What is blood in biology definition. What does human blood consist of? What does blood contain? Physicochemical properties of blood and plasma
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 hematopoietic organs (bone marrow, spleen, liver and lymph nodes) constitutes an integral 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 the cells, and the end products of metabolism (ammonia, urea, uric acid, etc.) - from them to the excretory organs.
15. Regulatory – carries out the transfer of hormones and other physiological active substances, affecting various organs and tissues; 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. Formed in red bone marrow, are 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 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, production of antibodies and destruction of toxins of protein origin);
2) participation in the breakdown of nutrients
Platelets- plasmatic formations of 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 that 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 a large number of 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 when platelets are destroyed. 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 AVO. 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 of blood that 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;
III groups a (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.
Residents 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 human blood: agglutinogen A with agglutinin a or agglutinogen B with agglutinin b. When incompatible blood is transfused, as a result of 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, blood of group I can be transfused to people with all blood groups (I, II, III, IV), therefore people with blood group I are called universal donors. Group II blood can be transfused to people with II and IY blood groups, group III blood - from III and IV, Group IV blood can be transfused only 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- fluid circulating in circulatory system and transporting gases and other dissolved substances necessary for metabolism or resulting from metabolic processes.
Blood consists of plasma (a clear, pale yellow liquid) and particles suspended in it. cellular elements. There are three main types of blood cells: red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (platelets). The red color of blood is determined by the presence of the red pigment hemoglobin in red blood cells. In the arteries, through which blood entering the heart from the lungs is transported to the tissues of the body, hemoglobin is saturated with oxygen and colored bright red; in the veins through which blood flows from tissues to the heart, hemoglobin is practically devoid of oxygen and is darker in color.
Blood is a rather viscous liquid, and its viscosity is determined by the content of red blood cells and dissolved proteins. Blood viscosity greatly influences the speed at which blood flows through arteries (semi-elastic structures) and blood pressure. The fluidity of blood is also determined by its density and the pattern of movement of various types of cells. Leukocytes, for example, move singly, in close proximity to the walls blood vessels; red blood cells can move either individually or in groups like stacked coins, creating an axial, i.e. flow concentrated in the center of the vessel. An adult male's blood volume is approximately 75 ml per kilogram of body weight; in an adult woman this figure is approximately 66 ml. Accordingly, the total blood volume in an adult man is on average about 5 liters; more than half of the volume is plasma, and the rest is mainly erythrocytes.
Blood functions
The functions of the blood are much more complex than simply transporting nutrients and metabolic waste. Hormones that control many vital processes are also carried in the blood; blood regulates body temperature and protects the body from damage and infection in any part of it.
Transport function of blood. Almost all processes related to digestion and respiration - two body functions without which life is impossible - are closely related to blood and blood supply. The connection with breathing is expressed in the fact that blood ensures gas exchange in the lungs and transport of the corresponding gases: oxygen - from the lungs to the tissue, carbon dioxide (carbon dioxide) - from the tissues to the lungs. Transport of nutrients begins from capillaries small intestine; here the blood captures them from the digestive tract and transports them to all organs and tissues, starting with the liver, where modification of nutrients (glucose, amino acids, fatty acids) occurs, and liver cells regulate their level in the blood depending on the needs of the body (tissue metabolism) . The transition of transported substances from blood to tissue occurs in tissue capillaries; at the same time, end products enter the blood from the tissues, which are then excreted through the kidneys with urine (for example, urea and uric acid). The blood also carries secretion products of the endocrine glands - hormones - and thereby ensures communication between various organs and coordination of their activities.
Body temperature regulation. Blood plays a key role in maintaining constant temperature bodies in homeothermic, or warm-blooded, organisms. The temperature of the human body in a normal state fluctuates in a very narrow range of about 37 ° C. The release and absorption of heat by different parts of the body must be balanced, which is achieved by heat transfer through the blood. The center of temperature regulation is located in the hypothalamus, a part of the diencephalon. This center, being highly sensitive to small changes in the temperature of the blood passing through it, regulates those physiological processes in which heat is released or absorbed. One mechanism is to regulate heat loss through the skin by changing the diameter of the cutaneous blood vessels of the skin and, accordingly, the volume of blood flowing near the surface of the body, where heat is more easily lost. In case of infection certain products the vital activity of microorganisms or the products of tissue breakdown caused by them interact with leukocytes, causing the formation of chemicals that stimulate the center of temperature regulation in the brain. As a result, there is a rise in body temperature, felt as heat.
Protecting the body from damage and infection. In the implementation of this blood function, two types of leukocytes play a special role: polymorphonuclear neutrophils and monocytes. They rush to the site of injury and accumulate near it, with most of these cells migrating from the bloodstream through the walls of nearby blood vessels. They are attracted to the site of injury chemical substances released by damaged tissues. These cells are able to absorb bacteria and destroy them with their enzymes.
Thus, they prevent the spread of infection in the body.
Leukocytes also take part in the removal of dead or damaged tissue. The process of absorption by a cell of a bacterium or a fragment of dead tissue is called phagocytosis, and the neutrophils and monocytes that carry it out are called phagocytes. An actively phagocytic monocyte is called a macrophage, and a neutrophil is called a microphage. In the fight against infection, an important role is played by plasma proteins, namely immunoglobulins, which include many specific antibodies. Antibodies are formed by other types of leukocytes - lymphocytes and plasma cells, which are activated when specific antigens of bacterial or viral origin enter the body (or those present on cells foreign to the body). It may take several weeks for lymphocytes to produce antibodies against the antigen the body encounters for the first time, but the resulting immunity lasts a long time. Although the level of antibodies in the blood begins to fall slowly after a few months, upon repeated contact with the antigen it rises again quickly. This phenomenon is called immunological memory. P
When interacting with the antibody, microorganisms either stick together or become more vulnerable to absorption by phagocytes. In addition, antibodies prevent the virus from entering the host cells.
blood pH. pH is an indicator of the concentration of hydrogen (H) ions, numerically equal to the negative logarithm (denoted by the Latin letter “p”) of this value. The acidity and alkalinity of solutions are expressed in units of the pH scale, which ranges from 1 (strong acid) to 14 (strong alkali). Normally, the pH of arterial blood is 7.4, i.e. close to neutral. Venous blood is somewhat acidified due to carbon dioxide dissolved in it: carbon dioxide (CO2), formed during metabolic processes, when dissolved in the blood, reacts with water (H2O), forming carbonic acid (H2CO3).
Maintaining blood pH at a constant level, i.e., in other words, acid-base balance, is extremely important. So, if the pH drops noticeably, the activity of enzymes in the tissues decreases, which is dangerous for the body. Changes in blood pH beyond the range of 6.8-7.7 are incompatible with life. The kidneys, in particular, contribute to maintaining this indicator at a constant level, since they remove acids or urea (which gives an alkaline reaction) from the body as needed. On the other hand, pH is maintained by the presence in the plasma of certain proteins and electrolytes that have a buffering effect (that is, the ability to neutralize some excess acid or alkali).
Physicochemical properties of blood. The density of whole blood depends mainly on its content of red blood cells, proteins and lipids. The color of blood changes from scarlet to dark red depending on the ratio of oxygenated (scarlet) and non-oxygenated forms of hemoglobin, as well as the presence of hemoglobin derivatives - methemoglobin, carboxyhemoglobin, etc. The color of plasma depends on the presence of red and yellow pigments in it - mainly carotenoids and bilirubin, a large amount of which in pathology gives the plasma a yellow color. Blood is a colloidal polymer solution in which water is the solvent, salts and low-molecular organic plasma are the dissolved substances, and proteins and their complexes are the colloidal component. On the surface of blood cells there is a double layer of electrical charges, consisting of negative charges firmly bound to the membrane and a diffuse layer of positive charges balancing them. Due to the double electrical layer, an electrokinetic potential arises, which plays an important role in stabilizing cells, preventing their aggregation. As the ionic strength of the plasma increases due to the entry of multiply charged positive ions into it, the diffuse layer contracts and the barrier preventing cell aggregation decreases. One of the manifestations of blood microheterogeneity is the phenomenon of erythrocyte sedimentation. It lies in the fact that in the blood outside the bloodstream (if its coagulation is prevented), the cells settle (sediment), leaving a layer of plasma on top.
Erythrocyte sedimentation rate (ESR) increases in various diseases, mainly of an inflammatory nature, due to changes in the protein composition of plasma. The sedimentation of erythrocytes is preceded by their aggregation with the formation of certain structures such as coin columns. The ESR depends on how their formation proceeds. The concentration of plasma hydrogen ions is expressed in hydrogen index values, i.e. negative logarithm of hydrogen ion activity. The average blood pH is 7.4. Maintaining the constancy of this value is a great physiol. significance, since it determines the rates of many chemicals. and physical-chemical processes in the body.
Normally, the pH of arterial K is 7.35-7.47; venous blood is 0.02 lower; the content of erythrocytes is usually 0.1-0.2 more acidic than plasma. One of the most important properties of blood - fluidity - is the subject of study of biorheology. In the bloodstream, blood normally behaves like a non-Newtonian fluid, changing its viscosity depending on flow conditions. In this regard, the viscosity of blood in large vessels and capillaries varies significantly, and the viscosity data given in the literature is conditional. The patterns of blood flow (blood rheology) have not been sufficiently studied. The non-Newtonian behavior of blood is explained by the high volume concentration of blood cells, their asymmetry, the presence of proteins in the plasma and other factors. Measured on capillary viscometers (with a capillary diameter of several tenths of a millimeter), the viscosity of blood is 4-5 times higher than the viscosity of water.
In pathology and injury, blood fluidity changes significantly due to the action of certain factors of the blood coagulation system. Basically, the work of this system consists in the enzymatic synthesis of a linear polymer - fabrin, which forms a network structure and gives the blood the properties of jelly. This “jelly” has a viscosity that is hundreds and thousands higher than the viscosity of blood in a liquid state, exhibits strength properties and high adhesive ability, which allows the clot to stay on the wound and protect it from mechanical damage. The formation of clots on the walls of blood vessels when the balance in the coagulation system is disturbed is one of the causes of thrombosis. The formation of a fibrin clot is prevented by the anticoagulation system; the destruction of the formed clots occurs under the action of the fibrinolytic system. The resulting fibrin clot initially has a loose structure, then becomes denser, and retraction of the clot occurs.
Blood components
Plasma. After the separation of cellular elements suspended in the blood, what remains is water solution complex composition, called plasma. As a rule, plasma is a clear or slightly opalescent liquid, yellowish color which is determined by the presence in it of a small amount of bile pigment and other colored organic substances. However, after consuming fatty foods, many fat droplets (chylomicrons) enter the bloodstream, causing the plasma to become cloudy and oily. Plasma is involved in many vital processes of the body. It transports blood cells, nutrients and metabolic products and serves as a link between all extravascular (i.e., located outside the blood vessels) fluids; the latter include, in particular, the intercellular fluid, and through it communication with the cells and their contents occurs.
Thus, the plasma comes into contact with the kidneys, liver and other organs and thereby maintains the constancy of the internal environment of the body, i.e. homeostasis. The main plasma components and their concentrations are shown in the table. Among the substances dissolved in plasma are low molecular weight organic compounds (urea, uric acid, amino acids, etc.); large and very complex protein molecules; partially ionized inorganic salts. The most important cations (positively charged ions) include sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+); The most important anions (negatively charged ions) are chloride anions (Cl-), bicarbonate (HCO3-) and phosphate (HPO42- or H2PO4-). The main protein components of plasma are albumin, globulins and fibrinogen.
Plasma proteins. Of all proteins, albumin, synthesized in the liver, is present in the highest concentration in plasma. It is necessary to maintain osmotic balance, ensuring normal distribution of fluid between blood vessels and the extravascular space. During fasting or insufficient protein intake from food, the albumin content in plasma decreases, which can lead to increased accumulation of water in tissues (edema). This condition, associated with protein deficiency, is called starvation edema. Plasma contains several types or classes of globulins, the most important of which are designated by the Greek letters a (alpha), b (beta) and g (gamma), and the corresponding proteins are a1, a2, b, g1 and g2. After separation of globulins (by electrophoresis), antibodies are detected only in fractions g1, g2 and b. Although antibodies are often called gamma globulins, the fact that some of them are also present in the b-fraction led to the introduction of the term “immunoglobulin”. The a- and b-fractions contain many different proteins that provide transport in the blood of iron, vitamin B12, steroids and other hormones. This same group of proteins also includes coagulation factors, which, along with fibrinogen, are involved in the process of blood clotting. The main function of fibrinogen is to form blood clots (thrombi). During the process of blood clotting, whether in vivo (in a living body) or in vitro (outside the body), fibrinogen is converted into fibrin, which forms the basis of a blood clot; Plasma that does not contain fibrinogen, usually in the form of a clear, pale yellow liquid, is called blood serum.
Red blood cells. Red blood cells, or erythrocytes, are round discs with a diameter of 7.2-7.9 µm and an average thickness of 2 µm (µm = micron = 1/106 m). 1 mm3 of blood contains 5-6 million red blood cells. They make up 44-48% of the total blood volume. Red blood cells have the shape of a biconcave disc, i.e. The flat sides of the disk are compressed, making it look like a donut without a hole. Mature red blood cells do not have nuclei. They contain mainly hemoglobin, the concentration of which in the intracellular aqueous environment is about 34%. [In terms of dry weight, the hemoglobin content in erythrocytes is 95%; per 100 ml of blood, the hemoglobin content is normally 12-16 g (12-16 g%), and in men it is slightly higher than in women.] In addition to hemoglobin, red blood cells contain dissolved inorganic ions (mainly K+) and various enzymes. The two concave sides provide the red blood cell with optimal surface area through which gases can be exchanged: carbon dioxide and oxygen.
Thus, the shape of cells largely determines the efficiency of physiological processes. In humans, the surface area through which gas exchange occurs is on average 3820 m2, which is 2000 times the surface of the body. In the fetus, primitive red blood cells are first formed in the liver, spleen and thymus. From the fifth month of intrauterine development, erythropoiesis gradually begins in the bone marrow - the formation of full-fledged red blood cells. In exceptional circumstances (for example, when normal bone marrow is replaced by cancerous tissue), the adult body can switch back to producing red blood cells in the liver and spleen. However, under normal conditions, erythropoiesis in an adult occurs only in flat bones (ribs, sternum, pelvic bones, skull and spine).
Red blood cells develop from precursor cells, the source of which is the so-called. stem cells. On early stages formation of red blood cells (in cells still in the bone marrow), the cell nucleus is clearly visible. As the cell matures, hemoglobin accumulates, formed during enzymatic reactions. Before entering the bloodstream, the cell loses its nucleus due to extrusion (squeezing out) or destruction by cellular enzymes. With significant blood loss, red blood cells are formed faster than normal, and in this case, immature forms containing a nucleus may enter the bloodstream; This apparently occurs because the cells leave the bone marrow too quickly.
The period of maturation of erythrocytes in the bone marrow - from the moment the youngest cell appears, recognizable as the precursor of an erythrocyte, to its full maturation - is 4-5 days. The lifespan of a mature erythrocyte in peripheral blood is on average 120 days. However, with certain abnormalities of these cells themselves, a number of diseases, or under the influence of certain medicines The lifespan of red blood cells may be shortened. Most of the red blood cells are destroyed in the liver and spleen; in this case, hemoglobin is released and breaks down into its components heme and globin. The further fate of globin was not traced; As for heme, iron ions are released from it (and returned to the bone marrow). Losing iron, heme turns into bilirubin - a red-brown bile pigment. After minor modifications occurring in the liver, bilirubin in bile is excreted through gallbladder into the digestive tract. Based on the content of the final product of its transformations in feces, the rate of destruction of red blood cells can be calculated. On average, in an adult body, 200 billion red blood cells are destroyed and re-formed every day, which is approximately 0.8% of their total number (25 trillion).
Hemoglobin. The main function of the red blood cell is to transport oxygen from the lungs to the tissues of the body. A key role in this process is played by hemoglobin - an organic red pigment consisting of heme (a porphyrin compound with iron) and globin protein. Hemoglobin has a high affinity for oxygen, due to which the blood is able to carry much more oxygen than a regular aqueous solution.
The degree of binding of oxygen to hemoglobin depends primarily on the concentration of oxygen dissolved in the plasma. In the lungs, where there is a lot of oxygen, it diffuses from the pulmonary alveoli through the walls of blood vessels and the aqueous medium of the plasma and enters the red blood cells; there it binds to hemoglobin - oxyhemoglobin is formed. In tissues where the oxygen concentration is low, oxygen molecules are separated from hemoglobin and penetrate into the tissue due to diffusion. Insufficiency of red blood cells or hemoglobin leads to a decrease in oxygen transport and thereby to disruption of biological processes in tissues. In humans, a distinction is made between fetal hemoglobin (type F, from fetus) and adult hemoglobin (type A, from adult). There are many known genetic variants of hemoglobin, the formation of which leads to abnormalities of red blood cells or their function. Among them, the most famous is hemoglobin S, which causes sickle cell anemia.
Leukocytes. White peripheral blood cells, or leukocytes, are divided into two classes depending on the presence or absence of special granules in their cytoplasm. Cells that do not contain granules (agranulocytes) are lymphocytes and monocytes; their kernels have a predominantly regular round shape. Cells with specific granules (granulocytes) are usually characterized by the presence of irregularly shaped nuclei with many lobes and are therefore called polymorphonuclear leukocytes. They are divided into three types: neutrophils, basophils and eosinophils. They differ from each other in the pattern of granules stained with various dyes. In a healthy person, 1 mm3 of blood contains from 4000 to 10,000 leukocytes (on average about 6000), which is 0.5-1% of blood volume. Ratio individual species The number of cells in white blood cells can vary significantly from person to person and even from one person to another at different times.
Polymorphonuclear leukocytes(neutrophils, eosinophils and basophils) are formed in the bone marrow from precursor cells, which give rise to stem cells, probably the same ones that give rise to the precursors of red blood cells. As the nucleus matures, the cells develop granules that are typical for each cell type. In the bloodstream, these cells move along the walls of the capillaries primarily due to amoeboid movements. Neutrophils are able to leave the internal space of the vessel and accumulate at the site of infection. The lifespan of granulocytes appears to be about 10 days, after which they are destroyed in the spleen. The diameter of neutrophils is 12-14 microns. Most dyes color their core in purple; the nucleus of peripheral blood neutrophils can have from one to five lobes. The cytoplasm is stained pinkish; under a microscope, many intense pink granules can be distinguished in it. In women, approximately 1% of neutrophils carry sex chromatin (formed by one of the two X chromosomes), a drumstick-shaped body attached to one of the nuclear lobes. These so-called Barr bodies allow sex to be determined by examining blood samples. Eosinophils are similar in size to neutrophils. Their nucleus rarely has more than three lobes, and the cytoplasm contains many large granules, which clearly stain bright red with eosin dye. Unlike eosinophils, basophils have cytoplasmic granules stained blue with basic dyes.
Monocytes. The diameter of these non-granular leukocytes is 15-20 microns. The nucleus is oval or bean-shaped, and only in a small part of the cells is it divided into large lobes that overlap each other. When stained, the cytoplasm is bluish-gray and contains a small number of inclusions that are stained blue-violet with azure dye. Monocytes are formed both in the bone marrow and in the spleen and lymph nodes. Their main function is phagocytosis.
Lymphocytes. These are small mononuclear cells. Most peripheral blood lymphocytes have a diameter of less than 10 µm, but lymphocytes with a larger diameter (16 µm) are sometimes found. The cell nuclei are dense and round, the cytoplasm is bluish in color, with very sparse granules. Although lymphocytes appear morphologically uniform, they differ clearly in their functions and cell membrane properties. They are divided into three broad categories: B cells, T cells, and O cells (null cells, or neither B nor T). B lymphocytes mature in the human bone marrow and then migrate to the lymphoid organs. They serve as precursors to cells that form antibodies, the so-called. plasmatic. In order for B cells to transform into plasma cells, the presence of T cells is necessary. The maturation of T cells begins in the bone marrow, where prothymocytes are formed, which then migrate to the thymus (thymus gland), an organ located in chest behind the sternum. There they differentiate into T lymphocytes, a highly heterogeneous population of cells immune system, performing various functions. Thus, they synthesize macrophage activation factors, B-cell growth factors and interferons. Among T cells there are inducer (helper) cells that stimulate the formation of antibodies by B cells. There are also suppressor cells that suppress the functions of B cells and synthesize the growth factor of T cells - interleukin-2 (one of the lymphokines). O cells differ from B and T cells in that they do not have surface antigens. Some of them serve as “natural killers”, i.e. kill cancer cells and cells infected with a virus. However, the overall role of O cells is unclear.
Platelets They are colorless, nuclear-free bodies of spherical, oval or rod-shaped shape with a diameter of 2-4 microns. Normally, the platelet content in peripheral blood is 200,000-400,000 per 1 mm3. Their lifespan is 8-10 days. Standard dyes (azur-eosin) give them a uniform pale pink color. Using electron microscopy, it was shown that the structure of the cytoplasm of platelets is similar to ordinary cells; however, they are not actually cells, but fragments of the cytoplasm of very large cells (megakaryocytes) present in the bone marrow. Megakaryocytes are derived from the descendants of the same stem cells that give rise to red and white blood cells. As will be discussed in the next section, platelets play a key role in blood clotting. Bone marrow damage caused by drugs ionizing radiation or in case of cancer can lead to a significant decrease in the platelet count in the blood, which causes spontaneous hematomas and bleeding.
Blood clotting Blood clotting, or coagulation, is the process of turning liquid blood into an elastic clot (thrombus). Blood clotting at the site of injury is a vital reaction that stops bleeding. However, the same process also underlies vascular thrombosis - an extremely unfavorable phenomenon in which a complete or partial blockage of their lumen occurs, preventing blood flow.
Hemostasis (stopping bleeding). When a thin or even medium-sized blood vessel is damaged, for example by cutting or squeezing tissue, internal or external bleeding (hemorrhage) occurs. As a rule, bleeding stops due to the formation of a blood clot at the site of injury. A few seconds after injury, the lumen of the vessel contracts in response to the action of released chemicals and nerve impulses. When the endothelial lining of blood vessels is damaged, the collagen located under the endothelium is exposed, to which platelets circulating in the blood quickly adhere. They release chemicals that cause blood vessels to narrow (vasoconstrictors). Platelets also secrete other substances that participate in a complex chain of reactions leading to the conversion of fibrinogen (a soluble blood protein) into insoluble fibrin. Fibrin forms a blood clot, the threads of which trap blood cells. One of the most important properties of fibrin is its ability to polymerize to form long fibers that compress and push blood serum out of the clot.
Thrombosis- abnormal blood clotting in arteries or veins. As a result of arterial thrombosis, blood flow to the tissues deteriorates, which causes their damage. This occurs with myocardial infarction caused by thrombosis of a coronary artery, or with a stroke caused by thrombosis of cerebral vessels. Vein thrombosis prevents the normal flow of blood from tissues. When a large vein is blocked by a blood clot, swelling occurs near the site of the blockage, which sometimes spreads, for example, to the entire limb. It happens that part of the venous thrombus breaks off and enters the bloodstream in the form of a moving clot (embolus), which over time can end up in the heart or lungs and lead to life-threatening circulatory problems.
Several factors have been identified that predispose to intravascular thrombus formation; These include:
- slowing of venous blood flow due to low physical activity;
- vascular changes caused by increased blood pressure;
- local hardening of the inner surface of blood vessels due to inflammatory processes or - in the case of arteries - due to the so-called. atheromatosis (lipid deposits on artery walls);
- increased blood viscosity due to polycythemia (increased levels of red blood cells in the blood);
- an increase in the number of platelets in the blood.
Studies have shown that the last of these factors plays a special role in the development of thrombosis. The fact is that a number of substances contained in platelets stimulate the formation of a blood clot, and therefore any influences that cause platelet damage can accelerate this process. When damaged, the platelet surface becomes more sticky, causing them to stick together (aggregate) and release their contents. The endothelial lining of blood vessels contains the so-called. prostacyclin, which suppresses the release of the thrombogenic substance, thromboxane A2, from platelets. Other plasma components also play an important role, preventing thrombus formation in blood vessels by suppressing a number of enzymes of the blood coagulation system. Attempts to prevent thrombosis have so far yielded only partial results. In number preventive measures includes regular physical exercise, lowering high blood pressure and treating with anticoagulants; After surgery, it is recommended to start walking as early as possible. It should be noted that daily intake of aspirin, even in a small dose (300 mg), reduces platelet aggregation and significantly reduces the likelihood of thrombosis.
Blood transfusion Since the late 1930s, transfusion of blood or its individual fractions has become widespread in medicine, especially in the military. The main purpose of blood transfusion (hemotransfusion) is to replace the patient's red blood cells and restore blood volume after massive blood loss. The latter can occur either spontaneously (for example, with an ulcer duodenum), or as a result of injury, during surgery or during childbirth. Blood transfusions are also used to restore the level of red blood cells in some anemias, when the body loses the ability to produce new blood cells at the rate required for normal functioning. The general consensus among medical authorities is that blood transfusions should only be given when strictly necessary, as they carry a risk of complications and transmission to the patient. infectious disease- hepatitis, malaria or AIDS.
Blood typing. Before transfusion, the compatibility of the blood of the donor and the recipient is determined, for which blood typing is performed. Currently, typing is carried out by qualified specialists. A small amount of red blood cells is added to an antiserum containing large amounts of antibodies to certain erythrocyte antigens. Antiserum is obtained from the blood of donors specially immunized with the corresponding blood antigens. Red blood cell agglutination is observed with the naked eye or under a microscope. The table shows how anti-A and anti-B antibodies can be used to determine ABO blood groups. As an additional in vitro test, you can mix donor red blood cells with recipient serum and, conversely, donor serum with recipient red blood cells - and see if there is any agglutination. This test is called cross-typing. If even a small number of cells agglutinate when mixing donor red blood cells and recipient serum, the blood is considered incompatible.
Blood transfusion and storage. The original methods of direct blood transfusion from donor to recipient are a thing of the past. Today, donor blood is taken from a vein under sterile conditions into specially prepared containers, into which an anticoagulant and glucose are previously added (the latter as a nutrient medium for red blood cells during storage). The most commonly used anticoagulant is sodium citrate, which binds calcium ions in the blood, which are necessary for blood clotting. Liquid blood is stored at 4°C for up to three weeks; During this time, 70% of the initial number of viable red blood cells remains. Since this level of living red blood cells is considered the minimum acceptable, blood stored for more than three weeks is not used for transfusion. With the growing need for blood transfusions, methods have emerged to keep red blood cells alive for longer periods of time. In the presence of glycerin and other substances, red blood cells can be stored indefinitely at temperatures from -20 to -197° C. For storage at -197° C, metal containers with liquid nitrogen, into which containers with blood are immersed. Blood that has been frozen is successfully used for transfusion. Freezing allows not only to create reserves of regular blood, but also to collect and store rare blood groups in special blood banks (storages).
Previously, blood was stored in glass containers, but now mostly plastic containers are used for this purpose. One of the main advantages of the plastic bag is that several bags can be attached to one anticoagulant container, and then using differential centrifugation in a “closed” system, all three types of cells and plasma can be separated from the blood. This very important innovation radically changed the approach to blood transfusion.
Today they are already talking about component therapy, when by transfusion we mean replacing only those blood elements that the recipient needs. Most people with anemia only need whole red blood cells; patients with leukemia require mainly platelets; hemophiliacs require only certain plasma components. All these fractions can be isolated from the same donor blood, after which only albumin and gamma globulin will remain (both have their own areas of application). Whole blood is used only to compensate for very large blood loss, and is now used for transfusion in less than 25% of cases.
Blood banks. In all developed countries, a network of blood transfusion stations has been created, which provide civil medicine with the necessary amount of blood for transfusion. At stations, as a rule, they only collect donor blood and store it in blood banks (storages). The latter provide blood upon request from hospitals and clinics. the desired group. In addition, they usually have a special service that is responsible for obtaining both plasma and individual fractions (for example, gamma globulin) from expired whole blood. Many banks also have qualified specialists who perform complete blood typing and study possible reactions incompatibility.
Blood (haema, sanguis) is a liquid tissue consisting of plasma and blood cells suspended in it. The blood is enclosed in a system of blood vessels and is in a state of continuous movement. Blood, lymph, interstitial fluid are the 3 internal environments of the body that wash all cells, delivering them the substances necessary for life, and carry away the end products of metabolism. The internal environment of the body is constant in its composition and physicochemical properties. The constancy of the internal environment of the body is called homeostasis and is a necessary condition life. Homeostasis is regulated by the nervous and endocrine systems. The cessation of blood flow during cardiac arrest leads to the death of the body.
Blood functions:
Transport (respiratory, nutritional, excretory)
Protective (immune, protection against blood loss)
Thermostatic
Humoral regulation of functions in the body.
QUANTITY OF BLOOD, PHYSICAL AND CHEMICAL PROPERTIES OF BLOOD
Quantity
Blood makes up 6-8% of body weight. Newborns have up to 15%. On average, a person has 4.5 - 5 liters. Blood circulating in the vessels - peripheral , part of the blood is contained in the depot (liver, spleen, skin) - deposited . Loss of 1/3 of blood leads to the death of the body.
Specific gravity(density) of blood - 1,050 - 1,060.
It depends on the number of red blood cells, hemoglobin and proteins in the blood plasma. It increases with blood thickening (dehydration, exercise). A decrease in the specific gravity of blood is observed with the influx of fluid from tissues after blood loss. Women have a slightly lower specific gravity of blood because they have fewer red blood cells.
Blood viscosity 3- 5, exceeds the viscosity of water by 3 - 5 times (the viscosity of water at a temperature of + 20°C is taken as 1 conventional unit).
Plasma viscosity is 1.7-2.2.
Blood viscosity depends on the number of red blood cells and plasma proteins (mainly
fibrinogen) in the blood.
The rheological properties of blood depend on the viscosity of blood - the speed of blood flow and
peripheral blood resistance in blood vessels.
Viscosity has different values in different vessels (the highest in venules and
veins, lower in arteries, lowest in capillaries and arterioles). If
the viscosity would be the same in all vessels, then the heart would have to develop
power is 30-40 times greater to push blood through the entire vascular
Viscosity increases with blood thickening, dehydration, after physical exercise
loads, with erythremia, some poisonings, in venous blood, upon administration
drugs - coagulants (drugs that enhance blood clotting).
Viscosity decreases with anemia, with the influx of fluid from tissues after blood loss, with hemophilia, with an increase in temperature, in arterial blood, with the introduction heparin and other anticoagulants.
Medium reaction (pH) - fine 7,36 - 7,42. Life is possible if the pH is between 7 and 7.8.
A condition in which acidic equivalents accumulate in the blood and tissues is called acidosis (acidification), The blood pH decreases (less than 7.36). Acidosis may be :
gas - with the accumulation of CO 2 in the blood (CO2+ H 2 O<->H 2 CO 3 - accumulation of acid equivalents);
metabolic (accumulation of acidic metabolites, for example, in diabetic coma, accumulation of acetoacetic and gamma-aminobutyric acids).
Acidosis leads to central nervous system inhibition, coma and death.
The accumulation of alkali equivalents is called alkalosis (alkalinization)-increase in pH more than 7.42.
Alkalosis may also be gas , with hyperventilation of the lungs (if too much CO 2 is removed), metabolic - with the accumulation of alkaline equivalents and excessive excretion of acidic ones (uncontrollable vomiting, diarrhea, poisoning, etc.) Alkalosis leads to overexcitation of the central nervous system, muscle cramps and death.
Maintaining pH is achieved through blood buffer systems, which can bind hydroxyl (OH-) and hydrogen ions (H+) and thereby keep the blood reaction constant. The ability of buffer systems to counteract pH shifts is explained by the fact that when they interact with H+ or OH-, compounds are formed that have a weakly acidic or basic character.
The main buffer systems of the body:
protein buffer system (acidic and alkaline proteins);
hemoglobin (hemoglobin, oxyhemoglobin);
bicarbonate (bicarbonates, carbonic acid);
phosphate (primary and secondary phosphates).
Blood osmotic pressure = 7.6-8.1 atm.
It is being created mainly sodium salts and other mineral salts dissolved in the blood.
Thanks to osmotic pressure, water is distributed evenly between cells and tissues.
Isotonic solutions are called solutions whose osmotic pressure is equal to the osmotic pressure of blood. In isotonic solutions, red blood cells do not change. Isotonic solutions are: physiological solution 0.86% NaCl, Ringer's solution, Ringer-Locke solution, etc.
In hypotonic solution(the osmotic pressure of which is lower than in the blood), water from the solution goes into the red blood cells, while they swell and collapse - osmotic hemolysis. Solutions with higher osmotic pressure are called hypertensive, the red blood cells in them lose H 2 O and shrink.
Oncotic blood pressure caused by blood plasma proteins (mainly albumin) Normally it is 25-30 mm Hg. Art.(on average 28) (0.03 - 0.04 atm.). Oncotic pressure is the osmotic pressure of blood plasma proteins. It is part of the osmotic pressure (it is 0.05% of
osmotic). Thanks to it, water is retained in the blood vessels (vascular bed).
When the amount of proteins in the blood plasma decreases - hypoalbuminemia (with impaired liver function, hunger), oncotic pressure decreases, water leaves the blood through the wall of blood vessels into the tissue, and oncotic edema (“hungry” edema) occurs.
ESR- erythrocyte sedimentation rate, expressed in mm/hour. U men ESR is normal – 0-10 mm/hour , among women - 2-15 mm/hour (in pregnant women up to 30-45 mm/hour).
ESR increases in inflammatory, purulent, infectious and malignant diseases; it is normally elevated in pregnant women.
BLOOD COMPOSITION
Formed elements of blood - blood cells, make up 40 - 45% of blood.
Blood plasma is a liquid intercellular substance of blood, making up 55 - 60% of blood.
The ratio of plasma and blood cells is called hematocritindex, because it is determined using hematocrit.
When blood stands in a test tube, the formed elements settle to the bottom, and the plasma remains on top.
BLOOD ELEMENTS
Erythrocytes (red blood cells), leukocytes (white blood cells), platelets (red blood platelets).
erythrocytes- these are red blood cells that lack a nucleus and have
the shape of a biconcave disk, 7-8 microns in size.
They are formed in the red bone marrow, live 120 days, are destroyed in the spleen (“red blood cell cemetery”), liver, and macrophages.
Functions:
1) respiratory - due to hemoglobin (transfer of O 2 and CO 2);
nutritious - can transport amino acids and other substances;
protective - capable of binding toxins;
enzymatic - contain enzymes. Quantity normal red blood cells:
in men in 1 ml - 4.1-4.9 million.
in women in 1 ml – 3.9 million.
in newborns in 1 ml - up to 6 million.
in the elderly in 1 ml - less than 4 million.
An increase in the number of red blood cells in the blood is called erythrocytosis.
Types of erythrocytosis:
1.Physiological(normal) - in newborns, residents of mountainous areas, after meals and physical activity.
2.Pathological- for hematopoietic disorders, erythremia (hemoblastosis - tumor diseases of the blood).
A decrease in the number of red blood cells in the blood is called erythropenia. It can occur after blood loss, disruption of red blood cell formation
(iron deficiency, B!2 deficiency, folate deficiency anemia) and increased destruction of red blood cells (hemolysis).
HEMOGLOBIN (Нь)- red respiratory pigment found in red blood cells. It is synthesized in the red bone marrow and destroyed in the spleen, liver, and macrophages.
Hemoglobin consists of protein - globin and 4 molecules. Heme- the non-protein part of Hb, contains iron, which combines with O 2 and CO 2. One molecule of hemoglobin can attach 4 molecules of O 2.
Norm amount of Hb in the blood of men up to 132-164 g/l, in women 115-145 g/l. Hemoglobin decreases - with anemia (iron deficiency and hemolytic), after blood loss, increases - with blood thickening, B12 - folic - deficiency anemia, etc.
Myoglobin is muscle hemoglobin. Plays an important role in the supply of O2 to skeletal muscles.
Functions of hemoglobin: - respiratory - transfer of oxygen and carbon dioxide;
enzymatic - contains enzymes;
buffer - participates in maintaining blood pH. Hemoglobin compounds:
1.physiological compounds of hemoglobin:
A) Oxyhemoglobin: Hb + O 2<->NIO 2
b) Carbohemoglobin: Hb + CO 2<->HbCO 2 2. pathological hemoglobin compounds
a) Carboxyhemoglobin- a compound with carbon monoxide, formed during carbon monoxide (CO) poisoning, irreversible, while Hb is no longer able to tolerate O 2 and CO 2: Hb + CO -> HbO
b) Methemoglobin(Met Hb) - a compound with nitrates, the compound is irreversible, formed during nitrate poisoning.
HEMOLYSIS - this is the destruction of red blood cells with the release of hemoglobin out. Types of hemolysis:
1. Mechanical hemolysis - can occur when shaking a test tube with blood.
2. Chemical hemolysis - acids, alkalis, etc.
Z. Osmotic hemolysis - in a hypotonic solution, the osmotic pressure of which is lower than in the blood. In such solutions, water from the solution goes into the red blood cells, while they swell and collapse.
4. Biological hemolysis - during transfusion of an incompatible blood group, during snake bites (the poison has a hemolytic effect).
Hemolyzed blood is called “lacquer”, its color is bright red because hemoglobin passes into the blood. Hemolyzed blood is unsuitable for analysis.
LEUCOCYTES- these are colorless (white) blood cells, containing a nucleus and protoplasm. They are formed in the red bone marrow, live 7-12 days, are destroyed in the spleen, liver, and macrophages.
Functions of leukocytes: immune defense, phagocytosis of foreign particles.
Properties of leukocytes:
Amoeboid motility.
Diapedesis is the ability to pass through the wall of blood vessels into tissue.
Chemotaxis is movement in tissues towards the site of inflammation.
The ability to phagocytosis - the absorption of foreign particles.
In the blood of healthy people at rest white blood cell count ranges from 3.8-9.8 thousand in 1 ml.
An increase in the number of white blood cells in the blood is called leukocytosis.
Types of leukocytosis:
Physiological leukocytosis (normal) - after eating and physical activity.
Pathological leukocytosis - occurs during infectious, inflammatory, purulent processes, leukemia.
Decreased white blood cell count in the blood is called leukopenia, may be due to radiation sickness, exhaustion, aleukemic leukemia.
The percentage ratio of the types of leukocytes among themselves is called leukocyte formula.
Blood functions.
Blood is a liquid tissue consisting of plasma and blood cells suspended in it. Blood circulation through a closed cardiovascular system is a necessary condition for maintaining the constancy of its composition. Stopping the heart and stopping blood flow immediately leads the body to death. The study of blood and its diseases is called hematology.
Physiological functions of blood:
1. Respiratory - transfer of oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.
2. Trophic (nutritional) – delivers nutrients, vitamins, mineral salts, water from the digestive organs to the tissues.
3. Excretory (excretory) – release from tissues of final decay products, excess water and mineral salts.
4. Thermoregulatory – regulation of body temperature by cooling energy-intensive organs and warming organs that lose heat.
5. Homeostatic – maintaining the stability of a number of homeostasis constants (ph, osmotic pressure, isoionicity).
6. Regulation water-salt metabolism between blood and tissues.
7. Protective – participation in cellular (leukocytes) and humoral (At) immunity, in the process of coagulation to stop bleeding.
8. Humoral – transfer of hormones.
9. Creative (creative) – transfer of macromolecules that carry out intercellular information transfer in order to restore and maintain the structure of body tissues.
Quantity and physicochemical properties of blood.
The total amount of blood in the body of an adult is normally 6-8% of body weight and is approximately 4.5-6 liters. Blood consists of a liquid part - plasma and blood cells suspended in it - formed elements: red (erythrocytes), white (leukocytes) and blood platelets (platelets). In circulating blood, formed elements make up 40-45%, plasma accounts for 55-60%. In deposited blood, on the contrary: formed elements - 55-60%, plasma - 40-45%.
The viscosity of whole blood is about 5, and the viscosity of plasma is 1.7–2.2 (relative to the viscosity of water of 1). The viscosity of blood is due to the presence of proteins and especially red blood cells.
Osmotic pressure is the pressure exerted by substances dissolved in the plasma. It depends mainly on the mineral salts it contains and averages 7.6 atm, which corresponds to the freezing point of blood equal to -0.56 - -0.58 ° C. About 60% of the total osmotic pressure is due to Na salts.
Blood oncotic pressure is the pressure created by plasma proteins (i.e. their ability to attract and retain water). Determined by more than 80% albumin.
The blood reaction is determined by the concentration of hydrogen ions, which is expressed as a hydrogen indicator - pH.
In a neutral environment pH = 7.0
In acidic - less than 7.0.
In alkaline – more than 7.0.
Blood has a pH of 7.36, i.e. its reaction is slightly alkaline. Life is possible within a narrow range of pH shifts from 7.0 to 7.8 (since only under these conditions can enzymes - catalysts of all biochemical reactions - work).
Blood plasma.
Blood plasma is a complex mixture of proteins, amino acids, carbohydrates, fats, salts, hormones, enzymes, antibodies, dissolved gases and protein breakdown products (urea, uric acid, creatinine, ammonia) that must be excreted from the body. Plasma contains 90-92% water and 8-10% dry matter, mainly proteins and mineral salts. Plasma has a slightly alkaline reaction (pH = 7.36).
Plasma proteins (there are more than 30 of them) include 3 main groups:
· Globulins ensure the transport of fats, lipoids, glucose, copper, iron, the production of antibodies, as well as α- and β-agglutinins in the blood.
Albumin provides oncotic pressure, binds medicinal substances, vitamins, hormones, pigments.
· Fibrinogen is involved in blood clotting.
Formed elements of blood.
Red blood cells (from the Greek erytros - red, cytus - cell) are nuclear-free blood cells containing hemoglobin. They have the shape of biconcave disks with a diameter of 7-8 microns and a thickness of 2 microns. They are very flexible and elastic, easily deformed and pass through blood capillaries with a diameter smaller than the diameter of a red blood cell. The lifespan of red blood cells is 100-120 days.
In the initial phases of their development, red blood cells have a nucleus and are called reticulocytes. As it matures, the nucleus is replaced by respiratory pigment - hemoglobin, which makes up 90% of the dry matter of erythrocytes.
Normally, 1 μl (1 cubic mm) of blood in men contains 4-5 million red blood cells, in women – 3.7-4.7 million, in newborns the number of red blood cells reaches 6 million. Increase in the number of red blood cells per unit volume of blood is called erythrocytosis, a decrease is called erythropenia. Hemoglobin is the main component of red blood cells, ensures the respiratory function of the blood through the transport of oxygen and carbon dioxide and regulates the pH of the blood, having the properties of weak acids.
Normally, men contain 145 g/l of hemoglobin (with fluctuations 130-160 g/l), women – 130 g/l (120-140 g/l). The total amount of hemoglobin in five liters of blood in a person is 700-800 g.
Leukocytes (from the Greek leukos - white, cytus - cell) are colorless nuclear cells. The size of leukocytes is 8-20 microns. They are formed in the red bone marrow, lymph nodes, and spleen. 1 μl of human blood normally contains 4-9 thousand leukocytes. Their number fluctuates throughout the day, is reduced in the morning, increases after eating (digestive leukocytosis), increases during muscular work, and strong emotions.
An increase in the number of leukocytes in the blood is called leukocytosis, a decrease is called leukopenia.
The lifespan of leukocytes is on average 15-20 days, lymphocytes - 20 years or more. Some lymphocytes live throughout a person's life.
Based on the presence of granularity in the cytoplasm, leukocytes are divided into 2 groups: granular (granulocytes) and non-granular (agranulocytes).
The group of granulocytes includes neutrophils, eosinophils and basophils. They have a large number of granules in the cytoplasm, which contain enzymes necessary for the digestion of foreign substances. The nuclei of all granulocytes are divided into 2–5 parts, interconnected by threads, which is why they are also called segmented leukocytes. Young forms of neutrophils with nuclei in the form of rods are called band neutrophils, and those in the form of an oval are called young.
Lymphocytes are the smallest of the leukocytes and have a large round nucleus surrounded by a narrow rim of cytoplasm.
Monocytes are large agranulocytes with an oval or bean-shaped nucleus.
The percentage of certain types of leukocytes in the blood is called leukocyte formula, or leukogram:
· eosinophils 1 – 4%
· basophils 0.5%
· neutrophils 60 – 70%
lymphocytes 25 – 30%
· monocytes 6 – 8%
In healthy people, the leukogram is quite constant, and its changes serve as a sign various diseases. For example, in acute inflammatory processes There is an increase in the number of neutrophils (neutrophilia), with allergic diseases and helminthic disease - an increase in the number of eosinophils (eosinophilia), with sluggish chronic infections(tuberculosis, rheumatism, etc.) – the number of lymphocytes (lymphocytosis).
Neutrophils can be used to determine a person's gender. In the presence of a female genotype, 7 out of 500 neutrophils contain special, female-specific formations called “drumsticks” (round outgrowths with a diameter of 1.5-2 μm, connected to one of the segments of the nucleus through thin chromatin bridges).
Leukocytes perform many functions:
1. Protective – fight against foreign agents (they phagocytose (absorb) foreign bodies and destroy them).
2. Antitoxic – production of antitoxins that neutralize the waste products of microbes.
3. Production of antibodies that provide immunity, i.e. immunity to infections and genetically foreign substances.
4. Participate in the development of all stages of inflammation, stimulate recovery (regenerative) processes in the body and accelerate wound healing.
5. Provide graft rejection and destruction of own mutant cells.
6. They form active (endogenous) pyrogens and form a febrile reaction.
Platelets, or blood platelets (Greek thrombos - blood clot, cytus - cell) are round or oval non-nuclear formations with a diameter of 2-5 microns (3 times smaller than red blood cells). Platelets are formed in the red bone marrow from giant cells - megakaryocytes. 1 μl of human blood normally contains 180-300 thousand platelets. A significant part of them is deposited in the spleen, liver, lungs, and, if necessary, enters the blood. An increase in the number of platelets in peripheral blood is called thrombocytosis, a decrease is called thrombocytopenia. The lifespan of platelets is 2-10 days.
Functions of platelets:
1. Participate in the process of blood clotting and dissolution of the blood clot (fibrinolysis).
2. Participate in stopping bleeding (hemostasis) due to the biologically active compounds present in them.
3. Perform a protective function due to the gluing (agglutination) of microbes and phagocytosis.
4. They produce some enzymes necessary for the normal functioning of platelets and for the process of stopping bleeding.
5. They transport creative substances that are important for preserving the structure of the vascular wall (without interaction with platelets, the vascular endothelium undergoes degeneration and begins to let red blood cells pass through it).
Blood coagulation system. Blood groups. Rh factor. Hemostasis and its mechanisms.
Hemostasis (Greek haime - blood, stasis - stationary state) is the cessation of blood movement through a blood vessel, i.e. stop bleeding. There are 2 mechanisms to stop bleeding:
1. Vascular-platelet hemostasis can independently stop bleeding from the most frequently injured small vessels with fairly low blood pressure in a few minutes. It consists of two processes:
Vascular spasm leading to a temporary stop or reduction of bleeding;
Formation, compaction and contraction of a platelet plug, leading to a complete stop of bleeding.
2. Coagulation hemostasis (blood clotting) ensures the cessation of blood loss when large vessels are damaged. Blood clotting is a protective reaction of the body. When wounded and blood leaks from the vessels, it changes from a liquid state to a jelly-like state. The resulting clot clogs the damaged vessels and prevents the loss of a significant amount of blood.
The concept of the Rh factor.
In addition to the ABO system (Landsteiner system), there is the Rh system, since in addition to the main agglutinogens A and B, erythrocytes may contain other additional ones, in particular, the so-called Rh agglutinogen (Rh factor). It was first discovered in 1940 by K. Landsteiner and I. Wiener in the blood of the rhesus monkey.
85% of people have the Rh factor in their blood. This blood is called Rh positive. Blood that lacks the Rh factor is called Rh negative. A special feature of the Rh factor is that people do not have anti-Rhesus agglutinins.
Blood groups.
Blood groups are a set of characteristics that characterize the antigenic structure of red blood cells and the specificity of anti-erythrocyte antibodies, which are taken into account when selecting blood for transfusions (from the Latin transfusio - transfusion).
Based on the presence of certain agglutinogens and agglutinins in the blood, people’s blood is divided into 4 groups, according to the Landsteiner ABO system.
Immunity, its types.
Immunity (from Latin immunitas - liberation from something, deliverance) is the body’s immunity to pathogens or poisons, as well as the body’s ability to protect itself from genetically foreign bodies and substances.
According to the method of origin they distinguish congenital And acquired immunity.
Innate (species) immunity is a hereditary trait for this type of animal (dogs and rabbits do not get polio).
Acquired immunity acquired in the process of life and is divided into naturally acquired and artificially acquired. Each of them, according to the method of occurrence, is divided into active and passive.
Naturally acquired active immunity occurs after suffering a corresponding infectious disease.
Naturally acquired passive immunity is caused by the transfer of protective antibodies from the mother’s blood through the placenta into the blood of the fetus. In this way, newborn children gain immunity against measles, scarlet fever, diphtheria and other infections. After 1-2 years, when the antibodies received from the mother are destroyed and partially released from the child’s body, his susceptibility to these infections increases sharply. Passive immunity can be transmitted to a lesser extent through mother's milk.
Artificially acquired immunity is reproduced by humans in order to prevent infectious diseases.
Active artificial immunity is achieved through vaccination healthy people cultures of killed or weakened pathogenic microbes, weakened toxins or viruses. For the first time, artificial active immunization was performed by Jenner by inoculating children with cowpox. This procedure was called by Pasteur vaccination, and the grafting material was called vaccine (from the Latin vacca - cow).
Passive artificial immunity is reproduced by injecting a person with serum containing ready-made antibodies against microbes and their toxins. Antitoxic serums are especially effective against diphtheria, tetanus, gas gangrene, botulism, and snake venoms (cobra, viper, etc.). these sera are obtained mainly from horses, which are immunized with the corresponding toxin.
Depending on the direction of action, antitoxic, antimicrobial and antiviral immunity are also distinguished.
Antitoxic immunity is aimed at neutralizing microbial poisons, the leading role in it belongs to antitoxins.
Antimicrobial (antibacterial) immunity is aimed at destroying microbial bodies. Antibodies and phagocytes play a major role in this process.
Antiviral immunity is manifested by the formation in the cells of the lymphoid series of a special protein - interferon, which suppresses the reproduction of viruses
1. Blood is a liquid tissue that circulates through the vessels, transporting various substances within the body and providing nutrition and metabolism to all cells of the body. The red color of blood comes from hemoglobin, contained in red blood cells.
In multicellular organisms, most cells do not have direct contact with the external environment; their vital activity is ensured by the presence of the internal environment (blood, lymph, tissue fluid). From it they obtain the substances necessary for life and secrete metabolic products into it. The internal environment of the body is characterized by relative dynamic constancy of composition and physicochemical properties, which is called homeostasis. The morphological substrate that regulates metabolic processes between blood and tissues and maintains homeostasis is histo-hematic barriers, consisting of capillary endothelium, basement membrane, connective tissue, cellular lipoprotein membranes.
The concept of “blood system” includes: blood, hematopoietic organs (red bone marrow, lymph nodes, etc.), organs of blood destruction and regulatory mechanisms (regulatory neurohumoral apparatus). The blood system is one of the most important life support systems of the body and performs many functions. Stopping the heart and stopping blood flow immediately leads the body to death.
Physiological functions of blood:
4) thermoregulatory - regulation of body temperature by cooling energy-intensive organs and warming organs that lose heat;
5) homeostatic - maintaining the stability of a number of homeostasis constants: pH, osmotic pressure, isoionicity, etc.;
Leukocytes perform many functions:
1) protective - fight against foreign agents; they phagocytose (absorb) foreign bodies and destroy them;
2) antitoxic - production of antitoxins that neutralize microbial waste products;
3) production of antibodies that provide immunity, i.e. lack of sensitivity to infectious diseases;
4) participate in the development of all stages of inflammation, stimulate recovery (regenerative) processes in the body and accelerate wound healing;
5) enzymatic - they contain various enzymes necessary for phagocytosis;
6) participate in the processes of blood coagulation and fibrinolysis through the production of heparin, gnetamine, plasminogen activator, etc.;
7) are the central link of the body’s immune system, performing the function of immune surveillance (“censorship”), protection from everything foreign and maintaining genetic homeostasis (T-lymphocytes);
8) provide a transplant rejection reaction, destruction of their own mutant cells;
9) form active (endogenous) pyrogens and form a febrile reaction;
10) carry macromolecules with information necessary to control the genetic apparatus of other cells of the body; Through such intercellular interactions (creative connections), the integrity of the body is restored and maintained.
4 . Platelet or blood plate, is a formed element involved in blood clotting, necessary to maintain the integrity of the vascular wall. It is a round or oval non-nuclear formation with a diameter of 2-5 microns. Platelets are formed in the red bone marrow from giant cells - megakaryocytes. 1 μl (mm 3) of human blood normally contains 180-320 thousand platelets. An increase in the number of platelets in the peripheral blood is called thrombocytosis, a decrease is called thrombocytopenia. The lifespan of platelets is 2-10 days.
The main physiological properties of platelets are:
1) amoeboid mobility due to the formation of pseudopods;
2) phagocytosis, i.e. absorption foreign bodies and microbes;
3) adhesion to a foreign surface and gluing to each other, while they form 2-10 processes, due to which attachment occurs;
4) easy destructibility;
5) release and absorption of various biologically active substances such as serotonin, adrenaline, norepinephrine, etc.;
All these properties of platelets determine their participation in stopping bleeding.
Functions of platelets:
1) actively participate in the process of blood coagulation and blood clot dissolution (fibrinolysis);
2) participate in stopping bleeding (hemostasis) due to the biologically active compounds present in them;
3) perform a protective function due to the gluing (agglutination) of microbes and phagocytosis;
4) produce some enzymes (amylolytic, proteolytic, etc.) necessary for the normal functioning of platelets and for the process of stopping bleeding;
5) influence the state of histohematic barriers between blood and tissue fluid by changing the permeability of capillary walls;
6) transport creative substances important for maintaining the structure of the vascular wall; Without interaction with platelets, the vascular endothelium undergoes degeneration and begins to let red blood cells pass through it.
Erythrocyte sedimentation rate (reaction)(abbreviated ESR) is an indicator reflecting changes in the physicochemical properties of blood and the measured value of the plasma column released from red blood cells when they settle from a citrate mixture (5% sodium citrate solution) for 1 hour in a special pipette of the T.P. device. Panchenkova.
IN normal ESR is equal to:
For men - 1-10 mm/hour;
For women - 2-15 mm/hour;
Newborns - from 2 to 4 mm/h;
Children of the first year of life - from 3 to 10 mm/h;
Children aged 1-5 years - from 5 to 11 mm/h;
Children 6-14 years old - from 4 to 12 mm/h;
Over 14 years old - for girls - from 2 to 15 mm/h, and for boys - from 1 to 10 mm/h.
in pregnant women before childbirth - 40-50 mm/hour.
An increase in ESR greater than the specified values is, as a rule, a sign of pathology. The value of ESR does not depend on the properties of erythrocytes, but on the properties of plasma, primarily on the content of large molecular proteins in it - globulins and especially fibrinogen. The concentration of these proteins increases during all inflammatory processes. During pregnancy, the fibrinogen content before childbirth is almost 2 times higher than normal, so the ESR reaches 40-50 mm/hour.
Leukocytes have their own sedimentation regime, independent of erythrocytes. However, the leukocyte sedimentation rate is not taken into account in the clinic.
Hemostasis (Greek haime - blood, stasis - stationary state) is a stop of blood movement through a blood vessel, i.e. stop bleeding.
There are 2 mechanisms to stop bleeding:
1) vascular-platelet (microcirculatory) hemostasis;
2) coagulation hemostasis (blood clotting).
The first mechanism is capable of independently stopping bleeding from the most frequently injured small vessels with fairly low blood pressure in a few minutes.
It consists of two processes:
1) vascular spasm, leading to a temporary stop or reduction of bleeding;
2) formation, compaction and contraction of a platelet plug, leading to a complete stop of bleeding.
The second mechanism for stopping bleeding - blood clotting (hemocoagulation) ensures the cessation of blood loss when large vessels are damaged, mainly of the muscular type.
It is carried out in three phases:
Phase I - formation of prothrombinase;
Phase II - thrombin formation;
Phase III - conversion of fibrinogen to fibrin.
In the blood coagulation mechanism, in addition to the walls of blood vessels and formed elements, 15 plasma factors take part: fibrinogen, prothrombin, tissue thromboplastin, calcium, proaccelerin, convertin, antihemophilic globulins A and B, fibrin-stabilizing factor, prekallikrein (factor Fletcher), high molecular weight kininogen (Fitzgerald factor), etc.
Most of these factors are formed in the liver with the participation of vitamin K and are proenzymes related to the globulin fraction of plasma proteins. They pass into the active form - enzymes during the coagulation process. Moreover, each reaction is catalyzed by an enzyme formed as a result of the previous reaction.
The trigger for blood clotting is the release of thromboplastin by damaged tissue and decaying platelets. Calcium ions are required to carry out all phases of the coagulation process.
A blood clot is formed by a network of insoluble fibrin fibers and erythrocytes, leukocytes and platelets entangled in it. The strength of the resulting blood clot is ensured by factor XIII, a fibrin-stabilizing factor (fibrinase enzyme synthesized in the liver). Blood plasma devoid of fibrinogen and some other substances involved in coagulation is called serum. And blood from which fibrin has been removed is called defibrinated.
The normal time for complete coagulation of capillary blood is 3-5 minutes, for venous blood - 5-10 minutes.
In addition to the coagulation system, the body simultaneously has two more systems: anticoagulant and fibrinolytic.
The anticoagulation system interferes with the processes of intravascular blood coagulation or slows down hemocoagulation. The main anticoagulant of this system is heparin, secreted from lung and liver tissue, and produced by basophilic leukocytes and tissue basophils (mast cells of connective tissue). The number of basophilic leukocytes is very small, but all tissue basophils of the body have a mass of 1.5 kg. Heparin inhibits all phases of the blood coagulation process, suppresses the activity of many plasma factors and the dynamic transformations of platelets. Allocable salivary glands medical leeches hirudin acts depressingly on the third stage of the blood coagulation process, i.e. prevents the formation of fibrin.
The fibrinolytic system is capable of dissolving formed fibrin and blood clots and is the antipode of the coagulation system. The main function of fibrinolysis is the breakdown of fibrin and restoration of the lumen of a vessel clogged with a clot. The breakdown of fibrin is carried out by the proteolytic enzyme plasmin (fibrinolysin), which is found in the plasma in the form of the proenzyme plasminogen. To convert it into plasmin, there are activators contained in the blood and tissues, and inhibitors (lat. inhibere - restrain, stop), inhibiting the conversion of plasminogen into plasmin.
Disruption of the functional relationships between the coagulation, anticoagulation and fibrinolytic systems can lead to serious diseases: increased bleeding, intravascular thrombus formation and even embolism.
Blood groups- a set of characteristics characterizing the antigenic structure of erythrocytes and the specificity of anti-erythrocyte antibodies, which are taken into account when selecting blood for transfusions (Latin transfusio - transfusion).
In 1901, the Austrian K. Landsteiner and in 1903 the Czech J. Jansky discovered that when mixing the blood of different people, red blood cells often adhere to each other - the phenomenon of agglutination (lat. agglutinatio - gluing) with their subsequent destruction (hemolysis ). It was found that erythrocytes contain agglutinogens A and B, adhesive substances of glycolipid structure, and antigens. Agglutinins α and β, modified proteins of the globulin fraction, and antibodies that glue erythrocytes were found in the plasma.
Agglutinogens A and B in erythrocytes, like agglutinins α and β in plasma, may be present one at a time, together, or absent in different people. Agglutinogen A and agglutinin α, as well as B and β are called the same name. The adhesion of red blood cells occurs when the red blood cells of the donor (the person giving blood) meet the same agglutinins of the recipient (the person receiving blood), i.e. A + α, B + β or AB + αβ. From this it is clear that in the blood of every person there are opposite agglutinogen and agglutinin.
According to the classification of J. Jansky and K. Landsteiner, people have 4 combinations of agglutinogens and agglutinins, which are designated as follows: I(0) - αβ., II(A) - A β, Ш(В) - B α and IV(AB). From these designations it follows that in people of group 1, agglutinogens A and B are absent in their erythrocytes, and both agglutinins α and β are present in the plasma. In people of group II, red blood cells have agglutinogen A, and plasma has agglutinin β. Group III includes people who have agglutinin gene B in their erythrocytes and agglutinin α in their plasma. In people of group IV, erythrocytes contain both agglutinogens A and B, and agglutinins are absent in the plasma. Based on this, it is not difficult to imagine which groups can be transfused with blood of a certain group (Diagram 24).
As can be seen from the diagram, people of group I can only be transfused with blood of this group. Group I blood can be transfused to people of all groups. This is why people with blood group I are called universal donors. People with group IV can receive blood transfusions of all groups, which is why these people are called universal recipients. Group IV blood can be transfused to people with group IV blood. The blood of people of groups II and III can be transfused to people with the same, as well as with IV blood group.
However, currently in clinical practice only blood of the same group is transfused, and in small quantities (no more than 500 ml), or the missing blood components are transfused (component therapy). This is due to the fact that:
firstly, with large massive transfusions, dilution of the donor’s agglutinins does not occur, and they glue the recipient’s red blood cells together;
secondly, with a careful study of people with blood type I, immune agglutinins anti-A and anti-B were discovered (in 10-20% of people); transfusion of such blood to people with other blood groups causes severe complications. Therefore, people with blood group I, containing anti-A and anti-B agglutinins, are now called dangerous universal donors;
thirdly, many variants of each agglutinogen have been identified in the ABO system. Thus, agglutinogen A exists in more than 10 variants. The difference between them is that A1 is the strongest, and A2-A7 and other options have weak agglutination properties. Therefore, the blood of such individuals may be erroneously assigned to group I, which can lead to blood transfusion complications when transfused to patients with groups I and III. Agglutinogen B also exists in several variants, the activity of which decreases in the order of their numbering.
In 1930, K. Landsteiner, speaking at the ceremony of awarding him the Nobel Prize for the discovery of blood groups, suggested that in the future new agglutinogens will be discovered, and the number of blood groups will grow until it reaches the number of people living on earth . This scientist’s assumption turned out to be correct. To date, more than 500 different agglutinogens have been discovered in human erythrocytes. From these agglutinogens alone, more than 400 million combinations, or blood group characteristics, can be made.
If we take into account all the other agg-lutinogens found in the blood, then the number of combinations will reach 700 billion, i.e. significantly more than there are people on the globe. This determines amazing antigenic uniqueness, and in this sense, each person has his own blood group. These agglutinogen systems differ from the ABO system in that they do not contain natural agglutinins in the plasma, like α- and β-agglutinins. But under certain conditions, immune antibodies - agglutinins - can be produced to these agglutinogens. Therefore, it is not recommended to repeatedly transfuse blood to a patient from the same donor.
To determine blood groups, you need to have standard sera containing known agglutinins, or anti-A and anti-B coliclones containing diagnostic monoclonal antibodies. If you mix a drop of blood from a person whose group needs to be determined with serum of groups I, II, III or with anti-A and anti-B cyclones, then by the agglutination that occurs, you can determine his group.
Despite the simplicity of the method, in 7-10% of cases the blood type is determined incorrectly, and patients are given incompatible blood.
To avoid such a complication, before blood transfusion, be sure to:
1) determination of the blood group of the donor and recipient;
2) Rh blood of the donor and recipient;
3) test for individual compatibility;
4) biological test for compatibility during the transfusion process: first, 10-15 ml of donor blood is poured in and then the patient’s condition is observed for 3-5 minutes.
Transfused blood always has a multilateral effect. In clinical practice there are:
1) replacement effect - replacement of lost blood;
2) immunostimulating effect - to stimulate the defenses;
3) hemostatic (hemostatic) effect - to stop bleeding, especially internal;
4) neutralizing (detoxification) effect - in order to reduce intoxication;
5) nutritional effect - introduction of proteins, fats, carbohydrates in an easily digestible form.
In addition to the main agglutinogens A and B, erythrocytes may contain other additional ones, in particular the so-called Rh agglutinogen (Rh factor). It was first found in 1940 by K. Landsteiner and I. Wiener in the blood of a rhesus monkey. 85% of people have the same Rh agglutinogen in their blood. Such blood is called Rh-positive. Blood that lacks Rh agglutinogen is called Rh negative (in 15% of people). The Rh system has more than 40 varieties of agglutinogens - O, C, E, of which O is the most active.
A special feature of the Rh factor is that people do not have anti-Rhesus agglutinins. However, if a person with Rh-negative blood is repeatedly transfused with Rh-positive blood, then under the influence of the administered Rh agglutinogen, specific anti-Rh agglutinins and hemolysins are produced in the blood. In this case, transfusion of Rh-positive blood to this person can cause agglutination and hemolysis of red blood cells - transfusion shock will occur.
The Rh factor is inherited and has special meaning for the course of pregnancy. For example, if the mother does not have the Rh factor, but the father has it (the probability of such a marriage is 50%), then the fetus may inherit the Rh factor from the father and turn out to be Rh positive. The fetal blood enters the mother's body, causing the formation of anti-Rhesus agglutinins in her blood. If these antibodies cross the placenta back into the fetal blood, agglutination will occur. At high concentrations of anti-Rhesus agglutinins, fetal death and miscarriage can occur. In mild forms of Rh incompatibility, the fetus is born alive, but with hemolytic jaundice.
Rh conflict occurs only with a high concentration of anti-Rhesus glutinins. Most often, the first child is born normal, since the titer of these antibodies in the mother’s blood increases relatively slowly (over several months). But when a Rh-negative woman becomes pregnant again with a Rh-positive fetus, the threat of Rh-conflict increases due to the formation of new portions of anti-Rhesus agglutinins. Rh incompatibility during pregnancy is not very common: approximately one case in 700 births.
To prevent Rh conflict, pregnant Rh-negative women are prescribed anti-Rh gamma globulin, which neutralizes Rh-positive fetal antigens.
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