Lab 10
Gross Anatomy of the Brain and Cranial Nerves
Autonomic Nervous System
Chapter 14
Chapter 16
Brain and Cranial Nerves
Identifying External Brain Structures (Consult Lab Exam Review Sheet)
Identifying Internal Brain Structures (Consult Lab Exam Review Sheet)
Cranial Nerves. Cranial nerves are shown in Text Figure 14.18. (Consult Lab Exam
Review Sheet) but will be tested on the figure below.
There are several mnemonics for learning the order of the cranial nerves. Two are below:
The first letters of the nerves are in bold.
Oh, Oh, Oh, to touch and feel very good velvet, Ah.
On occasion our trusty truck acts funny. Very good vehicle anyhow
Dissection: The Sheep Brain. Consult Lab Exam Review Sheet.
You are not required to touch the dissection, but you are responsible for the material.
Objective:
Identify important parts of the sheep brain in a preserved specimen. Refer to the Lab Exam Review list.
Materials: Dissection tools and trays, lab glasses, lab gloves, preserved specimen.
A. External Sheep Brain: The sheep brain is quite similar to the human, although there are some
important differences.
1. The tough outer covering of the sheep brain is the dura mater, one of three meninges (membranes) that
cover the brain. You will need to remove the dura mater to see most of the structures of the brain. You
can see some structures on the brain before you remove the dura mater. Take special note of the pituitary
gland and the optic chiasma, optic nerves and optic tracts. The pituitary gland and attached infundibulum
are likely to be pulled off when you remove the dura mater. Note the deep transverse fissure separating the
cerebrum from the cerebellum.
(I will demonstrate this.)
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. Pull the hemispheres apart gently and observe the
whitish corpus callosum, a large commissure that connects the right and left hemispheres of the brain.
3. The surface of the cerebrum is covered with large folds of tissue called gyri. The grooves between the
gyri are sulci. The deeper indentations are called 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,
and temporal lobes. Use the blunt probe to push under the pia mater, a thin membrane covering the surface
of the brain. Move the probe from side to side to release the pia mater.
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. Compare the gyri of the cerebellum to that of the cerebrum.
5. Turn the brain over so that the cerebrum is down. The most prominent structure visible 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. The optic tract runs from the optic chiasma to the brain. Just posterior to the optic chiasma is the
mammillary body. You may also be able to see where the infundibulum attached the pituitary gland to the
brain.
Optic Tract
Optic Nerve
6. Toward the front of the brain are two prominent round structures, the olfactory bulbs that connect to the
olfactory tracts. The olfactory nerves (Cranial Nerve I) enter the olfactory bulbs from the nasal cavity
through the cribriform plate.
7. Identify the midbrain, the pons, and the medulla oblongata.
8. Carefully bend the cerebellum to see the dorsal surface of the midbrain. The four domes are the
superior colliculi and the inferior colliculi.
9. If you gently push those structures down, you can see the rounded pea-sized pineal gland.
B. Internal Sheep Brain.
1. Use a knife or long-bladed scalpel to cut the specimen along the longitudinal fissure. This will allow you
to separate the brain into left and the right parts. Lay one side of the brain on your tray to locate the
structures visible on the inside.
2. The corpus callosum is a commissure that connects the right and left cerebral hemispheres.
3. You may see a membrane – the septum pellucidum – covering the opening to the lateral ventricle.
Underneath it, you can find the third ventricle, which surrounds the interthalamic adhesion (intermediate
mass of the thalamus). This is labeled as the thalamus in the picture. The white area between those two
ventricles is the fornix. The fourth ventricle is the space under the cerebellum.
4. Just behind the thalamus is the pineal body (gland). The hypothalamus is the area below the thalamus
that points to the area of the optic chiasma.
5. The pons, medulla, cerebellum and spinal cord are also visible in the side view of the brain. Gently
separate the cerebellum at the transverse fissure, which separates it from the cerebrum.
6. Within the cerebellum, you can see the arbor vitae, named such because the white lines resemble a tree.
7. Compare the size of the cerebral hemispheres, brain stem and olfactory lobe in the sheep brain to the
preserved human brain at the front of the lab. You will be asked which is larger in the human, which is
larger in the sheep and which is the same size in the human and the sheep in the online exercise.
8. Use a scalpel to cut a cross section of the cerebrum in the occipital lobe area. You should be able to see
the color and texture differences of the white matter and the gray matter.
6. You can also push the colliculi down to show the pineal body from this side.
Modified from http://www.biologycorner.com/anatomy/sheepbrain/sheep_brain_dissection_guide.html
Figures from http://www.biologycorner.com/anatomy/sheepbrain/sheep_dissection.html
Name____________________________
Lab Section ________________
Fill in the name, number in Roman numerals, type (either sensory or mixed), and
associated part of the body for each of the cranial nerves. Note: some nerves are listed as
motor, but they do have some sensory branches, so consider them mixed.
Name
Number in
Roman
Numerals
Type
Either
Sensory or
Mixed
Brain
Association
Body Part
Association
Simplify from
Table 14-9
Forebrain
Forebrain
Midbrain
Midbrain
Pons
Pons
Pons
Pons
Medulla
Oblongata
Medulla
Oblongata
Medulla
Oblongata
Medulla
Oblongata
Note: Cranial nerves 3, 4, 6, 11 and 12 are considered primarily motor. Fibers from
proprioceptors are ignored. We will consider them mixed for this exercise.
For the Lab Exam
External Anatomy of Brain - from models and figures in text, Chapter 14 or PAL
 brain stem
 longitudinal fissure
 central sulcus
 mammillary bodies
 cerebellum
 medulla oblongata
 cerebral hemispheres
 occipital lobe
 corpora quadrigemina
 olfactory bulbs and
tracts
 frontal lobe
 optic chiasma
 gyri
 optic nerves
 lateral sulcus
 optic tracts







parietal lobe
pituitary gland
pons
postcentral gyrus
precentral gyrus
sulci
temporal lobe
Internal Anatomy - from models and figures in text, Chapter 14 or PAL
 arbor vitae
 gray matter
 basal nuclei (as a group)
 hypothalamus
 cerebral aqueduct
 intermediate mass of thalamus
(interthalamic adhesion)
 choroid plexus
 pineal body
 corpus callosum
 white matter
 fornix
Membranes –from Chapter 13-2
 dura mater (two layers)
 arachnoid mater
 pia mater


Ventricles – from figure
 location of ventricles
 route of circulation of spinal fluid
Identify on Sheep Brain
 arbor vitae
 cerebellum
 cerebral aqueduct
 cerebral
hemispheres
 cerebral peduncles
 corpora
quadrigemina
 corpus callosum
 dura mater
Cranial nerves –from figure
 identify on attached figure (F. 14.18)
 information from chart on handout









fornix
gray matter
intermediate mass of
thalamus
mammillary body
medulla
midbrain
olfactory bulb
olfactory tract
optic chiasma
Spinal Cord and Spinal Nerves – Chapter 13
Identify on figure
 cauda equina
 cervical enlargement
 cervical spinal nerves
 lumbar enlargement
Identify on figure
 anterior horn
 arachnoid mater
subarachnoid space
arachnoid villi
 central canal
 dorsal root








optic nerve,
optic tract
pia mater
pineal body
pituitary gland
pons
ventricles
white matter
 lumbar spinal nerves
 sacral spinal nerves
 thoracic spinal nerves


dura mater
gray matter


lateral horns
pia mater
 posterior horn
 spinal nerve
 ventral root
 white matter
Identify on figure
 brachial plexus
 cervical plexus
 lumbar plexus
 sacral plexus
Identify on figure
 phrenic nerve
 Identify on figure
 median nerve
 musculocutaneous nerve
 radial nerve
 ulnar nerve
Identify on figure
 femoral nerve
 Identify on figure
 sciatic nerve
Identify on model of spinal cord
 gray matter
 white matter
 central canal