The eyes

Páginas: 2 (462 palabras) Publicado: 26 de febrero de 2011
The Eye
Eye, organ of vision, the sense of sight can perceive the form, color, size, movements, and distance of objects. The eyes are about the size of a ping pong ball.

Shapes and PropertiesShape: The eye is a spherical shaped structure and is made up of a lens and a three-layered wall, which are the outer sclera, the middle choroid and the inner retina. The eye is shaped like a ball, witha slight bulge at the front. With a diameter about the size of a quarter.
Properties: The eyes are mobile because they can rotate in different directions to focus the eyes and perceive objects.
Eyemovements are divided into:
a) Lateral (abduction and addiction)
b) Vertical (elevation and depression)
c) Rotating (internal and external rotation).

The eyes are located on top ofthe head according the transverse plane. They are to the sides of the median plane or sagittal plane, separated by the nose. They are in the anterior part of the head according the coronal plane.Structure
There are three layers in the anatomy of the eye, which the ophthalmologists call tunics.
The first layer is the cornea and sclera.
The second layer is the vascular tunic, which includesthe iris (which surrounds the pupil), the ciliary body, and the choroid.
The third layer is the retina, which rests on the inside surface of the back of the eyeball.

Process and Function
Process:There are three separate processes that make up the visual process:
• Mechanical: The first part of the visual process is mechanical. Light passes through the cornea and the pupil to the lens.
•Chemical: The second part of the visual process is chemical.
• The photoreceptors receive the light and convert it into electrical signals.
• Electrical processes: The third part of the visualprocess is electrical. Once the photoreceptors convert the light into electrical signals, the nerve cells pick up the signals and carry them to the optic nerve. The optic nerve takes the signals to the...
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