urine

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Urine is a liquid product of the body that is secreted by the kidneys by 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.

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 secretion.

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.

Except in cases of kidney or urinary tract infection (UTI), urine is virtually sterile and nearly odorless. 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- 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.^[1]
• 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.
• Consumption of beets can cause urine to have a pinkish tint; the condition is harmless and temporary.
• 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.
• Reddish or brown urine may be caused by porphyria. Again, the consumption of beets can cause the urine to have a harmless, temporary pink or reddish tint.
• Greenish color is usually a consequence of consuming asparagus.
• Fluorescent yellow / greenish urine may be caused by dietary supplemental vitamins, especially the B vitamins.
• Dark yellow urine is usually indicative of dehydration.

Odor

The smell of urine can be affected by the consumption of food. Eating asparagus is known to produce a strong odour in human urine. This is due to the body's breakdown of asparagusic acid. ^[2] Other foods that contribute to odor include curry, alcohol, coffee, turkey, onion and sugar puffs.^[3][4]

Turbidity

Look up turbid in Wiktionary, the free dictionary.

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 6.5 and 7.4 In persons with hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder.^[5] Urine pH can be monitored by a physician^[6] 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 or may not 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.^[7] 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 is 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.

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.^[8]

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.^[9]

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.^[10] 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. ^[11]

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). ^[12] 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.^[11] 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,^{[13][14][15][16][17][18]} including the US Army Field Manual,^[19] 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).

Urine has also been historically used as an antiseptic.

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.^[20][21][22]

History

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

• Bed-Wetting
• Drinking urine
• Ecological sanitation
• Urination
• Urine therapy
• Urolagnia, an attraction to urine

Notes

References

External links

• Urine formation, excretion and osmoregulation.
• Urinanalysis page
• BBC News Online - US army food... just add urine
• Kelly, John F. "The Urine Cure and Other Curious Medical Treatments" Hippocrates Magazine. (May/June 1988)
• Punch and Us "A Golden Shower A Day, Keeps The Doctors Away" (Humor)
• Urine Chemistry (www.drugs.com)
• Removing urine odor
• Using Biochar for tapping the nitrogen from urine Biochar + Urine +++ for soil amendments for improving the fertility of soils and enhanced agriculture production.