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Can you explain how this works. Why does the top balloon inflate and deflate as you pull or push the bottom balloon. Thanks. I’m having trouble explains this to my students.



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The activity can be viewed at: Explore How Lung Infection Influences Breathing

Hi!

Thank you for your question!

This phenomenon is really all about pressure and volume. Pulling down on the knot is symbolic of the diaphragm contracting and flattening. This allows the chest cavity (or the balloon, in this analogy) to enlarge, effectively creating a vacuum of lower-pressure air. As a result, air rushes in and fills the lungs. Once the knot/diaphragm returns to its normal position, the chest cavity/balloon must return to its smaller size – effectively forcing air out, as it now has less space in the lungs.

The key thing to remember here is that lower pressure (of air) results from greater volume (of the chest cavity/balloon), and high pressure is a result of lesser volume.

This link may also be helpful for a detailed scientific explanation of this phenomenon: https://medlineplus.gov/ency/anatomyvid ... he%20lungs..

Hope this helps!