Eye - Evolution Of The Eye, Anatomy And Function Of The Human Eye, Retina, Optic Nerve
light brain images lens
The eye is the organ of sight in humans and animals which transforms light waves into visual images and provides 80% of all information received by the human brain. These remarkable organs are almost spherical in shape and are housed in the orbital sockets in the skull. Sight begins when light waves enter the eye through the cornea (the transparent layer at the front of the eye) pass through the pupil (the opening in the center of the iris, the colored portion of the eye) then through a clear lens behind the iris. The lens focuses light onto the retina which functions like the film in a camera. Photoreceptor neurons in retinas, called rods and cones, convert light energy into electrical impulses, which are then carried to the brain via the optic nerves. At the visual cortex in the occipital lobe of the cerebrum of brain, the electrical impulses are interpreted as images.
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The human eyeball is about 0.9 in (24 mm) in diameter and is not perfectly round, being slightly flattened in the front and back. The eye consists of three layers: the outer fibrous or sclera, the middle uveal or choroid layer, and the inner nervous layer or retina. Internally the eye is divided into two cavities—the anterior cavity filled with the watery aqueous fluid, and the posterior ca…
The retina is the innermost layer of the eye. The retina is thin, delicate, extremely complex sensory tissue composed of layers of light sensitive nerve cells. The retina begins at the ciliary body and encircles the entire posterior portion of the eye. Photoreceptor cells in the rods and cones, convert light first to chemical energy and then electrical energy. Rods function in dim light, allowing …
The optic nerve connects the eye to the brain. These fibers of the optic nerve run from the surface of the retina and converge at exit at the optic disc (or blind spot), an area about 0.06 in (1.5 mm) in diameter located at the lower posterior portion of the retina. The fibers of this nerve carry electrical impulses from the retina to the visual cortex in the occipital lobe of the cerebrum. If the…
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