Age-related features of blood composition. Age physiology

Introduction

The idea of blood as a system was created by G.F. Lang in 1939. This system included four components: a) peripheral blood circulating through the vessels, b) hematopoietic organs, c) hematopoietic organs, d) the regulatory neurohumoral apparatus.

Blood is one of the most important life support systems of the body, which has a number of features. The high mitotic activity of hematopoietic tissue causes its increased sensitivity to the action of damaging factors, and the genetic determination of the reproduction, differentiation, structure and metabolism of blood cells creates the preconditions for both genomic disorders and changes in genetic regulation.

The uniqueness of the blood system lies in the fact that pathological changes in it arise as a result of dysfunction not only of its individual components, but also of other organs and systems of the body as a whole. Any disease, pathological process, as well as a number of physiological changes can, to one degree or another, affect the quantitative and qualitative characteristics of the composition of circulating blood. This determines the enormous importance of the need to study blood (as the “blood mirror of the body”) and reveal the patterns of its changes in various diseases.

Purpose of the study: to consider and study the morphology of the blood system and its age-related features.

To achieve this goal, the following tasks were solved:

.Consider the components of the blood system and their morphology.

.Determine age-related characteristics of the blood system.

1. Morphology of the blood system

1.1 Peripheral blood and its elements

Peripheral blood is blood circulating through vessels outside the hematopoietic organs. In a healthy adult, blood accounts for an average of 7% of body weight

Depending on the vessels in which blood flows, its types are distinguished: arterial, venous, capillary. There are differences between these types of blood in biochemical and morphological parameters, but they are insignificant. For example, the concentration of hydrogen ions (medium pH) in arterial blood is 7.35 - 7.47; venous - 7.33 - 7.45. This value is of great physiological importance, as it determines the rate of many physiological and chemical processes in the body.

The absolute majority of circulating blood cells are erythrocytes - red, anucleate cells. Their number in men is 4.710 + - 0.017 x 10.12 / l, in women - 4.170 + - 0.017 x 10.12 / l. In a healthy person, 85% of red blood cells have a discoid shape with biconvex walls, and 15% have other shapes. The diameter of the erythrocyte is 7-8 microns, thickness is 1-2.4 microns. The cell membrane of an erythrocyte is 20 nm thick. Its outer surface consists of lipids, oligosaccharides, which determine the antigenic composition of the cell - blood group, sialic acid and protein, and the inner surface - of glycotic enzymes, sodium, potassium, ATP, glycoprotein and hemoglobin. The cavity of the erythrocyte is filled with granules (4.5 nm) containing hemoglobin.

The red blood cell is a highly specialized cell whose main task is to transport oxygen from the pulmonary alveoli to tissues and carbon dioxide (CO 2) - back from the tissues to the pulmonary alveoli. The biconcave shape of the cell allows for the largest surface area for gas exchange. The diameter of an erythrocyte is about 8 microns, however, the features of the cell skeleton and membrane structure allow it to undergo significant deformation and pass through capillaries with a lumen of 2-3 microns. This ability to deform is provided by the interaction between membrane proteins (segment 3 and glycophorin) and cytoplasm (spectrin, ankyrin and protein 4.1). Defects in these proteins lead to morphological and functional disorders of red blood cells. A mature erythrocyte does not have cytoplasmic organelles and a nucleus and therefore is not capable of synthesizing proteins and lipids, oxidative phosphorylation and maintaining reactions of the tricarboxylic acid cycle. It obtains most of its energy through the Embden-Meyerhof anaerobic pathway and stores it as ATP.

Approximately 98% of the mass of proteins in the cytoplasm of an erythrocyte is hemoglobin (Hb), the molecule of which binds and transports oxygen. The process of binding and releasing oxygen by hemoglobin molecules depends on the pressure of oxygen, carbon dioxide, pH and temperature of the environment.

The lifespan of red blood cells corresponds to 120+-12 days, which was determined using a radioactive label. Red blood cells are distinguished between young (neocytes), mature and old. Neocytes are the most resistant to influence, which is especially evident when they are frozen with various cryoprotectants and thawed. The gradual aging of a cell leads to disruption of metabolic processes and its death. About 200 billion red blood cells die in the human body every day. Their remains are absorbed by macrophages of the spleen and liver.

The next largest number of cells in the blood are platelets - blood platelets. Their number in the blood of a healthy person is 150,000 - 400,000/μl. Platelets, the smallest blood cells, are formed from the largest bone marrow cells - megakaryocytes. Platelets in circulating blood have a round or oval shape, with a diameter of 2.5 microns. There is no nucleus in the cell. The structure of blood platelets is divided into a single-layer membrane, a peripheral structureless zone (hyalomere) and a central granular zone (granulomere). Dense microtubules are detected in the hyalomere by electron microscopy. They play the role of the cell skeleton, as well as participation in the process of clot retraction. The granulomere contains mitochondria, ribosomes, alpha granules, dense bodies, and glycogen particles. Alpha granules contain acid phosphatase, B-glucuronidase, and cathepsin, which makes it possible to classify them as lysosomes that determine cell function. Dense bodies contain serotonin, which contracts blood vessels during release, ATP and ADP, which are involved in adhesion and the release reaction.

Normal platelets are distinguished: young (4.2+-0.13%), mature (88.2+-0.19%), old (4.1+-0.21%) and forms of irritation (2.5 +-0.1%) degenerative and vacuolated.

humoral (plasma) system, consisting of procoagulant proteins;

cellular system consisting of platelets.

The end result of activation of the humoral coagulation system is the formation of a fibrin clot, or red thrombus, while the platelet reaction, accompanied by cell adhesion and aggregation, results in the formation of a platelet plug, or white thrombus. Although these two coagulation systems are usually considered separately, it should be understood that in fact their functions are closely intertwined. Soluble coagulation factors (eg, fibrinogen and von Willebrand factor) are essential for normal platelet function, and, conversely, platelets are important suppliers of procoagulant proteins and an essential catalyst for a number of reactions in the soluble coagulation system.

In general, the hemostatic functions of platelets explain their ability to adhesion, aggregation, formation of a primary platelet clot at the site of damage to the wall of a blood vessel and the release of coagulation factors involved in fibrin loss and retraction of the resulting clot.

In addition to their main function, blood platelets carry a number of vasoactive substances - serotonin, histamine and catecholamines, and maintain the function of the vascular endothelium. Platelets, having phagocytic activity, are able to absorb fat droplets, viruses, bacteria, and immune complexes. Blood plates are involved in inflammatory processes and immunological reactions. They contain both specific antigens, characteristic only of platelets (HPA: 1-5), and antigens of the ABO, MN, P systems, the major histocompatibility complex HLA, but there are no antigens of the Rh, Daffy, Kell, Kidd systems. The most immunogenic antigens are the A and B loci and the least are the C locus of the HLA system.

The average lifespan of a platelet is 9.5+-0.6 days. Normally, 2/3 of a person’s blood platelets are in the circulating blood and 1/3 in the spleen and are a kind of reserve for rapid mobilization if necessary. There is a dynamic exchange between these parts.

The total number of platelets in the human body ranges from 1.0 to 1.5 trillion; they are renewed per day (1.1 - 1.73) x10.11. The process of the terminal stage of thrombocytopoiesis has not been sufficiently studied. It is possible that in response to a certain signal, megakaryocytes are transformed into spider-like cells, from which many long filamentous processes (proplatelets) extend with uniform foci of constriction. The proplatelets enter the medullary sinusoids and there fragment into platelets, possibly due to the shear force of the blood flow. Although end-stage thrombocytopoiesis is limited to only the most mature megakaryocytes, it is a regulated process. After a sharp increase in the peripheral demand for platelets, an increase in the volume of these cells is immediately detected, which reflects changes in the mechanism of platelet formation.

White blood cells, or leukocytes, are the basis of the body's antimicrobial defense. This heterogeneous group of “defenses” includes the main effectors of immune and inflammatory responses.

The term "leukocyte" refers more to the appearance of the cell (leukos - white Greek) observed in a blood sample after centrifugation.

Neutrophils.

Neutrophil granulocytes are the most large group circulating leukocytes. The term "neutrophil" describes the appearance of cytoplasmic granules on Wright-Giemsa stain. Together with eosinophils and basophils, neutrophils belong to the class of granulocytes. Due to the presence of a characteristic multilobar (segmented) nucleus, the neutrophil is also called a polymorphonuclear leukocyte (PMNL). Granulocytes have sizes of 9-15 microns, exceeding those of erythrocytes. In the protoplasm of all granulocytes, granularity is detected: aerophilic and special. Aerophilic granules contain mainly acid phosphatase, while special granules contain alkaline phosphatase. The main function of granulocytes is phagocytosis.

The phagocytic activity of neutrophils is most pronounced in young people; as people get older, it decreases. In addition to phagocytosis, granulocytes exhibit secretory activity during inflammation, releasing a number of antibacterial agents: peroxidases, bactericidal lysosomal cationic proteins and other substances. These highly specialized cells migrate to sites of infection where they recognize, capture and destroy bacteria. This function is possible due to the ability of neutrophils to chemotaxis, adhesion, movement and phagocytosis. They have a metabolic apparatus for producing toxic substances and enzymes that destroy microorganisms.

Granulocytes live 1-6 days, on average 6-9 days, while their residence time in the bone marrow is 2-6 days. They circulate with the blood for 60-90 minutes. up to 24 hours, sometimes up to 2 days. A small part of granulocytes is destroyed in the blood, the majority enters the tissues and ends its physiological existence. Granulocytes are destroyed by macrophages of the lungs, spleen, and liver. Some of the granulocytes are excreted from the body with secretions and excreta, sputum, saliva, bile, urine, and feces.

Eosinophils.

Eosinophils have a bilobed nucleus and a cytoplasm filled with clearly visible granules that turn red after Wright-Giemsa staining. The basic (positively charged) proteins of these granules stain red due to their high affinity for eosin. Although eosinophils undergo the same stages of maturation as neutrophils, due to their small number, eosinophil precursors in the bone marrow are detected less frequently (with the exception of some pathological conditions: worms, allergies).

Basophils.

Basophils are the smallest group of circulating granulocytes, making up less than 1% of leukocytes. Large cytoplasmic granules of basophils contain sulfated or carboxylated acidic proteins, such as heparin, which acquire Blue colour with Wright-Giemsa staining. Basophils mediate allergic reactions, especially those based on IgE-dependent mechanisms. They express IgE receptors and, when stimulated appropriately, release histamine in response to IgE and antigen.

Monocytes.

Monocytes circulate in the peripheral blood as large cells with blue/gray cytoplasm and a kidney-shaped or folded nucleus containing delicate reticulate chromatin. Monocytes are a derivative of COE-GM (common precursor for granulocytes and monocytes) and COE-M (precursor of monocytic lineage only). Monocytes spend only about 20 hours in the bloodstream and then enter peripheral tissues, where they transform into macrophages of the reticuloendothelial system (RES). These tissue macrophages, or histiocytes, are large cells with an eccentrically located nucleus and vacuolated cytoplasm containing numerous inclusions.

Monocytes and macrophages are long-lived cells whose functional characteristics are in many ways similar to those of granulocytes. They more effectively capture and absorb microbacteria, fungi and macromolecules; their role in the phagocytosis of pyogenic bacteria is less significant. In the spleen, macrophages are responsible for the disposal of sensitized and senescent red blood cells. Macrophages play an important role in processing and presenting antigens to lymphocytes during cellular and humoral immune responses. Their production of cytokines and interleukins, interferons and complement components contributes to coordination in the integrated immune response.

Normally, monocytes make up 1 to 10% of circulating leukocytes. When the number of monocytes exceeds 100/μl, we can talk about monocytosis, which is observed in patients with chronic infections (tuberculosis, chronic endocarditis) or inflammatory processes (autoimmune diseases, inflammatory bowel diseases).

Lymphocytes.

A significant population of leukocytes consists of lymphocytes. Based on their structure, they are conventionally divided into small (5-9 microns), medium (10 microns) and large (11-13 microns). The lymphocyte is currently considered as the main cell immune system. These are small mononuclear cells that coordinate and execute the immune response by producing inflammatory cytokines and antigen-specific binding receptors.

Lymphocytes are divided into two main categories: B cells and T cells - and several smaller classes, such as natural killer cells. Subsets of lymphocytes differ in the site of their formation and the effector molecules they express, but share a common feature - the ability to mediate a highly specific antigenic response. Lymphocytes are able to move and penetrate other cellular elements. A small part of lymphocytes have phagocytic activity. The main function of a lymphocyte is to participate in immune reactions. For example, T-lymphocytes are active participants in the rejection reaction, the graft-versus-host reaction; B-lymphocytes produce antibodies that determine the humoral immune response.

Lymphocytes can retain immunological memory for a long time. Under the influence of a number of immune and chemical (mutogens) factors they are able to proliferate.

The generation of lymphocytes in an adult occurs mainly in the bone marrow and thymus gland.

The lifespan of lymphocytes is different: for short-lived ones (obviously, those that participate in immune reactions) - 3-4 days, for long-lived ones - 100-200 days and even 580 days. Their presence in the circulating blood does not exceed 40 minutes. The total number in the circulating blood of an adult is 7.5x10.9 lymphocytes, and in the body, taking into account the reserve of these cells in the bone marrow, spleen, lymph nodes, thymus, tonsils and Peyer's patches - 6.0x10.12.

Old lymphocytes die in the circulating blood and are eliminated by the reticulo-macrophage elements of the capillaries.

B lymphocytes .

B lymphocytes express unique antigen receptors - immunoglobulins - and are programmed to produce them in large quantities in response to antigenic stimulation. B cells are formed from stem cells in the bone marrow. The term B cell comes from the Latin name for the bursa Fabricius, an organ necessary for the maturation of B cells in birds. Humans do not have a similar organ; B cell maturation occurs primarily in the bone marrow.

The immune system contains a large population of individual clones of B lymphocytes. Each clone expresses a unique antigen receptor that is essentially identical to the immunoglobulin molecule it produces. These molecules are different from each other and bind only to a limited number of antigens.

Mature B lymphocytes with characteristic surface antigens CD19 and CD20 are located mainly in the germinal centers of the lymph node cortex and in the white pulp of the spleen. B cells make up less than 20% of circulating lymphocytes.

T lymphocytes.

Having formed from bone marrow stem cells, T cells necessarily undergo a developmental stage in the thymus (thymus gland), resulting in the generation of mature, functional T cells.

According to the unitary theory, all blood cells come from one pluripotent undifferentiated (stem) cell. It has no morphological differences from a small lymphocyte.

Speaking from the formed elements of blood, it should be noted that after maturation in the bone marrow, they do not immediately enter the vascular bed. For some time, blood cells remain in special depots in the bone marrow and spleen. This reserve of additional blood is one of the factors regulating the constant composition of the blood. Once in the circulating flow, each blood cell functions for a certain time, gradually ages and is eliminated from the vascular bed. To replace old and eliminated cells, young formed elements come from hematopoietic tissue into the circulating blood during the process of physiological regeneration. This process is the main mechanism for maintaining a constant blood composition and an essential factor in ensuring homeostasis in the body.

Most of the blood is plasma. It has a complex multicomponent composition. The basis of plasma is water (90%), in which various proteins (7-8%) are dissolved, other organic compounds - glucose, enzymes, vitamins, acids, lipids (1.1%) and minerals (0.9%).

Protein components of plasma, together with platelets, provide the hemostatic function of the blood, participate in plastic processes in the tissues of the body, determine humoral immunity, detoxification and transport functions of the blood. In plasma, the concentration of total protein (normally 70-80 g/l), albumin (40-45%) and globulins (55-60%) is determined by electrophoretic method. Albumin is formed in the liver and is a low molecular weight (mw 69,000) protein. One third of its total amount (200-300 g) in the body of an adult is in the circulating blood, and two thirds are outside the vascular bed. There is a continuous exchange of albumin between these pools. It performs several functions: it maintains colloid-osmotic pressure in the blood and tissues (it accounts for 80% of the value of this indicator), on which transcapillary fluid exchange, tissue turgor and the volume of fluid in the extravascular and vascular spaces depend. Easily combines with organic and inorganic substances, hormones, medicines, albumin delivers them through the bloodstream to the tissues and at the same time removes some metabolic products into the vascular bed to the liver, kidneys, lungs, and gastrointestinal tract, promoting detoxification of the body. It is one of the important components of the plasma buffer system, regulating the acid-base state of the blood. Participates in tissue nutrition as an easily digestible protein.

The next group of proteins consists of globulins, which have a high (105.00-900.000) molecular weight. They account for 15-18% of the value of maintaining colloid-osmotic blood pressure. Their main function is to provide humoral immunity.

When using the immunological method, plasma proteins are divided into 3 classes - A, M, G. Antibodies against the vast majority of infectious agents are contained in class G.

Among hemostatic plasma proteins, the most prominent place is given to factors VIII and IX of the blood coagulation system, which are currently obtained in pure form.

Plasma contains several humoral systems: complementary (complement components are involved in the binding of antigens to antibodies), coagulation and anti-inflammatory systems, oxidative and antioxidant systems, kallekrein, properdin, nonspecific protective factors, humoral immunity factors and others. Plasma contains various protein complexes (glycoproteins, metalloproteins, lipoproteins, etc.), hormones, and other biologically active substances, which makes it possible to obtain valuable therapeutic drugs from it.

The physiological role of a number of plasma ingredients has not yet been sufficiently studied and requires further research.

blood platelet immunity age

1.2 Organs of hematopoiesis and blood destruction

A common feature of the histological structure of the hematopoietic organs is the presence in their composition of parenchyma of reticular (in the case of the thymus - reticuloepithelial) connective tissue, which performs a number of special functions: 1) trophism of the hematopoietic tissue itself, 2) delimitation of groups of maturing formed elements belonging to different lines of differentiation, 3 ) are “chemical beacons” for reducing blood cells (lymphocytes, etc.).

The hematopoietic organs include the red bone marrow, lymph nodes, spleen, thymus, and the hematopoietic organs include the liver, bone marrow, and spleen.

Red bone marrow

structural features: honeycomb-like structure (due to the abundance of fat cells)

functions: hematopoietic (all types and germs of hematopoiesis), immune (the place of formation of the precursors of B- and T-lymphocytes, differentiation and maturation of T-lymphocytes occurs in the thymus). The destruction of cells (erythrocytes), recycling of iron, and synthesis of Hb also occur in it.

Spleen.

localization: in the left hypochondrium, along the blood vessels

structural features: largest peripheral hematopoietic organ; covered with peritoneum and a capsule of connective tissue with a high content of smooth myocytes (give the organ the ability to contract); trabeculae extend from the capsule deep into the organ, anastomosing with each other; in the parenchyma, white and red pulp are distinguished: the first is represented by many lymphoid follicles (nodules), the second - by blood vessels, reticular tissue and the splenic cords lying in the nodes of the latter - special cellular associates, which include erythrocytes, platelets, leukocytes, macrophages, plasma cells and etc.; it is believed that it is in the splenic cords that the destruction of old blood cells occurs, primarily erythrocytes and blood platelets;

functions: hematopoietic (formation of B-lymphocytes), protective (phagocytosis, participation in immune reactions), storage (operational blood depot, accumulation of platelets), destruction of old and damaged red blood cells, leukocytes, platelets.

Thymus (thymus gland)

localization: behind the sternum

age dynamics: the greatest development is achieved in childhood; after puberty undergoes gradual involution; by old age, it is almost completely replaced by adipose tissue (since a significant part of T-lymphocytes is represented by long-lived cells capable of selective proliferation when encountering an antigen, age-related atrophy of the thymus does not lead to a catastrophic decrease in immunity)

structural features: covered with a connective tissue capsule, septa extending from it divide the organ into lobules; in each lobule the cortex and medulla are distinguished; the parenchyma of the lobules is formed by the precursors of T-lymphocytes (migrated to the thymus from the red bone marrow), T-lymphocytes at various stages of differentiation and reticuloepithelial tissue; layered thymic corpuscles are located in the medulla, presumably performing an endocrine function

functions: a) hematopoietic (the place of formation of the first lymphocytes in the embryo), b) immune, c) endocrine (secretes a number of hormones and hormone-like substances that stimulate the reproduction and differentiation of T lymphocytes and regulate certain parts of the immune response).

Lymph node

localization: along the lymphatic vessels

structural features: the organ is bean-shaped, on the convex side several afferent lymphatic vessels approach the lymph node, on the opposite side there is a gate through which the efferent lymphatic vessel and veins exit and the artery and nerves enter; covered with a connective tissue capsule, from which trabeculae extend deep into the organ; in the parenchyma, the cortex and medulla are distinguished, the first is formed by spherical lymphoid follicles (nodules, which are dense accumulations of lymphocytes), the second by pulpal cords - branching and anastomosing cords consisting of many lymphocytes; tissue composition of the parenchyma: hematopoietic tissue (B-lymphocytes, plasma cells, macrophages, etc.) and reticular tissue; the spaces through which lymph moves within the node are called sinuses

functions: hematopoietic (formation of B-lymphocytes), protective (filtration of lymph, phagocytosis, participation in the immune response - in the lymph nodes B-lymphocytes are converted into plasma cells - antibody producers)

Amygdala.

localization: depending on the topography, the pharyngeal, laryngeal, tubal, lingual and palatine tonsils are distinguished

structural features: the tonsil belongs to the so-called lymphoepithelial organs and is an accumulation of lymphoid follicles (nodules) around a finger-like (or slit-like) ingrowth of the epithelium into the underlying connective tissue; has its own capsule

functions: hematopoietic (formation of lymphocytes), protective (phagocytosis, local immunity)

1.3 Neurohumoral regulation

Neurohumoral regulation is a form of regulation of physiological processes in the body, carried out by the central nervous system and biologically active substances of body fluids (blood, lymph and tissue fluid). Plays a leading role in maintaining homeostasis, i.e. the constancy of the internal environment of the body, and the adaptation of the body to changing conditions of existence.

Neurohumoral regulation arose in the process of animal evolution as a result of the combination of two forms of regulation of the body’s vital activity - the more ancient humoral (with its help, communication was carried out between individual cells or organs due to substances released from them in the process of metabolism) and nervous (which took control of activity of the humoral regulatory system). In the processes of N. r. in addition to direct transmitters of nervous excitation, i.e. mediators, tissue hormones, hypothalamic neurohormones, regulatory peptides and other biologically active substances take part. They are distributed throughout the body through the bloodstream, but only affect the resulting organs (target organs), interacting with the receptor (target cell). Under their influence, the adreno-, cholinergic, histamine- and serotonin-reactive structures of the body are excited. In particular, the neurosecretory cells of the hypothalamus are the site of transformation of nervous stimuli into humoral ones, and humoral ones into nervous ones. Under certain conditions, biologically active substances form a link in the reflex arc, i.e. transmit information to the central nervous system, where it is processed and then returned in the form of a stream of nerve impulses to the executive organs (effectors).

The presence of histohematic barriers determines the selective penetration of hormones, mediators and other biologically active substances from the blood only into strictly defined areas of the brain. However, if the permeability of the barrier is disrupted, biologically active substances can penetrate into those parts of the brain that are usually closed to these substances, which can lead to the development of unusual conditions, even pathological ones, affecting both peripheral and central parts nervous system. Violations of the mechanisms of N. r. can also lead to a mismatch of certain parameters of the internal environment of the body and, as a consequence, to the development of various pathological conditions.

2. Age characteristics blood systems

At the end of the 19th century, the outstanding French physiologist Claude Bernard formulated the position of the constancy of the internal environment of the body (homeostasis) as a necessary condition for maintaining the vital functions of the body. This property was improved in the process of evolution, when the mechanisms that supported it were formed, and warm-blooded animals in evolution represented the highest level of development of this function.

During ontogenesis in each age period, blood has its own characteristics. They are determined by the level of development of the morphological and functional structures of the organs of the blood system, as well as neurohumoral mechanisms for regulating their activity.

2.1 General properties blood in ontogenesis

The total amount of blood in relation to the body weight of a newborn is 15%, in children of one year - 11%, and in adults - 7-8%. At the same time, boys have slightly more blood than girls. However, at rest, only 40-45% of the blood circulates in the vascular bed, the rest is in the depot: the capillaries of the liver, spleen and subcutaneous tissue - and is included in the bloodstream when body temperature rises, muscle work, blood loss, etc.

Specific gravity blood of newborns is slightly higher than that of older children, and is respectively 1.06-1.08. The blood density established in the first months (1.052-1.063) remains until the end of life.

Blood viscosity in newborns is 2 times higher than in adults and is 10.0-14.8 arb. units By the end of the first month, this value decreases and usually reaches average figures - 4.6 conventional units. units (relative to water). Blood viscosity values in elderly people do not exceed normal limits (4.5).

2.2 Biochemical properties of blood

In humans chemical composition blood is characterized by significant constancy. The greatest deviations, if we take the content of substances in the blood of adults as the norm, can be noted during the neonatal period and in old age.

The total protein content in the blood serum of healthy newborns is 5.68+-0.04 g%. With age, this amount increases, growing especially rapidly in the first three years. At 3-4 years, these values practically reach the level of adults (6.83+-0.19 g). Attention should be paid to the wider range of individual fluctuations in protein levels in young children (from 4.3 to 8.3 g%) compared to adults, in whom these values were 6.2-8.2 g%. The lower level of protein in the blood plasma in children in the first months of life is explained by the insufficient function of the body's protein-forming systems.

During ontogenesis, the ratio between albumins and various fractions of globulins in the blood plasma also changes. In the first months of life, the content of albumin in the blood is reduced (3.7 g); by 6 years this value increases to 4.1 g%, and by 3 years it was 4.5 g%, which is close to the norm for an adult. The amount of gamma globulins, high in the first days after birth due to maternal plasma, gradually decreases, and then by 3 years it reaches the adult norm (17.39 g). The content of alpha1-globulins in children under 1 year of age is increased; by 3 years of age their level in the blood is normalized. The determination of the concentration of alpha2-globulins proceeds somewhat differently. In the first six months their level is elevated, by the age of 7 it gradually decreases, and then reaches the level characteristic of adults. The content of beta globulins also reaches adult levels after 7 years.

Thus, the protein composition of the blood undergoes a number of changes during ontogenesis: from birth to adulthood, the protein content in the blood increases, and certain ratios in protein fractions are established. The functional capabilities of the organs that synthesize plasma proteins, primarily the liver, are relatively low at the time of birth and gradually increase, which leads to normalization of blood composition.

Picture 1

The amount of cholesterol (Fig. 1) in the blood of newborns is relatively low and increases with age. It is noted that when carbohydrates predominate in food, the level of cholesterol in the blood increases, and when proteins predominate, it decreases. In old age and old age, cholesterol levels increase.

The level of lactic acid in an infant can be 30% higher than that in adults, which is associated with an increase in the level of glycolysis in children. With age, the content of lactic acid in a child's blood gradually decreases. Thus, the level of lactic acid in a child in the first 3 months of life is 18.7 mg%, by the end of 1 year - 13.8 mg%, and in adults - 10.2 mg%.

2.3 Formed elements of blood in ontogenesis

Erythropoiesis. The number of red blood cells in the fetus gradually increases, and there is a decrease in their diameter, volume and number of nucleated cells. In newborns, the intensity of erythropoiesis is approximately 5 times higher than in adults. The number of red blood cells in them on the 1st day is increased compared to adults and reaches 6-10 x1012 /l. On the 2-3rd day their quantity decreases as a result of their destruction (physiological jaundice) and during the 1st month their content decreases to 4.7x1012 / l. In this case, anisocytosis, poikilocytosis and polychromatophilia are detected, and sometimes nucleated red blood cells are also found. During the first half of the year, infants are characterized by a further decrease in the number of red blood cells, after which their number increases to 4.2x1012 /l. Starting from the age of 4, there is a decrease in myeloid tissue and during puberty, hematopoiesis remains in the red bone marrow of the spongy substance of the vertebral bodies, ribs, sternum, leg bones and femurs. With aging, there is a decrease in the total mass of red bone marrow and its proliferative activity. There is a tendency towards a decrease in the number of red blood cells and hemoglobin.

Hemoglobin. The function of oxygen carrier in the embryo up to 9-12 weeks is performed by embryonic (primitive) hemoglobin (HbP), which is replaced by fetal hemoglobin (HbF) by the 3rd month of intrauterine development. At the 4th month, adult hemoglobin (HbA) appears in the fetal blood and its amount does not exceed 10% until 8 months. Newborns still retain up to 70% HbF and already contain 30% HbA. The amount of Hb is increased (170 - 246 g/l), but, starting from the 1st day, its content gradually decreases. In elderly and senile people, the Hb content decreases slightly and fluctuates within the lower limit of the norm for mature age. ESR in newborns is lower than in adults and is 1-2 mm/h.

Leukocytes. In newborns, immediately after birth, the number of leukocytes is increased and reaches 15 x 1012/l (leukocytosis of newborns). After 6 hours, their number increases to 20 x1012/l, after 24 hours - 28 x1012/l, 48 hours - 19 x1012/l. The regeneration index is increased and a shift in the leukocyte formula to the left is noted. The highest increase in the number of leukocytes is observed on the 2nd day. Then their number decreases and the maximum drop in the curve occurs on the 5th day, and by the 7th day their number approaches the upper limit of the adult norm. In infants, there is a relatively low motor and phagocytic activity of leukocytes. The picture of white blood in children after the 1st year of life is characterized by a gradual decrease in the absolute number of leukocytes, an increase in the relative number of neutrophils with a corresponding decrease in the number of lymphocytes. In the leukocyte formula, 2 “crossovers” of changes in leukocytes are noted. The first - at the age of 3 - 7 days (decrease in the percentage of neutrophils and increase in the percentage of lymphocytes) and the second - at the age of 4-6 years (increase in the percentage of neutrophils and decrease in the percentage of lymphocytes). With old age, leukopenia (leukopenia of old age) and eosinopenia are noted. The functional reserve of leukopoiesis decreases under extreme conditions.

Platelets. The number of platelets in newborns in the first hours after birth ranges from 150 to 320 x 109 /l, which on average does not differ significantly from their content in the blood of adults. This is followed by a slight decrease in their quantity (up to 164-178x109 / l) by 7-9 days, after which by the end of the 2nd week their content increases and remains practically without significant changes at the level of adults. Children 1 day of life are characterized by a large number of round and young forms of platelets, the number of which decreases with age.

Hemostasis. There is no fibrinogen, prothrombin and accelerin in the blood of the fetus up to 16 - 20 weeks, and therefore it does not clot. Fibrinogen appears at 4-5 months of intrauterine life, its concentration is 0.6 g/l. During this period, the activity of the fibrin-stabilizing factor is still low, but the activity of heparin is high (almost 2 times higher than in adults). The low level of factors of the coagulation and anticoagulation systems of the blood in the fetus is explained by the immaturity of the cellular structures of the liver that carry out their biosynthesis. In the blood of newborns, there is a low concentration of a number of factors (FII, FVII, FIX, FX, FXI, FXIII) of the blood coagulation system, anticoagulants and plasminogen, although the ratio of their concentrations is the same as in adults. In children in the first days of life, blood clotting time is reduced, especially on the 2nd day, after which it gradually increases and reaches the blood clotting rate in adults by the end of adolescence. During childhood, there is a gradual increase in the content of procoagulants and anticoagulants. In this case, heterochronic maturation of individual links (pro- and anticoagulants) in a given postnatal period is characteristic. By the age of 14-16 years, the content and activity of all factors involved in blood coagulation and fibrinolysis reach adult levels.

Blood groups. The formation of factors that determine group membership in ontogeny does not occur simultaneously. Agglutinogens A and B are formed by 2 - 3 months of the antenatal period, and agglutinins alpha and beta - at the time of or after birth, which determines the low ability of erythrocytes to agglutinate, which reaches its level in adults by 10 - 20 years.

Agglutinogens of the Rh system appear in the fetus at 2 - 3 months, while the activity of the Rh antigen in the prenatal period is higher than in adults.

2.4 Leucoformula

The number of leukocytes in a child in the first days of life is greater than in adults, and on average ranges from 10,000-20,000 per cubic meter. mm. Then the white blood cell count begins to fall. As with erythrocytes, there is a wide range of fluctuations in the number of leukocytes in the first days of postnatal life from 4600 to 28000. The following is characteristic of the picture of leukocytes in children of this period. An increase in the number of leukocytes during 3 hours of life (up to 19,600), which is apparently associated with the resorption of decay products of the child’s tissues, tissue hemorrhages possible during childbirth, after 6 hours - 20,000, after 24 - 28,000, after 48 - 19,000 By day 7, the number of leukocytes approaches the upper limit of adults and is 8000-11000. In children 10-12 years old, the number of leukocytes in the peripheral blood ranges from 6-8 thousand, i.e. corresponds to the number of leukocytes in adults.

The leukocyte formula also has its own age-related characteristics. Let us remember that this means the ratio of different forms of leukocytes as a percentage.

Figure 2

The leukocyte formula of a child’s blood during the neonatal period is characterized by:

) a consistent increase in the number of lymphocytes from the moment of birth to the end of the neonatal period (at the same time, on the 5th day there is an intersection of the curves of the fall of neutrophils and the rise of lymphocytes);

) a significant number of young forms of neutrophils;

) a large number of young forms, myelocytes, blast forms;

) structural immaturity and fragility of leukocytes.

Conclusion

The blood system is vital to the human body. It includes bone marrow, spleen, lymph nodes, liver, circulating and deposited blood. This is a very dynamic system that clearly responds to exogenous and endogenous influences on the human body and responds with unique reactions to changes occurring in it.

During ontogenesis, in each age period, blood has its own characteristic features. They are determined by the level of development of the morphological and functional structures of the organs of the blood system, as well as neurohumoral mechanisms for regulating their activity.

The blood system subtly responds to physical and chemical influences from the external and internal environments of the body, therefore blood tests provide the basis for important general biological conclusions that allow competent and most accurate diagnosis and, on the basis of this, formulate a conclusion about the presence and type of a typical form of blood system pathology, about its possible causes, development mechanisms and outcome.

Literature

1.Human anatomy. /Ed. Sapina M.R. In 2 volumes. - M.: Medicine, 1997.

.Atlas of blood cells and bone marrow (edited by G.I. Kozinets). - M.: "Triad-X", 1998, - 160 p.

2.Age-related features of the blood system / A.A. Markosyan, Kh.D. Lomazova. - Moscow, 2002 // Reader on developmental physiology: textbook: for higher education students educational institutions, studying in the specialties - “Preschool pedagogy and psychology”, “Pedagogy and methods of preschool education” / Comp. MM. Bezrukikh, V.D. Sonkin, D.A. Farber. - Moscow: Academy, 2002. - P. 81-102.

.Ermolaev Yu.A. Age physiology. Tutorial for students of pedagogical universities. - M.: graduate School, 1985, 384 p.

5.Kurepina M.M. Human anatomy. - M.: Education, 1979.

.The beginnings of physiology: Textbook for universities / Edited by academician. HELL. Nozdracheva. - St. Petersburg: Lan Publishing House, 2001. - 1088 p.

.Pathological physiology / Ed. V.V. Novitsky, E.D. Goldberg - Tomsk, 2001 - pp. 136-141

8.Guide to hematology in 3 volumes, volume 1. / Ed. Vorobyova A.I. Ed. "Newdiamed". M., 2002, 280 s

.Guide to hematology in 3 volumes, volume 2. / Ed. Vorobyova A.I. Ed. "Newdiamed". M., 2003, 270 p.

.Shiffman Fred. J., Blood Pathophysiology, St. Petersburg, 2000

Similar works to - Morphology of the blood system and its age-related features

Plan

Age-related features of the blood and circulatory system

Lecture 6

Literature

11. Bezrukikh M.M., Sonkin V.D., Farber D.A. Developmental physiology: physiology of child development. – M.: Academy, 2003. – 416 p.

12. Belyaev N.G. Age physiology. – Stavropol: SSU, 1999. – 103 p.

13. Obreimova N.I., Petrukhin A.S. Fundamentals of anatomy, physiology and hygiene of children and adolescents. – M.: Academy, 2000. – 376 p.

14. Sapin M.R., Bryksina Z.G. Anatomy, physiology of children and adolescents. – M.: Academy, 2002. – 456 p.

1. Age-related characteristics of blood quantity and composition 1

2. The heart and its age-related characteristics 6

3. age-related features of the circulatory system 8

4. Age-related characteristics of the cardiovascular system’s response to physical activity 10

The amount of blood in the human body changes with age. Children have more blood relative to their body weight than adults. In newborns, blood makes up 14.7% of the mass, in children one year old - 10.9%, in children 14 years old - 7%. This is due to a more intense metabolism in the child’s body. The total amount of blood in newborns is on average 450-600 ml, in children 1 year old - 1.0-1.1 l, in children 14 years old - 3.0-3.5 l, in adults weighing 60-70 kg the total the amount of blood is 5-5.5 l.

In healthy people the ratio between plasma and formed elements fluctuates slightly (55% plasma and 45% formed elements). In young children, the percentage of formed elements is slightly higher.

The number of blood cells also has its own age-related characteristics. Thus, the number red blood cells (red blood cells) in a newborn is 4.3-7.6 million per 1 mm 3 of blood, by 6 months the number of erythrocytes decreases to 3.5-4.8 million per 1 mm 3, in children 1 year old - up to 3.6-4.9 million per 1 mm 3 and at 13-15 years old reaches the level of an adult. It should be emphasized that the content of blood cells also has gender characteristics, for example, the number of red blood cells in men is 4.0-5.1 million per 1 mm 3, and in women – 3.7-4.7 million per 1 mm 3.

The respiratory function of erythrocytes is associated with the presence in them hemoglobin , which is an oxygen carrier. The hemoglobin content in the blood is measured either in absolute values or as a percentage. The presence of 16.7 g of hemoglobin in 100 ml of blood is taken as 100%. An adult's blood usually contains 60-80% hemoglobin. Moreover, the hemoglobin content in the blood of men is 80-100%, and in women – 70-80%. The hemoglobin content depends on the number of red blood cells in the blood, nutrition, exposure to fresh air and other reasons.

The hemoglobin content in the blood also changes with age. In the blood of newborns, the amount of hemoglobin can vary from 110% to 140%. By the 5-6th day of life this figure decreases. By 6 months, the amount of hemoglobin is 70-80%. Then, by 3-4 years, the amount of hemoglobin increases slightly (70-85%), at 6-7 years there is a slowdown in the increase in hemoglobin content, from 8 years of age the amount of hemoglobin increases again and by 13-15 years it is 70-90%, i.e., reaches the level of an adult. A decrease in the number of red blood cells below 3 million and the amount of hemoglobin below 60% indicates the presence of an anemic condition (anemia).

Anemia– a sharp decrease in blood hemoglobin and a decrease in the number of red blood cells. Various types of diseases and especially unfavourable conditions the lives of children and adolescents lead to anemia. It is accompanied by headaches, dizziness, fainting, and has a negative impact on performance and learning success. In addition, in anemic students, the body's resistance sharply decreases, and they often get sick for a long time.

The primary preventive measure against anemia is the correct organization of the daily routine, a balanced diet rich in mineral salts and vitamins, strict rationing of academic, extracurricular, work and creative activity To prevent overfatigue from developing, the required amount of daily physical activity in conditions open air and wise use of natural factors.

One of the important diagnostic indicators indicating the presence inflammatory processes and other pathological conditions, is erythrocyte sedimentation rate .In men it is 1-10 mm/h, in women – 2-15 mm/h. This figure changes with age. In newborns, the erythrocyte sedimentation rate is low (from 2 to 4 mm/h). In children under 3 years of age, the ESR value ranges from 4 to 12 mm/h. At the age of 7 to 12 years, the ESR value does not exceed 12 mm/h.

Another class of shaped elements are leukocytes - white blood cells. The most important function of leukocytes is to protect against microorganisms and toxins entering the blood. Based on their shape, structure and function, different types of leukocytes are distinguished. The main ones are: lymphocytes, monocytes, neutrophils. Lymphocytes are formed mainly in the lymph nodes. They produce antibodies and play a large role in providing immunity. Neutrophils are produced in the red bone marrow: they play a major role in phagocytosis. Capable of phagocytosis and monocytes – cells formed in the spleen and liver.

There is a certain relationship between different types leukocytes, expressed as a percentage, the so-called leukocyte formula . In pathological conditions, both the total number of leukocytes and the leukocyte formula change.

The number of leukocytes and their ratio change with age. Thus, the blood of an adult contains 4000-9000 leukocytes per 1 μl. A newborn has significantly more leukocytes than an adult (up to 20 thousand in 1 mm 3 of blood). In the first day of life, the number of leukocytes increases (resorption of decay products of the child’s tissues, tissue hemorrhages that are possible during childbirth occurs) to 30 thousand per 1 mm 3 of blood.

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

The leukocyte formula in the first years of a child’s life is characterized by an increased content of lymphocytes and a decreased number of neutrophils. By 5-6 years, the number of these formed elements levels out, after which the percentage of neutrophils increases, and the percentage of lymphocytes decreases. The low content of neutrophils, as well as their insufficient maturity, explains the greater susceptibility of young children to infectious diseases. In addition, the phagocytic activity of neutrophils in children of the first years of life is the lowest.

Age-related changes in immunity. The question of the development of the immunological apparatus in pre- and postnatal ontogenesis is still far from being resolved. It has now been discovered that the fetus in the mother’s body does not yet contain antigens; it is immunologically tolerant. No antibodies are formed in his body, and thanks to the placenta, the fetus is reliably protected from antigens in the mother’s blood.

Obviously, the transition from immunological tolerance to immunological reactivity occurs from the moment the child is born. From this time on, his own immunology apparatus begins to function, which comes into effect in the second week after birth. The formation of own antibodies in the child’s body is still insignificant, and important in immunological reactions during the first year of life they have antibodies obtained from mother's milk. Intensive development of the immunological apparatus occurs from the second year to approximately 10 years, then from 10 to 20 years the intensity of immune defense weakens slightly. From 20 to 40 years of age, the level of immune reactions stabilizes and after 40 years of age begins to gradually decline.

In addition to antibodies, some proteins are of great importance in immunity. These are immunoglobulins A, M, G, E, D.

IgG – protection against viruses (measles, smallpox, rubella, mumps, etc.) and bacterial infections caused by gram-positive microbes (staphylococci, streptococci).

IgM – protection against gram-negative bacteria (Shigella, typhoid fever) and some viruses.

IgA - activates local nonspecific immunity - lysozyme, protective properties of sweat, saliva, tears, etc.

IgD has a similar effect.

IgE – enhances the phagocytic activity of leukocytes and is involved in allergic reactions.

Newborns have a high level of IgG, since this protein is obtained from the mother. They either lack the remaining immunoglobulins or have very few of them. This explains the relatively high resistance of children in the 1st month of life to viral infections(measles, chickenpox), but, on the other hand, high sensitivity to bacterial infections.

By 3-6 months, maternal immunoglobulins are destroyed and the synthesis of their own immunoglobulins begins. By 4-5 years, the level of IgM reaches the adult level, IgG - by 5-6 years, IgA - by 10-12 years, IgD - by 5-10 years. In newborns, the lack of IgA is partially compensated by colostrum and breast milk.

Preventive vaccinations are of great importance in the formation of sufficient resistance of the body of children and adolescents to diseases. Before recent years The following scheme of basic vaccinations and their revaccination (repetition) was in effect.

1. Newborns (first 12 hours of life) - first vaccination against viral hepatitis IN.

2. Newborns 3-7 days old - vaccination against tuberculosis.

3. 1 month – second vaccination against viral hepatitis B.

4. 3 months – first vaccination against diphtheria, whooping cough, tetanus and polio.

5. 4.5 months - second vaccination against diphtheria, whooping cough, tetanus, polio.

6. 6 months – third vaccination against diphtheria, whooping cough, tetanus, polio.

7. 12 months – vaccination against measles, rubella, mumps.

8. 18 months – first revaccination against diphtheria, whooping cough, tetanus, polio.

9. 20 months – second revaccination against polio.

10. 6 years – revaccination against measles, rubella, mumps.

11. 7 years – revaccination against tuberculosis, second revaccination against diphtheria and tetanus.

12. 13 years old - vaccination against rubella (girls), vaccination against viral hepatitis B (for those who have not been vaccinated before).

13. 14 years – third revaccination against diphtheria and tetanus, revaccination against tuberculosis, third revaccination against polio.

14. Adults - revaccination against diphtheria and tetanus every 10 years from the date of the last revaccination.

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

Platelets are produced in the red bone marrow and spleen. The main function of platelets is associated with their participation in blood clotting. The normal functioning of blood circulation, which prevents both blood loss and blood clotting inside the vessel, is achieved by a certain balance of two systems existing in the body - coagulation and anti-coagulation.

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

Red blood cells contain special substances antigens, or agglutinogens, and in plasma proteins agglutinins, with a certain combination of these substances, red blood cells stick together - agglutination. One of the most significant agglutinogens for age-related physiology is Rh factor . It is found in 85% of people (Rh-positive), 15% do not have this factor in their blood (Rh-negative). When Rh-positive blood is transfused into a Rh-negative person, Rh-negative antibodies appear in the blood, and if Rh-positive blood is re-transfused, serious complications in the form of agglutination can occur. The Rh factor is especially important to consider during pregnancy. If the father is Rh positive and the mother is Rh negative, the fetal blood will be Rh positive, since this is a dominant trait. Fetal agglutinogens, entering the mother's blood, will cause the formation of antibodies (agglutinins) to Rh-positive red blood cells. If these antibodies penetrate the fetal blood through the placenta, agglutination will occur and the fetus may die. Since the amount of antibodies in the mother's blood increases with repeated pregnancies, the danger to children increases. In this case, either a woman with Rh-negative blood is given anti-Rhesus gammaglobulin in advance, or a replacement blood transfusion is given to the newly born child.

Age anatomy and physiology Antonova Olga Aleksandrovna

Topic 7. AGE FEATURES OF BLOOD AND CIRCULATION

7.1. general characteristics blood

Blood, lymph and tissue fluid are the internal environment of the body in which the vital activity of cells, tissues and organs takes place. The internal environment of a person maintains a relative constancy of its composition, which ensures the stability of all functions of the body and is the result of reflex and neurohumoral self-regulation. Blood, circulating in blood vessels, performs a number of vital functions: transport (transports oxygen, nutrients, hormones, enzymes, and also delivers residual metabolic products to the excretory organs), regulatory (maintains relative constancy of body temperature), protective (blood cells provide immune response reactions).

Amount of blood. Deposited and circulating blood. The amount of blood in an adult is on average 7% of body weight, in newborns - from 10 to 20% of body weight, in infants - from 9 to 13%, in children from 6 to 16 years old - 7%. How younger child, the higher his metabolism and the greater the amount of blood per 1 kg of body weight. Newborns have 150 cubic meters per 1 kg of body weight. cm of blood, in infants - 110 cubic meters. cm, for children from 7 to 12 years old - 70 cubic meters. cm, from 15 years old - 65 cubic meters. cm. The amount of blood in boys and men is relatively greater than in girls and women. At rest, approximately 40–45% of the blood circulates in the blood vessels, and the rest is in the depot (capillaries of the liver, spleen and subcutaneous tissue). Blood from the depot enters the general bloodstream when body temperature rises, muscle work, rise to altitude, and blood loss. Rapid loss of circulating blood is life-threatening. For example, with arterial bleeding and loss of 1/3-1/2 of the total amount of blood, death occurs due to a sharp drop in blood pressure.

Blood plasma. Plasma is the liquid part of the blood after all the formed elements have been separated. In adults it accounts for 55–60% of the total blood volume, in newborns it is less than 50% due to the large volume of red blood cells. The blood plasma of an adult contains 90–91% water, 6.6–8.2% proteins, of which 4–4.5% albumin, 2.8–3.1% globulin and 0.1–0.4% fibrinogen; the rest of the plasma consists of minerals, sugar, metabolic products, enzymes, and hormones. The protein content in the plasma of newborns is 5.5–6.5%, in children under 7 years of age – 6–7%.

With age, the amount of albumin decreases and globulin increases; the total protein content approaches the level of adults by 3–4 years. Gamma globulins reach the adult norm by 3 years, alpha and beta globulins by 7 years. The blood levels of proteolytic enzymes increase after birth and reach adult levels by the 30th day of life.

Blood minerals include table salt (NaCl), 0.85-0.9%, potassium chloride (KC1), calcium chloride (CaC12) and bicarbonates (NaHCO3), 0.02% each, etc. In newborns, the amount of sodium less than in adults, and reaches normal by 7–8 years. From 6 to 18 years of age, sodium content ranges from 170 to 220 mg%. The amount of potassium, on the contrary, is highest in newborns, lowest at 4–6 years of age and reaches the adult norm by 13–19 years.

Boys aged 7-16 years have 1.3 times more inorganic phosphorus than adults; organic phosphorus is 1.5 times more than inorganic phosphorus, but less than in adults.

The amount of glucose in the blood of an adult on an empty stomach is 0.1–0.12%. The amount of blood sugar in children (mg%) on an empty stomach: in newborns – 45–70; for children 7-11 years old – 70–80; 12–14 years old – 90-120. The change in blood sugar levels in children aged 7–8 years is significantly greater than in children aged 17–18 years. Significant fluctuations in blood sugar levels occur during puberty. With intense muscular work, blood sugar levels decrease.

In addition, blood plasma contains various nitrogenous substances, amounting to 20–40 mg per 100 cubic meters. cm blood; 0.5–1.0% fat and fat-like substances.

The viscosity of the blood of an adult is 4–5, of a newborn – 10–11, of a child in the first month of life – 6, then a gradual decrease in viscosity is observed. The active blood reaction, depending on the concentration of hydrogen and hydroxyl ions, is slightly alkaline. The average blood pH is 7.35. When acids formed during metabolism enter the blood, they are neutralized by a reserve of alkalis. Some acids are removed from the body, for example, carbon dioxide is converted into carbon dioxide and water vapor, exhaled during increased ventilation of the lungs. When there is excessive accumulation of alkaline ions in the body, for example during a vegetarian diet, they are neutralized by carbonic acid, which is retained when ventilation of the lungs decreases.

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Features of metabolism in the formed elements of blood Red blood cells: 1. Mature red blood cells lack a nucleus, so proteins are not synthesized in the cell. The red blood cell is almost completely filled with hemoglobin.2. Red blood cells do not have mitochondria, therefore the reactions of the TCA cycle, CTD, and

The process of intrauterine hematopoiesis includes 3 stages:

1. Yolk stage. Starts from the 3rd week and continues until the 9th week. Hematopoiesis occurs in the vessels of the yolk sac (primitive primary erythroblasts (megaloblasts) containing HbP are formed from stem cells.

2. Hepatic (hepato-lienal) stage. Starts from the 6th week and continues almost until birth. Initially, both megaloblastic and normoblastic erythropoiesis occur in the liver, and from the 7th month only normoblastic erythropoiesis occurs. Along with this, granulocyto-, megakaryocyto-, monocyto- and lymphocytopoiesis occurs. From the 11th week to the 7th month, erythrocyte-, granulocyto-, monocyto- and lymphocytopoiesis occurs in the spleen.

3. Bone marrow(medullary) stage. It begins at the end of the 3rd month and continues into postnatal ontogenesis. In the bone marrow of all bones (starting from the clavicle), normoblastic erythropoiesis, granulocyto-, monocyto-, megakaryocytopoiesis and lymphopoiesis occur from stem cells. The role of the organs of lymphopoiesis during this period is performed by the spleen, thymus, lymph nodes, palatine tonsils and Peyer's patches.

In children, with age, there is a gradual decrease in myeloid tissue in the bone marrow and functional lability of the hematopoietic apparatus is revealed. The possibility of returning to the megaloblastic type of hematopoiesis remains.

Blood quantity. Newborns and infants have a higher relative amount of blood (15% and 14% of body weight, respectively). Decrease in value this indicator to adult level occurs by 6 - 9 years. There is a slight increase in the amount of blood during puberty. With aging, the relative blood mass decreases (up to 67 ml/l).

Relatively high hematocrit(0.54) in newborns decreases to the level of adults by the end of the 1st month, after which it decreases to 0.35 in infancy and childhood (at 5 years - 0.37, at 11-15 years - 0.39) , after which its value increases and by the end of puberty the hematocrit reaches the level of adults (0.40 - 0.45).

Children have relatively high blood levels lactic acid(2.0 - 2.4 mmol/l), which is a reflection of increased glycolysis. In an infant, its level is 30% higher than in adults. With age, its amount decreases (at the age of 1 year - 1.3 - 1.8 mmol/l).

In newborns, content proteins in the blood is 48 - 56 g/l. Their number increases to the level of adults by 3–4 years. In children younger age Individual fluctuations in the amount of proteins in the blood are characteristic. The relatively low protein level is due to insufficient liver function (protein-forming). During ontogenesis, the A/G ratio changes. In the first days after birth, there are more globulins in the blood, especially g-globulins (from the mother's plasma). They then quickly collapse. In the first months, the albumin content is reduced (37 g/l). It gradually increases and by 6 months reaches 40 g/l, and by 3 years it reaches adult levels. The high content of g-globulins at the time of birth is explained by their ability to pass through the placental barrier. With old age, there is a slight decrease in protein concentration and protein coefficient due to a decrease in albumin content and an increase in the amount of globulins.

The low level of proteins in the blood of newborns causes lower oncotic blood pressure compared to adults.

In newborns pH and blood buffer bases are reduced (decompensated acidosis on the 1st day, and then compensated acidosis). With old age, the amount of buffer bases decreases (especially blood bicarbonates).

Relative density blood levels in newborns are higher (1.060-1.080) than in adults. Then the established relative blood density during the first months remains at the level of adults.

Viscosity blood levels in newborns are relatively high (10.0-14.8), which is 2-3 times higher than in adults (mainly due to an increase in the number of red blood cells). By the end of the 1st month, viscosity decreases and remains at a relatively constant level, without changing with old age.

Erythropoiesis. The number of red blood cells in the fetus gradually increases, and there is a decrease in their diameter, volume and number of nucleated cells. In newborns, the intensity of erythropoiesis is approximately 5 times higher than in adults. The number of red blood cells in them on the 1st day is increased compared to adults and reaches 6-10 x10 12 / l. On the 2-3rd day their quantity decreases as a result of their destruction (physiological jaundice) and during the 1st month their content decreases to 4.7x10 12 / l. In this case, anisocytosis, poikilocytosis and polychromatophilia are detected, and sometimes nucleated red blood cells are also found. During the first half of the year, infants are characterized by a further decrease in the number of red blood cells, after which their number increases to 4.2x10 12 /l. Starting from the age of 4, there is a decrease in myeloid tissue and during puberty, hematopoiesis is preserved in the red bone marrow of the spongy substance of the vertebral bodies, ribs, sternum, leg bones and femurs. With aging, there is a decrease in the total mass of red bone marrow and its proliferative activity. There is a tendency towards a decrease in the number of red blood cells and hemoglobin.

Hemoglobin. The function of an oxygen carrier in an embryo up to 9-12 weeks is performed by the embryonic (primitive) hemoglobin(HbP), which is replaced by fetal hemoglobin (HbF) by the 3rd month of intrauterine development. At the 4th month, adult hemoglobin (HbA) appears in the fetal blood and its amount does not exceed 10% until 8 months. Newborns still retain up to 70% HbF and already contain 30% HbA. The amount of Hb is increased (170 - 246 g/l), but, starting from the 1st day, its content gradually decreases. In elderly and senile people, the Hb content decreases slightly and fluctuates within the lower limit of the norm for mature age.

ESR in newborns it is lower than in adults and equals 1-2 mm/h.

Leukocytes. In newborns, immediately after birth, the number of leukocytes is increased and reaches 15 x 10 12 / l (leukocytosis of newborns). After 6 hours, their quantity increases to 20 x10 12 /l, after 24 hours - 28 x10 12 /l, 48 hours - 19 x10 12 /l. The regeneration index is increased and a shift in the leukocyte formula to the left is noted. The highest increase in the number of leukocytes is observed on the 2nd day. Then their number decreases and the maximum drop in the curve occurs on the 5th day, and by the 7th day their number approaches the upper limit of the adult norm. In infants, there is a relatively low motor and phagocytic activity of leukocytes. The picture of white blood in children after the 1st year of life is characterized by a gradual decrease in the absolute number of leukocytes, an increase in the relative number of neutrophils with a corresponding decrease in the number of lymphocytes. In the leukocyte formula, 2 “crossovers” of changes in leukocytes are noted. First- at the age of 3 - 7 days (decrease in the percentage of neutrophils and increase in the percentage of lymphocytes) and second- at the age of 4-6 years (increasing percentage of neutrophils and decreasing percentage of lymphocytes). With old age, leukopenia (leukopenia of old age) and eosinopenia are noted. The functional reserve of leukopoiesis decreases under extreme conditions.

Platelets. The number of platelets in newborns in the first hours after birth ranges from 150 to 320 x 10 9 /l, which on average does not differ significantly from their content in the blood of adults. This is followed by a slight decrease in their quantity (up to 164-178x10 9 /l) by 7-9 days, after which by the end of the 2nd week their content increases and remains practically without significant changes at the level of adults. Children 1 day of life are characterized by a large number of round and young forms of platelets, the number of which decreases with age.

Hemostasis. There is no fibrinogen, prothrombin and accelerin in the blood of the fetus up to 16 - 20 weeks, and therefore it does not clot. Fibrinogen appears at 4-5 months of intrauterine life, its concentration is 0.6 g/l. During this period, the activity of the fibrin-stabilizing factor is still low, but the activity of heparin is high (almost 2 times higher than in adults). The low level of factors of the coagulation and anticoagulation systems of the blood in the fetus is explained by the immaturity of the cellular structures of the liver that carry out their biosynthesis. In the blood of newborns, there is a low concentration of a number of factors (FII, FVII, FIX, FX, FXI, FXIII) of the blood coagulation system, anticoagulants and plasminogen, although the ratio of their concentrations is the same as in adults. In children in the first days of life, blood clotting time is reduced, especially on the 2nd day, after which it gradually increases and reaches the blood clotting rate in adults by the end of adolescence. During childhood, there is a gradual increase in the content of procoagulants and anticoagulants. In this case, heterochronic maturation of individual links (pro- and anticoagulants) in a given postnatal period is characteristic. By the age of 14-16 years, the content and activity of all factors involved in blood coagulation and fibrinolysis reach adult levels.

Blood groups. The formation of factors that determine group membership in ontogeny does not occur simultaneously. Agglutinogens A and B are formed by 2-3 months of the antenatal period, and agglutinins a and b - by the time of or after birth, which determines the low ability of erythrocytes to agglutinate, which reaches its level in adults by 10-20 years.

Agglutinogens of the Rh system appear in the fetus at 2 - 3 months, while the activity of the Rh antigen in the prenatal period is higher than in adults.

TOPIC 6. IMPORTANCE AND AGE CHANGES IN THE MUSCULOSKETAL SYSTEM.

Plan:

Microstructure of muscle fiber. The muscle is distinguished by a middle part - the abdomen, consisting of muscle tissue, and a tendon formed by dense connective tissue. Each muscle consists of a large number of fibers of striated skeletal muscle, located in parallel and interconnected by layers of loose connective tissue, along which nerve fibers and blood vessels approach them. The outside of the striated muscle fiber is covered with sarcolemma; inside, the sarcoplasm contains myofibrils, the contractile apparatus of the muscle fiber, as well as mitochondria and other cell organelles. The fiber is divided into regularly alternating sections (disks) with different optical properties. Some areas are anisotropic, that is, they look dark in ordinary light. Other areas appear light in ordinary light - they are isotropic.

Each myofibril, in turn, consists of 2800 protofibrils, which are long chains of myosin and actin protein molecules. Myosin filaments are twice as thick as actin filaments. In the resting state, the filaments are arranged in such a way that the thin, long actin filaments fit into the gap between the thick, shorter myosin filaments. An important component of the myofibril microstructure is the presence of numerous cross bridges connecting actin and myosin filaments. When the muscle fiber contracts due to these bridges, the filaments begin to slide over each other, the actin filaments move into the gap between the myosin filaments. The cause of sliding is the chemical interaction between actin and myosin in the presence of calcium ions and ATP. Something similar to a gear wheel is observed, pulling one group of threads relative to another. The role of the denticles in this process belongs to the cross bridges, due to which the actin and myosin molecules interact with each other.

Indicators of muscles in ontogenesis. Throughout ontogenesis, the total mass of muscle tissue changes significantly, and the weight of muscles during growth increases much more intensively than the weight of many other organs. For example, in newborns the mass of all muscles is 23% of body weight, and at 8 years old - 27%, at 17-18 years old - 44% (in athletes, as is known, muscle mass can reach 50%).

During ontogenesis, significant changes occur in the microstructure of muscles. Height muscle mass in the postnatal period occurs due to an increase not in the number, but in the size of muscle fibers. Myofibrils thicken and, as a result, muscle fibers thicken. Stabilization and cessation of muscle fiber growth occurs by the age of 18-20, that is, at approximately the same time as the stabilization of skeletal growth. But in old age, the opposite process occurs - atrophy of muscle fibers, leading to a decrease in their diameter. The transverse striation of muscle fibers weakens with aging. The direction of the muscle fibers ceases to be strictly parallel, and groups of muscle fibers appear irregularly, spirally, and even ring-shaped. The development of the histostructure of connective tissue elements of muscles is especially intensive in early childhood, reaching a significant level by 7 years. At the age of 19-20, the connective tissue elements of the muscles are a powerful framework for both the entire muscle and each muscle fiber separately. With aging, muscle connective tissue undergoes atrophic changes. In the sarcoplasm, fatty inclusions are found, as well as areas of waxy degeneration.

The nuclei of muscle fibers, which play an important role in the development and functioning of the tissue, undergo significant changes during ontogenesis. It is known, for example, that the muscles of an embryo are much richer in nuclei than the muscles of children and adults. The decrease in the number of nuclei occurs in parallel with a thickening of the muscle fiber diameter. With aging, as dystrophic changes develop, the number of nuclei begins to increase again, and their shape also changes.

Innervation and blood supply to muscle units. Motor nerve endings in muscles appear long before birth, and their network continues to develop for a long time after birth. But the proprioceptor apparatus is formed at a faster pace, and is ahead of the motor endings in its development. By the time of birth, the neuromuscular spindle already has a well-defined capsule, convoluted and branched nerve fibers and a muscle core. With age, not only the structure changes, but also their distribution in the muscle. So, if in a newborn the “spindles” are located more or less evenly, then by the age of 4-11 years the neuromuscular spindles are found to a greater extent in the terminal thirds than in the middle. Up to about 17 years of age and older, the number of muscle spindles increases especially rapidly in the areas of the muscles that experience the greatest stretch. The blood supply to muscles in embryonic and early childhood is already well developed, but in contrast to the adult organism, in this period the type of branching of muscle vessels is different: it can be scattered or transitional, and in an adult it is main. In general, it can be noted that the structure of the arterial bed of the muscles is formed already at birth.

During ontogenesis, muscle functions also change significantly. One of the important indicators of muscle function is their lability. Under lability or functional mobility N.E. Vvedensky understood the greater or lesser speed of those elementary reactions that accompany the physiological activity of a given apparatus, in our case the muscular one. A measure of lability according to Vvedensky is the largest number of action potentials that an excitable substrate is capable of reproducing in 1 second under the influence of a stimulus. The lowest lability is observed in the prenatal period. Skeletal muscles reproduce only 3-4 contractions per second, while in an adult it is up to 60-80. In the prenatal period, when the optimal frequency of irritation is exceeded, the muscle continues to contract as long as the irritation lasts, while the state of pessimism characteristic of an adult is absent. Pessimal inhibition consists, as is known, in reducing the magnitude of tetanic contraction with very high frequency irritation of the muscle, while the force of its contraction decreases. Age-related changes in the functional lability of muscles are largely associated with the state of neuromuscular synapses. This is indicated, for example, by the impossibility of realizing a true pessimum in the antenatal period. In addition, as myoneural synapses mature, the time for transmission of excitation from nerve to muscle is shortened by 4 times.

With aging, pessimal inhibition develops much more easily than in adulthood. This is indicated by the fact that in old rats pessimum develops already at a pulse frequency of 60-80, while in young animals, with the same duration of an individual pulse, frequencies of 150-200 Hz are required. These data show that the functional lability of the neuromuscular system decreases with age.

The reflex reaction of antagonist muscles is distinguished by significant originality in the antenatal period. Instead of the reciprocal inhibition reaction typical of an adult organism, in this period the contraction of the flexor is accompanied by a simultaneous contraction of the extensor. This type of reflex muscle contraction is characterized by the participation of not only the muscles of the limbs, but also the respiratory muscles.

One of the significant features of muscle functioning in the antenatal period and newborns is the constant activity of skeletal muscles. On initial stages development, skeletal muscles perform mainly a thermoregulatory function. An adequate stimulus in this case is a decrease in temperature below an indifferent level. Unlike adults, children's skeletal muscles do not relax even during sleep. This constant activity of skeletal muscles stimulates the rapid growth of muscle mass, as well as the development of the working capabilities of the developing muscles. The motor activity of a child in the first months of life is characterized by the so-called flexor hypertension of newborns and a number of generalized motor reflexes (reaching, Babinski motor reflex). As a result of these movements, there is an increase in overall tone.

A powerful incentive development of the neuromuscular system is the emergence and development of anti-gravity reactions (holding the head, sitting posture and standing). At the same time, not only the apparatus of motor activity develops and improves, but the motor-visceral reflexes that arise cause a profound restructuring of the activity of systems such as cardiovascular, respiratory, etc. In the mechanisms of developing changes, significant importance belongs to the strengthening of the tone of the vagus nerve.

Speed of movement characterizes the ability to perform various actions in the shortest period of time. The development of this quality is determined by the state of the musculoskeletal system and the activity of central innervation mechanisms, that is high level speed of movement is closely related to mobility and balance of the processes of excitation and inhibition. With age, the speed of movements increases.

By determining this indicator by the maximum frequency of pedal rotations on a bicycle ergometer, it was possible to establish that the greatest development of this quality is achieved in children 14-15 years old. Speed of movement is closely related to other qualities - strength and endurance. It is noteworthy that the maximum pedaling speed depends on the resistance to pedal movement, since an increase in the load applied in the exercise led to a displacement maximum values speed towards older ages. The same picture was found with increasing pedaling duration, that is, when the subjects needed to show greater endurance. Thus, the speed of movements at different stages of ontogenesis depends on the degree of functional development of nerve centers and peripheral nerves, which ultimately determines the rate of transmission of excitation from neurons to muscle units. Studies have shown that the speed of impulse conduction in the fibers of peripheral motor nerves reaches adult values by the age of 5 years. This position is confirmed by histological data showing that the structure of the fibers of the anterior spinal roots in humans begins to correspond to the structure of the adult body between 2 and 5 years, and the fibers of the dorsal roots - between 5 and 9 years.

Endurance– this is the ability to continue working despite developing fatigue. But despite the great practical significance of elucidating the age-related characteristics of the development of endurance, the development of this aspect of motor qualities has been least studied.

Static endurance (measured by the time the hand squeezes a hand dynamometer with a force equal to half the maximum) increases significantly with age. For example, in 17-year-old boys, endurance was 2 times higher than in seven-year-old boys, and the achievement of adult levels occurs only at 20-29 years of age. By old age, endurance decreases by about 4 times. It is noteworthy that at different age periods endurance does not depend on the development of strength. If the greatest increase in strength is observed at 15-17 years, then the maximum increase in endurance occurs at the age of 7-10 years, that is, with rapid development of strength, the development of endurance slows down.

TOPIC 7. AGE FEATURES OF THE BLOOD SYSTEM.

General properties of blood in ontogenesis. The total amount of blood in relation to the body weight of a newborn is 15%, in children of one year - 11%, and in adults - 7-8%. At the same time, boys have slightly more blood than girls. However, at rest, only 40-45% of the blood circulates in the vascular bed, the rest is in the depot: the capillaries of the liver, spleen and subcutaneous tissue and is included in the bloodstream when body temperature rises, muscle work, blood loss, etc.

The specific gravity of the blood of newborns is slightly higher than that of older children, and is respectively 1.06-1.08. The blood density established in the first months (1.052-1.063) remains until the end of life. Blood viscosity in newborns is 2 times higher than in adults and is 10.0-14.8 conventional units. By the end of the first month, this value decreases and usually reaches average figures - 4.6 conventional units. (relative to water). Blood viscosity values in elderly people do not exceed normal limits (4.5).

Biochemical properties of blood. In humans, the chemical composition of blood is characterized by significant constancy. The greatest deviations, if we take the content of substances in the blood of adults as the norm, can be noted during the neonatal period and in old age.

The protein composition of blood undergoes a number of changes during ontogenesis: from birth to adulthood, the protein content in the blood increases, and certain ratios in protein fractions are established. The functional capabilities of the organs that synthesize plasma proteins, primarily the liver, are relatively low at the time of birth and gradually increase, which leads to normalization of blood composition.

The content of lipid fractions in newborns differs from the spectrum of these substances in older children and adults in that they have a significantly increased content of alpha-lipoproteins and a decreased amount of beta-lipoproteins. By the age of 14, the indicators are approaching the norms of an adult. The amount of cholesterol in the blood of newborns is relatively low and increases with age. It is noted that when carbohydrates predominate in food, the level of cholesterol in the blood increases, and when proteins predominate, they decrease. In old age and old age, cholesterol levels increase.

Formed elements of blood in ontogenesis. The content of erythrocytes in mm3 of blood is also subject to age-related changes. In a newborn, this value ranges from 4.5 million per mm3 to 7.5 million, which is apparently associated with insufficient oxygen supply to the fetus in last days embryonic period and during childbirth. After childbirth, gas exchange conditions improve, and some red blood cells are destroyed. The blood of newborns contains a significant amount of immature forms of red blood cells containing a nucleus.

In children aged 1 to 2 years, large individual differences in the number of red blood cells are observed. A similar wide range in individual data is also noted from 5 to 7 and from 12 to 14 years, which, apparently, is directly related to periods of accelerated growth.

One important property of cell membranes is their selective permeability. This fact determined that when erythrocytes are placed in solutions with different salt concentrations, serious changes in their structure are observed. When erythrocytes are placed in a solution whose osmotic pressure is lower than plasma (hypotonic solution), according to the laws of osmosis, water begins to enter the erythrocyte, they swell and their membranes rupture, hemolysis occurs. In humans, hemolysis begins when his red blood cells are placed in a 0.44-0.48% NaCl solution. The ability of red blood cells to resist hemolysis is called osmotic resistance. It is significantly higher in newborns and infants than in adults. For example, the maximum resistance of erythrocytes in infants is in the range of 0.24-0.32% (adults 0.44-0.48%).

Hemoglobin content in ontogenesis has the following features. During the period of intrauterine life in the fetus in the first 6 months, fetal hemoglobin HbF predominates. The significant fact is that it has a higher affinity for oxygen and can be saturated by 60% O 2 at such an O 2 voltage when the mother’s hemoglobin is saturated by 30%, that is, at the same O 2 voltage, the fetal blood will contain more O 2 than maternal blood. These features of fetal hemoglobin provide the ability to transport oxygen from the mother’s blood to the baby’s blood, satisfying the oxygen needs of tissues. By the time of birth, the amount of HbF decreases and remains at the level of 20%, and 80% is HbA. By 4-5 months of life, only 1-2% HbF remains.

Children of the neonatal period are characterized by an increased hemoglobin content. But, starting from the first day of postnatal life, the amount of hemoglobin gradually decreases, and this drop does not depend on the weight of the child. The amount of Hb in children of the first year decreases significantly by the 5th month and remains at a low level until the end of 1 year; with age, the amount of hemoglobin increases.

In elderly and senile people, the amount of hemoglobin decreases slightly, approaching the lower limit of the norm derived for adulthood.

Leukoformula. The number of leukocytes in a child in the first days of life is higher than in adults, and on average ranges from 10-20 thousand per mm3. Then the white blood cell count begins to fall. As with erythrocytes, there is a wide range of fluctuations in the number of leukocytes in the first days of postnatal life from 4600 to 28 thousand. The following is characteristic of the picture of leukocytes in children of this period. An increase in the number of leukocytes during 3 hours of life (up to 19,600), which is apparently associated with the resorption of decay products of the child’s tissues, tissue hemorrhages possible during childbirth, after 6 hours - 20 thousand, after 24 - 28 thousand, after 48 - 19 thousand. By the 7th day, the number of leukocytes approaches the upper limit of adults and amounts to 8000-11000. In children 10-12 years old, the number of leukocytes in the peripheral blood ranges from 6-8 thousand, i.e. corresponds to the number of leukocytes in adults.

The leukocyte formula (the ratio of different forms of leukocytes in percentage) also has its own age-related characteristics. The leukocyte formula of a child’s blood during the neonatal period is characterized by:

1) a consistent increase in the number of lymphocytes from the moment of birth to the end of the neonatal period (at the same time, on the 5th day there is an intersection of the curves of the fall of neutrophils and the rise of lymphocytes);

2) a significant number of young forms of neutrophils;

3) a large number of young forms, myelocytes, blast forms;

4) structural immaturity and fragility of leukocytes.

In children of the first year of life, with a fairly wide range of fluctuations in the total number of leukocytes, wide ranges of variations in the percentage of individual forms are also observed. The high content of lymphocytes and low number of neutrophils in the first years of life gradually levels out, reaching almost the same values by 5-6 years. After this, the percentage of neutrophils gradually increases, and the percentage of lymphocytes decreases.

Formation of the child's immunity. The role of various factors in this process. As is known, the immune process is understood as the body’s response to a certain kind of irritation, to the invasion of a foreign agent - an antigen. Protecting the body from the invasion of antigens, the blood produces special protein bodies - antibodies, which neutralize antigens, reacting with them in a wide variety of ways. At the same time, lymphocytes actively produce antibodies, with the participation and control of other immune cells. In the embryonic period, antibodies are not produced in the fetus, and despite this, in the first 3 months after birth, children are almost completely immune to infectious diseases. This is explained by the fact that the fetus receives ready-made antibodies (gamma globulins) through the placenta from the mother. During the breast period, the child receives some of the antibodies through breast milk. In addition, the immunity of newborn children to certain diseases is associated with insufficient maturity of the body, especially its nervous system. As the body and its NS mature, the child gradually acquires more and more stable immunological properties. By the second year of life, a significant number of immune bodies are already produced.

It has been noticed that children raised in groups develop immune reactions faster. This is explained by the fact that in a group the child is subjected to hidden immunization: the entry of small doses of the pathogen into the child’s body from sick children does not cause the child to become ill, but activates the production of antibodies. If this is repeated several times, immunity to the disease is acquired.

By the age of 10, the body’s immune properties are well expressed and subsequently they remain at a relatively constant level and begin to decline after 40 years. Preventive vaccinations play an important role in the formation of the body’s immune reactions.

Age-related features of blood circulation. Blood can perform vital functions only if it is in continuous movement. Blood circulation in the body is the essence of blood circulation and is ensured by the activity of the circulatory organs: the heart and blood vessels. The human vascular system, as a representative of the class of mammals, consists of two circles of blood circulation: large and small. The systemic circulation begins in the left ventricle (from the aorta), then the blood flows through the arteries to the tissues and organs in which there is a branched capillary network. The blood, which has given up oxygen and absorbed carbon dioxide and metabolic products, enters the veins ending in the right atrium. The small circle is designed to saturate the blood with oxygen and release carbon dioxide. It begins in the right ventricle, from which blood flows through pulmonary artery enters the lungs and returns through the pulmonary vein to the left atrium. This is the general diagram of the circulatory system in the adult human body.

Age-related features of heart functioning. After birth, the child’s heart grows and enlarges, and morphogenesis processes occur in it. The heart of a newborn has a transverse position and a spherical shape, this is explained by the fact that the relatively large liver makes the vault of the diaphragm high, so the heart of the newborn is located at the level of the 4th left intercostal space. Under the influence of sitting and standing, by the end of the first year of life the diaphragm lowers and the heart takes an oblique position. By 2-3 years, the apex of the heart reaches the level of the 5th rib, and in 10-year-old children the borders of the heart are the same as in adults.

During the first year of life, the growth of the atria outpaces the growth of the ventricles, and only after 10 years does the growth of the ventricles begin to exceed the growth of the atria.

Age-related changes in heart mass are associated with the fact that heart mass grows in the first year of life, doubling by eight months, tripling by three years, fourfold by five, and 11-fold by age 16.

At the same time, the heart mass in boys exceeds this figure in girls in the first years of life, and at the age of 12-13, on the contrary, due to the onset of a period of increased growth in girls, its mass becomes greater than in boys. By the age of 16, girls’ hearts again begin to lag behind boys’ hearts in mass.

Heart rate in the fetus it ranges from 120 to 150 per minute. In the first 2 days after birth, heart rate is slightly lower than intrauterine, which is explained by an increase in intracranial pressure, a change in heat production due to the transition to an environment with a lower temperature, and finally, inhibition of sympathetic influences. In the following week, heart rate increases slightly to 120-140 beats per minute. Subsequently, heart rate decreases with age. For example in children preschool age at 6 years old it is 95 beats/min; for schoolchildren 7-15 years old it varies between 92-76 beats/min

A slowdown in heart rate is the result of a change in the lability of the sinus node and the development of more advanced forms of neurohumoral regulation of the heart. An increase in the tonic influence of the vagus nerve leads not only to a current decrease in heart rate, but also changes the metabolism of the sinus node, leading to a persistent decrease in its lability with age.

After the age of 60, heart rate decreases somewhat, and “rigidity” and “inertness” of the heart rate develops, which is clearly visible under various loads. The slowdown in the rhythm of contractions, in this case, is associated with a decrease in the lability of the sinus node, and its “stiffness” is associated with a weakening of the influence of extracardiac nerves on the heart.

Related information.

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