[oz-moh-reg-yuh-ley-shuhn, os-]
the process by which cells and simple organisms maintain fluid and electrolyte balance with their surroundings.

1930–35; osmo- + regulation

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World English Dictionary
osmoregulation (ˌɒzməʊˌrɛɡjʊˈleɪʃən)
zoology the adjustment of the osmotic pressure of a cell or organism in relation to the surrounding fluid

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American Heritage
Medical Dictionary

osmoregulation n.
The maintenance of an optimal constant osmotic pressure in the body of a living organism.

os'mo·reg'u·la·to'ry (-lə-tôr'ē, -tōr'ē) adj.
The American Heritage® Stedman's Medical Dictionary
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Encyclopedia Britannica


in biology, maintenance by an organism of an internal balance between water and dissolved materials regardless of environmental conditions. In many marine organisms osmosis (the passage of solvent through a semipermeable membrane) occurs without any need for regulatory mechanisms because the cells have the same osmotic pressure as the sea. Other organisms, however, must actively take on, conserve, or excrete water or salts in order to maintain their internal water-mineral content.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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