This shows the results of a cut that passes anterior to the genu of the corpus callosum. The darker (gray) matter is mostly cell bodies, and the lighter (white) matter is mostly axons. To assist you in recognizing gray (cell body) from white (axon) areas, the former will be written and indicated by gray and the latter white. If there are numerous labled areas on a section, it often helps to hit the Show/Hide button to toggle the labels and indicators. Try it, you'll like it.
Looking at the big picture, you
can see that the cerebral cortex (gray) has
sulci and gyri. Inside
the core of each gyrus there are substantial amounts of white matter
interconnecting the cortex with other structures in the central nervous
system. When we say that the brain tends to have gray
matter on the outside and white matter on the inside, you can think of
the cerebral and cerebellar cortecies.
Working from the ventral aspect of
your section, look laterally
until you find the first infolding (It's a bit subtle here, but it will get
bigger in latter sections.). This is the rhinal fissure. To
appreciate
the full extent of this fissure, either look at the ventral lateral
surface
of your uncut hemi-brain, or look back at Plate ??. Obviously, you
should
be able to see the rhinal fissure
in many of your coronal sections; we
will only label it here and in the next section. Impress your
friends by finding it
elsewhere.
Since this cut is rostral to
the
genu of the corpus callosum, there are no
fibers connecting the left
and right hemispheres across the
midline. You can see white
matter gathering, actually pointing, toward the midline. Those
are fibers that are heading to the corpus
callosum. They will
cross the midline in the next section.
Saying on the midline and looking
just
above the white matter that will become the corpus callosum is a thin
space, the callosal
sulcus. The cortex above
the collosal sulcus is the callosal
gyrus , and the space above that
is the cingulate
sulcus.
Let those terms wash over you, they, like most structures in the brain
are named very rationally. Trust in the neuroanatomists!
Not far off the midline, the
spaces below the white matter heading for the corpus callosum are the
rostral ends of the lateral
ventricles . The caudate
nucleus
forms the lateral wall of
the lateral ventricle. In
this cut you are
looking at the rostral side
of the section and you can see the front
end of each lateral ventricle.
These ventricles are slots that
run through each cerebral hemisphere.
They are closed at both
rostral and caudal ends. Cerebrospinal
fluid (CSF) flows
from the lateral to the 3rd ventricle.
The 3rd is 3rd because
there are two lateral ventricles.
Those rational neuroanatomists
strike again.
As mentioned above, this plate
shows the rostral half of a
cut through the tissue. This won't
always be true. We have chosen sections that best exemplify the
brain. We'll warn you when the direction in which you are viewing
is relevant to understanding the section.