(Describer) An animated ball becomes an amoeba and a rocket. Title:

(singers) ♪ Science ♪

♪ Out loud ♪♪

(Describer) Putting on rainbow wristbands and headbands, a woman runs.

(man narrating) We are the most complex technology on the planet. Our bodies, honed by thousands of years of evolution. Our brains, capable of billions of calculations per second. Our position on the food chain? The top.

(Describer) She stares at a burrito.

[bobcat snarls]

We are humans.

(Describer) She runs upstairs and trips.

Bow down before our physiological majesty. Hear us...

(Describer) She sneezes and lies on a couch.

[sneezes]

Okay, so this might be our weak point.

(Describer) She sits up.

Or is it? Yeah, mucus oozes out of us when we're sick, but it's also... One important defense mechanism our body sets up to protect us.

(Describer) Professor Katharina Ribbeck:

She would know. So mucus, which we call snot, is actually everywhere. It's human motor oil. It's in your nose, on your eyes, in your throat, lungs, stomach, intestines, lady parts, dude parts. The stuff that makes up mucus is between almost every single cell in your body, and you make a gallon of it every day.

(Describer) Outside...

Mucus protects you in a ton of different ways. The first way is by moisturizing. Mucus is a meshwork of proteins with long sugars branching off of it. This combo, called mucin, can bind to and retain an insane amount of water.

(Describer) By a river...

Big deal, right? It is a big deal. Without that moisture, you couldn't eat without ripping up your esophagus. Your eyes would dry out, and your airways, lungs, and throat wouldn't trap and dispose of particles, which brings up way number two.

(Describer) Her eye is shown close-up.

(woman) Your body constantly secretes mucus when your eyes tear up, or you blow your nose, or you swallow your post nasal drip, or you go to the bathroom.

(Describer) In a car...

By trapping unwanted particles, this mucus system is like a car wash that's flushing out germs before they can take hold.

(Describer) The car goes through one, with soapy water running down windows. In a lab, samples are shaken by a machine. The woman holds a clear material in a cup.

This is fake snot made from corn syrup, gelatin, and water. It's disgustingly convincing and would do a decent job at moisturizing and protecting against particles. But real mucus is loaded with immune cells that fight bacteria and viruses. And the chemical structure of mucins keeps bacteria moving by giving them handholds to propel themselves on. If bacteria stop moving, they could clump together to form biofilms, which even the toughest antibiotics can't always kill. Researchers are trying to learn from our own body's natural defenses to understand and fight infections. In fact, studying mucus could help us with many different things-- antibiotic resistance, cavities in our teeth, respiratory disease, even preterm labor. We're trying to see if we can use mucus to predict if a woman is at risk of delivering a baby too early. And mucus doesn't just sit there. It changes and adapts to its environment. Take cervical mucus. You ladies don't want random stuff getting in your uterus, and mucus helps protect against germs. But when a woman wants to have a baby, mucus lets sperm through. When she ovulates, it physically and biologically changes to let that happen. And when mucus does let stuff like good bacteria, or sperm, or certain particles through, it doesn't get ripped up but instead restores its original mechanical properties and self-heals, which is something that no single man-made material can do nearly as well or as easily.

(Describer) In a gym...

So, see, we are majestic specimens of life on Earth. We are humans. Bow down before us. Hear us...

[sneezes]

(Describer) Title: Made with love at MIT.

Accessibility provided by the U.S. Department of Education. Hi, guys, it's Elizabeth. Thanks for watching Science Out Loud. If you liked it, subscribe to our channel. And if you want to learn more about snot, go to our website at k12videos.mit.edu. Cut. Uh!

(Describer) She smiles and stretches her arms. Accessibility provided by the U.S. Department of Education.