5-13. COVERINGS OF THE CENTRAL NERVOUS SYSTEM
The coverings of the central nervous center (CNS) are skeletal and fibrous.
(1) Brain. The bones of the cranium form a spherical case around the brain.
The cranial cavity is the space enclosed by the bones of the cranium.
(2) Spinal cord. The vertebrae, with the vertebral foramina, form a
cylindrical case around the spinal cord. The overall skeletal structure is the vertebral
column (spine). The vertebral (spinal) canal is the space enclosed by the foramina of
b. Meninges (Fibrous Membranes). The brain and spinal cord have three
different membranes called meninges surrounding them (Figure 5-8). These coverings
(1) Dura mater. The dura mater is a tough outer covering for the CNS.
Beneath the dura mater is the subdural space, which contains a thin film of fluid.
Figure 5-8. The meninges, as seen in side view of the CNS.
(2) Arachnoid mater. To the inner side of the dura mater and subdural
space is a fine membranous layer called the arachnoid mater. It has fine spider-web
type threads that extend inward through the subarachnoid space to the pia mater. The
subarachnoid space is filled with cerebrospinal fluid (CSF).
ARACHNOID = Spiderlike