Why is a good blood supply necessary for a good exchange surface?

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Ok so I know the four main factors for a good exchange surface are; 

  1. Large surface area- so there is more capacity for exchange to occur
  2. Thin wall - Short diffusion path 
  3. Ventilated
  4. Good blood supply

But I'm not sure why a good blood supply is so important for it to be a good exchange surface - unless it's just to do with the diffusion of co2 from the blood (and if so is this only applicable in gaseous exchange?)

Your help would be so much appreciated 

thanks guys 

Evie ***

Posted Tue 16th April, 2013 @ 19:21 by zoe3027

1 Answer

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Good blood flow in capillaries maintains:

  • High concentration of Carbon Dioxide in the capillary
  • Low concentration of Oxygen in the capillary

So more oxygen diffuses in, and more carbon dioxide diffuses out down their concentration gradients.

Answered Tue 16th April, 2013 @ 20:02 by Charlotte