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Sheep Eye Dissection Lab
Purpose: The purpose of this lab is to dissect a sheep eye, which is similar to the eyes of all mammals
including humans, to gain a better understanding of the structure and function of the parts of the eye.
Hypothesis:
Materials:
Procedure:
1. Locate these external structures and record your observations in the results section.
Optic nerve
Sclera
Cornea
Iris
Pupil
Muscles
Fat
Eyelids
2. Have the eye facing up towards you. Puncture the sclera with the tip of your scissors (or a scalpel)
about 1cm outside the edge of the iris.
3. Being careful not to squeeze the liquid out of the eye, use the scissors to cut a circle around the
eye, staying 1 cm from the iris. Pull the cut portion away from the sclera and lay it face down on
your tray.
4. Carefully remove the lens and the vitreous and aqueous humors from the eye, notice the
difference between the aqueous and the vitreous humor.
5. Examine the lens carefully. Attached to it are the fine ciliary muscle fibers that controlled the
shape of the lens. In a fresh or living eye the lens would be clear, but once preserved they become
cloudy. Using your probe and forceps to gently lift and work around the edges of the lens.
6. Next examine the back portion of the eye. You will see a thin, wrinkled white layer of tissue that is
the retina. It will be attached to the optic nerve at the blind spot. Use your forceps and scissors to
cut away the retina.
7. At the very back of the eye is a bluish layer called the tapetum. This layer is a reflective surface
found only in some animals with good night vision.
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8. Identify these internal structures and record your observations in the results section.
Vitreous humor
Aqueous humor
Iris
Pupil
Lens
Ciliary muscles
Retina
Blind spot
Tapetum
9. Dispose of all materials according to the teacher’s directions and clean your work area.
Results:
External Observations
What does it look like?
What is its function?
Optic Nerve
Sclera
Cornea
Iria
Pupil
Muscles
Fat
Eyelids
Internal Observations
What does it look like?
Vitreous humor
What is its function?
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Aqueous humor
Iris
Pupil
Lens
Ciliary Muscles
Retina
Blind Spot
Tapetum
Analysis Questions:
1. What parts were easy to locate and which were difficult to identify?
2. Number these in the order in which light passes through them to form an image inside the eye.
______
cornea
______
lens
______
optic nerve
______
pupil
______
retina
______
vitreous humor
______
aqueous humor
3. Describe the path light travels through the eye to reach the brain.
4. Where are the photoreceptors found in the eye?
5. What are the two types of photo receptors?
6. What surprised you most about this dissection?