Words Worth Knowing- The Structure of the Human Eye

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término		definición
sclera empezar lección		white, opaque, and tough covering of the eye that protects it; nourished by capillaries that supply oxygen to it (red squiggly lines that are visible on the whites of your eyes)
cornea empezar lección		clear and transparent; positioned in front of the pupil and iris and protects them; nourished by aqueous humor and tears produced by lacrimal glands
lacrimal glands empezar lección		located above each eye in the upper lid; secretes fluid (tears) to lubricate and moisten the surface of the eye
iris empezar lección		circular muscles surrounding the pupil; helps regulate amount of light entering the eye; different colors due to lack or concentration of melanin (pigment)
pupil empezar lección		opening in the middle of the eye; regulates amount of light entering the eye with the help of the iris; sensitive to light
ciliary muscles empezar lección		these muscles around the lens hold it in place and change its shape to adjust to focus on objects at different distances
acqueous humor empezar lección		clear, watery fluid behind the cornea; nourishes the cornea and works with it to help focus light
lens empezar lección		colorless; nearly transparent; focuses light rays onto retina; behind iris and pupil; ciliary muscles contract, lens thickens, focus on near objects; muscles relax, lens flattens, focus on far objects
vitreous humor empezar lección		clear, jelly-like fluid; holds internal structure in place; gives shape to the eye ball; fills up posterior chamber
retina empezar lección		thin, innermost layer; sensitive to light; absorbs light entering the eye
choroid empezar lección		second layer between sclera and retina; contains blood vessels to nourish retina
macula empezar lección		concentration of cone cells; processes clear sharp vision; located in the center of the retina
fovea empezar lección		dip in macula; only cone cells; highest sensitivity
optic disk empezar lección		all, white, oval-shaped area on the retina; beginning of the optic nerve
blind spot empezar lección		the optic disk; called the "blind spot" because the area is absent of photoreceptors to images cannot be processed in this area
optic nerve empezar lección		begins at optic disk, located at the back of the eye; carries sensory information from retina's photoreceptors to visual centers of the brain

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