Anatomy and physiology labs

AP_5310_L08_Exp5_SheepBrainDiss.pdf

Introduction to ScienceExperiment 5Sheep Brain Dissection Experiment Inventory

Materials Sheep Brain

Dissection Tray

Dissection Tools Kit

EXPERIMENT 5: SHEEP BRAIN DISSECTION

The brain is the master control center of the body. This experiment will guide you through a dissection of a preserved sheep brain.

PROCEDURE

1. To begin, lay down your underpad and place your dissecting tray on top of it. Be sure you have all of your safety equipment on

before beginning.

2. Once prepared, gently open the bag containing your sheep brain and place it on the dissection tray.

3. Examine the external features of the sheep brain. Compare the cerebrum, brainstem, and cerebellum structures. From a later

al view, locate the frontal, parietal, occipital, and temporal lobes, as well as the central sulcus.

4. Place the brain ventral side down to view the dorsal side of the organ. Note the pia mater extending downward into the sulci

on the superior and lateral surfaces.

5. Observe the dura mater, the arachnoid mater, and blood vessels on the surface of the brain.

6. The two cerebral hemispheres are separated by a longitudinal fissure. Each hemisphere is divided into four major lobes. The

frontal lobes are directly anterior from the cruciate fissure (these may be difficult to locate). Moving posteriorly, you will see the

parietal lobe, followed by the occipital lobe. The temporal lobe can be identified as the slight bulge superior to the hippocam

pus gyrus. This may be ill defined.

7. Turn the brain over to examine its inferior aspect.

8. View the club-like olfactory bulbs on the inferior surface of the frontal lobes.

9. Locate the optic nerve. Find the optic chiasm, the x-shaped structure where medial fibers from each optic nerve cross over to

the opposite side.

10. Find the pituitary gland (posterior to the chiasm).

11. Locate the midbrain, pons, and medulla oblongata posterior to the optic chiasm.

12. Place the brain with the ventral side down.

13. Using a scalpel, make a mid-sagittal cut down the longitudinal fissure of the cerebrum and midline of the cerebellum to create

left and right halves. Note the tree-like arrangement of the white matter that is the cerebellar cortex.

14. Observe the exposed corpus callosum, the prominent collection of axons that extends along the medial face of the cerebral

hemisphere.

15. Identify the lateral, third, and fourth ventricles, continuations of the central canal that carry cerebrospinal fluid through the

spinal cord.

16. Just outside the third ventricle is the pineal body.

17. Identify the thalamus and hypothalamus.

18. Slice a small cross-section of the spinal cord. Note the classic butterfly-shaped section of the gray matter and the dorsal and

ventral roots on the outside of the spinal cord.

19. Clean off your dissecting tray and dissecting tools with soap and water. Biological scraps should not be thrown into the gar-

bage. Securely store the biological scraps until the end of the term so that they can be properly disposed of at one time.

20. Clean the area in which you worked with soap and water. As long as the underpad has not been damaged, keep it for future

experiments.