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Our story is about a girl named Iris.

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Iris is very sensitive.

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So much that she is always in tears.

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She cries when she's sad,

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when she's happy,

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and even tears up when things just get to her.

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She has special lacrimal glands to make new tears

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and special tubes, called lacrimal puncta,

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to drain old ones away.

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And she cries so much that she goes through

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ten ounces of tears per day,

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thirty gallons a year!

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In fact, if you look closely,

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you'll see that she's crying a little bit all the time.

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The basal tears that Iris constantly produces

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form a thin coating of three layers

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that cover her and keep dirt and debris away.

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Right next to Iris is the mucus layer,

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which keeps the whole thing fastened to her.

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On top of it is the aqueous layer,

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which keeps Iris hydrated,

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repels invasive bacteria,

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and protects her skin, or cornea, from damage.

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And, finally, there is the lipid layer,

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an oily outer film that keeps the surface smooth

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for Iris to see through,

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and prevents the other layers from evaporating.

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Normally, Iris goes about her day

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without really noticing the basal tears

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doing their thing.

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That's kind of their whole point.

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But one day, she meets a girl named Onion.

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Iris is immediately smitten.

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Onion looks gorgeous in her bright purple jacket,

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and she smells terrific.

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So, Iris invites Onion to her house for dinner,

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but when she comes in and takes off her jacket,

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something terrible happens.

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You see, when Onion's jacket is removed,

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a chemical reaction happens,

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converting the sulfoxides that make her smell so great

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into sulfenic acid,

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which then becomes a nasty substance with a long name:

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syn-Propanethial S-oxide.

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The gas stings Iris,

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and suddenenly, she can't help it,

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she starts weeping uncontrollably.

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These reflex tears are different from the basal tears

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that Iris is used to.

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Because they're designed

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to wash away harmful substances, or particles,

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they're released in much larger amounts,

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and their aqueous layer contains more antibodies

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to stop any microorganisms that may be trying to get in, as well.

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Both Iris and Onion are devastated.

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They know they can't continue their relationship

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if Iris is going to hurt and cry

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every time Onion takes off her jacket.

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So, they decide to break up.

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As Onion walks out the door,

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Iris stops crying.

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And immediately starts again.

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Only now, she's not crying reflex tears

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but emotional tears.

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When someone is either too sad or too happy,

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it feels like a loss of control,

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which can be dangerous.

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So, emotional tears are sent in

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to stabilize the mood

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as quickly as possible,

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along with other physical reactions,

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such as an increased heart rate

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and slower breathing.

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But scientists still aren't sure

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exactly how or why the tears themselves are helpful.

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They may be a social mechanism

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to elicit sympathy or show submission.

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But some studies have also found

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that emotional tears contain higher levels

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of stress hormones,

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such as ACTH and enkephalin,

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an endorphin and natural pain killer.

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In this case, emotional tears are also directly calming Iris down,

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as well as signaling her emotional state to others.

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Sorry things didn't work out with Onion, Iris,

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but don't worry.

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As long as you have all three kinds of tears

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working to keep you balanced and healthy,

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it will get better.

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You'll see.