final urine

Urine is a liquid waste product containing metabolic by-products and other substances expelled from the body by the excretory organs. Its composition reflects an organism's water needs, with freshwater animals excreting dilute urine and marine animals excreting concentrated urine to conserve water. Terrestrial animals also produce concentrated urine to retain water.1

In mammals, including humans, urine is formed in the kidneys. Blood plasma is filtered, and as the fluid moves through the nephron, useful components like water, amino acids, and glucose are reabsorbed into the bloodstream. The remaining concentrated solution of waste materials is called final urine. This final urine consists of water, urea (from amino acid metabolism), inorganic salts, creatinine, ammonia, and pigmented products that give urine its yellowish color. Any unusual substances not reabsorbed also remain in the urine.1