urine

Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra.

Cellular metabolism generates many by-products that are rich in nitrogen and must be cleared from the bloodstream, such as urea, uric acid, and creatinine. These by-products are expelled from the body during urination, which is the primary method for excreting water-soluble chemicals from the body. A urinalysis can detect nitrogenous wastes of the mammalian body.

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 use it to mark their territories. Historically, aged or fermented urine (known as lant) was also used for gunpowder production, household cleaning, tanning of leather and dyeing of textiles.

Human urine and feces are collectively referred to as human waste or human excreta, and 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. 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 from the body.

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

Average urine production in adult humans is around 1.4 L of urine per person per day with a normal range of 0.6 to 2.6 L 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
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. 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.Composition Of The Urine. (1872). ''The British Medical Journal'', ''1''(579), 133–133. http://www.jstor.org/stable/25231362 Urine also contains proteins, hormones, and a wide range of metabolites,Helmenstine, Anne Marie, Ph.D. (2020, August 26). What Is the Chemical Composition of Urine? Retrieved from https://www.thoughtco.com/the-chemical-composition-of-urine-603883 varying by what is introduced into the body.

The total solids in urine are on average 59 g 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 at most 1.7 times more matter than minerals. However, any more than that is suggestive of illness.

However, it is important to note that 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.

* Dark yellow urine is often indicative of dehydration.
* Yellowing may be caused by removal of excess riboflavin from the bloodstream.
* Certain medications such as rifampin and phenazopyridine can cause orange urine.
* Bloody urine is termed hematuria, a symptom of a wide variety of medical conditions.
* 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 or non-melanin acute intermittent porphyria.
* Pinkish urine can result from the consumption of beets (beeturia)
* Greenish urine can result from the consumption of asparagus or foods, beverages with green pigments, or from a urinary tract infection.
* Reddish or brown urine may be caused by porphyria (not to be confused with the harmless, temporary pink or reddish tint caused by beeturia).
* Blue urine can be caused by the ingestion of methylene blue (e.g., in medications) or foods or beverages with blue