Final answer:
The outermost covering of the brain and spinal cord is the dura mater, which provides physical protection to the CNS.
Step-by-step explanation:
The outermost covering of the brain and spinal cord is the dura mater. It is a tough outer layer that encloses the entire central nervous system (CNS) and the major blood vessels that enter the cranium and vertebral cavity. Its primary function is to provide physical protection.