Thursday, December 9, 2010

Michelle and Megan 12/09/10

Hi! It’s Michelle and Megan again. We are starting a project on the development and anomalies of the eye. So far we have researched how the eye develops.

The eye starts off as a tiny groove in the folds of the brain tissue. Later, as the folds become the forebrain, the groove turns into a bump, known as the optic vesicle. The optic vesicle is connected to the forebrain by a thin hollow tube, called the optic stalk, which allows the brain to send messages to the eye. The optic vesicle then comes into contact with a layer of the skin known as ectoderm. The ectoderm thickens and moves inward to form the lens vesicle. Meanwhile, the optic vesicle also moves inward to begin forming the two layers of the retina, which later join together. The lens vesicle then increases in length and small fibers are formed connecting the lens to the retina. The thin membrane that covers the lens disappears to provide communication between the two chambers of the eye. The cornea is formed by the combination of a layer of the ectoderm, stroma and epithelial layer. A groove in the back of the optic vesicle allows the hyaloid artery to enter the eye. Later, the hyaloid artery disappears leaving behind a hollow path known as the hyaloid canal, and the optic stalk’s walls grow from an increase in fibers turning the optic stalk into the optic nerve.

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