As part of an anatomy course, students are required to be told where leukocytes are formed in humans. However, the information is not secret, so find out this interesting fact Any interested person can. Let's consider what kind of cells these are, how they differ and, of course, where they are formed.

Why are they needed?

Before finding out where leukocytes are formed in humans, you should understand the essence of the phenomenon: what kind of cells are designated by this name? Doctors say that this blood element is one of the most important, as it forms a barrier that can protect the body from negative influence external factors affecting the circulatory system. If a person falls ill, he is immediately given a referral for a blood test to determine the level of leukocytes - this information will allow him to get a complete picture of what is happening in the body.

White blood cells (leukocytes) allow you to make a preliminary diagnosis quite accurately, as well as determine which additional research required. If the number of cells is abnormal, it is probably due to serious illness. Since the doctor knows where leukocytes are formed and how long they live, based on the concentration of these elements of the circulatory system, he can tell whether the disease is beginning or is currently observed active stage. The doctor will explain in detail what to do to defeat the pathology.

Red blood cells, white blood cells and platelets - important elements, formed by the hematopoietic system. Disturbances in its activity are considered very serious, life-threatening problems for the patient. It’s not surprising, because blood cells form vital organs:

• bone marrow;
• tonsils;
• lymph nodes;
• spleen.

Leukocytes themselves can produce active compounds - antibodies that can fight inflammatory mediators. The process of the appearance of cells in medicine is called leukopoiesis. The largest percentage is formed in the bone marrow. The duration of existence of a leukocyte is up to 12 days.

Blood concentration

Knowing where red blood cells and white blood cells are formed, you can look at the known parameters of the concentration of blood elements - what is normal and what should cause concern. To identify specific indicators, the doctor issues a referral for general analysis. The number of leukocytes is measured at a concentration of 10^9/l. With results of 4.2-10*10^9/l there is nothing to worry about; such values ​​are considered normal for adults. IN childhood norm - 5.5-15.5*10^9/l. Based on the information obtained by the laboratory technicians, the doctor will also determine how the different fractions of these cells relate to each other.

If the indicator turns out to be outside the norm, this does not mean that the activity of the organ where leukocytes are formed is impaired. The probability of an erroneous result is no less high: for example, there could be a failure in the laboratory that caused an incorrect result. If leukocytopenia is suspected, leukocytosis should be done comprehensive study. Only if all its stages confirm the preliminary diagnosis, treatment begins. First, the patient will be sent for a repeat general analysis, and then the doctor will make a decision based on the results. In some cases, based on these data, it is possible to select a course of treatment.

What's in my numbers for you?

To navigate what is happening in the body, at the appointment it is important not only to ask the doctor about where leukocytes are formed and where they are destroyed, what standard indicators for these cells are currently isolated, but also to clarify what numbers were obtained in the laboratory and what this may indicate. The doctor is obliged to clearly explain to the person what the quantitative indicators obtained allow one to suspect.

If the activity of the organs where leukocytes are formed is more active (weaker) than normal, and blood parameters are close to critical, then you need to change the menu and lifestyle. To normalize blood composition, you need to constantly move actively. Otherwise, serious illnesses cannot be avoided.

How will they find out?

Doctors know exactly where white blood cells are produced. The liver, for example, is the source of one type of these cells - monocytes. During the analysis, the doctor will receive information about the ratios different types elements of the circulatory system. In the laboratory, this data is obtained using a Goryaev camera. It's so high precision optical instrument, which automatically calculates the concentration of specified elements. It has low error and high accuracy.

Visually, the device looks like a simple rectangular glass, but a microscopic mesh is applied to it.

Features of the analysis

It is necessary to pay attention to the activity of the organs where leukocytes are formed if, based on the results of a correctly conducted study, the indicators were outside normal limits. But what does “correct” mean? To understand this, it is worth understanding the procedure itself.

First, acetic acid is poured into the test tube, the color of which is changed due to methylene blue. A drop of the patient’s blood is dropped into the reagent and mixed thoroughly, the chamber and glass are wiped with clean gauze, the glass is rubbed against the chamber and wait for the formation of multi-colored rings. The chamber is filled with plasma. Waiting time is one minute. After this period, the cells stop moving. The laboratory technician uses a special formula to accurately calculate the indicators.

Why are leukocytes needed?

Where these cells are formed is already indicated above; the main responsible organ is the bone marrow. But why are they needed? Science asked this question quite a long time ago and found a comprehensive answer to it. Of course, scientists assume that some functions of leukocytes have yet to be discovered, but even today humanity has an impressive database on the capabilities of cells.

The organs where leukocytes are formed are responsible for immunity, since the blood cells they produce are the main defenders of our body. IN equally they give a person both nonspecific and specific immune protection. One of the key concepts in the operation of such a system is phagocytosis, that is, the capture of agents potentially dangerous to humans by blood cells. In addition, during phagocytosis of the cell immune system can immediately destroy hostile elements.

What else?

Leukocytes are also transporters, thanks to which amino acids are adsorbed, active ingredients, enzyme substances and other cells important for body tissues. White blood cells receive these substances and deliver them to the tissues that need them, moving through the blood vessel.

Leukocytes ensure blood clotting. This functionality is called “hemostatic”. Sanitary health is no less significant - leukocytes can break down cells and organic tissues that have already died under the influence of infection, injury, or other types of damage.

What to pay attention to

One of important functions leukocytes - synthetic. This means that it is through such blood cells that the formation of some components necessary for normal life occurs. human body. It's about about histamine, heparin.

There are several types of leukocytes in the human body. Each of them has specific functions and structural features. The division into groups is based not only on the duration of the existence of cells, but also on the organs producing a particular type.

What is highlighted?

There are granular leukocytes (where they are formed, doctors established quite a long time ago - in the bone marrow) - these are called granulocytes. The name is due to the structural feature of the cytoplasm. The second group is agranulocytes, that is, not granular. Such cells are formed in the bone marrow and in other organs listed above - the spleen, the lymphatic system.

Granulocytes last up to 30 hours, but agranulocytes last up to three weeks (but not less than 40 hours in healthy person). The division into these groups simplifies the diagnosis based on laboratory tests.

Neutrophils

From half to 70% of the total mass of leukocytes is composed of this particular category of cells. They are produced by the bone marrow and belong to the class of phagocytes. There are two types of molecules: with a rod-shaped core (immature) and mature - segmented. Most of the blood contains mature cells of this class, the least - young ones. By identifying the ratio of the number of these groups, the intensity of hematopoiesis can be assessed. With significant blood loss, the cells do not get the opportunity to mature, then the ratio changes in favor of young compounds.

Lymphocytes

A distinctive feature of such cells is the ability to distinguish foreign, malicious connections and the host organism's own. In addition, it is lymphocytes that are able to remember infection, fungal and microbial invasions, if they occurred at any period of life. As soon as infection occurs, transport through the circulatory system of lymphocytes that can eliminate aggressive factors is immediately organized. This is a kind of line of defense for the body, thanks to which it starts complex process immune protection. Such a complex interconnected systemic reaction helps to localize inflammation and prevents it from spreading to healthy tissue in the vicinity.

Lymphocytes are the main element of the immune system. As soon as inflammation begins, almost instantly this type of cell is “at the scene.”

Eosinophils

Such cells are present in the body in slightly lower concentrations than, for example, neutrophils, but their functionality is in many ways similar to this largest group. Eosinophils provide movement towards the point of origin of the aggressive factor. Such cells can quickly move around vascular system, absorbing harmful agents.

A key feature of this class of blood cells is the ability to absorb fairly large elements. In this way, tissues affected by inflammation, already dead leukocytes and various microscopic life forms are removed from the body. Monocytes are fairly long-living compounds that clean tissues and prepare them for the regeneration process. Without them, full recovery is impossible. Monocytes are responsible for normalizing the condition of body tissues after damage by infection, fungi, and viruses.

Basophils

This group of blood cells is the least numerous - only one percent of the total mass. Such cells are like ambulance. They are the first to appear if tissue poisoning, damage by vapors, or substances that are poisons for the human body are noted. For example, if a spider or snake has bitten, then the first to be delivered to the “scene of events” are: circulatory system namely basophils.

Leukocytosis

This term refers to the situation of a pathological increase in the concentration of leukocytes in human blood. Even healthy people sometimes experience this condition. It can be provoked by long-term exposure to direct sun rays, negative emotional experiences or prolonged stress. Leukocytosis can be provoked physical activity beyond measure. In females, this condition is observed during pregnancy and menstruation.

Leukocyte count – important indicator for diagnosing pathological conditions. The body constantly produces white blood cells, and their levels in the blood can change throughout the day. How are these cells produced and what role do they play in the human body?

Several species swim in the blood shaped elements that support the health of the whole organism. White cells that have a nucleus inside are called leukocytes. Their peculiarity is the ability to penetrate the capillary wall and enter the intercellular space. It is there that they find foreign particles and absorb them, normalizing the vital activity of the cells of the human body.

Leukocytes include several types of cells that differ slightly in origin and appearance. The most popular division is based on morphological characteristics.

The ratio of these cells is the same in all healthy people and is expressed leukocyte formula. By changing the number of any type of cells, doctors draw conclusions about the nature of the pathological process.

Important: It is leukocytes that maintain human health at the proper level. Most infections that enter the human body are asymptomatic due to a timely immune response.

The importance of leukocytes is explained by their participation in the immune response and protecting the body from any foreign agents. The main functions of white cells are as follows:

1. Antibody production.
2. Absorption of foreign particles – phagocytosis.
3. Destruction and removal of toxins.

Each type of leukocyte is responsible for certain processes, which help in carrying out the main functions:

1. Eosinophils. They are considered the main agents for the destruction of allergens. They participate in the neutralization of many foreign components that have a protein structure.
2. Basophils. They accelerate the healing process at the site of inflammation, due to the presence of heparin in its structure. Updated every 12 hours.
3. Neutrophils. Participate directly in phagocytosis. Capable of penetrating into the intercellular fluid and into the cell where the microbe lives. One such immune cell can digest up to 20 bacteria. Fighting microbes, the neutrophil dies. Acute inflammation provoke a sharp production of such cells by the body, which is immediately reflected in the leukocyte formula as an increased number.
4. Monocytes. Helps neutrophils. They are more active if an acidic environment develops at the site of inflammation.
5. Lymphocytes. They distinguish their own cells from foreign cells by their structure and participate in the production of antibodies. They live for several years. Are the most an important component immune protection.

Important: many doctors force you to do this before prescribing treatment clinical analysis blood. Viral and bacterial diseases cause various changes in the analysis, which makes it possible to put correct diagnosis and prescribe the necessary medications.

All types of white blood cells are produced in the bone marrow, which is found inside the bones. It contains a huge number of immature cells similar to those found in an embryo. From them, as a result of a complex multi-stage process, various hematopoietic cells are formed, including all types of leukocytes.

The transformation occurs as a result of the division of immature cells. With each stage they become more differentiated and designed to perform more specific functions. All stages, and there can be up to 9 of them, occur in the bone marrow. The exception is lymphocytes. To fully “grow up,” they will need to mature in the lymphoid organs.

Leukocytes accumulate in the bone marrow, and during the inflammatory process they enter the blood and reach the pathological focus. After fulfilling their purpose, the cells die, and the bone marrow forms new ones. Normally, only a small part of the body’s total leukocyte reserves floats in the bloodstream (up to 2%).

During the inflammatory process, all cells rush to the site of its localization. Neutrophil reserves for such emergency surges are located on the walls of blood vessels. It is this depot that allows the body to quickly respond to inflammation.

Lymphocytes can mature into T or B cells. The former regulate the production of antibodies, and the latter recognize foreign agents and neutralize them. Intermediate T cell development occurs in the thymus. The final maturation of lymphocytes occurs in the spleen and lymph nodes. It is there that they actively divide and turn into full-fledged immune defense. During inflammation, lymphocytes move to the nearest lymph node.

Important: The mechanism of leukocyte formation is very complex. Don't forget the importance of the spleen and other organs. For example, drinking alcohol has a negative effect on them.

Video - Leukocytes

Lack of white blood cells

Leukopenia in an adult is a condition when the number of leukocytes is below 4 * 10 9 / l. This may be caused by malignant diseases, exposure to radiation, vitamin deficiencies or problems with hematopoietic function.

Leukopenia leads to the rapid development of various infections and a decrease in the body's resistance. A person feels chills, body temperature rises, loss of strength and exhaustion appear. The body tries to compensate for the lack of defense cells, resulting in an enlarged spleen. This condition is very dangerous and requires identification of the cause and treatment.

Important: chronic fatigue or other conditions that have been bothering you for a long time cannot be ignored. They often arise due to a decrease protective forces body.

Excess white blood cells

The number of leukocytes above 9*10 9 /l is considered to be above normal and is called leukocytosis. Physiological enlargement, which does not require treatment, can be caused by food intake, physical activity, some hormonal surges (pregnancy, premenstrual period).

TO pathological conditions lead following reasons leukocytosis:

1. Infectious diseases.
2. Inflammatory processes of microbial and non-microbial etiology.
3. Blood loss.
4. Burns.

Treatment for this condition may include the following groups of drugs:

1. Antibiotics. They help eliminate the infection that caused leukocytosis and prevent complications.
2. Steroid hormones. Quickly and effectively relieve inflammation, which leads to a decrease in the production of leukocytes.
3. Antihistamines. Also help reduce inflammation.

The treatment tactics for any changes in the leukocyte formula depend on the cause that caused them.

Important: minor changes in the leukocyte formula may be temporary and even considered normal. Strong discrepancies with acceptable values ​​or lack of changes during repeated analyzes should be alarming.

Children are taught about the importance of leukocytes at school. This topic is not an exaggeration. Good immunity ensures health and good quality life of every person. To determine the state of the immune system, you can take a blood test during the absence of illness. A competent doctor will help you interpret the results correctly.

Video - What does an increase in leukocytes in a blood test mean?

A person performs several important tasks and are considered one of the most significant cells. They differ from other blood components by the absence of color and the presence of a nucleus. Translated from Greek language this word refers to white cells. The primary task of these cells is to absorb and destroy foreign organisms that have entered the human body.

What are they for?

The functions of leukocytes in the blood are to provide reliable protection against various bacteria and foreign bodies. Most white blood cells are produced by red bone marrow from stem cells. Leukocytes differ from each other and can have homogeneous or granular cytoplasm.

As soon as foreign organisms enter the human body, white blood cells surround them and absorb them. In this case, leukocytes begin to gradually increase and then are destroyed. If this happens, substances are released that attract new leukocytes to the site of introduction of a foreign body into the body, which causes limited inflammatory reaction. The result is swelling of the skin, redness or a local increase in body temperature. Pus on the surface of a wound or pimple appears due to the destruction of a large number of these blood cells.

Each type of these cells has the ability to actively move and can pass through the capillary wall into the tissue in order to destroy pathogenic internal or external agents. This process is called phagocytosis.

Types of white blood cells

All white blood cells are divided among themselves according to the following characteristics:

• appearance;
• origin;
• action.

Depending on this, the following types of leukocytes are distinguished:

• eosinophils;
• basophils;
• monocytes;
• neutrophils;
• lymphocytes.

Quantity various types leukocytes in the blood may change. A change in the leukocyte formula can be a symptom of some serious diseases.

Eosinophils help eliminate excess histamine, which is released during allergic reaction. An increase in eosinophils may occur with bronchial asthma, infection with worms, tumor processes and leukemia. Basophils play a significant role in the development of inflammation, their level increases with lymphogranulomatosis, an allergic reaction or decreased performance thyroid gland. Monocytes play the role of orderlies (capable of phagocytosis), their number increases with systemic lupus erythematosus, leukemia or rheumatoid arthritis. Neutrophils provide reliable protection from infection, therefore an increase in the number of such cells indicates a sore throat, sepsis, abscess or pneumonia. Lymphocytes exercise control over their own and foreign cells, their content increases in whooping cough, leukemia, viral hepatitis and tuberculosis. If the number of such leukocytes decreases, one may suspect malignant tumor or severe viral pathology.

How many leukocytes should there be

The number of leukocytes present in the blood serum is an indicator of a person’s health status. Therefore, determining the level of these blood cells is mandatory laboratory analysis, which is prescribed to patients in hospitals or clinics. Even in a healthy person, the number of leukocytes is variable and can change under the influence of certain factors:

• pregnancy;
• hard physical labor;
• hot bath;
• menstrual bleeding;
• childbirth.

An upward deviation from these indicators (leukocytosis) may indicate the presence of a tumor in the human body or inflammatory process. A decrease in the number of white blood cells (leukopenia) is caused by:

• medicines;
• infections;
• anaphylactic shock.

After eating, the level of these cells can also change, so it is very important to take a blood test in the morning on an empty stomach. The norm for an adult and healthy person is considered to be a leukocyte content in 1 liter of blood serum from 4.0 to 9.0x10^9. For an infant this figure is 9.2-13.8x10^9, and for children from 1 to 3 years old 6-17x10^9. In children aged 4-10 years, the number of leukocytes in the blood should be 6.1-11.4x10^9.

The materials are published for informational purposes only and are not a prescription for treatment! We recommend that you consult a hematologist at your medical institution!

Leukocytes are round cells with a size of 7-20 microns, consisting of a nucleus, homogeneous or granular protoplasm. They are called white blood cells because of their lack of color. And also granulocytes due to the presence of granules in the cytoplasm or agranulocytes due to the absence of granularity. IN calm state Leukocytes penetrate the walls of blood vessels and exit the bloodstream.

Because of their colorless cytoplasm, variable shape, and amoeboid movement, leukocytes are called white cells (or amoebae) that “float” in the lymph or blood plasma. The rate of leukocytes is within 40 µm/min.

Important! An adult in the morning on an empty stomach has a leukocyte ratio of 1 mm - 6000-8000. Their numbers change during the day due to other functional state. Sharp increase level in the blood of leukocytes is leukocytosis, a decrease in concentration is leukopenia.

Main functions of leukocytes

The spleen, lymph nodes, red marrow in the bones are organs where leukocytes are formed. Chemical elements irritate and force leukocytes to leave the bloodstream, penetrate the endothelium of the capillaries in order to quickly reach the source of irritation. These can be remnants of the vital activity of microbes, decaying cells, anything that can be called foreign bodies or antigen-antibody complexes. White cells use positive chemotaxis towards stimuli, i.e. they have a motor response.

• immunity is formed: specific and nonspecific;
• nonspecific immunity is formed with the participation of the resulting antitoxic substances and interferon;
• The production of specific antibodies begins.

Leukocytes are surrounded by their own cytoplasm and digested by special enzymes foreign body, which is called phagocytosis.

Important! One leukocyte digests 15-20 bacteria. Leukocytes are capable of secreting important protective substances that heal wounds and have a phagocytic reaction, as well as antibodies with antibacterial and antitoxic properties.

In addition to the protective function of leukocytes, they also have other important functional responsibilities. Namely:

• Transport. Amoeba-shaped white cells adsorb protease from the lysosome with peptidase, diastase, lipase, deoxyribronuclease and carry these enzymes on themselves to problem areas.
• Synthetic. With a deficiency in cells active substances: heparin, histamine and others, white cells synthesize biological substances that are missing for life and activity of all systems and organs.
• Hemostatic. Leukocytes help the blood to quickly clot with the leukocyte thromboplastins they secrete.
• Sanitary. White blood cells promote the resorption of cells in tissues that died during injuries, due to the enzymes that they carry from lysosomes.

How long does life last?

Leukocytes live for 2-4 days, and the processes of their destruction occur in the spleen. The short lifespan of leukocytes is explained by the entry into the body of many bodies that are accepted by the immune system as foreign. They are quickly absorbed by phagocytes. Therefore, their sizes increase. This leads to the destruction and release of a substance that causes local inflammation accompanied by edema, elevated temperature and hyperemia in the affected area.

These substances, which caused the inflammatory reaction, begin to attract active fresh leukocytes to the epicenter. They continue to destroy substances and damaged cells, grow and also die. The place where the dead white cells have accumulated begins to fester. Then lysosomal enzymes are activated, and the leukocyte sanitary function is activated.

Structure of leukocytes

Agranulocyte cells

Lymphocytes

Lymphoblast in the bone marrow produces a round shape and different sizes, lymphocytes with a large round nucleus. They belong to immunocompetent cells, therefore they mature according to a special process. They are responsible for creating immunity with a variety of immune responses. If their final maturation occurred in the thymus, then the cells are called T-lymphocytes, if in the lymph nodes or spleen - B-lymphocytes. The size of the first (80%) smaller size second cells (20% of them).

The lifespan of cells is 90 days. They actively participate in immune reactions and protect the body, while also using phagocytosis. Cells show resistance to all pathogenic viruses and pathological bacteria. nonspecific resistance- same impact.

Leukocytes(white blood cells) are blood cells containing a nucleus. In some leukocytes, the cytoplasm contains granules, which is why they are called granulocytes . Others have no granularity and are classified as agranulocytes. There are three forms of granulocytes. Those of them whose granules are stained with acidic dyes (eosin) are called eosinophils . Leukocytes, the granularity of which is susceptible to basic dyes - basophils . Leukocytes, the granules of which are stained with both acidic and basic dyes, are classified as neutrophils. Agranulocytes are divided into monocytes and lymphocytes. All granulocytes and monocytes are formed in the red bone marrow, and are called myeloid cells . Lymphocytes are also formed from stem cells bone marrow, but multiply in the lymph nodes, tonsils, appendix, thymus, and intestinal lymphatic plaques. These are lymphoid cells.

Neutrophils are in the vascular bed for 6-8 hours, and then pass into the mucous membranes. They make up the vast majority of granulocytes. The main function of neutrophils is to destroy bacteria and various toxins. They have the ability to chemotaxis and phagocytosis. Vasoactive substances released by neutrophils allow them to penetrate the capillary wall and migrate to the site of inflammation. The movement of leukocytes towards it occurs due to the fact that T-lymphocytes and macrophages located in the inflamed tissue produce chemoattractants. These are substances that stimulate their movement towards the site. These include arachidonic acid derivatives - leukotrienes, as well as endotoxins. The engulfed bacteria enter phagocytic vacuoles, where they are exposed to oxygen ions, hydrogen peroxide, and lysosomal enzymes. Important property neutrophils is that they can exist in inflamed and edematous tissues poor in oxygen. Pus mainly consists of neutrophils and their remains. Enzymes released during the breakdown of neutrophils soften the surrounding tissues. Due to this, a purulent focus is formed - an abscess.

Basophils contained in an amount of 0-1%. They remain in the bloodstream for 12 hours. Large granules of basophils contain heparin and histamine. Due to the heparin they secrete, lipolysis of fats in the blood is accelerated. On the basophil membrane there are E-receptors to which E-globulins attach. In turn, allergens can bind to these globulins. As a result, basophils release histamine. An allergic reaction occurs - hay fever(runny nose, itchy rash on the skin, redness, bronchospasm). In addition, basophil histamine stimulates phagocytosis and has an anti-inflammatory effect. Basophils contain platelet-activating factor, which stimulates platelet aggregation and the release of platelet-derived clotting factors. Highlight heparin And histamine, they prevent the formation of blood clots in the small veins of the lungs and liver.

Lymphocytes make up 20-40% of all leukocytes. They are divided into T and B lymphocytes. The former differentiate in the thymus, the latter - in various lymph nodes. T cells are divided into several groups. Killer T cells destroy foreign antigen cells and bacteria. Helper T cells are involved in the antigen-antibody reaction. Immunological memory T cells remember the structure of the antigen and recognize it. T-amplifiers stimulate immune reactions, and T-suppressors inhibit the formation of immunoglobulins. B lymphocytes make up a minority. They produce immunoglobulins and can turn into memory cells.

Percentage various forms leukocytes is called the leukocyte formula. Normally, their ratio constantly changes during diseases. Therefore, a study of the leukocyte formula is necessary for diagnosis.

Normal leukocyte formula.

Granulocytes:

Basophils 0-1%.

Eosinophils 1-5%.

Neutrophils.

Bands 1-5%.

Segmented 47-72%.

Agranulocytes.

Monocytes 2-10%.

Lymphocytes 20-40%.

Major infectious diseases are accompanied by neutrophilic leukocytosis, a decrease in the number of lymphocytes and eosinophils. If monocytosis then occurs, this indicates the body's victory over the infection. In chronic infections, lymphocytosis occurs.

Counting the total number of leukocytes produced in Goryaev's cell. Blood is drawn into a melangeur for leukocytes, and it is diluted 10 times with a 5% solution acetic acid tinted with methylene blue or gentian violet. Shake the melangeur for several minutes. During this time, acetic acid destroys red blood cells and the membrane of leukocytes, and their nuclei are stained with dye. The resulting mixture is filled into a counting chamber and leukocytes in 25 large squares are counted under a microscope. The total number of leukocytes is calculated using the formula:

X = 4000. A. i.p.

Where a is the number of leukocytes counted in squares;

b – the number of small squares in which the count was made (400);

c – blood dilution (10);

4000 is the reciprocal of the volume of liquid above a small square.

To study the leukocyte formula, a blood smear on a glass slide is dried and stained with a mixture of acidic and basic dyes. For example, according to Romanovsky-Giemsa. Then, under high magnification, the number of different forms is counted out of at least 100 counted.