Cow Eye
Dissection
Objectives
By the end of this lesson, students will
be able to:
• Demonstrate proper dissection
safety techniques.
• Explore and identify the external
anatomy of the cow eye.
• Explore and identify the internal
anatomy of the cow eye.
• Compare and contrast human and
cow eye anatomy
• Evaluate how the structure of the
parts of an eyeball relate to its
function.
Arkansas Frameworks
Grade 6
Grade 7
Grade 8
LS.2.6.1
LS.7.1.2
LS.8.1.8
LS.2.6.2
LS.7.1.3
LS.2.6.3
LS.7.1.4
LS.2.6.4
LS.2.6.6
Why Dissect?
Dissection allows students to:
• Practice safety procedures
• Construct science process skills
• Organize the hierarchal
relationships of tissues, organs,
organ systems and organisms
• Compare similarities and
differences among organisms
• Connect organism complexity to
its diversity
Materials
• Cow eye specimen
• Dissection tray or
Styrofoam meat tray
• Dissection kit with
scissors, pins, scalpels,
tweezers and probes
• Gloves
• Goggles
• Plastic aprons
• Student worksheets
General Safety Rules
• The classroom should
be well ventilated
• Work space should be
flat and free of
unnecessary materials
• All equipment should
be clean and unbroken
• ABSOLUTELY no eating,
drinking or gum
chewing during
dissection activities
Sharp Instrument Safety
• Prepare a container for disposal of
broken instruments or glassware
• Dispose of the container intact and
replace with a new one to prevent
others from being cut
• Inventory all sharp items to ensure
all objects remain in the classroom
• Ensure that students use sharp
instruments properly.
• Remind students they should always
cut away from themselves and
others
Before we proceed
While dissecting, be respectful of your
lab partners and of the specimen you
are about to explore, observe and
learn from.
Take extra care with your dissection
tools. Your scissors are your most
important tool, but be sure to handle
them carefully and always double
check before cutting.
If you have any questions, please ask.
Attire
• Wear Gloves
• Wear Aprons
• Wear Goggles (ANSI
Z87.1)
Always!! No
Exceptions!!!!
Interesting Facts
Look all around without moving
your head. Look up, look
down, look side to side and all
around. You have six muscles
surrounding your eye that
allows you to look in different
directions. However, cows only
have four muscles. Therefore,
they can only look up, down,
left and right. They are not
able to roll their eyes like you
can.
Interesting Facts
• Reach up and feel around
your eye. Can you feel the
bone of your skull? Fat
surrounds your eyeball to
keep it from bumping
against the bone and getting
bruised.
• The fat and muscle
surrounding the cow eye is
cut away when dissecting in
order to see the eyeball.
Muscle
Fat
Optic Nerve
External Anatomy
• Obtain a cow eye,
place it in your
dissecting pan and
rinse with water.
• Observe the white
part of the eye. This
is the sclera. The
sclera is the outer
covering of the
eyeball.
Sclera
Sclera
Fat
External Anatomy
• Locate the eyelids.
• Observe the blue portion of
the eye. This is the cornea.
The cornea starts out clear
but becomes cloudy after
death.
• Look through the cornea
and locate the iris. The iris
is a round black tissue.
• Locate the pupil. The pupil
is the round opening in the
center of the eye.
Eyelid
Cornea
Pupil
Iris
External Anatomy
• On the opposite side
of the cornea, locate
the optic nerve. The
optic nerve is a white
cord on the back of the
eye about 3 mm thick.
• The following video
will review what we’ve
learned about the
external anatomy of
the eye.
Optic Nerve
Incision 1
• Now remove the fat and
muscle surrounding the
eye using caution not to
remove the optic nerve.
• Place the eye in the
dissecting pan so it is
again facing you. Using
your scalpel, pierce the
white part of the eye
(sclera) just behind the
edge of the cornea.
Make a hole large
enough for your scissors.
Sclera
Incision 2
• Using your scissors,
carefully cut around
the eye using the edge
of the cornea as a
guide. Lift the eye and
turn it as needed to
make the cut and be
careful not to squeeze
the liquid out of the
eye.
Internal Anatomy
• If a fluid should
ooze out, it is called
the aqueous
humor. This fluid is
clear and made of
protein and water.
The aqueous humor
helps give the eye
its shape.
Aqueous Humor
Internal Anatomy
• After completing the
cut, carefully remove
the front of the eye
and lay it in your
dissecting tray.
• Place the back part of
the eye in the pan
with the inner part
facing upward.
Internal Anatomy
• Observe the tough tissue
of the removed cornea.
Cut across the cornea with
your scalpel to note its
thickness.
• Observe the iris. The iris is
the black tissue of the eye
that contains curved
muscle fibers
• Locate the ciliary body. It
is located on the back of
the iris that has muscle
fibers to change the shape
of the lens.
Ciliary
Body
Iris
Pupil
Internal Anatomy
• Locate the lens. It can be
found by looking through
the pupil.
• Using your scalpel and
dissecting needle,
carefully lift and work
around the edges of the
lens to remove it.
• The gel the lens is
suspended it is called the
vitreous humor.
Retina
Lens
Vitreous
Humor
Internal Anatomy
• Observe the back of the eye
after the lens has been
removed. It should be
shaped like a bowl. On the
inside of the bowl is a thin
film with red blood vessels
running through it. This is
the retina.
• The retina is attached to the
back of the eye at just one
spot. It is called your blind
spot. Use forceps to
separate the retina from the
back of the eye to see the
layer beneath it.
Retina
Blind
Spot
Internal Anatomy
• The layer beneath the
retina is called the
tapetum. It is a shiny,
blue-green layer
designed to assist night
vision by reflecting
light back through the
retina. Humans do not
have a tapetum. This
structure is responsible
for the shining of
animals eyes at night.
Tapetum
Clean Up
• Place all dissecting specimens and
parts into approved container
provided by the instructor.
• Wash dissecting equipment and
trays in dilute bleach solution
provided by the instructor.
• Dry equipment thoroughly to
prevent rusting.
• Clean table tops with dilute bleach
solution provided by the
instructor.
• Wash hands thoroughly before
leaving the classroom.
Resources
Cow Eyeball Dissection:
http://www.exploratorium.edu/learning_studio/cow
_eye
Cow Eye Dissection, worksheet, lab:
http://www.dishs.org/webpages/dalpoggettom/Phis
icalScience/coweyedissection.htm
Cow Eye Dissection:
http://www.cas.vanderbiltedu/bsci111b/eye/coweye/cow-eye-dissection.htm
Dissection Narrative:
http://www.seq.org/ca_science/Silva/HumanBio/Units/Nervous/eyedisse
ction.doc