Structural and functional organization of excretory organs/excretory system in animals.

Priya sarda

The kidney and urinary systems help the body to eliminate liquid waste called urea and to keep chemicals, such as potassium and sodium, and water in balance. Urea is carried in the bloodstream to the kidneys, where it is removed along with water and other wastes in the form of urine. The excretory system is the system of an organism’s body that performs the function of excretion, the bodily process of discharging wastes. The Excretory system is responsible for the elimination of wastes produced by homeostasis. The excretory system is very important to your body and only has a few parts. In a similar way to removing solid waste from your body. Functions of the excretory system: Collect water and filter body fluids Remove and concentrate water products from body fluids and return other substance. Eliminate excretory products from the body. Modes of Excretion Based on the excretory product, five modes of excretion are known in animals. They are: Ammonotelism (Type of excretion- ammonia) Ureotelism (Type of excretion – urea) Uricotelism (Type of excretion – uric acid) Aminotelism (Type of excretion – amino acids) Guanotelism (Type of excretion – guanine) Ammonotelism The process of eliminating ammonia from the body is known as ammonotelism, and the organisms which exhibit this nature are called ammonotelic. Most fish, protozoans, echinoderms, poriferans and crustaceans fall into this category. Aquatic animals excrete ammonia directly into the environment; where the compound is quickly diluted. It is also very toxic to tissues. Ureotelism In some mammals and amphibians, urea is excreted as the metabolic waste products. Such organisms are called ureotelic. In these organisms, ammonia that is produced is converted to urea in the liver of animals and is released back into the blood. The kidneys filter the urea and are expelled outside the body. Some of the urea is retained in the matrix of the kidney to maintain a desired osmolarity in the organisms. Humans are ureotelic as we expel the urea through urine. Moreover, urea is comparatively less toxic than ammonia. Uricotelism Uricotelic animals remove nitrogenous wastes as uric acid in the form of pellets or paste. Metabolically, this process is quite costly; however, the water loss is minimal, and it is the least toxic. Moreover, since uric acid is not readily soluble in water, the excrements form pasty white suspensions. Most reptiles, birds, and insects are classified as uricotelics. Aminotelism Certain molluscs and echinoderms excrete excess amino acids. This feature is called aminotelism. Guanotelism Spiders convert the ammonia into guanine before excretion. This characteristic is also found in some reptiles, birds and earthworms. It is also insoluble in water; hence no water is required for its excretion. Excretion Examples & Structures All vertebrates have kidneys – Excretory product is urea Flame cells in planaria Earthworms have Nephridia Cockroaches have malpighian tubules Prawns have antennal glands or green glands