The Eye

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The Eye
Kayla Nix
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The Eye And Its Function
The human eye is a very complex organ. The eye
uses light to allow us to see. Light travels
through the cornea in the front of the eye to the
lens. The cornea and lens help focus what you
are seeing and focuses the light on the retina.
Then the cells in the retina send an impulse to
the brain and then you actually see the image.
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Controlling the Light
The iris and pupil of the eye control how much
light is let into the back of the eye. When the
eye needs to absorb more light the pupil
enlarges. When the eye needs less light the
pupil gets smaller.
The pupil is the black part of the eye.
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Parts of the Eye

• lens
• The transparent crystalline lens of the eye
  is located immediately behind the iris.
• cornea
• The cornea is a transparent dome which
  serves as the outer window of the eye. The cornea
  is the most powerful structure focusing light
  entering the eye.
• retina
• The retina is the innermost layer of the eye. It
  is composed of nerve tissue which senses the
  light entering the eye.
• The retina sends impulses through the optic
  nerve back to the brain, which translates the
  impulses into images that we see.
• There are 4 types of light-sensitive receptors
  found in the retina
• rods
• cones that absorb long-wavelength light (red)
• cones that absorb middle-wavelength light (green)
  
• cones that absorb short-wavelength light (blue)

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Parts of the Eye Part 2

• pupil
• The pupil is the hole in the center of the
  eye where light passes through.
• iris
• The iris is the colored part of the eye. It
  is a thin diaphragm composed mostly of connective
  tissue and smooth muscle fibers. The iris lies
  between the cornea and the crystalline lens.
• optic nerve
• The optic nerve is a continuation of the
  axons of the ganglion cells in the retina. It
  acts acts like a cable connecting the eye with
  the brain.
• The optic nerve is also called the cranial
  nerve II.
• sclera
• The sclera is the white, opaque portion of
  the eye. It provides protection and serves as an
  attachment for the extra-ocular muscles which
  move the eye.

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Diagram of the Eye
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Rods and Cones

• There are close to 120 million rods in the human
  eye.
• The cone of the eye help detect color.
• There are six to seven million cone cells in the
  eye.
• The rod is used at night to allow you to see.

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See you later!