Which layer of the meninges is the outermost?

The outermost layer of the meninges is the dura mater. This thick and durable membrane plays a vital protective role, providing a tough barrier that surrounds the brain and spinal cord. Its primary function is to safeguard the central nervous system from injury. Additionally, the dura mater is crucial in supporting the structures associated with the brain and spinal cord, as it is involved in the formation of sinuses that help drain cerebrospinal fluid.

In contrast, the arachnoid mater lies beneath the dura mater and serves as a web-like layer that houses the cerebrospinal fluid. The pia mater is the innermost layer, composed of delicate tissue that closely follows the contours of the brain and spinal cord, providing further protection. The subdural space is not a layer but rather a potential space between the dura mater and arachnoid mater, which may become relevant in certain medical conditions but does not constitute a meninges layer itself. Thus, the dura mater is rightly recognized as the outermost layer among these options.