Why does dehydration elevate plasma osmolality leading to increased water reabsorption in the kidneys?

💡 Explanation

Elevated plasma osmolality triggers the release of antidiuretic hormone (ADH), because ADH increases the permeability of the collecting ducts in the kidneys to water. Therefore, more water is reabsorbed back into the bloodstream, rather than being excreted in urine, decreasing plasma osmolality.

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