Topic: Urine formation

Examine the work of the urinary system


Primary urine production

In humans, 1000-1200 ml of blood flows through the kidneys in 1 minute. This is almost a quarter of the volume of blood ejected by the heart during the same time. Human blood passes through the kidneys 300 times per day!




Primary urine production

The supply of blood to the kidneys differs from the supply of blood to other organs of the body in that the blood entering the kidneys sequentially passes through two networks of capillaries located one after the other: capillary glomeruli and capillaries that encircle the renal tubules. Such an abundant blood supply and a special arrangement of the capillary network of the kidneys allow the body to quickly get rid of unnecessary decay products and substances brought in with the blood.

Urine is formed from blood plasma. However, the composition of urine differs significantly from that of blood plasma.


Primary urine production

This means that the kidneys produce urine by changing the blood flowing through them. This process takes place in two stages: first, primary urine and then secondary, or final, urine. Urination is carried out using a number of physiological mechanisms, in three stages... Let's see how this happens.

First stage, filtration. There is high blood pressure in the capillary glomerulus, since the glomerular arteriole bringing in is almost twice as large in diameter as the outgoing one, and about 20% of the fluid - blood plasma from the capillary blood goes into the convoluted tubule.




Primary urine production

The walls of the capillaries and the renal capsule act as a filter. They keep blood cells and large protein molecules out. But other substances dissolved in blood plasma easily pass through this filter.

The fluid formed in the cavity of the renal capsule is called primary urine. For a day it is formed 150-170 l primary urine. Thus, primary urine is filtered blood plasma. High blood pressure causes blood plasma to be filtered through the capillary walls into the renal capsule.


The second stage, absorption (reabsorption). From the renal capsule, primary urine enters the renal tubule. Its walls are sucked in from primary urine water, amino acids, vitamins and other substances dissolved in it. Substances such as glucose are absorbed completely, others are partially absorbed, and still others, such as urea, are not absorbed at all. Therefore, the concentration of urea in the secondary urine increases more than 60 times and increases from 0.03% to 2%.



In connection with such selective absorption in the secondary urine, only those substances remain that are not needed by the body. The substances it needs are returned to the blood again through the network of capillaries that encircle the renal tubule.

Stage three, secretion. In addition to absorption, in the renal tubule, certain substances are released into its lumen. So, the cells of the epithelium of the renal tubule secrete ammonia into the urine, some dyes that enter the body, and drugs such as penicillin.


With the help of the kidneys, not only the products of the final decay of substances or compounds unnecessary to it are removed from the body. Occasionally, excess blood nutrients such as glucose can also be removed. Therefore, in addition to the purely excretory function, the kidneys are involved in maintaining a constant chemical composition of the blood.

The urine formed in the renal tubule flows down the collecting ducts into the renal pelvis. From it through the ureter enters the bladder. Under normal conditions, in the absence of hard work and normal nutrition, the amount of urine released per day in an adult is 1.2-1.5 l.




In medical institutions, urine analysis is mandatory. It gives an idea not only about the state of the kidneys, but also about the metabolic processes occurring in other tissues, organs, in the body as a whole.

Urinary excretion. In the kidneys, urine is formed continuously, but it is excreted from them periodically in separate portions. Excretion of urine is associated with rhythmic contractions of the muscles of the ureters. These contractions push small volumes of urine from the ureters into the bladder.


Further additional absorption of water into the blood takes place in the bladder. When the bubble is filled to a certain limit, it is emptied. Emptying the bladder is a complex reflex act. The natural stimulus for this reflex is the expansion of the bladder. Irritation of receptors embedded in the wall of the bladder causes contraction of its muscles and relaxation of muscle thickenings, resulting in urination.

The center of the urinary reflex is located in the spinal cord.


Prevention of renal disease. The kidneys are vital organs in our body. Violation or termination of their function inevitably leads to the poisoning of the body with those substances that are usually excreted in the urine.

If the kidneys are disrupted, these substances accumulate in the blood and lead to the most severe conditions, often ending in death.

The cells of the renal tubules are highly sensitive to poisons of various origins, including those produced by pathogens of infectious diseases. The dysfunction of such cells is accompanied by the cessation of the formation of secondary urine. As a result, a huge amount of water, glucose and other vital substances is lost. There is a serious threat to human life.





Prevention of kidney disease

Eating too spicy food has a harmful effect on the kidneys. Such food often causes impaired renal function. An even greater evil is the use of alcohol, which destroys the renal epithelium, abruptly disrupts or stops the formation of urine. As a result, the body is poisoned with toxic metabolic products.

Currently, in the treatment of patients with severe chronic kidney disease, as well as people who have lost their kidneys as a result of injury or other reasons, a healthy kidney transplant from another person is used.


  • What are the stages of the process of urination?
  • Why is there high pressure in the capillary glomerulus?
  • How does filtration work?
  • What is the composition of the primary urine?
  • How does reabsorption work?
  • What is the content of urea in blood plasma and secondary urine?
  • How does the secretion take place?
  • In what case can glucose appear in the urine of a healthy person?
  • How much primary and secondary urine is produced per day?
  • Where is the urinary reflex center located?

** Test 1. What are the stages of the process of urination?

  • The flow of blood to the kidney through the renal artery.
  • Filtration of blood plasma into the cavity of Bowman's capsules.
  • Reabsorption of nutrients by the epithelium of the convoluted tubules.
  • Secretion of unnecessary substances into the lumen of the convoluted tubule.
  • The movement of secondary urine through the collecting duct into the renal pelvis.
  • The movement of secondary urine through the ureters into the bladder.

Test 2. Why is there high pressure in the capillary glomerulus?

  • The diameter of the renal artery is greater than the diameter of the renal vein.
  • The diameter of the efferent arteriole is greater than the diameter of the afferent arteriole.
  • The diameter of the afferent arteriole is greater than the diameter of the outflow arteriole.
  • The diameter of the renal artery is smaller than the diameter of the renal vein.

Test 3. How does filtration work?

  • Blood plasma from the capillary glomerulus is filtered into the convoluted tubule.
  • Blood plasma from the capillary glomerulus is filtered into the cavity of the Bowman's capsule.
  • Blood plasma from the capillary glomerulus is filtered into the capillary network.
  • Blood plasma from the capillary glomerulus is filtered into the collecting duct.

Test 4. How does reabsorption take place?

  • The epithelium of the convoluted tubule reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the bringing arteriole.
  • The epithelium of the convoluted tubule reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the efferent arteriole.
  • The epithelium of the convoluted tubule reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the renal vein.
  • The epithelium of the convoluted tubule reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the capillary network.

Test 5. What is the composition of the primary urine?

  • This is normal blood plasma.
  • This is blood plasma without proteins.
  • This is blood plasma without proteins and fats.
  • This is blood plasma without proteins, fats and carbohydrates.

Test 6. What is the content of urea in blood plasma and secondary urine?

  • In blood plasma 0.3%, in urine - 3%.
  • In blood plasma 0.03%, in urine - 13%.
  • In blood plasma 0.003%, in urine - 2%.
  • In blood plasma 0.03%, in urine - 2%.

Test 7. How does the secretion take place?

  • Ammonia and other substances unnecessary for the body are secreted into the lumen of the Bowman capsule.
  • Ammonia and other substances unnecessary for the body are secreted into the lumen of the convoluted tubule.
  • Ammonia and other substances unnecessary for the body are secreted into the lumen of the collecting duct.
  • Ammonia and other substances unnecessary for the body are secreted into the renal pelvis.

Test 8. In what case can glucose appear in the urine of a healthy person?

  • A healthy person should not have glucose in the urine.
  • After sleep.
  • In the middle of the night.
  • After eating.

Test 9. How much primary and secondary urine is generated per day?

  • Primary urine - 10 liters, secondary 1.2-1.5 liters.
  • Primary urine - 100 liters, secondary 1.2-1.5 liters.
  • Primary urine - 130 liters, secondary 1.2-1.5 liters.
  • Primary urine - 180 liters, secondary 1.2-1.5 liters.

Test 10. Where is the urinary reflex center located?

  • In the medulla oblongata.
  • In the diencephalon.
  • In the cerebral cortex.
  • In the spinal cord.

The human body has organs that help cleanse the body. One of them is the kidney. Filtration of blood and the formation of urine occurs in this organ. The place of localization of the kidneys is the lower back. Normally, the left one is 2 cm higher than the right one. Urine is the result of excretion of the 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 gets into the blood. 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 a person takes place in several stages, and malfunctions of the kidneys are often diagnosed by the composition of urine.

General information about the formation of urine, its properties

There are 3 phases of urine production.

Urine is formed in the nephrons, the structural unit of the kidneys. There are more than 1 million of them there. Each nephron contains a small body, consisting of a ball of capillaries. Above there is a capsule, layer-by-layer covered with epithelial cells, membrane and channels. The scheme of urine formation is rather complex: plasma slips through the nephrons, as a result of which primary urine is formed, 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 all this volume, urine is formed, the amount of which is approximately 1/1000 of the passed blood. As a result of these processes, a total cleansing of the human body occurs.

Physicochemical properties of urine are shown in the table:

Primary phase: ultrafiltration


During ultrafiltration in the kidneys, the blood plasma is purified from the primary urine.

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

  • leukocytes;
  • erythrocytes;
  • platelets;
  • most of the proteins.

Secondary phase: reabsorption

Secondary urine is formed by 2 methods: active (against the 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. At the second stage, the ultrafiltrate enters the curved and straight tubules of the nephron and is reabsorbed or reabsorbed. The intricate canal system of the nephron is completely covered with blood vessels. Substances of primary urine vital for the body (water, glucose, amino acids and other elements) go backward and are drawn into the blood. In this way, the formation of secondary urine occurs. More than 95% of the ultrafiltrate is reabsorbed into the blood stream, and therefore, from 160 liters, 1.5 liters of concentrate is obtained, that is, secondary urine.

Last phase: secretion

Primary urine is different from secondary urine. The composition of the secondary urine includes a huge part of water and only 5% of dry waste, consisting of urea, uric acid, creatinine, etc. The composition of the 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 secretion process is similar to reabsorption, but in the opposite direction. In parallel with absorption, the secretion process takes place, as a result of which the final urine is formed. Due to secretion, substances that are in excess in the blood or do not pass filtration are released from the body. These can be antibiotics, ammonia, etc.

Daily urine rate

During the day, the kidneys of an adult healthy person produce 1―2 liters of urine, while at night they function 2 times less. Displacement depends on weight, age, fluid intake, and sweating level. The urine contains liquid, salt and toxins. However, there are no viruses or bacteria.

Allocate certain norms of the volume of chemical elements in the urine. Therefore, with the help of its analysis, it is possible to make a comparison and, having found a difference, determine how much the level of substances in the body is disturbed. 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 consumes a lot of alcohol, medications or does not eat well, then over time, toxins will still accumulate in the blood, since they cannot be constantly processed by the kidneys.

Urine composition

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

It is needed to remove urine outside, and in men, semen is excreted through it.

Woman's urethra It is a short tube 3-6 cm long, which is located behind the pubic symphysis. Wall myocytes form two layers: internal longitudinal and more pronounced outer - annular... The external opening is located in the vestibule of the vagina, in front of and above the vaginal opening and is surrounded by a striated external sphincter of the urethra.

Male urethra - a curved tube 18-23 cm long. Urine and seminal fluid come out through it. The canal passes through the prostate gland, the urogenital diaphragm and the corpus spongiosum.

By location, in the male urethra there are three parts- prostate, membranous, spongy.

Prostate part- length 2.5 cm. This is the widest part of the male urethra. There is an elevation on its back wall - seed mound there is a hole on it prostate uterus and holes ejaculatory ducts. On the sides of the mound are the openings of the excretory ducts of the prostate gland.

Webbed part- 1 cm long - this is the narrowest part of the male urethra, surrounded by a sphincter.

Spongy part- length 15-20cm, has two extensions:

a) in the bulb of the spongy body;

b) in the scaphoid fossa of the glans penis.

The ducts of the bulbourethral glands open into the spongy part.

The male urethra has two curvatures- front and back

The front straightens when the penis is raised, the back remains fixed

Curvatures, narrowing and widening of the male urethra are taken into account when the catheter is inserted.

Mechanisms of formation and excretion of urine.

During the day, a person consumes about 2.5 liters of water, including 1.5 liters. in liquid form and about 650 ml with solid food. In addition, in the body during the breakdown of proteins, fats and carbohydrates, another 400 ml of water is formed. Water is excreted from the body mainly through the kidneys - 1.5 liters per day.

Urine formation in the kidneys

In the formation of urine in the nephrons of the kidneys, they excrete two phases :

First phase - glomerular ultrafiltration - this education primary urine in the glomeruli of the nephrons. In the renal glomeruli, water and substances dissolved in it are filtered from the renal capillaries of the nephrons in the first phase from the blood. Ultrafiltration occurs due to the pressure difference in the capillaries of the glomeruli and in the capsule of the nephron. In the capillaries of the glomeruli there is a very high blood pressure - 60-70 mm Hg. Art. The creation of high pressure in the capillaries of the renal glomeruli is facilitated by a noticeable difference in the diameter of the vessels that bring blood to the glomeruli and carry away blood from them. The efferent arterioles of the glomeruli are 2 times larger in diameter than the efferent arterioles. Thus, the capillary network of the glomerulus is located between the two arterial vessels.

More than 1 liter of blood flows through the kidneys within 1 minute. During the day, up to 1700-1800 ml of blood passes through the kidneys. Thus, in 24 hours, all blood flows through the capillaries of the glomeruli more than 200 times. This blood comes into contact with the inner surface of the capillaries, the area of ​​which in the glomeruli of the kidneys is 1.5-2 m 2. The amount of formed primary urine reaches 150-180 liters per day. Thus, from 10 liters of blood flowing through the kidneys, 1 liter of primary urine is filtered. Primary urine contains all components of blood plasma, except for high molecular weight proteins. Primary urine contains amino acids, glucose, vitamins and salts, blood cells, as well as small amounts of urea, uric acid and other substances.

Second phase - tubular reabsorption (reabsorption) , occurs in the tubules of the nephron. As a result, a concentrated, so-called, secondary (final) urine. In the second phase, from the glomerular capsules, primary urine, which is similar in structure to blood plasma, enters the tubules of the nephrons. In the tubules, amino acids, glucose, vitamins, most of the water and salts are absorbed into the blood from the primary urine. Ultimately, within a day from 150-180 liters. primary urine is formed up to 1.5 liters. secondary urine. Secondary urine enters the bladder through the urinary tract and is excreted from the body. The tubules absorb 99% of the water contained in the primary urine. Secondary urine lacks glucose, amino acids, many salts, proteins, and blood cells. At the same time, the concentration of sulfates, phosphates, urea and uric acid is sharply increased in the secondary urine.

The human body takes up to 2.5 l of water Along with food and drink, up to 150 ml of water enter the body as a result of metabolism. In order for the body to maintain a water balance, the flow of water must be equal to its consumption. The main role in the process of excretion of water from the body is played by the kidneys. Due to daily diuresis (urination), up to 1500 ml of fluid is released. Part of the water is removed by the lungs (up to 500 ml), the skin (up to 400 ml), a small amount of it is excreted in the feces.

Every minute through the vessels of the kidneys passes up to 1.2 l of blood, while the mass of the kidneys is only 0.43% of the human body mass, which confirms the very high level of renal blood supply. If it is calculated per 100 g of tissue, then the blood flow to the kidneys is 430, the blood flow to the cardiac system is 66, and the blood flow to the brain is 53 ml / min. It is important that even a twofold increase in blood pressure (for example, from 90 to 190 mm Hg) does not affect the blood flow in the kidneys. The renal arteries are connected with the abdominal aorta, therefore, the necessary high level of blood pressure is constantly maintained in them.

How primary and secondary urine is formed

The genitourinary system performs the main function of excreting metabolic products from the body. The process of urine formation is a very complex mechanism, which consists of two stages. During the first stage, primary urine is formed by filtration in the nephron capsule. Then it passes through the convoluted tubules and the loop of Henle, where up to 99% of the water with the amino acids, sugars and some mineral salts contained in it is absorbed from it back into the blood.

What is the difference between primary and secondary urine

Primary urine is produced by renal glomerulus, consisting of a huge number of capillaries. The blood passing through them is filtered, and the secreted fluid is sent to the capsule Shumlyansky-Bowman... This will be the primary urine. It does not contain blood cells and molecules of complex proteins, since capillary walls do not allow them to pass through, however, molecules of amino acids, sugars, fats, etc. pass freely through them. Primary urine also contains water, which, passing through the tortuous tubules of the nephron, is absorbed due to increased osmotic pressure on the walls of the tubules (the so-called reabsorption).

Daily in the body is formed 150-180 l of primary urine... All the useful compounds present in it do not disappear, since they again enter the body in the process of diffusion and the transport function of the tubule walls. Substances that remain after the diffusion process will be secondary urine. It first enters the collecting ducts, then into the small and large renal cups, then collects in the renal pelvis, from which urine is excreted through the ureters into the bladder, and, after filling it, leaves the body through the urethra.

Secondary urine is more concentrated; in addition to water, it contains urea, uric acid, sodium, chlorine, potassium salts, sulfates and ammonia. It is they who give the urine its characteristic odor. The human body daily produces up to 1.5 liters of secondary urine, which is then excreted during urination. It is in the peculiarities of the formation of urine that the answer to the question is contained, what is the difference between primary and secondary urine.

Since primary urine is a liquid that was formed at the beginning of the urinary process, it is identical to blood plasma and contains only useful trace elements. Secondary urine contains residues of primary fluid that, as a result of reabsorption, have not been absorbed by the body.

conclusions

Both primary and secondary urine are stages of a single process, they are closely interconnected and their formation occurs through a gradual flow of one into another. If the primary fluid is produced by the renal glomerulus, then secondary urine is formed in the capillaries that encircle the urinary tubules. If most of the primary urine is absorbed back by the body, then the secondary urine is completely excreted from the body.

History

Primary urine was first described by Karl Ludwig (1816-1895) in 1842 in his doctoral dissertation "Contribution to the theory of the mechanism of urine excretion" (German: "Beiträge zur Lehre vom Mechanismus der Harnabsonderung").

Compound

Primary urine by its composition is plasma, practically devoid of proteins. Namely, the amount of creatinine, amino acids, glucose, urea, low molecular weight complexes and free ions in the ultrafiltrate coincides with their amount in the blood plasma. Due to the fact that the glomerular filter does not allow proteins-anions to pass through, in order to maintain Donnan's membrane equilibrium (the product of ion concentrations on one side of the membrane is equal to the product of their concentrations on the other side) in the primary urine, the concentration of chlorine and bicarbonate anions becomes about 5% higher and, accordingly, the concentration of sodium and potassium cations is proportionally lower than in blood plasma. The ultrafiltrate contains a small amount of one of the smallest protein molecules - almost 3% of hemoglobin and about 0.01% of albumin.

Properties

Primary urine has the following properties:

  1. Low osmotic pressure. It arises from membrane equilibrium.
  2. Large daily volume, which is measured in tens of liters. The entire volume of blood passes through the kidneys about 300 times. Because on average, a person has 5 liters of blood, then the kidneys filter about 1500 liters of blood per day and form about 150-180 liters of primary urine.

Glomerular filtration rate (GFR)

GFR is regulated by nervous and humoral mechanisms and affects:

  • the tone of the glomerular arterioles and, consequently, the volume of blood flow (plasma flow) and the magnitude of the filtration pressure;
  • the tone of the mesangial cells (connective tissue between the capillaries of the nephron glomerulus) and the filtration surface;
  • activity of visceral epithelial cells (or podocytes) and their functions.

Humoral factors such as prostaglandins, atriopeptides, norepinephrine and epinephrine, adenosine, and the like. can both increase and decrease glomerular filtration. The most important role in the constancy of GFR is played by the autoregulation of cortical blood flow.

Meaning

Primary urine undergoes further concentration and removal of useful substances from it. The resulting concentrated residue is secondary urine.

Links

  1. Primary urine (glomerular ultrafiltrate). Regulation of the glomerular filtration rate (GFR).
  2. E.V. Trifonov Human pneumopsychosomatology. Rus.-eng.-rus. encyclopedia, 15th ed., 2012 = Tryphonov E.B. Human Pneumapsychosomatology. The Rus.-Engl.-Rus. Encyclopedia, 15th ed., 2012.

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See what "Primary urine" is in other dictionaries:

    I Urine (urina) is a biological fluid produced by the kidneys and excreted from the body through the urinary tract. The formation and release of M. is one of the most important mechanisms for maintaining the constancy of the internal environment of the body. From the body with urine ... ... Medical encyclopedia

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    A complex process, continuously occurring in the nephridia and others, excretes, the organs of invertebrates and in the kidneys of vertebrates, ensures the production of urine and its excretion into the urinary system. Urine, as it moves along, excretes, the organ undergoes, it means ... ...

    - (named after the English doctor of the XIX century W. Bowman, W. Bowman), the cupped blind end of the urinary tubule of the kidneys. Primary urine is formed in the cavity of Bowman's capsule. * * * BOWMEN'S CAPSULE BOUMEN'S CAPSULE (named after the 19th century English physician U. ... ... encyclopedic Dictionary

    This term has other meanings, see Kidney. Kidney Human kidney. Latin name ren ... Wikipedia

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    - (from meta ... and nephridia), metamerically located paired will allocate, organs in invertebrates, ch. arr. in annelids. They develop from ectoderm or mesodermal nephroblasts. M. tubular canals opening at one end (ciliary funnel, ... ... Biological encyclopedic dictionary