Human Eye

Human Eye

1. STRUCTURE & FUNCTION OF THE EYE Prepared by Mr. Vinayak Raju Bodhankar M. Pharm. (QA)

2. Human Eye The human eye is an organ for sight . Situated in the orbital cavity supplied by the optic nerve . Spherical in shape & 2.5 cm in diameter. Structurally 2 eyes are separate but, some of their activities are coordinated, so they function as pair THE HUMAN EYE

3. STRUCTURE There are 3 layers of tissue in the wall of eye Outer fibrous layer: Sclera & cornea Middle vascular layer: Choroid, ciliary body & iris Inner nervous tissue layer: Retina

4. PARTS OF HUMAN EYE The front part of the Eye includes: Iris: the colored part. Cornea: a clear dome over the iris. Pupil: the black circular opening in the iris that lets light in. Sclera: the white of your eye.

5. SCLERA & C O RNE A CORNEA T ransparent covering of the front of the eye . Allows for the passage of light into the eye and functions as a fixed lens. Function: Allows for the passage of light into the eye and it also focuses the light on retina . SCLERA A tough white skin (made of tissue) that covers all of the eyeball except the cornea. Function: Supports eyeball and provides attachment for muscles .

6. I r i s , Choroid & Ciliary body IRIS Colored part of eye . Lying behind the cornea in front of lens. It is a circular body composed of pigment cells & two layers of smooth muscle fibres. Controls the amount of light entering the eye. CHOROID Lines the inner surface of sclera. Rich in blood vessel & is deep chocolate brown in colour. Light enters the eye through pupil, stimulate the nerve endings in retina & then absorbed by choroid. CILIARY BODY It is the anterior continuation of the choroid. Consist of ciliary muscle & secretory epithelial cells. Contraction & relaxation of ciliary muscle changes the thickness of the lens.

7. R eti na In nermost layer of the wall of the eye. Layer is highly sensitive to the light. Contains light-receptive cells (rods and cones) Converts light to electrical signals

8. P u pil (black hole) B lack hole in iris where light enters . Function: Pupil size is controlled by iris muscles . Pupil Expansion When the eye needs more light to enter (when it is dark), the pupils get larger ; allowing more light to enter the eye . Pupil Contraction When the eye needs less light to enter (when it is very bright), the pupils get smaller ; allowing less light to enter the eye.

9. Optic Nerve Transmits electrical impulses from retina to the brain . Creates blind spot . Brain takes inverted image and flips it so we can see . Function: Transmits electrical signals from retina to the brain .

10. F u n c t i o n s The eye has many parts that must work together to produce clear vision: The sclera, or white part of the eye, protects the eyeball. The pupil, or black dot at the center of the eye, is a hole through which light can enter the eye. The iris, or colored part of the eye, surrounds the pupil.