Carolina Mammal Brain Dissection Guide - Manual (Page 3)

Carolina TM Mammal Brain Dissection Guide
Overview
The Carolina™ Mammal Brain Dissection Guide is a general set of instructions for dissecting mammal brains.
With each type of brain, there will be differences in the size of the structures and brain regions, but the
general structures and their relative location will be the same or very similar.
Safety
Follow safe laboratory practices when performing any dissection. Wear safety glasses or goggles, gloves, and lab
aprons when dissecting. Perform dissections on a dissecting tray or pan to contain specimens and fluids. Be
careful when using sharp instruments such as scalpels, forceps, teasing needles, and scissors.
Procedure
1. Review the glossary provided at the end of the dissection guide. Refer to the Mammal Brain Section
diagram to help you observe and identify external and internal structures.
2. Place the brain on a dissecting tray, dorsal side up.
3. Observe the dura mater, or outer meninges, if they are present and were not removed prior to
preservation. The two remaining meninges, pia and arachnoid, form a thin covering which adheres to the
surface of the cerebrum. Use forceps to gently remove these layers.
4. Identify the cerebrum. On the cerebral surface, observe the grooves known as sulci. Also observe the
ridges called gyri. Identify the medial longitudinal fissure, which separates the right and left hemispheres
of the cerebral cortex.
5. Locate the four lobes of the cerebrum. At the anterior portion of the brain is the frontal lobe, which
controls motor functions. Dorsal to this lobe is the parietal lobe, which receives and processes somatic
sensory information. Inferior to the parietal lobe are the temporal lobes. The temporal lobes receive and
process auditory sensations. The dorsal portion of the cerebrum makes up the occipital lobe, which
receives and processes sensations from the eyes.
6. Locate the cerebellum, which is inferior to the occipital lobe of the cerebrum. The cerebellum has an
outer cortex and is folded. It is incompletely divided by a dorsal central ridge called the vermis. The
cerebellum controls muscle coordination.
7. Place the brain on the dissecting tray, ventral surface up. Locate the following structures: medulla, pons,
brain stem, and spinal cord.
8. The cranial nerves and pituitary were cut when the brain was removed from the skull. You should be able
to identify the olfactory bulb, which lies below the frontal lobe of the cerebrum. Identify the optic
chiasma. This x-shaped structure is formed by the crossover of the right and left optic nerves. The optic
nerves have been removed, but portions of the optic chiasma are visible.
9. Place the brain on a dissecting tray, dorsal side up. Using your fingers, gently widen the medial
longitudinal fissure. Insert a scalpel into the fissure and cut through the corpus callosum connecting the
two cerebral hemispheres. Continue to cut, dividing the cerebrum, cerebellum, and brain stem into two
longitudinal halves.
10. Each hemisphere contains a lateral ventricle, referred to as the first and second ventricles. The lateral
ventricles can be located by removing the septum pellucidum. The septum pellucidum is a thin,
transparent membrane located inferior to the corpus callosum on each hemisphere.
T e a c h e r ’ s M a n u a l 3