Breathing and Spirometers

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  • Created by: Chris
  • Created on: 28-11-10 16:15

Ventilation is broken down into inspiration and expiration, its controlled by the movement of the diaphragm, intercostal muscles and the ribcage.


1. The intercostal muscles and diaphragm contract.

2. The ribcage moves upwards and outwards, the diaphragm flattens.

3. The volume of the thorax increases.

4. As the volume increases, the pressure decreases meaning that air flows into the lungs.

5. Inspiration is an active process.



1. The intercostal muscles and diaphragm relax.

2. The ribcage moves downwards and inwards, the diaphragm curves.

3. The volume of the thorax decreases.

4. As the volume decreases, the pressure increases meaning that air flows out of the lungs.

5. Expiration is a passive process.

Spirometers: A spirometer has an…


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