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 (fat). 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. Newborns are richer than adults lymphatic vessels and lymphoid elements with many young forms, the number of which gradually decreases after 4-5 years of life. Morphological and associated functional immaturity of the lymph nodes leads to their insufficient barrier function, and therefore, in children of the first months of life, infectious agents easily penetrate into 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 the age of 7-8, in connection with the completion of the development of the lymph nodes, the possibility of local protection against infectious agents appears. The response to the infection is an increase in the size of the lymph nodes, their pain on palpation. In healthy children, cervical (submandibular, anterior and posterior, occipital), axillary and inguinal lymph nodes are palpable. They are single, soft, mobile, not soldered to each other and to the surrounding tissue, they have a size from millet grain to lentil. Knowing the localization of the lymph nodes, it is possible to determine the direction of the spread of the infection and detect their change when 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 there is an increase in its mass. With the onset of puberty, age involution begins thymus. Spleen. One of the peripheral organs of immunity. It is the formation of lymphocytes, the destruction of erythrocytes and platelets, the accumulation of iron, the synthesis of immunoglobulins. The function of the spleen is to deposit blood. Macrophage systems (reticuloendothelial system) is the site of monocyte formation. Tonsils. Major lymphoid formations. In a newborn child, they are deep and small in size. Due to the structure and functional immaturity of the tonsils, children of the first year of life rarely suffer from tonsillitis. From 5-10 years old, an increase in the palatine tonsils is often observed, often combined with an increase in the nasopharyngeal tonsil and other lymphoid formations of the pharynx. From puberty begins reverse development. Lymphoid tissue is replaced by a connective one, the tonsils decrease in size, become more dense. The hematopoietic system of a child is characterized by pronounced functional instability, slight vulnerability, the possibility of a return 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 regeneration processes. These properties are explained by a large number of undifferentiated cells, which, under various stimuli, differentiate in the same way as in the period embryonic development. Blood. As the child grows, the blood undergoes a kind of change in terms of quality and quantitative composition. According to hematological parameters, all childhood subdivided into three periods: 1) newborns; 2) infancy; 3) after 1 year of life.
Newborn blood. For peripheral blood in this age period is characterized increased amount red blood cells and high hemoglobin levels. Blood contains 60-80% fetal hemoglobin. In premature babies, its level can be 80-90%. Adapted to the transport of oxygen 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 in the neonatal period exceeds 1 (up to 1.3). The following qualitative differences are characteristic of newborn erythrocytes: anisocytosis (different color 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 is equalized (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 by 55-60% (Fig. 55). The blood of a child over the age of 1 year. The number of erythrocytes and hemoglobin gradually increases, reticulocytes remain from young forms of erythrocytes, the number of which ranges from 2 to 5%. The color index is 0.85-0.95, the ESR is 4-10 mm/h. The total number of leukocytes decreases, and the nature of leukocyte formula: the number of lymphocytes gradually decreases, and neutrophils increase, and by 5-6 years their number is equalized, i.e. there is a second crossing of the curve of neutrophils (Fig. 55). In the future, 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. C o a l s y m e newborns and children of the 1st year of life has a number of features. During the neonatal period, coagulation is slow, 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, a delayed formation of thromboplastin is noted. In the first days of life, the activity of X and IV factors is reduced. In the neonatal period, there is also a slight decrease in the amount of I factor. The activity of the fibrinolytic system in children is often increased. In the future, as the liver matures, the activity of coagulation factors becomes sufficient and ensures the balance of the complex system of homeostasis.
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 students of the third year
medical faculty
Course - III semester
Faculty: medical
Lesson duration: 4 academic hours
Location: cardiology department of City Clinical Hospital No. 4
1. Topic of classes: Clinical methods of research of patients with diseases of the blood system. Morphological examination of peripheral blood, diagnostic value.
2. The value of studying this topic. The study of this topic gives an understanding of the methods of clinical examination of patients with a disease of the blood system, hematopoietic organs are extremely sensitive to various physiological and pathological effects on the body, a reflection of these is the picture of a peripheral blood test in normal conditions and in diseases of various body systems.
3. The 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 is normal and in diseases of various body systems.
As a result of studying this topic, the student should know:
The main complaints of patients with a disease of the blood system;
Ability to palpate peripheral lymph nodes
liver, spleen;
Indicators general analysis blood is normal;
Method 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 erythrocyte, ESR;
Leukocyte formula in pathology;
The concept of sternal puncture, trepanobiopsy;
The idea of a coagulogram;
Self-training for work.
As a result of self-training, the student should know:
Anatomical and physiological features of the blood system;
The main complaints of patients with a disease of the blood system, the mechanism of their occurrence;
General examination data of patients with a disease of the blood system;
Be able to palpate the peripheral lymph nodes, liver, spleen;
Be able to analyze the data of a general blood test, biochemical analysis blood.
Basic sections for repetition received by the student in related disciplines:
Anatomical and physiological features of the blood system, the scheme of hematopoietic sprouts;
Metabolism and exchange of iron;
Sections for repetition, received earlier in the discipline of propaedeutics of internal diseases:
Anamnesis and its sections;
Inspection and palpation of peripheral lymph nodes;
Percussion and palpation of the liver;
Palpation of the spleen;
Auscultation of the heart;
Investigation of the properties of the pulse;
Criteria for the norm of a peripheral blood test.
Questions for repetition and study in preparation for the lesson.
1. Anatomical and physiological features of the blood system, the scheme of hematopoietic germs;
3. The main complaints of patients with diseases of the blood system, the mechanism of their occurrence;
4. Significance of history to identify factors contributing to the development of anemia.
5. Significance of physical examination of patients with blood system.
6. Significance of quantitative and qualitative changes cellular composition blood:
a) erythrocytes;
b) change in the shape and color of erythrocytes;
c) change in color index;
d) the 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 at present the unitary theory of hematopoiesis is generally accepted, on the basis of which the scheme of hematopoiesis was developed (I. L. Chertkov and A. I. Vorobyov, 1973).
- unitary theory (A. A. Maksimov, 1909) - all blood cells develop from a single stem cell precursor;
- the dualistic theory provides for two sources of hematopoiesis, for myeloid and lymphoid;
- polyphyletic theory provides for each shaped element its own source of development.
In the process of gradual differentiation of stem cells into mature blood cells, in each row of hematopoiesis, intermediate types cells that in the scheme of hematopoiesis constitute classes of cells. In total, 6 classes of cells are distinguished in the hematopoietic scheme:
1st class - stem cells;
Grade 2 - semi-stem cells;
class 3 - unipotent cells;
class 4 - blast cells;
Grade 5 - maturing cells;
Grade 6 - mature shaped elements.
Morphological and functional characteristic cells of various classes of hematopoietic scheme.
1 class- stem pluripotent cell capable of maintaining its population. In morphology, it corresponds to a small lymphocyte, is pluripotent, that is, capable of differentiating into any blood cell. 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 population of stem cells 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 the morphology of a small lymphocyte and is a stem cell. Stem cells divide rarely (once every six months), 80% of stem cells are at rest and only 20% are in mitosis and subsequent differentiation. During proliferation, each stem cell forms a group or a clone of cells, and therefore stem cells in the literature are often called clone-forming units - CFU.
Grade 2- semi-stem, limitedly pluripotent (or partially committed) cells - precursors of myelopoiesis and lymphopoiesis. They have the morphology of a small lymphocyte. Each of them gives a clone of cells, but only myeloid or lymphoid. They divide more often (after 3-4 weeks) and also maintain the size of their population.
3rd grade- unipotent poetin-sensitive cells - the precursors 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 retain the population size. this class. The frequency of division of these cells and the ability to differentiate further depends on the content of special biologically active substances in the blood. 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 potential for development is different.
4th grade- blast (young) cells or blasts (erythroblasts, lymphoblasts, and so on). 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 a large number free ribosomes. They often divide, but the daughter cells all take the path of further differentiation. According to cytochemical properties, blasts of different hematopoietic lines can be identified.
5th grade- a class of maturing cells characteristic of their hematopoietic series. In this class, there may be several varieties of transitional cells - from one (prolymphocyte, promonocyte), to five in the erythrocyte row. Some maturing cells may enter the peripheral blood in small numbers (eg, reticulocytes, juvenile and stab granulocytes).
6th grade- mature blood cells. However, it should be noted that only erythrocytes, platelets and segmented granulocytes are mature end differentiated cells or their fragments. Monocytes are not terminally differentiated cells. Leaving the bloodstream, they differentiate into end cells - macrophages. Lymphocytes, when they encounter antigens, turn into blasts and divide again.
The set of cells that make up the line of differentiation of a stem cell into a certain uniform element form its differon or histological series. For example, erythrocyte differon is:
- stem cell;
- semi-stem cell, the precursor of myelopoiesis;
- unipotent erythropoietin-responsive cell;
- erythroblast;
- maturing cells - pronormocyte, basophilic normocyte, polychromatophilic normocyte, oxyphilic normocyte, reticulocyte, erythrocyte.
In the process of maturation of erythrocytes in the 5th grade, the following occurs: the synthesis and accumulation of hemoglobin, the reduction of organelles, and the 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. With severe blood loss, the replenishment of erythrocytes is ensured not only by increased division of maturing cells, but also by cells of 4, 3, 2, and even 1 classes. A heteroplastic type of hematopoiesis, which precedes reparative blood regeneration. Blood is a liquid (liquid tissue of mesodermal origin), red, weakly 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 a variety of functions. The most important of them are the following:
Transport nutrients from digestive tract to tissues, places of reserve stocks 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; storage of oxygen (respiratory function);
Transport of hormones from glands internal secretion to the 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 alien substances (humoral immunity);
Blood clotting that prevents blood loss;
Thermoregulatory function - redistribution of heat between organs, regulation of heat transfer through the skin;
Mechanical function - giving turgor tension to the organs due to the rush of blood to them; ensuring ultrafiltration in the capillaries of the capsules of the nephron of the kidneys, etc.;
homeostatic function - maintaining constancy 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 body tissues. Of the total volume of blood, about half circulates throughout the body. The remaining half is retained in the dilated capillaries of some organs and is called deposited. Organs in which blood is deposited are called blood depots.
Diagram of hematopoiesis
(I. L. Chertkov and A. I. Vorobyov, 1973).
|
Spleen. Holds in its lacunae - processes of capillaries up to 16% of all blood. This blood is practically excluded from circulation and does not mix with the circulating blood. With the contraction of the smooth muscles of the spleen, the lacunae are compressed, and the blood enters the general channel.
Liver. Holds up to 20% of the blood volume. The liver acts as a blood depot by contracting the sphincters of the hepatic veins, through which blood flows away from the liver. Then more blood enters the liver than flows out. The capillaries of the liver expand, the blood flow in it slows down. However, the blood deposited in the liver is not completely switched off from the bloodstream.
Subcutaneous tissue. Deposits up to 10% of blood. IN blood capillaries skin has anastomoses. Part of the capillaries expands, fills with blood, and the blood flow occurs through shortened paths (shunts).
Lungs can also be attributed to the organs that deposit blood. The volume of the vascular bed of the lungs is also not constant, it depends on the ventilation of the alveoli, the amount of blood pressure in them and on the blood supply to the vessels of the systemic circulation.
Thus, the deposited blood is switched off from the circulation and basically 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 meaning of the deposited blood is as follows. When the body is in a state of physiological rest, its organs and tissues do not need an 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, inhalation of air with a high content of carbon dioxide - that is, in all cases when required, it will increase the delivery of oxygen and nutrients to organs. The mechanisms of blood redistribution between the deposited and circulating blood involve the vegetative 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 bloodstream, the blood leaves the depot. In case of blood loss, the volume of blood is restored, first of all, due to the transition tissue fluid into the blood, and then the deposited blood enters the bloodstream. As a result, the volume of plasma is restored much faster than the number of formed elements. With an increase in blood volume (for example, when a large amount of blood substitutes is introduced or when a large amount of water is drunk), part of the liquid is quickly excreted by the kidneys, but most of it passes into the tissues, and then gradually excreted from the body. Thus, the volume of blood filling the vascular bed is restored.
©2015-2019 site
All rights belong to their authors. This site does not claim authorship, but provides free use.
Page creation date: 2016-02-16
Anatomical and physiological features of blood and lymphatic system
Hematopoiesis, or hematopoiesis, is the processes of the emergence and subsequent maturation of blood cells in the so-called hematopoietic organs.
During the intrauterine life of the fetus, 3 periods of hematopoiesis are distinguished. The stages are not strictly delimited, but gradually replace each other. By the time the child is born, hematopoiesis stops in the liver, and the spleen loses the function of forming red cells, granulocytes, megakaryocytes, while retaining the function of forming 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 the year, 15% of the fetal remains, and by the age of 3, its amount should not exceed 2%.
newborn blood. The total amount of blood in children is not a constant value and depends on body weight, the time of ligation of the umbilical cord, and the child's full term. On average, in a newborn, the volume of blood is about 14.7% of its body weight, and in an adult, respectively, 5.0-5.6%.
in peripheral blood healthy newborn the content of hemoglobin and erythrocytes is increased, and the color index ranges from 0.9 to 1.3. From the very first hours after birth, the breakdown of erythrocytes begins, which clinically causes the appearance of physiological jaundice.
The leukocyte formula in newborns has features. Swing range total number leukocyte count is quite wide. During the first hours of life, their number increases somewhat, and then falls. A large number of erythrocytes, an increased content of hemoglobin in them, the presence of a large number of young forms of erythrocytes indicate increased hematopoiesis in newborns and the associated entry into the peripheral blood of young, not yet mature formed elements. These changes are caused by the fact that the hormones circulating in the blood of a pregnant woman and stimulating her hematopoietic apparatus, passing into the body of the fetus, increase the work of its hematopoietic organs. After birth, the flow of these hormones into the blood of the child stops, as a result of which the amount of hemoglobin, erythrocytes, and leukocytes rapidly decreases. In addition, increased hematopoiesis in newborns can be explained by the peculiarities of gas exchange - insufficient supply of oxygen to the fetus.
Blood of children of the first year of life. Continues at this age gradual decline erythrocyte count and hemoglobin level. By the end of the 5-6th month, the most low rates. 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 with food, functional failure of the hematopoietic apparatus.
From the beginning of the second year of life before puberty, the morphological composition of the peripheral blood of the child gradually acquires the 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 year of life, the 2nd crossover of the number of neutrophils and lymphocytes occurs in the direction of an increase in the number of neutrophils. It should be noted that in recent decades there has been a trend towards a decrease in the number of leukocytes in healthy children and adults.
Blood vessels in a newborn is wider than in an adult. Their lumen gradually increases, but more slowly than the volume of the heart. The process of blood circulation in children is more intense than in adults. Pulse the child has a rapid: 120-140 beats per minute. There are 3.5-4 heart beats for one cycle of "inhale-exhale". 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 in different children in different ways, depending on weight, temperament, etc.
The blood of a newborn contains a large number of erythrocytes and leukocytes, hemoglobin increased. But gradually during the year their number decreases to the norm. Because the hematopoietic system babies are very sensitive to different kind external and internal harmful effects, children of the first year of life are more likely than older children to develop anemia.
The formation of hematopoiesis in the antenatal and postnatal periods.
The process of intrauterine hematopoiesis includes 3 stages:
1. Yolk stage(mesoblastic, angioblastic) . It starts from the 3rd 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. It starts from the 6th week and continues almost until birth. Initially, both megaloblastic and normoblastic erythropoiesis occurs 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 starts from the end of the 3rd month and continues in postnatal ontogenesis. In the bone marrow of all bones (starting with the clavicle), stem cells produce erythropoiesis of the normoblastic type, granulocyto-, monocyto-, megakaryocytosis and lymphopoiesis. The role of organs of lymphopoiesis during this period is performed by the spleen, thymus, lymph nodes, palatine tonsils and Peyer's patches.
In postnatal life, the main hematopoietic organ becomes the bone marrow. It contains the bulk of hematopoietic stem cells and the formation of all blood cells. The intensity of hematopoiesis in other organs decreases rapidly after birth.
Features of hematopoiesis in a child.
Features of erythropoiesis in a child.
In a newborn child, HbF predominates, it has a high affinity for oxygen and easily gives it to the tissues. Starting from the first weeks of postnatal life, there is a sharp increase in HbA synthesis, while the formation of HbF decreases sharply (approximately 3% per week). By the age of six months, the content of HbA in the blood is 95-98% (that is, as in an adult), while the concentration of HbF does not exceed 3%.
In a newborn child, the number of erythrocytes in the peripheral blood reaches 710 12 / l, and the hemoglobin level - 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 erythropoietins in its blood. However, after birth, the child develops hyperoxia (since external respiration), 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 erythrocytes and the level of hemoglobin even increase, mainly due to thickening of the blood, but by the end of the first day, the number of erythrocytes begins to fall. In the future, the content of erythrocytes decreases on the 5-7th, and hemoglobin - on the 10th day of a child's life after massive hemolysis of erythrocytes, accompanied by the so-called transient hyperbilirubinemia of newborns, manifested in some children by "physiological jaundice". So rapid decline The number of erythrocytes in a newborn child is explained by a very short period of life of the fetal red blood cells (the child is born with them) - only 10-14 days - and a very high degree of their destruction, 5-7 times higher than the intensity of erythrocyte death in an adult. However, during these periods, fast education new erythrocytes.
Number of reticulocytes in full-term newborns, it varies widely and ranges from 0.8 to 4%. Moreover, isolated normoblasts can 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 erythrocytes 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 infancy" and are rarely accompanied by 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 baby compared with adults, the intensity of erythropoiesis is significantly reduced, which is associated with low education during this period, the main factor of erythropoiesis - erythropoietin. In the future, the content of erythrocytes and hemoglobin may increase or decrease slightly, 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. By this time, there are gender differences in the standards of red blood.
Particularly sharp individual variations in the number of erythrocytes and hemoglobin levels are observed in age periods from 1 to 2 years, from 5 to 7 and from 12 to 15 years, which, apparently, is associated with significant variations in the growth rate of children.
The erythrocytes of a newborn differ significantly in size and shape: from the first hours of life until the 5-7th day, macrocytosis and poikilocytosis are noted in children. Many young immature are revealed in the blood large forms erythrocytes. During the first hours of life, the child has sharp rise 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.
Erythrocytes of a fetus and a newborn child, compared with adult erythrocytes, are more sensitive to oxidants, which can lead to membrane structure disruption, 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 the 1st week of a child's life, the function of the antioxidant system increases, the activity of such enzymes as glutathione peroxidase, glutathione catalase, and 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.
For fetal erythropoiesis and especially developing child influenced by the same factors as in adults. In particular, iron in the body of the fetus accumulates 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. These mechanisms include more high ability fetal transferrin to be saturated with iron, as well as a slow consumption of ferritin due to low activity of xanthine oxidase.
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 a reverse transfer to the placenta and to the mother. By the time of the birth of a child, the total supply of iron in his body is 75 mg / kg of body weight. This value is constant in both full-term and premature babies.
The child in gastrointestinal tract iron absorption is much more intense than in adults. So, in children of the first months of life, who are on breastfeeding, up to 57% of the iron consumed can be absorbed, at the age of 4-5 months - up to 40-50%, and at 7-10 years old - up to 8-18%. In an adult, on average, from 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 the total content of hemoglobin 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 youth. With the onset of menstruation in girls, the need for iron increases significantly, and it can only be compensated by good nutrition.
Starting from the 12th week, in the fetus in the foci of hematopoiesis, cobalt, which emphasizes its important role in the processes of hematopoiesis. Further from the 5th month prenatal development when normoblastic hematopoiesis appears, cobalt in the fetus is detected in the liver. Varithropoiesis is also involved manganese, copper, selenium and other micronutrients.
An important role in the regulation of erythropoiesis in the fetus and child is played by vitamin IN 12 and folic acid. Uplodacobalamin enters the liver through the placenta from the mother of the unborn child. In term babies, the reserves of vitamin B 12 are 20-25 mcg. daily requirement child in vitamin B 12 is 0.1 mcg. At the same time, 100 ml of mother's milk contains approximately 0.11 micrograms of cobalamin. In the serum of a full-term newborn, the content of cobalamin varies within very wide limits and averages 590 ng/l. In the future, the concentration of vitamin B 12 in the blood decreases and by the age of six weeks reaches the norm characteristic of an adult (an average of 440 ng / l). daily requirement for folic acid in infants ranges from 20 to 50 mcg. The content of folate in breast milk mothers averages 24 mcg / liter. Hence, breastfeeding fully provides the child with the necessary amount of not only vitamin B 12, but also folic acid.
In the antenatal period erythropoietin first formed 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, erythropoietin receptors are found in placental cells, so that erythropoietic factor can be transferred from mother to fetus. The content of erythropoietin at the time of birth in both full-term and premature children is significantly higher than in adults. At the same time, in premature babies, its concentration varies widely. In the first two weeks after the birth of a child, the content of erythropoietin decreases sharply (especially in preterm infants) and even by the thirtieth day of life is lower than the 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 due to the severe stress that the child feels when moving into a new environment during childbirth. During 1 day, the number of leukocytes can even increase and reach 3010 9 / l, which is associated with thickening of the blood. Then gradually there is a decrease in the number of leukocytes (in some children there is a slight rise between 4 and 9 days). IN infancy in different months, the level of leukocytes fluctuates over a very wide range - from 6 to 1210 9 / l. The norms typical for an adult are set at the age of 9-10 years.
Leukocyte formula of the newborn is very similar to that in adults, although there is a clear shift to the left due to the predominance, mainly, of stab neutrophils. From the 2nd day, the number of neutrophils begins to fall, and lymphocytes begin to increase. On days 5-7, the number of neutrophils and lymphocytes is 40-45% for each population. This is the so-called "first crossover" of the relative content of neutrophils and lymphocytes. In the future, the number of neutrophils continues to decrease, and the number of lymphocytes increases at a slower pace, and by the 3-5th 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 the age of 9-10 months, after which a systematic increase in the number of neutrophils and a decrease in the number of leukocytes begin, which leads to the appearance of a "second decussation" at the age of 5-6 years. After that, 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. However, it should be pointed out that in children of the same age, especially in the first days and months of life, there is an extraordinary variation in percentage both neutrophils and lymphocytes.
As for other white blood cells (eosinophils, basophils and monocytes), their relative number undergoes only slight fluctuations throughout the development of the child and differs little from the indicators of 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 a newborn in the first hours of life, the content platelets does not differ from the values characteristic of children more than late age and for adults. At the same time, in different children it varies over 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 thickening of the blood, and by the end of the day it decreases and reaches numbers characteristic of a child who has just been born. By the end of the 2nd day, the number of platelets increases again, approaching upper bound adult standards. However, by the 7-10th day, the number of platelets drops sharply and reaches 150-20010 9 /l. It is quite possible that platelets, like erythrocytes, undergo massive destruction in the first week of life. In a child at the age of 14 days, the number of platelets corresponds approximately to the value characteristic of a newborn. In the future, the content of platelets changes slightly in one direction or another, not differing significantly from the generally accepted norms for adults (150 - 40010 9 / l).
Features of hemostasis in children
All healthy full-term newborns of the first five days of life have an associated decrease in the level of procoagulants, the main physiological anticoagulants and plasminogen (Table 32). Such a ratio indicates a balance between the individual links of the hemostasis system, although at a lower level. functional level than in later ages. Characteristic for early period adaptation, transient hypocoagulation is due to the predominant hypoproduction of factors IX and X associated with K-hypovitaminosis, although the mechanism of their consumption in the process of blood clotting 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 RFBA, products of enhanced enzymatic activity thrombin. In dynamics, this indicator rapidly and progressively increases (by 4.2 times compared to the norm), reaching a maximum by 3-5 days. Subsequently, the amount of these intermediate products of fibrin formation decreases markedly and by the end of the neonatal period becomes almost normal.
In children with chronic hypoxia, prematurity is marked by a later formation of the balance of participants hemostatic reactions(Table 33). These children already before childbirth, 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 low activity of fibrinolysis and anticoagulants, the development of DIC.
Clotting time according to Lee-White: 5-12 min.
Bleeding duration: 1-2 min.
Hemogram analysis scheme
Assessment of erythrogram: hemoglobin content, erythrocytes, color index value (c.p.), reticulocyte count, morphological features erythrocytes.
Decrease in hemoglobin and erythrocytes - anemia, increase - erythrocytosis
C.p. \u003d (Hb in g / l x 0.3): 2 first digits of erythrocytes
Example: Hb - 120g / l, erythrocytes - 3.6 * 10.12 / l, cp = (120 x 0.3): 36 = 1.0
Norm: 0.8 - 1.1
Below 0.8 - hypochromia, above 1.1 - hyperchromia
Decreased reticulocytes - reticulocytopenia - hyporegeneration
Increased reticulocytes - reticulocytosis - hyperregeneration
Anisocytosis - large variations in the size of red blood cells, microcytosis - the predominance of red blood cells smaller than 7 microns, macrocytosis - the predominance of red blood cells larger than 8 microns
Leukogram evaluation: white blood cell count, ratio different forms leukocytes
A decrease in the number of leukocytes is leukopenia, an increase is leukocytosis.
A decrease in the number of eosinophils - eosinopenia, an increase - 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 of the leukocyte formula to the left.
Decrease in lymphocytes - lymphopenia, increase - lymphocytosis
Decrease in monocytes - monocytopenia, increase - monocytosis
A decrease in platelets is thrombocytopenia, an increase is thrombocytosis.
An example of a 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%, stab neutrophils - 4%, segmented neutrophils - 41%, lymphocytes - 45%, monocytes - 9%, platelets -10 9 / l, ESR - 5 mm / h
Grade. Erythrogram. Ts.p. \u003d (150x0.3): 50 \u003d 0.9
Physiological erythrocytosis of the newborn, c.p., the content of reticulocytes is normal.
Leukogram. Physiological leukocytosis newborn, the ratio of neutrophils and lymphocytes can be defined as the "first crossover" at 5 days. The content of eosinophils, monocytes is within normal limits.
Conclusion. Normal hemogram healthy child in 5 days.
Hematopoiesis, or hematopoiesis, is the processes of the emergence and subsequent maturation of blood cells in the so-called hematopoietic organs.
Embryonic hematopoiesis. For the first time, hematopoiesis is found in a 19-day-old embryo in the blood islands of the yolk sac, which surround the developing embryo from all sides. Primitive primitive cells appear - megaloblasts. 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 are 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 stops in the liver, and the spleen loses the function of forming red cells, granulocytes, megakaryocytes, while retaining the function of forming 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 period of intrauterine life of the fetus, 3 periods of hematopoiesis are distinguished. However, its various stages are not strictly delimited, 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 (HbP), fetal (HbF) and adult hemoglobin (HbA). Embryonic hemoglobin (HHP) is found only in the very early stages of embryonic development. Already at the 8-10th week of pregnancy, the fetus has 90-95% HbF, and HbA (5-10%) begins to appear in the same period. At birth, the amount of fetal hemoglobin varies from 45% to 90%. Gradually, HbF is replaced by HbA. By the year, 15% HbF remains, and by 3 years, its amount should not exceed 2%. Types of hemoglobin differ in amino acid composition.
Hematopoiesis in the extrauterine period. The main source of formation of all types of blood cells, except for 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 the red bone marrow into fatty (yellow) begins to be outlined, and by the age of 12-15, as in adults, hematopoiesis is preserved 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, including reticular cells of the stroma of the bone marrow, 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 depletion of the bone marrow. Under the influence of adverse effects: acute and chronic infections, severe anemia and leukemia - in young children, a return to the embryonic type of hematopoiesis may occur.
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 the blood is the result of a complex interaction between the processes of hematopoiesis, blood destruction and blood distribution.
Newborn blood. The total amount of blood in children is not a constant value and depends on body weight, the time of ligation of the umbilical cord, and the child's full term. On average, in a newborn, the volume of blood is about 14.7% of its 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 erythrocytes begins, which clinically causes the appearance of physiological jaundice.
Erythrocytes are polychromatophilic, have a different size (anisocytosis), macrocytes predominate. The diameter of erythrocytes in the first days of life is 7.9-8.2 microns (at a rate of 7.2-7.5 microns). Reticulocytosis in the first days reaches 22-42 ° / 00 (in adults and children older than 1 month 6-8 ° / w), "there are nuclear forms of erythrocytes - normoblasts. 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%. preschool age the minimum resistance is 0.44-0.48%, and the maximum is 0.28-0.36%.
The leukocyte formula in newborns has features. The range of fluctuations in the total number of leukocytes is quite wide and is 10-30-109 / l. During the first hours of life, their number increases somewhat, and then falls, and from the second week of life it remains within 10-12-109 / l.
Neutrophilia with a shift to the left to myelocytes, noted at birth (60-50%), begins to decline rapidly, and the number of lymphocytes increases, and on the 5th-6th day of life, the curves for the number of neutrophils and lymphocytes intersect (first crossover). Since that time, lymphocytosis up to 50-60% has become a normal phenomenon for children of the first 5 years of life.
A large number of erythrocytes, an increased content of hemoglobin in them, the presence of a large number of young forms of erythrocytes indicate increased hematopoiesis in newborns and the associated entry into the peripheral blood of young, not yet mature formed elements. These changes are caused by the fact that the hormones circulating in the blood of a pregnant woman and stimulating her hematopoietic apparatus, passing into the body of the fetus, increase the work of its hematopoietic organs. After birth, the flow of these hormones into the blood of the child stops, as a result of which the amount of hemoglobin, erythrocytes, and leukocytes rapidly decreases. In addition, increased hematopoiesis in newborns can be explained by the peculiarities of gas exchange - insufficient supply of oxygen to the fetus. The state of anoxemia is characterized by an increase in the number of erythrocytes, hemoglobin, and leukocytes. Removed after the birth of the child oxygen starvation and erythrocyte 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, spleen and the flow of young blood elements from them into the peripheral bloodstream is important. It is impossible to exclude the influence on hematopoiesis and resorption of interstitial hemorrhages.
Fluctuations from other elements of white blood are rather small. The number of platelets in the neonatal period averages 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 Duke method is 2-4 minutes. Blood clotting time in newborns may be accelerated or normal, and prolonged in children with severe jaundice. Clotting times vary depending on the technique used. The hematocrit number, which gives an idea of the percentage ratio between blood cells and plasma in the first days of life, is higher than in older children, and is about 54%. The retraction of a blood clot, 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 is reduced to 120-115 g / l, and the number of red blood cells - up 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 with food, functional failure of the hematopoietic apparatus. Macrocytic anisocytosis gradually decreases and the diameter of erythrocytes becomes equal to 7.2-7.5 microns. Polychromatophilia after 2-3 months is not expressed. The hematocrit value decreases in parallel with the decrease in the number of erythrocytes 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. The leukocyte formula is dominated by lymphocytes.
From the beginning of the second year of life to the pubertal period, the morphological composition of the peripheral blood of the child gradually acquires the 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 year of life, the 2nd crossover of the number of neutrophils and lymphocytes occurs in the direction of an increase in the number of neutrophils.
It should be noted that in recent decades there has been a tendency to reduce the number of leukocytes in healthy children and adults to 4.5-5.0109 / l. Perhaps this is due to changing environmental conditions.
