A pair of bean-shaped organs that filter waste products and excess water from blood to produce urine. They also regulate blood pressure and produce hormones essential for red blood cell production.
From Middle English 'kidnei,' possibly from Old English 'cwith' (womb) and 'nēre' (kidney), or from 'kid' (young goat) referring to the organ's shape. The modern spelling emerged in the 14th century as anatomical knowledge improved.
Your kidneys process about 50 gallons of blood daily, essentially cleaning your entire blood supply multiple times - they're like tireless janitors working 24/7. Remarkably, you can live normally with just one kidney, as a single healthy kidney can perform about 75% of normal kidney function.
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