urine


urine
/yoor"in/, n.
the liquid-to-semisolid waste matter excreted by the kidneys, in humans being a yellowish, slightly acid, watery fluid.
[1275-1325; ME < OF < L urina]

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Liquid solution of metabolic wastes and other, often toxic, substances filtered from plasma.

The fluid in the Bowman capsule at the start of each nephron is essentially plasma without the large molecules (e.g., proteins). The concentrated fluid (final urine) that exits the kidney consists of water, urea, inorganic salts, uric acid, creatinine, ammonia, and broken-down blood pigments, including urochrome, which makes urine yellow, plus any unusual substances not reabsorbed into the blood. This is then excreted. See also hematuria; urinalysis; urinary system; urination.

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      liquid or semisolid solution of metabolic wastes and certain other, often toxic, substances that the excretory organs withdraw from the circulatory fluids and expel from the body. The composition of urine tends to mirror the water needs of the organism. Freshwater animals usually excrete very dilute urine. Marine animals tend to combat water loss to their salty environment by excreting concentrated urine; some develop methods actively to expel salts. Terrestrial animals, depending on their habitat, usually retain water and secrete a highly concentrated urine.

      In most mammals, including humans, the formation of urine begins in the nephrons of the kidneys by filtration of blood plasma into the nephron; the fluid found within the nephron is essentially the same as blood plasma without the macromolecules (e.g., proteins). As the fluid passes along the nephron tube, water and useful plasma components such as amino acids, glucose, and other nutrients are reabsorbed into the bloodstream, leaving a concentrated solution of waste material called final, or bladder, urine. It consists of water, urea (from amino acid metabolism), inorganic salts, creatinine, ammonia, and pigmented products of blood breakdown, one of which (urochrome) gives urine its typically yellowish colour. In addition, any unusual substances for which there is no mechanism of reabsorption into the blood remain in the urine. The products of nucleic acid breakdown are present as allantoin in most mammals and as uric acid in man and, through a quirk of breeding, in the Dalmatian dog.

      In most birds, reptiles, and terrestrial insects, the end product of amino acid metabolism is not water-soluble urea but insoluble uric acid. The urine of birds and reptiles is a whitish, aqueous suspension of uric acid crystals that is passed into the cloaca and mixed with fecal material before being expelled. The urine of terrestrial insects is solid and in some cases is stored as pigment in the body rather than being expelled.

      Amphibians and fishes excrete aqueous solutions of urea; unlike those of mammals, however, their excretory organs do not reabsorb large quantities of water, so their urine remains dilute. Some marine animals retain much of the urea in the blood, thus retarding osmotic water loss.

      In small, primitive animals (teleost fishes, echinoderms, coelenterates, and single-celled animals), particularly those that live in aqueous environments, the end product of amino acid metabolism is the highly toxic gas ammonia, which is collected and expelled in a dilute aqueous solution. Many of the smaller animals develop no excretory system; each individual cell disposes of its waste products to the circulatory fluids, and the wastes then diffuse to the surrounding medium.

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Universalium. 2010.

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  • urine — [ yrin ] n. f. • XIIe var. orine; lat. pop. °aurina, d apr. aurum « or », à cause de la couleur; lat. urina ♦ Liquide organique clair et ambré, limpide, odorant, qui se forme dans le rein, séjourne dans la vessie et est évacué par l urètre… …   Encyclopédie Universelle

  • Urine — U rine, n. [F. urine, L. urina; akin to urinari to plunge under water, to dive, Gr. ? urine; cf. Skr. v[=a]r water, Icel. ?r drizzling rain, AS. w[ae]r the sea.] (Physiol.) In mammals, a fluid excretion from the kidneys; in birds and reptiles, a… …   The Collaborative International Dictionary of English

  • urine — early 14c., from O.Fr. urine (12c.), from L. urina urine, from PIE *ur (Cf. Gk. ouron urine ), variant of root *awer to moisten, flow (Cf. Skt. var water, Avestan var rain, Lith. jures sea, O.E. wær …   Etymology dictionary

  • urine — Urine, Lotium, Vrina. Quand une urine en pissant est ainsi tortuë comme celle d un porceau qui pisse, Vrina tortuosa. Urine graveleuse, pleine de gravelle. Vrina arenosa …   Thresor de la langue françoyse

  • urine — [yoor′in] n. [OFr < L urina, urine < IE * ūr , var. of base * awer , to moisten, flow > WATER, Gr ouron, urine] a waste product of vertebrates and many invertebrates, secreted by the kidneys or other excretory structures: in mammals, it… …   English World dictionary

  • Urine — U rine, v. i. To urinate. [Obs.] Bacon. [1913 Webster] …   The Collaborative International Dictionary of English

  • urine — ► NOUN ▪ a pale yellowish fluid stored in the bladder and discharged through the urethra, consisting of excess water and waste substances removed from the blood by the kidneys. ORIGIN Latin urina …   English terms dictionary

  • Urine — (from Latin Urina, ae, f.) is a typically sterile (in the absence of a disease condition)[1] liquid by product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism… …   Wikipedia

  • Urine — Un flacon d urine récolté en vue d analyses en laboratoire. L urine est un liquide organique composé des déchets de l organisme. L urine est secrétée par les reins par filtration du sang, puis par récupération des molécules de l urine… …   Wikipédia en Français

  • urine — (u ri n ) s. f. Liquide excrémentitiel sécrété par les reins, d où il coule, par les uretères, dans la vessie, qui, après l avoir conservé en dépôt pendant quelque temps, le chasse au dehors par l urèthre en se contractant. Suppression d urine.… …   Dictionnaire de la Langue Française d'Émile Littré


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