(māt'ĕr )

[L. mater, mother]

Nonneural tissue coverings of the brain and spinal cord; meninges.

arachnoid m.Arachnoid membrane.

dura m.The outermost meninx, a tough sheet of fibrous connective tissue that completely envelops the brain and spinal cord inside the skull and vertebral canal. Inside the skull, there is no epidural space, and the dural envelope is fused with the inner periosteum of the skull bones. In several places within the skull, the dura divides into a periosteal and a meningeal layer. The meningeal layer forms dural septa, which support the brain. Inside the vertebral canal, however, the dural envelope is separated from the vertebral bone by an epidural space filled with fat and a network of veins. SYN: dural membrane; pachymeninx.

pia m.The innermost meninx, a delicate membrane investing the surfaces of the brain and spinal cord and closely following all their contours. In most places, the pia mater is one cell thick. It invests the superficial blood vessels of the brain and follows the arteries for a short distance as they dive into the brain tissue. SYN: pial membrane.