1. Parts of the Eye
By: Jakob Palmer
Friday, February 1, 2013

2. The Pupil
The pupil is a hole located in the
center of the iris of the eye that
allows light to enter the retina. It
appears black because light rays
entering the pupil are either
absorbed by the tissues inside the
eye directly, or absorbed after
diffuse reflections within the eye
that mostly miss exiting the
narrow pupil.
In humans the pupil is round, but
other species, such as some cats,
have vertical slit pupils, goats have
horizontally oriented pupils, and
some catfish have annular types.
Friday, February 1, 2013

3. The Iris
the Iris is a thin, circular
structure in the eye, responsible
for controlling the size of the
pupils and the the amount of light
reaching the retina.
Eye color is the color of the iris,
which in humans can be green,
blue, brown, and in rarer cases,
hazel, grey, violet, or even pink.
In response to the amount of light
entering the eye, muscles attached
to the iris expand or contract the
aperture at the center of the iris,
known as the pupil. The larger the
pupil, the more light can enter.
Friday, February 1, 2013

4. The Eyelid
An eyelid is a thin fold of skin
that covers and protects the eye. It
has the thinnest skin of the whole
body. The eyelid opens when you
want it to. You can do this if you
want or not. The human eyelid has
a row of eyelashes which serve to
protect the eye from dust and
other debris.
Its key function is to regularly
spread the tears and other liquids
on the eye surface to keep it
moist, since the cornea must
always be moist. They keep the
eyes from drying out when asleep.
Friday, February 1, 2013

5. The Sclera
The sclera also known as the
white of the eye, is the opaque,
fibrous, protective, outer layer
of the eye. In humans the whole
sclera is white, with the colored
iris, but in other mammals the
visible part of the sclera
matches the color of the iris.
In children, it is thinner and
shows some of the underlying
appearing slightly blue. In the
elderly, fatty deposits on the
sclera can make it appear
slightly yellow.
Friday, February 1, 2013

6. The Cornea
The cornea is the transparent front
part of the eye that covers the iris,
pupil, and anterior chamber.
The cornea, with the anterior
chamber and lens, refracts light,
with the cornea accounting for
approximately two thirds of the
eye's total optical power. While the
cornea contributes most of the
eye's focusing power, its focus is
fixed.
The curvature of the lens, on the
other hand, can be adjusted to
tune the focus depending upon the
object's distance.
Friday, February 1, 2013

7. The Lens
The crystalline lens is a
transparent structure in the eye
that, along with the cornea, helps
to refract light to be focused on
the retina.
The lens, by changing shape,
functions to change the focal
distance of the eye so that it can
focus on objects at different
distances, then allowing a sharp
real image of the object of
interest to be formed on the
retina. The lens is more flat on
its anterior side than on its
posterior side.
Friday, February 1, 2013

8. The Retina
The Retina
The retina is a light sensitive
layer at the back of the eye that
covers about 65 percent of its
interior surface. Photosensitive
cells called rods and cones in
the retina convert incident light
energy into signals that are
carried to the brain by the optic
nerve. It is the center of the
eye's sharpest vision and the
location of most color
perception.
Friday, February 1, 2013

9. The Optic Nerve
The optic nerve is the
second of twelve paired
cranial nerves but is
considered to be part of the
central nerves of the eye. As
a consequence, the fibers
are covered with myelin
produced by some part of
the eye rather than Schwann
cells, which are found in
the peripheral nervous
system, and are encased
within the meninges.
Friday, February 1, 2013

10. The Vitreous Humor
The vitreous humor
or vitreous humor
is the clear gel
that fills the space
between the lens
and the retina of
the eyeball of
humans and other
vertebrates.
Friday, February 1, 2013