Science
How do the lungs work?
The lungs work by drawing in air and exchanging gases with your blood. Air flows down into millions of tiny sacs where oxygen passes into the bloodstream and carbon dioxide passes out to be exhaled — keeping every cell supplied with oxygen.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how the lungs works.
Step by step
- 1Air travels down the windpipe into branching airways.
- 2It ends in millions of tiny sacs called alveoli.
- 3Oxygen crosses the thin sac walls into the blood.
- 4Carbon dioxide passes the other way to be breathed out.
- 5A huge total surface area makes the exchange efficient.
Frequently asked questions
- How do the lungs get oxygen into the blood?
- In tiny air sacs (alveoli), oxygen diffuses across thin walls into surrounding blood vessels while carbon dioxide diffuses out.
- Why do the lungs have so many tiny sacs?
- The hundreds of millions of alveoli give a vast surface area — roughly the size of a tennis court — for fast gas exchange.
- What's the difference between breathing and gas exchange?
- Breathing moves air in and out; gas exchange is the actual swapping of oxygen and carbon dioxide between air and blood in the alveoli.