Mystery #2Tier 2-3body / lungs

How do your lungs pull in air?

Your lungs have no muscles of their own to suck in air; they're soft, floppy bags. Yet air rushes in and out all day long. So what's actually doing the pulling?

A diagram of the diaphragm muscle moving down and up to draw air into the lungs and push it out. — Photo: Cruithne9 · CC BY-SA 4.0 · via Wikimedia Commons

Your guess

What's your hunch: if your lungs can't pull on their own, what makes air rush into them?

There's no single magic word to type, have a go in your own words, then reveal the answer to see how close you got.

Make a guess to unlock the hints and the answer.