Sheep Eye Dissection Analysis

In this lab we dissected a sheep's eye. A sheep's eye is very similar to our own, except they need to see in low light environments, meaning that they have a tapetum lucidum on the choroid coat that allows light to reflect more onto the retina. 

Eye before the dissection 

The cloudy part seen here is the cornea. While the animal is living, the cornea is not cloudy and is only cloudy now because of the non living tissue. Compared to the sclera, the cornea is relatively thin but serves to protect the eye from debris.

Eye after all the extrinsic muscle and fatty tissue is removed

The schelera of the eye is shown above, the white part of the eye. The sclera is tough, and helps protect the eye and inside because of its toughness. The extrinsic muscles and fatty tissue attach the to sclera of the eye as well. The muscles help facilitate eye movement, and can move the eye depending on which muscles are pulled. The fatty tissue serves as a cushion for the eye and ensures that it fits snugly in the eye socket. The fatty tissue is more yellow that then the brown muscles.

Choroid coat and tapetum lucidum 

The choroid is used to nourish the back of the eye, and has several blood vessels running to and through it. The tapetum lucidum is used to reflect light onto the retina and is part of the choroid layer ( the shiny blue seen above). It is used in mostly nocturnal animals or animals that need to see in low light conditions. When we take a flash picture of an animal at night, the reason that its eyes glow is because of the tapetum lucidum and the light being reflected back. Humans don't have this structure since we aren't nocturnal and have no need to see in low light conditions to survive. The retina contains the photoreceptors for our vision and allows us to see. These signals are transmitted through the optic nerve to the brain where they are interpreted. Because of the way that the optic nerve is connected, humans have a blind spot at that point. However, this spot is barely noticeable because of the way that our right and left eyes work together to create a complete image of whatever we see.

Photo of the Lens

The lens is the structure of the eye that changes shape to focus light on the retina. It is relatively hard to compress, but is still rather squishy. Ciliary bodies and sensory ligaments surrounding the lens help shape it and focus light on the back of the retina. The lens can also become damaged or cloudy and impair the animal's vision. A cataract, for example, is a cloudy lens which prevents or reduces the amount of light that can reach the retina. Another way the eye can be damaged is glaucoma, a condition where the fluid pressure of the eye is too high and causes eye damage.

Lens, vitreous and aqueous humors removed so pupil is visible

The pupil is the opening in the iris through which light passes. The sheep's pupil is rectangular (see above) while a human's is circular.

Labeling of all the parts!