Meninges
Bones, membranes, and fluid surround the organs of the CNS. The brain lies within the cranial cavity of the skull, and the spinal cord occupies the vertebral canal within the vertebral column. Beneath these bony coverings, membranes called meninges (singular, meninx), located between the bone and soft tissues of the nervous system, protect the brain and spinal cord.
The meninges have three layers - dura mater, arachnoid mater, and pia mater. The dura mater is the outermost layer of the meninges. It is composed of tough, white fibrous connective tissue and contains many blood vessels and nerves. The dura mater continues into the vertebral canal as a strong, tubular sheath that surrounds the spinal cord. The arachnoid mater is a thin, weblike membrane that lacks blood vessels and is located between the dura and pia maters. It spreads over the brain and spinal cord but generally does not dip into the grooves and depressions on their surfaces.