HUMAN EYE

 EYE

Eye is the important sense organ that makes vision possible. It consists of three layers, the outer most layer sclera that provides firmness to the eyeball. The anterior portion of the sclera forms a transparent layer called cornea that allows the light to pass through it. Sclera is covered by conjunctiva except the anterior portion cornea. It keeps the moisture of eye. Middle layer is choroid with number of blood vessels that provide nutrients to eye. The anterior part of choroid forms iris, that regulate amount of light by adjusting the size of pupil. Pupil is an aperture formed in between iris. There is a convex lens located behind the iris that focusses light onto retina. Lens is attached to ciliary muscles from choroid by small ligaments.  Retina is inner most layer consisting of number of photoreceptor cells. Photoreceptor cells mainly concentrated at yellow spot, and spot where there is no photoreceptor cells called blind spot. Optic nerve starts at blind spot which carries impulse from eye to the brain. Other than these parts, there are two chambers an aqueous chamber and vitreous chamber. Aqueous chamber located in between lens and cornea that nourishes eye, and vitreous chamber located in between retina and lens that provide shape to the eyeball.