School › Heart and lungs › Ages 10–11
How breathing works
The path of air into the lungs, the diaphragm, gas exchange, and the heart as a double pump. With a model-lung experiment.
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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.[2]
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.[2]
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.[3]
The heart has four chambers: two atria at the top receive blood and two ventricles at the bottom pump it out. Valves stop the blood flowing backwards.[1]
The heart is really two pumps side by side. The right side sends blood to the lungs to pick up oxygen. The left side sends that oxygen-rich blood to the rest of the body.[1][4]
Arteries carry blood away from the heart, veins bring it back, and capillaries are where oxygen and food pass into the body's cells.[4]
Try it: Make a model lung
You need
- A clear plastic bottle (about 1.5 L), bottom cut off by an adult
- Two balloons
- A drinking straw (or a Y-shaped tube)
- Modelling clay or Blu-Tack
- Sticky tape
- Scissors (adult only)
Safety
Only an adult cuts the bottle; cover the cut edge with tape. Anyone with a latex allergy uses latex-free balloons or watches. Don't put balloons or bits of balloon in your mouth.
What to do
- An adult cuts the bottom off the bottle and tapes over the sharp edge.
- Push a straw into the neck of one balloon and tape it airtight. This balloon is a lung; the straw is the windpipe.
- Put the balloon inside the bottle with the straw sticking out of the neck. Seal the neck around the straw with modelling clay.
- 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.
- Gently pull the knot down. What happens to the balloon inside? Push it up. What happens now?
What happens, and why?
Pulling the 'diaphragm' down makes more space inside the bottle, so air rushes in through the straw and the 'lung' inflates, just like your lungs when your diaphragm moves down. Pushing it up squeezes the air back out.[3]
Play: Follow the path
Sort each part: does air pass through it, does blood pass through it, or is it a muscle that pumps or moves?
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 6–7 · Ages 15–16