Sheep Eye

1. Eye Eye Eye !
• By the end of the dissection students will be
able to identify various parts of the eye.

2. EYE
The eye is an
extension of
the brain
It helps us take
in light
information
from our
surroundings.
This is how!

3. Eye brain
proximity
• Can you see :
• the optic
nerve bundle?
• Spinal cord?

4. What are the parts of the eye?
• Let’s use a diagram to help us get familiar with
the parts and pronounce them correctly!

5. Cornea
Cornea- transparent membrane that covers iris and
pupil. Focuses light on the retina.

6. Pupil, Iris, Sclera
Pupil- hole passes different amounts of light
Iris- colored part of the eye that controls the size of
the pupil
Sclera- “whites” of the eye that forms outer covering

7. Aqueous Humor, Ciliary Muscle, Lens
Aqueous Humor- nutritious fluid between the iris and
the cornea. As we age, it breaks down and we begin
to see “floaters”
Ciliary Muscles- produces aqueous humor and
controls lens shape
Lens- Bends light rays to the back of the eye –retina.
Elastic so change in shape allows for focus on
objects close up or far away

8. Retina
• Full of light
receptors
which are
sensitive
to:
• Cones-
Colour
• Rods- Light
levels
• Massive
blood
supply is
also
needed
Blind Spot- site of
optic nerve
connection

9. Vitreous Humor, Blind Spot, Optic Nerve,
Vitreous Humor- transparent jelly-like fluid that fills
the eye and refracts light
Blind Spot- area where optic
nerve attaches. No retina is
located there so information
cannot be picked up; “Blind”
Optic Nerve- sends messages
picked up by retina to the brain

10. Choroid Layer, Tapetum lucidum
Choroid Layer- lies between the
sclera and the retina it provides
the blood supply to the eye.
Tapetum lucidum- iridescent film
under the retina that provides
animals with “night vision”

11. Eye Dissection
• Before we go over the dissection, let’s review
the parts of the eye and their function

12. Cross
section
You must know:
1. Lens
2. Cornea
3. Aqueous humor
4. Pupil
5. Iris
6. Ciliary Muscle
7. Sclera
8. Vitreous Humor
9. Retina
10. Blind Spot
11. Choroid Layer
12. Optic Nerve
13. Tapetum Lucidum
Sclera
Blind
Spot
Ciliary
Choroid Layer
Taptem lucidum

13. Cut away fat using scissors

14. Anterior External Eye Structure

15. Posterior External Eye Structures

17. • Select a place to make an incision of the sclera midway
between the cornea and optic nerve. Use the point of a
surgical scissors to make a small cut through the sclera.
Fluid should ooze out of the eyeball when you have cut
deeply enough.

19. • Arrange the two hemispheres of the eye as you see in the
photograph.
• Observe the semi-fluid vitreous humor that fills the central
cavity of the eye. It is transparent in the living eye but might
be cloudy in the preserved specimen

20. • The retina lines the the posterior cavity of the eye and
extends forward to the ciliary body. Use your probe to lift
and pull the retina back from the underlying choroid layer.
• Notice that the retina is only firmly attached to the choroid at
one place. This region is the optic disc or blind spot.

21. Internal Eye Structure – Posterior Section

23. Internal Eye Structures – Anterior Section

24. Remove the lens and place against
newspaper to see that it is a
magnifier!

25. • When the lens is removed, an opening, allowing light to enter
the eye is seen. This opening, the pupil is located in the
center of the iris. Note the oblong shape of the sheep pupil,
in humans the pupil is circular.
• The back side of the iris can be seen just above the pointer in
the photograph.

27. Can you identify the parts? You will
need to to get credit during the lab

28. 1. Cornea 4. Iris 7. Ciliary Body 10. Retina
2. Sclera 5. Pupil 8. Choroid 11. Lens
3. Optic Nerve 6. Ora Serrata 9. Tapetum Lucidum 12. Vitreous Humor

29. 1. Cornea
2. Sclera
3. Optic Nerve
4. Iris
5. Pupil
6. Ora Serrata (you do not
have to know this
structure!)
7. Ciliary Body
8. Choroid
9. Tapetum Lucidum
10. Retina
11. Lens
12. Vitreous Humor

30. Clean up!
• Follow clean up procedures:
– Place all remains in a zip lock bag and place it in your
box.
– All dissecting instruments, tray and gel must be
thoroughly washed in water.
– Remove the paper towel from the tray and dispose of
it in the trash bag.
– All used gloves are to be disposed of in the trash bag.
– All goggles returned to the designated place.
– Lab stations are clean and free of water/waste.
– Each person washes their hands with soap and water.