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Parts of the Eye and their Functions

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  • 0:01 What Is the Eye?
  • 0:20 The Front of the Eye
  • 1:52 The Back of the Eye
  • 3:36 Lesson Summary
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Lesson Transcript
Instructor: Brekke Peterson Munks
Do you know the parts of the eye? If not, this lesson will help you to identify the parts of the eye and understand their specific functions. After learning about the eye, you will be able to test your knowledge with a quiz.

What is the Eye?

Is the eye a round, liquid-filled sphere that allows us to see? Well, essentially yes, but it is much more complicated than that. There are many parts that must work together to allow mammals to see. There are two regions of the eye: the front and the back. We'll discuss the front of the eye first.

The Front of the Eye

The front part of the eye is what you see if you stand in front of a mirror. It consists of the:

  • Iris
  • Pupil
  • Cornea
  • Sclera
  • Conjunctiva

What you see when you look in the mirror.
eye iris

The iris is the colored part of the eye. It is important because it controls the size of the pupil. The pupil is the dark circle inside the center of the eye. The dark hole is altered in shape by the iris, affecting the amount of light that is let into the eye. The pupil is large when light is low or it is dark outside and tiny when it is very sunny or bright.

The cornea is the clear covering over the pupil and iris. This is the reason that contacts are dome shaped because they sit on the cornea. The cornea provides 66% of the optic power that the overall eye has. This means that the cornea is very important in focusing what we see by bending light.

The sclera is the white part of the eye that we see in the mirror that becomes pink or red when we are tired or have sneezed so hard that our eyes become bloodshot. This eye part is the protective, outer layer of the eye. It is made up of elastic-like fibers called elastin and collagen, a common connective tissue found in mammals.

The eyeball is held in place by the eyelid, which is the first protective layer. The eyelid has an inner layer of skin called conjunctiva. The conjunctiva covers the sclera and provides mucus and tears for eye lubrication and bacterial infection prevention. It does not cover the cornea.

Eye anatomy

The Back of the Eye

In the back of the eye, are the important items that we cannot see when we look in the mirror. This area consists of the:

  • Lens
  • Vitreous
  • Retina
  • Macula
  • Fovea
  • Optic nerve

These parts have important independent functions. The lens of the eye works in conjunction with the cornea. This part is also important for light refraction and focusing of images onto the retina. The lens can change shape to fine tune focus, change focal distance, and create a sharp image.

The vitreous is the clear, thick gel-like substance between the lens and retina. The function of the vitreous gel is to help with optical power, maintain eye structure and retinal health. It is very clear, 98% water, and doesn't change from birth, unlike many fluids in the body that are replenished throughout life.

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