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Eye diagram

Answer» Eye:\xa0Eye is a hollow spherical structure composed of three coats:– Outer fibrous coat– Middle vascular coat– Inner nervous coat(i) Fibrous coat: It is thick and protects the eyeball. It has two distinct regions – sclera and cornea. Sclera covers most of the eye ball. The sclera or white of the eye contains many collagen fibres. Cornea is a transparent portion that forms the anterior one – sixth of the eyeball. The cornea is avascular (i.e., lacks blood supply).(ii)Vascular coat: It comprises of 3 regions : choroid, iris, ciliary body.(a) Choroid : It lies adjacent to sclera and contains numerous blood vessels and pigmented cells.(b) Iris: The iris is a circular muscular diaphragm containing the pigment giving eye its colour. It extends from the ciliary\xa0body across the eyeball in front of the lens. It 2. has an opening in the centre called the pupil.It contains two types of smooth muscles, circular muscles (sphincters) and radial muscles (dilators), of ectodermal origin.(c) Ciliary body: Behind the peripheral margin of the iris, the vascular coat is thickened to form the ciliary body. It is composed of the ciliary muscles and the ciliary processes.(iii) Nervous coat: It consists of retina which is neural and sensory layer of an eye ball.\xa0It consists of three layers; ganglion cells, bipolar cells and photoreceptor cells (rods and cones).Lens: It is a transparent, biconvex, elastic structure that bends light waves as they pass through its surface. It is composed of epithelial cells that have large amounts of clear cytoplasm in the form of fibres.Chambers of eyeball: The lens, suspensory ligament and ciliary body divide the eye into an anterior aqueous chamber and a posterior vitreous chamber which are filled with aqueous humour and vitreous humour respectively.


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