Anatomical and physiological features of hematopoiesis, classification, main syndromes. Anatomical, physiological and age-related features of the blood system
The blood system includes peripheral blood, hematopoietic and hematopoietic organs (red bone marrow, liver, spleen, The lymph nodes and other lymphoid formations). IN embryonic period hematopoietic organs are the liver, spleen, bone marrow and lymphoid tissue. After the birth of a child, hematopoiesis is concentrated mainly in the bone marrow and occurs in children early age in all bones. Starting from the 1st year of life, signs of the transformation of red bone marrow to yellow (fatty). By puberty, hematopoiesis occurs in flat bones (sternum, ribs, vertebral bodies), epiphyses tubular bones, as well as in the lymph nodes and spleen. Lymph nodes. The most important organs lymphopoiesis. They are richer in newborns compared to adults lymphatic vessels and lymphoid elements with many young forms, the number of which gradually decreases after 4-5 years of life. The morphological and associated functional immaturity of the lymph nodes leads to their insufficient barrier function, and therefore, in children in the first months of life, infectious agents easily penetrate into the lymph nodes. bloodstream. There are no visible changes in the lymph nodes. At the age of 1-3 years, the lymph nodes begin to respond to the introduction of the pathogen. From 7-8 years of age, due to the completion of the development of lymph nodes, local protection against infectious agents becomes possible. The response to infection is an increase in the size of the lymph nodes and their pain on palpation. In healthy children, the cervical (submandibular, anterior and posterior cervical, occipital), axillary and inguinal lymph nodes are palpated. They are single, soft, mobile, not fused to each other or to the surrounding tissue, and range in size from millet grains to lentils. Knowing the location of the lymph nodes, it is possible to determine the direction of spread of the infection and detect their changes during pathological processes. Thymus. Central organ of immunity. By the time the baby is born, it is well developed. At the age of 1 to 3 years, its mass increases. With the onset of puberty, age-related involution begins thymus gland. Spleen. One of the peripheral organs of the immune system. It contains the formation of lymphocytes, destruction of red blood cells and platelets, accumulation of iron, and synthesis of immunoglobulins. The functions of the spleen include depositing blood. Macrophage systems (reticuloendothelial system) is the site of monocyte formation. Tonsils. Main lymphoid formations. In a newborn baby they are located deep and small in size. Due to the structure and functional immaturity of the tonsils, children in the first year of life rarely suffer from tonsillitis. From 5-10 years of age, an enlargement of the palatine tonsils is often observed, often combined with an enlargement of the nasopharyngeal tonsil and other lymphoid formations of the pharynx. From the period of puberty they begin reverse development. Lymphoid tissue is replaced by connective tissue, the tonsils decrease in size and become denser. The child’s hematopoietic system is characterized by pronounced functional instability, slight vulnerability, and the possibility of returning when pathological conditions to the embryonic type of hematopoiesis or the formation of extramedullary foci of hematopoiesis. At the same time, there is a tendency of the hematopoietic system to undergo regeneration processes. These properties are explained by a large number of undifferentiated cells, which, under various irritations, differentiate in the same way as during embryonic development. Blood. As the child grows, the blood undergoes peculiar changes in terms of quality and quantitative composition. According to hematological parameters, all childhood divided into three periods: 1) newborns; 2) infancy; 3) after 1 year of life.
Blood of a newborn. For peripheral blood in this age period it is typical increased amount red blood cells and high hemoglobin levels. Blood contains 60-80% fetal hemoglobin. In premature infants, its level can be 80-90%. Adapted to oxygen transport under conditions placental circulation Fetal hemoglobin binds oxygen faster than adult hemoglobin, playing important role during the period of adaptation of newborns to new living conditions. Gradually, during the first 3 months of life, it is replaced by adult hemoglobin. The color index during the newborn period exceeds 1 (up to 1.3). The erythrocytes of a newborn are characterized by the following qualitative differences: anisocytosis (different colors of erythrocytes), increased content of reticulocytes (young forms of erythrocytes containing granularity), the presence of normoblasts (young forms of erythrocytes with the presence of a nucleus). The erythrocyte sedimentation rate (ESR) in newborns is 2-3 mm/h.
In the leukocyte formula in the first days of a child’s life, neutrophils predominate (about 60-65%). The number of lymphocytes is 16-34%; by the 5-6th day of life, the number of neutrophils and lymphocytes equalizes (the first physiological crossover in the leukocyte formula). By the end of the first month of life, the number of neutrophils decreases to 25-30%, and lymphocytes increase 55-60% (Fig. 55). Blood from a child over 1 year of age. The number of red blood cells and hemoglobin gradually increases; the young forms of red blood cells remain reticulocytes, the number of which ranges from 2 to 5%. The color index is 0.85-0.95, ESR is 4-10 mm/h. The total number of leukocytes decreases, and the character also changes leukocyte formula: the number of lymphocytes gradually decreases, and neutrophils increase, and by 5-6 years their number equalizes, i.e. the second crossing of the neutrophil curve occurs (Fig. 55). Subsequently, the increase in neutrophils and the decrease in lymphocytes continues, and gradually the composition of the blood approaches the composition of the blood of adults. BLOOD COLLAGING SYSTEM newborns and children of the 1st year of life have a number of features. During the newborn period, coagulation is slowed down, which is due to a decrease in the activity of the components of the prothrombin complex: II, V, and VII factors. In children of the 1st year of life, delayed formation of thromboplastin is observed. In the first days of life, the activity of factors X and IV is reduced. During the neonatal period, there is also a slight decrease in the amount of factor I. The activity of the fibrinolytic system in children is often increased. Subsequently, as the liver matures, the activity of coagulation factors becomes sufficient and ensures the balance of the complex homeostasis system.
Clinical methods studies of patients with diseases of the blood system. Morphological examination of peripheral blood, diagnostic value.
Methodological development of a practical lesson for third year students
Faculty of Medicine
Course - III semester
Faculty: medicinal
Lesson duration: 4 academic hours
Location: Cardiology Department of City Clinical Hospital No. 4
1. Topic of classes: Clinical methods for studying patients with diseases of the blood system. Morphological examination of peripheral blood, diagnostic value.
2. The importance of studying this topic. The study of this topic gives an understanding of the methods of clinical examination of patients with diseases of the blood system; the hematopoietic organs are extremely sensitive to various physiological and pathological effects on the body; these are reflected in the picture of peripheral blood tests in normal conditions and in diseases of various body systems.
3. Purpose of the lesson: Teach students clinical examination patients with diseases of the blood system and familiarize students with the main indicators clinical analysis peripheral blood in normal conditions and in diseases of various body systems.
As a result of studying this topic, the student should know:
The main complaints of patients with diseases of the blood system;
Be able to palpate peripheral lymph nodes,
liver, spleen;
Indicators general analysis blood is normal;
Methodology for determining hemoglobin, erythrocytes, leukocytes, hemoglobin content in one erythrocyte, erythrocyte sedimentation rate (ESR);
Method for calculating the leukocyte formula;
Clinical significance blood cells, average hemoglobin content in one red blood cell, ESR;
Leukocyte formula in pathology;
Introduction to sternal puncture, trepanobiopsy;
Understanding the coagulogram;
Self-preparation for the lesson.
As a result of self-study, the student should know:
Anatomical and physiological features of the blood system;
The main complaints of patients with diseases of the blood system, the mechanism of their occurrence;
Data from a general examination of patients with diseases of the blood system;
Be able to palpate peripheral lymph nodes, liver, spleen;
Be able to analyze data from a general blood test, biochemical analysis blood.
Basic sections for repetition obtained by the student in related disciplines:
Anatomical and physiological features of the blood system, diagram of hematopoietic germs;
Metabolism and exchange of iron;
Sections for repetition obtained previously in the discipline of propaedeutics of internal diseases:
History and its sections;
Inspection and palpation of peripheral lymph nodes;
Percussion and palpation of the liver;
Palpation of the spleen;
Auscultation of the heart;
Study of pulse properties;
Criteria for normal peripheral blood analysis.
Questions for review and study in preparation for class.
1. Anatomical and physiological features of the blood system, diagram of hematopoietic germs;
3. The main complaints of patients with diseases of the blood system, the mechanism of their occurrence;
4. The importance of anamnesis to identify factors contributing to the development of anemia.
5. The importance of physical examination of patients with the blood system.
6. The meaning of quantitative and qualitative changes cellular composition blood:
a) erythrocytes;
b) change in the shape and color of red blood cells;
c) change in color indicator;
d) number of reticulocytes;
e) leukocytosis and leukopenia;
e) neutrophilic shift;
g) eosinophilia and aneosinophilia;
h) lymphocytosis and lymphopenia;
i) monocytosis;
Question 1. Anatomical and physiological features of the blood system.
There are several theories of hematopoiesis, but currently the unitary theory of hematopoiesis is generally accepted, on the basis of which a hematopoiesis scheme was developed (I. L. Chertkov and A. I. Vorobyov, 1973).
- unitary theory (A. A. Maksimov, 1909) - all formed elements of blood develop from a single precursor of a stem cell;
- the dualistic theory provides for two sources of hematopoiesis, for myeloid and lymphoid;
- The polyphyletic theory provides for each shaped element its own source of development.
In the process of step-by-step differentiation of stem cells into mature blood cells, in each row of hematopoiesis, intermediate types cells that make up classes of cells in the hematopoietic scheme. In total, 6 classes of cells are distinguished in the hematopoietic scheme:
1st class - stem cells;
Class 2 - semi-stem cells;
Class 3 - unipotent cells;
Class 4 - blast cells;
Class 5 - maturing cells;
Grade 6 - mature shaped elements.
Morphological and functional characteristic cells of different classes of hematopoiesis.
1 class- a pluripotent stem cell capable of maintaining its population. In morphology it corresponds to a small lymphocyte, it is pluripotent, that is, capable of differentiating into any formed element of the blood. The direction of stem cell differentiation is determined by the level of this formed element in the blood, as well as the influence of the microenvironment of stem cells - the inductive influence of stromal cells of the bone marrow or other hematopoietic organ. Maintaining the size of the stem cell population is ensured by the fact that after mitosis of the stem cell, one of the daughter cells takes the path of differentiation, and the other takes on the morphology of a small lymphocyte and is a stem cell. Stem cells rarely divide (once every six months), 80% of stem cells are in a state of rest and only 20% are in mitosis and subsequent differentiation. In the process of proliferation, each stem cell forms a group or clone of cells and therefore stem cells in the literature are often called clone-forming units - CFU.
2nd grade- semi-stem, limited pluripotent (or partially committed) cells - precursors of myelopoiesis and lymphopoiesis. They have the morphology of a small lymphocyte. Each of them produces a clone of cells, but only myeloid or lymphoid. They divide more often (every 3-4 weeks) and also maintain the size of their population.
3rd grade- unipotent poetin-sensitive cells - the predecessors of their hematopoietic series. Their morphology also corresponds to a small lymphocyte. Able to differentiate into only one type of shaped element. They divide frequently, but the descendants of these cells some enter the path of differentiation, while others maintain the population size of this class. The frequency of division of these cells and the ability to differentiate further depends on the content in the blood of special biological active substances- poetins specific for each series of hematopoiesis (erythropoietins, thrombopoietins and others).
The first three classes of cells are combined into a class of morphologically unidentifiable cells, since they all have the morphology of a small lymphocyte, but their developmental potencies are different.
4th grade- blast (young) cells or blasts (erythroblasts, lymphoblasts, etc.). They differ in morphology from both the three preceding and subsequent classes of cells. These cells are large, have a large loose (euchromatin) nucleus with 2-4 nucleoli, the cytoplasm is basophilic due to large number free ribosomes. They divide frequently, but the daughter cells all embark on the path of further differentiation. Based on their cytochemical properties, blasts of different hematopoietic series can be identified.
5th grade- a class of maturing cells characteristic of their hematopoietic series. In this class there can be several varieties of transitional cells - from one (prolymphocyte, promonocyte) to five in the erythrocyte series. Some maturing cells in small quantities can enter the peripheral blood (for example, reticulocytes, young and band granulocytes).
6th grade- mature blood cells. However, it should be noted that only erythrocytes, platelets and segmented granulocytes are mature terminal differentiated cells or their fragments. Monocytes are not fully differentiated cells. Leaving the bloodstream, they differentiate into final cells - macrophages. When lymphocytes encounter antigens, they turn into blasts and divide again.
The totality of cells that make up the line of differentiation of a stem cell into a certain shaped element form its differential or histological series. For example, erythrocyte differential is:
- stem cell;
- semi-stem cell precursor of myelopoiesis;
- unipotent erythropoietin-sensitive cell;
- erythroblast;
- maturing cells - pronormocyte, basophilic normocyte, polychromatophilic normocyte, oxyphilic normocyte, reticulocyte, erythrocyte.
In the process of maturation of erythrocytes in class 5, the following occurs: synthesis and accumulation of hemoglobin, reduction of organelles, reduction of the nucleus. Normally, the replenishment of erythrocytes is carried out mainly due to the division and differentiation of maturing cells of pronormocytes, basophilic and polychromatophilic normocytes. This type of hematopoiesis is called homoplastic hematopoiesis. In case of severe blood loss, the replenishment of red blood cells is ensured not only by the increased division of maturing cells, but also by cells of classes 4, 3, 2 and even class 1, a heteroplastic type of hematopoiesis that precedes reparative regeneration of blood. Blood is a liquid (liquid tissue of mesodermal origin), red in color, weak alkaline reaction, salty taste with a specific gravity of 1.054-1.066. Together with tissue fluid and lymph, it forms the internal environment of the body. Blood performs many functions. The most important of them are the following:
Transport nutrients from digestive tract to tissues, places of reserve reserves from them (trophic function);
Transport of metabolic end products from tissues to excretory organs (excretory function);
Transport of gases (oxygen and carbon dioxide from respiratory organs to tissues and back; oxygen storage (respiratory function);
Transport of hormones from glands internal secretion to organs ( humoral regulation);
Protective function- carried out due to the phagocytic activity of leukocytes ( cellular immunity), the production of antibodies by lymphocytes that neutralize genetically foreign substances (humoral immunity);
Blood clotting, preventing blood loss;
Thermoregulatory function - redistribution of heat between organs, regulation of heat transfer through the skin;
Mechanical function - imparting turgor tension to organs due to the flow of blood to them; ensuring ultrafiltration in the capillaries of the nephron capsules of the kidneys, etc.;
Homeostatic function - maintaining constant internal environment organism, suitable for cells in terms of ionic composition, concentration of hydrogen ions, etc.
The relative constancy of the composition and properties of blood - homeostasis is necessary and prerequisite vital activity of all tissues of the body. Of the total blood volume, approximately half circulates throughout the body. The remaining half is retained in the dilated capillaries of some organs and is called deposited. The organs in which blood is deposited are called blood depots.
Hematopoiesis scheme
(I.L. Chertkov and A.I. Vorobyov, 1973).
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Spleen. It contains up to 16% of all blood in its lacunae - processes of capillaries. This blood is practically excluded from the circulation and does not mix with the circulating blood. When the smooth muscles of the spleen contract, the lacunae are compressed, and blood enters the general channel.
Liver. Contains up to 20% of blood volume. The liver acts as a blood depot due to the contraction of the sphincters of the hepatic veins, through which blood flows from the liver. Then more blood enters the liver than flows out. The capillaries of the liver dilate, the blood flow in it slows down. However, the blood deposited in the liver is not completely excluded from the bloodstream.
Subcutaneous tissue. Deposits up to 10% of blood. IN blood capillaries skin there are anastomoses. Some of the capillaries expand, fill with blood, and blood flow occurs through shortened paths (shunts).
Lungs can also be classified as blood storing organs. The volume of the vascular bed of the lungs is also not constant; it depends on the ventilation of the alveoli, the blood pressure in them and on the blood supply to the vessels of the systemic circulation.
Thus, the deposited blood is excluded from the bloodstream and generally does not mix with the circulating blood. Due to the absorption of water, the deposited blood is thicker, it contains large quantity shaped elements The significance of deposited blood is as follows. When the body is in a state of physiological rest, its organs and tissues do not need increased blood supply. In this case, the deposition of blood reduces the load on the heart, and as a result it works at 1/5 - 1/6 of its capacity. If necessary, blood can quickly pass into the bloodstream, for example when physical work, strong emotional experiences, inhaling air with a high content of carbon dioxide - that is, in all cases where required, it will increase the delivery of oxygen and nutrients to the organs. The vegetative system is involved in the mechanisms of blood redistribution between stored and circulating. nervous system: sympathetic nerves cause an increase in the volume of circulating blood, and parasympathetic - the transition of blood to the depot. When a large amount of adrenaline enters the blood, the blood leaves the depot. In case of blood loss, blood volume is restored primarily due to the transition tissue fluid into the blood, and then the deposited blood enters the bloodstream. As a result, the plasma volume is restored much faster than the amount of formed elements. When the volume of blood increases (for example, when a large amount of blood substitutes is administered or when drinking a large amount of water), some of the fluid is quickly excreted by the kidneys, but most of it passes into the tissues and is then gradually eliminated from the body. Thus, the volume of blood filling the vascular bed is restored.
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Anatomical and physiological features of the blood and lymphatic system
Hematopoiesis, or hematopoiesis, is the process of the emergence and subsequent maturation of blood cells in the so-called hematopoietic organs.
During the intrauterine life of the fetus, there are 3 periods of hematopoiesis. The stages are not strictly demarcated, but gradually replace each other. By the time the child is born, hematopoiesis in the liver stops, and the spleen loses the function of producing red cells, granulocytes, megakaryocytes, while retaining the function of producing lymphocytes. Respectively different periods hematopoiesis - mesoblastic, hepatic and bone marrow - there are three different types of hemoglobin: embryonic, fetal and adult hemoglobin. Gradually, fetal hemoglobin is replaced by adult hemoglobin. By one year, 15% fetal remains, and by 3 years, its amount should not exceed 2%.
Blood of a newborn. The total amount of blood in children is not a constant value and depends on body weight, time of umbilical cord ligation, and term of the child. On average, a newborn's blood volume is about 14.7% of its body weight, and in an adult it is 5.0-5.6%, respectively.
In peripheral blood healthy newborn the content of hemoglobin and red blood cells is increased, and the color index ranges from 0.9 to 1.3. From the very first hours after birth, the breakdown of red blood cells begins, which clinically causes the appearance of physiological jaundice.
The leukocyte formula in newborns has its own characteristics. Oscillation range total number leukocytes is quite wide. During the first hours of life, their number increases slightly and then decreases. A large number of red blood cells, an increased content of hemoglobin in them, and the presence of a large number of young forms of red blood cells indicate enhanced hematopoiesis in newborns and the associated entry into the peripheral blood of young, not yet matured formed elements. These changes are caused by the fact that hormones circulating in the blood of a pregnant woman and stimulating her hematopoietic apparatus, passing into the body of the fetus, increase the functioning of its hematopoietic organs. After birth, the flow of these hormones into the child’s blood stops, as a result of which the amount of hemoglobin, red blood cells, and white blood cells quickly drops. In addition, increased hematopoiesis in newborns can be explained by the peculiarities of gas exchange - insufficient oxygen supply to the fetus.
Blood of children of the first year of life. At this age it continues gradual decline red blood cell count and hemoglobin level. By the end of the 5-6th month the most low performance. This phenomenon is physiological and is observed in all children. It is caused by a rapid increase in body weight, blood volume, insufficient intake of iron from food, and functional failure of the hematopoietic apparatus.
From the beginning of the second year of life Before puberty, the morphological composition of the child’s peripheral blood gradually acquires features characteristic of adults. In the leukogram after 3-4 years, a tendency to a moderate increase in the number of neutrophils and a decrease in the number of lymphocytes is revealed. Between the fifth and sixth years of life, the 2nd crossover in the number of neutrophils and lymphocytes occurs in the direction of increasing the number of neutrophils. It should be noted that in recent decades there has been a tendency towards a decrease in the number of leukocytes in healthy children and adults.
Blood vessels in a newborn it is wider than in an adult. Their lumen gradually increases, but more slowly than the volume of the heart. The blood circulation process in children occurs more intensely than in adults. Pulse in a child, rapid: 120-140 beats per minute. There are 3.5-4 heart beats per inhalation-exhalation cycle. But after six months the pulse becomes less frequent - 100-130 beats.
Blood pressure in children of the first year of life is low. It increases with age, but varies from child to child, depending on weight, temperament, etc.
A newborn's blood contains a large number of erythrocytes and leukocytes, hemoglobin is increased. But gradually over the course of the year their number decreases to normal. Because the hematopoietic system babies are very sensitive to various kinds external and internal harmful effects, children in the first year of life are more likely than older children to develop anemia.
Formation of hematopoiesis in the antenatal and postnatal periods.
The process of intrauterine hematopoiesis includes 3 stages:
1. Yolk stage(mesoblastic, angioblastic) . 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(hepatolienal) 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, myeloid) 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, tonsils and Peyer's patches.
In postnatal life, the bone marrow becomes the main hematopoietic organ. It contains the bulk of hematopoietic stem cells and produces all blood cells. The intensity of hematopoiesis in other organs quickly decreases after birth.
Features of hematopoiesis in a child.
Features of erythropoiesis in a child.
In a newborn baby, HbF predominates, it has a high affinity for oxygen and easily transfers it to tissues. Beginning in the first weeks of postnatal life, there is a sharp increase in HbA synthesis, while HbF production decreases sharply (by approximately 3% per week). By six months of age, the HbA content in the blood is 95-98% (that is, as in an adult), while the HbF concentration does not exceed 3%.
In a newborn child, the number of erythrocytes in the peripheral blood reaches 710 12 /l, and the hemoglobin level is 220 g/l. The increased number of red blood cells in a newborn is explained by the fact that the fetus in the womb and during childbirth experiences a state of hypoxia, which causes an increase in the content of erythropoietin in its blood. However, after birth, the child develops hyperoxia (as external breathing), which leads to a decrease in the intensity of erythropoiesis (due to a decrease in the production of erythropoietin), although in the first days it remains at a fairly high level. A few hours after birth, the number of red blood cells and the level of hemoglobin even increase, mainly due to blood thickening, but by the end of the first day the number of red blood cells begins to fall. Subsequently, the content of erythrocytes decreases on the 5-7th day, and hemoglobin - on the 10th day of the child’s life after massive hemolysis of erythrocytes, accompanied by the so-called transient hyperbilirubinemia of newborns, manifested in some children as “physiological jaundice”. So rapid decline the number of red blood cells in a newborn child is explained by the very short life span of the fetal red blood cells (the child is born with them) - only 10-14 days - and the very high degree of their destruction, 5-7 times higher than the intensity of red blood cell death in an adult. However, during these periods there is also fast education new red blood cells.
Reticulocyte count in full-term newborns it varies widely and ranges from 0.8 to 4%. Moreover, isolated normoblasts may be found in the peripheral blood. However, by the 10th day of a child’s life, the content of reticulocytes does not exceed 2%. By this time, normoblasts disappear in the peripheral blood.
By the 3rd month of a child’s life, the hemoglobin level and the number of red blood cells decrease, reaching 100-130 g/l and 3.0 - 4.510 12 /l, respectively. Such low numbers of red blood cells and hemoglobin levels in infants represent the so-called “physiological anemia” or “erythroblastopenia of infants” and are rarely accompanied clinical manifestations hypoxia. The sharp decrease in the content of erythrocytes is partly due to the hemolysis of fetal erythrocytes, the lifespan of which is approximately 2 times less than that of an adult. In addition, at infant compared to adults, the intensity of erythropoiesis is significantly reduced, which is associated with low education during this period, the main factor of erythropoiesis is erythropoietin. Subsequently, the content of red blood cells and hemoglobin may slightly increase or decrease, or remain at the same level until the age of three. Despite the fact that by the age of ten the number of red blood cells and the level of hemoglobin gradually increases, fluctuations in both directions persist until puberty. At this point, gender differences in red blood standards are noted.
Particularly sharp individual variations in the number of red blood cells and hemoglobin levels are observed in age periods from 1 year to 2 years, from 5 to 7 and from 12 to 15 years, which appears to be associated with significant variations in the growth rate of children.
Newborn red blood cells differ significantly in size and shape: From the first hours of life until the 5th-7th day, children experience macrocytosis and poikilocytosis. Many young immature cells are detected in the blood large forms red blood cells During the first hours of life, the child experiences sharp increase the number of reticulocytes (reticulocytosis) up to 4-6%, which is 4-6 times higher than the number of these forms in an adult. In addition, erythroblasts and normoblasts can be detected in a newborn. All this indicates the intensity of erythropoiesis in the first days of a child’s life.
Red blood cells of the fetus and newborn child, compared to red blood cells of adults, are more sensitive to oxidants, which can lead to disruption of the membrane structure, hemolysis and a reduction in their lifespan. These phenomena are explained by a decrease in sulfhydryl groups in erythrocytes and a decrease in the content of antioxidant enzymes. However, by the end of 1 week of the child’s life, the function of the antioxidant system increases, the activity of enzymes such as glutathione peroxidase, glutathione catalase, superoxide dismutase increases, which protects the membrane structures of the child’s erythrocytes from oxidation and the possibility of further destruction. By this time, most newborns end with physiological jaundice.
On fetal erythropoiesis and especially developing child The same factors influence as in an adult. In particular, iron accumulates in the fetal body throughout its development, but this process is especially intensive in the third trimester of pregnancy. Maternal iron, passing through the placenta, binds to fetal transferrin and is transported mainly to the liver. The fetus has a positive supply of iron, which is due to the perfect mechanisms of the placenta, which make it possible to provide the unborn child with a sufficient amount of iron even in the presence of iron deficiency anemia in a pregnant woman. Such mechanisms include more high ability fetal transferrin is saturated with iron, as well as slow ferritin consumption due to low xanthine oxidase activity.
Therefore, the fetus has a positive iron balance. Iron transport is an active process that goes against the concentration gradient in favor of the fetus without reverse transfer to the placenta and mother. By the time a child is born, the total iron reserve in his body is 75 mg/kg body weight. This value is constant in both full-term and premature babies.
The child has gastrointestinal tract Iron absorption is much more intense than in adults. Thus, in children of the first months of life who are on breastfeeding, up to 57% of consumed iron can be absorbed, at the age of 4-5 months - up to 40-50%, and at 7-10 years - up to 8-18%. In an adult, on average, 1 to 2% of the iron supplied with food is utilized in the gastrointestinal tract.
The daily intake of iron necessary for the development of effective erythropoiesis is as follows: up to 4 one month old- 0.5 mg, from 5 months to a year - 0.7 mg, from 1 year to 12 years - 1.0 mg, from 13 to 16 years - 1.8 mg for boys and 2.4 mg for girls.
As the child grows and his total hemoglobin content increases sharply, the formation of the latter requires an increased intake of iron from food. The need for iron is especially great in adolescence and young adulthood. With the onset of menstruation in girls, the need for iron increases significantly, and it can only be compensated for by proper nutrition.
Starting from the 12th week, foci of hematopoiesis can be detected in the fetus cobalt, which emphasizes its important role in hematopoietic processes. Subsequently from the 5th month intrauterine development When normoblastic hematopoiesis appears, cobalt in the fetus is detected in the liver. Varythropoiesis is also involved manganese, copper, selenium and other microelements.
Vitamin plays an important role in the regulation of erythropoiesis in the fetus and child. IN 12 and folic acid. Uplodacobalamin enters the liver through the placenta from the mother of the unborn child. In premature babies, the reserves of vitamin B 12 are 20-25 mcg. Daily requirement for a child, vitamin B 12 is 0.1 mcg. At the same time, 100 ml of mother's milk contains approximately 0.11 mcg of cobalamin. In the serum of a full-term newborn baby, the cobalamin content fluctuates within very wide limits and averages 590 ng/l. Subsequently, the concentration of vitamin B 12 in the blood decreases and by the age of six weeks reaches the norm characteristic of an adult (on average 440 ng/l). Daily requirement for folic acid in infants it ranges from 20 to 50 mcg. Folate content in breast milk mother averages 24 mcg/liter. Hence, breastfeeding completely provides the child with the necessary amount of not only vitamin B 12, but also folic acid.
In the antenatal period erythropoietin is formed first in yolk sac and then in the liver. Its synthesis in this organ, as in an adult, is regulated by oxygen tension in the tissues and increases sharply during hypoxia. At the same time, in the last trimester of pregnancy, the formation of erythropoietin in the fetus switches from the liver to the kidneys, which by the 40th day after the birth of the child become the main organ for the synthesis of erythropoietin. The action of erythropoietin in the fetus is also carried out through receptors that are located on the hematopoietic stem cells of the embryo. In addition, receptors for erythropoietin are found in the cells of the placenta, due to which the erythropoietic factor can be transferred from mother to fetus. The content of erythropoietin at the time of birth in both full-term and premature infants is significantly higher than in adults. At the same time, in premature infants its concentration varies widely. In the first two weeks after the birth of a child, the erythropoietin content decreases sharply (especially in premature infants) and even by the thirtieth day of life is lower than on average in adults. In the second month of a child’s life, a significant increase in the level of erythropoietin is observed, and its concentration approaches the figures characteristic of adults (5 – 35 IU/ml).
Features of leukopoiesis in a child
Immediately after the birth of a child, the number of leukocytes is very high and can reach 2010 9 /l and even more. This physiological leukocytosis is caused by the severe stress that the child feels when moving into a new environment during childbirth. Over the course of 1 day, the number of leukocytes may even increase and reach 3010 9 /l, which is associated with blood thickening. Then the number of leukocytes gradually decreases (in some children there is a slight increase between 4 and 9 days). IN infancy in different months the level of leukocytes fluctuates within a very wide range - from 6 to 1210 9 / l. The norms characteristic of an adult are established at the age of 9-10 years.
Leukocyte formula the newborn is very similar to that of adults, although there is a clear shift to the left due to the predominance of mainly band neutrophils. From the 2nd day, the number of neutrophils begins to fall, and the number of lymphocytes begins to increase. On days 5-7, the number of neutrophils and lymphocytes is 40-45% for each population. This is the so-called “first cross” of the relative content of neutrophils and lymphocytes. Subsequently, the number of neutrophils continues to decrease, and the number of lymphocytes increases at a slower pace, and by the 3rd–5th month the leukocyte formula is a mirror image for an adult. In this case, the number of neutrophils reaches 25-30%, and lymphocytes - 60-65%. This ratio of neutrophils and lymphocytes with slight fluctuations persists until 9-10 months of age, after which a systematic increase in the number of neutrophils and a fall in the number of leukocytes begins, which leads to the appearance of a “second cross” at the age of 5-6 years. After this, the number of lymphocytes gradually decreases, and the number of neutrophils increases and by the time of puberty becomes the same as in an adult. It should, however, be pointed out that among children of the same age, especially in the first days and months of life, there is an extreme variation in percentage both neutrophils and lymphocytes.
As for other white blood cells (eosinophils, basophils and monocytes), their relative number undergoes only minor fluctuations throughout the child’s development and differs little from the leukocyte formula of an adult
Note. At 5 days and 5 years, the content of neutrophils and lymphocytes in the peripheral blood is approximately the same (45%). How younger child, the more lymphocytes in the peripheral blood. The ratio of lymphocytes and neutrophils can be approximately determined by the formula:
up to 5 years: neutrophils (%) = 45-2(5-n), lymphocytes (%) = 45+2(5-n), where n is the number of years;
after 5 years: neutrophils (%) = 45+2(n-5), lymphocytes (%) = 45-2(n-5)
Platelets in a child
In the first hours of life, a newborn has blood platelets does not differ from the values typical for children more late age and for adults. At the same time, in different children it varies within a very wide range from 10010 9 /l to 40010 9 /l and on average is about 20010 9 /l. In the first hours after birth, the number of platelets increases, which may be due to blood thickening, and by the end of the day it decreases and reaches figures characteristic of a child who has just been born. By the end of the 2nd day, the platelet count increases again, approaching upper limit adult norms. However, by 7-10 days the number of blood platelets drops sharply and reaches 150-20010 9 /l. It is quite possible that platelets, like red blood cells, undergo massive destruction in the first week of life. In a child aged 14 days, the platelet count corresponds approximately to the value characteristic of a newborn. Subsequently, the platelet content changes slightly in one direction or another, not differing significantly from generally accepted norms for adults (150 - 40010 9 /l).
Features of hemostasis in children
All healthy full-term newborns in the first five days of life have a concomitant decrease in the level of procoagulants, basic physiological anticoagulants and plasminogen (Table 32). This ratio indicates a balance between the individual parts of the hemostasis system, although at a lower level. functional level than in subsequent age periods of life. Characteristic for early period adaptation, transient hypocoagulation is caused by the predominant hypoproduction of factors IX and X associated with K-hypovitaminosis, although the mechanism of their consumption during the process of blood coagulation is not excluded. It is noteworthy that in the first minutes and days of life, despite the background deficiency of vitamin K, in the plasma of healthy children the content of RFMC, products of enhanced enzymatic activity thrombin. In dynamics, this indicator quickly and progressively increases (compared to the norm by 4.2 times), reaching a maximum at 3–5 days. Subsequently, the amount of these intermediate products of fibrin formation decreases markedly and by the end of the neonatal period it becomes almost normal.
In children with chronic hypoxia, prematurity marks a later development of the balance of the participants hemostatic reactions(Table 33). These children, already before birth, during childbirth and immediately after birth, show a tendency to bleed, and this tendency increases in the first days of life (“ hemorrhagic disease newborns"). Some of them hemorrhagic syndrome combined with thrombosis due to the low activity of fibrinolysis and anticoagulants, the development of disseminated intravascular coagulation syndrome.
Lee-White clotting time: 5-12 min.
Bleeding duration: 1-2 min.
Hemogram analysis scheme
Erythrogram assessment: hemoglobin content, erythrocytes, color index value (c.p.), reticulocyte count, morphological features red blood cells
Decreased hemoglobin and red blood cells – anemia, increased – erythrocytosis
C.p. = (Hb in g/l x 0.3): 2 first digits of red blood cells
Example: Hb – 120g/l, red blood cells – 3.6*10.12/l, c.p.=(120 x 0.3):36 = 1.0
Norm: 0.8 – 1.1
Below 0.8 – hypochromia, above 1.1 – hyperchromia
Decrease in reticulocytes – reticulocytopenia – hyporegeneration
Increased reticulocytes – reticulocytosis – hyperregeneration
Anisocytosis – large variations in the size of erythrocytes, microcytosis – predominance of erythrocytes less than 7 microns in size, macrocytosis – predominance of erythrocytes more than 8 microns in size
Assessment of leukogram: number of leukocytes, ratio different forms leukocytes
A decrease in the number of leukocytes is leukopenia, an increase is leukocytosis.
A decrease in the number of eosinophils is eosinopenia, an increase is eosinophilia.
A decrease in the number of neutrophils is neutropenia, an increase is neutrophilia. If the content of young forms of granulocytes increases in the peripheral blood, they speak of a shift in the leukocyte formula to the left.
Decreased lymphocytes – lymphopenia, increased – lymphocytosis
A decrease in monocytes is monocytopenia, an increase is monocytosis.
A decrease in platelets is thrombocytopenia, an increase is thrombocytosis.
Example of hemogram evaluation.
The child is 5 days old.
Hb – 150 g/l, erythrocytes – 510 12 /l, reticulocytes – 0.5%, leukocytes – 1210 9 /l, eosinophils – 1%, band neutrophils – 4%, segmented neutrophils – 41%, lymphocytes – 45%, monocytes – 9%, platelets –10 9 /l, ESR – 5 mm/h
Grade. Erythrogram. C.p.=(150x0.3):50 = 0.9
Physiological erythrocytosis of the newborn, cp, reticulocyte content is normal.
Leukogram. Physiological leukocytosis newborn, the ratio of neutrophils and lymphocytes can be defined as the “first cross” at 5 days. The content of eosinophils and monocytes is within normal limits.
Conclusion. Normal hemogram healthy child in 5 days.
Hematopoiesis, or hematopoiesis, is the process of the emergence and subsequent maturation of blood cells in the so-called hematopoietic organs.
Embryonic hematopoiesis. For the first time, hematopoiesis is detected in a 19-day embryo in the blood islands of the yolk sac, which surround the developing embryo on all sides. The initial primitive cells—megaloblasts—appear. This short-term first period of hematopoiesis is called mesoblastic, or extraembryonic, hematopoiesis.
The second (hepatic) period begins after 6 weeks and reaches a maximum by the 5th month. Erythropoiesis is most clearly expressed and leuko- and thrombocytopoiesis is much weaker. Megaloblasts are gradually replaced by erythroblasts. At the 3-4th month of embryonic life, the spleen is included in hematopoiesis. Most active as hematopoietic organ it functions from the 5th to the 7th month of development. It carries out erythrocyte-, granulocyto- and megakaryo-cytopoiesis. Active lymphocytopoiesis occurs in the spleen later - from the end of the 7th month of intrauterine development.
By the time the child is born, hematopoiesis in the liver stops, and the spleen loses the function of producing red cells, granulocytes, megakaryocytes, while retaining the function of producing lymphocytes.
At the 4-5th month, the third (bone marrow) period of hematopoiesis begins, which gradually becomes decisive in the production of blood cells.
Thus, during the intrauterine life of the fetus, 3 periods of hematopoiesis are distinguished. However, its various stages are not strictly demarcated, but gradually replace each other.
According to the different periods of hematopoiesis - mesoblastic, hepatic and bone marrow - there are three different types of hemoglobin: embryonic (HbF), fetal (HbF) and adult hemoglobin (HbA). Fetal hemoglobin (HbH) is found only in the very early stages of embryonic development. Already at the 8-10th week of pregnancy, 90-95% of the fetus is HbF, and during the same period HbA begins to appear (5-10%). At birth, the amount of fetal hemoglobin varies from 45% to 90%. Gradually, HbF is replaced by HbA. By one year, 15% of HbF remains, and by 3 years, its amount should not exceed 2%. Types of hemoglobin differ in their amino acid composition.
Hematopoiesis in the extrauterine period. The main source of formation of all types of blood cells, except lymphocytes, in a newborn is the bone marrow. At this time, both flat and tubular bones are filled with red bone marrow. However, already from the first year of life, a partial transformation of red bone marrow into fatty (yellow) begins to appear, and by 12-15 years, as in adults, hematopoiesis remains in the bone marrow of only flat bones. Lymphocytes in extrauterine life are produced by the lymphatic system, which includes the lymph nodes, spleen, solitary follicles, group lymphatic follicles (Peyer's patches) of the intestine and other lymphoid formations.
Monocytes are formed in the reticuloendothelial system, which includes reticular cells of the bone marrow stroma, spleen, lymph nodes, stellate reticuloendothelial cells (Kupffer cells) of the liver and connective tissue histiocytes.
The neonatal period is characterized by functional lability and rapid bone marrow depletion. Under the influence of adverse effects: acute and chronic infections, severe anemia and leukemia, young children may experience a return to the embryonic type of hematopoiesis.
Regulation of hematopoiesis is carried out under the influence of nervous and humoral factors. The existence of a direct connection between the nervous system and the hematopoietic organs can be confirmed by the presence of bone marrow innervation.
The constancy of the morphological composition of blood is the result of a complex interaction between the processes of hematopoiesis, blood destruction and blood distribution.
Blood of a newborn. The total amount of blood in children is not a constant value and depends on body weight, time of umbilical cord ligation, and term of the child. On average, in a newborn, the blood volume is about 14.7% of his body weight, i.e. 140-150 ml per 1 kg of body weight, and in an adult - respectively 5.0-5.6%, or 50-70 ml/ kg.
In the peripheral blood of a healthy newborn, the content of hemoglobin (170-240 g/l) and erythrocytes (5-7-1012 / l) is increased, and the color index ranges from 0.9 to 1.3. From the very first hours after birth, the breakdown of red blood cells begins, which clinically causes the appearance of physiological jaundice.
Erythrocytes are polychromatophilic, have different sizes (anisocytosis), macrocytes predominate. The diameter of red blood cells in the first days of life is 7.9-8.2 microns (the norm is 7.2-7.5 microns). Reticulocytosis in the first days reaches 22-42°/00 (in adults and children over 1 month 6-8°/g)", nuclear forms of erythrocytes - normoblasts - are found. The minimum resistance (osmotic resistance) of erythrocytes is slightly lower, i.e. hemolysis occurs at high concentrations of NaCl - 0.48-0.52%, and the maximum - above 0.24-0.3%. In adults and schoolchildren and preschool age the minimum resistance is 0.44-0.48%, and the maximum is 0.28-0.36%.
The leukocyte formula in newborns has its own characteristics. The range of fluctuations in the total number of leukocytes is quite wide and amounts to 10-30-109 /l. During the first hours of life, their number increases slightly, and then falls and from the second week of life remains within the range of 10-12-109 / l.
Neutrophilia with a shift to the left to myelocytes, noted at birth (60-50%), begins to rapidly decrease, and the number of lymphocytes increases, and on the 5th-6th day of life the curves of the numbers of neutrophils and lymphocytes intersect (first crossover). From this time on, lymphocytosis up to 50-60% becomes normal for children in the first 5 years of life.
A large number of red blood cells, an increased content of hemoglobin in them, and the presence of a large number of young forms of red blood cells indicate enhanced hematopoiesis in newborns and the associated entry into the peripheral blood of young, not yet matured formed elements. These changes are caused by the fact that hormones circulating in the blood of a pregnant woman and stimulating her hematopoietic apparatus, passing into the body of the fetus, increase the functioning of its hematopoietic organs. After birth, the flow of these hormones into the child’s blood stops, as a result of which the amount of hemoglobin, red blood cells, and white blood cells quickly drops. In addition, increased hematopoiesis in newborns can be explained by the peculiarities of gas exchange - insufficient oxygen supply to the fetus. The state of anoxemia is characterized by an increase in the number of red blood cells, hemoglobin, and leukocytes. Eliminates after the baby is born oxygen starvation and red blood cell production decreases.
It is more difficult to explain the increase in the number of leukocytes and especially neutrophils in the first hours of extrauterine life. Perhaps the destruction of embryonic foci of hematopoiesis in the liver and spleen and the flow of young blood elements from them into the peripheral bloodstream are important. It is impossible to exclude the influence on hematopoiesis and resorption of interstitial hemorrhages.
Fluctuations on the part of the remaining elements of white blood are relatively small. The number of blood platelets during the neonatal period is on average 150-400-109 /l. Their anisocytosis with the presence of giant forms of plates is noted.
The duration of bleeding is not changed and according to the Duque method it is 2-4 minutes. Blood clotting time in newborns can be accelerated or normal, and in children with severe jaundice it can be prolonged. Clotting times depend on the technique used. The hematocrit number, which gives an idea of the percentage ratio between the formed elements of blood and plasma in the first days of life, is higher than in older children and is about 54%. Blood clot retraction, which characterizes the ability of platelets to tighten fibrin fibers in a clot, as a result of which the volume of the clot decreases and serum is squeezed out of it, is 0.3-0.5.
Blood of children of the first year of life. At this age, a gradual decrease in the number of red blood cells and hemoglobin levels continues. By the end of the 5-6th month, the lowest rates are observed. Hemoglobin decreases to 120-115 g/l, and the number of red blood cells - to 4.5-3.7-1012/l. In this case, the color index becomes less than 1. This phenomenon is physiological and is observed in all children. It is caused by a rapid increase in body weight, blood volume, insufficient intake of iron from food, and functional failure of the hematopoietic apparatus. Macrocytic anisocytosis gradually decreases and the diameter of erythrocytes becomes 7.2-7.5 microns. Polychromatophilia is not expressed after 2-3 months. The hematocrit value decreases in parallel with the decrease in the number of red blood cells and hemoglobin from 54% in the first weeks of life to 36% by the end of the 5-6th month.
The number of leukocytes ranges from 9-10-109 /l. Lymphocytes predominate in the leukocyte formula.
From the beginning of the second year of life until puberty, the morphological composition of the child’s peripheral blood gradually acquires features characteristic of adults. In the leukogram after 3-4 years, a tendency to a moderate increase in the number of neutrophils and a decrease in the number of lymphocytes is revealed. Between the fifth and sixth years of life, the 2nd crossover in the number of neutrophils and lymphocytes occurs in the direction of increasing the number of neutrophils.
It should be noted that in recent decades there has been a tendency towards a decrease in the number of leukocytes in healthy children and adults to 4.5-5.0109 / l. This may be due to changed environmental conditions.
