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Where blood is filtered in the kidneys. Implementation of urinary function in the kidneys

The kidneys, ureters, bladder, urethra, and in men the genitals and prostate, represent the urinary system, the task of which is to produce, store and excrete urine. The main role in this system is played by the kidneys. Filtration of blood in the kidneys occurs through many renal corpuscles and tubules (nephrons).

Each kidney is a non-stop filter that processes about 1.2 liters of blood per minute in an adult.

The kidneys perform the following functions:

  • the process of urine formation takes place in them;
  • blood purification, as well as the removal of medications, toxins, etc.;
  • regulate electrolyte exchange;
  • control blood pressure and volume;
  • maintain acid-base balance.


Kidneys perform vital functions in the human body

Thanks to nephrons, the following processes occur in the kidneys.

Filtration

The filtration process in the kidneys begins with the filtering of blood through the glomerular membranes under the influence of hydrostatic pressure. As a result, a large amount of fluid, useful chemicals and toxins are lost. Substances filtered from the blood (primary urine) move into Bowman's capsule. Primary urine contains water, excess salts, glucose, urea, creatinine, amino acids and other low molecular weight compounds.

The rate of kidney filtration is its main characteristic, which affects the effective functioning of the organ and overall health.

The rate of primary urine formation is 110 ml per minute in the female body and 125 in the male. These are average values ​​that may vary depending on a person’s weight, age and other physical characteristics.

During the day, 180 liters of primary urine are formed.

Reabsorption

During the process of reabsorption, epithelial cells absorb water, glucose, and nutrients and return them to the blood.

At this stage, 178 liters or 99% of the components of primary urine return to the blood. Threshold substances are absorbed up to a certain concentration in the blood (for example, glucose), non-threshold substances are absorbed completely (for example, proteins).

Secretion

At this stage, the secretion of hydrogen ions (H+), potassium ions (K+), ammonia and some drugs occurs. Secretion and reabsorption processes occur, as a result of which primary urine is converted into secondary urine in a volume of 1.5 to 2 liters per day.

Impaired filtration process in the kidneys

The filtration capacity of the kidneys is determined using the purification indicator - clearance. It is used to determine the rate of blood purification by the kidneys of a certain substance in 1 minute. Specialists use endogenous substances (endogenous creatinine) and exogenous substances (inulin). Data is also needed on the content of milligram percentages of the substance in blood plasma (K) and urine (M), as well as minute diuresis (D) - the volume of urine excreted by the body within 1 minute.

This method reveals decreased or increased kidney filtration.

Symptoms of a broken filtration process

Filtration disturbances manifest themselves in:

  • low blood pressure;
  • renal congestion;
  • hyperedema (especially of the limbs and face);
  • impaired urination (emptying the bladder too often or, conversely, rarely);
  • change in urine color;
  • pain syndrome in the lumbar region.

Causes of impaired kidney filtration

Impaired filtration capacity of the kidneys has causes that are divided into 2 types:

  • The occurrence of pathology due to the presence of serious chronic diseases that do not directly affect the urinary system. These include: shock, dehydration, purulent-inflammatory processes, different pressures in different areas in the circulatory system, etc.
  • The kidneys stop filtering normally due to their pathology, for example: reduced glomerular surface, reduced blood supply to the kidneys, damaged glomerular membranes, as well as tubular obstruction. Polycystic disease, pyelonephritis and other diseases lead to such changes.


Filtering glomerulus of the kidney

Reduced kidney filtration

Reduced kidney filtration is characterized by an insufficient amount of primary urine formation and occurs due to:

  • low blood pressure. This condition is caused by shock and heart failure, which leads to a decrease in hydrostatic pressure in the glomeruli and, as a consequence, to disruption of the filtration process. Cardiac decompensation leads to congestion in the kidneys, resulting in increased intrarenal pressure and decreased filtration. However, the kidneys have the ability to automatically regulate blood supply and low pressure cannot fully affect the functioning of the organ;
  • narrowed renal artery and arterioles (atherosclerotic stenosis). As a result of this pathological condition, renal blood flow decreases and hydrostatic pressure in the glomeruli decreases. A strong increase in pressure occurs when the afferent arterioles have increased tone (with reflex pain anuria, administration of a large dose of adrenaline, hypertension);
  • increased oncotic pressure of the blood as a result of dehydration or the introduction of protein-based medications into the blood contribute to a drop in filtration pressure, and as a result, poor renal filtration occurs;
  • impaired outflow of urine occurs with kidney stones, prostate hypertrophy and other diseases and contributes to a progressive increase in intrarenal pressure. When it reaches 40 mmHg. Art. there is a risk of complete cessation of filtration, followed by anuria and uremia;
  • a reduced number of working glomeruli is observed in chronic nephritis and nephrosclerosis. As a result, the filtration area is limited and primary urine is formed in smaller quantities. These changes may indicate damage to the filter membrane and contribute to the occurrence of uremia;
  • a damaged filter membrane causes a disruption in the filtration of the organ.

Filtration of blood in the kidneys is slow, most often with heart failure, hypotension and the presence of tumors, which contribute to a decrease in pressure in the kidneys and contribute to the occurrence of renal failure.

Increased kidney filtration

This pathological condition is caused by:

  • increased tone of the efferent arteriole, which occurs when a small dose of adrenaline enters the body, in the initial stages of nephritis or hypertension;
  • decreased tone of the afferent arteriole can occur reflexively with limited blood circulation to the external part of the body (for example: fever leads to increased diuresis when the temperature rises);
  • decreased oncotic blood pressure due to copious fluid administration or blood thinning.

Increased filtration is also observed in lupus erythematosus and diabetes mellitus, leading to increased diuresis, as a result of which the body loses essential amino acids, glucose and other substances.


Diabetes mellitus is one of the causes of impaired kidney filtration

Treatment of impaired blood filtration

The treatment regimen for the pathological condition is determined individually by the nephrologist, depending on the patient’s condition and the underlying disease that must be combated.

The most commonly prescribed medications by specialists are Theobromine and Eufillin, which are diuretics and can improve kidney filtration.

Treatment also involves following a diet. It is necessary to exclude fatty, fried, salty and spicy foods from the diet. Protein intake should also be limited. Boiled, stewed or steamed dishes are recommended. These restrictions are relevant both for treatment and for preventive purposes.


Diet is important in the treatment of kidney filtration disorders

The drinking regime should be increased to 1.2 liters of fluid per day. An exception may be the presence of edema.

To normalize kidney function, folk remedies are used. The watermelon diet, diuretic decoctions and herbal infusions, teas have proven themselves well:

  • parsley (1 tablespoon of roots and seeds) pour boiling water (0.5 l), leave for several hours. Drink half a glass 2 times a day;
  • Pour boiling water over rosehip root (2 tablespoons of roots), boil for 15 minutes. Drink 1/3 glass three times a day.

You should also give up alcohol, avoid stress, get plenty of rest and take the necessary measures to boost your immunity.

Self-medication is strictly prohibited. Only timely diagnosis and treatment of pathology, as well as concomitant diseases with the help of specialists, can lead to a positive result.

Human blood is of great importance for the normal functioning of the body, therefore the condition of the entire body depends on its purity. Under the influence of negative external influences, changes associated with age, bad habits and poor nutrition, gradual contamination of the blood occurs with toxins, toxic and other substances that have a negative effect on it.

You can help your body become healthier and stronger if you periodically perform blood cleansing procedures. This is precisely why the plasmapheresis procedure is performed.

You need to know that this method of healing cannot be carried out independently. All procedures must be performed only in a medical facility and only by highly qualified specialists. And also, before deciding on such treatment, you can consult with a doctor who has already performed such “operations” more than once.

Pros and cons of plasmapheresis

The plasmapheresis procedure involves the process of removing plasma from the blood. After this, the plasma is filtered. Then all the necessary elements are taken from it, which renew the blood and are reintroduced into the human body. Of the volume of blood fluid that was taken, only 25% ends up in the filter. In order to complete the entire volume, add saline solution.

Benefits of the procedure

As already said, plasmapheresis should be performed in a medical clinic and by experienced doctors. Another condition is that the procedure is carried out using materials that have undergone thorough sterilization and using disposable instruments.

Before performing the “operation” of plasmapheresis, the specialist performing such treatment must carry out an individual calculation of the volume of blood required for cleaning. Therefore, the attending physician requires information about the patient’s height and weight, as well as information about preliminary studies completed.

During blood collection and plasma injection into the body, the person is monitored by medical personnel. At the same time, with the help of devices, the state of pulse and pressure is constantly monitored, as well as how fast the patient’s breathing is.

During the “operation” itself, the patient is monitored by medical personnel who have experience in performing these procedures. Special equipment is also attached to the patient, which monitors the condition of the body. Devices are also connected to the patient to monitor how oxygenated the blood is and the breathing rate.

Another advantage of plasmapheresis is painlessness. For this purpose, no painkillers or medications of this type are used. Taking and administering blood is absolutely easy. In addition to the collected and processed plasma, only saline solution and drugs that replace blood fluid are injected into the human body.

The renewal of blood has a general effect on the human body. After the procedure, changes in health occur.

  1. Immunity increases.
  2. The consistency of the blood becomes more liquid, which is the prevention of heart disease.
  3. The amount of cholesterol decreases.
  4. The pressure becomes stable.
  5. Metabolism is restored.
  6. The possibility of oxygen starvation is excluded.

It is very important that the plasmapheresis procedure is carried out according to all the rules. Since any violation can cause complications.

Side effects

After the patient's blood has been renewed, he may experience minor negative effects, expressed in symptoms:

  • blurred vision periodically occurs in the eyes;
  • slight dizziness;
  • pressure in the arterial system may decrease.

As a result of plasmapheresis, substances such as immunoglobulins are removed. This happens when plasma is removed from the blood. But still, this does not affect the immune system.

Results of one session

As a result of the session, almost 20% of those harmful substances that negatively affect health are removed from the blood taken. But if the patient has a fairly severe form of any disease, then such treatment may be ineffective.

For a more effective result, it is necessary to carry out a complex, including a number of therapeutic procedures and strict diets that help strengthen the health of the entire body.

For whom is this procedure necessary?

Blood cleansing is not possible for every disease. Among the many human diseases there are about two hundred. It is for these diseases that this procedure is most effective and permissible.

Such diseases include disorders of certain body systems, as well as its reaction to any injury. In most cases, it is the doctor who determines whether this procedure is possible and necessary. Diseases for which blood cleansing is prescribed include damage to the skin that occurs due to an allergic reaction, inflammatory processes, or burns.

The “operation” is considered to be most effective if there is an infection in the human body, or with diseases such as periodontal disease, chlamydia, or serious forms of poisoning.

Very often, this procedure is prescribed to women who are planning to conceive a child. Because for the normal development of the fetus, it is necessary that there are no toxins in the mother’s body. This is especially useful for women who smoke, drink alcohol, have used drugs, or medications containing toxins.

It is also advisable to carry out blood cleansing for pregnant women suffering from allergies or for the purpose of its prevention. Indications for this method of treatment are:

  • the presence of a chronic infection in the body;
  • autoimmune diseases;
  • Rhesus conflict that has arisen.
  • In what cases is plasmapheresis contraindicated?

It is strictly forbidden to carry out the plasmapheresis procedure in case of heavy bleeding, especially if it cannot be stopped. Before the “operation”, tests are taken from the patient, which, after examination, reveal the presence of contraindications. It is not advisable for a patient to perform blood cleansing if he:

  • poor coagulation of blood fluid was revealed;
  • pressure too low;
  • cardiac dysfunction;
  • have serious illnesses;
  • a small amount of protein was found in the blood;
  • there is an infection in the body;
  • underdeveloped veins.

If the patient is female, then plasmapheresis is prohibited during the menstrual cycle, since during this period the patient already loses blood, which is renewed independently.

In the event that there is any contraindication, then he simply must consult a specialist. Since this “operation” may not only not give the desired result, but also completely negatively affect the patient’s condition.

How is blood purified?

This procedure is one of the most popular methods of blood purification. Medical personnel perform this “operation” in six stages.

  1. First, blood is drawn.
  2. After this, the blood is separated into its constituent elements.
  3. Next, the substances obtained as a result of processing are reintroduced into the bloodstream.
  4. The missing amount of plasma is replaced with a special physiological solution.
  5. Plasma that has been processed or that was taken from the patient is added to it.
  6. The fluid obtained as a result of this entire process is reintroduced into the body.

Additional plasma treatment services are also provided. However, this can only be done in cases of an individual approach.

The process is performed only if there are special devices and apparatus in medical clinics. The patient must lie down during each procedure.

Blood fluid is removed from the body using one or two needles. The devices used in this procedure must be large, much larger than the needles that are inserted into the veins when connecting the IV.

  1. Fractions are separated by three methods.
  2. Filtration or membrane.
  3. Centrifugal or gravity.
  4. Cascade.

First method

The blood fluid that was taken from the patient is filtered in devices created for this procedure. When the entire stage is completed, the resulting substances are introduced into the patient’s blood, but the plasma substances are destroyed or further filtered. The same applies to cells that have not undergone treatment.

Second method

The collected blood is placed in bags, which are then sent to a centrifuge. The formed element settles in the apparatus. The blood is divided into cell masses and plasma. The plasma is subsequently removed from the bag and the resulting elements are reintroduced into the bloodstream.

Third method

The collected plasma is filtered in a special device. During the filtration process, the plasma passes through an additional filter insert, which allows only low molecular weight proteins to pass through.

Last stage of the procedure

The final stage consists of returning the processed formed elements to the patient by introducing them into the blood. Since these elements are quite dense, the lack of plasma, which dilutes the liquid, is replaced with saline solution or solutions that can replace blood. It is also possible to return your own plasma, but only after it has undergone additional filtration. When a patient has a plasma pathology, then the patient is injected with donor plasma, which is enriched with the protein fraction.

What method will be used for fractional separation, what composition will be used and in what volume the solution will be processed, the amount of plasma that needs to be removed is decided on an individual basis.

In a number of diseases, there is a need to remove harmful substances from the blood that cause the disease process in the body. Plasmapheresis is a procedure for purifying the blood and the body as a whole. The effectiveness of plasmapheresis has also been proven for various forms of severe and incurable autoimmune diseases in a variety of fields of medicine.

Efferent medicine

Plasma filters and membrane plasmapheresis devices produced by TRACKPORE TECHNOLOGY are instruments of a branch of medicine called efferent medicine. Its basis is the purification of human blood from toxic substances that our body accumulates in the process of life, from harmful bacteria and microbes that cause mass diseases. Efferent medicine is an assistant in the treatment of more than 200 diseases, which include allergic and autoimmune diseases, chronic hepatitis, diabetes mellitus, etc., in relieving toxicosis in pregnant women, in eliminating the consequences of drug and alcohol use, and simply in cleansing the blood of toxins, which delays the aging of the body.

Blood purification - plasmapheresis

Plasmapheresis is a method of efferent therapy based on the removal of the liquid part of whole blood - plasma, which contains compounds harmful to the body, toxins and viruses. The patient's blood is passed through a membrane plasma filter to separate plasma and red blood cells. The plasma is separated from the cellular elements and removed along with toxins and pathological elements, while the cellular elements are returned to the patient. The advantage of plasmapheresis compared to drug treatment methods is the absence of addiction and side effects.

Cascade blood filtration

Unlike therapeutic plasmapheresis, when plasma with autoimmune factors is removed from the body and disposed of, the plasma obtained by the cascade plasmapheresis apparatus is sent to a secondary filter. At this stage, unlike conventional plasmapheresis, only harmful components are selectively removed from the plasma. The purified plasma is returned to the person.

The main purpose of using cascade plasmapheresis is to combat atherosclerosis, which causes myocardial infarction, stroke and other severe cardiovascular diseases. Cascade filtration of plasma is also the basis of other methods of efferent therapy. With the help of cascade plasma filtration, some specific treatment methods are carried out, in particular LDL apheresis, or the removal of low-density lipoproteins using filtration technology. In this case, at the second stage, the plasma obtained as a result of filtration of the first stage is passed through columns with sorbents.

The urinary system is an organic complex that produces, stores and excretes urine. The main organ of this system is the kidney. In fact, urine is a product that is formed due to the processing of blood plasma. Therefore, urine also belongs to organic biomaterials. It is distinguished from plasma only by the absence of glucose, proteins and some microelements, as well as the content of metabolic products. This is why urine has such a specific color and smell.

Filtration of blood in the kidneys

To understand the mechanism of blood purification and urine formation, you need to have an understanding of the structure of the kidney. This paired organ consists of a huge number of nephrons, in which urine formation occurs.

The main renal functions are:

  1. Urination;
  2. , excretion of drugs, metabolites, etc.;
  3. Regulation of electrolyte metabolism;
  4. Control of blood pressure and volume;
  5. Maintaining acid-base balance.

In fact, the kidneys are non-stop functioning filters that process up to 1.2 liters of blood per minute.

Each bud is bean-shaped. Each kidney has a kind of depression, which is also called a gate. They lead into a fat-filled space or sinus. The pyelocaliceal system, nerve fibers and vascular system are also located there. The vein and artery of the kidney, as well as the ureter, emerge from the same portal.

Each kidney consists of many nephrons, which are a complex of tubules and a glomerulus. Blood filtration occurs directly in the renal corpuscle or glomerulus. This is where urine is filtered from the blood and goes into the bladder.
Video of the structure of the kidneys

Where does it happen?

The kidney is, as it were, placed in a capsule, under which there is a granular layer called the cortex, and below it is the medulla. The medulla folds into renal pyramids, between which there are columns that expand towards the renal sinuses. At the tops of these pyramids there are papillae, which empty the pyramids, removing their contents into small calyxes, then into large ones.

The number of calyces may vary in each person, although in general 2-3 large calyces branch into 4-5 small calyces, with one small calyx necessarily surrounding the pyramidal papilla. From the small calyx, urine enters the large calyx, and then into the ureter and bladder structures.

Blood is supplied to the kidneys through the renal artery, which branches into smaller vessels, then the blood enters the arterioles, which divide into 5-8 capillaries. This is how the blood enters the glomerular system, where the filtration process takes place.

Renal filtration scheme

Glomerular filtration - definition

Filtration in the glomeruli of the kidneys occurs according to a simple principle:

  • First, fluid is squeezed out/filtered from the glomerular membranes under hydrostatic pressure (≈125 ml/min);
  • The filtered fluid then passes through the nephrons, most of it in the form of water and necessary elements is returned to the blood, and the rest is formed into urine;
  • The average rate of urine formation is about 1 ml/min.

The glomerulus of the kidney filters the blood, clearing it of various proteins. During the filtration process, primary urine is formed.

The main characteristic of the filtration process is its speed, which is determined by factors affecting renal activity and the general state of human health.

The glomerular filtration rate is the volume of primary urine produced in the renal structures per minute. The normal filtration rate is 110 ml/min in women and 125 ml/min in men. These indicators act as a kind of guidelines, which are subject to correction in accordance with the weight, age and other indicators of the patient.

Glomerular filtration circuit

Filtration violations

Nephrons filter up to 180 liters of primary urine per day. All the blood in the body can be cleansed by the kidneys 60 times per day.

But some factors can provoke disruption of the filtration process:

  • Reduced pressure;
  • Urinary outflow disorders;
  • Narrowing of the kidney artery;
  • Trauma or damage to the membrane that performs filtering functions;
  • Increased oncotic pressure;
  • Reducing the number of “working” glomeruli.

Such conditions most often cause filtration disorders.

How to determine a violation

Violation of filtration activity is determined by calculating its speed. You can determine how limited filtration is in the kidneys using various formulas. In general, the process of determining the rate comes down to comparing the level of a certain control substance in the patient’s urine and blood.

Typically, inulin, which is a fructose polysaccharide, is used as a comparative standard. Its concentration in the urine is compared with the content in the blood, and then the insulin content is calculated.

The more inulin in urine in relation to its level in the blood, the greater the volume of filtered blood. This indicator is also called inulin clearance and is considered as a value of purified blood. But how to calculate the filtration rate?

The formula for calculating the glomerular filtration rate of the kidneys is as follows:

GFR (ml/min),

where Min is the amount of inulin in urine, Pin is the content of inulin in plasma, Vurine is the volume of final urine, and GFR is the glomerular filtration rate.

Renal activity can also be calculated using the Cockcroft-Gault formula, which looks like this:

When measuring filtration in women, the result obtained must be multiplied by 0.85.

Quite often in clinical settings, creatinine clearance is used to measure GFR. Such a study is also called the Rehberg test. In the early morning, the patient drinks 0.5 liters of water and immediately empties the bladder. After this, you need to urinate every hour, collecting urine in different containers and noting the duration of each urination.

Then the venous blood is examined and glomerular filtration is calculated using a special formula:

Fi = (U1/p) x V1,

where Fi is glomerular filtration, U1 is the content of the control component, p is the level of creatinine in the blood, and V1 is the duration of the test urination. Using this formula, a calculation is made every hour throughout the day.

Symptoms

Signs of impaired glomerular filtration are usually reduced to changes of a quantitative (increase or decrease in filtration) and qualitative (proteinuria) nature.

Additional signs include:

  • Decreased pressure;
  • Renal congestion;
  • Hyperswelling, especially in the limbs and face;
  • Urinary disorders such as decreased or increased urge, the appearance of uncharacteristic sediment or color changes;
  • Pain in the lumbar area
  • Accumulation of various kinds of metabolites in the blood, etc.

A drop in pressure usually occurs during shock or myocardial failure.

Symptoms of glomerular filtration disorder in the kidneys

How to improve filtering

It is extremely necessary to restore kidney filtration, especially if there is persistent hypertension. Along with urine, excess electrolytes and fluids are washed out of the body. It is their delay that causes an increase in blood pressure.

To improve renal activity, in particular glomerular filtration, specialists may prescribe medications such as:

  • Theobromine is a weak diuretic that, by increasing renal blood flow, increases filtration activity;
  • Euphylline is also a diuretic containing theophylline (an alkaloid) and ethylene diamide.

In addition to taking medications, it is necessary to normalize the patient’s general well-being, restore immunity, normalize blood pressure, etc.

To restore kidney function, you also need to eat a balanced diet and follow a daily routine. Only an integrated approach will help normalize the filtration activity of the kidneys.

Folk methods such as the watermelon diet, rosehip infusion, diuretic infusions and herbal infusions, teas, etc. also help a lot in increasing renal activity. But before doing anything, you need to consult a nephrologist.

EXCRETORY SYSTEM

C1. Why is the volume of urine excreted by the human body per day not equal to the volume of liquid drunk during the same time?

1) part of the water is used by the body or formed in metabolic processes;

2) part of the water evaporates through the respiratory organs and through the sweat glands.

C2 Find errors in the given text. Indicate the numbers of the sentences in which errors were made and correct them.

1. The human urinary system contains the kidneys, adrenal glands, ureters, bladder and urethra. 2. The main organ of the excretory system is the kidneys. 3. Blood and lymph containing the end products of metabolism enter the kidneys through the vessels. 4. Blood filtration and urine formation occur in the renal pelvis. 5. Absorption of excess water into the blood occurs in the nephron tubule. 6. The ureters carry urine into the bladder.

Errors were made in sentences 1, 3, 4.

C2. Find errors in the given text. Indicate the numbers of the sentences in which errors were made and correct them.

1.The human urinary system contains the kidneys, adrenal glands, ureters, bladder and urethra. 2. The main organ of the excretory system is the kidneys. 3. Blood and lymph containing the end products of metabolism enter the kidneys through the vessels. 4. Blood filtration and urine formation occur in the renal pelvis. 5. Absorption of excess water into the blood occurs in the nephron tubule. 6. The ureters carry urine into the bladder.

Errors made in sentences:

1) 1. The human urinary system contains the kidneys, ureters, bladder and urethra

2) 3. Blood containing the end products of metabolism enters the kidneys through the vessels

3) 4. Filtration of blood and formation of urine occurs in the nephrons (glomeruli, renal capsules and renal tubules).

C2 What function does the organ shown in the figure perform in the human body? Which parts of this organ are indicated by numbers 1 and 2? Indicate their functions.



1) Kidney – cleanses the blood of end products of metabolism, urine is formed in it;

2) 1 – the cortical layer of the kidney, contains nephrons with capillary glomeruli that filter blood plasma;

3) 2 - renal pelvis, secondary urine collects in it.

C3 Name at least 4 kidney functions

1) excretory - achieved by the processes of filtration and secretion. Filtration occurs in the glomeruli, and secretion and reabsorption occur in the tubules.

2) maintaining the acid-base balance of blood plasma.

3) ensure the constancy of the concentration of osmotically active substances in the blood under different water conditions to maintain water-salt balance.

4) the end products of nitrogen metabolism, foreign and toxic compounds (including many drugs), and excess organic and inorganic substances are removed from the body through the kidneys

5) in the formation of biologically active substances that play an important role in the regulation of blood pressure, as well as a hormone that regulates the rate of red blood cell formation.

C3 Indicate the functions of the kidneys in mammals and humans.

1. Maintaining water-salt metabolism (removal of water and mineral salts)

2. Maintaining acid-base balance

3. Kidneys - biological filters (removal of drugs, poisons and other substances)

4. Synthesis of biologically active substances (stimulation of the process of hematopoiesis, increased blood pressure).

C3 How primary and secondary urine is formed in the kidneys

The process of urine formation takes place in two stages.

The first takes place in the capsules of the outer layer of the kidneys (the glomerulus). All the liquid part of the blood that enters the glomeruli of the kidneys is filtered and ends up in capsules. This is how primary urine is formed, which is practically blood plasma.

Primary urine contains, along with dissimilation products, amino acids, glucose, and many other compounds necessary for the body. Only proteins from blood plasma are absent in primary urine. This is understandable: after all, proteins are not filtered.

The second stage of urine formation is that primary urine passes through a complex system of tubules, where substances and water necessary for the body are sequentially absorbed. Everything harmful to the functioning of the body remains in the tubules and is excreted from the kidneys through the ureters into the bladder in the form of urine. This final urine is called secondary urine.

C3. What organs perform the excretory function in the human body and what substances do they remove?