Which layer of the meninges is the outermost and very tough?

The outermost layer of the meninges is the dura mater, which serves as a protective covering for the brain and spinal cord. The dura mater is known for its toughness and resilience, providing a crucial barrier against physical impacts and infections. This thick and durable layer is composed of dense connective tissue, which helps to safeguard the underlying structures of the central nervous system.

In contrast, the pia mater, which is the innermost layer, is much thinner and delicate, closely adhering to the surface of the brain and spinal cord. The arachnoid mater, situated between the dura and pia maters, has a web-like appearance and is more protective, but still not as tough as the dura mater. Cerebrospinal fluid, which is not a meninges layer, is present in the space between the arachnoid and pia mater, cushioning the brain and spinal cord but does not contribute to the structural protection provided by the meninges themselves.

Therefore, the identification of the dura mater as the outermost and very tough layer reflects its crucial role in protecting the central nervous system.