Sheep Eye Dissection

In this lab we dissected the eye of a sheep which is very similar to the human. Firstly we look at outer portion of the eye which includes the cornea, sclera, extrinsic muscles, fatty tissue, and optic nerve. The cornea is the outermost lens of the eye. It is cloudy because it is non living. The main job of the cornea is to focus the entry of light into the eye.The sclera is the white portion of the eye, it the toughest part of the eye specifically made strong to help prevent against injury. The extrinsic muscles allow the eye to move is many directions, we have 6 which give us a larger range of motion. Fatty tissue is the yellowy stuff surrounding the eye, its main job is to cushion the eye. Finally the optic nerve (picture 2), located at the back of the eye the optic nerve transfers visual information from the eye to the brain. Next we made an incision in the sclera which separated the eye into two hemispheres. In the picture the left hemisphere consists of the vitreous humor a gelatinous substance that helps keep the shape of the eye. The right hemisphere (posterior cavity) consists of the retina and the choroid. The retina processes light information and converts it to an image. If you peel away the that tissue you reveal the black choroid. The choroid is black due to pigments, it absorbs light so it doesn't bounce around the eye. After this we removed the vitreous humor from the left hemisphere (anterior part) this then reveal the lens, ciliary body, and suspensory ligaments. The lens is convex shaped, connected to the vitreous humor, and held in place by suspensory ligaments (picture 6 shows lens when removed from cavity). The lens bends rays of light in eye. Picture 7 shows the empty anterior cavity of the eye. The ciliary body is the mushroom looking lines/folds in this cavity, they contract to help adjust the lens. The aqueous humor can be found here too, much like the vitreous it is gelatinous and helps hold eye shape. The iris and pupil are also visible. The pupil is the small opening and the iris is the colored part surrounding the pupil. The pupil controls the amount of light that can enter the eye while the iris dilates and constricts the pupil size, this controlling light flow. The eye was very complex, but also very interesting to learn about.