AOK Invaders

Urine is an aqueous solution of waste electrolytes and metabolites excreted by mammals, birds, reptiles, fish and amphibians. Although urine is excreted as a paste (uric acid) by most birds, it is commonly excreted as a fluid varying in color from clear, when dilute, to a dark amber, when concentrated. Urine is produced by the kidneys, and plays a vital role in maintaining homeostasis by removing excess water, electrolytes such as sodium, chloride, potassium, and calcium ions, urea and other metabolites from the blood. Urine excreted by healthy kidneys is sterile. The production of urine is called diuresis.