Excretion is the process of eliminating waste products of metabolism and other materials that are of no use. It is an essential process in all forms of life. In one-celled organisms wastes are discharged through the surface of the cell. The higher plants eliminate gases through the stomata, or pores, on the leaf surface. They also have been shown (by British biologist Brian J. Ford) to translocate wastes into leaves which are then shed. In this fashion, the leaf, in addition to acting as an energy-trapping structure, is also a plant's organ of excretion. Brian J. Ford is a British independent scientist, prolific author and popular interpreter of scientific issues for the general populace, whose scientific papers and numerous books have been published internationally. ...

Multicellular animals have special excretory organs. In humans the main organs of excretion are the kidneys and accessory urinary organs, through which urine is eliminated (see urinary system), and the large intestines, from which solid wastes are expelled. The skin and lungs also have excretory functions: The skin eliminates water and salt in sweat, and the lungs expel water vapor and carbon dioxide." [1]

In mammals, for example, the two major excretory processes are the formation of urine in the kidneys and the formation of carbon dioxide (a human's most abundant metabolic waste) molecules as a result of respiration, which is then exhaled from the lungs. Orders Multituberculata (extinct) Palaeoryctoides (extinct) Triconodonta (extinct) Subclass Australosphenida Ausktribosphenida Monotremata Subclass Eutheria (excludes extinct ancestors) Afrosoricida Anagaloidea (extinct) Arctostylopida (extinct) Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Cingulata Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Dinocerata (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Leptictida (extinct) Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata... To meet Wikipedias quality standards, this article or section may require cleanup. ... Kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... Metabolism (from Greek μεταβολισμός metabolismos) is the biochemical modification of chemical compounds in living organisms and cells. ... Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ...

The waste products are eliminated by urination and exhalation respectively. In urination, Hormone control over excretion occurs in the distal tubules of the kidneys as directed by the hypothalamus. Urination, also called micturition, is the process of disposing urine from the urinary bladder through the urethra to the outside of the body. ... Hormone is also the NATO reporting name for the Soviet/Russian Kamov Ka-25 military helicopter. ... Kidney nephron The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting duct system. ... In the anatomy of mammals, the hypothalamus is a region of the brain located below the thalamus, forming the major portion of the ventral region of the diencephalon and functioning to regulate certain metabolic processes and other autonomic activities. ...

Perspiration is another excretory process which removes salts and water, although the primary purpose is cooling. Sweating (also called perspiration or sometimes transpiration) is the loss of a watery fluid, consisting mainly of sodium chloride and urea in solution, that is secreted by the sweat glands in the skin of mammals. ...

In insects, a system involving Malpighian tubules is utilized to excrete metabolic waste. Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the intestines. The metabolic waste is then released from the body along with fecal stuffs. Classes & Orders See taxonomy Insects are invertebrate animals of the Class Insecta, the largest and (on land) most widely-distributed taxon within the phylum Arthropoda. ... The Malpighian tubules are the insects main organ of excretion and osmoregulation, helping them to maintain water and electrolyte balance. ...

Many people misuse the term excretion as a sort of euphemism for defecation, and use excrement for feces, but this is medically improper.

See also

• Urination
• Perspiration
• Defecation
• Respiration (physiology)