Erotusjärjestelmä

Erotusjärjestelmä, known in English as the excretory system, is a biological system in multicellular organisms responsible for the elimination of waste products from the body. These waste products include metabolic byproducts, excess substances, and toxins. The primary function of the excretory system is to maintain homeostasis, the stable internal environment necessary for life.

The most common form of excretion involves the removal of nitrogenous wastes, which are byproducts of protein metabolism. These include urea, uric acid, and ammonia. The specific nitrogenous waste excreted varies depending on the organism and its environment. For instance, aquatic animals often excrete ammonia, which is highly toxic but can be diluted in water, while terrestrial animals, especially birds and reptiles, excrete less toxic uric acid in a semi-solid form to conserve water. Mammals primarily excrete urea.

In vertebrates, the kidneys are the principal organs of the excretory system. They filter blood, reabsorbing useful substances and secreting waste products into urine. Urine is then transported through ureters to the bladder for storage and expelled from the body through the urethra. Other organs also contribute to excretion. The lungs remove carbon dioxide, a waste product of cellular respiration. The skin eliminates sweat, which contains water, salts, and some urea. The liver plays a role by detoxifying harmful substances and converting them into less harmful compounds that can be excreted by the kidneys or bile.

The efficiency and complexity of the excretory system vary greatly among different species, reflecting their evolutionary adaptations to diverse environments and metabolic needs. Understanding the excretory system is fundamental to comprehending organismal physiology and health.