Human Eye

Essay by sunnyharHigh School, 10th grade May 2004

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The eye is an essential part of the human body. The human eye consists of many parts that interact and function to their purpose. The parts of the eyes are as follows:

The resilient outer layer of the eye is called the sclera. Its purpose is to maintain the shape of the eye. The front sixth of this layer is clear and is known as the cornea. The muscles attached to sclera that prohibits us to freely move the eye are called the extra ocular muscles. As we go in deeper, we would approach the choroids. The choroids supplies blood the delicate structures of the eye. The front parts of the choroids are the ciliary body and the iris. The ciliary body serves as a muscular area that is attached to the lens, which permits us to contract and relax the lens for focusing. The iris is colored part of our eyes.

The color of the iris is a result of the color of the connective tissue and pigment cells. The lesser the pigment the lighter the eyes. The dilator and sphincter are the two muscles in the iris. The dilator decreases the size of the iris and thus the pupil becomes larger. This allows more light to enter the eye. The sphincter on the other hand does the opposite, allowing less light into the eye. Pupil size can change from 2 mm to 8 mm. This means that by changing the size of the pupil, the eye can change the amount of light that enters it by 30 times. The innermost layer is called the retina. Inside are rods and cones. The rods allow us to see in dark places and the cones allow us to see colour and detail. In the back of the eye is where...