How does the respiratory system work?

You breathe about 20,000 times a day and never think about it. Air passes the nose, throat, voice box and windpipe, then branches about 23 times into roughly 480 million air sacs. The diaphragm and rib muscles do the pulling; the lungs themselves have no muscles.

Read how it works: How does the respiratory system work? · The history of breathing · More boxes on Glassbox

Chapters in this interactive model

1. The breathing system, nose to diaphragm: A tube that splits into a tree, a pair of sponges, and a muscle that pulls.
2. Air in, air out: the breathing pump: Make the chest bigger and the pressure inside drops, so air rushes in.
3. The journey of air: Warmed, wetted, cleaned, kept away from food, and turned into your voice.
4. From air sac to cell: Haemoglobin grabs oxygen in the lungs and lets it go where muscles are busy.
5. Control: the brainstem’s autopilot: You breathe about 20,000 times a day without thinking. Here is who does the thinking.
6. When breathing goes wrong: Narrow airways, filled air sacs, germs and dirty air, and how people get help.