COLEGIO AGUSTINIANO CIUDAD SALITRE
AREA DE CIENCIAS NATURALES Y EDUCACIÓN AMBIENTAL
BIOLOGÍA GRADO OCTAVO
LABORATORY PRACTICE # 2
STRUCTURE OF THE BRAIN
OBJECTIVES:
you can find the third ventricle. There are other ventricles within
1.
List and describe the principal structures of the brain
the brain, but those are the easiest to locate in a preserved
2.
Identify important parts of the brain in a preserved
specimen. The white area between those two ventricles is the
specimen
fornix. The fourth ventricle is the space under the cerebellum.
PROBLEMIC QUESTION:
4.
Inferior to the corpus callosum is a round structure known as the
Why we can study the anatomy of the human brain to analyze the
thalamus. It seems it almost perfectly centered. Just behind the
brain of another animal such as sheep or lamb?
thalamus is the pineal body (gland). The hypothalamus is also
round shaped but is lower and toward the front of the brain.
THEORETHICAL FRAMEWORK
5.
The sheep brain is quite similar to the human brain except for
the side view of the brain. Gently separate the cerebellum at the
proportion. The sheep has a smaller cerebrum. Also the sheep brain is
oriented anterior to posterior whereas the human brain is superior to
transverse fissure, which separates it from the cerebrum.
6.
inferior.
Within the cerebellum, you can see the arbor vitae, named such
because the white lines resemble a tree
External Structure of Brain
1.
The pons, medulla, cerebellum and spinal cord are also visible in
7.
When you use a scalpel to cut a cross section of the cerebrum in
The tough outer covering of the sheep brain is the dura
the occipital lobe area, you should be able to see the color and
mater, one of three meninges (membranes) that cover the
texture differences of the white matter and the gray matter.
brain.
2.
The most prominent feature of the brain is the cerebrum which is divided into nearly symmetrical left and right
hemispheres by a deep longitudinal fissure.
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: frontal lobes / parietal lobes /
occipital lobes / temporal lobes
4.
The smaller, rounded structure at the back of the brain is the
cerebellum. The cerebellum has smaller gyri that are roughly
parallel to one another.
5.
The most prominent structure on the ventral side of the brain
is the optic chiasma, where the two optic nerves cross over
each other and form an “X” shape.
6.
The pituitary gland is a large round structure under the
chiasma
7.
Toward the front of the brain are two prominent round
structures, the olfactory bulbs.
8.
Toward the back of the brain, in order from the optic chiasma
are bulges that indicate the midbrain, the Pons, and the
medulla.
9.
Just behind the optic chiasma is a raised area or bump that
indicates the infundibulum (also known as the pituitary stalk).
This is where the pituitary was attached to (which was
probably removed with the dura mater).
10. Occulomotor nerves may be visible to each side of the

Herramientas de disección
11. The bumps you see (kind of resemble a “butt”) are the

Lámina de icopor de 30 cm X 30 cm
superior colliculi. The smaller ones underneath are inferior

Cerebro de cordero o de res
colliculi.

Periódico

Palillos

Cintas separadoras
pituitary gland (or stalk).
12. The tiny nub of the pineal gland.
Internal Structure of Brain
1.
2.
3.
MATERIALS: (En el pre informe debes escribirlos en inglés)

Bata
right hemisphere.

Guantes
The corpus callosum had been connecting the two cerebral

Tapabocas
hemispheres and can now be clearly seen in the brain section.

Gafas de protección
The tiny space within the corpus callosum (which hold

Toalla de manos
The longitudinal fissure
separates the brain into the left and the
cerebrospinal fluid) is called the lateral ventricle. Underneath it,
PROCEDURE:(En el pre informe lo escribes en forma de diagrama de
You need to know the difference between a nerve and a
flujo “Flowchart”)
tract. On this screen also note the longitudninal fissure and
the cranial nerve called the oculomotor (III) nerve which
1.
2.
Before beginning the dissection of the sheep brain you will
helps control eye movements.
need to know the terms used to specify the location and
Find the medulla (oblongata) which is an elongation below
relative location of various brain structures .Read carefully
the pons. Among the cranial nerves, you should find the very
the information of the following link: (IMPORTANT: Print
large root of the trigeminal nerve.
one file per group)
From the view below, find the IV ventricle and the
http://psych.hanover.edu/classes/neuropsychology/Syllabus/
cerebellum.
Labs/DISSECTION.pdf
From the view below, you can see both the superior
The procedure is divided into three main sections:
colliculus(i) and inferior
Examination of the Exterior of the Brain, Examination of the
colliculus(i). The superior and inferior colliculi are part of the
Mid-Sagittal Plane of the Brain, Examination of two Frontal
midbrain and collectively known as the Tectum.
Cuts.
Note the large gyrus called the Uncus. Posterior to the uncus
Examination of the Exterior of the Brain.
find the Hippocampal gyrus so named because the
The first portion of the dissection will be a detailed
hippocampus lies dorsal to it. In the middle of the brain you
examination of the brain surface. No actual cutting of the
will find the Mammilary Bodies which are part of the limbic
brain is required for this portion of the dissection. As you
system and play a role in memory. Also find the Rhinal
proceed to identify the listed parts of the brain, note their
Fissure which defines one boundary of the limbic system.
structure and how they are related to other parts of the brain.
Now find the four lobes of the cerebrum: frontal, parietal,
First examine the exterior of the entire brain. You may be able
temporal, and occipital. The Frontal Lobe is bounded by the
to see one or two of the three layers of the meninges, the
Ansate Sulcus and the Pseudosylvian Sulcus. The Parietal
dura mater, the arachnoid layer, and the pia mater. The
Lobe is bounded by the Ansate Sulcus, the Suprasylvian
meninges are the protective coverings, which enclose the
Sulcus, and the Lateral Sulcus. The Temporal Lobe is
brain and spinal cord. The dura mater, the tough outer layer,
bounded by the Pseudosylvian Sulcus and the Suprasylvian
will have been mostly removed when the brains were
Sulcus. The Occiptial Lobe is inside the Lateral Sulcus.
prepared for the dissection; however, some of the dura mater
Examination of the Mid-Sagittal Cut
may remain near the base of the brain. The arachnoid layer,
Do not proceed to the next step before checking with the lab
the middle layer, and pia mater, the inner layer, are still likely
instructor No you will make a mid-saggital cut. Hold the
to cover the brain. The pia mater follows the gyri and sulci
brain level and flat and cut along the longitudinal fissure. On
and most likely is still on your specimen and may be
this screen you can find the lateral ventricles (and septum
indistinguishable from the brain. Blood vessels are between
pellucidum), third ventricle, the cerebral acqueduct (which
the arachnoid layer and the pia mater. These vessels and the
connects the third and fourth ventricle), and the tegmentum,
arachnoid layer will obscure your view of the sulci making the
the other part of the mid brain.
identifications below difficult and confusing. Before
Can you find the superior and inferior colliculi on this view?
proceeding with the identification of structures on the surface
This is a more detailed view of the mid-saggital section. Here
of the brain you will need to remove the arachnoid layer and
you can find the largest of all of the commisures (a band of
the blood vessels. Use your tweezers and be very careful
fibers that connects the two sides of the central nervous
because the brain is soft and easily damaged.
system). This is the corpus callosum. It is so big that
Next locate the area referred to as the brain stem. This area
different parts of it get different names. So you have the
is made up of the pons, medulla, and cerebellum. Find also
genu, splenium, and the body of the corpus callosum. In
the root where the pituitary gland was attached to your brain.
addition note the pineal body famous from our discussion
The pituitary gland may have been there when you first
of Decarte), the hypothalamus, and the massa intermedia.
cleaned your brain.
Now you are looking at the cerebellum. Notice the pattern of
Examine the ventral surface of the sheep brain. The next
grey and white matter. To some it resembles a tree or bush
several steps will view this surface of the brain. A pair of
and is called as a result the arbor vitae (the tree of life –ok a
olfactory bulbs may be seen, one under each lobe of the
bit strong).
frontal cortex. Several important parts of the visual system are
Examination of the Frontal Cuts
visible in the ventral view of the brain. Muscles, other nerves
Do not proceed to the next step before checking with the lab
and fatty tissue may surround the optic nerve on your
instructor.
specimen. After inspection of these, use a scalpel to cut away
Find the putamen, globus pallidus, and caudate nucleus.
this muscle tissue, leaving as much of the optic nerve as
These structures are collectively known as the Basal
possible protruding from the ventral side of the brain. Notice
Ganglia. In addition you should see the crossing of the
that as the optic nerves from the right and left eyes proceed
anterior commissure right above the optic chiasm. While not
towards the center of the brain, they meet in the optic
labeled see if you can see the corpus callosum and the
chiasm (named for the Greek letter chi, C, which it
lateral ventricles.
resembles).
In the optic chiasm, there is a partial crossover of fibers
carrying visual information. Any time fibers in a tract or nerve
cross the midline of the brain it is called a decussation. After
the optic chiasm, visual information proceeds along the optic
tract toward the visual cortex.
Names:_______________________________________
Class #
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ANALYSIS OF RESULTS.
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Score
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Date:__________________________ Grade: ________
Topic: Lab practice structure of brain
RESULTS

Match the structure to the description
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
looks like a butt'
leathery covering over the entire brain
cauliflower, the area toward the back of the brain
behind the colliculi, looks like a little nub
looks like a "tree"
the rounded part of the brain stem
shaped like an X
large area under the corpus callosum
space for fluid between the corpus callosum and the fornix
contains nerves, connects to the far front of the brain
Organize the description of your observations in the following
table, In addition for your lab report, print and paste photos of the
brain observed in the lab.
1. ___ Arbor Vitae
2. ___Lateral Ventricle
3. ___Optic Chiasma
External
structure
4. ___Superior Colliculi
of the brain
5. ___Dura Mater
6. ___Cerebellum
7. ___Pineal Gland
8. ___Thalamus
9. ___ Pons
10. ___ Olfactory Bulb
Internal
structure
of the brain

Label this brain

What conclusions can you make about the brain
from this examination?
Before you clean up your brain, your teacher will check to make sure
you know the structures on this page. You will be given 1-5 items on
the list to locate. Alternatively, you may be shown slides
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
Thalamus
Hypothalamus
Superior & Inferior Colliculi
Arbor Vitae
Cerebellum
Cerebrum
Optic Chiasma
Transverse & Longitudinal Fissue
Corpus Callosum
Lateral Ventricle
pineal body
pituitary gland
fornix
spinal cord
medulla
pons
midbrain
olfactory bulb
sulcus
gyrus
1. _________________________________
1______________________________________________________________
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2______________________________________________________________
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2. _________________________________
3. _________________________________
4. _________________________________
5. _________________________________
3______________________________________________________________
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