Describes the general anatomy of the human (vertebrate) eye. Since the sound is very low, I have typed out the text ... First, we need to get our bearings straight. The terms inner and outer are used to describe the relative positions of different structures of the eye. This can be somewhat confusing. One might think that outer means closer to the body’s surface - the lens for example - and that inner means closer to the body’s center - the optic nerve for example. This is not so. The terms inner and outer are relative to the center of the spherical eyeball. Similar to their meanings when dealing with the spherical Earth, inner refers to something that is closer to the center - center of the sphere - and outer means something that is farther away from the center, closer to the edges. Sclera. The sclera is the outermost layer of the eyeball: the fibrous tunic. The sclera is the white part of the eye and is where the muscles that move the eye attach. At the front of the eye, the sclera becomes the transparent cornea. Choroid. The choroid is the middle layer of the eyeball: the vascular tunic. At the front of the eye, the choroid becomes the colored, donut-shaped iris, as well as the ciliary body. Retina. The retina is the innermost layer of the eyeball: the neural tunic. The neural layer of the retina contains the photoreceptors - both rods and cones - that detect light, as well as having the neurons that the photoreceptors stimulate in order to send signals to the brain. The pigmented layer of the retina also absorbs light, to prevent visual echoes. In addition, it recycles retinal from the photoreceptors in the neural layer. Fovea. The fovea is a small, circular depression in the retina (close to the optic disc) where cones are highly concentrated. The fovea, the center of the field of vision where light is focused by the lens, contains only cones, which detect different colors of light: rods do not. Optic nerve. The optic nerve contains all the retinal ganglion cells’ axons and runs from the optic disc at the back of the eye to the brain. Central artery and vein. The central artery and vein, whose path runs through the center of the optic nerve, supply and drain the retina respectively. Optic disc. The optic disc is the origin of the optic nerve. It is the point where all of the retinal ganglion cells’ axons exit the eye on route to the brain. Since the optic disc is devoid of photoreceptors, any light striking it cannot be detected. Hence, it is called the blind spot. Lens. The lens is the transparent disc that helps focus light onto the retina. The cells of the lens have ejected their nuclei and other organelles and are filled primarily with proteins called crystallins. The lens is held in place by the suspensory ligament. In mammals, the lens can change shape to adjust focusing for far away and nearby objects. However, in fish, the lens does not change shape but instead moves forward and backward to assist in focusing. Pupil. The pupil is the hole in the center of the iris. When the iris changes shape, the pupil is either dilated - allowing more light in - or constricted - allowing less light in. Iris. The iris is the colored – blue, brown, hazel, etc. – donut-shaped portion of the choroid just in front of the lens. If more or less light needs to enter the eye, dilator of constrictor muscles, respectively, within the iris contract to change the iris’s shape. Cornea. The cornea, located at the front of the eye, is the transparent portion of the sclera. Light passes through it before reaching the lens. The cornea acts as a fixed lens: unlike the lens itself, the cornea’s shape cannot be altered in order to focus the light or image. Suspensory ligaments. The suspensory ligaments attach the lens to the ciliary body, anchoring the lens and positioning it appropriately. Ciliary body. The suspensory ligaments that hold the lens in place attach to the ciliary body. In addition, the ciliary body functions to produce the aqueous humor. Aqueous humor. The aqueous humor is the clear, watery fluid that fills the anterior cavity, just in front of the lens. The aqueous humor, which circulates through the anterior cavity, provides fluid pressure that helps maintain the eye’s shape. Vitreous humor. The vitreous humor is the jelly-like substance that fills the posterior cavity, behind the lens. The pressure exerted by the vitreous humor helps maintain the shape of the eye, as well as keep the neural layer of the retina pressed against the pigmented layer of the retina.
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This video gives 5 reasons, the last one being undeniably compelling, why honest people should accept that Richard Dawkins was not -- NOT --- stumped by the Creationists' question asking him for a process that can add information to genomes.
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The ICR (Institue of Creationist Retards) recently published an article making incorrect claims about science, horribly mistating science, and pulling a "scientific" conclusion out of their backside orifice. Isn't it cute when Creationists pretend to do science? ROTFLMAO! The music is Maynard Ferguson's "Awright, Awright", off his album "M.F. Horn 3."
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Some of my favorite atheist and atheist-related quotes. The music is Maynard Ferguson's band playing the appropriately titled "Got the Spirit" from the album "Live at Jimmy's: MF Horn 4&5". Maynard is the trumpet soloist: I believe the sax soloist is Bruce Johnstone, but it may be him (baritone) and Ferdinand Povel (tenor) as different places.
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Addresses what has to be one of the most scientifically flawed videos about the origin of life on the Internet (Origin of Life made Difficult). In particular, its references to eukaryotic cells and mitosis.
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Addresses problems with what has to be one of the most scientifically flawed videos about the origin of life on the Internet (Origin of Life made Difficult). In particular, RNA replication, DNA-or-protein conundrum, and the fact that the Earth is billions of years old
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I present a group of features of manatees, and a couple of fossils, that together make manatee origins probably one of the best single examples of macroevolution known. References for the images I used did not show up well in the video, so someone requested I add them here. Toenails on Flippers: http://www.locolobo.org/SirenianEvolution.html Tetrapod Limb Skeleton in Flipper: http://www.theoceanadventure.com/FMIE/media/skeleton.jpg Rudimentary Pelvic Bone, Vestigial Hip Sockets, & Characteristic Features of Modern Manatees David M. Kingsley, Ph.D., Lecture 3: Fossils, Genes, and Embryos" from the free DVD Evolution: Constant Change and Common Threads, Howard Hughes Medical Institute, 2006 Fossil with 4 Legs and Full-Size Hindlimbs http://www.talkorigins.org/faqs/comdesc/images/legged_seacow.jpg Fossil with 4 Legs, but Reduced-Size Hindlimbs http://www.locolobo.org/SirenSkels.jpg
Views: 11360 DNAunion