What does the pia mater do?

The pia mater is the innermost layer of the meninges, which are the protective coverings of the brain and spinal cord. Its primary function is to closely adhere to the surface of the brain, molding to every tiny crook and crevice. This intimate connection allows the pia mater to provide a supportive and protective environment for the central nervous system, and it plays a vital role in the overall structure of the brain.

This layer also is involved in the support of blood vessels that supply the brain, but its main defining characteristic is its close association with the brain's surface, providing both a barrier and a conduit for nutrients. The other options describe functions that are attributed to broader systems or other layers of protection, but do not accurately characterize the unique role of the pia mater in relation to the brain.