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Air enters through your nose or mouth, which warm and moisten it. It travels down the windpipe (trachea), which splits into two bronchi, then smaller and smaller bronchioles.

The bronchioles end in clusters of tiny air sacs called alveoli. Each one is wrapped in tiny blood vessels called capillaries. Oxygen passes from the air into the blood, and carbon dioxide passes from the blood into the air.

Breathing in: the diaphragm tightens and moves down, making room in your chest, and the lungs fill with air. Breathing out: the diaphragm relaxes and moves up, and air is pushed out.

Experiment: Make a model lung

1. An adult cuts the bottom off the bottle and tapes over the sharp edge.
2. Push a straw into the neck of one balloon and tape it airtight. This balloon is a lung; the straw is the windpipe.
3. Put the balloon inside the bottle with the straw sticking out of the neck. Seal the neck around the straw with modelling clay.
4. Tie a knot in the second balloon, cut off its round end (adult) and stretch it over the open bottom of the bottle. This is the diaphragm.
5. Gently pull the knot down. What happens to the balloon inside? Push it up. What happens now?

What I do to the diaphragm	What the lung balloon does	In my body this is…
Pull down	What will the balloon inside do when you pull the bottom down?
Push up	What will the balloon inside do when you pull the bottom down?

Questions

1. Put in order the path air takes: alveoli, nose, bronchioles, trachea, bronchi.

2. Explain what happened to your model lung when you pulled the 'diaphragm' down.

3. Why is the heart called a double pump?

4. Label a simple heart diagram: right atrium, left atrium, right ventricle, left ventricle.

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Sources for every fact on this sheet: echoesof.science/school/heart-and-lungs/sources/

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