Dissection of the Sheep Brain
Neurobiology, Spring ‘07
We will dissect the sheep brain this semester to better learn the organization of a mammalian brain and the relationships of specific structures involved in many of the functional circuits that are of importance to us in this course. We will follow the general pattern of study used by our lab guide (The Sheep Brain: A Photographic Series, by Vanderwolf and Cooley) - identifying superficial structures first, then studying structures found along the sagittal midline, and finishing with a detailed analysis of internal structures found in coronal sections. This pattern is also used by a sheep brain dissection manual put on the internet by the University of Scranton (http://www.uofs.edu/sheepindex.html), and I recommend using this web site as a supplementary study guide. However, the internet guide uses some terminology that is a little different from the terms that we will be using, so I have tried to indicate those differences in the list that follows. This list is a comprehensive summary of all of the structures that you will be responsible for knowing, either in terms of straight identification in the laboratory or in the context of some of the circuits that we will be discussing in the lecture. I will monitor your pace in this series of dissections, but you will have a lot of freedom to study regions of the brain in whatever sequence works best for you and at your own pace.
I would like you to do most of your work in groups of two (even though you could all benefit from working communally at times), and each group will have 2-3 sheep brains to use throughout the semester. One should be cut sagittally to study the structures on the external surface and along the midline, another will be cut in a series of coronal sections (see p. 28 in your lab guide) and stained for contrast (see below), and a third or fourth can be used for special dissections to expose complex 3-dimensional circuits such as the hippocampus or fornix or visual pathways. These will be stored in a jar (for each group) filled with 70% ethanol, and will be available for your study in J-153 at any time the room is unused. The coronal sections (and any other sections that you would like) will be stained with the following Mulligan method:
1) Wash sections overnight in running water to remove preservativa;
2) Rinse in 3 changes of distilled water for 20 minutes each;
3) Place in preheated Mulligan’s solution for 3-5 minutes (60oC);
4) Rinse in tap water for 1 minute;
5) Place in 1% ferric chloride solution for 2 minutes;
6) Wash in running tap water for 5 minutes;
7) Place in 1% potassium ferrocyanide until gray matter turns bright blue (~3 minutes);
8) Wash in running tap water for 24 hours;
9) Store in 70% ethanol.
Mulligan’s solution:
carbolic acid (phenol), crystalline 40.00 g
copper sulfate, crystalline 5.00 g
HCl, concentrated 1.25 mL
H2O, distilled 1 L
(be careful not to breathe fumes)
1% Ferric Chloride:
ferric chloride, crystalline 10 g
H2O, distilled 1 L
(make up just before use, then discard)
1% Potassium Ferrocyanide:
potassium ferrocyanide, crystalline 10 g
H2O, distilled 1 L
(can be stored before use)
Terms (& Structures) to know in the sheep brain:
(Terms in italics are not shown in your dissection manual)
Directional Terms:
anterior/posterior
rostral /caudal
dorsal/ventral
superior/inferior
lateral/medial
proximal/distal
Brain Regions:
telencephalon - cerebral cortex, corpora striata (caudate, internal capsule, putamen), rhinencephalon (olfactory bulb, hippocampus, amygdala, septal region,cingulate gyrus)
diencephalon - thalamus, hypothalamus, pituitary gland, pineal gland
mesencephalon - tectum (corpora quadrigemina = superior & inferior colliculi), tegmentum
metencephalon - cerebellum, pons
myelencephalon - medulla oblongata
External Surface:
4th ventricle
abducens nerve (VI)
ansate sulcus (= cruciate sulcus)
anterior medullary velum
brachium conjunctivum (= rostral or superior cerebellar peduncle)
brachium pontis (= middle cerebellar peduncle)
brainstem
cerebellum (vermis, hemispheres, ansiform lobule, paraflocculus, flocculus, posterior median lobule, anterior lobe)
cerebral peduncle
choroid plexus
cisterna magna
coronal sulcus (= superior frontal sulcus)
dentate gyrus
entorhinal cortex (= hippocampal gyrus)
facial nerve (VII)
fimbria
frontal lobe
glossopharyngeal nerve (IX)
hippocampal fissure
hypoglossal nerve (XII)
infundibulum
interpeduncular fossa (cistern)
lateral geniculate body
lateral olfactory tract (= gyrus) (= stria)
mammillary body
marginal gyrus
medial geniculate body
medial olfactory tract (= gyrus)
median longitudinal fissure
meninges (dura mater, arachnoid, pia mater)
mesencephalic tectum (corpora quadrigemina - superior & inferior colliculi)
mesencephlic tegmentum
obex
occipital lobe
oculomotor nerve (III)
olfactory bulb
olfactory tubercle
optic nerve (II) (optic chiasm, optic tract)
parietal lobe
periamygdaloid cortex (=uncus)
pituitary gland (anterior & posterior)
pons
prepyriform cortex
pulvinar
pyramidal tract
pyriform cortex (= hippocampal gyrus)
restiform body (= caudal or inferior cerebellar peduncle)
rhinal fissure
rhinencephalon
spinal accessory nerve (XI)
superior cistern
sylvian sulcus
tela choroidea
temporal lobe
transverse fibers
trapezoid body
trigeminal nerve (V)
trochlear nerve (IV)
tuber cinereum
vagus nerve (X)
vestibolocochlear nerve (VIII)
Sagittal Surface:
3rd ventricle
4th ventricle
anterior commissure
callosal sulcus
central canal
cerebellum (arbor vitae, folia)
cerebral aqueduct
cingulate gyrus
cingulate sulcus
corpus callosum (rostrum, genu, body, splenium)
fornix (columns, body, hippocampal commissure)
genual sulcus
hippocampal formation
inferior colliculus
interventricular foramen
lamina quadrigemina
lamina terminalis
lateral ventricle
mammillothalamic tract
massa intermedia
pineal body
posterior commissure
septal area
septum pellucidum
splenial sulcus
superior colliculus
thalamus
Coronal Sections: (Follow p. 28 in the lab guide in making the coronal sections - you should end up with 11 pieces of brain produced by 10 cuts, but cut just 3-4 sections at a time starting with the most anterior. The sections are labeled by the cut location and you should see the same structures on either of the surfaces produced by a given cut.)
anterior forebrain (sections C, D, E) -
anterior commissure
caudate nucleus
cingulum
claustrum
corona radiata
corpus callosum (genu & body)
external capsule
extreme capsule
fornix (columns)
globus pallidus
internal capsule
lateral olfactory tract
lateral ventricle
olfactory tubercle
optic chiasma
preoptic area
putamen
rhinal fissure
septal nuclei
septohypothalamic tract
septum pellucidum
caudal forebrain & midbrain (sections F, G, H, I) -
amygdala
anterior thalamus
caudate nucleus (tail)
central gray
cerebral aqueduct
corpus callosum (body, splenium)
crus cerebri
fornix (dorsal fornix, fimbria)
hippocampus (alveus, dentate gyrus)
hypothalamus
inferior colliculus (brachium)
internal medullary lamina
lateral geniculate body
mammillary body
mammillothalamic tract
medial geniculate body
medial thalamic nucleus
midbrain reticular formation
optic tract
pineal body
posterior commissure
pulvinar
stria medullaris
stria terminalis
substantia nigra
superior colliculus
third ventricle
ventral thalamic nucleus
hindbrain (sections I, J, K, L) -
cochlear nerve
corticobulbar tract
corticospinal tract
dorsal tegmental nucleus
facial nerve (genu)
fourth ventricle
hindbrain reticular formation
inferior cerebellar peduncle
lateral lemniscus
lingula
medial lemniscus
medial longitudinal fasciculus
middle cerebellar peduncle
olivary nuclei
pyramidal tract
solitary tract (& nucleus)
superior cerebellar peduncle
transverse pontine fibers
trapezoid body
trigeminal nerve (spinal tract & nucleus)
vestibular nuclei