diffusion

(dif-ū′zhŏn )

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[L. diffusio, pouring out, spreading out]
The tendency of the molecules of a substance (gas, liquid, or solid) to move from a region of high concentration to one of lower concentration. In the body, oxygen and carbon dioxide move by diffusion. The diffusion of water to an area of greater solute concentration is called osmosis.
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DIFFUSION OF RESPIRATORY GASES

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