How do the lungs work?

You breathe about 20,000 times a day without thinking. Air flows through your nose, throat and voice box into the windpipe, which splits into two bronchi. They branch about 23 times, ending in roughly 480 million tiny air sacs called alveoli.

Read how it works: How do the lungs work? · The history of the lungs · More boxes on Glassbox

Chapters in this interactive model

1. The breathing system: From your nose to 480 million tiny air sacs, in a cage of ribs.
2. How we breathe: Boyle’s law: Make the chest bigger, the pressure inside drops, and air rushes in.
3. Swapping gases in the alveoli: Oxygen slips into the blood, carbon dioxide slips out, all by diffusion.
4. How blood carries oxygen: Haemoglobin grabs oxygen in the lungs and lets it go where it is needed.
5. How much air your lungs hold: Blow into a spirometer and see your lung volumes drawn as a line.
6. Keeping lungs healthy: How your airways clean themselves, and what smoke, dirty air and illness do.