AP1, Lab 8

OCULOMOTOR NERVES – Gently lift the pituitary gland from its anterior edge while looking for the
oculomotor nerves (cranial nerve #3) to be raised with the dura mater and the pituitary gland. Go
ahead and remove the dura mater and pituitary gland. The stumps of the oculomotor nerves will
either be lying on the midbrain, projecting forward or they will have torn loose and be attached to the
dura mater above the pituitary gland.
BRAIN STEM
Spinal cord – function?
Medulla Oblongata – functions?
Pons – functions?
**Confirm identifications of everything up to this point with your instructor.
2. Bisect the brain on the mid-sagittal plane along the longitudinal fissure all the way through the brain stem.
Make one clean, straight cut all the way through. Try to cut as precisely in the middle as possible. Identify the
following.
Corpus Callosum and Fornix– recall function?
Thalamus – recall functions?
Hypothalamus – recall functions?
Lateral ventricles - Use your metal probe to separate the corpus callosum and the fornix in order to see
better into the lateral ventricles. The corpus callosum will be the roof and the fornix
will be the floor of each ventricle.
Third ventricle – Look above the thalamus but below the fornix.
Choroid plexus - specialized capillaries for production of CSF. They are delicate and dark brown in color
similar to the vessels on the surface of the cerebrum. Use your forceps to gently reach deep into the
posterior portion of a lateral ventricle and pull some of this out. You might also find some in the 3 rd
and 4 th ventricles.
Cerebral aqueduct – passageway for CSF to flow from 3 rd to 4 th ventricle.
Fourth ventricle – space between the cerebellum and spinal cord.
3. Locate your thalamus again. Put the two hemispheres back together and perform a coronal section such that
your cut passes through the thalamus. Hold the two posterior portions together and view them from the
anterior side.
Identify the following:
Cerebral white matter
Cerebral cortex - The term “cortex” refers to the outer layer of any structure.
On the cow brain it’s the darker, more superficial layer that borders the white matter and follows
the contour of the sulci. The majority of the synapses of the brain are found in the cortex.
Corpus callosum
Lateral ventricles
Fornix
Third ventricle
Thalamus
Revised 5-3-2012 10