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"Diffusion"

By Craig Weber, M.D., About.com

Updated: November 13, 2006

About.com Health's Disease and Condition content is reviewed by Rich Fogoros, MD

Definition: A type of passive transport(non-energy requiring) involving the movement of small molecules from an area where they are highly concentrated to an area where they are less concentrated. Diffusion is spontaneous and automatic.

Diffusion is the process that transfers:

  • oxygen to the blood in the lungs
  • oxygen out of the blood in the body tissues
  • carbon dioxide into the blood from the body tissues

Pronunciation: di-Fu-shun

Also Known As: Passive Transport

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