Biology 4.3 Exchange of Gases in the Lungs

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  • Created by: Anna
  • Created on: 21-04-13 17:04

Site of gas exchange in mammals = epithelium of alveoli.

Alveoli - minute air sacs 100-300um in diameter.

Essential features of exchange surfaces

  • Large surface area to volume ratio - speeds up rate of exchange.
  • Very thin - short diffusion pathway so materials can cross rapidly.
  • Partially pemeable - selected materials diffuse through easily.
  • Movement of environmental medium e.g. air - maintain a diffusion gradient.
  • Movement of internal medium e.g. blood - maintain a diffusion gradient.

Diffusion is proportional to: (surface area x difference in concentration…


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