Human eye-Structure & Functions

Introduction

Human eye Structure & Functions are below, Human eye Not larger than a Ping-Pong ball, It have tens of millions of electrical connections and can handle 1.5 million simultaneous messages.
It gather 80% of all the knowledge a man absorbs. Man thinks of me as a miniature television camera.

Eye structure

The eye is made up of three layers, enclosing various anatomical structures. The outermost layer is fibrous tunic, is composed of the cornea and sclera. The middle layer is the vascular tunic or uvea, consists of the choroid, ciliary body, pigmented epithelium and iris. The inner most layer is retina, the inner layer gets its oxygenation from blood vessels e.g choroid and retinal vessels. The vitreous body is a clear substance composed of water and proteins, which give it a jelly-like and sticky composition.
Human eye have 6 muscles that control its movement and this movement is caused by exerted tensions of these muscles. There are different types of movement of human eye ball.Behind the pupil, there is a transparent structure called a lens.

Eye Functions 

Both are located in the front part of the eye, in front of the lens). The eye receives oxygen through the aqueous. Its function is to nourish the cornea, iris, and lens by carrying nutrients, it removes waste products excreted from the lens, and maintain intraocular pressure and thus maintains the shape of the eye.

The sclera, or white part of the eye, protects the eyeball.The pupil, or black dot at the centre of the eye, is a hole through which light can enter the eye.The iris, or coloured part of the eye, surrounds the pupil.

Light enters the eye through the cornea, the clear, curved layer in front of the iris and pupil. The cornea serves as a protective covering for the front of the eye and also helps focus light on the retina at the back of the eye.

After passing through the cornea, light travels through the pupil.

The iris—the circular, colored area of the eye that surrounds the pupil—controls the amount of light that enters the eye. The iris allows more light into the eye, when the environment is dark and allows less light into the eye, when the environment is bright. Thus, the pupil dilates and constricts like the aperture of a camera lens as the amount of light in the immediate surroundings changes. The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle.

Behind the iris sits the lens. By changing its shape, the lens focuses light onto the retina. Through the action of small muscles, the lens becomes thicker to focus on nearby objects and thinner to focus on distant objects.