| The entire eye, often called the eyeball, is a
sensory organ which allows vision. They eye is a round
structure approximately 2.5 centimeters long. It is
located in the front of the scull in a bony cavity called
the orbit. The skull gives the eye some protection from
physical injury. They eye is held in place by a series of
muscles that also allows the eye to move around and
expand the field of vision. The white part of the eye is
called the sclera. It helps protect the optic nerve, at
the back of the eye from too much light and it helps the
eye to hold it's shape. The iris is the part of the eye
that is colored. The iris is around the pupil which is
the dark center of the eye. The pupil's job it to open
and close to let in light. You can test this on a friend
by turning off the light and flashing a penlight at your
friends eye. The pupil will be bigger in the dark and
smaller when you turn the light back on. This also helps
control how much light goes into the eye. The lens of the
eye sits right behind the pupil. It is the lens that
focuses the image that we see into the retina. The retina
then turns the image upside down and the brain
"reads" what we see. The lens is also what can
change shape and cause some people to wear glasses or
contact lenses in order to have normal vision again. |
