Dear James and Zion,

Despite being a curious science cat, I must confess I haven’t spent much time looking up human noses. But I have noticed that human nostrils can be a bit…furry.

I talked about what’s inside your nose with my friend Edward Johnson. He teaches classes about the human body in the School of Biological Sciences at Washington State University.

He told me that nose hairs only grow in your nose’s vestibule. That’s the inside of the part of your nostrils that you can flare out. The nose hair’s job is to filter the air you breathe in through your nose.

When you breathe in, air enters your nose of course. But so do other things like little bits of dust, pollen and pollution like from wildfire smoke. Sometimes bacteria and viruses are hanging out in the air you breathe, too.

Your nose hairs are like guards for the entrance to your nose.

“They’re part of the air cleansing system that’s all through the upper nasal airways,” Johnson said. “So, by the time the air gets down into your lungs and into the exchange surfaces, hopefully it’s pretty clean.”

Your nose hairs physically block bigger stuff from entering your nose. But there’s more to it than that. The whole inside of your nose—and your nose hairs—are covered with thick, gooey mucus. All the stuff you breathe in with the air get stuck in that mucus.

Then special parts that stick out of the cells that line your nasal cavity kick in. They’re called cilia. The cells and cilia are too small to see with just your eyes. But if you zoomed in with a microscope, the cilia look like little hairs or itty-bitty fingers.

The cilia bend and sweep back and forth. That moves all that thick, sticky mucus up your nose and back toward your throat. All the little bits of stuff stuck in the mucus go with it. Then, when you swallow, the mucus slides down into your digestive system.

The cilia (teal) move out particles (olive green) after they get stuck in the mucus (clear). Here that’s happening in the windpipe, but it happens in your nasal cavity, too. Image: staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2); cropped by Dr. Universe

You have a similar setup in your windpipe—also called the trachea. There, the cilia move the mucus up the windpipe like an escalator. Once it’s in your throat, you either swallow it or cough it out.

If that sounds a little bit gross, remember that some of us hack up hairballs.

But the great news is that a lot of that dust, pollen and smoke—as well as those bacteria or viruses that could make you sick—have been filtered out of the air you breathed in. It’s all thanks to those mucus-coated hairs and sweeping cilia.

I guess nature really nose what it’s doing.


Dr. Universe