Which innermost layer of the meninges is the pia mater?

• A. Dura mater
• B. Arachnoid mater
• C. Pia mater
• D. Subarachnoid space

Answer: (C)

The innermost membrane that directly covers the brain and spinal cord is the pia mater. It is a very thin, highly vascular layer that adheres tightly to the brain’s surface, following every contour, including the folds of the gyri and sulci. This close contact with neural tissue is what makes the pia mater the deepest protective layer. Just outside it lies the subarachnoid space, which contains cerebrospinal fluid and is not a distinct layer. Above the pia is the arachnoid mater, the middle membrane, and outside of that is the dura mater, the tough outer layer.