Mon Prof Augmenté
Air moving in and out
Age 14 · Biology
Your chest changes size because of two sets of muscles: the dome-shaped diaphragm under the lungs and the muscles between the ribs. When the chest gets bigger the pressure inside drops and air flows in; when it gets smaller the air is pushed out.
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In the picture
- The diaphragm under the left lungs, pulled flat and low
- The rib wall of the left chest, lifted up and out
- The diaphragm under the right lungs, relaxed into a tall dome
- The right lungs, smaller and drawn away from the rib wall
Examples
- Blowing up a balloon: your chest tightens and air leaves your lungs through your mouth.
- A bicycle pump: pulling the handle draws air in, pushing it down forces air out.
Key takeaways
- Air moves because of a pressure difference: bigger chest, lower pressure, air flows in.
- At rest, breathing out is mainly the muscles relaxing rather than squeezing.
Quiz: Air moving in and out (Age 14)
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Why does air flow into the lungs when the chest gets bigger?
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What does the rib wall do when it helps make the chest bigger?
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At rest, what mainly causes air to be pushed out of the lungs?
The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.
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