Human Body : Eyes


The human eye is the organ which enables us to see. The eyes are two in number and each is placed inside specialised compartments or sockets in the skull.

The white part of our eyes is known as sclera. It consists of fibrous tissues. The job of this part it to protect the internal parts of the eye.

The transparent tissue through which light enters the eyes is called cornea. It exists in front of the eye.

The iris is made up of muscles which contract or relax in order to adjust the amount of light which enters the eye.

The pupil is an aperture controlled by the iris muscles; when it is dark, the iris muscles relax, causing the pupil to open up wider so that more light enters the eyes to enable us to see better. Conversely, the pupil becomes narrow due to the contraction of the iris muscles when there is excessive light in order to protect the cells of the eyes.

The lens is present behind the pupil. Light enters the pupil, passes through the lens and is focused on the retina of the eye. The lens is capable of changing its shape in order to help us see near or far off objects.

The retina converts light into electrical signals which are transferred to the brain for processing. The retina contains two types of cells: rods and cones. These cells are sensitive to light. Rods are important for night-time vision when there is little light; cones play an important role in helping us see colours.

The optic nerve takes electrical signals from the retina of the eye to the brain.

The human eye does not only let us view the scenes and phenomena in our surroundings, but also enables us to differentiate between colours, though sometimes, there is a minor defect in the eye function and the individual cannot make difference between the red and green colour.

Find out much more about the eyes here…

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