Eyeball Dissection

Objectives: 

          By the end of this laboratory you should be able to do the following:

• Learn the basic anatomy and physiology of the visual system.

• Successfully dissect, sketch, and identify the superficial aspect of the eyeball.

• Successfully dissect, sketch, and identify the deep aspect of the eyeball.

• Successfully dissect, sketch, and identify the lens.

• Prepare a study sheet for eyeball anatomy.

            Today’s laboratory involves the dissection of a sheep eye.  We will begin with a short lecture on the anatomy and physiology of the visual system. This material will be part of the in class quizzes and examinations, so pay close attention and take good notes. After the lecture is complete we will move on to the eye dissection. Since this laboratory involves dissection of animal tissue it is important to remember to be thankful, respectful, and subsequently take your studies, and in this case, your dissections seriously. Once again you will be using extremely sharp scalpels and probes so be careful with them. Please proceed with caution and care during your dissections.  Work in groups of no more than two. Use the dull and sharp probes to try to identify all of the brain regions discussed.  Follow the instructions carefully before you cut into your eyeballs.  A single clean slice will make viewing clearer.  I will be asking you to identify the different regions and parts of your sheep eyes so study while you dissect.  When you have completed your dissection you will need to do the exercises on the last pages of the handout (which will be given to you in class) in order to complete the laboratory.  Good Luck in your explorations.

Anatomy and Physiology of the Visual System

Vision Lecture (html)        Vision Lecture (powerpoint)

Successfully dissect, sketch, and identify the superficial aspect of the eyeball.

We receive the majority of our information through our visual senses. There is much integration of the images by our retina prior to getting to our visual cortex. The rods are critical for dim light discrimination and periphery viewing. The cones are located near the fovea and are important for color discrimination and fine details. Both the left and right eye work together to give you a clear view of the world. These exercises should help you gain a better respect for your visual system.

Step 1: Trim away excess adipose tissue (yellow material), the extrinsic eye muscles (tan material), and the connective (conjunctiva) tissue (white/clear material).  If you pull with the tweezers you will see the clear connective tissue holding the muscle and fat in place. In this taught position you can simply cut all of the muscle and fat off of the eyeball.

Step 2: Draw and color a side view of your eye specimen. Label all of the listed terms.

Step 3: Give the function of the five terms you identified.

    optic nerve: _________________________________

    sclera: _____________________________________

    cornea: ____________________________________

    pupil: ______________________________________

    conjunctiva: _________________________________

Successfully dissect, sketch, and identify the deep aspect of the eyeball.

Step 2: Gently tease apart the anterior and posterior portions of the eyeball. The fluid that escapes is the aqueous humor. Be careful not to disturb the fine tissue layer in the posterior section. That is the retina.

Step 3: Draw and color the anterior view of your eye specimen. Label all of the listed terms.

Step 4: Give the function of the four undefined terms you identified.

    aqueous humor: _______________________________________

    iris: _________________________________________________

    lens: _________________________________________________

    cilliary muscles: ________________________________________

Step 5: Draw and color the posterior view of your eye specimen. Label all of the listed terms.

Step 6: Give the function of the six terms you identified.

    vitreous humor: _________________________________

    retina: _________________________________________

    blind spot: ______________________________________

    tapetum: _______________________________________

    fovea: _________________________________________

    choroid coat: ____________________________________

Successfully dissect, sketch, and identify the lens.

Dissect out the lens so it is separate from all other tissue. Use the scalpel to cleanly bisect the lens. Draw a sketch below of what you find.

Prepare a study sheet for eyeball anatomy.

Use the colored pencils and markers to color these two "coloring book of the brain" vision anatomy panels.  Your duties for full credit in the laboratory are not complete until all panels are beautifully colored.  Have fun.

rmorrissette@palomar.edu