Sight/ origin of sight

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Sense of sight or vision enables us to see our environment. It provides the richest and most detailed source of sensory information. It gives us location and text us what is around us. It also provides three dimensional image of them e.i and colour and motion.

Origin of sight

Each eyes is a spherical or organ known as the eyeball. It is located in a bony socket in the skull. Only a small portion of the front part of the eyes can be seen.
We blink automatically every 2 or 10 seconds.the action spreads tears fluid over the eye surface cleaning and keeping them moist.

Structures of the eye

The outermost sclera: the sclera is a white tough of connective tissue which protects and maintains the shape of the eyeball.
The choroid consist of black pigmented cells and has a rich supply of blood capillaries. the hole in the central of the lris is called the pupil . Light enters the eye through the pupil.
The r e t i n a : retina is the light-sensitive inside layer at the back of the eyeball. It gets its nourishment from the capillaries and choroid .

In the human eyes, each retina contains about 125 million rods and 7 millions cones.note: other animals gross like the arthropods and mollusca too have eyes.
Their eyes and mammalian eyes are different as day involved along different line of common ancestry .

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