Final answer:
The brain and spinal cord are protected by three membranes collectively known as the meninges, which include the dura mater, arachnoid mater, and pia mater, with cerebrospinal fluid circulating between them for additional protection.
Step-by-step explanation:
The brain and spinal cord are protected and cushioned by three connective tissue membranes that are collectively called the meninges. These layers consist of the dura mater, the arachnoid mater, and the pia mater. The dura mater is the outermost, tough layer that encapsulates the central nervous system (CNS), providing significant protection. Below the dura mater lies the arachnoid mater, a web-like layer that includes the arachnoid trabeculae, resembling a spider web. The innermost layer is the pia mater, which is a delicate membrane that closely adheres to the surface of the brain and spinal cord. The space between the arachnoid and pia maters is filled with cerebrospinal fluid (CSF), which provides additional cushioning, buoyancy, and facilitates the circulation of nutrients and waste removal.