How do kidneys clean the blood without removing too much water?
Quick Answer
Kidneys filter blood through millions of nephrons, then reabsorb needed water, salts, and nutrients. On average, they make about 1 to 2 litres of urine per day.
The Full Story
Each kidney contains about a million nephrons, which are tiny filtering units. Blood is filtered in the glomerulus, then the useful substances and most water are reabsorbed along the tubules according to the body's needs. Hormones such as ADH and aldosterone help regulate how much water and salt are kept or lost. The result is a delicate balance between cleansing the blood and preserving hydration. This system is one reason the kidneys are among the body’s most precisely regulated organs.
Key Facts
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