Here's everything you ever wanted to know about snot.

Spoiler alert: You swallow a ton of this stuff everyday.

I'm Anna and this is Gross Science.

It might seem like a bummer when you have a cold, but snot is truly terrific stuff.

Snot is what we call the mucus that comes out of our noses, but we actually produce similar, slimy substances all over our bodies-from our lungs, to our guts, to our private parts.

And all this mucus is actually vital to our survival.

Mucus keeps us healthy by keeping our delicate body tissues moist, and by trapping particles that might irritate or infect us.

And snot is one of our first lines of defense, since about 80% of our body's air filtration happens in the nose.

So, how does it work?

Well, special types of cells called "goblet" cells in the membranes lining your nose produce proteins called "mucins."

Mucins are long protein chains that are great at linking up with one another, and are heavily "glycosylated."

That means that they have lots of sugar groups attached to them.

And this chemical sugar coating means that they can absorb lots of water.

In fact, mucus is about 95% water.

(And, as a quick side note, boogers are just snot that's dried up a bit.)

Anyway, we produce a ton of this stuff.

When you're healthy, you make a little under half a cup of mucus a day-and that's just in your nose.

So when you breath in, all that mucus traps any harmful particles that may have hitched a ride on the incoming air.

If any pathogens, like bacteria or viruses, are trapped, antimicrobial agents in the mucus, like lysozymes, may help to destroy them, and antibodies may help recruit immune cells to deal with the invaders.

Throughout the day, you have a steady stream of mucus moving over your nasal passages.

Certain cells lining your nose have small, hair-like projects sticking off of them called "cilia."

These cilia beat through the mucus, and move it about a millimeter per second toward your throat, where you swallow it down.

That's right, you swallow most of the snot you produce everyday, probably without even realizing it.

And that's just when you're healthy.

But what about when you're sick?

A runny nose and nasal congestion mean that a pathogen has managed to sneak through the mucus defense.

So, your body springs into action.

First of all, it starts producing more mucus, to flush the pathogens out.

But it also sends lots of immune cells to the area to battle the invaders.

Along with this influx of immune cells may come some inflammation of the nasal passages.

Specifically, structures on the sides of your nose that help warm the incoming air, called nasal turbinates, may swell, making it difficult to breath.

So, it may not exactly be an excess of snot that causes congestion, but all the nasal inflammation.

Your sinuses may also get infected and inflamed.

Sinuses are air pockets in the bones of your face, that also produce mucus.

You actually have four of them on each side of your head.

And when the membranes of the sinuses swell, mucus and air can get trapped, which cause the headaches and facial pressure that can sometime come with a cold.

Anyway, while congestion and runny noses may be unpleasant, they're just a sign that your body is doing its job and protecting you from invaders.

So maybe next time you get a sniffle, you'll be able to appreciate your snot a little bit more.

Ew.

What do the different colors of snot mean?

And how do all those cold medicines really work?

Head over to Reactions to learn even more snotty science.

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Thanks.

I'll see you next week.