

The arachnoid is one of the three layers surrounding the brain and spinal cord, collectively called the meninges. It is a thin, web-like membrane located between the outer dura mater and the inner pia mater. The arachnoid acts as a protective barrier and contains a space called the subarachnoid space, filled with cerebrospinal fluid, which cushions and nourishes the central nervous system. Its structure helps prevent injuries and infections, maintaining a stable environment for the brain and spinal cord.