Function & Structure of the Eyes

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  • 0:01 Your Eyes
  • 0:31 Protective Structures
  • 1:17 Anterior Eye
  • 2:00 Tears & Secretions
  • 3:29 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

There are many structures associated with your eyes that protect them from harm and keep them moist. In this lesson, we look at these external and accessory structures, and learn how they help you see the world around you.

Your Eyes

Your eyes convey a lot of emotions. They well up with tears when you're feeling sad, they open wide when you're shocked, and they wink when you're revealing a secret. But your eyes do much more than reveal your emotions; they are actually complex sensory organs that allow you to experience vision. In this lesson, we will describe some of the important external and accessory structures of the eye. The internal structures of the eyeball will be covered in a separate lesson.

Protective Structures

In an adult, the eye measures about one inch in diameter. Much of the eye is found inside the orbit, or eye socket, which is the bony structure that houses the eyeball. This solid structure protects the back of your eye from harm.

The visible part of your eye is protected by the eyelids, which are folds of skin that can close over the eyes. When you wink or blink, it's your eyelids that move. Your eyelashes grow from the edges of your eyelids. The short, curved hairs of your eyelashes may seem like they're just part of a pretty face, but they actually serve a protective purpose. The main function of your eyelashes is to prevent dust and debris from entering the eye.

Anterior Eye

If you look into the eyes of a friend, you notice that her upper and lower eyelids come together on the sides. The place where the eyelids meet is called the inner canthus and the outer canthus. If you ever peeked at someone out of the corner of your eye, your full view was blocked by your outer canthus. The canthi don't have a distinct purpose, but they do provide an anchor point that allows your eyelids to close completely over the eye.

Closing your eyes has some obvious benefits, such as blocking light so you can get a good night's sleep, and preventing bugs from flying into your eyes when you're enjoying the outdoors. A purpose of the eyelids that you might not think of is that they help keep the surface of the eye moist by spreading tears and other natural secretions.

Tears & Secretions

There's a clear, moist membrane that lines the inner surface of your eyelids and the outer surface of the eyeball called the conjunctiva. This delicate membrane secretes mucus, which helps keep your eye moist. Keeping the eye moist is an important job, but because the conjunctiva is a continual membrane, it serves another interesting purpose. The conjunctiva covers the anterior eyeball, and then loops up to cover the inside surface of the eyelids. Because this is a continuous membrane, it prevents eyelashes and your contact lenses from slipping back behind your eyeball.

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