Activity 8.2.5 Brain Dissection
Introduction
In the previous activity, you learned about the various structures that make up the
human brain. The sheep brain is very similar to the human brain, but it also
possesses some important differences. The purpose of dissecting a sheep brain is
to explore the three dimensional structure of the brain as well as investigate how the
spinal cord and major nerves connect to the brain.
In this project you will learn about the structure and functions of the brain as you
dissect a sheep brain and compare the anatomy with what you have learned about
the human brain.
Equipment










Activity 8.2.4 Brain Anatomy (to use as a reference)
Laboratory Journal
Pencil
Dissection pan and tools
Latex or nitrile gloves
Safety goggles
Toothpicks to secure flags
Adhesive labels or masking tape to make flags
Sheep brain
Camera (optional)
Free images courtesy of Wikimedia Commons http://commons.wikimedia.org/wiki/Main_Page
© 2013 Project Lead The Way, Inc.
GTT-MD Activity 8.2.4 Brain Dissection – Page 1
Procedure
Part 1: External Dissection
1. Working with a partner, obtain a dissection pan, a tool set, toothpicks, and
adhesive labels from your teacher.
2. Use the toothpicks and folded adhesive labels to make 19 toothpick flags. Label
the flags with the following terms: cerebrum, right frontal lobe, left frontal lobe,
right parietal lobe, left parietal lobe, right occipital lobe, left occipital lobe, right
temporal lobe, left temporal lobe, cerebellum, brain stem, olfactory bulb (two
flags), optic nerve (two flags), optic chiasm, corpus callosum, thalamus, and
hypothalamus.
3. Follow your teacher’s instructions, especially concerning safety with the
dissection equipment.
4. Follow the steps listed below to complete the dissection of the sheep brain. In the
instructions you will find terms in italics. These are the structures you must
identify and mark using a flag in the tissue at the correct location. Use your
drawings from Activity 8.2.4 or other resources as a guide.
5. Sketch or take notes in your laboratory journal to help you remember key
structures.
6. Obtain one sheep brain as instructed by the teacher.
7. As you first look at the sheep brain, notice the way the brain matter is folded.
This folding increases the surface area of the brain and allows for more nerve
cells to process information in the brain.
8. Locate the brain stem. In the sheep brain, the brain stem will exit the brain
horizontally. Sheep are four legged animals, so their brain and spinal cord line up
horizontally. Humans, on the other hand, are bipedal (two legged) animals.
Therefore, the human spinal cord must exit the brain vertically to travel down the
spinal column. Use a tape flag to label the brain stem.
9. The structure connected to the brain stem is the cerebellum and will appear as a
densely folded structure located at the base of the brain. Use a tape flag to label
the cerebellum.
10. The largest portion of the brain is the cerebrum. This portion of the brain
consists of four lobes. Use a tape flag to label the cerebrum.
11. Place the brain in your dissecting tray with the frontal lobes facing away from
you. This positioning will ensure that the right side of the brain is the same as the
right side of your body as you continue the dissection.
12. Locate and use your tape flags to label the following lobes of the cerebrum:
right and left frontal lobes, right and left parietal lobes, right and left
occipital lobes, and right and left temporal lobes.
13. Have your teacher check your flag placement before moving to the next step.
14. Turn the brain over so that you are viewing the bottom, or ventral side, of the
brain with the frontal lobes still facing away from you.
© 2013 Project Lead The Way, Inc.
GTT-MD Activity 8.2.4 Brain Dissection – Page 2
15. Two nerves involved in sensing input from the environment are visible on the
surface of the brain. Locate and use your tape flags to label the following
structures:

A pair of olfactory bulbs may be seen, one under each lobe of the frontal
cortex.

A pair of optic nerves may be seen as they meet in the optic chiasm,
which is the X-shaped structure on the bottom surface of the cerebrum. It
is named after the Greek letter chi, c, which it resembles.
16. If desired, take a picture of your labeled brain or make a sketch of your brain in
your laboratory journal.
17. Have your teacher check your flag placement before beginning the internal
dissection.
Part 2: Internal Dissection
18. Remove all tape flags from the brain and set aside.
19. Place the brain with the brain stem closest to you and carefully cut along the
longitudinal fissure, the natural division between the left and right hemispheres of
the cerebrum.
20. Gently cut and separate the two hemispheres of the brain. Continue cutting the
cerebellum and brain stem so you have two similar halves.
21. Position the left side of the brain with the frontal lobe to your right so that it looks
similar to the image you labeled in Activity 8.2.4.
22. Locate and label with a tape flag the following structures: corpus callosum,
thalamus, hypothalamus, brain stem, cerebellum, left frontal lobe, left parietal
lobe, left temporal lobe, and left occipital lobe.
23. If desired, take a picture of your labeled brain or make a sketch of your brain in
your laboratory journal.
24. Answer the conclusion questions.
Conclusion
1. In the previous activity, you learned that vision is processed in the occipital lobe.
What structural evidence did you see during the dissection to support this?
2. What structure connects the left and right hemispheres of the brain?
© 2013 Project Lead The Way, Inc.
GTT-MD Activity 8.2.4 Brain Dissection – Page 3
3. The thalamus acts as a relay station for all senses except smell. How does the
location of the thalamus within the brain help with this function?
4. What were some differences between the sheep brain that you dissected and a
human brain? What were some similarities?
© 2013 Project Lead The Way, Inc.
GTT-MD Activity 8.2.4 Brain Dissection – Page 4