Kidneys form primary urine. Primary urine is

Consists of kidneys, ureters, bladder, urethra. The kidneys filter blood and produce urine.

The kidneys consist of two layers: cortical And brain, located inside the kidney pelvis, from which it starts ureter.

The cortex of each kidney contains about a million structural and functional units - nephrons, consisting of a capsule, glomerulus and convoluted tubule. The medulla is represented by 10-15 pyramids, consisting of collecting ducts. The bases of the pyramids face the cortex, and the tops open into the pelvis.

The renal artery entering the kidneys splits into afferent arterioles, which enter inside kidney capsules(Bowman) and there they form capillary (Malpighian) glomeruli. The efferent arteriole, which leaves the capsule, is approximately twice as large as the efferent arteriole; due to this, increased pressure is created in the capillary glomerulus, due to which about 10% of the blood plasma is filtered into the cavity of Bowman’s capsule ( ultrafiltration), this is how primary urine is formed, about 170 liters per day. It does not contain large elements of blood - cells and proteins, because they cannot filter through two layers of cells: the capillary wall and the capsule wall. All other blood components - water, salts, and simple organic substances (glucose, amino acids, urea, etc.) are included in the composition of primary urine.

A convoluted tubule emerges from the renal capsule, which is entwined with capillaries into which the efferent artery breaks up. In a convoluted lot occurs reverse absorption (reabsorption) useful substances - water, amino acids, glucose, some salts. This way it is formed secondary urine, consisting of water, salts and urea, approximately 1.5 liters per day. The convoluted tubules empty into the collecting ducts, which empty into the pelvis.

From the renal pelvis, urine flows into ureter. Its walls contract peristaltically, pushing urine into bladder. The volume of the bladder is 250-500 ml; when it is full, stretch receptors in its walls begin to send signals to the urination center in the brain. Coming out of the bladder.

urethra

Drawing
Look at the drawing depicting a human organ and determine: (A) what its outer and inner anatomical layers are called, (B) the processes that ensure the purification of the blood from metabolic end products and (C) the structural formation of the organ in which solutions of substances accumulate to remove them from human body. For each letter, select the corresponding term from the list provided.
1) cortical, cerebral
2) urinary
3) renal pelvis
4) loop of Henle
5) transport of nutrients
6) epithelial, muscular

7) filtration, reverse suction

Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. Kidneys provide:
1) neutralization of toxic substances
2) synthesis of biologically active substances
3) homeostasis
4) increased immunity
5) accumulation of urine

7) filtration, reverse suction

6) biological blood filtration
1. Establish the correct sequence of passage of water in the excretory system. Write down the numbers under which they are indicated.
1) water entering the renal pelvis
2) absorption of water in convoluted tubules
3) collection of water in the bladder
4) passage of water in the renal capsule

7) filtration, reverse suction

5) removal of water through the urethra
2. Establish the sequence of processes occurring during the formation and movement of urine. Write down the corresponding sequence of numbers.
1) entry of primary urine into the renal tubules
2) the flow of secondary urine into the pelvis
3) reabsorption from primary urine
4) filtration in the nephron capsule

7) filtration, reverse suction

5) movement of urine through the ureter
3. Establish the sequence of stages of formation and movement of urine in the human body. Write down the corresponding sequence of numbers.
1) accumulation of urine in the renal pelvis
2) reabsorption from nephron tubules

3) filtration of blood plasma in the renal glomeruli

7) filtration, reverse suction

5) movement of urine through the collecting ducts of the pyramids
4. Establish the sequence of stages of formation and movement of urine in the human body.
2) movement of urine through the collecting ducts of the pyramids
3) filtration of blood from the renal glomerulus in the nephron capsule
4) outflow of urine through the ureter into the bladder
5) accumulation of urine in the renal pelvis

7) filtration, reverse suction

5. Establish the sequence of stages of urine formation. Write down the corresponding sequence of numbers.
1) formation of primary urine
2) reabsorption in convoluted tubules
3) filtration of blood plasma into the cavity of the nephron capsule
4) formation of secondary urine
5) bringing vessel
6) collecting tube

7) filtration, reverse suction

6. Establish the sequence of processes occurring in the human kidneys during the formation of urine. Write down the corresponding sequence of numbers in the table.
1) removal of urine from the renal pelvis
2) reabsorption into the capillaries of the convoluted tubules
3) the flow of urine into the collecting ducts
4) formation of primary urine
5) filtration of blood from the capillaries of the glomerulus into the capsule cavity

7) filtration, reverse suction

7. Establish the sequence of arrangement of organs in the human excretory system, starting with the organ in which urine is formed. Write down the corresponding sequence of numbers.
1) urethra
2) bladder
3) ureters
4) kidneys

7) filtration, reverse suction

Establish a correspondence between the process and the part of the human urinary system in which it occurs: 1) kidney, 2) bladder, 3) ureter. Write numbers 1-3 in the correct order.
A) formation of primary urine
B) accumulation of secondary urine
B) movement of secondary urine
D) formation of secondary urine
D) transformation of primary urine into secondary
E) movement of primary urine

7) filtration, reverse suction

In the human body, urine is formed from
1) lymph
2) blood plasma
3) tissue fluid
4) water and mineral salts

7) filtration, reverse suction

Choose three correct answers out of six and write down the numbers under which they are indicated. The nephron contains
1) capillary glomerulus
2) renal pelvis
3) renal tubule
4) renal capsule
5) ureter
6) adrenal glands

7) filtration, reverse suction

Primary urine is liquid
1) filtered from the blood capillaries into the cavity of the capsule of the renal tubule
2) filtered from the lumen of the renal tubule into the adjacent blood vessels
3) coming from the nephron to the renal pelvis
4) coming from the renal pelvis to the bladder

Formation of primary urine

First stage The formation of urine in the kidneys begins with the filtration of blood plasma in the renal glomeruli. In this case, the liquid part of the blood passes through the wall of the capillaries into the cavity of the capsule of the renal corpuscle. The ability to filter is provided by a number of anatomical features:

capillary endothelial cells are flat, they are especially thin along their periphery and have pores in these parts, through which, however, protein molecules do not pass due to their large size

The inner wall of the Shumlyansky-Bowman capsule is formed by flat epithelial cells, which also do not allow only large molecules to pass through.

The main force that ensures the possibility of filtration in the renal glomeruli is the high pressure in them due to:

high pressure in the renal artery

difference in diameter of the afferent and efferent arterioles of the renal corpuscle. The pressure in the capillaries of the body is about 60 - 70 mm Hg. Art., and in the capillaries of other tissues it is 15-30 mm Hg. Art.

The filtered plasma easily enters the nephron capsule, since the pressure in the capsule is low - about 30 mm Hg. Art. Water and all substances dissolved in the plasma, with the exception of large molecular compounds, are filtered into the capsule cavity from the capillaries. Inorganic salts, organic compounds, such as urea, uric acid, glucose, amino acids, etc. freely pass into the capsule cavity. Proteins with high molecular weight normally do not pass into the capsule cavity and remain in the blood. The liquid filtered into the capsule cavity is called primary urine 150 - 180 . Human kidneys form in a day

liters of primary urine.

Formation of secondary urine Second phase urine formation is reverse absorption (reabsorption) , occurs in convoluted tubules and the loop of Gnele. Primary urine, passing through them, undergoes a process of reverse absorption (reabsorption). Reabsorption is carried out passively on the principle of osmosis and diffusion and actively

the cells of the nephron wall themselves. The significance of this process is to return all vital substances to the blood in the required quantities and remove the end products of metabolism, toxic and foreign substances. In the initial section of the nephron, organic substances are absorbed: amino acids, glucose, low molecular weight proteins, vitamins, Na +, K +, Ca ++, Mg ++ ions, water and many other substances. In subsequent sections of the nephron, only water and ions are absorbed. The third stage is secretion:

In addition to reabsorption, an active secretion process occurs in the nephron tubules, i.e. the release of certain substances from the blood into the lumen of the nephron, carried out by the cells of the nephron walls. As a result of secretion from the blood, creatinine and medicinal substances enter the urine. The result of reabsorption and secretion is the formation, the composition of which is very different from primary urine. Secondary urine contains a high concentration of urea, uric acid, chlorine, magnesium, sodium, potassium, sulfates, phosphates, and creatinine ions. About 95% of secondary urine is water, 5% is dry residue. Approximately 1,5 liters of secondary urine.

Topic: Urine formation

Learn how the urinary system works

Formation of primary urine

In humans, 1000-1200 ml of blood flows through the kidneys in 1 minute. This is almost a quarter of the volume of blood pumped out by the heart in the same time. A person’s blood passes through the kidneys 300 times per day!

Formation of primary urine

The blood supply to the kidneys differs from the blood supply 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 intertwining the renal tubules. Such an abundant blood supply and the special structure of the capillary network of the kidneys allow the body to quickly get rid of unnecessary waste products and substances carried with the blood.

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

Formation of primary urine

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. Urine formation occurs through a number of physiological mechanisms, including three stages. Let's look at how this happens.

The first stage, filtration. In the capillary glomerulus there is high blood pressure, since the afferent arteriole of the glomerulus is almost twice as large in diameter as the efferent arteriole, and about 20% of the fluid - blood plasma from the blood of the capillaries goes into the convoluted tubule.

Formation of primary urine

The walls of the capillaries and the renal capsule act as a filter. They do not allow blood cells and large protein molecules to pass through. But other substances dissolved in the blood plasma easily pass through this filter.

The fluid formed in the cavity of the renal capsule is called primary urine. Within 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 kidney capsule.

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

Due to such selective absorption, only those substances that are not needed by the body remain in the secondary urine. The substances it needs are returned to the blood through a network of capillaries intertwining the renal tubule.

The third stage, secretion. In addition to absorption, the renal tubule also releases certain substances into its lumen. Thus, the epithelial cells 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 final breakdown products of substances or unnecessary compounds are removed from the body. Sometimes excess nutrients in the blood, such as glucose, can also be removed. Consequently, in addition to the purely excretory function, the kidneys are involved in maintaining a constant chemical composition of the blood.

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

In medical institutions, a urine test is required. It gives an idea not only of the condition of the kidneys, but also of the metabolic processes occurring in other tissues, organs, and in the body as a whole.

Urinary excretion. Urine is produced continuously in the kidneys, but is excreted periodically in separate portions. The 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 occurs in the bladder. When the bladder is filled to a certain limit, it is emptied. Emptying the bladder is a complex reflex act. The natural stimulus of this reflex is the stretching of the bladder. Irritation of the 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 micturition reflex is located in the spinal cord.

Prevention of kidney diseases. Kidneys are vital organs of our body. Violation or cessation of their function inevitably leads to poisoning of the body with substances that are usually excreted in the urine.

When kidney function is disrupted, these substances accumulate in the blood and lead to 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 secondary urine formation. As a result, huge amounts of water, glucose and other vital substances are lost. There is a serious threat to human life.

Preventing Kidney Diseases

Eating too spicy food has a harmful effect on the kidneys. Such foods often cause kidney dysfunction. An even greater evil is the consumption of alcohol, which destroys the renal epithelium and sharply disrupts or stops the formation of urine. The result is poisoning of the body with toxic metabolic products.

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

• What are the stages of the urine formation process?
• Why is there high pressure in the capillary glomerulus?
• How does filtering happen?
• What is the composition of primary urine?
• How does reabsorption occur?
• What is the urea content in blood plasma and secondary urine?
• How does secretion occur?
• 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 center of the micturition reflex located?

**Test 1. What stages does the process of urine formation consist of?

• Blood flows into the kidney through the renal artery.
• Filtration of blood plasma into the cavity of Bowman's capsules.
• Reabsorption of nutrients by the convoluted tubule epithelium.
• Secretion of unnecessary substances into the lumen of the convoluted tubule.
• Movement of secondary urine through the collecting duct into the renal pelvis.
• 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 efferent arteriole.
• The diameter of the renal artery is smaller than the diameter of the renal vein.

Test 3. How does filtration occur?

• Blood plasma from the capillary glomerulus is filtered into the convoluted tubule.
• Blood plasma from the capillary glomerulus is filtered into the cavity of 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 occur?

• The convoluted tubule epithelium reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the afferent arteriole.
• The convoluted tubule epithelium reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the efferent arteriole.
• The convoluted tubule epithelium reabsorbs water, salts, glucose and all substances that need to be stored in the body and transfers them to the renal vein.
• The convoluted tubule epithelium 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 primary urine?

• This is ordinary 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 urea content 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 secretion occur?

• Ammonia and other substances unnecessary for the body are secreted into the lumen of Bowman's 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 their urine.
• After sleep.
• In the middle of the night.
• After eating.

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

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

Test 10. Where is the center of the urination reflex located?

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

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 amounts. 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.

1) mechanism of formation of primary urine

2) mechanism of final urine formation

1. Composition and properties of urine
2. Urine excretion
3. Regulation of urine formation

Selection- this is liberation from excreta, excess water, salts, and foreign substances coming from food.

Stages of the extraction process:

· Formation of excreta and their entry from tissues into the blood

Transport of excreta by blood to organs that neutralize them, to excretory organs, to nutrient depots

· Removing excreta from the body, foreign substances that have entered the blood (penicillin, iodides, paints, etc.)

Education process and the release of urine is called diuresis. Urine is formed from blood plasma flowing through the kidneys. The process of urine formation occurs in 3 phases:

glomerular filtration

tubular reabsorption

tubular secretion

Glomerular filtration

Blood filtration occurs in the Bowman-Shumlyansky capsule, where arterial blood enters the capillaries of the Malpighian glomerulus through the afferent arteriole. High blood pressure is created in the capillaries of the glomerulus due to the difference in diameters of the afferent and efferent arterioles. In addition, blood enters here already under the pressure provided by the heart. Due to high pressure and due to the high permeability of the capsule walls, blood plasma devoid of protein enters the lumen of the capsule. Primary urine is formed. During the day, 150-170 liters are formed. Primary urine, in addition to metabolic products, also contains nutrients necessary for the body: amino acids, glucose, vitamins, salts. A prerequisite for the filtration of primary urine is high hydrostatic blood pressure in the capillaries of the glomeruli - 70-90 mm Hg. It is counteracted by oncotic blood pressure = 25-30 mmHg. and the pressure of the fluid located in the cavity of the nephron capsule is equal to 10-15 mm Hg. The value of the blood pressure difference that ensures glomerular filtration is 30 mm Hg, i.e. 75 mmHg – (30 mmHg+15 mmHg) = 30 mmHg. Urine filtration stops if glomerular blood pressure is below 30 mmHg.

The final urine produced per day is 1.5 liters. This means that the nephron must ensure the reabsorption of these substances. This process is called tubular reabsorption.

Tubular reabsorption

Tubular reabsorption is the process of transporting substances from primary urine into the blood. Primary urine, passing through the urinary tubule system, changes its composition. H 2 O, glucose, amino acids, vitamins, Na +, K +, Ca +2 ions are absorbed back into the blood. CI¯. The latter are excreted in the urine only if their concentration in the blood is higher than normal. Metabolic products (urea, creatinine, sulfates, etc.) are excreted in the urine at any concentration in the blood and are not reabsorbed. Reabsorption occurs actively and passively. Active reabsorption occurs due to the activity of the renal tubular epithelium with the participation of enzymes and energy expenditure. Glucose, amino acids, phosphates, and sodium salts are actively absorbed. They are completely absorbed in the tubules and are absent in the final urine. Passive reabsorption occurs due to diffusion and osmosis without energy expenditure. H 2 O, chlorides, etc. are reabsorbed. A special place in the mechanism of reabsorption of water and sodium ions from primary urine is occupied by the loop of Henle of the nephron due to the rotary-countercurrent system. The loop of Henle has 2 bends: descending and ascending. The epithelium of the descending part allows water to pass through, while the epithelium of the ascending part is impermeable to water, but actively absorbs Na + back into the blood. Passing through the descending part of the loop of Henle, urine releases water, thickens, and becomes more concentrated. The release of water occurs passively, since Na + ions are actively reabsorbed in the ascending part of the loop of Henle. Entering the tissue fluid, Na + ions increase the osmotic pressure in it and thereby contribute to the attraction of water into the tissue fluid from the descending part of the loop of Henle. Thus, a large amount of water and Na + ions are reabsorbed in the loop of Henle.

Tubular secretion

Secretion is the active transport of certain substances by epithelial cells with the expenditure of ATP energy.

Thanks to secretion, substances are released from the body that are not amenable to glomerular filtration or are contained in the blood in large quantities: xenobiotics (dyes, antibiotics and other drugs), organic acids and bases, ammonia, K +, H + ions.

SCHEME OF URINE FORMATION