Chest models and how fish breathe
When you breathe in, the muscle under your lungs, the diaphragm, moves down and your ribs move up and out. The chest gets bigger and air flows in. When you breathe out, the diaphragm moves up, the ribs move back, the chest gets smaller and air flows out. You can feel this by putting a hand on your chest and taking a deep breath. You can measure it too: a tape around the chest is a bit longer when you breathe in. A bottle and balloon model can show the idea, but an adult must cut the bottle. Fish live in water. Dissolved oxygen in water passes into their blood through gills, and carbon dioxide leaves through the gills too. Fish do not have lungs like ours.
| Breathing in | Breathing out | |
|---|---|---|
| Diaphragm | moves down | moves up |
| Ribs | move up and out | move back |
| Chest | bigger | smaller |
| Air | flows in | flows out |
| Chest | Tape reading |
|---|---|
| after breathing out | 70 cm |
| after breathing in | 73 cm |
Hand on the chest. With a grown-up, put one hand on your chest and one on your tummy. Breathe in slowly three times and feel which part rises. Then measure your chest with a soft tape after breathing out and after breathing in. Write the two numbers and subtract.