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Urine is a liquid product of the body that is secreted by the kidneys by a process called urination and excreted through the urethra. Cellular metabolism generates numerous waste compounds, many rich in nitrogen, that require elimination from the bloodstream. This waste is eventually expelled from the body in a process known as micturition, the primary method for excreting water-soluble chemicals from the body. These chemicals can be detected and analyzed by urinalysis. Amniotic fluid is closely related to urine, and can be analyzed by amniocentesis.

Sample of human urine.

Contents

Physiology

To eliminate soluble wastes, which are toxic, most animals have excretory systems. In humans soluble wastes are excreted by way of the urinary system, which consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys extract the soluble wastes from the bloodstream, as well as excess water, sugars, and a variety of other compounds. Remaining fluid contains high concentrations of urea and other substances, including toxins. Urine flows through these structures: the kidney, ureter, bladder, and finally the urethra. Urine is produced by a process of filtration, reabsorption, and tubular section.

Composition

Urine is a transparent solution that can range from colorless to amber but is usually a pale yellow. Urine is an aqueous solution of approximately 95% water, with the remaining percentages being metabolic wastes such as urea, dissolved salts, and organic compounds. Fluid and materials being filtered by the kidneys, destined to become urine, come from the blood or interstitial fluid.

Urine is sterile until it reaches the urethra where the epithelial cells lining the urethra are colonized by facultatively aerobic Gram negative rods and cocci [1]. Subsequent to elimination from the body, urine can acquire strong odors due to bacterial action. Most noticeably, the asphyxiating ammonia is produced by breakdown of urea. Some diseases alter the quantity and consistency of the urine, such as sugar as a consequence of diabetes.

Hazards

Urea is toxic and can be irritating to skin and eyes. High concentrations in the blood can cause damage to organs of the body. However, after suitable processing (as is done, for example, on the International Space Station), it is possible to extract potable water for drinking.

Characteristics

The typical color can range from clear to a dark amber, depending mostly upon the level of hydration of the body, among other factors.

Chemical analysis

Urea structure

Urine contains a range of substances that vary with what is introduced into the body. Aside from water, urine contains an assortment of inorganic salts and organic compounds, including proteins, hormones, and a wide range of metabolites.

Unusual color

  • Colorless urine indicates over-hydration, which is usually considered much healthier than dehydration. In the context of a drug test, it could indicate a potential attempt to avoid detection of illicit drugs in the bloodstream through over-hydration.[2]
  • Dark yellow urine is often indicative of dehydration.
  • Yellowing/light orange may be caused by removal of excess B vitamins from the bloodstream.
  • Certain medications such as rifampin and pyridium can cause orange urine.
  • Bloody urine is termed hematuria, potentially a sign of a bladder infection.
  • Dark orange to brown urine can be a symptom of jaundice, rhabdomyolysis, or Gilbert's syndrome.
  • Black or dark-colored urine is referred to as melanuria and may be caused by a melanoma.
  • Fluorescent yellow / greenish urine may be caused by dietary supplemental vitamins, especially the B vitamins.
  • Consumption of beets can cause urine to have a pinkish tint, and asparagus consumption can turn urine greenish.
  • Reddish or brown urine may be caused by porphyria. Although again, the consumption of beets can cause the urine to have a harmless, temporary pink or reddish tint.

Odor

The smell of urine can be affected by the consumption of food. Eating asparagus is known to cause a strong odor in human urine. This is due to the body's breakdown of asparagusic acid.[3] Other foods (and beverages) that contribute to odor include curry, alcohol, coffee, turkey, cheese cake, and onion.[4][5]

Turbidity

Turbid urine may be a symptom of a bacterial infection, but can also be due to crystallization of salts such as calcium phosphate.

pH

The pH of urine is close to neutral (7) but can normally vary between 4.4 and 8. In persons with hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder.[6] Urine pH can be monitored by a physician[7] or at home.

Volume

The amount of urine produced depends on numerous factors including state of hydration, activities, environmental factors, size, and health. In adult humans the average production is about 1 - 2 L per day. Producing too much or too little urine needs medical attention: Polyuria is a condition of excessive production of urine (> 2.5 L/day), in contrast to oliguria where < 400 mL are produced per day, or anuria with a production of < 100 mL per day.

Density or specific gravity

Normal urine density or specific gravity values vary between 1.003–1.035 (g·cm−3) , and any deviations may be associated with urinary disorders.

Urine in medicine

A Doctor Examining Urine. Trophime Bigot.

Examination

Many physicians in history have resorted to the inspection and examination of the urine of their patients. Hermogenes wrote about the color and other attributes of urine as indicators of certain diseases. Abdul Malik Ibn Habib of Andalusia d.862CE, mentions numerous reports of urine examination throughout the Umayyad empire.[8] Diabetes mellitus got its name because the urine is plentiful and sweet. A urinalysis is a medical examination of the urine and part of routine examinations. A culture of the urine is performed when a urinary tract infection is suspected. A microscopic examination of the urine may be helpful to identify organic or inorganic substrates and help in the diagnosis.

The color and volume of urine can be reliable indicators of hydration level. Clear and copious urine is generally a sign of adequate hydration, dark urine is a sign of dehydration. The exception occurs when alcohol, caffeine, or other diuretics are consumed, in which case urine can be clear and copious and the person still be dehydrated.

Application

Aztec physicians used urine to clean external wounds to prevent infection, and administered it as a drink to relieve stomach and intestinal problems.[citation needed]

Resource

Urine contains proteins and other substances that are useful for medical therapy and are ingredients in many prescription drugs (e.g., Ureacin, Urecholine, Urowave). Urine from postmenopausal women is rich in gonadotropins that can yield follicle stimulating hormone and luteinizing hormone for fertility therapy. The first such commercial product was Pergonal. Urine from pregnant women contains enough human chorionic gonadotropins for commercial extraction and purification to produce hCG medication. Pregnant mare urine is the source of estrogens, namely Premarin.

Other uses

Munitions

Urine has been used in the manufacture of gunpowder. Urine, a nitrogen source, was used to moisten straw or other organic material, which was kept moist and allowed to rot for several months to over a year. The resulting salts were washed from the heap with water, which was evaporated to allow collection of crude saltpeter crystals, that were usually refined before being used in making gunpowder.[9]

Textiles

Urine has often been used as a mordant to help prepare textiles, especially wool, for dyeing. In Scotland, the process of "walking" (stretching) the tweed is preceded by soaking in urine.[10]

Agriculture

Urine contains large quantities of nitrogen (mostly as urea), as well as significant quantities of dissolved phosphates and potassium, the main macronutrients required by plants. Diluted at least 8:1 with water it can be applied directly to soil as a fertilizer. Undiluted, it can chemically burn the roots of some plants, but it can be safely used as a source of complementary nitrogen in carbon rich compost.[11] Urine typically contains 70% of the nitrogen and more than half the phosphorus and potassium found in urban waste water flows, while making up less than 1% of the overall volume. Thus source separation and on-site treatment has been studied in Sweden as a way to partially close the cycle of agricultural nutrient flows, to reduce the cost and energy intensivity of sewage treatment, and the ecological consequences such as eutrophication, resulting from an influx of nutrient rich effluent into aquatic or marine ecosystems. The fertilization effect of urine has been found to be comparable to that of commercial fertilizers with an equivalent NPK rating. [12]

However, depending on the diet of the producer, urine may also have undesirably high concentrations of various inorganic salts such as sodium chloride, which are also excreted by the renal system. Concentrations of heavy metals such as lead, mercury, and cadmium, commonly found in solid human waste, are much lower in urine (though not low enough to qualify for use in organic agriculture under current EU rules).[13] Proponents of urine as an agricultural fertilizer usually claim the risks to be negligible or acceptable, and point out that sewage causes more environmental problems when it is treated and disposed of compared with when it is used as a resource.

It is unclear whether source separation and on site treatment of urine can be made cost effective, and to what degree the required behavioral changes would be regarded as socially acceptable, as the largely successful trials performed in Sweden may not readily generalize to other industrialized societies.[12] In developing countries, the application of pure urine to crops is rare, but the use of whole raw sewage (termed night soil) has been common throughout history.

Survival uses

Numerous survival instructors and guides,[14][15][16][17][18][19] including the US Army Field Manual,[20] advise against drinking urine for survival. These guides explain that drinking urine tends to worsen, rather than relieve dehydration due to the salts in it, and that urine should not be consumed in a survival situation, even when there is no other fluid available.

During World War I, the Germans experimented with numerous poisonous gases for use during war. After the first German chlorine gas attacks, Allied troops were supplied with masks of cotton pads that had been soaked in urine. It was believed that the ammonia in the pad neutralized the chlorine. These pads were held over the face until the soldiers could escape from the poisonous fumes, although it is now known that chlorine gas reacts with urine to produce toxic fumes (see chlorine and Use of poison gas in World War I).[citation needed]

Urine has also been historically used as an antiseptic.[citation needed]

Urban myth states that urine works well against jellyfish stings, and this scenario was demonstrated on an early episode of the CBS-TV show Survivor. At best, it is ineffective and in some cases this treatment may make the injury worse.[21][22][23]

History

Ancient Romans used human urine to cleanse grease stains from their clothing, before acquiring soaps from the Germans during the first century CE.[24].

Alchemists spent much time trying to extract gold from urine, and this effort led to discoveries such as white phosphorus, which was discovered by the German alchemist Hennig Brand in 1669 when he was distilling fermented urine. In 1773 the French chemist Hilaire Rouelle discovered the organic compound urea by boiling urine dry.

The word "urine" was first used in the 14th century. Before that, the concept was described by the now vulgar word "piss". Onomatopoetic in origins, "piss" was the primary means of describing urination, as "urinate" was at first used mostly in medical contexts. Likely, "piss" became vulgar through its use by lower class characters such as the reeve and the Wife of Bath in Geoffrey Chaucer's 14th century work The Canterbury Tales. "Piss" and its association with vulgarity has led to its current classification as obscene, as well as its use in such colloquial expressions as "to piss off", "piss poor", and others.

See also

Notes

  1. ^ Brock: Biology of microorganisms
  2. ^ Neonjoint.com
  3. ^ Lison M, Blondheim SH, Melmed RN. (1980). "A polymorphism of the ability to smell urinary metabolites of asparagus". Br Med J 281: 1676. PMID 7448566. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=7448566. 
  4. ^ Stefan Gates and Max La Riviere-Hedrick. Gastronaut: Adventures in Food for the Romantic, the Foolhardy, and the Brave. Page 87. 2006.
  5. ^ "All the Problems in the World." The Independent on Sunday. April 15, 2007.
  6. ^ Martín Hernández E, Aparicio López C, Alvarez Calatayud G, García Herrera MA (September 2001). "[Vesical uric acid lithiasis in a child with renal hypouricemia"] (in Spanish; Castilian). An. Esp. Pediatr. 55 (3): 273–6. PMID 11676906. http://db.doyma.es/cgi-bin/wdbcgi.exe/doyma/mrevista.pubmed_full?inctrl=05ZI0103&rev=37&vol=55&num=3&pag=273. 
  7. ^ "Urine pH". MedlinePlus Medical Encyclopedia. http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/003583.htm. Retrieved December 26, 2008. 
  8. ^ Ibn Habib, Abdul Malik d.862CE/283AH "Kitaab Tib Al'Arab" (The Book of Arabian Medicine), Published by Dar Ibn Hazm, Beirut, Lebanon 2007(Arabic)
  9. ^ Joseph LeConte (1862). Instructions for the Manufacture of Saltpeter. Columbia, S.C.: South Carolina Military Department. pp. 14. http://docsouth.unc.edu/imls/lecontesalt/leconte.html. Retrieved 2007-10-19. 
  10. ^ Mentioned by an interviewee in Lomax the Songhunter, a 2004 documentary film.
  11. ^ Steinfeld, Carol (2004). Liquid Gold: The Lore and Logic of Using Urine to Grow Plants. Ecowaters Books. ISBN 978-0966678314. http://www.liquidgoldbook.com/. 
  12. ^ a b "Urine Separation -- Closing the Nitrogen Cycle" (PDF). Stockholm Water Company. 2001. http://www.stockholmvatten.se/pdf_arkiv/english/urinsep_eng.pdf. 
  13. ^ Håkan Jönsson (2001-10-01). "Urine Separation — Swedish Experiences". EcoEng Newsletter 1. http://www.iees.ch/EcoEng011/EcoEng011_F1.html. 
  14. ^ water
  15. ^ Tracker Trail - Mother Earth News - Issue #72
  16. ^ Equipped to Survive (tm) - A Survival Primer
  17. ^ Five Basic Survival Skills in the Wilderness
  18. ^ Survival Gear
  19. ^ Wilderness Survival: Sea Survival - The Open Sea
  20. ^ Water Procurement, US Army Field Manual
  21. ^ ABC News: Old Wives' Tale? Urine as Jellyfish Sting Remedy
  22. ^ Fact or Fiction?: Urinating on a Jellyfish Sting is an Effective Treatment: Scientific American
  23. ^ Jellyfish Sting Treatment - How to Treat a Jellyfish Sting
  24. ^ "Hygiene in Ancient Rome". http://ancienthistory.about.com/library/weekly/aa031303a.htm. Retrieved 2010-02-09. 

References

External links


Simple English

Urine is liquid created by the body in the kidneys. It is stored in the bladder and comes out of the human body through the urethra, a tube which leads from the bladder to the urethral meatus (meatus = an opening in the body), located at the tip of the penis (Men) or the vulva (Women). Urinating is how the body gets rid of unwanted or unneeded substances in the blood. Urine is the liquid that these substances are put in. After the blood has circulated through the body, its composition has changed, because some substances in the blood have been absorbed by the body, and because the body has released other substances into the blood. The blood has also absorbed substances produced from our food. The liver removes many toxins (harmful substances) and adds other substances that the blood needs (amino acids, proteins, coagulation factors, hormones, etc). Then the kidneys remove excess amounts of urea, salts, etc) by putting them into the urine. After the blood has passed through the liver and the kidneys, it has the correct composition that the body needs.

Urine is mostly water, and contains mineral salts, and about 2% urea, which is produced in the liver to remove ammonia, which is a very toxic substance. Urea has a very low toxicity, although a continuous high level of urea in the blood (a condition called hyperuremia) can cause disease.

The color of urine normally ranges from colourless to yellow. The yellow color is caused by urobilins, which are produced by the breakdown of hemoglobin, the substance that gives blood its red color. If a person is dehydrated, less urine will be produced (maybe less than 1 liter per day), and it will be more concentrated. If a person drinks a lot of water, more urine will be produced (maybe as much as 2 liters per day) and it will be less concentrated. [[File:|thumb|right|170px|Urine.]] Urine lets the body get rid of:

  1. Extra water
  2. Extra electrolytes (salts)
  3. Urea (mostly not needed by the body)
  4. Drugs
  5. Toxins (poisons in the body)( Note that toxins are generally removed by the liver, which transfers the toxins to the feces. Many descriptions of urine say that some toxins are removed in urine, but do not say what toxins these are).

Urine leaves the kidneys and is stored in the bladder. Urine leaves the body through the urethra.

Some slang terms for urine are "pee" and "piss".








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