Cow Eye Dissection

Cow Eye Dissection

For this lab exercise, we will examine the internal anatomy of the cow eye. Cow eyes are relatively inexpensive, and are particularly useful because of their size. Moreover, the basic structures are similar to those in the primate eye. Most diagrams of the eye show a cross section to illustrate the relative locations of all the important internal structures. However, we are going to divide the eye into front and back hemispheres and examine each half separately. This will allow us to examine the lens and the ligaments that hold it in place in the front half and to view most of the retina, still intact in the back half of the eye.

Materials:

cow eye

surgical gloves

scalpel

dissecting scissors

small container of water (large enough to immerse half of the eye)

Procedure:

Imagine the eye is a globe and divide it into front and back hemispheres:

DO NOT simply cut through the entire eye with your scalpel, but follow these steps:

1.Make a small incision in the sclera. This is the tough white outer coating.

2.With dissecting scissors cut around the equator. Separate the two hemispheres carefully.

3.Note the jelly like substance inside. This is the vitreous humor. Carefully remove it so as not to tear the retina.

4.Place the back hemisphere in a dish of water. The retina should float off the back of the eye easily.

5.Note the black layer behind the retina. This is the choroid. You may also note a shiny blue region on the surface of the choroid. This is the tapetum, which reflects light. The human eye does not have a tapetum.

6.Also locate the optic disc. This is the region where axons of retinal ganglion cells (the optic nerve) leave the eye.

7.Take the front half of the eye and carefully cut the suspensory ligaments which surround the lens.

8.Now you may remove the lens. Note how hard it is. You may want to cut it to see the onion like layers.

9.Identify and examine the ciliary body, iris, aqueous humor and cornea which are all in front of the lens.

10.Note that the pupil is not a structure per se, but rather a hole surrounded by the iris.

CLEAN UP!!!!