Sight and the eye. Structure of the eye and blood and nerve supply to the eye.

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Anatomy of the eye.
The eye is the organ of sight. It is situated in the orbital cavity and is supplied by the optic nerve . It is almost spherical in shape and about 2.5 cm in diameter. The space between the eye and orbital cavity is occupied by adipose tissue . The bony walls of the orbit and the fat protects the eye from injury.
STRUCTURE- There are three layer of tissue in the walls of the eye:-
• The outer fibrous layer :sclera and cornea
• The middle vascular layer or uveal tract:consisting of the choroid,ciliary body and iris
• The inner nervous tissue layer :the retina
SCLERA AND CORNEA:- The sclera ,or white of the eye ,forms the outermost layer of the posterior and lateral aspects of the eyeball and is continous anteriorly with the cornea.
CHOROID:- The choroid lines the posterior five-sixth of the inner surface of the sclera and it is rich in blood vessels and it absorbs light which enters in the eye through the pupil.
Ciliary body:The ciliary body is the anterior continuation of the choroid consisting of the ciliary muscle and secretory epithelial cells.
Iris: The iris is the visible coloured ring at the front of the eye and extends anteriorly from the ciliary body,lying behind the cornea and in front of the lens.
Lens: The lens is a highly elastic circular biconvex body,lying immediately behind the pupil .
RETINA:- The retina is the innermost lining of the eye. It is extremely delicate structure and well adapted for stimulation by light rays.
BLOOD SUPPLY TO THE EYE:- The eye is supplied with arterial blood by the ciliary arteries and the central retinal artery. These are branches of ophthalmic artery.
Venous drainage is by a number of veins ,including the central retinal vein.
NERVE SUPPLY TO THE EYE:- The eye is supplied by the optic nerve ,which is the second cranial nerve.

Sushila choudhary
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