|Neither the brain nor the spinal cord directly touches
the bones of the skull or spine. They are wrapped in three membranes
Any of three continuous sheets of connective
tissue which cover the spinal cord and the brain. From the outside in, the meninges
|Another cross-sectional view of the meninges
The arachnoid and pia mater collectively are known as the leptomeninges;
leptomeningitis is inflammation of the arachnoid and pia mater (see meningitis).
- The dura mater, a very tough white
fibrous tissue that is pressed against, and sticks to, the bony surface
of the interior of the vertebrae and
- The arachnoid, a thin layer resembling
a cobweb with numerous threadlike strands attaching it to the innermost
layer. The space under the arachnoid, the subarachnoid space,
is filled with cerebrospinal
fluid and contains blood vessels.
- The pia mater, the innermost layer
of meninges. This thin, delicate membrane is tightly bound to the surface
of the brain and spinal cord and cannot be dissected away without damaging
the surface. From it, numerous small blood vessels pass into the nerve
Meningiomas are tumors of the nerve tissue
covering the brain and spinal cord. Although meningiomas are unlikely to
spread, physicians often treat them as though they were malignant because
symptoms may develop when a tumor applies pressure to the brain.
Institutes of Health