The air tube
When you breathe in, air goes through your nose or mouth, down your throat, past your voice box and into your windpipe. Its science name is the trachea.
Your windpipe runs down the front of your neck into your chest. In a grown-up it's about 4 to 5 inches long and about an inch wide.
At the bottom, the windpipe splits in two, like an upside-down letter Y. The two branches are called bronchi (BRONG-kye). One goes to your left lung and one goes to your right lung.
Rings that keep it open
Your windpipe is held open by about 16 to 20 rings of cartilage, the tough, bendy stuff that's also in your ears.
The rings are shaped like the letter C, open at the back. Your food pipe sits right behind, and the open part gives it room to bulge when you swallow a big bite.
Try it: gently feel the front of your neck below your voice box. Those small ridges are your windpipe's rings!
The rings work like the coils in a vacuum cleaner hose. You can bend your neck any way you like, and the tube stays open.
Tiny sweepers
Your windpipe is lined with sticky mucus that traps dust, pollen and germs.
It's also covered with millions of tiny hairs called cilia. They wave back and forth, sweeping the mucus up toward your throat like a moving walkway. Then you swallow it or cough it out.
This cleaning crew works all day and all night to keep your lungs clean.
The wrong pipe
Your windpipe and your food pipe both start at the back of your throat. So how does food know where to go?
A little flap called the epiglottis acts like a trapdoor. When you swallow, it covers your windpipe so food and drinks slide into your food pipe instead.
If you laugh or talk while you eat, the trapdoor can be too slow, and a crumb goes down the wrong pipe. Your body coughs hard to blast it back out. Here, coughing is a good thing!
That's why it's smart to sit down, take small bites and chew well when you eat.