Lab 14 Sheepbraindiss 2

College Level Design: Tim Cannonhttp://academic.scranton.edu/department/psych/sheep/newsheep/ welcome2.html

Edited by Dr. S.C. Wache

Goal:

We will compare sheep brain structures with human brain structures. Compared to human cerebrum a human’s olfactory bulb is much shorter than sheep olfactory bulbs compared to the sheep cerebrum. Human cerebellum is bilobed, sheep cerebellum is not.

First, we will learn body positions applied to the whole sheep brain.

We will do two sections: one group will do a mid-sagittal cut, the other a coronal cut.

Use the mid-sagittal section to find your location through each consecutive coronal section.

Methods and Materials:We will be dissecting a preserved adult sheep brain.

Our dissection kit contains a scalpel, a fine tipped pair of scissors, a blunt metal probe, a fine tipped forceps, a blunt-tipped forceps.

It is vital to wear vinyl gloves. It is important to be careful when working with preservatives. If necessary protect your eyes. Follow OSHA (office of safety and Health administration) regulations.

Dispose of the dissected specimen as indicated on the MSDA (material safety and data administration) sheets.

These are some additional web sites where you can obtain more information:http://labs.ansci.uiuc.edu/rwjohnson/class/braintext.htmlUniversity of Scranton, Dissection of the Sheep BrainUniversity of Scranton, The Sheep Brain Dissection GuideMichigan State University, Atlas of the Sheep BrainInteractive Atlases, Digital Anatomist ProjectUniversity of Wisconsin, Global AnatomyUniversity of Utah, Anatomy-Histology TutorialsGray Cancer Institute On-line Medical Dictionary

Results: The result section should consist of drawings with labels on the structures that were identified.

Sheep brains arrive crudely prepared. You can see fatty tissue and three membranes, the meninges. The white film consists of a tough fibrous connective tissue, the dura mater.

Note: Underneath the dura mater, there is the arachnoid mater and the pia mater.

spinal cord

(Anterior) (Posterior)

BODY POSITIONS:

Diencephalon

LATERAL VIEW

Note the gyri and sulci.

SUPERIOR VIEW

Note the longitudinal fissure.

INFERIOR VIEW Ventral Midbrain

Pons Medulla Oblongata

Spinal Cord

Diencephalon: PITUITARY GLAND

Temporal lobe

Insula

Note: Insula - the lobe in the center of the cerebral hemisphere that is situated deeply between the lips of the sylvian fissure -- called also central lobe, island of Reil

Frontal lobe

Parietal lobe

Lobes of the Sheep Brain Cerebrum

Occipital lobe

Pineal gland

CEREBRUM AND CEREBELLUM BENT APART TO EXPOSE THE DORSAL MIDBRAIN.

INFERIOR VIEW

Diencephalon: MAMMILLARY BODIES

Oculomotor Nerve

Abducens Nerve

R- Olfactory Bulb

Note the trigeminal and abducens nerves.

Note the abducens, hypoglossal, and spinal accessory nerves.

Synonym: Vestibulo-cochlear Nerve

Note: You are asked to learn all 12 cranial nerve pairs. Please identify each nerve,Location, and function. Place answers in your journal.

‘Arbor vitae’ or ‘tree of life’

Thalamus

Pineal Gland

Corpus callosum

Thalamus

Lateral Ventricle

Third VentricleUse this frame to assess your location in the following coronal sections.

Pineal Gland

Lateral Ventricle

Note the gyri and sulci.

FIRST CORONAL SECTION: STARTS WITH THE ANTERIOR PORTION OF THE FRONTAL LOBE

Optic Chiasma

Diencephalon:

Pituitary Gland

Thalamus

Hypothalamus

CORONAL SECTION AT THE LEVEL OF THE PITUITARY GLAND

Note: septum pellucidum - the thin double partition extending vertically from the lower surface of the corpus callosum to the fornix and neighboring parts, separating the lateral ventricles.

Septum pellucidumDiencephalon:

Lateral Ventricle

ThirdVentricle

Midbrain (ventral surface) with mammillo-thalamic tract of fibers connecting thalamus and mammillary bodies

Caudate Nucleus

Caudate nucleus: one of the four basal ganglia in each cerebral hemisphere that comprises a mass of gray matter in the corpus striatum, forms part of the roof of the lateral ventricle, and is separated from the lentiform nucleus by the internal capsule

Diencephalon:

Pineal gland (releases melatonin which controls circadian rhythm)

Midbrain toward the Superior Colliculi

Caudate nucleus: comprises a mass of gray matter in the corpus striatum and forms part of the lateral roof of the lateral ventricle.Hippocampus: : a curved seahorse-shaped ridge extending over the roof of the descending horn of each lateral ventricle, but tissue within the temporal lobe; the hippocampus is part of the limbic system, and consists of gray matter covered on the ventricular surface with white matter.

From: www.neuropat.dote.hu/anastru/test2na.htm

(near Pons)

Connecting tissue between colliculi

(cerebral aqueduct)

Cerebellum

Corpora quadrigemina

(visible externally on the dorsal surface when bending open the brain between the cerebrum and cerebellum at a 45o angle)

Midbrain / near Pons

(ventral surface)

Note the H-shaped center of the spinal cord consisting of gray matter.

Summary:

We have studied the structures on a preserved sheep brain specimen. We have learned the functions of such structures using the lecture handout and comparing to what is known about the human brain function.

We learned body positions applied to the whole sheep brain.

The mid-sagittal cut was helpful in identifying the extension of the lateral ventricle to the third ventricle. The coronal cuts made it possible to find the cerebral aqueduct (aqueductus sylvii) that joins the third and fourth ventricles which house the CSF.

The coronal cut helped in the location of the hippocampus along the roof of the descending lateral ventricle.

Look at the live sheep brain dissection following this slide show.