Ventral
Surface:
Looking medially:
- The longitudinal
fissure divides the
two hemispheres rostral
to the optic
chiasm.
- Just caudal to the optic chiasm you can see a hole on
the midline that also falls about in the middle (rostro-caudally) of the hypothalamus.
You are looking dorsally into
the third
ventricle though this hole,
which was formed when the pituitary
gland and its delicate connecting infundibulum were removed
during
dissection. The infundibulum is
complex for such a small structure. It contains axons that allow
the hypothalamus to
communicate with elements of the pituitary.
It also contains a hollow central core that allows cerebrospinal
fluid to
exchange between the pituitary below
and the third ventricle
above. The odds are good that this exchange has functional
importance.
- At the caudal
end of the hypothalamus there's
a buldge on the midline. In many sheep
brains, like this one, the bulge appears to be a single
item. In reality, however, there are two bulges just
off the midline that fuse in the middle, usually with a slight dip
between them. These are the mammillary
bodies.
- Caudal to the mammillary bodies
and between the large bundles of fibers (axons) forming the cerebral
peduncles is a substantial
indentation called the interpeduncular
cistern. (A "cistern" is a container used to store
water,
or other liquid, and was sometimes a covered depression in the
earth. This goes to show you that those old neuroanatomists just
kept coming up with great names!)