1. Eye Dissection

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?

5. Cornea- transparent membrane that covers iris and pupil
Cornea- transparent membrane that covers iris and pupil. Refracts light into the eye. Clear portion of the Fibrous Tunic.

6. Sclera- “whites” of the eye that forms outer covering or Fibrous Tunic
Sclera- “whites” of the eye that forms outer covering or Fibrous Tunic. It protects the eye & gives the eye its shape.
Sclera
Cornea

7. Can you find the fibrous tunic on your eye?

8. Can you find the extrinsic muscles around the eye? How many are there?

9. Can you find any other accessory eye structures?

10. Can you find the Optic Nerve? What does it do?

11. Why does the eye have so much Adipose connective tissue surrounding it?

12. Using the eye’s weight & gravity, trim all excess adipose, muscles, & accessory structures away from the eye. Leave the Optic nerve in tact.
When you’re finished, your eye should look like the eye below.

13. 1. Place the eye in the dissecting pan so the cornea is facing you. 2
1. Place the eye in the dissecting pan so the cornea is facing you. 2. Hold the eyeball gently w/your thumb & forefinger & using your scalpel, pierce the cornea just large enough for your scissors. 3. Using your scissors make a transverse cut through the cornea & then empty the Aqueous Humor from the anterior chamber of the eye onto your lab tray. Aqueous Humor is the nutritious fluid between the iris and the cornea. As we age, it breaks down and we begin to see “floaters”

14. Allow the aqueous humor to flow onto your tray.

15. Using your scalpel, pierce the sclera inferior to the cornea & iris
Using your scalpel, pierce the sclera inferior to the cornea & iris. Then using scissors, carefully cut around the superior portion of the eye.. Do not squeeze the eye too tightly, so as not to push the lens &/or vitreous humor out of the eye. Lift the eye & turn it as needed to make the cut.

17. As you are cutting the top off of your eye, what 3 structures are you cutting through?

18. After completing the cut, carefully remove the front of the eye and lay it in your dissecting pan. Place the back part of the eye in the pan with the inner part facing upward.

19. Look @ the Internal Eye Structures – Anterior Section

20. Place the cornea on the hard surface of the dissecting tray (below the blue mat). Using your scalpel, make small cuts into the cornea & describe the sound it makes. It should crunch like you were cutting into an onion.

21. Can you see the Pupil- hole that light passes through & the Iris- colored muscle of the eye that controls the size of the pupil, thus controlling the amount of light that enters the eye. Note the oblong shape of the
sheep pupil, in humans the pupil is circular.
Cow Eye
Iris
Pupil
Sheep Eye
Human Eye

22. Using your fingers or tweezers, gently pull the Iris away from the interior, anterior portion of the eye that you just removed. Notice the color of the iris & the ciliary bodies on the edges of the iris..

23. Notice the Ciliary bodies on the dorsal aspect of the Iris & attached to the lens.

24. Ciliary Muscles- produces aqueous humor and controls lens shape
Suspensory Ligament- hold the lens in place.
Lens- Focuses & magnifies the image onto the retina. It is elastic so change in shape allows for focus on objects close up or far away

25. Separate the Lens (the marble looking structure) from the vitreous humor. Leave the vitreous humor in the tray.

26. Vitreous Humor- transparent jelly-like fluid that fills the posterior eye and nourishes it & holds the retina in place.

27. What does the Lens do?

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

29. Retina AKA: Sensory Tunic
Blind Spot- site of optic nerve connection
Full of photo receptors which are sensitive to:
Cones- Colour
Rods- Dim light/black & white

30. Optic Disc is the area where optic nerve enters the retina
Optic Disc is the area where optic nerve enters the retina. Can you find it? Which photo receptors are found there?

31. Choroid Layer- lies between the sclera
and the retina & is the black layer. It
provides the blood supply to the eye
therefore it’s called the what layer?
Tapetum lucidum- iridescent film under the retina that provides animals with “night vision”

32. Tapetum Lucidum

33. Can you identify the parts?
1. Cornea Sclera Optic Nerve Iris Pupil Sclera Ciliary Body Choroid Tapetum Lucidum Retina Lens Vitreous Humor

34. Clean up! Scrape all eye parts into the trash can.
Wash w/soap & water all instruments; dry them & return them to the teacher.
Wash the tray & mat w/soap & water; Dry them & put them back on your table.
Wipe down your table w/the table cleaner (in the spray bottles) & return your lab instructions.
Wash & dry your gloves & goggles & return them to their proper place.