Excreted

Excreted is the past participle of excrete. In biology, excretion refers to the process by which organisms eliminate metabolic wastes and other non-useful substances from their bodies.

In animals, excretion relies on specialized organs that remove wastes from the circulatory system. The kidneys filter blood to form urine, which is excreted through the urinary tract; the liver converts certain wastes into water-soluble forms such as bile pigments; the lungs expel carbon dioxide and water vapor; the skin releases sweat containing salts and small amounts of waste.

Feces are the solid waste remaining after digestion and absorption; they contain undigested matter, bacterial biomass, and bile pigments. Nitrogenous wastes such as urea or uric acid are excreted in urine or, in some species, as solid waste; ammonia is excreted directly by aquatic animals.

Excretion is distinct from secretion, the production and release of substances such as enzymes, hormones, or mucus that serve a physiological function rather than being waste. Excretion results in the removal of toxins and metabolic byproducts to maintain internal balance.

In plants and some microorganisms, excretion occurs less through dedicated organs and more via guttation, resin or latex release, and the emission of volatile compounds; some wastes may be excreted from roots or leaves.

Proper excretion is essential for homeostasis; impaired excretory function can lead to toxin buildup, disease, or environmental impact. In humans, kidney or liver disease can disrupt excretion; dialysis or transplantation may be required.