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Uploaded:2015-05-21
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Ever have a staring contest? Why is it so hard?! Jessi answers a question from a curious SciShow Kids viewer: Why do we blink?

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SOURCES:
https://www.highlightskids.com/science-questions/why-do-we-blink
http://kidshealth.org/kid/talk/qa/eyes_water.html?tracking=K_RelatedArticle
https://faculty.washington.edu/chudler/chreflex.html
One, two, three, go!  

Oh, darn it! Okay Squeaks, you win again. Squeaks and I were just having a staring contest and I keep losing because after a few seconds, no matter how hard I try, I just have to blink!

(Squeaks) Good question Squeaks! Why do we blink?

Well, the short answer is we blink because... we have to! Blinking is a reflex, and reflexes are things that our bodies do automatically, that is we don't have to think about doing them, our bodies just do them.

Maybe you've been to the doctor's office, and they've hit the spot right below your kneecap with a little rubber mallet. What happens? Your lower leg kicks slightly, and you can't control it! That's an example of a reflex. 

Breathing is a reflex too! We breathe all day and night without even thinking about it! And while you can hold your breath for a little bit, eventually you have to breathe.

And the same goes for blinking! Without actually having to think about it, your brain sends a signal to your eyes to tell them to blink about twenty to twenty five times per minute. And although you can stop it for a while, like during our staring contest, eventually you always end up blinking again.

And the same is true if something comes at your face when you're not expecting it. Like if someone tosses a ball to you when you're not quite ready yet. Your brain will tell your eyes to close. This reflex is important because your eyelids help to protect your eyes, which are very delicate, and very important.

If you've ever been outside on a windy day, you've probably noticed that you can't help squinting and blinking. Your body uses the blinking reflex to help keep all of the dust and dirt that's flying around in the wind out of your eyes. 

And you might also notice that your eyes water. When your eyes water, those are tears. Our eyes don't just make tears when we cry, tears also play a role in protecting our eyes when we blink. Our eyes are always wet, and they look shiny. That's because they're covered with a very thin watery layer that's made mostly of tears. This watery layer helps wash away little bits of dust and other particles that can irritate our eyes. 

Tears keep that layer and other parts of our eyes from drying out so they stay healthy, and those tears come from lacrimal glands which are just above the eye and below the eyebrow. 

But tears aren't just made of water. You might already know that tears taste salty and they do contain salt, but they also contain other special substances that can help kill bacteria and viruses, which are things that can make you sick if they entered your body. 

When you blink, the movement of your eyelids acts like a windshield wiper, spreading the tears made by the lacrimal glands over the surface of your eye. The tears wash away dirt and germs, and then leave your eyes through tiny holes in the corner of your eye closest to your nose. These holes act like little drains and they lead right into your nose and empty into your throat. 

So blinking is a reflex. Something we don't specifically have to think about doing but something we have to do to protect our eyes and help keep them healthy. So blinking is awesome! What do you say Squeaks, we should have a blinking contest instead. Thanks guys! See you next time on SciShow Kids!