Final answer:
The meninges are the three-layered membrane that covers and protects the brain and spinal cord. They consist of the durable dura mater, the web-like arachnoid mater, and the thin pia mater, with cerebrospinal fluid circulating in the spaces between. The correct answer is C. Meninges.
Step-by-step explanation:
Protective Membranes of the CNS
The three-layered membrane that covers the brain and spinal cord and is known as the meninges serves a critical role in the protection of our central nervous system. The meninges consist of three distinct layers:
- Dura mater, the outermost layer, is a thick and durable membrane that provides strong protection. It is anchored to the cranium and vertebral cavity and includes vein-like structures that carry blood back to the heart.
- The middle layer, called the arachnoid mater, is a web-like membrane that forms a sac around the central nervous system. Beneath it is the arachnoid trabeculae, resembling a spider web, hence the name.
- The innermost layer is the pia mater, which is a delicate and thin membrane that closely conforms to the contours of the brain and spinal cord. It serves as a fluid-impermeable layer that safeguards the central nervous tissue.
The space between the arachnoid mater and the pia mater contains cerebrospinal fluid (CSF), which cushions the brain and spinal cord, provides buoyancy, and circulates nutrients while removing waste.
Therefore, the correct answer to the question about the three-layered membrane that covers the brain and spinal cord and is referred to as 'membrane' is C. Meninges.