1. Sheep Brain Dissection Guide
Good
Luck!!
Laurie Hayes

2. To begin
Get gloves and a rubber apron or lab coat. Goggles are available if you would like them.
Pick up dissection tray, dull probe, pins and labels
Obtain a sheep brain and share this with a partner (or 2)
Rinse the sheep brain to remove preservative

3. Meninges of the Brain
Brain is protected by the skull and 3 layers of membranes called meninges

4. Observe Meninges
Examine the brain to see if there is a tough outer coat…This is the DURA MATER (literally means “tough mother”)
Now look for the stringy, web-like ARACHNOID MATER (literally means spider mother) beneath and stuck to the dura mater. The space under the arachnoid, the subarachnoid space, is filled with cerebrospinal fluid and contains blood vessels.
Look deeper and see an thin transparent membrane that follows the contour of the ridges (gyri) and valleys (sulci) of the brain. This is the PIA MATER ( means tender mother)

5. Questions?? What is the function of the meninges?
Describe the following meninges:
Dura mater, Arachnoid mater, and Pia mater
What is meningitis?

6. Main Brain Regions
Identify the cerebrum, brain stem) and cerebellum on your brain
Draw picture of sheep brain and label structures
Cerebrum
Cerebellum
Brain stem

7. Questions?? Which part of the brain allows for 1) Balance 2) Breathing
3) Hearing and Vision

8. Human vs Sheep
Compare the various areas of the sheep brain (cerebrum, brain stem, cerebellum) to the human brain.
#4. How is it the same and How is it different?
Human brain

9. Identify Dorsal Structures
With the dorsal side up, identify the cerebral hemispheres, gyri, sulci,and longitudinal fissure on your sheep brain

10. Questions?? What does the longitudinal fissure divide?
What is the difference between gyri and sulci?
What is the purpose of the gyri and sulci?

11. Lobes of the Cerebrum
Find the 4 lobes of the brain-frontal, parietal, occipital,
and temporal
Using pins label each lobe
Teacher check

12. Questions???? Name the lobe that functions in a) Hearing b) Vision
c) Touch
d) Movement

13. Corpus Callosum
At the longitudinal fissure, gently separate the two hemispheres and look down between them for the thick band of white fibers. This is the corpus callosum
What is its function?

14. Identify Ventral Structures
Place the sheep brain ventral side up.
Identify the olfactory bulb, optic nerve, optic chiasm
Using pins label each structure.
Draw and label the structures in lab writeup

15. Questions??
How does the human brain’s olfactory bulb differ from the sheeps?
Which is able to smell more odors?
Look at the optic chiasma. What happens to the optic nerve (vision) at the optic chiasma?
Which side of the occipital lobe (right or left) “sees” for the right eye?

16. Brain Stem
Look at the three parts of the brain stem-the midbrain (cerebral peduncle and mammilary body), pons and medulla oblongata
Pin and label parts
Teacher check

17. Function
Mammillary bodies serve as relay stations for reflexes related to sense of SMELL
Cerebral Peduncle-group of myelinated nerves

18. Questions?? Label your diagram with parts of midbrain and brain stem
What is the function of the medulla oblongata and pons?
Could you survive without them?
Why or Why not?

19. Identify dorsal structures
Carefully pull the cerebellum away from the cerebrum. Don’t break any structures off.
Identify the pineal body, superior colliculi, and inferior colliculi.

20. Functions-Reflex Centers
Inferior Colliculi- movement of head and trunk in response to sound stimuli
Superior Colliculi-movement of eyes, head and neck in response to visual stimuli

21. Pineal Gland Produces the hormone melatonin at night
Melatonin is the sleep hormone

22. Questions??
What is the function of the Pineal body?

23. Midsagittal Section Obtain a brain the has been cut in half
Locate the brain stem parts: the medulla oblongata, the pons, cerebrum, and cerebellum

24. Cerebellum
Look at the cross section of the cerebellum. The inner structure is called the arbor vitae (living tree).
Why is this a good name for it?

25. Midsagittal Section
Locate the corpus callosum, thalamus,lateral ventricle, fourth ventricle and cerebral aqueduct

26. Questions What is the function of the ventricles?
The cerebral aquaduct allows for the circulation of the cerebral spinal fluid through the ventricles. What do you think would happen if the duct became blocked?
How would that affect brain tissue?

27. How does the normal brain compare with the Alzheimer’s brain?
How would that explain the memory loss?

28. The End!!
Good bye or in sheep language
BAA BAA