3.2.5

Breathing Process

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Breathing

Inspiration (breathing in) and expiration (breathing out) involve many parts of the thorax moving in the following steps:

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Inspiration

  • The diaphragm contracts and becomes flattened.
  • The internal intercostal muscles relax and the external intercostal muscles contract, moving the ribcage up and out.
  • The thorax volume increases, forcing air into the lungs because of decreased internal pressure.
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Expiration

  • The diaphragm relaxes and becomes dome-shaped.
  • The internal intercostal muscles contract and the external intercostal muscles relax, moving the ribcage downwards and in.
  • The thorax volume decreases, increasing internal pressure.
  • Air is forced out of the lungs.

Jump to other topics

1The Nature & Variety of Living Organisms

2Structure & Functions in Living Organisms

3Organism Functions

3.1Respiration

3.2Gas Exchange

3.3Transport

3.4Excretion

3.5Coordination & Response

4Reproduction & Inheritance

5Ecology

6Biological Resources

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