Why do we have snot?

[MUSIC PLAYING] Science out loud. [MUSIC PLAYING] We are the most complex technology of the planet. Our bodies, honed by thousands of years of evolution. Our brains, capable of billions of calculations a second. Our position on the food chain, the top. We are humans. Bow down before our physiological majesty. Hear us. [SNEEZE] OK, so this might be our weak point. Or is it? I mean, yeah, mucus is the stuff that oozes out of us when we're sick. But it's also-- One important defense mechanism our body sets up to protect us. She would know. So mucus, which is the stuff that we call snot, is actually everywhere, like it's human motor oil. It's not just in your nose. It's on your eyes, and your throat, lungs, stomach, intestines, lady parts, dude parts. In fact, the stuff that makes up mucus is between almost every single cell in your body. And it's so important that you make a gallon of it every day. And all this mucous protects you in a ton of different ways. The first way is by moisturizing. See, mucus is a mesh work made up of these proteins with all these long sugars branching off of it. And this combo is called a mucin. And it can bind to and retain an insane amount of water. Big deal, right? Well, it is a big deal. Without that moisture, you wouldn't be able to eat without ripping up your esophagus. Your eyes would dry out and you wouldn't be able to blink. And your airways, lungs, and throat wouldn't be able to trap particles and get rid of them, which brings me to way number two. Your body constantly secretes mucus when your eyes tear up, or you blow your nose, or you cough, or you swallow your post nasal drip, or you go to the bathroom. By trapping unwanted particles, this mucus system is like a carwash that's constantly flushing out germs before they have a chance to take hold. [MUSIC PLAYING] So this is fake snot made out of corn syrup, gelatin, and water. And 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 hand holds 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 a lot of different things, antibiotic resistance, cavities in our teeth, respiratory disease, even preterm labor. My research group is 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. For example, cervical mucus-- now 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, that mucus has to somehow let sperm through. And it does. 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's so crazy that not a single manmade material can do nearly as well or as easily. So see, we are majestic specimens of life on earth. We are humans. Bow down before us. Hear us. [SNEEZE] Hi, guys. It's Elizabeth. Thanks for watching this episode of Science Out Loud. If you liked it, check out some of our other videos and subscribe to our channel. And if you want to learn more about the awesome science of snot, go to our website at k12videos.mit.edu. Cut. Ahh. Cut. [LAUGHTER]