SHEEP BRAIN DISSECTION (Activity on page 212)



SHEEP BRAIN DISSECTION

Materials: Ziploc bag for brain waste, Gloves, Dissection tray, Probe, Scalpel, Sheep’s brain

Procedures:

1. Put on safety goggles, lab coat and gloves. Gather materials. Rinse brain. Make sure that the pieces do not wash down the sink-put them in the ziploc bag.

External structures:

[pic]

2. With the brain in the tray, identify the cerebrum, cerebellum and brain stem.

3. The surface of the cerebrum is covered with large folds of tissue called gyri.   The grooves between the gyri are sulci.   The deeper sulci are often termed fissures.   The fissures are used as landmarks to divide the surface of the cerebrum (the cerebral cortex) into regions or lobes.

4. On the cerebrum identify the frontal, parietal, temporal, and occipital lobes

5. The pituitary gland is a large round structure under the chiasma (cross).  If the dura mater is removed it may be hard to find the pituitary gland but try to identify.

[pic]

6. Pineal gland: Carefully bend the cerebellum to get an inside glimpse of the brain.  The bumps you see (kind of resemble a “butt”) are the superior colliculi.  The smaller ones underneath are inferior colliculi. If you gently push those structures down, you can see the tiny nub of the pineal gland

[pic]

7. Notice that the cerebrum consists of two parts called hemispheres. Use the scalpel to separate the two hemispheres. Use a knife or long-bladed scalpel to cut the specimen along the longitudinal fissure along the median/ midsagital plane.  This will allow you to separate the brain into the left and the right hemisphere.  You should also cut through the cerebellum.

[pic]

8. Lay the halves open and use the picture below to identify the corpus callosum: The corpus callosum had been connecting the two cerebral hemispheres and can now be clearly seen in the brain section

9. Next identify the thalamus & hypothalamus (parts of the diencephalon): Inferior to the corpus callosum is a round structure known as the thalamus.  It seems it almost perfectly centered.  Just behind the thalamus is the pineal body (gland).  The hypothalamus is also round shaped but is lower and toward the front of the brain.

10. Find the pons and medulla oblongata (parts of the brain stem): The pons, medulla, cerebellum and spinal cord are also visible in the side view of the brain. Gently separate the cerebellum at the transverse fissure, which separates it from the cerebrum. Toward the back of the brain, there are bulges that indicate the midbrain, the pons, and the medulla. 

[pic]

11. Use a scalpel to cut a cross section of the cerebrum in the occipital lobe area.  You should be able to see the color and texture differences of the white matter and the gray matter

[pic]

Be prepared to recognize all bolded structures on a lab practical label test tomorrow.

12. For clean up:

▪ Place brain tissue into the ziploc bag and place in the trash

▪ Wash the dissecting tray and other dissecting materials with soap and water.

▪ Dry materials and put them back.

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