Eyes The One-Way Windows of the Face For sighted people, the eyes are one of the most important organs of the human body. These slimy Ping-Pong balls are largely responsible for helping you understand and interpret the world around you--using more than two million moving parts and eye muscles that move more than a hundred thousand times a day! And thanks to your eyes, you have the ability to appreciate the colors of a rainbow, enjoy a smile from someone you love, or even watch out for dog poop on the sidewalk before you step in it. Your eyes are literally always looking out for you. Thanks, eyes! How in the World Do Eyes Work?! Have you ever noticed how difficult it is to see in the dark? Of course you have! But do you know why? (Uhh . . .) We'll tell you! It's because our eyes are powered by light. When we look at an object, light reflects or bounces off that object and enters the eye. Once that light works its way to the retina in the back of your eye, the retina turns it into signals that your brain can understand. Putting the EYE in TEAM Let's meet the different parts of the eye and learn a little bit about how they all work together to help you see! Hey all! Iris here. I'm the beautiful colored part of your eye, and believe it or not, I am basically all muscle! I'm also a total control freak! It's my very important job to pick and choose the exact amount of light that's allowed to enter the lens through ol' Pupil. It's easy--I just grow and shrink, and light bends to my will. And not to toot my own horn (okay, I'm totally tootin' here!), but it's because of me that you can see in different amounts of light! If it's sunny outside, I grow extra big and put the brakes on the amount of light I allow in. And when you go to the bathroom in the middle of the night, I get real small, opening the gates up wide to let whatever light is out there come in. In other words, eye am super loyal and there for you day or night! Um . . . hello, my name is Cornea and I am here to protect and serve. You probably don't even notice I'm here. I'm just a thick, clear, protective layer guarding your eye from all the junk that tries to get in there. If you protect me by not sticking garbage in your eye, you can rest assured that I will always protect you. And by you, I mean your eyeball, and that's pretty much it. Hi, hi! Pupil here! Some people call me "PeeOOP" and some call me "Poopil," but I prefer to be called by my given name, Pupil. I am that little black dot in the middle of your eye. Can you even imagine what your eye would look like without me?! Try it right now--IMAGINE IT! NOW STOP IMAGINING IT! Creepy, right? My job is to let the light in to hit the back part of your eye, called Retina. (Shout-out to Retinaaaal) Retina and I work together like a projector and a movie screen. Like a projector, the light that comes through me is focused by Lens (you'll meet Lens next), and then it's projected onto Retina just like a movie screen! Okay, Lens, you're up! Hello, my name is Lens, and like Pupil said, it's my job to keep things focused. And by "things," I mean light. I sit back here behind Iris, WHO DOESN'T EVEN KNOW I EXIST BECAUSE I'M SO CLEAR AND COLORLESS, and focus light rays on the back of your eyeball, AKA (also known as) Retina. Retina, take it away! They call me Retina, because that's what I am. For me, every day is Opposite Day, and here's why: Because your eyeball is curved, whatever you look at hits me upside down. Even so, I take this information and send it to your brain via Optic Nerve. Thankfully, your brain has the power to flip it around and make it right-side up again. Hey, Optic Nerve! Introduce yourself! Nice to meet you! My name is Optic Nerve and I pretty much just hang out here at the back of your eye and send info on what you see to your brain. No biggie, I'm just the messenger. Except, of course, YOU WOULD NEVER BE ABLE TO SEE WITHOUT ME! BOOGERS They're Not Just for Noses! Eye boogers are those sticky, crusty little bits of oil, mucus, ooze, and dead skin cells that clump up in the inner corners of your eyes and gross you out in the mirror. While you're awake, you're blinking them away before they're even able to set up shop. But during your blinkless sleep, they settle in, waiting to greet you in the morning! What in the Wow? The word "pupil" means "little person." Could this be because tiny versions of ourselves are reflected in other people's pupils?! Due to our lack of thick fur everywhere, our furry eyebrows are much more noticeable than other animals'. But just imagine if your family pet had eyebrows as bushy as yours. A fish with eyebrows?! No laughing!! There are about 250 hairs in a human eyebrow, but grownups who have never plucked them could have more than one thousand hairs! Eyelids (AKA eyelash holders) are the official blinkers of the human face. They not only help to keep our eyeballs slimy with mucus and oils--and help to refocus our eyes when we blink--but they also work like tiny windshield wipers to clear away all the dust and other microscopic junk that shouldn't be there. WOW DON'T YOU . . . ? BLINK! BLANK! BLINK! BLANK! Set your timer for one minute and count how many times you blink naturally in that time. Chances are you'll count somewhere between fifteen and twenty blinks. Do you feel like you missed anything in each tenth of a second that your eyes were closed? Probably not. But why? Turns out our brains have the amazing ability to automatically stitch together what we see between blinks, essentially filling in the blanks! A Blink of an Eye Newborn babies are the world champions when it comes to the art of staring competitions. Some babies blink as little as ONCE a minute! Grownups, on the other hand, can hardly keep their eyes open, clocking in at a whopping average of fifteen blinks a minute. Wow-to Experiment: Host a staring-contest smackdown between a newborn baby and a grownup. Set a clock for one minute and count the blinks between the two opponents. Do you have what it takes to challenge the winner? Fact Snacks While your nose and ears continue to grow, grow, grow throughout your lifetime, the eyes that you were born with stay the same: about the size of a Ping-Pong ball! (Okay, fine. They grow a few measly millimeters in the first two years of your life, but after that, they pretty much stay the same.) People with blue eyes all share a common ancestor! Some people have two or even three rows of eyelashes! Actress Elizabeth Taylor was one of these people. People with heterochromia have two different colored eyes or eyes that have more than one color. Just another reason to always look people in the irises! When you get snotty while crying, it's a result of tears draining into the back of your nose and mixing with snot. Because of blinking, our eyes are closed for about 10 percent of the time we're awake! As many as 20 percent of people, from babies to adults, can sleep with their eyes open! Astronauts cannot cry in space--at least not the usual way. Without gravity, tears don't fall downward out of the eye. Instead, they form into little balls of liquid that hang out in the eye and cause a stinging sensation. And according to astronaut Chris Hadfield, space tears can really sting! RECORD-BREAKING WOW! In 2007, Kim Goodman "popped" her eyeballs .47 inches (12 mm) beyond her eye sockets and became the Guinness World Record holder for the Farthest Eyeball Pop. Don't try this at home. Two Whats?! and a Wow Use your eyeballs to spot the true wow among the totally made-up whats?!: If unprotected, your eyes can get sunburned. If you sneeze with your eyes open, your eyeballs will pop out of your face. One out of ten humans suffer from "ticklish eyes." ANSWERS wow what?! what?! Quiz--The Eye Exam The most common eye color in the world is . . . (A) Blue (B) Hazel (C) Brown (D) Mismatched colors Eye transplants are . . . (A) Fun (B) A pain in the eye (C) Dangerous but worth it (D) Currently impossible ANSWERS (C) Brown. Over half of the people in the world have brown eyes. (D) Currently impossible. Surgeons are unable to rewire the one million fibers that make up the optic nerve, which connects the eye to the brain. But, it is possible to get a cornea transplant. Excerpted from Wow in the World: the How and Wow of the Human Body: From Your Tongue to Your Toes and All the Guts in Between by Mindy Thomas, Guy Raz All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
