Urine is not just a biological fluid, but also an indicator that signals any changes that occur in the body. The main body responsible for the production, excretion and composition of human urine is the kidneys. Urination or diuresis is the most important process, without which it is impossible to maintain the normal functioning of the body, because together with urine, metabolic products, salts and toxins are excreted.

For a day, in an adult, blood is cleared by the kidneys about 300 times, after which the waste is excreted through the urethra. It is considered that after filtration, 1.2 to 2 liters of liquid should be released. Its quantity and indicators are determined by a number of factors:

• climatic conditions;
• physical activity;
• age, weight;
• consumed food.

Any deviations from the norm (both up and down) are an occasion to consult a doctor for an additional examination.

In order for the tests to be reliable, it is recommended to adhere to the rules for collecting urine. The first morning portion, which is collected after a thorough washing of the external genital organs, is subject to research. A single container must be delivered to the laboratory within 2 hours, otherwise the chemical composition of the urine may change.

Physical properties of urine

The physical characteristics of urine include:

1. Density or specific gravity (determined using a urometer). When drinking water in large volumes, the amount of urine increases, respectively, its density becomes less. The norm is in the range from 1.002 to 1.040 g / ml. After heavy sweating, the density can reach the upper limit, however, if it is associated with sports training, do not worry.
2. Acidity (pH). This indicator can change its value depending on the food consumed: plant foods increase, and meat products reduce the level of alkali in the urine. The average is 5.5-7. High acidity is the first symptom of pyelonephritis, cystitis, thyroid dysfunction, or kidney failure. An acid reaction is characteristic of newborns in the first days of life.
3. Color and smell. As a rule, in healthy people, urine is painted in a moderately yellow hue and does not have a sharp odor. The density also affects color - the higher it is, the brighter the color pigment is. If the urine has a reddish tint, this is a possible sign of diseases such as glomerulonephritis or porphyria. Urine that has the color of dark beer indicates liver disease (hepatitis or jaundice). And urination with the smell of ammonia indicates an acute inflammatory process of the bladder (cystitis).

PAY ATTENTION: Eating foods such as beets or carrots, as well as taking certain medications (such as aspirin) on the eve of testing, can affect the color scheme of urine.

What is the composition of urine?

The chemical composition of the urine of a healthy person is varied and variable, in total, almost 150 different compounds of an organic and inorganic nature were found in this vital product.

The main part of the total mass is urea (normally up to 35 g / day) - the product of the breakdown of proteins in the body. Urine is also considered normal in the presence of such substances as:

• uric acid (up to 0.7 g); this compound can cause the formation of stones in the genitourinary system;
• creatinine (up to 36 mg);
• ammonia (up to 57);
• sulfates (up to 83 mg) and phosphates (up to 127 mg);
• as well as elements known in chemistry - sodium, potassium, magnesium and calcium.

Organic sludge

In the secondary urine, there may be bloody bodies, white blood cells and epithelium, which in complex form an organic sediment.

Women contain from 1 to 3 red blood cells, and their presence in men is a pronounced sign of kidney disease or the genitourinary system.

The number of white blood cells should normally not exceed 7 for men and 10 for women. An increased level of leukocytes (from 60) is accompanied by a clouding of urine, which acquires an unpleasant smell of rot and a greenish tint. If leukoceturia is bacterial in nature, this indicates a current infectious disease.

GOOD TO KNOW: When shaking the container, the urine should not foam. The formation of foam happens when there is protein or bile acid in the composition.

Pathological indicators of urine

In the composition of urine, normally, such components as protein, blood, sugar and others should be absent. They are a pathology and signal about certain violations in the body.

For example, if a certain amount of glucose (over 10 g) was detected during laboratory diagnosis, this is an indicator of glycosuria, which is a symptom of diabetes. Also, in this case, kidney, liver and pancreas diseases should not be excluded.

IT IS USEFUL TO KNOW: For reliable results of urine testing for sugar, it is collected during the day, skipping the first urination.

In acute inflammation of the genitourinary system, red blood cells (blood cells) may be present in the urine. This pathology is sometimes observed in athletes after injuries of the urinary organs.

If a lot of ketone bodies go out with urine, this means that the body uses fat reserves instead of carbohydrates to generate energy. This phenomenon can be observed with diabetes mellitus, exhausting physical training and fasting.

Cylinders or cubic particles of the epithelium, which are normally absent in human urine, also indicate inflammatory processes.

With diseases of the kidneys or heart, the patient may experience proteinuria - an increase in the amount of protein in the urine. This substance is almost always associated with impaired functioning of the body. In adults, the amount of protein should not exceed 0.033 g / l, and in infants from 30 to 50 mg. Sometimes this indicator is overestimated under the influence of elevated temperature or after physical exertion. If during repeated tests in the urine protein is found in the amount of:

• 150-500 mg / day - this indicates rotopea, acute or chronic glomerulonephritis;
• 500-2000 mg - the manifestation of post-streptococcal glomerulonephritis in the acute stage is possible;
• over 2000 mg - the patient has a nerotic syndrome.

Components such as bilirubin and urobilinogen should not be present in the analyzes. They usually stain the urine a deep yellow or brown, and indicate problems with the liver or.

So, the composition of urine, as well as its physico-chemical properties, can change under the influence of various diseases. In any case, only the doctor should establish the correct diagnosis. It is worthwhile to regularly monitor any changes in the urine - timely detect and prevent disturbances in the body.

Diuresis is the amount of urine excreted by a person for a certain time. This value in a healthy person varies widely depending on the state of water metabolism. Under normal water conditions, 1-1.5 liters of urine are excreted per day. The concentration of osmotically active substances in the urine depends on the state of water metabolism. After consuming a significant amount of water and during a functional test with a water load (the test subject drinks water in a volume of 20 ml per 1 kg of body weight), the rate of urination reaches 15-20 ml / min. Under conditions of high ambient temperature due to increased sweating, the amount of urine excreted decreases. At night during sleep, diuresis is less than during the day.

Composition and properties of urine. Most substances found in blood plasma, as well as some compounds synthesized in the kidney, can be excreted in the urine. With urine, centration in the urine is from the level of urination.

The kidneys serve as the main organ of excretion of the final products of nitrogen metabolism.

Glucose in urine is not detected under normal conditions. With excessive sugar consumption, when the concentration of glucose in the blood plasma exceeds 10 mmol / l, with hyperglycemia of a different origin, glucosuria is observed - the release of glucose in the urine.

The color of urine depends on the amount of urine output and the level of pigment excretion. Color changes from light yellow to orange. Part of the urine pigments are oxidized products of the breakdown of hemoglobin in the kidney.

Various biologically active substances and the products of their conversion are excreted in the urine, according to which to a certain extent it is possible to judge the function of some endocrine glands. Derivatives of adrenal cortex hormones, estrogens, ADH, vitamins (ascorbic acid, thiamine), enzymes (amylase, lipase, transaminase, etc.) were found in urine. With pathology in the urine, substances are found that are usually not detected in it - acetone, bile acids, hemoglobin, etc.

Urination and its regulation

Urine formed in the renal tubules is secreted into the renal calyx. Contraction of the musculature of the pelvis ensures the movement of urine into the ureter, through which urine is delivered to the bladder. The bladder is a complete organ formed by a network of smooth muscle fibers. In the area of \u200b\u200bthe base of the bubble is a triangular section formed by thin smooth muscle fibers. At the corners of the base of this triangle are the mouths of the ureters. The ureters open into the bladder in an oblique direction, and therefore, with an increase in intravesical pressure, the backflow of urine does not pass into them. In the area of \u200b\u200bthe apex of the triangle, the urethra leaves. Due to the special arrangement of muscles, a functional sphincter (contracting involuntarily) forms here. The urethra ends with the external sphincter (contracting at random), formed by the striated muscles.

Urine produced continuously in the kidneys accumulates in the bladder, which is periodically completely empty. This function, which is of great importance to humans, is mediated both by the activity of the smooth muscles of the bladder and by the effects of the autonomic and somatic nerves. There are special systems for the reflex regulation of the kidneys. Reflex urination can change with irritation of the internal organs. Blockage of one ureter with a stone inhibits urination, not only in the kidney from which the ureter departs, but also in the neighboring one.

Nervous regulation of the function of the bladder consists in the alternation of long periods of filling and short periods of emptying. With irritation of the mechanoreceptors of the bladder, impulses along the centripetal nerves enter the sacral spinal cord, in the II-IV segments of which there is a reflex urination center. The spinal center of urination is influenced by the overlying parts of the brain that change the threshold for excitation of the urination reflex. Braking effects on this reflex come from the cerebral cortex, exciting from the posterior hypothalamus and the anterior bridge. The excitation of the center of urination causes impulse in the parasympathetic fibers of the pelvic internal nerves, while the contraction of the muscles of the bladder is stimulated, the pressure in it increases to 20-60 cm of water. Art., relaxes the internal sphincter of the urethra. The flow of impulses to the external sphincter of the urethra decreases, its muscle is the only striated in the urinary tract, innervated by the somatic nerve by the branch of the reproductive nerve, and urination begins.

The bladder filling rate is approximately 50 ml per 1 hour. Due to the plasticity of the smooth muscles of the bladder, the pressure in it only slightly increases with an increase in its volume. With the accumulation of approximately 150-250 ml of urine in the bladder, the first short urge to urinate appears due to a short-term increase in intravesical pressure. The period of emptying usually begins when about 250-500 ml of urine accumulate in the bladder.

During the day, a person secretes an average of about 1.5 liters of urine, but this amount is inconsistent. For example, diuresis increases after heavy drinking, consumption of protein, the breakdown products of which stimulate urination. On the contrary, urination decreases with the consumption of a small amount of water, with increased sweating.

The intensity of urination varies during the day. During the day, more urine is formed than at night. A decrease in urination at night is associated with a decrease in body activity during sleep, with a certain drop in blood pressure. Night urine is darker and more concentrated.

Physical activity has a pronounced effect on the formation of urine. With prolonged use, diuresis decreases. This is due to the fact that with increased physical activity, blood in large quantities flows to the working muscles, as a result of which the blood supply to the kidneys decreases and the filtration of urine decreases. At the same time, physical activity is usually accompanied by increased sweating, which also helps to reduce diuresis.

Color.Urine is a clear, light yellow liquid. When settling in the urine, a precipitate is formed, which consists of salts and mucus.

Reaction.The urine reaction of a healthy person is mostly weakly acidic. Its pH ranges from 5.0 to 7.0. The reaction of urine may vary depending on the composition of the food. When mixed food (animal and plant origin) is used, human urine has a slightly acid reaction. When eating mainly meat food and other protein-rich foods, the urine reaction becomes acidic; plant-based foods contribute to the transition of urine inneutral or even alkaline.

Relative density.Urine density is on average 1.015-1.020. It depends on the amount of fluid taken.

Composition.Kidneys are the main organ for eliminating nitrogenous protein breakdown products from the body: urea, uric acid, ammonia, purine bases, creatinine, and indican.

In normal urine, protein is absent or only its traces are determined (no more than 0.03%). The appearance of protein in the urine (proteinuria) usually indicates kidney disease. However, in some cases, for example, during intense muscular work (long-distance running), protein can appear in the urine of a healthy person due to a temporary increase in the permeability of the membrane of the renal vascular glomerulus.

Among the organic compounds of non-protein origin in the urine are: salts of oxalic acid, ingested with food, especially plant; lactic acid released after muscle activity; ketone bodies formed during the conversion of fats into sugar in the body.

Glucose appears in urine only in those cases when its content in the blood is sharply increased (hyperglycemia). Excretion of sugar in the urine is called glucosuria.

The appearance of red blood cells in the urine (hematuria) is observed in diseases of the kidneys and urinary organs.

The urine of a healthy person and animals contains pigments (urobilin, urochrome), which determine its yellow color. These pigments are formed from bilirubin bile in the intestines, kidneys and secreted by them.

A large amount of inorganic salts is excreted in the urine - about 15-25 g per day. Sodium chloride, potassium chloride, sulfates and phosphates are excreted from the body. The acid reaction of urine also depends on them.

Excretion of urine.Final urine flows from the tubules into the pelvis and from it into the ureter. The movement of urine through the ureters into the bladder is carried out under the influence of gravity, as well as due to peristaltic movements of the ureters. The ureters, obliquely entering the bladder, form a kind of valve at its base, which prevents the return of urine from the bladder. Urine builds up in the bladder and is periodically excreted during urination.

In the bladder, there are so-called sphincters or pulp (ring-shaped muscle bundles). They tightly close the exit from the bladder. The first of the sphincters - the sphincter of the bladder - is located at its exit. The second sphincter - the sphincter of the urethra - is located slightly below the first and closes the urethra.

The bladder is innervated by parasympathetic (pelvic) and sympathetic nerve fibers (hypogastric). Excitation of sympathetic nerve fibers leads to increased peristalsis of the ureters, relaxation of the muscular wall of the bladder and an increase in the tone of its sphincters. Thus, stimulation of the sympathetic nerves contributes to the accumulation of urine in the bladder. With the excitation of parasympathetic fibers, the wall of the bladder contracts, the sphincters relax and urine is expelled from the bladder.

Urine continuously enters the bladder, which leads to an increase in pressure in it. An increase in pressure in the bladder to 1,177-1,471 Pa (12-15 cm of water) causes the need for urination. After urination, the pressure in the bladder drops to almost 0.

Urination is a complex reflex act, consisting in the simultaneous contraction of the bladder wall and the relaxation of its sphincters. As a result, urine is expelled from the bladder.

An increase in pressure in the bladder leads to the excitation of mechanoreceptors of this organ. Afferent impulses enter the spinal cord to the center of urination (II-V segments of the sacral region). From the center along the efferent parasympathetic (pelvic) nerves, the impulses go to the muscle of the bladder and its sphincter. There is a reflex contraction of the muscle wall and relaxation of the sphincter. At the same time, the excitation is transmitted from the center of urination to the cerebral cortex, where there is a sensation of urge to urinate. Impulses from the cerebral cortex pass through the spinal cord to the sphincter of the urethra. Urination occurs. The effect of the cerebral cortex on the reflex act of urination is manifested in its delay, amplification or even voluntary induction. In young children, there is no cortical control of urinary retention. It is produced gradually with age.

The chemical composition of urine is complex, more than 150 of its components are known. Quantitative determination of the normal components of urine - urea, uric acid, indican, sodium chloride, etc., is carried out to study kidney function or metabolic disorders according to indications. A routine clinical analysis is only intended to find out if the urine contains the most important pathological components. In a clinical analysis of urine, protein, bilirubin (bile pigment), (if it is present, acetone and acetoacetic acid), sometimes blood pigments and indican, are determined.

The presence of protein in the urine (see) is checked by quality tests, and if it is detected, its amount is determined. All high-quality protein tests are based on the appearance of turbidity during coagulation, therefore, they must be produced in well-filtered, transparent urine. Alkaline urine must be acidified. Sample with boiling: a 2/3 test tube is filled with urine, the upper part of which is heated to boiling, after which 5-8 drops of a 10% solution of acetic acid are added. In the presence of protein, the upper part of the urine becomes cloudy. Test with sulfosalicylic acid: 5-7 drops of 20% solution of sulfosalicylic acid are added to 3-5 ml of urine, in the presence of protein turbidity or flakes appear. The amount of protein is determined by the Roberts-Stolnikov method, based on a Geller test (see. Geller test). When making this test, time is noted and the appearance of a ring at the liquid boundary is observed. If it appears between the second and third minutes, the protein in the urine is 0.033 ‰, if earlier, the urine is diluted and the sample is repeated with diluted urine. They are looking for the dilution, during the test with which the ring appears between the second and third minutes. The amount of protein in the urine is equal to the result of multiplying 0.033 ‰ by the degree of dilution of urine. In addition to serumal proteins, pathological proteins are sometimes excreted in the urine, for example Bens-Jones protein (see) in case of myeloma and some leukemia.

Sugar is opened with high-quality samples and, if positive, determine its quantity. Before the study, urine is freed from the protein by boiling with acetic acid and subsequent. The simplest high-quality sample of Gaines: 1 drop of urine is added to 9 drops of Gaines reagent and boiled for 1 minute. In the presence of sugar, a brownish-green, yellow or brick precipitate forms. Gaines Reagent: 13.3 g of chemically pure copper sulfate are dissolved in 400 ml of water, 50 g of dissolved in 400 ml of water, 15 ml of pure glycerol is diluted in 200 ml of water. The first and second solutions are mixed and the third is immediately added. The amount of sugar is determined using a polarimeter. With urine, dextrorotatory glucose is detected, with left rotation; at pregnant and nursing mothers is observed (see). The amount of sugar can also be determined by the Althausen method. 1 ml of a 10% solution of caustic is added to 4 ml of urine and boiled for 1 min. 10 minutes later determine what color on the Althausen color scale corresponds to the color of urine. In the absence of a printed color scale, it is prepared in test tubes. Harvested 0.5; 1; 1.5; 2; 3 and 4% glucose solutions. They are treated at the same time and in the same way with the studied urine.

Test for acetone bodies. Reagent: 6 g of nitroprusside sodium are dissolved in 100 ml of a 30% solution of acetic acid. To 5-6 ml of urine, the reagent is added dropwise to the color and ammonia is layered. In the presence of acetone bodies, a violet ring forms at the liquid boundary.

Bilirubin is absent in normal urine, it appears at jaundice (see. Bilirubinuria). A breakdown of Gmelin is revealed (see. Gmelin test), Rosina. Rosin's test: Lugolevsky or a weak alcoholic solution of iodine is layered on the urine; a green ring forms at the fluid boundary.

Urobilin is detected by Bogomolov's breakdown: 10-15 drops of 10% copper sulfate solution and 2-3 drops are added to 10 ml of urine. In 3-5 minutes pour 2 ml of chloroform and, having closed with a stopper, repeatedly overturn a test tube. With an increased content of urobilin, it turns pink.

A benzidine breakdown is detected (see): on a mixture of a benzidine solution poured into a test tube and (1-2 ml) layered urine; in the presence of hemoglobin, a blue or green color appears at the fluid boundary.

Indikan reveal breakdown of Jaffe. An equal amount of strong hydrochloric acid, 1 drop of a 1% solution (or 2 drops of a 10% solution of ferric chloride) and 2 ml of chloroform are added to 3-4 ml of urine. Shake vigorously. In the presence of indican, chloroform, settling to the bottom, acquires a blue color.

The composition of urine is very diverse, it directly depends on the consumption and production of various substances, the state of the body as a whole, and the function of the urinary tract. The main inorganic composition is represented by chemical components and nitrogen-containing compounds.

General information

Water and water-soluble substances are excreted from the body with urine. The volume of urine and its composition depends on the composition of the diet, body weight, age, gender, physical activity and conditions such as, for example, humidity and temperature. An adult daily produces from 0.5 to 2 liters of urine, of which about 95% are water. The body of an average healthy person removes 1.5 liters of urine per day. In addition to water, it contains many other substances. The chemical composition of urine includes the following components:

• urea,
• creatinine
• creatine
• ammonia,
• urata
• amino acids.

Proteins get into urine with a high load of pathological proteins on the glomeruli (for example, in the case of paraproteinemia), with a violation of the glomeruli membrane, with diseases of the tubules of the kidneys and urinary tract. Carbohydrates in the urine are present freely, in the form of glycoproteins, mucopolysaccharides and glycopeptides.

From lipids, fatty acids, triglycerides, phospholipids and cholesterol may be present; lipid excretion increases with nephrotic syndrome.

Organic components

The most important physiological components are represented by organic nitrogen-containing compounds. These include the following substances:

1. Urea (urea) is synthesized in the liver in the urea NH3 cycle, which comes from the degradation of amino acids. The secreted volume of urea depends on the amount of protein metabolized, for example, due to degradation of 70 g of protein, 30 g of urea is formed per day.
2. Uric acid is the final product of purine catabolism. In the proximal tubules of the kidneys, almost all filtered uric acid is absorbed, returns to urine again through active tubular secretion, and subsequently part of it is again actively resorbed. These actions in the distal tubules may depend on a number of anions and drugs (competes with uric acid for transport). Only 6-12% of filtered uric acid is finally excreted in the urine.
3. Creatinine is a product of muscle metabolism, spontaneously and irreversibly formed from creatine. When passing through the kidneys, creatinine in most (90%) of the volume is filtered into ultrafiltrate, and only 10% of it is secreted into the canaliculi of the urine and, as a rule, is resorbed. The amount of creatinine released per day is individual and depends directly on the weight of muscle mass and the function of individual glomeruli - thus, it can be used as a reference for the quantitative determination of other components.

The amount of secreted amino acids to a large extent depends on the quality of nutrition and liver performance. Modified amino acids that are present in proteins with specialized functions, such as hydroxyproline and 3-methylhistidine, can serve as indicators of the degradation of these proteins.

Some metabolites can be conjugated to H2SO4 → sulfates, glycine and other polar compounds. These conjugates are synthesized in a biotransformation reaction in the liver, and are excreted in the urine as water-soluble compounds.

Other components

Hormone metabolites (catecholamines, steroids, serotonin) also appear in the urine. An analysis of the content of metabolites of these hormones can provide information on the production of these hormones, for example, the determination of vanillyl mindic acid, 5-hydroxyindole, etc.

Another example is the human chorionic gonadotropin (hCG, Mr \u003d 36000). HCG is a proteogormone that is produced in the early stages of pregnancy; it circulates in the blood and, because it has a small molecule, is also present in the urine. Immunological detection of hCG in urine is the basis for most pregnancy tests.

Part of the urine is also a small amount of urobilinogen, which is produced in the intestines from bilirubin. Due to the oxidation of urobilinogen, urobilin (bile pigment) is formed.

Pathological indicators

Abnormal amounts of protein (particularly albumin) indicate proteinuria (i.e., greater than 0.15 g / 24 hours). Proteinuria is one of the symptoms of kidney disease, which indicates damage to the glomeruli (glomeruli). Damage can be caused by mechanical or foreign substances or organisms (toxins, bacterial infections).

Glucosuria is a term expressed by the occurrence of glucose (Glc) in the urine. Glc is filtered in primary urine at any level of glucose in the blood (even if hypoglycemia is present). Reverse absorption increases with an increase in glucose, but only to certain values \u200b\u200b(blood glucose is about 10 mmol / l). Above this “renal border”, resorption does not increase already, because all receptor proteins for Glc are already occupied. The presence of Glc (glucosuria) increases diuresis (for example, in diabetes mellitus).

The term ketonuria refers to a condition in which ketone bodies appear in the urine (acetoacetic acid is detected). Elevated ketone values \u200b\u200boccur when fatty acids are degraded excessively (for example, during fasting or diabetes).

Inorganic components and urinary sediment

Human urine contains a significant amount of cations: Na +, K +, Ca2 +, Mg2 +, NH4 + and anions: Cl-, SO4-2, HCO3- and HPO4-2 and trace amounts of other ions. The secretion of ions in most cases is regulated by hormones. A number of different inorganic components are determined by the nutritional composition.

Reabsorption of the above ions occurs in the tubular part of the nephron. The proximal tubules are the site of absorption of most ions (Na +, K +, Cl-, HCO3, etc.). Buffer systems are phosphates and ammonia.

Urinary sediment is a term referring to microscopic examination of urine. This is a standard examination carried out simultaneously with chemical research. To study the sediment, urine is used no more than 2 hours after collection (after this time, the elements disintegrate). The sediment is assessed for the presence of blood and epithelial cells, bacteria; in addition, the presence and quantity of various crystals is determined - their presence is mainly associated with insufficient hydration.

The composition of the urinary sediment can be of organic and inorganic origin. The organic part consists of cells having 2 sources:

• blood cells
• cells of the kidney itself or excretory urinary tract.

In the urine, almost all blood cells can be present: eosinophils, red blood cells, neutrophils, macrophages and lymphocytes (rarely). Renal cells in sediment are exfoliated epithelial cells that line the urinary tract (tubular, transitional, and squamous epithelium). The urinary sediment may contain various other cells: trichomonads, yeast, intestinal epithelial cells, or tumor cells.

Formations known as cylinders may be present in the sediment. They are formed from glycoprotein, which protects the surface of the tubule. Glycoprotein can bind epithelial cells, white blood cells, red blood cells, and bacteria. Cylinders found in urinary sediment always mean serious kidney damage.

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Elements of inorganic origin are represented by salt crystals, for example, oxalates, urates, phosphates. They have pathological significance if they are found in people who are currently or previously treating urolithiasis. The second group of crystals are crystals of small amino acids - cystine, leucine, tyrosine.

Thus, the composition of urine contains organic and inorganic compounds, blood cells and other elements.