Lungs and Breathing: Follow Oxygen Inside
Understand that breathing works by changing the volume of the chest, which changes the pressure inside so air flows in or out, and that gas exchange happens by diffusion in the alveoli.
Before you try
What if your lungs had to pull air in by themselves? Could they manage it?
Try it out
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What happened?
Move a control to see what changes and why.
Breathing is driven by one diaphragm control. Real breathing also uses the rib muscles, and adjusts by itself to what your body needs.
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Try these ideas
- Move the diaphragm slider slowly by hand and watch the airflow arrows change.
- Turn on automatic breathing and raise the rate to 24 breaths a minute.
- Watch the alveolus zoom and identify which circles move which way.
Why it works
Lungs are not muscles and cannot suck. The diaphragm, a sheet of muscle under them, contracts and flattens while the ribs swing up and out. That makes the space in the chest bigger, which lowers the pressure inside, and air from outside pushes its way in. Relax the diaphragm and the space shrinks, the pressure rises and air is pushed back out. A quiet breath moves about half a litre of air.
Deep inside are millions of tiny air sacs called alveoli, each wrapped in blood capillaries. Oxygen diffuses from the air into the blood and carbon dioxide diffuses the other way, purely because each gas moves from where it is plentiful to where it is scarce. This simulator shows quiet tidal breathing only, so exercise breathing would be deeper and faster than the model allows.
Check your understanding
Question 1 of 4
What makes air flow into the lungs?
What does the diaphragm do when you breathe in?
Where does oxygen enter the blood?
You breathe 15 times a minute, half a litre each time. How much air is that?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Put a hand on your stomach and feel it move as you breathe deeply.
- Count breaths at rest and after running, then compare.
- Ask why divers carry tanks of air rather than tanks of oxygen alone.