Neuroanatomy Lab A- Sheep Brain Dissection

Neuroanatomy Lab
Monday July 20
A- Sheep Brain Dissection
Based on Michael Peters lab manual
http://www.psychology.uoguelph.ca/learnmatl/sheep_labman/lab_manual_sheep_brain.pdf
Instructors:
Sonal Jhaveri, Senior Scientist, Department of Brain & Cognitive Science
Mandana Sassanfar, Instructor, Department of Biology
Work in pairs. You should wear goggles, gloves and a lab coat and work under the hoods.
Materials:
Gloves
Goggles
Dissection Tray
Diaper
Dissection tools
Sheep brains
Station set up.
1) Set up a diaper on the bench. Set up the dissection tray on the diaper. Obtain dissection instruments:
Scalpel, razor, scissors, scooping instrument, and twisters.
2) Obtain a sheep brain and place in the dissection tray
3) Orient the opening of the vent over the brain
Start your observations:
- Orient the brain: Identify the dorsal, ventral, anterior (frontal) and posterior positions.
- Observe the brain: It should still have the stem and 3 protective layers (meninges) attached. But your
particular specimen might have been removed from the skull without care and have a missing or damaged
stem and membranes.
- Using a dissecting scissor make an opening in the meninges and cut through to remove them carefully to
expose the brain.
- Identify the 3 layers of meninges as you remove them: the dura mater, arachnoid mater, and pia mater.
What do the names mean?
- Lay the brain on its ventral side; Identify the cerebrum, the two cerebral hemispheres, the sulci and gyri,
the longitudinal fissure that separates the two hemispheres, the cerebellum, and the vermis that separate the
cerebellum into two lobes, the stem and spinal chord.
http://www.personal.psu.edu/faculty/d/y/dys100/anatomy/SheepBrain/dorsal.htm
Which hemisphere is dominant in most people?
_________________________
Identify the 4 lobes of the brain.
Frontal Lobe
Parietal lobe
Occipital Lobe
Temporal lobe
Name the sulcus that separates the front lobe from the parietal lobe: _________________________
Name the sulcus that separates the frontal and parietal lobes from the temporal lobe:_______________
Which lobe contains the primary visual cortex?___________________________
- Turn the brain around to expose the ventral side.
- Identify the frontal cortex, pituitary gland (if present), the olfactory bulbs and olfactory tracts,
the optic nerves and the optic chiasm, the pons, the medulla oblongata
If present, the pituitary gland will obscure a lot of the cranial nerves and will need to be removed.
- Observe the cerebral peduncles, the pons, the trapezoid body, the oculomotor nerve, the trigemenial nerve, and
the facial nerve.
Orient the cerebellum and pons:
Is the cerebellum anterior, posterior ventral or dorsal to the pons? ________________________
It is also a good time to identify the major subdivisions of the brain from posterior to anterior:
Telencephalon (forebrain or cerebral cortex and subcortical structures)
Diencephalon (Thalamus and hypothalamus)
Mesencephalon (midbrain)
Metencephalon and Myelencephalon (Hindbrain)
Another way to subdivide the brain is shown below:
1) Cerebral Hemispheres
2) Diencephalon: thalamus and hypothalamus
3) Cerebellum
4) Brain Stem (Midbrain, Pons and Medulla)
-
Next perform a longitudinal cut throught the brain to separate the two hemispeheres.
-
Turn the brain over on its ventral side. Using a razor cut the brain in two by sawing through the
longitudinal fissure. Do not cut all the way through.
-
Open the brain in two and identify the parts indicated in the picture below.
-
Observe how each structure connect to other parts of the brain.
- Next complete cutting the brain in half and oberserve the lateral sections (plate 2).
-
Locate
the massa intermedia
the 4 ventricules
the cerebellum
the cingulate gyrus
the corpus callosum
the pimary fissure that separates the cerebellum into 2 lobes
the thalamus and hypotalamus
the fornix
the pineal gland
the hippocampus
the optic chiasm
the superior and inferios colliculus
the cingulate gyrus
the pons
th medulla
- Observe how each structure is linked to other structures in the brain.
- Describe the specific function of each structure
15 fornix
1 cerebellum
2 primary fissure, cerebellum
3 superior colliculus
4 inferior colliculus
5 pineal gland
6 habenula
7 stria medullaris
8 lateral ventricle
9 third ventricle
10 cerebral aqueduct
11 fourth ventricle
12 septum
13 septum pellucidum (a bit of it)
14 posterior commissure
16 hippocampus
17 mammillary body
18 hypothalamus
19 anterior commissure
20 body of corpus callosum
21 genu of corpus callosum
22 splenium of corpus callosum
23 optic chiasm
24 pons
25 massa intermedia - thalamus
26 cingulate gyrus
Identify again the major subdivisions of the brain
- Next dissect the hippocampus. It is deep inside the temporal lobe.
This will be done is stage and will be demonstrated in class.
What is the main function of the hippocampus? ___________________________
You will carefully shave layers of the top dorsal cortex to expose the white matter and the horn of the lateral
ventricule (cavity). The top of the hippocampus will start to appear (16 in plate 2). The hippocampus (35) is
right below the lateral ventricule.
Remove the cortex around the hippocampus to expose the superior colliculus (2), and then the pineal gland
which is just anterior to the superior colliculus.
The primary fissure (6) which separates the two lobes of the cerebellum (4 and 5) is nicely visible.
- When the hippocampus is fully exposed, peel it gently toward the anterior end to expose the tahamus which
lies just beneath the hippocampus.
- You will use a new brain to perform coronal by cutting slices from the anterior to the posterior end, and
horizontal slices by cutting 0.5 cm slices from the top to the bottom of the brain from anterior to posterior.
Coronal cut
Plate14 :
29 hippocampus
30 pineal gland
31 posterior commissure
32 beginning of cerebral
aqueduct
33 lateral geniculate nucleus
34 optic tract fibres on way
lateral
23 ventricle
geniculate nucleus
24 amygdala
F fimbria
Horizotal cut
Plate 21:
5 corpus callosum
6 internal capsule
14 septum pellucidum
15 septum
17 lateral geniculate
nucleus
19 external capsule
20 extreme capsule
21 claustrum
22 putamen
23 posterior commissure
into
Additonal links:
The sheep brain: 3D dissection a teaching video from Wellesley college showing how to dissect a brain
(http://www.wellesley.edu/Biology/Concepts/Html/sheepbrain.html)
A laboratory manual for the dissection of the sheep brain
by Michael Peters and Fern Jasper- Fyer
Excellent manual from which most of the photographs below were copied.
http://www.psychology.uoguelph.ca/learnmatl/sheep_labman/lab_manual_sheep_brain.pdf
The brain from top to bottom
an interactive site with a lot of basic information
http://thebrain.mcgill.ca/flash/index_a.html