Life flow. The meaning of blood

Blood is the main fluid of the body, continuously circulating through the vessels, penetrating into all organs and tissues, thereby providing them with oxygen and necessary nutrients. What does it consist of? – Let’s look at this in more detail in this publication.

Blood performs several vital functions in the body. It flows through arteries, veins and capillaries, delivers oxygen and nutrients to organs and tissues, removes carbon dioxide and other products of exchange. Blood elements, along with plasma proteins, provide immune protection against many pathogens, and also, being part of the blood coagulation system, are of utmost importance in stopping bleeding. In addition, blood is involved in maintaining the balance of the internal environment of the body (amount of water, osmotic pressure, mineral salts) and performs a thermoregulatory function.

Blood under a microscope

Blood consists of a liquid part, or plasma, cellular elements and substances dissolved in the plasma. The cellular elements of blood include red blood cells, white blood cells and platelets.

Their sizes are microscopically small. For example, red blood cells have the shape of biconcave disks with a diameter of 8 microns (microns) and a maximum thickness of 2 microns (1 micron is equal to 0.001 mm).

Red blood cells

Red blood cells are the most numerous of all types of blood cells, which normally constitute slightly less than half of the total blood volume. These cells contain hemoglobin, which carries oxygen to all organs and tissues. It is worth separately pointing out that the carbon dioxide formed in the cells is carried away by red blood cells back to the lungs, where it is excreted from the body. Hemoglobin is a protein that easily attaches and detaches molecules of oxygen and carbon dioxide. Hemoglobin that has added oxygen - oxyhemoglobin - is bright red, which causes the red color of the blood flowing through the arteries. After the absorption of oxygen by the tissues of the body and the binding of hemoglobin with carbon dioxide, the blood already acquires a dark red tint (it is this blood that flows through the veins).

A significant decrease in the number of red blood cells, a change in their shape, as well as insufficient hemoglobin content in them are characteristic features anemia,” note immunologists.

White blood cells

Leukocytes are larger in size than red blood cells. Moreover, they can perform the so-called. amoeboid movements (by protruding and then retracting their body in the form of outgrowths) and thus penetrate the wall blood vessels and move in intercellular spaces.

Leukocytes have a nucleus of different shapes, and in the cytoplasm of some of them there is a specific granularity (granulocytes), while others do not have such granularity (agranulocytes). Agranulocytes include lymphocytes and monocytes, granulocytes include neutrophils, eosinophils and basophils.

Neutrophils are the most numerous type of leukocytes. Note that these cells perform a protective function: when foreign substances, including pathogenic microbes, enter the body, they, as if on an alarm signal, penetrate the walls of the capillaries and move to the source of damage. Here, white blood cells surround the foreign substance, then absorb and digest it. This process is called phagocytosis. In this case, pus is formed at the site of inflammation, consisting of a large number of dead white blood cells.

Eosinophils are named for their ability to stain pink when the dye eosin is added to the blood. They make up 1-4% of the total number of leukocytes. Their main function is protection against bacteria and participation in allergic reactions. With the development of infectious diseases, special protective formations are formed in the blood plasma - antibodies, which neutralize the effect of a foreign antigen. This releases a chemical, histamine, which causes local allergic reaction. Eosinophils reduce its effect, and after suppressing the infection, relieve signs of inflammation.

Blood is the key fluid of the body. Its fundamental function is to provide the body with oxygen and other important substances, elements involved in the process of life. Plasma, a component of blood, and cellular components are divided by meaning and type. Cell groups are divided into the following groups: red blood cells (erythrocytes), white cells (leukocytes) and platelets.

In an adult, blood volume is calculated taking into account his body weight: approximately 80 ml per 1 kg (for men), 65 ml per 1 kg (for women). Most of the total blood is plasma, red cells occupy a significant proportion of the remaining amount.

How does blood work?

The simplest organisms living in the sea exist without blood. Their blood takes over the role sea ​​water, which through the tissues saturates the body with all the necessary components. Products of decomposition and exchange also come out with water.

The human body is more complex, therefore it cannot function by analogy with the simplest. That is why nature has endowed humans with blood and a system for distributing it throughout the body.

Blood is responsible not only for the function of supplying nutrients to systems, organs, tissues, and the release of residual waste products, but also controls the temperature balance of the body, supplies hormones, and protects the body from the spread of infections.

Nevertheless, the delivery of nutrients is a key function performed by the blood. It is the circulatory system that has a connection with all digestive and respiratory processes, without which life is impossible.

Basic functions

Blood in the human body performs the following vital tasks.

1. Blood carries out a transport function, which is to supply the body with all the necessary elements and its purification from other substances. Transport function also divided into several others: respiratory, nutritional, excretory, humoral.
2. Blood is also responsible for maintaining a stable body temperature, that is, it plays the role of a thermostat. This feature has special meaning– some organs need to be cooled, and some need to be warmed.
3. The blood contains leukocytes and antibodies that perform a protective function.
4. The role of blood is also to stabilize many constant quantities in the body: osmotic pressure, pH level, acidity, and so on.
5. Another function of blood is to provide water-salt metabolism what is happening to her tissues.

Red blood cells

Red blood cells make up slightly more than half of the body's total blood volume. The importance of red blood cells is determined by the hemoglobin content in these cells, which provides oxygen to all systems, organs and tissues. It is worth noting that the carbon dioxide formed in the cells is carried back to the lungs by red blood cells for further release from the body.

The role of hemoglobin is to facilitate the addition and detachment of oxygen molecules and carbon dioxide. Oxyhemoglobin has a bright red color and is responsible for the addition of oxygen. When the tissues of the human body absorb oxygen molecules and hemoglobin forms a compound with carbon dioxide, the blood becomes darker in color. A significant decrease in the number of red blood cells, their modification and lack of hemoglobin in them are considered the main symptoms of anemia.

Leukocytes

White blood cells are larger than red blood cells. In addition, white blood cells can move between cells by protruding and retracting their bodies. White cells differ in the shape of the nucleus, while the cytoplasm of individual white cells is characterized by granularity - granulocytes, others do not differ in granularity - agranulocytes. Granulocytes include basophils, neutrophils and eosinophils; agranulocytes include monocytes and lymphocytes.

The most numerous type of leukocytes are neutrophils; they perform the protective function of the body. When foreign substances, including microbes, enter the body, neutrophils are also sent to the source of damage to neutralize it. This value of white blood cells is extremely important for human health.

The process of absorption and digestion of foreign substances is called phagocytosis. The pus that forms at the site of inflammation is a lot of dead leukocytes.

Eosinophils are so named due to their ability to acquire a pinkish tint when eosin, a dye, is added to the blood. Their content is approximately 1-4% of the total number of leukocytes. The main function of eosinophils is to protect the body from bacteria and determine reactions to allergens.

When infections develop in the body, antibodies are formed in the plasma that neutralize the effect of the antigen. During this process, histamine is produced, which causes a local allergic reaction. Its effect is reduced by eosinophils, and after the infection is suppressed, they eliminate the symptoms of inflammation.

Plasma

Plasma consists of 90-92% water, the rest is represented by salt compounds and proteins (8-10%). There are other nitrogenous substances in plasma. These are mainly polypeptides and amino acids that come from food and help cells in the body produce proteins on their own.

In addition, plasma contains nucleic acids and protein breakdown products, which must be cleansed from the body. Plasma also contains nitrogen-free substances - lipids, neutral fats and glucose. About 0.9% of all components in plasma are minerals. Plasma also contains all kinds of enzymes, antigens, hormones, antibodies, etc., which can be important for the human body.

Hematopoiesis

Hematopoiesis is the formation of cellular elements that occurs in the blood. Leukocytes are formed by a process called leukopoiesis, red blood cells - erythropoiesis, platelets - thrombopoiesis. The growth of blood cells occurs in the bone marrow, which is located in flat and tubular bones. Lymphocytes are formed, in addition to bone marrow, also in the intestinal lymph tissue, tonsils, spleen and lymph nodes.

Circulating blood always maintains a relatively stable volume, the function it performs is so important, despite the fact that something is constantly changing inside the body. For example, fluid is constantly absorbed from the intestines. And if water enters the blood in a large volume, then some of it immediately leaves with the help of the kidneys, the other part enters the tissues, from where over time it again penetrates into the bloodstream and is completely released through the kidneys.

If not enough fluid enters the body, the blood receives water from the tissues. In this case, the kidneys do not function at full capacity, they collect less urine, and little water is excreted from the body. If the total blood volume decreases by at least a third in a short period of time, say, bleeding occurs or as a result of an injury, then this is already life-threatening.

Internal environment of the body. Cells, tissues and organs of the body can exist and function normally only under certain conditions that are created by the internal environment to which they have adapted during evolutionary development. The internal environment provides the opportunity for the entry into cells of substances necessary for their vital activity and the removal of metabolic products. By maintaining a certain composition of the internal environment, cells function under constant conditions. Maintaining a constant internal environment is called homeostasis.

Maintained in the body at a relatively constant level blood pressure, body temperature, osmotic pressure of blood and tissue fluid, their content of proteins and sugar, sodium, potassium, calcium, chlorine ions, etc.

Homeostasis is maintained by complexes of dynamic processes. A significant role in maintaining homeostasis belongs to regulatory systems- nervous and endocrine. Maintaining a constant internal environment is possible only with the functioning of the respiratory system, cardiovascular system, digestive and excretory organs.

The internal environment of the human body is blood, lymph and tissue fluid.

The meaning of blood. Nutrients and blood oxygen entering the body are distributed throughout the body and from the blood enter the lymph and tissue fluid. IN reverse order the products of exchange are separated. Being in continuous movement, blood ensures the constancy of the composition of tissue fluid in direct contact with cells. Consequently, blood plays a vital role in ensuring the constancy of the internal environment. The absorption of oxygen by the blood and the removal of carbon dioxide is called respiratory function blood. In the lungs, the blood is enriched with oxygen and releases carbon dioxide, which is then released into the environment with exhaled air. Flowing through the capillaries of various tissues and organs, blood gives them oxygen and absorbs carbon dioxide.

Blood carries out transport function- transfer of nutrients from the digestive organs to the cells and tissues of the body and removal of decay products. During the process of metabolism, substances are constantly formed in cells that can no longer be used for the needs of the body, and often turn out to be harmful to it. From the cells, these substances enter the tissue fluid and then into the blood. These products are delivered by blood to the kidneys, sweat glands, lungs and excreted from the body.

Blood performs protective function. Toxic substances or microbes may enter the body. They are destroyed and destroyed by certain blood cells or glued together and rendered harmless by special protective substances.

Blood is involved in humoral regulation body activity, performs thermoregulatory function cooling energy-consuming organs and warming organs that lose heat.

Quantity and composition of blood. The amount of blood in the human body changes with age. Children have more blood relative to body weight than adults (Table 15). In newborns, blood makes up 14.7% of the mass, in children one year old - 10.9%, in children 14 years old - 7%. This is due to a more intense metabolism in the child’s body. In adults weighing 60-70 kg, the total amount of blood is 5-5.5 liters.

Usually not all the blood circulates in the blood vessels. Some of it is in blood depots. The role of blood depot is performed by the vessels of the spleen, skin, liver and lungs. With increased muscle work, with the loss of large amounts of blood due to injuries and surgical operations In some diseases, blood reserves from the depot enter the general bloodstream. Blood depots are involved in maintaining a constant amount of circulating blood.

Blood plasma. Arterial blood is a red opaque liquid. If you take measures to prevent blood clotting, then during settling, or even better during centrifugation, it will clearly separate into two layers. Top layer- slightly yellowish liquid - plasma, the sediment is dark red. There is a thin light film at the boundary between the deposit and plasma. The sediment, together with the film, is formed by the formed elements of blood - erythrocytes, leukocytes and blood platelets - platelets. All blood cells live certain time, after which they are destroyed. IN hematopoietic organs(bone marrow, lymph nodes, spleen) there is a continuous formation of new blood cells.

U healthy people the ratio between plasma and formed elements varies slightly (55% plasma and 45% formed elements). In children early age percentage shaped elements are slightly higher.

Plasma consists of 90-92% water, 8-10% consists of organic and inorganic compounds. The concentration of substances dissolved in a liquid creates a certain osmotic pressure. Since the concentration organic matter(proteins, carbohydrates, urea, fats, hormones, etc.) is small, osmotic pressure is determined mainly by inorganic salts.

The constancy of blood osmotic pressure has important for the functioning of body cells. The membranes of many cells, including blood cells, have selective permeability. Therefore, when placing blood cells in solutions with different concentrations salts, therefore, and with different osmotic pressures, serious changes can occur in blood cells.

Solutions that in their own way quality composition and salt concentrations correspond to the composition of the plasma, called physiological solutions. They are isotonic. Such fluids are used as blood substitutes for blood loss.

Osmotic pressure in the body is maintained at a constant level by regulating the flow of water and mineral salts and their release by the kidneys and sweat glands. The plasma also maintains a constant reaction, which is referred to as blood pH; it is determined by the concentration of hydrogen ions. The blood reaction is slightly alkaline (pH is 7.36). Maintaining a constant pH is achieved by the presence of buffer systems in the blood that neutralize excess acids and alkalis entering the body. These include blood proteins, bicarbonates, salts phosphoric acid. In the constancy of the blood reaction, an important role also belongs to the lungs, through which carbon dioxide is removed, and the excretory organs, which remove excess substances that have an acidic or alkaline reaction.

Formed elements of blood. Formed elements that determine the possibility of performing the most important function of blood - respiratory - red blood cells(red blood cells). The number of red blood cells in the blood of an adult is 4.5-5.0 million per 1 mm 3 of blood.

If we placed all human red blood cells in one row, we would get a chain about 150 thousand km long; if you put red blood cells one on top of the other, a column would be formed with a height exceeding the length of the equator of the globe (50-60 thousand km). The number of red blood cells is not strictly constant. It can increase significantly with a lack of oxygen at high altitudes and during muscular work. People living in high mountain areas have approximately 30% more red blood cells than residents sea ​​coast. When moving from lowland to highland areas, the number of red blood cells in the blood increases. When the need for oxygen decreases, the number of red blood cells in the blood decreases.

Exertion by red blood cells respiratory function due to the presence of a special substance in them - hemoglobin, which is an oxygen carrier. Hemoglobin contains divalent iron, which, when combined with oxygen, forms a weak compound oxyhemoglobin. In capillaries, such oxyhemoglobin easily breaks down into hemoglobin and oxygen, which is absorbed by cells. There, in the tissue capillaries, hemoglobin combines with carbon dioxide. This compound breaks down in the lungs, carbon dioxide is released into the air.

The hemoglobin content in the blood is measured either in absolute values ​​or as a percentage. The presence of 16.7 g of hemoglobin in 100 ml of blood is taken as 100%. An adult's blood usually contains 60-80% hemoglobin. The hemoglobin content depends on the number of red blood cells in the blood, nutrition, in which the presence of iron necessary for the functioning of hemoglobin is important, staying on fresh air and other reasons.

The content of red blood cells in 1 mm 3 of blood changes with age. In the blood of newborns, the number of red blood cells can exceed 7 million per 1 mm3; the blood of newborns is characterized by a high hemoglobin content (over 100%). By the 5-6th day of life, these indicators decrease. Then, by 3-4 years, the number of hemoglobin and red blood cells increases slightly; at 6-7 years, there is a slowdown in the increase in the number of red blood cells and hemoglobin content; from the age of 8, the number of red blood cells and the amount of hemoglobin increase again.

A decrease in the number of red blood cells below 3 million and the amount of hemoglobin below 60% indicates the presence of an anemic condition (anemia).

If the blood is protected from clotting and left for several hours in the capillary tubes, the red blood cells begin to settle due to gravity. They settle at a certain rate; in men 1-10 mm/h, in women - 2-15 mm/h. With age, the erythrocyte sedimentation rate changes. Erythrocyte sedimentation rate (ESR) is widely used as an important diagnostic indicator, indicating the presence of inflammatory processes and other pathological conditions. Therefore, knowledge is important standard indicators ESR in children of different ages.

In newborns, the erythrocyte sedimentation rate is low (1 to 2 mm/h). In children under 3 years of age, the ESR value ranges from 2 to 17 mm/h. At the age of 7 to 12 years, the ESR value does not exceed 12 mm/h.

Leukocytes- white blood cells. The most important function! Leukocytes provide protection against microorganisms and toxins entering the blood. Protective function leukocytes is associated with their ability to move independently to the area where microbes or a foreign body have penetrated. Having approached them, leukocytes envelop them, draw them inside and digest them. The phenomenon of absorption of microorganisms by leukocytes is called phagocytosis.

Fig.5. Phagocytosis of bacteria by leukocyte (three final stages)

It was first discovered by the outstanding Russian scientist I.I. Mechnikov. An important factor, defining protective properties leukocytes is also their participation in immune mechanisms.

Based on their shape, structure and function, different types of leukocytes are distinguished. The main ones are: lymphocytes, monocytes, neutrophils. Lymphocytes are formed mainly in the lymph nodes. They are not capable of phagocytosis, but by producing antibodies, they play an important role in providing immunity. Neutrophils are produced in the red bone marrow: they are the most numerous leukocytes and play a major role in phagocytosis. One neutrophil can absorb 20-30 microbes. After an hour, all of them are digested inside the neutrophil. This occurs with the participation of special enzymes that destroy microorganisms. If the foreign body is larger in size than a leukocyte, then groups of neutrophils accumulate around it, forming a barrier.

Development of immunity in ontogenesis. Unlike the system specific immunity nonspecific protection factors in newborns are well expressed. They are formed earlier than specific ones and take on the main function of protecting the body of the fetus and newborn. IN amniotic fluid and in the blood of the fetus it is noted high activity lysozyme, which persists until the birth of the child and then decreases. The ability to form interferon immediately after birth is high; it decreases throughout the year, but gradually increases with age and reaches a maximum by 12-18 years.

Newborn receives from mother significant amount gamma globulins. This nonspecific protection turns out to be sufficient during the initial collision of the organism with the microflora of the environment. In addition, the newborn has “ physiological leukocytosis“- the number of leukocytes is 2 times higher than in an adult, as a natural preparation of the body for new living conditions. However, numerous lymphocytes of newborns are represented by immature forms and are not able to synthesize the required amount of globulins and interferon. Phagocytes are also not active enough. As a result of this children's body responds to the penetration of microorganisms with generalized inflammation. Often this reaction is caused by household microflora that is safe for adults. In the body of a newborn, specific immune systems are not formed, there is no immune memory, and nonspecific mechanisms are also not yet mature. That's why feeding is so important mother's milk, which contains immunoreactive substances. Between 3 and 6 months of age immune system The child already reacts to the invasion of microorganisms, but virtually no immune memory is formed. At this time, vaccinations are ineffective, the disease does not leave behind lasting immunity. The second year of a child’s life is identified as a “critical” period in the development of immunity. At this age, opportunities expand and efficiency increases. immune reactions, however the system local immunity is not yet sufficiently developed and children are susceptible to respiratory viral infections. At the age of 5-6 years, nonspecific cellular immunity matures. Formation of one’s own nonspecific humoral system immune defense ends in the 7th year of life, resulting in respiratory morbidity viral infections decreases.

Peculiarities hormonal regulation functions. Regulation of functions in the human body is carried out through the nervous and humoral pathways. Nervous regulation is determined by the speed of nerve impulse conduction, humoral regulation is determined by the speed of blood movement through the vessels or the rate of diffusion of molecules chemicals into the intercellular fluid. Nervous regulation is faster, so it is the leading one in the body, but it also has its drawbacks. The nerve impulse leads only to a short-term change in the polarization of the cell membrane. For long-term effects, nerve impulses must arrive one after another, which leads to fatigue nerve centers, as a result of which the nervous influence weakens. With humoral influence, information reaches all cells, although it is perceived only by the cell that has a specialized receptor. An information molecule, having reached such a cell, attaches to its membrane, changes its properties and remains there until the expected result is achieved, after which special mechanisms destroy this molecule. Thus, if control influence should be urgent and short-term - the advantage is for nervous regulation, and if long-lasting - for humoral regulation. Therefore, in the body there are both nervous and humoral modes of regulation, which act in concert depending on the conditions.

Among biologically active substances For the physiological regulation of body functions, mediators, hormones, enzymes and vitamins are most important. Mediators are represented by non-protein substances that are secreted by the endings nerve cells as a result of the passage of a nerve impulse. The most common mediators are acetylcholine, adrenaline, norepinephrine, dopamine and gamma-aminobutyric acid.

Capable of phagocytosis and monocytes- cells formed in the spleen and liver.

The blood of an adult contains 4000-9000 leukocytosis in 1 μl. There is a certain relationship between different types leukocytes, expressed as a percentage, the so-called leukocyte formula. At pathological conditions changes as total number leukocytes and leukocyte formula.

The number of leukocytes and their ratio change with age. A newborn has significantly more leukocytes than an adult (up to 20 thousand in 1 mm 3 of blood). In the first day of life, the number of leukocytes increases (resorption of decay products of the child’s tissues, tissue hemorrhages that are possible during childbirth occurs) to 30 thousand per 1 mm 3 of blood.

Starting from the second day of life, the number of leukocytes decreases and by the 7-12th day reaches 10-12 thousand. This number of leukocytes remains in children of the first year of life, after which it decreases and by the age of 13-15 reaches the values ​​of an adult. The younger the child is, the more immature forms of leukocytes his blood contains.

Leukocyte formula in the first years of a child's life is characterized by increased content lymphocytes and a reduced number of neutrophils. By 5-6 years, the number of these formed elements levels off, after which the percentage of neutrophils steadily increases, and the percentage of lymphocytes decreases. The low content of neutrophils, as well as their insufficient maturity, partly explains the greater susceptibility of children younger ages to infectious diseases. In addition, the phagocytic activity of neutrophils in children of the first years of life is the lowest.

Platelets and blood clotting. Platelets (blood plates) are the smallest of the formed elements of blood. Their number varies from 200 to 400 thousand in 1 mm 3 (µl). There are more of them during the day and fewer at night. After a hard muscle work quantity blood platelets increases by 3-5 times.

Platelets are produced in the red bone marrow and spleen. The main function of platelets is associated with their participation in blood clotting. When blood vessels are injured, platelets are destroyed. At the same time, substances necessary for the formation are released into the plasma. blood clot - blood clot

IN normal conditions blood in intact blood vessels does not clot due to the presence of anti-clotting factors in the body. In some inflammatory processes accompanied by damage inner wall vessel, and when cardiovascular diseases Blood clotting occurs and a blood clot forms.

Normal operation blood circulation, preventing both blood loss and blood clotting inside the vessel, is achieved by a certain balance of two systems existing in the body - coagulation and anti-coagulation.

Blood clotting in children in the first days after birth is slow, this is especially noticeable on the 2nd day of the child’s life. From the 3rd to the 7th day of life, blood clotting accelerates and approaches the adult norm. In children of preschool and school age, blood clotting time has wide individual variations. On average, the beginning of coagulation in a drop of blood occurs after 1-2 minutes, the end of coagulation occurs after 3-4 minutes.

Blood groups and blood transfusion. When transfusing blood from one person to another, blood types must be taken into account. This is due to the fact that the formed elements of blood - red blood cells - contain special substances antigens, or agglutinogens, and in plasma proteins agglutinins, with a certain combination of these substances, red blood cells stick together - agglutination. The classification of groups is based on the presence of certain agglutinins and agglutinogens in the blood. There are two types of agglutinogens in erythrocytes, they are designated by the letters of the Latin alphabet A, B. In erythrocytes they can be present one at a time, together, or absent. There are also two agglutinins (gluing red blood cells) in plasma, they are designated by the Greek letters a and p. The blood of different people contains either one, two, or no agglutinins. Agglutination occurs when agglutinogens from the donor meet agglutinins of the same name from the recipient (the person receiving the blood transfusion). It is clear that in the blood of every person there are different agglutinins and agglutinogens. If agglutinin A interacts with agglutinogen A or agglutinin B with agglutinogen B, agglutination occurs, threatening the body with death. People have 4 combinations of agglutinogens and agglutinins and, accordingly, 4 blood groups are distinguished: Group I - plasma contains agglutinins a and b, erythrocytes do not have agglutinogens; Group II - plasma contains agglutinin B, and erythrocytes contain agglutinogen A; Group III - agglutinin A is found in plasma, agglutinogen B is found in erythrocytes; Group IV - there are no agglutinins in plasma, but erythrocytes contain agglutinogens A and B.

Approximately 40% of people have group I, 39% have group II, 15% have group III, and 6% have group IV.

There are also other agglutinogens in the blood that are not included in the group classification system. Among them, one of the most significant, which must be taken into account when transfusing, is Rh factor. 85% of people have it (Rh-positive), 15% do not have this factor in their blood (Rh-negative). When Rh-positive blood is transfused into a Rh-negative person, Rh-negative antibodies appear in the blood, and with repeated transfusion of Rh-positive blood, serious complications in the form of agglutination. The Rh factor is especially important to consider during pregnancy. If the father is Rh positive and the mother is Rh negative, the fetal blood will be Rh positive because it dominant trait. Fetal agglutinogens, entering the mother's blood, will cause the formation of antibodies (agglutinins) to Rh-positive red blood cells. If these antibodies penetrate the fetal blood through the placenta, agglutination will occur and the fetus may die. Since the amount of antibodies in the mother's blood increases with repeated pregnancies, the danger to children increases. In this case, either a woman with Rh negative blood Anti-Rhesus gammaglobulin is administered in advance, or a replacement blood transfusion is given to the newly born child.

Blood transfusion is one of the treatment methods that is indispensable for acute blood loss(injuries, operations). Blood transfusions are often used in cases of shock and various diseases, where it is necessary to increase the body's resistance. A transfusion can be performed directly from the person giving blood (donor) to the person receiving it (recipient). However, it is more convenient to use donor canned blood, since blood will always be available required group. Donation has become widespread in our country. Blood is taken only from persons who are not sick with any infectious disease.

Anemia, its prevention. Anemia - sharp decline blood hemoglobin and a decrease in the number of red blood cells.

Various kinds diseases and especially unfavorable living conditions for children and adolescents lead to anemia. Anemia is accompanied by headaches, dizziness, fainting, and has a negative impact on performance and learning success. In addition, in anemic students, the body's resistance sharply decreases and they often get sick for a long time.

First preventive measure against anemia are: proper organization daily routine, rational nutrition, rich in mineral salts and vitamins, strict rationing of educational, extracurricular, labor and creative activity so that overwork does not develop, the required amount of daily allowance motor activity in open air conditions and reasonable use natural factors nature.

Blood, its meaning, composition and general properties.

Blood, together with lymph and interstitial fluid, makes up the internal environment of the body in which the vital activity of all cells and tissues takes place.

Peculiarities:

1) is a liquid medium containing formed elements;

2) is in constant motion;

3) the components are mainly formed and destroyed outside it.

Blood together with hematopoietic and blood-destructive organs (bone marrow, spleen, liver and lymph nodes) makes up the entire blood system. The activity of this system is regulated by neurohumoral and reflex pathways.

Due to circulation in the vessels, blood performs the following in the body: essential functions:

14. Transport - blood transports nutrients (glucose, amino acids, fats, etc.) to cells, and metabolic end products (ammonia, urea, uric acid etc.) - from them to the excretory organs.

15. Regulatory – carries out the transfer of hormones and other physiological active substances that affect various organs and fabrics; regulation of the constancy of body temperature - transfer of heat from organs with intensive heat production to organs with less intense heat production and to places of cooling (skin).

16. Protective - due to the ability of leukocytes to phagocytose and the presence in the blood of immune bodies that neutralize microorganisms and their poisons, destroying foreign proteins.

17. Respiratory - delivery of oxygen from the lungs to the tissues, carbon dioxide - from the tissues to the lungs.

In an adult, the total amount of blood is 5-8% of body weight, which corresponds to 5-6 liters. Blood volume is usually denoted in relation to body weight (ml/kg). On average, it is 61.5 ml/kg in men, and 58.9 ml/kg in women.

Not all blood circulates in the blood vessels at rest. About 40-50% of it is located in blood depots (spleen, liver, blood vessels of the skin and lungs). Liver – up to 20%, spleen – up to 16%, subcutaneous vascular network – up to 10%

Blood composition. Blood consists of formed elements (55-58%) - red blood cells, leukocytes and platelets - and a liquid part - plasma (42-45%).

Red blood cells– specialized anucleate cells with a diameter of 7-8 microns. They are formed in the red bone marrow and destroyed in the liver and spleen. There are 4–5 million red blood cells in 1 mm3 of blood. The structure and composition of red blood cells are determined by the function they perform - transport of gases. The shape of red blood cells in the form of a biconcave disk increases contact with environment, thereby helping to accelerate gas exchange processes.

Hemoglobin has the property of easily binding and removing oxygen. By attaching it, it becomes oxyhemoglobin. Giving up oxygen in places with low oxygen content, it turns into reduced (reduced) hemoglobin.

Skeletal and cardiac muscles contain muscle hemoglobin - myoglobin (an important role in supplying oxygen to working muscles).

Leukocytes, or white blood cells, according to morphological and functional characteristics, are ordinary cells containing a nucleus and protoplasm of a specific structure. They are formed in the lymph nodes, spleen and bone marrow. There are 5-6 thousand leukocytes in 1 mm 3 of human blood.

Leukocytes are heterogeneous in their structure: in some of them the protoplasm has a granular structure (granulocytes), in others there is no granularity (agronulocytes). Granulocytes make up 70-75% of all leukocytes and are divided depending on the ability to stain with neutral, acidic or basic dyes into neutrophils (60-70%), eosinophils (2-4%) and basophils (0.5-1%). Agranulocytes – lymphocytes (25-30%) and monocytes (4-8%).

Functions of leukocytes:

1) protective (phagocytosis, antibody production and destruction of toxins protein origin);

2) participation in splitting nutrients

Platelets- plasma formations oval or round shape with a diameter of 2-5 microns. In the blood of humans and mammals they do not have a nucleus. Platelets are formed in the red bone marrow and in the spleen, and their number ranges from 200 thousand to 60 thousand in 1 mm3 of blood. They play an important role in the blood clotting process.

The main function of leukocytes is immunogenesis (the ability to synthesize antibodies or immune bodies, which neutralize microbes and their metabolic products). Leukocytes, having the ability for amoeboid movements, adsorb antibodies circulating in the blood and, penetrating through the walls of blood vessels, deliver them to the tissues to the sites of inflammation. Neutrophils containing large number enzymes, have the ability to capture and digest pathogenic microbes (phagocytosis - from the Greek Phagos - devouring). Body cells that degenerate in areas of inflammation are also digested.

Leukocytes are also involved in recovery processes after tissue inflammation.

Protecting the body from bleeding. This function is carried out due to the ability of blood to clot. The essence of blood clotting is the transition of fibrinogen protein dissolved in plasma into undissolved protein - fibrin, which forms threads glued to the edges of the wound. Blood clot. (thrombus) blocks further bleeding, protecting the body from blood loss.

The transformation of fibronogen into fibrin is carried out under the influence of the enzyme thrombin, which is formed from the protein prothrombin under the influence of thromboplastin, which appears in the blood during the destruction of platelets. The formation of thromboplastin and the conversion of prothrombin to thrombin occur with the participation of calcium ions.

Blood groups. The doctrine of blood groups arose in connection with the problem of blood transfusion. In 1901, K. Landsteiner discovered agglutinogens A and B in human erythrocytes. Agglutinins a and b (gamma globulins) are found in blood plasma. According to the classification of K. Landsteiner and J. Jansky, depending on the presence or absence of agglutinogens and agglutinins in the blood of a particular person, 4 blood groups are distinguished. This system is called ABO. Blood groups in it are designated by numbers and those agglutinogens that are contained in the red blood cells of this group.

Group antigens are hereditary innate properties blood, which do not change throughout a person’s life. There are no agglutinins in the blood plasma of newborns. They are formed during the first year of a child’s life under the influence of substances supplied with food, as well as those produced by intestinal microflora, to those antigens that are not in his own red blood cells.

Group I (O) – there are no agglutinogens in erythrocytes, plasma contains agglutinins a and b

Group II (A) – erythrocytes contain agglutinogen A, plasma contains agglutinin b;

Group III (B) – agglutinogen B is found in erythrocytes, agglutinin a is found in plasma;

Group IV (AB) – agglutinogens A and B are found in erythrocytes, there are no agglutinins in plasma.

Among residents of Central Europe, blood group I occurs in 33.5%, group II – 37.5%, group III – 21%, group IV – 8%. 90% of Native Americans have blood type I. More than 20% of the population of Central Asia have blood type III.

Agglutination occurs when an agglutinogen with the same agglutinin is found in a person’s blood: agglutinogen A with agglutinin a or agglutinogen B with agglutinin b. When transfusion of incompatible blood results from agglutination and subsequent hemolysis, transfusion shock develops, which can lead to death. Therefore, a rule was developed for transfusion of small amounts of blood (200 ml), which took into account the presence of agglutinogens in the donor’s red blood cells and agglutinins in the recipient’s plasma. Donor plasma was not taken into account because it was highly diluted by recipient plasma.

According to this rule Group I blood can be transfused to people with all blood groups (I, II, III, IV), therefore people with the first blood group are called universal donors. Group II blood can be transfused to people with blood groups II and IY, blood III groups - III and IV. Group IV blood can only be transfused to people with the same blood group. At the same time, people with blood group IV can receive any blood transfusion, which is why they are called universal recipients. If large amounts of blood transfusion are necessary, this rule cannot be used.

Blood is life; Without it, the body cannot function. Driven by the heart pump, it runs through an extensive network of arteries and veins, carrying oxygen and nutrients to cells and removing harmful waste.

We often hear the expression “life-giving blood” without thinking about its real meaning. Meanwhile, blood is literally the carrier of life. Circulating throughout the body, it, like a reliable delivery service, supplies living cells with nutrients necessary for energy production and raw materials for growth, vital activity and repair of damaged tissues. In addition, like a diligent scavenger, she cleans out waste from cells, especially carbon dioxide, which is formed during the processing of food into energy. Blood also has a third, police function - to destroy or neutralize foreigners such as bacteria and other microorganisms that have entered the body.

Blood makes up approximately 1/14 of the total body weight, and its amount depends on our physical dimensions. The average man has about 5 liters of blood, a woman a little less. Approximately 45% of the total blood volume is various types cells, each of which performs its own specific tasks. The most important of them are red (erythrocytes) and white (leukocytes) blood cells.

All these tiny cells float freely in a substance called plasma. In total, the body contains about 3 liters of this thick liquid of light amber color, consisting mainly of water with small admixtures of proteins, salts and glucose. Its main purpose is to fold transport system for erythrocytes and leukocytes.

Most of the nutrients consumed with food are absorbed into the blood through the walls of the small intestine. At the same time, some are immediately transferred into cells, others are first processed by special “chemical factories” - the liver and other glands - before the body can use them. However, in both cases they travel through the circulatory system.

Blood circulates in the body through closed system tubes or blood vessels - arteries, veins and capillaries. Arteries and veins are waterproof, but the walls of the thinnest capillaries, through which blood flows from arteries to veins and back, allow water, glucose, amino acids and other substances to pass through so that they can enter living tissues.

Water exchange in the capillaries occurs at a constant rate, so the total volume of blood remains unchanged. Water flushes waste products from cells to further removal from the body. The blood is constantly “washed” by the kidneys, which extract harmful substances from it and ultimately eliminate them in the urine.

The protein molecules in plasma are too large to penetrate the capillary walls. They are called albumins, globulins and fibrinogens. Most of all there is albumin in plasma, which maintains constant osmotic pressure of the blood. This pressure, against the pressure generated by the heart, sucks water and waste from the cells as blood is sent back through the veins.

Antibodies or special substances that neutralize infectious agents, consisting of gamma globulin proteins. They are produced by the spleen or lymph nodes and continue to circulate in the blood after defeat. primary infection, making us invulnerable to repeated attacks. Fibrinogen, like albumin, is produced by the liver and plays an important role in the blood clotting process.

Red blood cells owe their scarlet color to a pigment called hemoglobin. Each cell with a diameter of about 7.2 microns (0.0072 mm) is similar to a round pad with holes on the sides (hemoglobia captures oxygen from the lungs and distributes it throughout all the cells of the body. Oxygen is released, it turns from scarlet to dark red or purple. Then, Having picked up carbon dioxide from the cells, hemoglobin delivers it to the lungs, from where it is exhaled. Red blood cells are produced by the bone marrow and live for 4 months. Of the myriad of red blood cells, about 5 million die every second, disintegrating into pieces. constituent elements, some of which are used for the construction of new cells.

A lack of red blood cells leads to a number of ailments that have common name- anemia. The body cannot produce hemoglobin without iron, and although many people have sufficient reserves of this element, slow but constant bleeding, as, say, with a stomach ulcer, can cause anemia. Anemia is more common in women than in men, either due to malnutrition and heavy loads, or during pregnancy, when the mother’s body supplies the fetus with iron, without leaving it for its own needs.

White blood cells, or leukocytes, are also produced by the bone marrow. Spherical in shape, they are slightly larger than red blood cells and are the body's main weapon in the fight against disease. There are two main types of white blood cells. These are granulocytes, so named because they contain many granules randomly scattered inside the cell, and lymphocytes, which are produced by the lymphatic system and liver,

Attacking microorganisms that have penetrated into the forehead, granulocytes surround them and devour them. Like a rapid response squad, they are always ready for battle and multiply rapidly at the slightest infection or injury. Lymphocytes are more like a defensive patrol system and take longer to reorganize battle formations before attacking strangers. They are also involved in the production of antibodies. White blood cells circulate through the walls of capillaries and are not difficult to find in living tissues, whose health is vigilantly guarded.

Since during injury or illness the body increases its production of white blood cells by 3-4 times, a blood test is often done to make a diagnosis. A small portion of blood is examined and the number is calculated. different cells. Let's say, abdominal pain with unclear, but unpleasant symptoms may indicate either indigestion or appendicitis. If the content of leukocytes in the blood sample is increased, then this is most likely not appendicitis. Using a blood test, hemoglobin levels are determined, and to identify physical abnormalities use powerful ones in cells modern microscopes. Sometimes a test of the spray reveals a problem. This is a mixture of dead leukocytes and microorganisms absorbed by them. Leukocytes are even capable of destroying and expelling foreign bodies the size of a splinter or thorn from the body. Sometimes problems arise with the leukocytes themselves. When they are in excess in the body, they speak of high-quality leukemia. Highly sensitive to the effects of poisons and radiation, bone marrow can slow down the production of red and white blood cells, leading to a rare disease - aplastic anemia.

For any damage circulatory system internal or external bleeding opens. Big loss blood is very dangerous. A person can lose up to 15% of their blood without much harm, but exceeding this threshold often leads to death. Slow, prolonged bleeding leads to anemia, and rapid blood loss causes shock, in which the pressure drops so low that blood stops flowing to the heart,

The body has a special system that prevents excess blood loss. This is the coagulation mechanism. Bone marrow produces special cells - platelets, which are even smaller in size than red blood cells. At the slightest damage to a blood vessel, platelets rush to the breakthrough and stick to its walls and to each other, forming a plug.

By sticking together, platelets - as well as the damaged tissue itself - release substances that trigger the coagulation mechanism. They also secrete the hormone sirotin, which stimulates the constriction of blood vessels, thereby reducing blood flow.

The clumped platelets induce fibrinogen, one of the proteins dissolved in the plasma, to form strands of the insoluble protein fibrin, and the blood clots. Fibrin threads entwine blood cells in a dense network, forming a semi-solid mass. This network then contracts, releasing a light yellow liquid or serum, and forms a solid clot. The total blood volume will be restored within a few hours after the bleeding stops as water is absorbed from the tissues, but it will take several weeks for the blood cells to recover.

Of all the bleeding disorders, the most famous hereditary disease is hemophilia. It only affects men, but women can be carriers of it and pass it on to their sons. Many have heard about hemophilia, remembering the crowned heads who suffered from it - ten princes from the offspring of Queen Victoria of England were sick with it. However, that's quite rare disease, affecting about one boy in 10,000.

Hemophilia is caused by the absence in the blood of one of the clotting factors, a plasma protein known as antihemophilic globulin or factor VIII. Even small cut can cause uncontrollable blood loss, and patients with this disease often suffer from internal bleeding without apparent reason. In the past, most of these patients died in childhood. Nowadays they receive blood transfusions and injections of extracted plasma factor VIII, which allows you to conduct normal image life. The trouble, however, is that before all donor blood began to be tested, many patients received transfusions infected with the virus HIV blood with factor VIII.

The blood of each of us belongs to a certain type or group. Groups for the world of glue by features chemical structure erythrocyte membranes. There are several different systems for classifying blood into groups, but the most commonly used system is A B O, introduced in 1900 in Vienna by Karl Landsteiner. It has four groups A, B, AB and O.

Knowing your blood type is very important in situations where, due to an accident or during surgery, a transfusion becomes necessary, because blood of a different type may bring more harm than good. The blood of some groups can be safely transfused to any person, while others accept the influx of someone else's blood with hostility. In the latter case, our blood perceives someone else’s as an enemy due to differences in chemical composition and destroys her red blood cells as if they were bacteria.

In 1940, the same Landsteiner discovered another blood classification - Rhesus. It consists of 6 factors, the most important of which is factor D. It is present in the red blood cells of 85% of people, making them Rh positive. The remaining 15% do not have factor D in their blood, i.e. They are Rhesus negative. If a person with Rh negative transfusion of Rh-positive blood, his own blood will perceive factor D as a foreign substance and produce antibodies to neutralize it.

During a nerve transfusion, antibodies are produced too slowly to cause complications, but the person then develops strong immunity to factor D. The next time the person receives a transfusion, their blood produces antibodies to kill foreign cells.

Women with a negative Rh factor are especially at risk. Like all blood groups, the Rh_factor is inherited. If a woman has a negative Rh factor and her husband has a positive one, then their child may have a positive Rh factor.

Because the baby's cells are too large to pass from the fetus to the mother during pregnancy, the baby's Rh-positive cells have no way of causing the mother to produce antibodies. Therefore, if the mother has never had a transfusion before Rh positive blood, then there will be no problems. However, during childbirth, the mother bleeds through the placenta, and the baby's cells can enter the mother's veins. Then she will develop antibodies against them and acquire immunity to factor D. To prevent this from happening, women with a negative Rh factor are injected with antibodies to factor D after the first birth, due to which their body does not produce its own antibodies.

Both of these methods for determining the blood group are usually sufficient to find out whether it is possible to proceed with a transfusion, but if there is the slightest doubt, blood samples from the recipient and the donor are carefully compared in the laboratory.