Eye lab

Eye See You…Dissection of a Cow Eye

By: K
3-28-13

On 3-28-13 in Anatomy and Physiology I got to take part in dissecting a cow eye. My lab partner was . The purpose of dissecting the cow eye was to learn and familiarize the class with the structure of the eye and to locate structures. Materials used were the cow eye, scalpel, probe, tweezers, scissors, dissection tray, gloves, paperwork / book, paper towel, ourselves, and our lab partner. My data includes the checklist, lab sheets, drawing, picture, and my lab report.

The first step was to observe the outer structure of the eye. Prior to dissection we located the optic nerve, cornea, sclera, iris, pupil, and lens. We then trimmed away excess tissue surrounding the eyeball on the sclera. Then we started a cross-section of the eye with the scalpel by making an incision behind the middle of the eyeball through the sclera. We then separated the eye into halves. We let the vitreous humor slide out. We had to tease it gently away from the lining of the eye. We then tipped the front portion over and let the lens fall out after a little teasing. We located the vitreous body, lens, hyaloid fossa, and zonula ciliaris. We picked up the lens with a pair of forceps and dried it with a paper towel. We attempted to observe its ability to magnify but we weren’t able to see much. If we would have been able to let it dry overnight we probably would have been able to see more. We then turned the eye so we were looking at the cornea. We cut the front of the eye around the outside of the outside of the cornea to remove the cornea. We cut the cornea in half to observe its thickness. We picked up the back half of the eye and located the retina. We located the optic nerve / blind spot when we turned the eye over. We pinched the nerve with the forceps. We moved the retina so that we could see the metallic – looking tissue at the back of the eye which is the choroid. The portion of the choroid that appears blue is the tapetum. When we were done we disposed of the cow eye in the garbage and cleaned up as directed.

The pupil is the circular opening in the center of the pigmented, or colored, iris of the eye, through which light passes to the retina. The iris is an involuntary muscle that controls how much light enters the eye by changing the size of the pupil. The retina is the light – sensitive membrane that lines the back wall of the eyeball. The rods and cones are light – sensitive cells on the sensory layer of the retina. Cones allow a person or animal to see color, and rods enable them to see shades of gray and motion. The aqueous humor is a clear fluid that helps the cornea maintain its rounded shape. The cornea is the tough, clear covering over the iris and the pupil that helps protect the eye. The lens is a clear, flexible structure that bends light to project an image onto the retina. The optic nerve is the bundle of nerve fibers that transmits information from the retina to the brain. Vitreous humor is the thick, clear jelly that helps give the eyeball its shape.

Overall I enjoyed the cow eye dissection. It helped me better understand where things are located. I thought the blue coloring was pretty neat. I also thought the lens was interesting and it would have been cool to let it dry overnight to be able to see how much it magnifies… I am including one drawing that I drew and one picture that I found that I thought was interesting.