The central nervous system(CNS)is made up of the brain and spinal cord and is covered with three layers of protective coverings called meninges (“meninges” is derived from the Greek and means “membranes”) (Figure 16.21). The outermost layer is the dura mater, the middle layer is the web-like arachnoid mater, and the inner layer is the pia mater, which directly contacts and covers the brain and spinal cord. The space between the arachnoid and pia maters is filled with cerebrospinal fluid(CSF). The brain floats in CSF, which acts as a cushion and shock absorber.
Figure 16.21 The cerebral cortex is covered by three layers of meninges: the dura, arachnoid, and pia maters.