Liquid solution of metabolic wastes and other, often toxic, substances filtered from plasma. The fluid in the Bowman capsule at the start of each nephron is essentially plasma without the large molecules (e.g., proteins). The concentrated fluid (final urine) that exits the kidney consists of water, urea, inorganic salts, uric acid, creatinine, ammonia, and broken-down blood pigments, including urochrome, which makes urine yellow, plus any unusual substances not reabsorbed into the blood. This is then excreted. See also hematuria; urinalysis; urinary system; urination.

This entry comes from Encyclopædia Britannica Concise.
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