Human Anatomy Physiology I PSIO 201 Sheep Brain Dissection Guide Includes Important Sheep Brain Structures Regions and Features to Know Before lab please make sure to review the PlayPosIt Bulb on the Sheep Brain Additionally this resource is provided for you to see certain steps of the dissection labeled https spark adobe com page fRazXUHsdBYBA For the Dissection 1 Put on gloves and goggles 2 Your sheep brains may have fat around the optic nerves and pieces of the ethmoid bone attached to the olfactory bulbs If this is the case remove the fat and ethmoid bone using a scalpel and or scissors The sheep brain is covered with a glossy tough outer connective tissue layer called the dura mater You can see two structures before removing the dura mater the pituitary gland and the optic chiasm The pituitary gland produces and secretes many hormones The optic chiasm is where the optic nerves cranial nerve II cross When you remove the dura mater these two structures will likely be pulled off 3 Carefully remove the dura mater Be careful and do not remove the cerebellum Once the dura mater is removed you can clearly see 3 of the 4 principle regions of the brain the brainstem cerebellum and cerebrum The surface anatomy features you can see are the lobes of the cerebrum frontal lobe temporal lobes parietal lobes and occipital lobe the longitudinal fissure which separates the two hemispheres of the cerebrum the transverse fissure which separates the cerebrum from the cerebellum as well as the gyri bumps and sulci grooves of the brain You should know two specific gyri of the cerebrum the pre central gyrus which is just anterior to the central sulcus and the post central gyrus which is immediately posterior to the central sulcus One other sulcus you should know is the lateral sulcus which separates the frontal and temporal lobes When you removed the pituitary gland while cutting the dura mater you may have also removed the infundibulum the structure attaching the pituitary gland to the hypothalamus You can also see the 12 cranial nerves You should be able to identify cranial nerves I VI on a sheep brain for the practical We will go over the cranial nerves during lab 9 4 Look at the posterior view of the brain Bend the cerebellum down to view the superior and inferior colliculi Together these four structures of the diencephalon make up the corpora quadrigemina These structures are visible at the gap between the cerebrum and the cerebellum at the transverse fissure Above the superior and inferior colliculi you can see the pineal gland an endocrine structure that produces melatonin Human Anatomy Physiology I PSIO 201 5 Use a scalpel and the longitudinal fissure as a guide to separate the left and right hemispheres of the cerebrum and cerebellum You are now able to view another principle region the diencephalon In the diencephalon you should be able to locate these specific regions the thalamus epithalamus and hypothalamus The thalamus which is the round region in the middle of the diencephalon contains the intermediate mass a structure which may or may not be visible depending on how you dissected your brain You can find the epithalamus by first finding the pineal gland which you found earlier If you trace the pineal gland anteriorly the structure you are tracing is the epithalamus The hypothalamus is the region below or inferior to the thalamus In the midsagittal view you should be able to find these structures the corpus callosum the lateral ventricles the third ventricle the fornix the choroid plexus the optic chiasm and the mammillary body The corpus callosum connects the two cerebral hemispheres The lateral ventricles are spaces that fill with CSF they are located below inferior to the corpus callosum The third ventricle is a space surrounding the thalamus Like the lateral ventricles the third ventricle fills with CSF The fornix is part of the limbic system and looks as though it helps enclose the lateral ventricles The choroid plexus is a bundle of capillaries that filters blood plasma into CSF and is located above superior to the epithalamus The mamillary body is posterior to the optic chiasma and the hypothalamus Looking at the cerebellum you should see a distinct tree like white area of white matter called the arbor vitae The gray matter that surrounds this is called folia Near the brainstem you will see a triangular space called the fourth ventricle The cerebral aqueduct is a structure that joins the third and fourth ventricles The vermis connects the two hemispheres of the cerebellum This is the structure you cut through when cutting through the longitudinal fissure In the brainstem you should be able to find these specific regions the medulla oblongata the pons and the midbrain In the midbrain you should be able to find these structures that you previously found superior and inferior colliculi 6 If you cut a cross section of the cerebrum you will be able to note the difference between the white and gray matter of the cerebrum Human Anatomy Physiology I PSIO 201 The following structures regions on the sheep brain are testable for the exam Dura mater Pituitary gland infundibulum The PRINCIPLE regions of the brain The SPECIFIC regions of the brain Cerebrum Cerebellum Diencephalon Brainstem Medulla oblongata Midbrain Pons Thalamus Hypothalamus Epithalamus Pre central gyrus Post central gyrus Longitudinal fissure Transverse fissure Occipital lobe Parietal lobe Frontal lobe Temporal lobe The surface anatomy the specific gyri sulci fissures lobes 4 superior colliculi inferior colliculi corpora quadrigemina Pineal gland Optic chiasm Mamillary body Arbor vitae folia and vermis Corpus callosum lateral ventricles fourth ventricle cerebral aqueduct Gray matter white matter choroid plexus Cranial nerves I VI You should be able to name functions for any starred structure region