Youtor
Structure of Human Eye Photoreceptor Biology lecture
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=tOzl2gquJHw
Eye Anatomy and the Parts of the Eye • What are the Parts of the Eye and what are their functions? • The eye is arguably one of the most complicated organs in our body. • It is unique in its ability to transmit light rays and images through the pupil, focus the image clearly through the vitreous humor and onto the retina and finally converting it into electrical signals that are carried to the brain via the optic nerve. • But what are the basic parts of the eye that provide this ability? • Let's find out. • The Cornea • The clear bulging surface in front of the eye is the cornea. The cornea helps us see in a number of ways, including: • Being the primary refractive surface of the eye. • Being the the eye's primary defense against foreign debris and irritants. Tears also help the cornea maintain its. • hydration • anti-bacterial integrity • water content • and extensive oxygen exchange. • The IRIS • The iris is the pigmented color portion of the eye. The iris's abilities include. • a sphincter muscle that controls the amount of light allowed into the eye through contraction and dilation. Similar to a camera aperture. • The Pupil • The pupil is a hole approximately 3 to 7 millimeters in diameter through which light passes. • The Natural Lens • The eye's natural lens has the ability to change shape as one focuses on near or distant objects. • As one ages the the lens becomes less flexible, leading to presbyopia. • This condition is the reason why people look to use bifocal glasses or reading glasses. • The Vitreous • This is the clear gelatinous substance that fills the space between the lens and retina. This fluid helps to maintain the eye's shape. • The Retina • The retina is a layer of tissue at the back of the eyeball, acting like the film of a camera for the eye. • It contains cells that are sensitive to light, both black and white as well as colored. It converts these light stimuli into electrical nerve impulses, and sends them to the optic nerve. • The Optic Nerve • The optic nerve is bundled at the back surface of the eye. There are no photoreceptor at the anatomical location of the optic disk therefore creating a blind spot. Electrical nerve impulses travel along the optic nerve, and onward to the brain. • The Entire Eye • With a better understanding of the eye and its structures one can appreciate its true complexity. Taking sight for granted is easy to do. However, it is easy to see and appreciate the true complexity of the eye. • http://www.blog.contactlensking.com/e... • http://www.blog.contactlensking.com
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