(leukopoiesis) and platelets (thrombocytopoiesis).
In adult animals, it takes place in the red bone marrow, where erythrocytes, all granular leukocytes, monocytes, platelets, B-lymphocytes and precursors of T-lymphocytes are formed. In the thymus, differentiation of T-lymphocytes takes place, in the spleen and lymph nodes - differentiation of B-lymphocytes and reproduction of T-lymphocytes.
The common ancestral cell of all blood cells is a pluripotent blood stem cell, which is capable of differentiation and can give rise to the growth of any blood cells and is capable of long-term self-maintenance. Each hematopoietic stem cell during its division turns into two daughter cells, one of which is included in the proliferation process, and the second goes to continue the class of pluripotent cells. Differentiation of stem hematopoietic cells occurs under the influence of humoral factors. As a result of development and differentiation, different cells acquire morphological and functional features.
Erythropoiesis takes place in the myeloid tissue of the bone marrow. The average lifespan of erythrocytes is 100-120 days. Up to 2 * 10 11 cells are formed per day.
Rice. Regulation of erythropoiesis
Regulation of erythropoiesis carried out by erythropoietins formed in the kidneys. Erythropoiesis is stimulated by male sex hormones, thyroxine and catecholamines. For the formation of red blood cells, vitamin B 12 and folic acid are needed, as well as an internal hematopoietic factor, which is formed in the gastric mucosa, iron, copper, cobalt, and vitamins. Under normal conditions, a small amount of erythropoietin is produced, which reaches the red brain cells and interacts with erythropoietin receptors, resulting in a change in the concentration of cAMP in the cell, which increases the synthesis of hemoglobin. Stimulation of erythropoiesis is also carried out under the influence of such non-specific factors as ACTH, glucocorticoids, catecholamines, androgens, as well as activation of the sympathetic nervous system.
RBCs are destroyed by intracellular hemolysis by mononuclear cells in the spleen and inside the vessels.
Leukopoiesis occurs in the red bone marrow and lymphoid tissue. This process is stimulated by specific growth factors, or leukopoetins, which act on certain precursors. An important role in leukopoiesis is played by interleukins, which enhance the growth of basophils and eosinophils. Leukopoiesis is also stimulated by the decay products of leukocytes and tissues, microorganisms, toxins.
Thrombocytopoiesis It is regulated by thrombopoietins, which are formed in the bone marrow, spleen, liver, as well as by interleukins. Thanks to thrombopoietins, the optimal ratio between the processes of destruction and formation of platelets is regulated.
Hemocytopoiesis and its regulation
Hemocytopoiesis (hematopoiesis, hematopoiesis) - a set of processes of transformation of hematopoietic stem cells into different types of mature blood cells (erythrocytes - erythropoiesis, leukocytes - leukopoiesis and platelets - thrombocytopoiesis), ensuring their natural loss in the body.
Modern ideas about hematopoiesis, including the differentiation pathways of pluripotent hematopoietic stem cells, the most important cytokines and hormones that regulate the processes of self-renewal, proliferation and differentiation of pluripotent stem cells into mature blood cells, are shown in Fig. one.
pluripotent hematopoietic stem cells are located in the red bone marrow and are capable of self-renewal. They can also circulate in the blood outside the hematopoietic organs. PSGCs of the bone marrow with normal differentiation give rise to all types of mature blood cells - erythrocytes, platelets, basophils, eosinophils, neutrophils, monocytes, B- and T-lymphocytes. To maintain the cellular composition of the blood at the proper level, an average of 2.00 is formed daily in the human body. 10 11 erythrocytes, 0.45 . 10 11 neutrophils, 0.01 . 10 11 monocytes, 1.75 . 10 11 platelets. In healthy people, these indicators are quite stable, although under conditions of increased demand (adaptation to high mountains, acute blood loss, infection), the processes of maturation of bone marrow precursors are accelerated. The high proliferative activity of stem hematopoietic cells is blocked by the physiological death (apoptosis) of their excess progeny (in the bone marrow, spleen or other organs), and, if necessary, of themselves.
Rice. Fig. 1. Hierarchical model of hemocytopoiesis, including differentiation pathways (PSGC) and the most important cytokines and hormones that regulate the processes of self-renewal, proliferation and differentiation of PSGC into mature blood cells: A - myeloid stem cell (CFU-HEMM), which is the precursor of monocytes, granulocytes, platelets and erythrocytes; B - lymphoid stem cell-precursor of lymphocytes
It is estimated that every day in the human body is lost (2-5). 10 11 blood cells, which will mix in an equal number of new ones. To satisfy this huge constant need of the body for new cells, hemocytopoiesis is not interrupted throughout life. On average, a person over 70 years of life (with a body weight of 70 kg) produces: erythrocytes - 460 kg, granulocytes and monocytes - 5400 kg, platelets - 40 kg, lymphocytes - 275 kg. Therefore, hematopoietic tissues are considered as one of the most mitotically active.
Modern ideas about hemocytopoiesis are based on the stem cell theory, the foundations of which were laid by the Russian hematologist A.A. Maximov at the beginning of the 20th century. According to this theory, all blood cells originate from a single (primary) pluripotent stem hematopoietic (hematopoietic) cell (PSHC). These cells are capable of long-term self-renewal and, as a result of differentiation, can give rise to any germ of blood cells (see Fig. 1.) and at the same time maintain their viability and properties.
Stem cells (SCs) are unique cells capable of self-renewal and differentiation not only into blood cells, but also into cells of other tissues. According to the origin and source of formation and isolation, SCs are divided into three groups: embryonic (SCs of the embryo and fetal tissues); regional, or somatic (SC of an adult organism); induced (SC obtained as a result of reprogramming of mature somatic cells). According to the ability to differentiate, toti-, pluri-, multi- and unipotent SCs are distinguished. Totipotent SC (zygote) reproduces all the organs of the embryo and the structures necessary for its development (placenta and umbilical cord). A pluripotent SC can be a source of cells derived from any of the three germ layers. Multi (poly) potent SC is able to form specialized cells of several types (for example, blood cells, liver cells). Under normal conditions, unipotent SC differentiates into specialized cells of a certain type. Embryonic SCs are pluripotent, while regional SCs are pluripotent or unipotent. The incidence of PSGC is on average 1:10,000 cells in red bone marrow and 1:100,000 cells in peripheral blood. Pluripotent SCs can be obtained as a result of reprogramming of somatic cells of various types: fibroblasts, keratinocytes, melanocytes, leukocytes, pancreatic β-cells, and others, with the participation of gene transcription factors or miRNAs.
All SCs have a number of common properties. First, they are undifferentiated and do not have structural components to perform specialized functions. Secondly, they are capable of proliferation with the formation of a large number (tens and hundreds of thousands) of cells. Thirdly, they are capable of differentiation, i.e. the process of specialization and the formation of mature cells (for example, erythrocytes, leukocytes, and platelets). Fourth, they are capable of asymmetric division, when two daughter cells are formed from each SC, one of which is identical to the parent and remains the stem (SC self-renewal property), and the other differentiates into specialized cells. Finally, fifthly, SCs can migrate to lesions and differentiate into mature forms of damaged cells, promoting tissue regeneration.
There are two periods of hemocytopoiesis: embryonic - in the embryo and fetus, and postnatal - from the moment of birth to the end of life. Embryonic hematopoiesis begins in the yolk sac, then outside it in the precordial mesenchyme, from 6 weeks of age it moves to the liver, and from 12 to 18 weeks of age to the spleen and red bone marrow. From 10 weeks of age, the formation of T-lymphocytes in the thymus begins. From the moment of birth, the main organ of hemocytopoiesis gradually becomes red bone marrow. Foci of hematopoiesis are present in an adult in 206 bones of the skeleton (sternum, ribs, vertebrae, epiphyses of tubular bones, etc.). In the red bone marrow, PSGC self-renewal and the formation of myeloid stem cells from them, also called the colony-forming unit of granulocytes, erythrocytes, monocytes, megakaryocytes (CFU-GEMM); lymphoid stem cell. Mysloid polyoligopotent stem cell (CFU-GEMM) can differentiate: into monopotent committed cells - precursors of erythrocytes, also called burst-forming unit (BFU-E), megakaryocytes (CFU-Mgcc); into polyoligopotent committed cells of granulocyte-monocytes (CFU-GM), differentiating into monopotent precursors of granulocytes (basophils, neutrophils, eosinophils) (CFU-G), and precursors of monocytes (CFU-M). The lymphoid stem cell is the precursor of T- and B-lymphocytes.
In the red bone marrow, from the listed colony-forming cells, through a series of intermediate stages, regiculocytes (precursors of erythrocytes), megakaryocytes (from which the platelet is “stripped off”, i), granulocytes (neutrophils, eosinophils, basophils), monocytes and B-lymphocytes are formed through a series of intermediate stages. In the thymus, spleen, lymph nodes and lymphoid tissue associated with the intestine (tonsils, adenoids, Peyer's patches), the formation and differentiation of T-lymphocytes and plasma cells from B-lymphocytes occurs. In the spleen, there are also processes of capture and destruction of blood cells (primarily erythrocytes and platelets) and their fragments.
In human red bone marrow, hemocytopoiesis can only occur in a normal hemocytopoiesis-inducing microenvironment (HIM). Various cellular elements that make up the stroma and parenchyma of the bone marrow take part in the formation of the GIM. GIM is formed by T-lymphocytes, macrophages, fibroblasts, adipocytes, endothelial cells of the vessels of the microvasculature, components of the extracellular matrix and nerve fibers. Elements of GIM control the processes of hematopoiesis both with the help of cytokines and growth factors produced by them, and through direct contact with hematopoietic cells. The HIM structures fix stem cells and other progenitor cells in certain areas of the hematopoietic tissue, transmit regulatory signals to them, and participate in their metabolic supply.
Hemocytopoiesis is controlled by complex mechanisms that can maintain it relatively constant, accelerate or inhibit it, inhibiting cell proliferation and differentiation up to the initiation of apoptosis of committed precursor cells and even individual PSGCs.
Regulation of hematopoiesis- this is a change in the intensity of hematopoiesis in accordance with the changing needs of the body, carried out by means of its acceleration or deceleration.
For a complete hemocytopoiesis, it is necessary:
- receipt of signal information (cytokines, hormones, neurotransmitters) about the state of the cellular composition of the blood and its functions;
- providing this process with a sufficient amount of energy and plastic substances, vitamins, mineral macro- and microelements, water. The regulation of hematopoiesis is based on the fact that all types of adult blood cells are formed from hematopoietic stem cells of the bone marrow, the direction of differentiation of which into various types of blood cells is determined by the action of local and systemic signaling molecules on their receptors.
The role of external signal information for the proliferation and apoptosis of SHC is performed by cytokines, hormones, neurotransmitters, and microenvironmental factors. Among them, early-acting and late-acting, multilinear and monolinear factors are distinguished. Some of them stimulate hematopoiesis, others inhibit it. The role of internal regulators of pluripotency or SC differentiation is played by transcription factors acting in cell nuclei.
The specificity of the effect on stem hematopoietic cells is usually achieved by the action of not one, but several factors at once. The effects of factors are achieved by stimulating specific receptors of hematopoietic cells, the set of which changes at each stage of differentiation of these cells.
Early-acting growth factors that promote survival, growth, maturation and transformation of stem and other hematopoietic precursor cells of several blood cell lines are stem cell factor (SCF), IL-3, IL-6, GM-CSF, IL-1, IL- 4, IL-11, LIF.
The development and differentiation of blood cells, predominantly of one line, is determined by late-acting growth factors - G-CSF, M-CSF, EPO, TPO, IL-5.
Factors that inhibit the proliferation of hematopoietic cells are transforming growth factor (TRFβ), macrophage inflammatory protein (MIP-1β), tumor necrosis factor (TNFa), interferons (IFN(3, IFNy), lactoferrin.
The action of cytokines, growth factors, hormones (erythropoietin, growth hormone, etc.) on the cells of hematopoietic organs is most often realized through stimulation of 1-TMS- and less often 7-TMS-receptors of plasma membranes and less often through stimulation of intracellular receptors (glucocorticoids, T 3 IT 4).
For normal functioning, hematopoietic tissue needs a number of vitamins and microelements.
vitamins
Vitamin B12 and folic acid are needed for the synthesis of nucleoproteins, maturation and cell division. To protect against destruction in the stomach and absorption in the small intestine, vitamin B 12 needs a glycoprotein (internal Castle factor), which is produced by the parietal cells of the stomach. With a deficiency of these vitamins in food or the absence of the internal factor of Castle (for example, after surgical removal of the stomach), a person develops hyperchromic macrocytic anemia, hypersegmentation of neutrophils and a decrease in their production, as well as thrombocytopenia. Vitamin B 6 is needed for the synthesis of the subject. Vitamin C promotes metabolism (rhodic acid and is involved in iron metabolism. Vitamins E and PP protect the erythrocyte membrane and heme from oxidation. Vitamin B2 is needed to stimulate redox processes in bone marrow cells.
trace elements
Iron, copper, cobalt are needed for the synthesis of heme and hemoglobin, the maturation of erythroblasts and their differentiation, stimulation of the synthesis of erythropoietin in the kidneys and liver, and the performance of the gas transport function of erythrocytes. Under conditions of their deficiency, hypochromic, microcytic anemia develops in the body. Selenium enhances the antioxidant effect of vitamins E and PP, and zinc is necessary for the normal functioning of the carbonic anhydrase enzyme.
Hematopoiesis is a complex set of mechanisms that ensure the formation and destruction of blood cells.
Hematopoiesis is carried out in special organs: liver, red bone marrow, spleen, thymus, lymph nodes. There are two periods of hematopoiesis: embryonic and postnatal.
According to the modern concept, a single maternal hematopoietic cell is stem cell, from which, through a series of intermediate stages, erythrocytes, leukocytes and platelets are formed.
red blood cells formed intravascular(inside the vessel) in the sinuses of the red bone marrow.
Leukocytes formed extravascular(outside the vessel). At the same time, granulocytes and monocytes mature in the red bone marrow, and lymphocytes in the thymus, lymph nodes, and spleen.
platelets formed from giant cells megakaryocytes in red bone marrow and lungs. They also develop outside the vessel.
The formation of blood cells occurs under the control of humoral and nervous mechanisms of regulation.
Humoral regulation components are divided into two groups: exogenous and endogenous factors.
TO exogenous factors include biologically active substances, B vitamins, vitamin C, folic acid, and trace elements. These substances, influencing the enzymatic processes in the hematopoietic organs, contribute to the differentiation of formed elements, the synthesis of their constituent parts.
TO endogenous factors relate:
The Castle Factor- a complex combination in which the so-called external and internal factors are distinguished. The external factor is vitamin B 12, internal - a substance of a protein nature, which is formed by additional cells of the glands of the fundus of the stomach. The intrinsic factor protects vitamin B 12 from destruction by hydrochloric acid of gastric juice and promotes its absorption in the intestine. The Castle factor stimulates erythropoiesis.
Hematopoietins- products of the breakdown of blood cells, which have a stimulating effect on hematopoiesis.
Erythropoietins, leukopoetins and thrombopoietins- increase the functional activity of hematopoietic organs, provide faster maturation of the corresponding blood cells.
A certain place in the regulation of hematopoiesis belongs to the endocrine glands and their hormones. With increased activity pituitary gland there is stimulation of hematopoiesis, with hypofunction - severe anemia. Hormones thyroid gland necessary for the maturation of erythrocytes, with its hyperfunction, erythrocytosis is observed.
Autonomic nervous system and its higher subcortical center - hypothalamus- have a pronounced effect on hematopoiesis. The excitation of the sympathetic department is accompanied by its stimulation, the parasympathetic - by inhibition.
Excitation neurons in the cerebral cortex accompanied by stimulation of hematopoiesis, and inhibition - its oppression.
Thus, the functional activity of the organs of hematopoiesis and blood destruction is ensured by complex relationships between the nervous and humoral mechanisms of regulation, on which the preservation of the constancy of the composition and properties of the universal internal environment of the body ultimately depends.
MOVEMENT PROCESS
GENERAL QUESTIONS OF OSTEOLOGY AND SYNDESMOLOGY
musculoskeletal system
One of the most important adaptations of the human body to the environment is motion. It is carried out using musculoskeletal system(ODA), which unites bones, their joints and skeletal muscles. The musculoskeletal system is divided into passive part and active parts .
TO passive parts include bones and their joints, on which the nature of the movements of body parts depends, but they themselves cannot perform movement.
The active part consists of the skeletal muscles, which have the ability to contract and set in motion the bones of the skeleton (levers).
ODA performs the most important functions in the body:
1. support : the skeleton is the support of the human body, and soft tissues and organs are attached to different parts of the skeleton. The support function of the spine and lower extremities is most pronounced;
Normally, the number of erythrocytes formed corresponds to the number of destroyed, and their total number remains surprisingly constant.
With oxygen starvation caused by any reason, the number of red blood cells in the blood increases. Local oxygen starvation of the bone marrow does not lead to increased erythropoiesis.
Studies have shown that the blood plasma of an animal subjected to oxygen starvation, when transfused into a normal animal, stimulates erythropoiesis in it. With oxygen starvation (caused by anemia, inhalation of gas mixtures with a low oxygen content, prolonged stay at high altitudes, respiratory diseases, etc.), substances stimulating hematopoiesis appear in the body - erythropoietins. The latter are glycoproteins of small molecular weight. In animals, after removal of the kidneys, erythropoietins do not appear in the blood. Therefore, it is believed that the formation of erythropoietins occurs in the kidneys.
With impaired production of erythropoietins, many researchers associate various diseases of the blood system, such as insufficient formation of red blood cells and a decrease in their number in the blood (anemia), and their excessive production and increase in their number (polycythemia).
The intensity of leukocyte production - leukopoiesis - depends mainly on the action of certain nucleic acids and their derivatives. Substances that stimulate leukopoiesis are tissue breakdown products that occur during damage, inflammation, etc. Under the influence of pituitary hormones - adrenocorticotropic hormone and growth hormone - the number of neutrophils increases and the number of eosinophils in the blood decreases.
According to a number of studies, the nervous system plays a role in stimulating erythropoiesis. In the laboratory of S.P. Botkin, back in the 80s of the last century, it was shown that when the nerves leading to the bone marrow are irritated, the content of red blood cells in dogs increases. Irritation of the sympathetic nerves also causes an increase in the number of neutrophilic leukocytes in the blood.
According to F. Chubalsky, irritation of the vagus nerve causes a redistribution of leukocytes in the blood: their content increases in the blood of mesenteric vessels and decreases in the blood of peripheral vessels; stimulation of the sympathetic nerves has the opposite effect. Pain irritation and emotional arousal increase the number of leukocytes in the blood.
After eating, in the midst of gastric digestion, the content of leukocytes in the blood circulating in the vessels increases. This phenomenon is called redistributive, or digestive, leukocytosis.
IP Pavlov's students showed that digestive leukocytosis can also be caused by a conditioned reflex.
The organs of the blood system (bone marrow, spleen, liver, lymph nodes) contain a large number of receptors, the irritation of which, according to the experiments of V. N. Chernigovsky, causes various physiological reactions. Thus, there is a two-way connection between these organs and the nervous system: they receive signals from the central nervous system (which regulate their state) and are, in turn, a source of reflexes that change the state of themselves and the body as a whole.
Hematopoiesis (hemocytopoiesis) is a complex, multi-stage process of formation, development and maturation of blood cells. During intrauterine development, the yolk sac, liver, bone marrow, and spleen perform a universal hematopoietic function. In the postnatal (after birth) period, the hematopoietic function of the liver and spleen is lost, and the red bone marrow remains the main hematopoietic organ. It is believed that the ancestor of all blood cells is the bone marrow stem cell, which gives rise to other blood cells.
The humoral regulator of erythropoiesis is erythropoietins produced in the kidneys, liver, and spleen. Synthesis and secretion of erythropoietins depends on the level of oxygenation of the kidneys. In all cases of oxygen deficiency in tissues (hypoxia) and in the blood (hypoxemia), the formation of erythropoietins increases. Adrenocorticotropic, somatotropic hormones of the pituitary gland, thyroxine, male sex hormones (androgens) activate erythropoiesis, and female sex hormones inhibit it.
For the formation of red blood cells, it is necessary to supply vitamin B 12, folic acid, vitamins B 6, C, E, elements of iron, copper, cobalt, manganese, which constitute the external factor of erythropoiesis. Along with this, the so-called internal factor of Castle, which is formed in the gastric mucosa, plays an important role, which is necessary for the absorption of vitamin B 12.
In the regulation of leukocytopoiesis, which ensures the maintenance of the total number of leukocytes and its individual forms at the required level, substances of a hormonal nature, leukopoetins, are involved. It is assumed that each row of leukocytes may have its own specific leukopoetins formed in various organs (lungs, liver, spleen, etc.). Leukocytopoiesis is stimulated by nucleic acids, decay products of tissues and leukocytes themselves.
Adrenotropic and somatotropic hormones of the pituitary gland increase the number of neutrophils, but reduce the number of eosinophils. The presence of interoreceptors in the hematopoietic organs serves as undoubted evidence of the influence of the nervous system on the processes of hematopoiesis. There are data on the influence of the vagus and sympathetic nerves on the redistribution of leukocytes in different parts of the vascular bed of animals. All this indicates that hematopoiesis is under the control of the neurohumoral mechanism of regulation.
Control questions: 1. The concept of the blood system. 2. Basic functions of blood. 3. Plasma and blood serum. 4. Physical and chemical properties of blood (viscosity, density, reaction, osmotic and oncotic pressure). 5. Red blood cells, their structure and functions. 6. ESR, Hemoglobin. Combination of hemoglobin with different gases. 7. Leukocytes, their types, functions. 8. Leukogram - coagulation and anticoagulation system of blood.
Chapter 2. Immunity and the immune system
Immunology is a science that studies the body's reactions to violations of the constancy of its internal environment. The central concept of immunology is immunity.
Immunity¾ is a way to protect the body from living bodies and substances that carry genetically alien information (viruses, bacteria, their toxins, genetically alien cells and tissues, etc.). This protection is aimed at maintaining the constancy of the internal environment (homeostasis) of the body and the result of them can be various phenomena of immunity. Some of them are useful, others cause pathology. The first ones include:
· ¾ immunity of the body to infectious agents ¾ pathogens (microbes, viruses);
· Tolerance¾ tolerance, non-response to one's own biologically active substances, one of the variants of which is anergy, i.e. no reaction. The immune system normally does not respond to "its own" and rejects "foreign".
Other phenomena of immunity lead to the development of the disease:
· autoimmunity includes reactions of the immune system to its own (not foreign) substances, i.e. for autoantigens. In autoimmune reactions, “self” molecules are recognized as “foreign” and reactions develop on them;
· Hypersensitivity¾ hypersensitivity (allergy) to allergen antigens, which leads to the development of allergic diseases.
Immunological memory is the basis for the manifestation of immunity phenomena. The essence of this phenomenon lies in the fact that the cells of the immune system "remember" those foreign substances with which they met and to which they reacted. Immunological memory underlies the phenomena of immunity, tolerance and hypersensitivity.
Types of immunity
According to the mechanism of development There are the following types of immunity:
· Species immunity(constitutional, hereditary) ¾ is a special variant of nonspecific resistance of the organism, genetically determined by the characteristics of the metabolism of this species. It is mainly associated with the lack of necessary conditions for the reproduction of the pathogen. For example, animals do not suffer from some human diseases (syphilis, gonorrhea, dysentery), and, conversely, people are not susceptible to the causative agent of dog distemper. Strictly speaking, this resistance variant is not true immunity, since it is not carried out by the immune system. However, there are variants of species immunity due to natural, preexisting antibodies. Such antibodies are available in small quantities against many bacteria and viruses.
· acquired immunity occurs during life. It can be natural and artificial, each of which can be active and passive.
· natural active immunity appears as a result of contact with the pathogen (after an illness or after hidden contact without symptoms of the disease).
· Natural passive immunity occurs as a result of the transfer from mother to fetus through the placenta (transplantation) or with milk (colostral) of ready-made protective factors ¾ of lymphocytes, antibodies, cytokines, etc.
· artificial active immunity induced after the introduction into the body of vaccines containing microorganisms or their substances ¾ antigens.
· artificial passive immunity is created after the introduction of ready-made antibodies or immune cells into the body. Such antibodies are found in the blood serum of immunized donors or animals.
By reacting systems Distinguish between local and general immunity. In local immunity non-specific protective factors are involved, as well as secretory immunoglobulins, which are located on the mucous membranes of the intestines, bronchi, nose, etc.
Depending on whether what factor is the body struggling with, Distinguish between anti-infective and non-infectious immunity.
Anti-infective immunity¾ a set of reactions of the immune system aimed at removing an infectious agent (pathogen).
Depending on the type of infectious agent, the following types of anti-infective immunity are distinguished:
antibacterial¾ against bacteria;
antitoxic¾ against waste products of microbial toxins;
antiviral¾ against viruses or their antigens;
antifungal¾ against pathogenic fungi;
Immunity is always specific, directed against a specific pathogen, virus, bacterium. Therefore, there is immunity to one pathogen (for example, the measles virus), but not to another (influenza virus). This specificity and specificity is determined by antibodies and immune T cell receptors against the respective antigens.
Non-infectious immunity¾ a set of reactions of the immune system aimed at non-infectious biologically active agents-antigens. Depending on the nature of these antigens, it is divided into the following types:
autoimmunity¾ autoimmune reactions of the immune system to its own antigens (proteins, lipoproteins, glycoproteins);
transplant immunity occurs during transplantation of organs and tissues from a donor to a recipient, in cases of blood transfusion and immunization with leukocytes. These reactions are associated with the presence of individual sets of molecules on the surface of leukocytes;
antitumor immunity¾ is the reaction of the immune system to the antigens of tumor cells;
reproductive immunity in the system "mother ¾ fetus". This is the reaction of the mother to the antigens of the fetus, since it differs in them due to genes received from the father.
Depending on the body defense mechanisms distinguish between cellular and humoral immunity.
Cellular immunity is determined by the formation of T-lymphocytes that specifically react with the pathogen (antigen).
Humoral immunity occurs due to the production of specific antibodies.
If, after an illness, the body is freed from the pathogen, while maintaining a state of immunity, then such immunity is called sterile. However, in many infectious diseases, immunity is maintained only as long as the pathogen is in the body and this immunity is called non-sterile.
The immune system is involved in the development of these types of immunity, which is characterized by three features: it is generalized, that is, distributed throughout the body, its cells constantly recirculate through the bloodstream, and it produces strictly specific antibodies.
The body's immune system
The immune system is a collection of all lymphoid organs and cells of the body.
All organs of the immune system are divided into central (primary) and peripheral (secondary). The central organs include the thymus and bone marrow (in birds ¾ of the bursa of Fabricius), and the peripheral organs include the lymph nodes, spleen, lymphoid tissue of the gastrointestinal tract, respiratory organs, urinary tract, skin, as well as blood and lymph.
The main cellular form of the immune system are lymphocytes. Depending on the place of origin, these cells are divided into two large groups: T-lymphocytes and B-lymphocytes. Both groups of cells originate from the same precursor ¾ of the ancestral hematopoietic stem cell.
In the thymus, under the influence of its hormones, antigen-dependent differentiation of T-cells into immunocompetent cells occurs, which acquire the ability to recognize the antigen.
There are several different subpopulations of T-lymphocytes with different biological properties. These are T-helpers, T-killers, T-effectors, T-amplifiers, T-suppressors, T-cells of immune memory.
· T-helpers belong to the category of regulatory auxiliary cells, stimulating T- and B-lymphocytes to proliferation and differentiation. It has been established that the response of B-lymphocytes to most protein antigens depends entirely on the help of T-helpers.
· T-effectors under the influence of foreign antigens that have entered the body, they form part of the sensitized lymphocytes ¾T-killers (killers). These cells exhibit specific cytotoxicity towards target cells as a result of direct contact.
· T-amplifires(amplifiers) in their function resemble T-helpers, with the difference, however, that T-amplifiers activate the immune response within the T-subsystem of immunity, and T-helpers provide the possibility of its development in the B-link of immunity.
· T-suppressors provide internal self-regulation of the immune system. They perform a dual function. On the one hand, suppressor cells limit the immune response to antigens, on the other hand, they prevent the development of autoimmune reactions.
· T-lymphocytes immune memory provide a secondary type of immune response in case of repeated contact of the body with this antigen.
· V-lymphocytes in birds, they mature in the bag of Fabricius. Hence, these cells are called "B-lymphocytes". In mammals, this transformation occurs in the bone marrow. B-lymphocytes are larger cells than T-lymphocytes. B-lymphocytes under the influence of antigens, migrating to lymphoid tissues, turn into plasma cells that synthesize immunoglobulins of the corresponding classes.
Antibodies (immunoglobulins)
The main function of B-lymphocytes, as noted, is the formation of antibodies. During electrophoresis, most immunoglobulins (denoted by the symbol Iq) are localized in the gamma globulin fraction. Antibodies are immunoglobulins that can specifically bind to antigens.
Immunoglobulins- the basis of the protective functions of the body. Their level reflects the functional ability of immunocompetent B cells to a specific response to antigen introduction, as well as the degree of activity of immunogenesis processes. According to the international classification developed by WHO experts in 1964, immunoglobulins are divided into five classes: IgG, IgA, IgM, IgD, IgE. The first three classes are the most studied.
Each class of immunoglobulins is characterized by specific physicochemical and biological properties.
The most studied IgG. They account for 75% of all immunoglobulins in blood serum. Four subclasses of IgG 1 , IgG 2 , IgG 3 , and IgG 4 have been identified, differing in heavy chain structure and biological properties. Usually, IgG predominates in the secondary immune response. This immunoglobulin is associated with protection against viruses, toxins, gram-positive bacteria.
IgA make up 15-20% of all serum immunoglobulins. Fast catabolism and a slow rate of synthesis are ¾ the reason for the low content of immunoglobulin in the blood serum. IgA antibodies do not bind complement, are thermotable. Found two subclasses of IgA ¾ serum and secretory.
Secretory IgA contained in various secrets (tears, intestinal juice, bile, colostrum, bronchial secretions, nasal secretions, saliva) are a special form of IgA absent in blood serum. Significant amounts of secretory IgA, exceeding its content in the blood by 8-12 times, were found in the lymph.
Secretory IgA affects viral, bacterial and fungal, food antigens. Secretory IgA antibodies protect the body from the penetration of viruses into the blood at the site of their introduction.
IgM make up 10% of all immunoglobulins in blood serum. The macroglobulin antibody system is onto- and phylogenetically earlier than other immunoglobulins. They are usually formed during the primary immune response in the early stages after the introduction of the antigen, as well as in the fetus and newborn. The molecular weight of IgM is about 900 thousand. Due to the large molecular weight of IgM, corpuscular antigens are well agglutinated, and they also lyse erythrocytes and bacterial cells. There are two types of IgM, differing in their ability to bind a compliment.
IgM do not pass through the placenta, and an increase in the amount of IgG causes inhibition of the formation of IgM, and, conversely, with inhibition of IgG synthesis, a compensatory increase in IgM synthesis is often found.
IgD make up about 1% of the total number of immunoglobulins. The molecular weight is about 180 thousand. It has been established that its level increases with bacterial infections, chronic inflammatory diseases; and also talk about the possible role of IgM in the development of autoimmune diseases and the processes of lymphocyte differentiation.
IgE - (reagins) play an important role in the formation of allergic reactions and make up 0.6–0.7% of the total amount of immunoglobulins. The molecular weight of IgE is 200 thousand. These immunoglobulins play a leading role in the pathogenesis of a number of allergic diseases.
Reagins are synthesized in the plasma cells of regional lymph nodes, tonsils, bronchial mucosa and the gastrointestinal tract. This indicates not only the place of their formation, but also an important role in local allergic reactions, as well as in the protection of mucous membranes from respiratory infections.
Common to all classes of immunoglobulins is that their number in the body depends on age, sex, species, feeding conditions, maintenance and care, the state of the nervous and endocrine systems. The influence of genetic factors and climatic and geographical environment on their content was also revealed.
Antibodies by interaction with the antigen are divided into:
· neutralizins- neutralizing antigen;
· agglutinins- gluing antigen.;
· lysines- lysing the antigen with the participation of complement;
· precipitins- precipitating antigen;
· opsonins- enhancing phagocytosis.
Antigens
Antigens(from lat. anti- against, genos- genus, origin) ¾ all those substances that carry signs of genetic alienness and, when ingested, cause the formation of immunological reactions and specifically interact with their products.
Sometimes an antigen, once in the body, causes not an immune response, but a state of tolerance. Such a situation can arise when the antigen is introduced into the embryonic period of fetal development, when the immune system is immature and is just being formed, or when it is sharply suppressed or under the action of immunosuppressants.
Antigens are high-molecular compounds that are characterized by such properties as: foreignness, antigenicity, immunogenicity, specificity (an example can be viruses, bacteria, microscopic fungi, protozoa, exo- and endotoxins of microorganisms, cells of animal and plant origin, animal and plant poisons, etc. .).
antigenicity is the ability of an antigen to elicit an immune response. Its severity will be different for different antigens, since an unequal amount of antibodies is produced for each antigen.
Under immunogenicity understand the ability of an antigen to confer immunity. This concept mainly refers to microorganisms that provide immunity to infectious diseases.
Specificity- this is the ability of the structure of substances by which antigens differ from each other.
The specificity of antigens of animal origin is divided into:
· species specificity. In animals of different species, they have antigens that are characteristic only of this species, which is used in determining the falsification of meat, blood groups by using anti-species sera;
· G group specificity characterizing the antigenic differences of animals in terms of erythrocyte polysaccharides, blood serum proteins, surface antigens of nuclear somatic cells. Antigens that cause intraspecific differences between individuals or groups of individuals are called isoantigens, for example, group human erythrocyte antigens;
· organ (tissue) specificity, characterizing the unequal antigenicity of different organs of the animal, for example, the liver, kidneys, spleen differ in antigens;
· stage-specific antigens arise in the process of embryogenesis and characterize a certain stage in the intrauterine development of the animal, its individual parenchymal organs.
Antigens are divided into complete and defective.
Complete antigens cause in the body the synthesis of antibodies or the sensitization of lymphocytes and react with them both in vivo and in vitro. Complete antigens are characterized by strict specificity, i.e. they cause in the body the production of only specific antibodies that react only with this antigen.
Complete antigens are natural or synthetic biopolymers, most often proteins and their complex compounds (glycoproteins, lipoproteins, nucleoproteins), as well as polysaccharides.
Incomplete antigens or haptens, under normal conditions do not cause an immune response. However, when bound to high molecular weight molecules - "carriers" they become immunogenic. Haptens include drugs and most chemicals. They are able to trigger an immune response after binding to body proteins, such as albumin, as well as proteins on the surface of cells (erythrocytes, leukocytes). As a result, antibodies are formed that can interact with the hapten. When the hapten enters the body again, a secondary immune response occurs, often in the form of an increased allergic reaction.
Antigens or haptens that cause an allergic reaction when re-introduced into the body are called allergens. Therefore, all antigens and haptens can be allergens.
According to the etiological classification, antigens are divided into two main types: exogenous and endogenous (self-antigens). exogenous antigens enter the body from the external environment. Among them, infectious and non-infectious antigens are distinguished.
infectious antigens- these are antigens of bacteria, viruses, fungi, protozoa that enter the body through the mucous membranes of the nose, mouth, gastrointestinal tract, urinary tract, and also through damaged, and sometimes intact skin.
to non-infectious antigens include plant antigens, drugs, chemical, natural and synthetic substances, animal and human antigens.
Under endogenous antigens understand their own autologous molecules (autoantigens) or their complex complexes, which, for various reasons, cause the activation of the immune system. Most often this is due to a violation of autotolerance.
Dynamics of the immune response
In the development of the antibacterial immune response, two phases are distinguished: inductive and productive.
· I phase. When an antigen enters the body, microphages and macrophages are the first to fight. The first of them digest the antigen, depriving it of antigenic properties. Macrophages act on the bacterial antigen in two ways: firstly, they do not digest it themselves, and secondly, they transmit information about the antigen to T- and B-lymphocytes.
· II phase. Under the influence of information received from macrophages, B-lymphocytes are transformed into plasma cells and T-lymphocytes ¾ into immune T-lymphocytes. At the same time, some of the T- and B-lymphocytes are transformed into immune memory lymphocytes. In the primary immune response, IgM is synthesized first, followed by IgG. At the same time, the level of immune T-lymphocytes increases, antigen-antibody complexes are formed. Depending on the type of antigen, either immune T-lymphocytes or antibodies predominate.
With a secondary immune response due to memory cells, stimulation of the synthesis of antibodies and immune T-cells occurs quickly (after 1-3 days), the number of antibodies increases sharply. In this case, IgG is immediately synthesized, the titers of which are many times greater than with the primary response. Against viruses and some intracellular bacteria (chlamydin, rickettsin), immunity develops somewhat differently.
The more contact with antigens, the higher the level of antibodies. This phenomenon is used in immunization (repeated administration of an antigen to animals) in order to obtain antisera, which are used for diagnosis and treatment.
Immunopathology includes diseases based on disorders in the immune system.
There are three main type of immunopathology:
Diseases associated with inhibition of immune reactions (immunodeficiencies);
diseases associated with increased immune response (allergies and autoimmune diseases);
Diseases with impaired cell proliferation of the immune system and the synthesis of immunoglobulins (leukemia, paraproteinemia).
Immunodeficiencies or immune deficiency is manifested by the fact that the body is not able to respond with a full immune response to the antigen.
By origin, immunodeficiencies are divided into:
primary - congenital, often genetically determined. They may be associated with the absence or decrease in the activity of genes that control the maturation of immunocomplementary cells or with pathology in the process of intrauterine development;
secondary - acquired, arise under the influence of adverse endo- and exogenous factors after birth;
age-related or physiological, occur in young animals in the molosin and milk period.
Young farm animals usually have age-related and acquired immune deficiencies. The cause of age-related immune deficiencies in young animals in the colostrum and milk periods is the lack of immunoglobulins and leukocytes in colostrum, the untimely receipt of it, as well as the immaturity of the immune system.
In young animals of the colostrum and milk periods, two age-related immune deficiencies are noted - in the neonatal period and at the 2–3rd week of life. The main factor in the development of age-related immune deficiencies is the insufficiency of humoral immunity.
The physiological deficiency of immunoglobulins and leukocytes in newborns is compensated by their intake with the mother's colostrum. However, with the immunological inferiority of colostrum, its untimely intake by newborn animals, impaired absorption in the intestine, age-related immune deficiency is aggravated. In such animals, the content of immunoglobulins and leukocytes in the blood remains at a low level, most of them develop acute gastrointestinal disorders.
The second age-related immune deficiency in young animals usually occurs at the 2nd or 3rd week of life. By this time, most of the colostral protective factors are consumed, and the formation of one's own is still at a low level. It should be noted that under good conditions for feeding and keeping young animals, this deficit is weakly expressed and shifted to a later time.
The veterinarian should monitor the immunological quality of colostrum. Good results were obtained by correcting immune deficiencies by using various immunomodulators (thymalin, thymopoietin, T-activin, thymazine, etc.).
Achievements in immunology are widely used in establishing the offspring of animals, in the diagnosis, treatment and prevention of diseases, etc.
Control questions: 1. What is immunity? 2. What are antibodies, antigens? 3. Types of immunity? 4. What is the body's immune system? 5. Function of T- and B-lymphocytes in the immune response? 6. What are immunodeficiencies and their types?
Chapter 3. The work of the heart and the movement of blood through the vessels
Blood can perform its important and diverse functions only under the condition of its continuous movement, provided by the activity of the cardiovascular system.
In the work of the heart, there is a continuous, rhythmically repeating alternation of its contractions (systole) and relaxation (diastole). The systole of the atria and ventricles, their diastole constitute the cardiac cycle.
The first phase of the cardiac cycle is atrial systole and ventricular diastole. The systole of the right atrium begins somewhat earlier than the left. By the beginning of atrial systole, the myocardium is relaxed and the cavities of the heart are filled with blood, the cusp valves are open. Blood enters the ventricles through the open cusp valves, which were mostly already filled with blood during total diastole. The reverse flow of blood from the atria to the veins is prevented by ring-shaped muscles located at the mouth of the veins, with the contraction of which the atrial systole begins.
In the second phase of the cardiac cycle, atrial diastole and ventricular systole are observed. Atrial diastole lasts much longer than systole. It captures the time of the entire systole of the ventricles and most of their diastole. The atria at this time are filled with blood.
In ventricular systole, two periods are distinguished: a period of tension (when all fibers are engulfed by excitation and contraction) and a period of expulsion (when pressure begins to rise in the ventricles and the flap valves close, the semilunar valve flaps move apart, and blood is expelled from the ventricles).
In the third phase, general diastole (diastole of the atria and ventricles) is noted. At this time, the pressure in the vessels is already higher than in the ventricles, and the semilunar valves close, preventing the return of blood to the ventricles, and the heart is filled with blood from the venous vessels.
The following factors ensure the filling of the heart with blood: the remnant of the driving force from the previous contraction of the heart, the suction capacity of the chest, especially during inspiration, and the suction of blood into the atria during ventricular systole, when the atria expand due to the atrioventricular septum being pulled down.
Heart rate (in 1 min): in horses 30 - 40, in cows, sheep, pigs - 60 - 80, in dogs - 70 - 80, in rabbits 120 - 140. With a more frequent rhythm (tachycardia), the heart cycle is shortened in by reducing the time for diastole, and with very frequent - and by shortening the systole.
With a decrease in heart rate (bradycardia), the phases of filling and expulsion of blood from the ventricles are prolonged.
The cardiac muscle, like any other muscle, has a number of physiological properties: excitability, conductivity, contractility, refractoriness and automaticity.
Excitability is the ability of the heart muscle to be excited by the action of mechanical, chemical, electrical and other stimuli on it. A feature of the excitability of the heart muscle is that it obeys the law "all - or nothing." This means that the heart muscle does not respond to a weak, sub-threshold stimulus (i.e., it is not excited and does not contract), but the heart muscle reacts to a threshold stimulus sufficient to excite the force with its maximum contraction and with a further increase in the strength of stimulation, the response from the side of the heart does not change.
· Conductivity is the ability of the heart to conduct excitation. The speed of excitation in the working myocardium of different parts of the heart is not the same. In the atrial myocardium, excitation spreads at a speed of 0.8 - 1 m / s, in the ventricular myocardium - 0.8 - 0.9 m / s. In the atrioventricular node, the conduction of excitation slows down to 0.02-0.05 m/s, which is almost 20-50 times slower than in the atria. As a result of this delay, ventricular excitation begins 0.12–0.18 s later than the onset of atrial excitation. This delay has a great biological meaning - it ensures the coordinated work of the atria and ventricles.
Refractoriness - a state of non-excitability of the heart muscle. The state of complete non-excitability of the heart muscle is called absolute refractoriness and takes almost the entire time of systole. At the end of absolute refractoriness by the beginning of diastole, excitability gradually returns to normal - relative refractoriness. At this time, the heart muscle is able to respond to a stronger irritation with an extraordinary contraction - an extrasystole. The ventricular extrasystole is followed by an extended (compensatory) pause. It arises as a result of the fact that the next impulse that comes from the sinus node enters the ventricles during their absolute refractoriness caused by extrasystole and this impulse is not perceived, and the next contraction of the heart falls out. After a compensatory pause, the normal rhythm of heart contractions is restored. If an additional impulse occurs in the sinoatrial node, then an extraordinary cardiac cycle occurs, but without a compensatory pause. The pause in these cases will be even shorter than usual. Due to the presence of a refractory period, the heart muscle is not capable of prolonged titanic contraction, which is tantamount to cardiac arrest.
The contractility of the heart muscle has its own characteristics. The strength of heart contractions depends on the initial length of the muscle fibers (the "law of the heart", which Starling formulated). The more blood flows to the heart, the more its fibers will be stretched and the greater will be the force of heart contractions. This is of great adaptive importance, providing a more complete emptying of the cavities of the heart from blood, which maintains a balance in the amount of blood flowing to the heart and flowing from it.
In the heart muscle, there is a so-called atypical tissue that forms the conduction system of the heart. The first node is located under the epicardium in the wall of the right atrium, near the confluence of the hollow vensinoatrial node. The second node is located under the epicardium of the wall of the right atrium in the region of the atrioventricular septum, which separates the right atrium from the ventricle, and is called the atrioventricular (atrioventricular) node. The bundle of His departs from it, dividing into the right and left legs, which separately go to the corresponding ventricles, where they break up into Purkinje fibers. The conduction system of the heart is directly related to the automation of the heart (Fig. 10).
Rice. 1. Conduction system of the heart:
a - sinoatrial node; b- atrioventricular node;
c- bundle of His; Mr. Purkinje fibers.
The automatism of the heart is the ability to contract rhythmically under the influence of impulses originating in the heart itself without any irritation.
With distance from the sinoatrial node, the ability of the conduction system of the heart to automate decreases (the law of the gradient of diminishing automatism, discovered by Gaskell). Based on this law, the atrioventricular node has a lesser ability to automate (the center of automatism of the second order), and the rest of the conducting system is the center of automatism of the third order. Thus, impulses that cause heart contractions initially originate in the sinoatrial node.
Cardiac activity is manifested by a number of mechanical, sound, electrical and other phenomena, the study of which in clinical practice makes it possible to obtain very important information about the functional state of the myocardium.
A cardiac impulse is a fluctuation of the chest wall as a result of ventricular systole. It is apical, when the heart during systole hits the top of the left ventricle (in small animals), and lateral, when the heart hits the side wall. In farm animals, the cardiac impulse is examined on the left in the region of the 4–5th intercostal space, and at the same time, attention is paid to its frequency, rhythm, strength and location.
Heart sounds are sound phenomena that are formed during the work of the heart. It is believed that five heart sounds can be distinguished, but in clinical practice, listening to two tones is important.
The first tone coincides with the systole of the heart and is called systolic. It is made up of several components. The main one is valvular, arising from fluctuations in the cusps and tendon filaments of atrioventricular valves when they close, fluctuations in the walls of myocardial cavities during systole, fluctuations in the initial segments of the aorta and pulmonary trunk during blood stretching in the phase of its expulsion. By its sound character, this tone is long and low.
The second tone coincides with diastole and is called diastolic. Its occurrence consists of the noise generated when the semilunar valves close, the opening of the leaflets at this time, the fluctuations of the walls of the aorta and pulmonary artery. This tone is short, high, in some animals with a flapping tone.
Arterial pulse is a rhythmic fluctuation of the walls of blood vessels, caused by the contraction of the heart, the ejection of blood into the arterial system, and the change in pressure in it during systole and diastole.
One of the methods that have found wide application in clinical practice in the study of cardiac activity is electrocardiography. When the heart works in its different departments, excited (-) and not excited (+) charged areas appear. As a result of this potential difference, biocurrents arise, which propagate throughout the body and are captured using electrocardiographs. In the ECG, a systolic period is distinguished - from the beginning of one P wave to the end of the T wave, from the end of the T wave to the beginning of the P wave (diastolic period). P, R, T waves are defined as positive, and Q and S as negative. On the ECG, in addition, intervals P-Q, S-T, T-P, R-R, complexes Q-A-S, and Q-R-S-T are recorded (Fig. 2).
Fig.2. Scheme of the electrocardiogram.
Each of these elements reflects the time and sequence of excitation of different parts of the myocardium. The cardiac cycle begins with excitation of the atria, which is reflected on the ECG by the appearance of the P wave. In animals, it is usually bifurcated due to non-simultaneous excitation of the right and left atria. The P-Q interval shows the time from the start of atrial excitation to the start of ventricular excitation, i.e. the time of passage of excitation through the atria and its delay in the atrioventricular node. When the ventricles are excited, the Q-R-S complex is recorded. The duration of the interval from the beginning of Q to the end of the T wave reflects the time of intraventricular conduction. The Q wave occurs when the interventricular septum is excited. The R wave is formed when the ventricles are excited. The S wave indicates that the ventricles are completely covered by excitation. The T wave corresponds to the phase of recovery (repolarization) of the potential of the ventricular myocardium. The Q-T interval (Q-R-S-T complex) shows the time of excitation and recovery of the potential of the ventricular myocardium. The R-R interval determines the time of one cardiac cycle, the duration of which is also characterized by the heart rate. The interpretation of the ECG begins with the analysis of the second lead, the other two are of an auxiliary nature.
The central nervous system, together with a number of humoral factors, provides a regulatory effect on the functioning of the heart. Impulses entering the heart through the fibers of the vagus nerves cause a slowdown in the heart rate (negative chronotropic effect), reduce the force of heart contractions (negative inotropic effect), reduce myocardial excitability (negative bathmotropic effect) and the speed of excitation through the heart (negative dromotropic effect). ).
In contrast to the vagus, sympathetic nerves have been found to produce all four positive effects.
Among the reflex influences on the heart, impulses arising in receptors located in the aortic arch and carotid sinus are important. Baro- and chemoreceptors are located in these zones. The areas of these vascular zones are called reflexogenic zones.
The work of the heart is also under the influence of conditioned reflex impulses coming from the centers of the hypothalamus and other structures of the brain, including its cortex.
Humoral regulation of the work of the heart is carried out with the participation of chemical biologically active substances. Acetylcholine has a short-term inhibitory effect on the work of the heart, and adrenaline has a longer stimulating effect. Corticosteroids, thyroid hormones (thyroxine, triiodothyronine) increase the work of the heart. The heart is sensitive to the ionic composition of the blood. Calcium ions increase the excitability of myocardial cells, but their high saturation can cause cardiac arrest, potassium ions inhibit the functional activity of the heart.
Blood in its movement goes through a complex path, moving through the large and small circles of blood circulation.
The continuity of blood flow is ensured not only by the pumping work of the heart, but by the elastic and contractile ability of the walls of arterial vessels.
The movement of blood through the vessels (hemodynamics), like the movement of any liquid, obeys the law of hydrodynamics, according to which the liquid flows from an area of higher pressure to a lower one. The diameter of the vessels from the aorta gradually decreases, therefore, the resistance of the vessels to blood flow increases. This is further facilitated by the viscosity and increasing friction of blood particles among themselves. Therefore, the movement of blood in different parts of the vascular system is not the same.
Arterial blood pressure (AKP) is the pressure of moving blood against the wall of a blood vessel. The value of the AKD is influenced by the work of the heart, the size of the lumen of the vessels, the amount and viscosity of the blood.
The same factors are involved in the mechanism of regulation of blood pressure as in the regulation of the work of the heart and the lumen of blood vessels. The vagus nerves and acetylcholine lower blood pressure, while the sympathetic nerves and adrenaline increase it. An important role belongs to the reflexogenic vascular zones.
The distribution of blood throughout the body is provided by three mechanisms of regulation: local, humoral and nervous.
Local regulation of blood circulation is carried out in the interests of the function of a particular organ or tissue, and humoral and nervous regulation provide the needs of predominantly large areas or the whole organism. This is observed during intensive muscular work.
Humoral regulation of blood circulation. Carbonic, lactic, phosphoric acids, ATP, potassium ions, histamine and others cause a vasodilatory effect. The same effect is exerted by hormones - glucagon, secretin, mediator - acetylcholine, bradykinin. Catecholamines (adrenaline, norepinephrine), pituitary hormones (oxytocin, vasopressin), renin produced in the kidneys cause a vasoconstrictive effect.
Nervous regulation of blood circulation. Blood vessels have dual innervation. The sympathetic nerves narrow the lumen of the blood vessels (vasoconstrictors), while the parasympathetic nerves widen them (vasodilators).
Control questions: 1. Phases of the cardiac cycle. 2. Properties of the heart muscle. 3. Manifestations of the work of the heart. 4. Regulation of the work of the heart. 5. Factors causing and preventing the movement of blood through the vessels. 6. Blood pressure and its regulation. 7. The mechanism of distribution of blood throughout the body.
Chapter 4
Respiration is a set of processes that result in the delivery and consumption of oxygen by the body and the release of carbon dioxide into the external environment. The breathing process consists of the following stages: 1) air exchange between the external environment and the alveoli of the lungs; 2) the exchange of gases of alveolar air and blood through the pulmonary capillaries; 3) transport of gases by blood; 4) exchange of blood gases and tissues in tissue capillaries; 5) the consumption of oxygen by cells and the release of carbon dioxide by them. The cessation of breathing even for the shortest period of time disrupts the functions of various organs and can lead to death.
Lungs in farm animals are located in a hermetically sealed chest cavity. They are devoid of muscles and passively follow the movement of the chest: when the latter expands, they expand and suck in air (inhale), and when they fall, they subside (exhale). The respiratory muscles of the chest and the diaphragm contract due to impulses coming from the respiratory center, which ensures normal breathing. The chest and diaphragm take part in the change in the volume of the chest cavity.
The participation of the diaphragm in the process of breathing can be traced on the model of the chest cavity by F. Donders (Fig. 3).
Rice. 3. Donders model.
The model is a liter bottle without a bottom, tightened at the bottom with a rubber membrane. There is a stopper through which two glass tubes pass, on one of which a rubber tube with a clamp is put on, and the other is inserted into the trachea of the rabbit's lungs and tied tightly with threads.
The lungs are carefully inserted into the cap. Close the stopper tightly. The walls of the vessel mimic the chest, and the membrane mimics the diaphragm.
If the membrane is pulled down, the volume of the vessel increases, the pressure in it decreases, and air will be sucked into the lungs, i.e. there will be an act of "breathing". If you release the membrane, it will return to its original position, the volume of the vessel will decrease, the pressure inside it will increase, and the air from the lungs will come out. There will be an act of "exhalation".
The act of inhalation and the act of exhalation are taken as one respiratory movement. The number of respiratory movements per minute can be determined by the movement of the chest, by the stream of exhaled air by the movement of the wings of the nose, by auscultation.
The frequency of respiratory movements depends on the level of metabolism in the body, on the ambient temperature, the age of the animals, atmospheric pressure and some other factors.
Highly productive cows have a higher metabolism, so the respiratory rate is 30 per minute, while in average cows it is 15-20. In calves at the age of one year at an air temperature of 15 0 C, the respiratory rate is 20-24, at a temperature of 30-35 0 C 50-60 and at a temperature of 38-40 0 C - 70-75.
Young animals breathe faster than adults. In calves at birth, the respiratory rate reaches 60-65, and by the year it decreases to 20-22.
Physical work, emotional arousal, digestion, change of sleep to wakefulness speed up breathing. Breathing is affected by exercise. In trained horses, breathing is rarer, but deeper.
There are three types of breathing: 1) thoracic, or costal - it mainly takes part in the muscles of the chest (mainly in women); 2) abdominal, or diaphragmatic type of breathing - in it, respiratory movements are performed mainly by the abdominal muscles and the diaphragm (in men) and 3) chest-abdominal, or mixed type of breathing - respiratory movements are carried out by the pectoral and abdominal muscles (in all farm animals).
The type of breathing can change with a disease of the chest or abdominal organs. The animal protects diseased organs.
Auscultation can be direct or with the help of a phonendoscope. During inhalation and at the beginning of exhalation, a soft blowing noise is heard, reminiscent of the sound of the pronunciation of the letter "f". This noise is called vesicular (alveolar) breathing. During exhalation, the alveoli are released from the air and collapse. The resulting sound vibrations form a respiratory noise, which is heard during inhalation and in the initial phase of exhalation.
Auscultation of the chest may reveal physiological breath sounds.
Regulation of hematopoiesis
The regulation of hematopoiesis is not the same at its different stages. Stem cells and early precursor cells of hematopoiesis are controlled by short-range regulation, which is provided by direct interaction with neighboring hematopoietic cells and bone marrow stromal cells. Late progenitor cells are regulated by humoral factors.
The increase and division of stem cells are under the influence of both stromal cells (forming the stroma of the organ), and hematopoietic cells - the closest progeny of the stem cell - and cells of a lymphatic and macrophage nature.
When the bone marrow is irradiated at doses below 5 Gy, an abortive rise in leukocytes, platelets, and reticulocytes is observed in the blood, which postpones the final restoration of the peripheral blood composition to a later date compared to the recovery time after bone marrow irradiation at higher doses. Obviously, the early precursor cells that survived after irradiation create an abortive rise in peripheral blood parameters, temporarily provide hematopoiesis and, by their existence, delay the appearance of hematopoiesis from the stem cell, which replaces the abortive one.
In the regulation of reproduction of early pluripotent and unipotent progenitor cells, their interaction with T-lymphocytes and macrophages is of no small importance. These cells act on progenitor cells with the help of factors produced by them - substances contained in the membrane and separated from it in the form of bubbles upon close contact with target cells.
Regulation of erythropoiesis
Among the regulators of early cells, precursors of the red series, burst promoter activity (BPA) is of particular interest. BPA is already detected in hepatic hematopoiesis in the fetus, but its role is mainly manifested in adult erythropoiesis. The immature colonies have a stimulating effect on BFU-E mainly from bone marrow macrophage elements used in culture at a low concentration, while a high concentration of these cells leads to an obstacle to the reproduction of burst-forming units.
The influence of monocyte-macrophage elements on the cells of the red row is diverse. Thus, macrophages are one of the main extrarenal (located outside the kidneys) sources of erythropoietin. In the fetus, erythropoietin is secreted by the Kupffer cells of the liver. In an adult, the Kupffer cell again begins to produce erythropoietin in the conditions of a regenerating liver.
The red series is characterized by a gradual increase in sensitivity to erythropoietin, the main humoral regulator of erythropoiesis, from early to late precursor cells.
Hypoxia - a decrease in oxygen in tissues - stimulates the production of erythropoietin. Permanent or short-term hypoxia in an experiment on mice with an implanted diffusion chamber led to an increased proliferation of PFU-E immature [ Harigaya et al., 1981]. At the same time, experiments with hypoxia in monkeys in a hypobaric chamber showed a significant increase in their blood HbF-containing erythrocytes.
Hypoxia is a consequence of a decrease in the level of oxygen in the external environment (when climbing to a great height), respiratory failure with damage to the lung tissue, increased oxygen consumption (for example, with thyrotoxicosis).
Increased oxygen demand leading to an increase in erythropoietin levels is observed in various forms of anemia. However, the production of erythropoietin and the response of erythropoiesis to it are ambiguous in different forms of anemia and depend on many factors. For example, a significant increase in erythropoietin in patients with aplastic anemia in the serum and urine of patients may be due not only to the need for it, but also to its reduced consumption. However, the need for oxygen may be reduced. For example, protein starvation leads to a decrease in metabolism and oxygen demand and, in connection with this, to a decrease in the production of erythropoietin and erythropoiesis, which manifests itself primarily in a sharp decrease in reticulocytes in the blood. Another condition with decreased erythropoiesis due to decreased oxygen demand and reduced erythropoietin production is prolonged physical inactivity (eg, bed rest, especially with the head down). This change in erythropoiesis can be observed with erythremia.
Myelopoiesis regulation
The development and widespread use of the method of cultivating bone marrow and blood in agar culture made it possible to study in more detail the regulation of the bipotential colony-forming granulocyte-monocytic progenitor cell (CFU-GM) growing in this culture. For the growth of colonies of this precursor cell in culture and its differentiation, a special colony-stimulating factor - CSF or colony-stimulating activity - CSA is needed. Only leukemic granulocyte-monocytic progenitor cells, in particular murine myeloid leukemia cells, can grow without this factor. CSF is produced in humans by monocyte-macrophage cells in the blood and bone marrow, placental cells, lymphocytes stimulated by certain factors, and endosteal cells.
CSF is a glycoprotein, it is heterogeneous in its composition. This factor consists of two parts: EO-CSF (stimulating the production of eosinophils) and GM-CSF (necessary for the production of neutrophils and monocytes). It depends on the concentration of CSF whether neutrophils or monocytes are produced from one CFU-GM cell under its influence: neutrophils require a high concentration of CSF, for monocytes a sufficiently low concentration.
The production of CSF depends on the stimulating or inhibitory effects of cells, monocyte-macrophage and lymphocytic nature. Monocytic-macrophage elements produce substances that inhibit the activity of CSF. Such inhibitory substances include lactoferrin, contained in the macrophage membrane, and acidic isoferritin. Macrophages synthesize prostaglandins E, which directly inhibit (suppress) CFU-GM.
T-lymphocytes are also heterogeneous in their action on CSF and on CFU-GM. With the depletion of all fractions of T-lymphocytes in the bone marrow and blood, the production of CFU-GM increases. When lymphocytes (but not T-suppressors) are added to such bone marrow, CFU-GM proliferation increases. T-suppressors of the bone marrow suppress the proliferation of CFU-GM.
Thus, the production of CSF, CFU-GM and its offspring is normally regulated by a feedback system: the same cells are both stimulators and inhibitors of their production.
The bulk of progenitor cells (which make up a tiny percentage of the total number of myelokaryocytes) are produced "just in case" and die unused. However, in itself, a gradual increase in sensitivity to poetins allows you to respond with a dosed increase in the production you need at the moment. If the blood loss is small, then some additional erythropoietin is released into the blood, the concentration of which is sufficient only to stimulate CFU-E. In severe anoxia, the release of erythropoietin will be increased, and its concentration will be enough to stimulate already and earlier precursors of erythropoiesis, which will increase the final production of erythrocytes by 1–2 orders of magnitude.
A similar picture is observed in granulopoiesis. The content of neutrophils and monocytes in the blood is mainly regulated by the colony-stimulating factor, a large amount of which leads to an increase in the production of neutrophils, and a small amount leads to monocytosis. The accumulation of monocytes, in turn, contributing to the production of prostaglandins, isoferritin, suppresses the production of colony-stimulating factor, and the level of neutrophils in the blood decreases.
From the book Secrets of the Healers of the East author Victor Fedorovich VostokovAnemia (various types of hematopoietic disorders) 1. Grape juice. Fresh figs. Apples. Juice and berries of black currant. (Separate).2. Treatment with koumiss.3. Hazel kernels, freed from brown husks, together with honey.4. 40 g of garlic insist in a closed
From the book Propaedeutics of childhood diseases author O. V. Osipova37. Stages of hematopoiesis Stem cells are regulated by a random signal. Hematopoiesis is carried out by changing clones formed in utero. Individual cells of the stroma produce growth factors. The intensity of cell formation depends on
From the book Propaedeutics of childhood diseases: lecture notes author O. V. Osipova2. Features of hematopoiesis in children Features of embryonic hematopoiesis: 1) early onset; 2) a sequence of changes in tissues and organs that are the basis for the formation of blood elements, such as the yolk sac, liver, spleen, thymus, lymph nodes,
From the book Histology author Tatyana Dmitrievna Selezneva3. Semiotics of damage to the blood system and hematopoietic organs Syndrome of anemia. Anemia is understood as a decrease in the amount of hemoglobin (less than 110 g / l) or the number of red blood cells (less than 4 x 1012 g / l). Depending on the degree of decrease in hemoglobin, the lungs are distinguished (hemoglobin 90-110 g / l),
From the book Histology author V. Yu. BarsukovTopic 30
From the book Book to help author Natalia Ledneva56. Organs of hematopoiesis Thymus The thymus is the central organ of lymphocytopoiesis and immunogenesis. From the bone marrow precursors of T-lymphocytes, antigen-independent differentiation occurs in it into T-lymphocytes, the varieties of which carry out
From the book Analyzes. Complete reference author Mikhail Borisovich IngerleibAdditional restrictions during aplasia of hematopoiesis Sterility! All food must be sterile (for example, canned food for infants) or treated with high temperature or in the microwave immediately before eating. Products packed at the factory with an expiration date
From the book Natural Cleansing of Vessels and Blood according to Malakhov author Alexander KorodetskyHormonal regulation of hematopoiesis Erythropoietin Erythropoietin is the most important regulator of hematopoiesis, a hormone that causes an increase in the production of red blood cells (erythropoiesis). In an adult, it is formed mainly in the kidneys, and in the embryonic period, almost
From the book Healing Ginger authorMedicinal dishes to improve blood formation, vitamin recipes Oatmeal soup with prunes Take 1.5 cups of oatmeal, 2 liters of water, 3 tbsp. tablespoons of butter, prunes, salt. Rinse the grits, pour hot water over it and boil, removing the foam. When the cereal softens, and
From the book Treatment of more than 100 diseases using Oriental medicine author Savely Kashnitsky From the book The Complete Guide to Nursing author Elena Yurievna KhramovaDISEASES OF THE HEATING SYSTEM
From the book Most Popular Medicines author Mikhail Borisovich IngerleibRehabilitation of patients with impaired hematopoietic processes Blood plays a vital role in the human body: it supplies all human organs and systems with water, oxygen and nutrients, removes unnecessary metabolites (metabolic products) from the body
From the book A Complete Guide to Analyzes and Research in Medicine author Mikhail Borisovich Ingerleib From the book Medical Nutrition. Medical treatment. 100% body protection author Sergey Pavlovich KashinHormonal regulation of hematopoiesis ErythropoietinErythropoietin is the most important regulator of hematopoiesis, a hormone that causes an increase in the production of red blood cells (erythropoiesis). In an adult, it is formed mainly in the kidneys, and in the embryonic period, almost
From the book Ginger. A treasure trove of health and longevity author Nikolai Illarionovich DanikovDiseases of the hematopoietic organs Beekeeping products have a pronounced effect on the processes of hematopoiesis. So, for example, bee venom increases the amount of hemoglobin in the blood, lowers cholesterol, increases the permeability of the walls of blood vessels,
From the author's bookDiseases of the cardiovascular system and hematopoietic organs The vascular system is a powerful branched tree that has roots, trunk, branches, and leaves. Every cell in our body owes its life to a blood vessel - a capillary. Take everything from the body
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