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Question : Describe the different parts of human eyes.

Answer»

Solution :(1) Eyeball is sphericaland has three layers.
(2) Sclera isthe outerlayer ofdenseconnectivetissue.Its transparentanteriorportionistermed as a cornea.
(3) Choroidis the middler layer. The posteriortwo third REGION of this layeris thin, while the anteriorregion is thickwhich formsthe ciliarybody.
(4) Iris is the forward segmentof the ciliary body which is pigmented andopaque.
(5) Lens is a transparentcrystalline structure.It is presentanteriorlyinside the iris andis heldin positionby the ligaments ofciliarybody.
(6) The aperturesurroundedby the iris in fontof thelends is known as pupil.
(7) The INNERMOST layer of the eye is the RETINA which consists of three sub-layers FORMED by ganglion cells, bipolar cells and photoreceptor cells, which are sensitive to light.
(8) There are two types of photoreceptor cells viz. road and cones containing photogments, rhodopsin which is a derivative of vitamin A (in roads) and iodopsin (in cones).
(9) The cones are responsiblefor daylightor photopic visionand colourvision.The rods functionin dim light givingscotopic vision.
(10) The opticnerveleavesthe eye at a point slightlyaway fromthe medianposteriorpole of theeyeball . In thisregion, the rods andconesare absentthereforethis regionis knownas blindspot.Maculalutea, a yellowishpigmentedspot ispresent lateral to theblindspot.Forvea is a centralpit presentbeside it.
(11)A spacebetween thecorneaand the lensis calledaqueous chamber, containingaqueoushumor.
(12) Vitreouschamberis the largerspacebetween thelens andthe retinawhichisfilled with vitreous homor.


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