Page 335 - Atlas of Histology with Functional Correlations

FIGURE 9.1 ■ Central nervous system (CNS). The CNS is composed of the
brain and spinal cord. A section of the brain and spinal cord is illustrated with
their protective connective tissue layers called meninges (dura mater, arachnoid
mater, and pia mater).

The outermost meningeal layer is the dura mater, a tough, strong, and thick

layer of dense connective tissue fibers. Deep to the dura mater is a more delicate
connective tissue, the arachnoid mater. The dura mater and arachnoid mater
surround the brain and spinal cord on their external surfaces. The innermost
meningeal layer is the delicate connective tissue pia mater. This layer contains

numerous blood vessels and adheres directly to the surfaces of the brain and
spinal cord.

Between the arachnoid mater and the pia mater is the subarachnoid space.
Delicate, weblike strands of collagen and elastic fibers attach the arachnoid
mater to the pia mater. Filling and circulating in the subarachnoid space is the

CSF that bathes and protects both the brain and spinal cord from shock and
injury.

CEREBROSPINAL FLUID

The CSF is a clear, colorless fluid that cushions the brain and spinal cord and

provides protective buoyancy from physical injuries. CSF is continually
produced by the choroid plexuses in the lateral, third, and fourth ventricles or
cavities of the brain, with the majority of the fluid produced in the lateral
ventricles. Choroid plexuses are small, vascular extensions of dilated and

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