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