Vision Photoreceptors and Ocular Disorders.docx

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Vision, Photoreceptors, and Ocular Disorders Samantha Whitman Alden Senior High School
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Vision, Photoreceptors, and Ocular Disorders 1 The human eye is composed of many different parts, and its complexity does not cease to amaze even modern scientists and researchers. Humans do not ‘see’ with their eyes as many would like to think, but the eyes act as a messenger of sorts to the central nervous system. What is picked up by the eye are photons being bounced off of objects that one may be looking at. These photons are then absorbed in the eye and the image is flipped upside down in a location called the retina. The image is then left to be interpreted by the occipital lobe. The physiology of the eye is especially complex, but the main exterior parts consist of the sclera and cornea. The sclera can be described as the’whites’ of the eyes. Its main function is to contain the shape of the eye by being stretched and held by tendons. It also offers protection from foreign particles that may enter. Another main attribute to the sclera is that it is connected to the myelin sheath of the optic nerve at the rear of the eye. The cornea is described as a transparent covering at the front of the eyeball. Its primary function is to act as a refractor of light into the lens of the eye. It is unique in that it contains almost no blood vessels and is the sight of oxygen exchange through tears. The cornea can act as a source of protection against foreign particles because of its numerous nerves by triggering the release of tears to flush the particle out. To begin in the interior section of the eye, the first anatomical structure would be the anterior and posterior chambers, which both contain a fluid called the aqueous humor. The anterior chambers can be found between the cornea and the iris, while the posterior chamber is found between the iris and the lens . The aqueous humor that both chambers contain is composed of blood plasma. Normally, the jelly-like fluid is free to travel between the anterior and posterior chambers. One ailment affecting these chambers is a blockage of aqueous passage between the
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Vision, Photoreceptors, and Ocular Disorders 2 chambers. This blockage can can cause blindness by inducing a form of glaucoma. The pressure built up within the eye can interfere with the optic nerve, leading to blindness. The iris and pupil generally go together when describing the makeup of the human eye because they work in conjunction to control the amount of light that is allowed to enter the eye, The iris is a heavily pigmented sphincter muscle that is used to constrict or dilate the pupil. Melanin is the predominant pigment of the eye which, in high concentrations, can contribute to darker eye colors. People with more melanin in their iris usually have brown or hazel coloration and have less sensitivity to bright lights. Behind the iris and pupil is the lens.
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  • Fall '15
  • Mr.Ertl
  • Biology, photoreceptors

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