{"id":1787,"date":"2020-07-12T15:49:49","date_gmt":"2020-07-12T15:49:49","guid":{"rendered":"https:\/\/murreeroad.org\/Biology10\/?p=1787"},"modified":"2020-07-12T15:49:49","modified_gmt":"2020-07-12T15:49:49","slug":"q-8-describe-structure-and-mechanism-of-function-of-human-eye","status":"publish","type":"post","link":"https:\/\/murreeroad.org\/Biology10\/q-8-describe-structure-and-mechanism-of-function-of-human-eye\/","title":{"rendered":"Q.8 Describe structure and mechanism of function of human eye."},"content":{"rendered":"

Q.8\u00a0Describe structure and mechanism of function of human eye.<\/strong>
\nAnswer:<\/strong>
\nHuman Eye<\/strong>
\nLocation<\/strong>
\nOur eyes are located in small portions of skull known as the orbits or eye sockets.
\nExternal Structure of Eye<\/strong>
\n(i) Eyelids <\/strong>
\nFunctions<\/strong>
\nEyelids wipe eyes and prevent dehydration. They spread tears on eyes which contain substances for fighting bacterial infections.
\n(ii) Eyelashes<\/strong>
\nFunction<\/strong>
\nEyelashes prevent fine particles from entering eye.
\nInternal structure of eye<\/strong>
\nThe internal structure of eye can be divided into three main layers;
\n(i) Outer layer<\/strong>
\nThe outer layer of eyeball consists of sclera and cornea.
\n(a) Sclera<\/strong>
\nIt consists of dense connective tissue.
\nFunctions<\/strong>
\nSclera gives eye most of its white colour, It protects the inner components of eye.
\nIt maintains the shape of eye.
\n(b) Cornea<\/strong>
\nIn the front, sclera forms the transparent cornea.
\nFunction<\/strong>
\nCornea admits light to the interior of eye and bends light rays so that they can be brought to a focus. (ii) Middle Layer Choroid<\/strong>
\nThe middle layer is called choroid.
\nStructure<\/strong>
\nIt contains blood vessels.
\nFunction<\/strong>
\nIt gives the inner eye a dark colour. The dark colour prevents disruptive reflections – within eye.
\nIRIS<\/strong>
\nBehind cornea, choroid bends to form a muscular ring called iris.
\n\"eye\"
\nPupil <\/strong>
\nThere is a round hole, called pupil, in the centre of iris. After striking the cornea, light passes through the pupil.
\nSize <\/strong>
\nThe size of pupil is adjusted by the muscles of iris.
\nFunction <\/strong>
\nPupil constricts in bright light when the circular muscles of iris contract Pupil dilates in dim light when the radial muscles of iris contract.
\n\"eye1\"
\nLens <\/strong>
\nBehind iris, there is a convex lens.
\nFunction <\/strong>
\nIt focuses light on the retina.
\nCiliary muscles and Suspensory Ligaments
\nLens is attached to ciliary muscles of eye via\/through a ring of suspensory ligament.
\nFunction <\/strong>
\nTo see an object far clearly that is away, ciliary muscles are relaxed and lens becomes less convex. When ciliary muscles contract, lens becomes more convex and round.
\n(iii)INNER LAYER-RETINA <\/strong>
\nThe inner layer is sensory and is called retina. It contains the photosensitive cells called rods and cones and associated neurons.
\nRods <\/strong>
\nThese are sensitive to dim light.
\nCones <\/strong>
\nThese are sensitive to bright light and they distinguish different colours.
\nPoints on Retina
\nRetina has two points, fovea and optic disc.
\nFovea <\/strong>
\nFovea is a dip in retina directly opposite to lens and is densely packed with cone cells.
\nFunction
\nIt is largely responsible for colour vision and sharpness.
\nOPTIC DISC <\/strong>
\nOptic disc is a point on retina where the optic nerve enters retina.
\nBlind spot <\/strong>
\nThere are no rods and cones at this point, that is why it is also referred to as the blind spot. Chambers <\/strong>
\nThe iris divides the cavity of eye into two chambers.
\nAnterior chamber <\/strong>
\nThe anterior chamber is in front of iris i.e. between cornea and iris.
\nAqueous humour<\/strong>
\nThe anterior chamber contains a clear fluid known as aqueous humour.
\nPosterior chamber <\/strong>
\nThe posterior chamber is between iris and retina.
\nVITREOUS HUMOUR <\/strong>
\nThe posterior chamber contains a jelly – like fluid known as vitreous humour.
\nFunction <\/strong>
\nIt helps to maintain the shape of eye and suspends the delicate lens.
\nMECHANISM OF VISION <\/strong>
\nLight from objects enters eye and is refracted when it passes through cornea, aqueous humour, lens and vitreous humour. Lens also focuses light on retina. As a result, the image falls on retina. Rods and cones generate nerve impulses in the optic nerve. These impulses are carried to the brain, which makes the sensation of the vision.<\/p>\n

\"\"<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Q.8\u00a0Describe structure and mechanism of function of human eye. Answer: Human Eye Location Our eyes are located in small portions of skull known as the orbits or eye sockets. External Structure of Eye (i) Eyelids Functions Eyelids wipe eyes and prevent dehydration. They spread tears on eyes which contain substances for fighting bacterial infections. (ii)… Read More »Q.8 Describe structure and mechanism of function of human eye.<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[23],"tags":[],"_links":{"self":[{"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/posts\/1787"}],"collection":[{"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/comments?post=1787"}],"version-history":[{"count":1,"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/posts\/1787\/revisions"}],"predecessor-version":[{"id":1790,"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/posts\/1787\/revisions\/1790"}],"wp:attachment":[{"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/media?parent=1787"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/categories?post=1787"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/murreeroad.org\/Biology10\/wp-json\/wp\/v2\/tags?post=1787"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}