Nervous System II
Interconnected cavities called
trı˘-klz) lie in
the cerebral hemispheres and brainstem (
f g. 11.3
ence plates 13 and 14). These spaces are continuous with the
central canal of the spinal cord and are F
lled with CS±.
The largest ventricles are the two
F rst ventricle is in the left cerebral hemisphere and the sec-
ond ventricle is in the right cerebral hemisphere. They extend
anteriorly and posteriorly into the cerebral hemispheres.
A narrow space that constitutes the
is in the
midline of the brain beneath the corpus callosum, which is a
bridge of axons that links the two cerebral hemispheres. This
ventricle communicates with the lateral ventricles through
) in its anterior end.
is in the brainstem, just anterior to
the cerebellum. A narrow canal, the
duct of Sylvius), connects it to the third ventricle and passes
lengthwise through the brainstem. This ventricle is continuous
with the central canal of the spinal cord and has openings in
its roof that lead into the subarachnoid space of the meninges.
Tiny, reddish cauliﬂ owerlike masses of specialized cap-
illaries from the pia mater, called
sus-ez), secrete CS±. These structures project into the
cavities of the ventricles
(f g. 11.4)
. A single layer of special-
ized ependymal cells (see chapter 10, p. 361) joined closely by
tight junctions covers the choroid plexuses. In much the same
way that astrocytes provide a barrier between the blood and
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 gener-
ally does not dip into the grooves and depressions on their
surfaces. Many thin strands extend from its undersurface
and are attached to the pia mater. Between the arachnoid
and pia maters is a
which contains the
nal ﬂ oo
is thin and contains many nerves, as well
as blood vessels that nourish the underlying cells of the brain
and spinal cord. The pia mater is attached to the surfaces
of these organs and follows their irregular contours, passing
over the high areas and dipping into the depressions.
is an inflammation of the meninges. Bacteria or viruses
that infect the cerebrospinal F
uid are typical causes of this condition.
Meningitis may a±
ect the dura mater, but it is more commonly limited
to the arachnoid and pia maters. Meningitis most often a±
and children and is serious. Complications include loss of vision, loss
of hearing, paralysis, and mental retardation. It may be fatal.
Describe the meninges.
Name the layers of the meninges.
Explain the location of cerebrospinal F
Meninges of the spinal cord. (
) The dura mater ensheaths the spinal cord. (
) Tissues forming a protective pad around the cord ²
the epidural space between the dural sheath and the bone of the vertebra.