lesson
Moving air and exchanging gases are different
1 · Learn
Breathing moves air into and out of the lungs. Gas exchange transfers oxygen into the blood and carbon dioxide out across the surfaces of tiny air sacs called alveoli. Their large combined area, thin barriers and blood supply support exchange.
When the diaphragm contracts and moves down and the chest expands, pressure inside falls relative to outside and air enters. A model bottle-and-balloon system illustrates pressure but does not reproduce every structure of the chest.
2 · Worked example
I distinguish inhaling air from oxygen diffusing into blood. Air does not simply flow as whole bubbles through blood vessels.
3 · Your turn
Why does a thin exchange barrier help diffusion?
Check your answer
It shortens the distance particles travel across the exchange surface.
4 · Apply your learning
Label a supplied lung diagram and identify one strength and one limitation of an approved breathing model.
Adult guidance and safety
Use supplied evidence and approved diagrams. Practical work requires a qualified adult, suitable equipment and a risk assessment. No unsupervised chemicals, heating, flames, mains electricity or bright-light experiments. Human biology is factual education, not personalised medical advice; never request intimate or health disclosures.
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