Urine is the fluid excreted by the kidneys of vertebrates to clear the bloodstream of excess water and metabolic by-products including urea, uric acid, and creatinine.
In mammals, urine travels from the kidneys via the ureters to the bladder for storage until urination. Placental mammals expel urine from the bladder through the urethra, whereas other vertebrates urinate through the cloaca.
Urine plays an important role in the earth's nitrogen cycle. In balanced ecosystems, urine fertilizes the soil and thus helps plants to grow. Therefore, urine can be used as a fertilizer. Some animals mark their territories with urine.MacDonald, David W. "Patterns of scent marking with urine and faeces amongst carnivore communities." Symposia of the Zoological Society of London. Vol. 45. No. 107. 1980. Historically, aged or fermented urine (known as lant) was also used in gunpowder production, household cleaning, leather tanning, and textile dyeing.
Human urine and feces, called human waste or human excreta, are managed via sanitation systems. Livestock urine and feces also require proper management if the livestock population density is high.
Physiology
Most animals have excretory systems for elimination of soluble toxic wastes. In humans, soluble wastes are excreted primarily by the urinary system and, to a lesser extent in terms of urea, removed by perspiration. In placental mammals, the urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The system produces urine by a process of filtration, reabsorption, and tubular secretion. The kidneys extract the soluble wastes from the bloodstream, as well as excess water, sugars, and a variety of other compounds. The resulting urine contains high concentrations of urea and other substances, including toxins. Urine flows from the kidneys through the ureter, bladder, and finally the urethra before passing through the urinary meatus.
Duration Research looking at the duration of urination in a range of mammal species found that nine larger species urinated for 21 ± 13 seconds irrespective of body size. Smaller species, including rodents and bats, cannot produce steady streams of urine and instead urinate with a series of drops.
Characteristics
Quantity
The adult human bladder typically holds between 300 and (10 and ) of urine before urination, but it can hold considerably more. Average urine production in adult humans is around of urine per person per day with a normal range of per person per day, produced in around 6 to 8 urinations per day depending on state of hydration, activity level, environmental factors, weight, and the individual's health. Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License . Producing too much or too little urine needs medical attention. Polyuria is a condition of excessive production of urine (> 2.5 L/day), oliguria when < 400 mL are produced, and anuria being < 100 mL per day.
Constituents
About 91–96% of urine consists of water. The remainder can be broadly characterized into inorganic salts, urea, organic compounds, and organic ammonium salts. Urine also contains proteins, hormones, and a wide range of metabolites, varying by what is introduced into the body.
The total solids in urine are on average per day per person. Urea is the largest constituent of the solids, constituting more than 50% of the total. The daily volume and composition of urine varies per person based on the amount of physical exertion, environmental conditions, as well as water, salt, and protein intakes. In healthy persons, urine contains very little protein and an excess is suggestive of illness, as with sugar. Organic matter, in healthy persons, also is reported to be at most 1.7 times more matter than minerals. However, any more than that is suggestive of illness. + Typical design values for the concentrations of constituents in fresh urine, based on data in Sweden and Switzerland Parameter Value pH 6.2 Total nitrogen 8,830 mg/L Ammonium/ammonia-N 460 mg/L Nitrate and nitrite 0.06 mg/L Chemical oxygen demand 6,000 mg/L Total phosphorus 800–2,000 mg/L Potassium 2,740 mg/L Sulphate 1,500 mg/L Sodium 3,450 mg/L Magnesium 120 mg/L Chloride 4,970 mg/L Calcium 230 mg/L
Lesser amounts and concentrations of other compounds and ions are often present in urination of humans.
Color
Urine varies in appearance, depending principally upon a body's level of hydration, interactions with drugs, compounds and pigments or dyes found in food, or diseases. Normally, urine is a transparent solution ranging from colorless to amber, but is usually a pale yellow. Usually urination color comes primarily from the presence of urobilin. Urobilin is a final waste product resulting from the breakdown of heme from hemoglobin during the destruction of aging blood cells.
Colorless urine indicates over-hydration. Colorless urine in drug tests can suggest an attempt to avoid detection of illicit drugs in the bloodstream through over-hydration.
Bloody urine is termed hematuria, a symptom of a wide variety of medical conditions. Reddish or brown urine may be caused by porphyria (not to be confused with the harmless, temporary pink or reddish tint caused by beeturia). Pinkish urine can result from the consumption of beets (beeturia) Dark yellow urine is often indicative of dehydration. Orange urine due to certain medications such as rifampin and phenazopyridine Dark orange to brown urine can be a symptom of jaundice, rhabdomyolysis, or Gilbert's syndrome. Greenish urine can result from the consumption of asparagus or foods, beverages with green pigments, or from a urinary tract infection. Blue urine can be caused by the ingestion of methylene blue (e.g., in medications) or foods or beverages with blue dyes. Blue urine stains can be caused by blue diaper syndrome. Purple urine may be due to purple urine bag syndrome. Black or dark-colored urine is referred to as melanuria and may be caused by a melanoma or non-melanin acute intermittent porphyria.
Odor
Sometime after leaving the body, urine may acquire a strong ammonia-like odor due to bacterial decomposition of urea into ammonia. Fresh urine from healthy individuals typically has only a mild odor. Abnormally strong or unpleasant urine odor may occur in association with dehydration, diet, or urinary tract infections.
The odor of normal human urine can reflect what has been consumed or specific diseases. For example, an individual with diabetes mellitus may present a sweetened urine odor. This can be due to kidney diseases as well, such as kidney stones. Additionally, the presence of amino acids in urine (diagnosed as maple syrup urine disease) can cause it to smell of maple syrup.
Eating asparagus can cause a strong odor reminiscent of the vegetable caused by the body's breakdown of asparagusic acid. Likewise consumption of saffron, alcohol, coffee, tuna fish, and onion can result in telltale scents. Particularly spicy foods can have a similar effect, as their compounds pass through the kidneys without being fully broken down before exiting the body.Foods that Affect the Odor of Urine. livestrong.com. December 27, 2010.
pH The pH normally is within the range of 5.5 to 7 with an average of 6.2. In persons with hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder. Urine pH can be monitored by a physician or at home.
A diet which is high in protein from meat and dairy, as well as alcohol consumption can reduce urine pH, whilst potassium and organic acids, such as from diets high in fruit and vegetables, can increase the pH and make it more alkaline.
Cranberries, popularly thought to decrease the pH of urine, have actually been shown not to acidify urine. Drugs that can decrease urine pH include ammonium chloride, chlorothiazide diuretics, and methenamine mandelate.Urine pH: MedlinePlus Medical Encyclopedia . Nlm.nih.gov (2011-03-28). Retrieved on 2011-04-27.Discovery Health "Urine PH – Medical Dictionary" . Healthguide.howstuffworks.com (2007-05-16). Retrieved on 2011-04-27.
Density Human urine has a specific gravity of 1.003–1.035.
Bacteria and pathogens Urine is not sterile, not even in the bladder, contrary to longstanding popular belief. This opened a new area of study: the urinary microbiome. In the urethra, epithelial cells lining the urethra are colonized by facultatively anaerobic Gram-negative rod and cocci bacteria. One study conducted in Nigeria isolated a total of 77 distinct bacterial strains from 100 healthy children (ages 5–11) as well as 39 strains from 33 cow urine samples, a considerable amount being pathogens. Pathogens identified and their percentages were: +Bacterial isolates in human urine and cows'Humans aged 5–11 Bacterial percentage in humansBacterial percentage in cowsBacillus10.4%5.1%Staphylococcus2.6%2.6%Citrobacter 3.9%12.8%Klebsiella7.8%12.8%Escherichia coli 36.4%23.1%Proteus18.2%23.1%Pseudomonas9.1%2.6%Salmonella3.9%5.1%Shigella7.8%12.8% The study also states:
Examination for medical purposes
Many physicians in ancient history 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 ( 862 AD) mentions numerous reports of urine examination throughout the Umayyad empire.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) Diabetes mellitus got its name because the urine is plentiful and sweet. The name uroscopy refers to any visual examination of the urine, including microscopy, although it often refers to the aforementioned prescientific or Proto-scientific forms of urine examination. Clinical urine tests today duly note the color, turbidity, and odor of urine but also include urinalysis, which chemically analyzes the urine and quantifies its constituents. A culture of the urine is performed when a urinary tract infection is suspected, as bacteriuria without symptoms does not require treatment.Köves, B; Cai, T; Veeratterapillay, R; Pickard, R; Seisen, T; Lam, TB; Yuan, CY; Bruyere, F; Wagenlehner, F; Bartoletti, R; Geerlings, SE; Pilatz, A; Pradere, B; Hofmann, F; Bonkat, G; Wullt, B (25 July 2017). "Benefits and Harms of Treatment of Asymptomatic Bacteriuria: A Systematic Review and Meta-analysis by the European Association of Urology Urological Infection Guidelines Panel". European Urology. 72 (6): 865–868. PMID 28754533. 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 diuretics are consumed, in which case urine can be clear and copious and the person still be dehydrated.
Uses
Source of medications Urine contains proteins and other substances that are useful for medical therapy and are ingredients in many prescription drugs. Urine from postmenopausal women is rich in gonadotropins that can yield follicle stimulating hormone and luteinizing hormone for fertility therapy. One such commercial product is 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. Urine also contains antibodies, which can be used in diagnostic antibody tests for a range of pathogens, including HIV-1.Urine Antibody Tests: New Insights into the Dynamics of HIV-1 Infection – Urnovitz et al. 45 (9): 1602 – Clinical Chemistry . Clinchem.org. Retrieved on 2011-04-27.