Primary urine composition. The process of urine formation. The influence of the concentration of substances circulating in the blood on the degree of filtration in the kidneys

The presence of a human genitourinary system makes it possible to quickly remove waste products from the body that were formed during previously occurring processes. Urine formation is a vital process carried out by the kidneys and occurs in three main stages: filtration, reabsorption and secretion. Violations in the formation and excretion of urine can lead to certain types of quite serious diseases. In this case, the examined primary and secondary urine, or rather the result of the analysis, will immediately show the occurrence of certain disorders, which will be a good reason for further examination and treatment.

Primary urine is the liquid that is formed in the kidneys after filtering substances of low molecular weight present in the blood from formed elements and proteins. By the name of the elements included in primary urine, it can be compared with blood plasma, in which amino acids, creatinine, glucose, urea, low molecular weight complexes and free ions are also present in exact quantities. After the formation of primary urine and its passage through the tubules through the cells of their walls, a large amount of water goes back into the blood, as well as those substances that the body needs for normal functioning. This entire process of passage and return of the contents of primary urine is called reabsorption.

During the process of reabsorption, some substances are completely absorbed by the body. Such substances are glucose and various amino acids. Mineral salts and water are “taken” by human blood. All that remains after this whole process is called secondary urine. That is, it is it that is submitted for analysis in the laboratory and its composition and other parameters are examined.

Composition of secondary urine

The main components of secondary urine are:

• water,
• urea,
• ammonia,
• various sulfates,
• chlorine,
• sodium.

The total volume of secondary urine, which includes all of the above components, exceeds one liter per day. It can be larger if a person consumes a much larger amount of water than his body requires, and smaller if the ambient temperature is high enough. The usual color of urine is yellow, due to the presence of bile pigments, part of which, being absorbed in the intestines, goes into the blood and is filtered by the kidneys, but is not reabsorbed. The frequency of urine excretion from the body is determined by volume.

The need to analyze the composition of secondary urine

The composition of secondary urine is examined to determine the presence of certain diseases in the human body. In this case, it is possible to quickly diagnose problems in the functioning of organs such as the bladder, kidneys and prostate. In addition, urine is analyzed when there is a suspicion of urolithiasis and nephrosclerosis.

Collection of material for research

In order to achieve reliable results, correct urine collection is a very important condition. In order to pass the test correctly, you must first perform hygiene procedures for the genital organs. Secondary urine should be collected in a sterile, dry container and tightly closed with a lid. All this is explained by the fact that the concentration of substances in the research material can change under the influence of external factors, as well as the presence of water and detergents in the container. In order to avoid this, there are now special containers, the use of which will help minimize the likelihood of obtaining unreliable results.

Features of collecting material for research in children

Children, especially under the age of one and a half years, cannot control the desire to urinate, which causes certain problems with collecting material. But in most cases, this analysis is mandatory and is taken quite often. That is why secondary urine from children is collected in a special way using special urinals. These elements are attached to the genitals, which have been thoroughly washed in advance, and are detached from them after urine is inside it. The resulting liquid is poured into a sterile container.

Thus, the formation of secondary urine is a fairly important process, which allows not only to remove excess water and unnecessary substances and elements from the body, but also to diagnose a particular disease in time. This test is one of the simplest for both the patient and laboratory technicians, so there are no restrictions on its performance. But in order to obtain a reliable result, it is necessary to fulfill a number of requirements when taking this analysis. Compliance with all the rules will accurately indicate the presence of violations and make a decision on the need for treatment.

Urine is a fluid produced by the kidneys that is excreted from the body through the genitourinary system as excrement. It is the result of renal filtration of the blood flow (aimed at removing metabolic end products from the body), making up to 30 full revolutions per day. Before being excreted through the urinary organs, it goes through two stages of formation:

• Formation of primary urine

What is primary urine?

It is formed as a result ultrafiltration– the process of purifying blood plasma from proteins and low molecular weight colloidal particles. Filtration occurs in the nephrons, the structural and functional unit of the kidneys, when the liquid portion of the blood flow passes through a capillary branch in the Malpegiian corpuscle.

The process occurs without a specific selective algorithm, moving waste with substances necessary for life. Length of tubules of one nephron about 50 mm. Their total length is up to 100 km. About 100 ml of liquid is filtered within a minute, up to 180 liters per day.

Composition of primary urine

99% is water. This filtrate has a similar chemical composition to blood plasma, except that it contains minimal amounts of protein molecules such as hemoglobin and albumin. The percentage of amino acids, glucose, and free ions corresponds to the same indicator in the blood.

Stages and mechanism of education

The filtration phase in the renal corpuscle is due to the functioning of the cardiovascular system, which maintains stable blood pressure in the kidneys even when it changes twice in the body itself. It is expressed in the leakage of the liquid part of the blood through the walls of the blood vessels into the capsule of the renal corpuscle.

This process is ensured by the difference in blood pressure in the afferent vessels and the cavity itself Shumlyansky-Bowman capsules. In the first case it is 70-90 mmHg, in the second - 10-15 mmHg. It is not controlled by the human brain, but is performed passively. When the pressure in the capillaries drops to 30 mm, the filtration process stops. The pores of the capillary walls are minimal in size, so all large protein molecules and blood cells (erythrocytes, leukocytes, platelets) are retained in the blood.

What is secondary urine?

98-99% is water. It is formed as a result of the reabsorption of many substances from primary urine (passed into the renal tubules) into the blood stream circulating in the networks of capillaries surrounding these tubules - proximal and distal. The proximal tubule is lined with a huge number of villi, providing forty times the reabsorption of water and salts, compared with the usual ability to filter through the walls of the capillaries.

Thanks to reabsorption, beneficial substances necessary for the body are returned to the blood. The daily volume of liquid received fluctuates around 1.5 liters. Return transportation ensures the return of 80% of the necessary substances, including amino acids and vitamins.

Composition of secondary urine

The chemical composition differs greatly from the primary one, predominating in the content of large amounts of urea, guppyric acid, creatinine, sulfates, and chlorine. It exceeds primary urine in concentration.

Stages and mechanism of education

Reabsorption includes the obligatory reverse transport of protein and glucose molecules (requiring a significant expenditure of chemical energy in the cellular layer of the proximal tubule), as well as the passive absorption of salts and water (due to osmotic pressure and diffusion).

The functions of the proximal tubule also include the production of acids and alkalis to maintain the acid-base balance of the blood. These processes of synthesis and secretion are caused by the activity of the epithelium of the renal tubules, for the maintenance of which the kidneys consume six times more oxygen than muscle tissue (based on the ratio of their masses). The resulting fluid is urine, passed through the ureters into the bladder for eventual removal from the body.

Regulating the physical and chemical composition of urine

1. Due to the extensive system of sympathetic and parasympathetic nerve endings, which helps to reduce or increase blood flow in the kidneys. The role of osmoreceptors, irritated by changes in the level of osmotic pressure due to an increase or decrease in the amount of salts in the blood, is also expressed. Such regulation has a greater impact on filtration;
2. Humoral regulation, which has a greater impact on reabsorption. Depending on the predominance of certain elements in the blood flow, certain hormones are released, narrowing the lumens and crevices in the epithelium, therefore increasing (or decreasing) the reabsorption of water, sodium and potassium ions.
3. Secretion (transport of elements from the blood) of hydrogen and potassium ions, organic acids, penicillin, which serves as a response to a sharp increase in these elements in the blood.

The influence of the concentration of substances circulating in the blood on the degree of filtration in the kidneys

1. Threshold- amino acids, vitamins, various ions, glucose. They are not eliminated along with the urine until their quantity exceeds a certain level in the blood plasma. Presence of pain.
2. Non-threshold- urea, sulfates. They are released during ultrafiltration into primary urine (regardless of their quantity), without being reabsorbed.

The detection of an excess of threshold substances in secondary urine tests may indicate a violation of the reabsorption mechanism, or may signal a disruption in the functioning of the body.

The presence of a genitourinary system in a person allows metabolic products to be removed from the body without problems. In fact, the process of urine formation is quite complex and includes several stages.

You can often hear the term secondary urine - this is a liquid that contains urea, chlorine, sodium, potassium, sulfates and ammonia. Urine examination is considered one of the informative research methods with which it is possible to diagnose various diseases in the human body.

In fact, urine itself is a liquid that is excreted by the kidneys through a process of filtration and secretion. Initially, such fluid first enters the ureter, and only then from the bladder into the urethra.

• age

Primary urine is formed when blood passes through the capillaries through the filtration process, and its constituent element is water, which is gradually absorbed into the channels. The human body contains about several liters of primary urine, which re-enters the body through the same channels.

The remainder of this fluid is converted into secondary urine, which is usually used for analysis.

The constituent elements of secondary urine are:

• water
• ammonia
• sulfates
• sodium
• chlorine

The human body contains no more than a liter of secondary urine, consisting of liquid that the body has not absorbed during absorption. In fact, primary urine includes useful elements and is absorbed by the body. Secondary urine contains acids and urea, which are not absorbed by the human body. Urinalysis is used when it is necessary to diagnose pathologies of such organs as:

• kidneys
• bladder

Often a urine test is prescribed when there is a suspicion of progression in the body:

• nephrosclerosis
• urolithiasis

Carrying out the simplest allows you to timely diagnose dangerous pathologies of the genitourinary system and prescribe effective treatment.

Diagnostics

In order for the results of a urine test to be reliable, you need to properly prepare

The main condition for obtaining accurate and reliable research results is purity. The concentration of substances in the collected material may change under the influence of excess liquid and detergent residues located on the walls of the container. If it is necessary to collect urine for research in childhood, you can use special urinals, but in no case a potty or a diaper.

A prerequisite for collecting urine is maintaining genital hygiene. The optimal material for research is considered to be morning urine, and the last urination should be no later than 4-6 hours before.

1. It is necessary to consume the usual amount of fluid, since its excess can cause changes in its density
2. the day before the test, you should stop drinking alcoholic beverages and those foods that can cause a change in the color of urine
3. Before the study, you must stop taking medications, herbal remedies and herbal preparations

If the patient is being treated with certain medications, the laboratory technician must be notified about this.

Useful video - How urine is formed in the human body:

After carrying out hygienic procedures for the genital organs, the patient must perform the following steps:

1. you need to flush the first small portion of urine down the toilet, because at this time dead cells are washed out of the urethra
2. the required amount of urine is collected into the prepared container, and the final portion of liquid is flushed into the toilet
3. The container containing urine should be tightly closed and taken to the laboratory.

It is allowed to store the collected material for no more than 1-1.5 hours, because after this time the active process of reproduction of microorganisms begins and the pH changes.

Decoding the analysis results

Experts say something bad if there are any deviations from the norm. In most cases, this indicates the development of various diseases in the body that require treatment.

What indicators of secondary urine does a specialist pay attention to:

• In a healthy person, urine is light yellow. A darker color of the secreted fluid may indicate a malfunction of the hematopoietic system, and the red color is a symptom of pyelonephritis, urolithiasis, etc. Urine the color of meat slop can signal the progression of kidney tuberculosis and glomerulonephritis in the human body.
• Urine should be clear, and if it becomes cloudy and flakes appear, an inflammatory process in the kidneys and urinary system can be suspected. Often this pathological condition is diagnosed with pyelonephritis, cystitis and amyloidosis.
• Normal urine acidity is 4-7, and its increase may be a sign of dehydration, acidosis and diabetes. A decrease in indicators can be observed with bladder cancer,

Urine formation occurs in the kidneys, or more precisely in the minimal structural unit of the kidney - the nephron. The nephron consists of a glomerulus and a renal tubule. The glomerulus is formed by a bundle of capillaries, which are branches of the afferent and efferent arterioles. The capillaries are surrounded by Bowman's capsule, formed by tubular epithelium. From it begin the convoluted sections of the renal tubules, turning into straight tubules.

urine formation occurs in two phases.

The first phase is filtration. It occurs in the capsule and consists of the formation of primary urine. It is assumed that primary urine is filtered from the capillaries of the Malpighian glomerulus into the capsule cavity.

In the second phase of urine formation - reabsorption - reabsorption (reabsorption) of amino acids, glucose, vitamins, most water and salts from primary urine into the blood occurs in the nephron tubules.

Glomerular filtration- this is the first stage of urine formation, which consists of the transfer of fluid and substances dissolved in it from the glomerular capillaries into the capsule cavity

Filtration pressure represents the effective pressure, i.e. this is the difference in hydrostatic pressure in the capillaries, which promotes filtration and, preventing filtration, oncotic pressure of the blood and the hydrostatic pressure of the primary urine itself in the glomerulus of the kidney.

The filtrate entering the Shumlyansky-Bowman capsule constitutes primary urine, which in its content differs from the composition of plasma only in the absence of proteins. primary urine, containing the water necessary for the body and substances dissolved in it, most of which are of biological value, such as amino acids, carbohydrates, salts, etc.

Tubular reabsorption and secretion. Threshold substances. Composition of final urine. Diuresis.

Tubular secretion called active transport into the urine of substances contained in the blood or formed in the cells of the tubular epithelium themselves, for example, ammonia.

Tubular reabsorption- the ability of renal tubular cells to reabsorb substances from the nephron lumen into the blood.

All substances contained in blood plasma can be divided into threshold and non-threshold. TO threshold substances These include those that are excreted in the final urine only when a certain concentration in the blood is reached; for example, glucose enters the final urine only if its content in the blood exceeds 6.9 mmol/l.

Urine is usually clear, but has a small sediment obtained by centrifugation and consisting of a small amount of erythrocytes, leukocytes and epithelial cells. Protein and glucose are practically absent in the final urine. In small quantities, derivatives of the products of protein decay in the intestines - indole, skatole, phenol - enter the urine. Urine contains a wide range of organic acids, small concentrations of vitamins (except fat-soluble), biogenic amines and their metabolites, steroid hormones and their metabolites, enzymes and pigments that determine urine color.

Diuresis- the volume of urine produced over a certain period of time.

The human body has organs that help cleanse the body. One of them is the kidney. Filtration of blood and formation of urine occurs in this organ. The location of the kidneys is the lower back. Normally, the left one is 2 cm higher than the right one. Urine is the result of the excretion of end products of catabolism from the body, which enter the body with food intake. The cleansing process takes place in 3 stages. At the first stage, waste accumulates and enters the bloodstream. At the second stage, it moves along with the blood to the excretory organ. At the third stage - exit from the body through the urinary tract.

The process of urine formation in humans occurs in several stages, and kidney failure is often diagnosed by the composition of urine.

General information about the formation of urine, its properties

There are 3 phases of urine formation.

Urine is formed in nephrons, the structural unit of the kidneys. There are more than 1 million of them there. Each nephron contains a body consisting of a tangle of capillaries. There is a capsule on top, covered in layers with epithelial cells, membrane and channels. The pattern of urine formation is quite complex: plasma slips through the nephrons, resulting in the formation of primary urine, then secondary urine and, at the last stage, final urine. The blood plasma is filtered: every day, 1500 liters of blood are forced through the kidney. From this entire volume, urine is formed, the amount of which is approximately 1/1000 of the blood passed. As a result of these processes, a total cleansing of the human body occurs.

The physicochemical properties of urine are shown in the table:

Primary phase: ultrafiltration

The formation of primary urine occurs due to the purification of blood plasma from colloidal particles by the renal glomeruli. During the day, the amount of primary urine produced is about 160 liters. Synthesis occurs against the background of high hydraulic pressure in the vessels of the nephron and low pressure in the capsule around it - the difference is approximately 40 mm Hg. Art. Due to this pressure difference, liquid is filtered from the blood: water with compounds containing carbon, as well as with inorganic substances, the molecules of which are very small in mass and enter the opening of the vessel. Elements whose molecular mass is more than 80,000 atomic units no longer slip through the capillary wall and are retained in the blood. This:

• leukocytes;
• red blood cells;
• platelets;
• most of the proteins.

Secondary phase: reabsorption

Secondary urine is formed by 2 methods: active (against a concentration gradient) and passive absorption (diffusion). Due to vigorous activity, a very high oxygen consumption occurs. In the kidney it is considerably higher than in other organs. In the second stage, the ultrafiltrate enters the curved and straight tubules of the nephron and is reabsorbed or reabsorbed. The complex system of nephron channels is completely covered with blood vessels. The substances vital for the body in primary urine (water, glucose, amino acids and other elements) go in reverse and are drawn into the blood. In this way, secondary urine is formed. More than 95% of the ultrafiltrate is reabsorbed into the bloodstream, and therefore from 160 liters 1.5 liters of concentrate are obtained, that is, secondary urine.

Last phase: secretion

Primary urine differs from secondary urine. The composition of secondary urine includes a huge part of water and only 5% of dry waste, consisting of urea, uric acid, creatinine, etc. The composition of primary urine is plasma, which contains almost no proteins. Only hemoglobin and albumin can be contained in primary urine due to their small size. The process of secretion is similar to reabsorption, but in the opposite direction. In parallel with absorption, the process of secretion occurs, resulting in the formation of final urine. Thanks to secretion, substances that are in excess in the blood or do not pass filtration are removed from the body. These could be antibiotics, ammonia, etc.

Daily urine value

During the day, the kidneys of an adult healthy person produce 1-2 liters of urine, while at night they function 2 times less. The volume depends on weight, age, volume of fluid consumed, and the level of sweating. Urine contains liquid, salts and waste. However, there are no viruses or bacteria.

There are certain norms for the volume of chemical elements in urine. Therefore, with the help of its analysis, it is possible to make a comparison and, having found the difference, determine how disturbed the level of substances in the body is. The norm, deficiency or excess of creatine, urobilin, xanthine, potassium, sodium, indican, urea, uric acid, hydrochloric acid salts indicates the state of the patient’s health. All these elements are divided into organic and mineral. In general, their daily weight should be about 60 g. But if a person drinks a lot of alcohol, medications, or eats poorly, then over time, toxins will still accumulate in the blood, since they cannot be constantly processed by the kidneys.

Composition of urine

Sometimes blood appears in the urine. There are many reasons why red blood cells (red cells) get into the urine. This may primarily be due to the formation of kidney stones. The second most common cause is internal injuries. The table shows how many of which components normally enter the urine of an adult healthy individual.