Final answer:
The middle layer of the meninges is known as the arachnoid mater, which is a web-like layer that supports the cerebrospinal fluid and facilitates its circulation and drainage in the central nervous system.
Step-by-step explanation:
The middle layer of the meninges is called the arachnoid mater. This layer is named for its spider-web-like structure, which consists of trabeculae situated between it and the pia mater. The arachnoid mater forms a sac around the central nervous system (CNS) and supports the cerebrospinal fluid (CSF) that circulates in the subarachnoid space.
The CSF is crucial for cushioning the brain, providing a shock absorber, and facilitating the circulation of nutrients and removal of waste. The arachnoid mater is also involved in filtering CSF through arachnoid granulations into the dural sinuses for drainage from the nervous system.