Why do we cry? The three types of tears - Alex Gendler

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Whether we cry during a sad movie, while chopping onions, or completely involuntarily, our eyes are constantly producing tears. Alex Gendler tracks a particularly watery day in the life of Iris (the iris) as she cycles through basal, reflex and emotional tears.

Lesson by Alex Gendler, animation by The Moving Company Animation Studio.

Our story is about a girl named Iris.

Iris is very sensitive.

So much that she is always in tears.

She cries when she's sad,

when she's happy,

and even tears up when things just get to her.

She has special lacrimal glands to make new tears

and special tubes, called lacrimal puncta,

to drain old ones away.

And she cries so much that she goes through

ten ounces of tears per day,

30 gallons a year!

In fact, if you look closely,

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

The basal tears that Iris constantly produces

form a thin coating of three layers,

that cover her and keep dirt and debris away.

Right next to Iris is the mucus layer,

which keeps the whole thing fastened to her.