Age features of the respiratory system in newborns and children. Age features of human breathing

In the seventy years that, on average, elapse between birth and death, a person goes through many stages of development. In the process of growth, both boys and girls follow a clear developmental pattern various ways breathing. For example, in junior and middle school age, between the ages of seven and fourteen, boys have more developed lungs than girls of the same age. It is characteristic that in girls of 9-11 years the respiratory volume of the lungs is 10 percent less than in boys of the same age group. By the age of twelve, this difference reaches 20 percent. It exists until the age of fourteen.

Doctors explain this difference in the physical development of boys and girls primarily by the influence of sex hormones secreted by the endocrine glands, especially testosterone, the male sex hormone, which plays a major role in muscle development and, accordingly, an increase in the respiratory volume of the lungs in boys.

Does location affect lung capacity?

Studies have been conducted to compare the lung activity of children of the same age group living in different regions of Japan. The young participants in the study were recruited in two different areas - one group of children was from Tokyo, and the other was from central Japan, from Nagano Prefecture. The Tokyo group represented students from major cities, while the Nagano group represented students from the countryside.

As a result of a study of pupils of primary school age, boys aged seven to eleven, it turned out that the average respiratory volume of residents of rural areas is greater than that of children who grew up in an urban area. But when it comes to boys aged twelve and over, the situation is in favor of the young representatives from Tokyo: their tidal volume significantly exceeds that of their peers from the countryside. As for girls, their development of respiratory volume of the lungs has the same trends in the same age groups.

This study shows that the more developed respiratory system of boys from rural areas under the age of eleven years is determined by better general physical development, which, in turn, is explained by the fact that from the age of six or even earlier these children have to engage in heavy physical labor associated with farm work. And the better functioning of the respiratory system of urban boys aged 12-14 is due to the fact that boys in urban areas reach puberty earlier than in rural areas.

The same explanation is offered for the fact that when studying the respiratory functions of young men aged 14-17 from the same regions, no significant differences were found. That is, in both urban and rural areas, students reach puberty by this age.

How lung capacity changes with age

The studies described above, as well as similar studies in which people who have already reached maturity took part, show that the total respiratory volume of a person's lungs constantly increases up to 18-20 years. However, in subsequent years, this volume gradually decreases. Taking the average value at the age of 18-20 years as 100 percent, the change in VC per square meter of body surface can be shown as follows:

95.9 aged 20-23,
90.17 aged 32-34,
86.07 aged 41-43,
81.86 aged 51-53,
76.36 aged 56-60,
67.38 aged 61-65,
60.48 aged 71-75
56.24 at the age of 75-80 years.

Similarly, taking the average at age 18-20 as 100 percent, the change in maximum ventilation per square meter of body surface can be shown as:

91.64 aged 20-23,
86.39 aged 32-34,
82.52 aged 41-43,
73.91 aged 51-53,
66.79 aged 56-60,
63.67 aged 61-65,
49.44 aged 71-75
41.7 at the age of 75-80 years.

Based on these data, we can say that the human respiratory system functions best in youth, between 18 and 20 years.

"Respiratory old age" and how to prevent it

The results of the studies mentioned above show that in a person aged sixty years and older, the respiratory system functions worse than in a child of nine years old. Signs of "respiratory old age" in men appear at the age of approximately 50 years. In women, they appear ten years earlier than in men. The occurrence of such symptoms sometimes coincides with signs of aging of muscle tissues. Therefore, it is very important for middle-aged people to master techniques that maintain a stable tidal volume for as long as possible.

The most effective way to prevent the acceleration of the aging process, a person will master by learning to maintain the rhythm and regularity of the respiratory cycle, and thus he will be able to rejuvenate himself. Exercises of this kind are more effective for rejuvenation than other physical exercises on outdoors, such as jogging or various types of athletics, which many people do today, trying to get rid of sticky weight.

Breath - a necessary physiological process of constant exchange of gases between the body and the external environment. As a result of respiration, oxygen enters the body, which is used by each cell of the body in oxidation reactions, which is the basis for the exchange of speech and energy. During these reactions, carbon dioxide is released, the excess of which must be constantly excreted from the body. Without access to oxygen and removal of carbon dioxide, life can last only a few minutes.

The concept of respiration includes the following processes:

external respiration- exchange of gases between the external environment and the lungs (pulmonary ventilation);

The exchange of gases in the lungs between the air of the lungs and the blood of the capillaries, densely permeate the alveoli of the lungs (lung breathing);

transport of gases by the blood(transfer of oxygen from the lungs to the tissues, and carbon dioxide from the tissues to the lungs);

The exchange of gases in tissues;

internal or tissue respiration- the use of oxygen by tissues (internal respiration at the level of cell mitochondria).

The first four stages relate to external respiration, and the fifth stage - to interstitial respiration, which occurs at the biochemical level.

The human respiratory system consists of the following organs :

Airways, which include the nasal cavity, nasopharynx, larynx, trachea and bronchi of different diameters;

Lungs, consisting of the smallest air channels (bronchioles), air bubbles - alveoli, tightly braided with blood capillaries of the pulmonary circulation

The musculoskeletal system of the chest, which provides respiratory movements and includes the ribs, intercostal muscles and the diaphragm (the membrane between the chest cavity and the abdominal cavity). The structure and performance of the organs of the respiratory system change with age, which determines certain features of the breathing of people of different ages.

In addition to the described function, the respiratory system is associated with:

2. the function of protecting the body from the ingress of dust and microorganisms (mucus secreted by the goblet cells of the ciliated epithelium and the ciliated epithelium of the respiratory tract itself, relieving us of protective mucus along with dust and microorganisms);

3. protective reflexes of sneezing and coughing;

4. the function of approaching the temperature of the inhaled air to the temperature of the internal environment of the body (abundant blood supply to the mucous membrane of the upper respiratory tract);

5. the function of humidifying the inhaled air;

6. the function of removing metabolic products (carbon dioxide, water vapor, etc.);

7. the function of distinguishing odors (olfactory receptors).

I would especially like to note the importance of nasal breathing. When breathing through the nose, cells of a special neuroepithelium associated with the brain are irritated. Irritation of these cells contributes to the development of the child's brain (therefore nasal breathing is so important for children and such obstacles as polyps and adenoids need to be removed), affects our performance, mood, and behavior. To be convinced of this, it is enough to remember your feelings during a runny nose. For symmetrical stimulation of the neuroepithelium of the right and left half of the nasal cavity, it is also necessary to avoid curvature of the nasal septum, which easily occurs in children due to mechanical trauma to the nose.

3.9.1. Morphofunctional transformations of the respiratory tract and lungs

In newborns, the nasal conchas are relatively thick, and the nasal passages are poorly developed. They intensively develop up to 10 years, finally formed by the age of 20. The integuments are tender, well supplied with blood and swell easily. Therefore, in the first years of life, children often have difficulty breathing.

The larynx in newborns is short, wide, located higher than in adults. It develops rapidly during 4 years of life and during puberty. At the age of 6-7 years, sexual differences appear in children. In boys, the larynx is larger, at the age of 10-12 a protrusion (Adam's apple) appears, changes occur in the structure of the vocal cords and the voice mutates. The mucous membrane of the larynx at this age is especially susceptible to irritants, microorganisms, inflammatory reactions, it quickly swells, so the voice often changes or disappears.

The trachea and bronchi in newborns are short, as a result of which the infection quickly penetrates the lungs. Their mucous membranes are thin, delicate and quickly affected by infection.

The lungs of the fetus are dense and collapsed. They straighten out after the first breath and are still undeveloped in newborns. The formation of alveolar passages ends by 7–9 years, alveoli - 12–15 years, lung tissue - 15–25 years. The increase in lung capacity occurs before the age of 25.

The fetus receives O2 and removes CO2 through the placental circulation. However, he already has rhythmic respiratory movements with a frequency of 38-70 cycles per minute. These movements are reduced to a slight expansion of the chest, which is replaced by a longer decline and an even longer pause. In the lungs, there is a slight negative pressure in the interpleural fissure due to the discharge of the outer pleura and an increase in the interpleural fissure. The respiratory movements of the fetus occur with a closed glottis, so amniotic fluid does not enter the respiratory tract.

Breathing movements help to increase the speed of blood movement through the vessels and its flow to the heart, which improves the blood supply to the fetus. They are a kind of training for the function that the body will need after birth.

Birth causes abrupt changes in the state of the respiratory center located in the medulla oblongata, leading to the onset of ventilation. The first breath occurs, as a rule, after 15-70 seconds. after birth.

The reasons for the first breath are:

· excess accumulation CO2 and depletion of blood O2 after the cessation of placental circulation;

change in the conditions of existence;

Irritation of skin receptors (mechano- and thermoceptors);

· different pressure in the interpleural fissure and airways (can reach 70 mm of water column, which is 10-15 times more than during subsequent quiet breathing).

During the implementation of the first breath, a significant elasticity of the lung tissue is overcome, which is due to the surface tension of the collapsed alveoli. To stretch the lungs of children who have not yet breathed, the pressure of the air flow must be approximately 3 times higher than in children who have switched to spontaneous breathing.

The process of the first breath is facilitated by a surfactant - surfactant, which in the form of a thin film covers the inner surface of the alveoli. The surfactant reduces surface tension and the work required to ventilate the lungs, and also keeps the alveoli in a straightened state, preventing them from sticking together. This substance begins to be synthesized at the 6th month of intrauterine life. When the alveoli are filled with air, the surfactant spreads over the surface of the alveoli with a monomolecular layer. Non-viable newborns who die from alveolar adhesion do not have surfactant.

In newborns, the number of respiratory movements is 40–60 per minute, the minute respiratory volume is 600–700 ml.

Minute respiratory volume (MOD) - the amount of air passed through the respiratory tract per minute. MOD is equal to the product of the depth of inspiration and the respiratory rate.

Minute respiratory volume (MOD)

Breathing in children is frequent and superficial, as they are dominated by diaphragmatic breathing, which requires overcoming the resistance of organs abdominal cavity(Children have a relatively large liver and frequent intestinal distention.)

Diaphragmatic breathing- breathing, carried out by contraction of the diaphragm and abdominal muscles.

Minute respiratory volume (MOD) gradually increases during preschool and primary school age. This indicator, due to the high respiratory rate in children, lags less behind adult values: at 4 years old - 3.4 l / min, at 7 years old - 3.8 l / min, at 11 years old - 4-6 l / min.

Respiratory rate in children of different ages:

1–2 months 35–48

1–3 years 28–35

4–6 years old 24–26

7–9 years 21–23

10–12 years 18–20

13–15 years 17–18

Value

Duration of breath holding in children is small, since they have a very high metabolic rate, a large need for oxygen and low adaptation to anaerobic conditions. They very quickly decrease the content of oxyhemoglobin in the blood, and already at its content of 90-92% in the blood, breath holding stops (in adults, breath holding stops at a much lower content of oxyhemoglobin - 80-85%, and for adapted athletes - even at 50- 60%). The duration of breath holding on inspiration (Stange test) at the age of 7-11 years is about 20-40 s. (in adults - 30-90 s), and on exhalation (Genchi test) -15-20 s. (for adults - 35-40 s.).

Due to the mild excitability of the respiratory center, the respiratory rate in children changes significantly during the day under the influence of various influences: mental excitation, physical activity, an increase in body temperature and the environment.

According to A. G. Khripkov et al. (1990) children of the first years of life have a higher resistance to lack of oxygen (hypoxia) than older children. The formation of the functional maturity of the respiratory center continues during the first 11-12 years, and at the age of 14-15 it becomes adequate for such regulation in adults. With the maturation of the cerebral cortex (15-16 years), the ability to consciously change the parameters of breathing is improved: hold your breath, make maximum ventilation, etc.

Up to 8 years, the respiratory rate in boys is slightly higher than in girls. By puberty, the respiratory rate in girls becomes more. This ratio is maintained throughout life.

In newborns and infants breathing is irregular. Deep breathing is replaced by shallow. Pauses between inhalation and exhalation are uneven.

The duration of inhalation and exhalation in children is shorter than in adults: inhalation is 0.5–0.6 s (in adults 0.98–2.82 s), and exhalation is 0.7–1 s (in adults 1.62 –5.75 s). The ratio between inhalation and exhalation becomes the same as in adults, already from the moment of birth: inhalation is shorter than exhalation.

Thoracic breathing in a newborn is difficult, since the chest has a pyramidal shape, and the upper ribs, the handle of the sternum, the collarbone and the entire shoulder girdle are located high, the ribs lie almost horizontally, the respiratory muscles of the chest are still weak. When the child begins to walk and increasingly takes up an upright position, his breathing becomes abdominal. chest breathing(mixed breathing) - breathing in which the muscles of the chest and abdominal cavities, as well as the diaphragm, are active.

From 3-7 years due to the development of the muscles of the shoulder girdle chest type breathing begins to dominate the diaphragmatic. chest breathing - breathing, which active movement chest: expansion of the chest and retraction of the abdomen when inhaling and reverse movements - when exhaling.

Sexual differences in the type of breathing begin to appear from the age of 7–8 years, the formation ends by the age of 14–17.

At this age, girls have a thoracic type of breathing, and boys have abdominal breathing.

At the age of 3 to 7 years, due to the development of the shoulder girdle, the chest type of breathing begins to predominate, and by the age of 7 it becomes pronounced.

At the age of 7-8, gender differences in the type of breathing begin: in boys, the abdominal type of breathing becomes predominant, in girls - chest. The sexual differentiation of respiration ends by the age of 14–17.

Sex differences functional indicators of the respiratory system appear with the first signs of puberty (in girls from 10-11 years old, in boys from 12 years old). Uneven development respiratory function lung remains a feature of this stage of the individual development of the child's body.

Between 8 and 9 years of age, against the background of increased growth of the bronchial tree, the relative alveolar ventilation of the lungs and the relative oxygen content in the blood are significantly reduced. Characteristically, the rate of development of the respiratory function slows down in the prepubertal period, and again it intensifies at the beginning of prepuberty. After 10 years after the relative stabilization of functional parameters, their age-related transformations increase: lung volumes, lung compliance increase, the relative values of pulmonary ventilation and oxygen uptake by the lungs decrease even more, functional indicators begin to differ in boys and girls.

The stages of maturation of the regulatory functions of the lungs are divided into three periods: 13-14 years old (chemoreceptor), 15-16 years old (mechanoreceptor), 17 years and older (central). A close connection between the formation of the respiratory system and the physical development and maturation of other body systems was noted.

Tidal volume(the volume of air that a person inhales and exhales at rest) in a newborn baby is only 15-20 ml. The volume of the lungs during inspiration increases slightly. During this period, the body is provided with O2 due to the high respiratory rate. In the process of development of the organism with a decrease in the frequency of breathing, the respiratory volume increases:

Age Tidal volume

1–12 months 30–70

1–3 years 70–115

4–6 years old 120–160

7–9 years old 160–230

10–12 years old 230–260

13–15 years old 280–375

Relative breathing volume(tidal volume to body weight ratio) is greater in children than in adults because children high level metabolism and O2 consumption.

Value maximum lung ventilation (MVL) reaches only 50-60 l/min in primary school age (for untrained adults it is about 100-140 l/min, and for athletes - 200 l/min and more).

VC is determined in children at the age of 5–6 years, since this requires the active and conscious participation of the child himself. In a newborn, the so-called vital capacity of a cry is determined. It is believed that with a strong cry, the volume of exhaled air is equal to the VC. In the first minutes after birth, it is 56–110 ml.

During puberty, some children may experience a temporary violation of the regulation of breathing (resistance to lack of oxygen decreases, respiratory rate increases, etc.), which should be taken into account when organizing physical education classes.

Sports training significantly increases breathing parameters. In trained adults, an increase in pulmonary gas exchange during physical exertion occurs mainly due to the depth of breathing, while in children, especially of primary school age, due to an increase in respiratory rate, which is less effective.

Children also achieve maximum oxygen supply more quickly, but this does not last long, reducing endurance in work.

It is very important to teach children to breathe correctly from early childhood when walking, running, swimming, etc. This is facilitated by normal posture in all types of work, breathing through the nose, as well as special exercises in breathing exercises. With the correct breathing stereotype, the duration of the exhalation should be 2 times the duration of the inhalation.

In the process of physical education, especially for children of preschool and primary school age (4-9 years old), special attention should be paid to educating proper breathing through the nose, both in a state of relative rest and during work or sports. Breathing exercises, as well as swimming, rowing, skating, skiing, especially contribute to the improvement of breathing.

Breathing exercises are best done in full breathing mode (deep breathing with a combination of thoracic and abdominal rear breathing). Such gymnastics is recommended to be done 2-3 times a day 1-2 hours after eating. In this case, you should stand or sit upright in a relaxed state. It is necessary to take a quick (2-3 s) deep breath and a slow (15-30 s) exhalation with full tension of the diaphragm and "compression" of the chest. At the end of the exhalation, it is advisable to hold your breath for 5-10 seconds, and then forcefully inhale again. Such breaths can be 2-4 per minute. The duration of one session of breathing exercises should be 5-7 minutes.

Breathing exercises are of great health importance. Taking a deep breath lowers the pressure in the chest cavity (by lowering the diaphragm). This leads to an increase in venous blood flow to the right atrium, which facilitates the work of the heart. The diaphragm, descending towards the abdomen, massages the liver and the second organs of the abdominal cavity, helps to remove metabolic products from them, and from the liver - venous stagnant blood and bile.

During a deep exhalation, the diaphragm rises, which contributes to the outflow of blood from the lower parts of the body, from the organs of the small pelvis and abdomen. There is also a slight massage of the heart and improved blood supply to the myocardium. The specified effects of respiratory gymnastics in the best way produce stereotypes of correct breathing, and also contribute to general improvement, increase defensive forces, optimization of internal organs.

Air requirements

The hygienic properties of the air environment are determined not only by its chemical composition, but also by its physical state: temperature, humidity, pressure, mobility, atmospheric electric field voltage, solar radiation, etc. For normal human life, the constancy of body temperature and the environment is of great importance, which has influence on the equilibrium of the processes of heat generation and heat transfer.

The high temperature of the surrounding air makes it difficult to release heat, which leads to an increase in body temperature. At the same time, the pulse and breathing become more frequent, fatigue increases, and working capacity decreases.

Electrical and magnetic field atmospheres also affect man. For example, negative air particles have a positive effect on the body (relieve fatigue, increase efficiency), and positive ions, on the contrary, depress breathing, etc.

In addition to dust, the air also contains microorganisms - bacteria, spores, mold fungi, etc. They are especially numerous in enclosed spaces.

The microclimate of school premises. Microclimate called the totality of physicochemical and biological properties of the air. For the school, this environment is its premises, for the city - its territory, etc. Hygienically normal air in the school is an important condition for the progress and performance of students. With a long stay in a classroom or office of 35–40 students, the air ceases to meet hygienic requirements. Change it chemical composition, physical properties and bacterial contamination. All these indicators increase sharply by the end of the lessons.

Most favorable conditions in the classroom are temperatures of 16–18 °C and relative humidity of 30–60%. With these standards, the working capacity and good health of students are preserved for the longest time. At the same time, the difference in air temperature along the vertical and horizontal lines of the class should not exceed 2–3 °C, and the air velocity should not exceed 0.1–0.2 m/s.

Natural ventilation. The flow of outside air into the room due to the difference in temperature and pressure through the pores and cracks in the building material or through specially made openings is called natural ventilation. Air vents and transoms are used to ventilate classrooms of this type.

Artificial ventilation. This ventilation is supply, exhaust and supply and exhaust (mixed) with natural or mechanical stimulation. Such ventilation is installed most often where it is necessary to remove exhaust air and gases generated during experiments. It is called forced ventilation, as the air is brought out through special exhaust ducts, which have several holes under the ceiling of the room. The air from the premises is directed to the attic and is led out through the pipes, where, to enhance the air flow in the exhaust ducts, thermal air movement stimulators are installed - deflectors or electric fans. The device of this type of ventilation is provided during the construction of buildings.

Respiration is a process of constant exchange of gases between the body and the environment, necessary for life. Breathing provides a constant supply of oxygen to the body, which is necessary for the implementation of oxidative processes, which are a source of energy. Without access to oxygen, life lasts only a few minutes. During oxidative processes, carbon dioxide is formed, which must be removed from the body.

^ The concept of respiration includes the following processes:

1. external respiration- the exchange of gases between the external environment and the lungs - pulmonary ventilation;

2. exchange of gases in the lungs between alveolar air and capillary blood - pulmonary respiration;

3. transport of gases in the blood transport of oxygen from the lungs to tissues and carbon dioxide to the lungs;

4. gas exchange in tissues;

5. internal or tissue respiration- biological processes occurring in the mitochondria of cells.

The human respiratory system consists of:

1) airways, which include the nasal cavity, nasopharynx, larynx, trachea, bronchi;

2) lungs - consisting of bronchioles, alveolar sacs and richly supplied with vascular ramifications;

3) the musculoskeletal system, which provides respiratory movements: it includes the ribs, intercostal and other auxiliary muscles, and the diaphragm.

With the growth and development of the body lung volume increases. The lungs in children grow mainly due to an increase in the volume of the alveoli (in newborns, the diameter of the alveoli is 0.07 mm, in an adult it reaches 0.2 mm. Up to 3 years, there is an increased growth of the lungs and differentiation of their individual elements. The number of alveoli by 8 years reaches the number lung growth rates decrease between the ages of 3 and 7. Especially intensive growth of the lungs is observed between 12 and 16. The weight of both lungs at 9-10 years is 395 g, and in adults almost 1000 g. At the age of 12, it increases 10 times compared to the lung volume of a newborn, and by the end of puberty - 20 times (mainly due to an increase in the volume of the alveoli).Accordingly, gas exchange in the lungs changes, an increase in the total surface of the alveoli leads to an increase in the diffuse capacity of the lungs.

At the age of 8-12 years occurs smooth maturation of the morphological structures of the lungs and the physical development of the body. However, between 8 and 9 years of age, the lengthening of the bronchial tree prevails over its expansion. As a result, the decrease in the dynamic resistance of the respiratory tract slows down, and in some cases there is no dynamics of tracheobronchial resistance. Smoothly, with a tendency to age-related increase, volumetric respiration rates also change. Qualitative changes on the verge of 8-12 years undergo elastic properties of the lungs and chest tissues. Their extensibility increases.

Breathing rate in children aged 8-12 years, it ranges from 22 to 25 breaths per minute without a clear age dependence. Tidal volume increases from 143 to 220 ml in girls and from 167 to 214 ml in boys. At the same time, the minute volume of respiration in boys and girls does not have significant differences. It gradually decreases in children from 8 to 9 years old and practically does not change between 10 and 11 years. The decrease in relative ventilation between 8 and 9 years of age and its downward trend from 11 to 12 years of age indicates relative hyperventilation in younger children compared to older ones. The increase in static lung volumes is most pronounced in girls from 10 to 11 years old and in boys from 10 to 12 years old.

Indicators such as the duration of breath holding, maximum lung ventilation (MVL), VC are determined in children from the age of 5, when they can consciously regulate breathing.

Vital capacity (VC) there are 3-5 times fewer preschoolers than adults, and 2 times fewer children of primary school age. At the age of 7-11 years, the ratio of VC to body weight (life index) is 70 ml/kg (in an adult - 80 ml/kg).

Duration of breath holding in children is small, since they have a very high metabolic rate, a large need for oxygen and low adaptation to anaerobic conditions. They very quickly decrease the content of oxyhemoglobin in the blood, and already at its content of 90-92% in the blood, breath holding stops (in adults, breath holding stops at a much lower content of oxyhemoglobin - 80-85%, and for adapted athletes - even at 50- 60%). The duration of breath holding on inspiration (Stange test) at the age of 7-11 years is about 20-40 s (in adults - 30-90 s), and on exhalation (Genchi test) -15-20 s (in adults - 35-40 s ).

Value MVL reaches only 50-60 l / min at primary school age (for untrained adults it is about 100-140 l / min, and for athletes - 200 l / min or more).

Indicators of the functional state of the airways and lung tissue change in close connection with the change in the anthropometric characteristics of the organism of children at this stage of ontogenesis. In the transitional period from the "second childhood" to adolescence (in girls at 11-12 years old, in boys from 12 years old), it is most pronounced. The basal-apical ventilation gradient, which characterizes the uneven distribution of gases in the lungs, remains lower in children under 9 years of age than in adults. At 10-11 years of age, a significant gradient of blood filling between the upper and lower zones of the lungs is revealed. There is a large heterogeneity in the ventilation ratio (blood flow in the lower zones of the lungs) and a tendency to increase with age.

Due to shallow breathing and a relatively large amount of "dead space" respiratory efficiency in children is low. Less oxygen passes from the alveolar air into the blood, and a lot of oxygen ends up in the exhaled air. As a result, the oxygen capacity of the blood is low - 13-15 vol.% (in adults - 19-20 vol.%).

However, in the course of research it was found that when 8 and 12-year-old boys adapt to dosed physical activity under the influence of moderate-intensity work, pulmonary ventilation increases, oxygen consumption increases markedly, and breathing efficiency increases. It was shown that physical activity led to some redistribution of the values of regional respiratory volumes of air, their greater functional load on the upper zones of the lungs.

In the process of age development increases the efficiency of gas exchange in the lungs, oxygen uptake increases to 3.9% and carbon dioxide release to 3.8%. The relative values of oxygen consumption continue to decrease, most noticeably at 9 years old - 4.9 ml / (min × kg), at 11 years the indicator is 4.6 ml / (min × kg) in girls and 4.85 ml / (min × kg) in boys. The relative content of oxygen in the blood in children aged 9-12 years is 1/4 of the level of infants and 1/2 of the level of children 4-7 years of age. However, the amount of oxygen physically soluble in the blood increases with age (in 7 year olds it did not exceed 90 mm Hg, in 8–10 year olds it was 93–97 mm Hg).

Sex differences functional indicators of the respiratory system appear with the first signs of puberty (in girls from 10-11 years old, in boys from 12 years old). The uneven development of the respiratory function of the lungs remains a feature of this stage of the individual development of the child's body.

Between 8 and 9 years of age, against the background of increased growth of the bronchial tree, the relative alveolar ventilation of the lungs and the relative oxygen content in the blood are significantly reduced. Characteristically, the rate of development of the respiratory function slows down in the prepubertal period, and again it intensifies at the beginning of prepuberty. After 10 years after the relative stabilization of functional parameters, their age-related transformations intensify: lung volumes, lung compliance increase, the relative values of pulmonary ventilation and oxygen uptake by the lungs decrease even more, functional indicators begin to differ in boys and girls.

^ Mechanism of regulation of respiration very complicated. The respiratory center provides a rhythmic change in the phases of the respiratory cycle due to the closure in it of signaling from the respiratory organs and vascular receptors. The respiratory center has well-developed connections with all parts of the central nervous system, due to which its activity can be combined with the activity of any part of the central nervous system. This ensures the restructuring of the activity of the respiratory center and the adaptation of the breathing process to the changing vital activity of the organism. In the regulation of respiration, neuroreflex mechanisms are predominant. Humoral factors act not directly on the respiratory center, but through peripheral and central chemoreceptors. The role of the cerebral cortex in the regulation of respiration was revealed.

By the time of birth central mechanisms breathing regulation provided by the reticular structures of the bridge, the sensory cortex and a number of formations of the limbic system in further postnatal development, new structures are included in the regulation of the respiratory function: the parafiscicumeric complex of the thalamus opticus, the posterior and lateral hypothalamus. The effector section of the functional respiratory system takes shape and reaches maturity by the 24-28th week of embryogenesis. The chemoreceptor glomus in newborns is highly sensitive to changes in blood pO2 and pCO2, which indicates sufficient maturity of the glomus itself and the nerve pathways coming from it. Such an automated function as breathing begins to improve from the first days of life, not only as a result of the continued development of synapses and new connections, but also due to the rapid formation of conditioned reflex reactions. They provide the best adaptation of the child's body to the environment.

Already from the first hours of life, children respond with an increase in ventilation to a drop in blood pO2 and a decrease in ventilation to the inhalation of oxygen. Unlike adults, the reaction to fluctuations in oxygen in the blood in newborns is insignificant and not stable. With age, an increase in tidal volume is of great importance in strengthening pulmonary ventilation. In preschool and primary school age, the increase in pulmonary ventilation is achieved mainly due to increased respiration. In adolescents, oxygen deficiency in the inhaled air causes an increase in tidal volume, and only half of them also increase the respiratory rate. The reaction of the respiratory center to a change in the concentration of carbon dioxide in the alveolar air and its content in arterial blood also changes in ontogenesis and at school age reaches the level of adults. During puberty, there are temporary violations regulation of respiration and the body of adolescents is less resistant to lack of oxygen; than the body of an adult. The need for oxygen, which increases with the growth and development of the organism, is ensured by the improvement of the regulation of the respiratory apparatus, leading to an increasing economization of its activity. As the cerebral cortex matures, the ability to arbitrarily change breathing improves - to suppress respiratory movements or to produce maximum ventilation of the lungs.

In an adult, during muscular work, pulmonary ventilation increases due to the increase and deepening of breathing. Activities such as running, swimming, skating, skiing, and cycling dramatically increase pulmonary ventilation. In trained people, the increase in pulmonary gas exchange occurs mainly due to an increase in the depth of breathing. Children, due to the peculiarities of their respiratory apparatus, cannot significantly change the depth of breathing during physical exertion, but increase their breathing. The already frequent and shallow breathing in children during physical exertion becomes even more frequent and superficial. This results in lower ventilation efficiency, especially in young children. The body of a teenager, unlike an adult, reaches the maximum level of oxygen consumption faster, but also stops working faster due to the inability to maintain oxygen consumption at a high level for a long time. Voluntary changes in breathing play an important role in the performance of a series of respiratory movements and help to correctly combine certain ones with the phase of breathing (inhalation and exhalation).

One of the important factors in ensuring the optimal functioning of the respiratory system under various types of loads is the regulation of the ratio of inhalation and exhalation. The most effective and facilitating physical and mental activity is the respiratory cycle, in which the exhalation is longer than the inhalation. Teaching children to breathe correctly when walking, running and other activities is one of the tasks of the teacher. One of the conditions for proper breathing is taking care of the development of the chest, because the duration and amplitude of the respiratory cycle depend on the action of external factors and the internal properties of the lung-chest system. For this it is important correct location body, especially while sitting at a desk, breathing exercises and other physical exercises that develop muscles that move the chest.

Especially useful in this regard are sports such as swimming, rowing, skating, skiing. Usually a person with a well-developed chest will breathe evenly and correctly. It is necessary to teach children to walk and stand, observing correct posture, as it helps to expand the chest, facilitates the activity of the lungs and provides deeper breathing. When the body is bent, less air enters the body. The correct position of the body of children in the process of various activities contributes to the expansion of the chest, provides deep breathing, On the contrary, when the body is bent, the opposite conditions are created, the normal activity lungs, they absorb less air, and at the same time oxygen, which reduces the body's resistance to adverse environmental factors.

Respiratory system in old age . There are atrophic processes in the mucous membrane of the respiratory organs, dystrophic and fibrous-sclerotic changes in the cartilage of the tracheobronchial tree. The walls of the alveoli become thinner, their elasticity decreases, and the membrane thickens. The structure of the total lung capacity changes significantly: it decreases vital capacity, the residual volume increases. All this disrupts pulmonary gas exchange, reduces the efficiency of ventilation. characteristic feature age-related changes is the stressful functioning of the respiratory system. This is reflected in an increase in the ventilation equivalent, a decrease in the oxygen utilization rate, an increase in the respiratory rate and the amplitude of respiratory fluctuations in transpulmonary pressure.

With age, the functionality of the respiratory system is limited. In this regard, the age-related decrease in maximum lung ventilation, maximum levels of transpulmonary pressure, and work of breathing are indicative. The maximum values of ventilation indicators in the elderly and old people clearly decrease under conditions of intense functioning during hypoxia, hypercapnia, and physical activity. Regarding the causes of these disorders, it should be noted changes in the musculoskeletal apparatus of the chest - osteochondrosis thoracic spine, costal cartilage ossification, degenerative-dystrophic changes in the costovertebral joints, atrophic and fibrous-dystrophic processes in the respiratory muscles. These shifts lead to a change in the shape of the chest and a decrease in its mobility.

One of the most important causes of age-related changes in pulmonary ventilation, its intense functioning is a violation of bronchial patency due to anatomical and functional changes in the bronchial tree (infiltration of the walls of the bronchi with lymphocytes and plasma cells, sclerosis of the bronchial walls, the appearance of mucus in the lumen of the bronchi, deflated epithelium, deformation of the bronchi due to peribronchial overgrowth connective tissue). The deterioration of bronchial patency is also associated with a decrease in the elasticity of the lungs (the elastic recoil of the lungs decreases). An increase in the volume of the airways and, consequently, dead space with a corresponding decrease in the proportion of alveolar ventilation worsens the conditions for gas exchange in the lungs. A decrease in oxygen tension and an increase in carbon dioxide tension in arterial blood are characteristic, which is due to the growth of alveoloarterial gradients of these gases and reflects a violation of pulmonary gas exchange at the stage of alveolar air - capillary blood. The causes of arterial hypoxemia during aging include uneven ventilation, mismatch between ventilation and blood flow in the lungs, an increase in anatomical shunting, a decrease in the diffusion surface with a decrease in the diffusion capacity of the lungs. Among these factors, the discrepancy between ventilation and lung perfusion is of decisive importance. Due to the weakening of the Hering-Breuer reflex, the reciprocal relationship between expiratory and inspiratory neurons is disrupted, which contributes to the increase in respiratory arrhythmias.

The resulting changes lead to a decrease in the adaptive capabilities of the respiratory system, to the occurrence of hypoxia, which sharply increases in stressful situations, pathological processes apparatus for external respiration.

^ VI. Age features of the digestive system
and METABOLISM

Digestion- this is the process of splitting food structures to components that have lost species specificity and can be absorbed in the gastrointestinal tract. At the same time, the plastic and energy value of nutrients is preserved. Once in the blood and lymph, nutrients are included in the metabolism of the body and absorbed by its tissues. Therefore, digestion provides nutrition to the body and is closely related to it.

During prenatal development the functions of the digestive organs are poorly expressed due to the absence of food irritants that stimulate the secretion of their glands. The amniotic fluid, which the fetus swallows from the second half of the intrauterine period of development, is a weak irritant of the digestive glands. In response to this, they secrete a secret that digests not a large number of proteins found in the amniotic fluid. The secretory function of the digestive glands develops intensively after birth under the influence of the irritating action of nutrients that cause a reflex secretion of digestive juices.

There are lactotrophic, artificial and mixed nutrition. With the lactotrophic type of nutrition, the nutrients of milk are hydrolyzed by means of enzymes, followed by an ever-increasing role of their own digestion. The intensification of the secretory activity of the digestive glands develops gradually and increases sharply with the transition to mixed and especially artificial nutrition of children.

With the transition to the reception dense food special meaning acquire its crushing, wetting and the formation of a food lump, which is achieved by chewing. Chewing becomes effective relatively late by 1.5 - 2 years. In the first months after birth teeth located under the mucous membrane of the gums. The eruption of milk teeth occurs from the 6th to the 30th month in a certain sequence of different teeth. Milk teeth are replaced by permanent ones in the period from 5 - 6 to 12 - 13 years. During the eruption of milk teeth, chewing movements are weak arrhythmic, with an increase in the number of teeth they become rhythmic and in strength, duration, character are brought into line with the properties of the chewed food. In the pubertal period, the development of teeth ends, with the exception of the third molars (wisdom teeth), which erupt at 18-25 years.

With the appearance of milk teeth, the child begins to salivate markedly. It intensifies during the first year of life and continues to improve in the amount and composition of saliva with an increase in the variety of food.

In newborns stomach has a rounded shape and is located horizontally. By 1 year, it becomes oblong and acquires a vertical position. The form characteristic of adults is formed by 7-11 years. The gastric mucosa of children is less folded and thinner than that of adults, contains fewer glands, and in each of them the number of glanulocytes is less than in adults. With age, the total number of glands and their number per 1 mm 2 of the mucous membrane increases. Gastric juice is poorer in enzymes, their activity is still low. This makes it difficult to digest food. Low hydrochloric acid reduces the bactericidal properties of gastric juice, which leads to frequent gastrointestinal diseases children.

glands small intestine, as well as the glands of the stomach, functionally not fully developed. Compound intestinal juice in a child the same as in an adult, but the digestive power of enzymes is much less. It increases simultaneously with an increase in the activity of the gastric glands and an increase in the acidity of its juice. The pancreas also secretes less active juice. The intestines of the child are characterized by active and very unstable peristalsis. It can easily increase under the influence of local irritation (food intake, its fermentation in the intestine) and various external influences. So, the general overheating of the child, a sharp sound irritation (cry, knock), an increase in his motor activity lead to an increase in peristalsis. Due to the fact that children have a relatively long intestine and a long, but weak, easily stretched mesentery, there is a possibility of intestinal volvulus. The motor function of the gastrointestinal tract becomes the same as in adults by 3-4 years.

Functions develop intensively during preschool age pancreas and liver child. At the age of 6-9 years, the activity of the glands of the digestive tract increases significantly, the digestive functions are improved. Fundamental difference digestion in a child's body from an adult is that they have only parietal digestion and there is no intracavitary digestion of food.

Insufficiency of absorption processes in small intestine to some extent compensated by the possibility of absorption in the stomach, which persists in children up to 10 years of age.

feature metabolic processes in the child's body is the predominance of anabolic processes (assimilation) over catabolic (dissimilation). A growing body requires increased intake of nutrients, especially proteins. Characteristic for children positive nitrogen balance i.e., the intake of nitrogen into the body exceeds its excretion.

Usage nutritious foods goes in two directions:

To ensure the growth and development of the body (plastic function)

To ensure motor activity (energy function).

For children due to the high intensity of metabolic processes is characterized by a higher than in adults, need for water and vitamins. The relative need for water (per 1 kg of body weight) decreases with age, and the absolute daily value of water consumption increases: at the age of 1 year, 0.8 l is needed, at 4 years - 1 l, at 7-10 years old 1.4 l, at 11 -14 years old - 1.5 liters.

IN childhood also requires a constant supply minerals: for bone growth (calcium, phosphorus), for excitation processes in the nervous and muscle tissue (sodium and potassium), for the formation of hemoglobin (iron), etc.

energy exchange children of preschool and primary school age significantly (almost 2 times) higher than the level of metabolism in adults, declining most sharply in the first 5 years and less noticeable - throughout the rest of life. Daily energy consumption increases with age: at 4 years old - 2000 kcal, at 7 years old - 2400 kcal, at 11 years old - 2800 kcal.

^ VII. Age features of the endocrine system

The endocrine system plays an important role in the regulation of body functions. The organs of this system are endocrine glands - secrete special substances (hormones) that have a significant and specialized effect on the metabolism, structure and function of organs and tissues. Hormones change the permeability of cell membranes, providing access to cells of nutrients and regulatory substances. They directly act on the genetic apparatus in the cell nuclei, regulating the reading of hereditary information, enhancing RNA synthesis and, accordingly, the processes of protein and enzyme synthesis in the body. With the participation of hormones, the processes of adaptation to various environmental conditions, including stressful situations, are formed in the developing organism.

The human endocrine glands are small in size, have a very small mass (from fractions of a gram to several grams), and are richly supplied with blood vessels. Blood brings to them the necessary building material and carries away chemically active secrets. TO endocrine glands an extensive network of nerve fibers is suitable, their activity is constantly controlled by the nervous system.

Even before the birth of a child, some endocrine glands begin to function, which are of great importance in the first years after birth (pineal gland, thymus, pancreatic and adrenal hormones).

^ Thyroid. In the process of ontogenesis, the mass thyroid gland increases significantly - from 1 g in the neonatal period to 10 g by 10 years. With the onset of puberty, the growth of the gland is especially intense, during the same period the functional tension of the thyroid gland increases, as evidenced by a significant increase in the content of total protein, which is part of the thyroid hormone. The content of thyrotropin in the blood increases intensively up to 7 years.

An increase in the content of thyroid hormones is noted by the age of 10 and at the final stages of puberty (15-16 years). At the age of 5-6 to 9-10 years, the pituitary-thyroid relationship changes qualitatively; the sensitivity of the thyroid gland to thyroid-stimulating hormones decreases, the highest sensitivity to which was noted at 5-6 years. This indicates that the thyroid gland is of particular importance for the development of the organism in early age.

Insufficiency of thyroid function in childhood leads to cretinism. At the same time, growth is delayed and the proportions of the body are violated, sexual development is delayed, mental development lags behind. Early detection of hypothyroidism and appropriate treatment has a significant positive effect.

A sharp reaction of a growing organism is caused by an insufficient function parathyroid glands, regulating calcium metabolism in the body. With their hypofunction, the calcium content in the blood falls, the excitability of the nervous and muscle tissues increases, and convulsions develop. Hyperfunction of the parathyroid glands leads to the leaching of calcium from the bones and an increase in its concentration in the blood. This leads to excessive bone flexibility, skeletal deformity and calcium deposition in blood vessels and other organs.

Early development thymus gland (thymus) provides a high level of immunity in the body. It affects the maturation of lymphocytes, the growth of the spleen and lymph nodes. If its hormonal activity is disturbed in infants, the protective properties of the body are sharply reduced, gamma globulin, which is of great importance in the formation of antibodies, disappears in the blood, and the child dies at the age of 2-5 months.

Adrenals. The adrenal glands from the first weeks of life are characterized by rapid structural transformations. The development of adrenal measles proceeds intensively in the first years of a child's life. By the age of 7, its width reaches 881 microns, at the age of 14 it is 1003.6 microns. The adrenal medulla at the time of birth is represented by immature nerve cells. They quickly differentiate during the first years of life into mature cells, called chromophilic, as they are distinguished by the ability to stain yellow with chromium salts. These cells synthesize hormones, the action of which has much in common with the sympathetic nervous system - catecholamines (adrenaline and norepinephrine). Synthesized catecholamines are contained in the medulla in the form of granules, from which they are released under the action of appropriate stimuli and enter the venous blood flowing from the adrenal cortex and passing through the medulla. The stimuli for the entry of catecholamines into the blood are excitation, irritation of the sympathetic nerves, physical activity, cooling, etc. The main hormone of the medulla is adrenalin, it makes up about 80% of the hormones synthesized in this section of the adrenal glands. Adrenaline is known as one of the fastest acting hormones. It accelerates the circulation of blood, strengthens and speeds up heart contractions; improves pulmonary respiration, expands the bronchi; increases the breakdown of glycogen in the liver, the release of sugar into the blood; increases muscle contraction, reduces their fatigue, etc. All these effects of adrenaline lead to one common result - the mobilization of all the forces of the body to perform hard work.

Increased secretion of adrenaline is one of the most important mechanisms of restructuring in the functioning of the body in extreme situations, during emotional stress, sudden physical exertion, and during cooling.

The close connection of the chromophilic cells of the adrenal gland with the sympathetic nervous system causes the rapid release of adrenaline in all cases when circumstances arise in a person's life that require an urgent effort from him. A significant increase in the functional tension of the adrenal glands is observed by the age of 6 and during puberty. At the same time, the content of steroid hormones and catecholamines in the blood increases significantly.

^ Pancreas. In newborns, intrasecretory pancreatic tissue predominates over exocrine pancreatic tissue. The islets of Langerhans increase significantly in size with age. Islets of large diameter (200-240 microns), characteristic of adults, are found after 10 years. An increase in the level of insulin in the blood in the period from 10 to 11 years was also established. The immaturity of the hormonal function of the pancreas may be one of the reasons why children diabetes is most often detected at the age of 6 to 12 years, especially after suffering acute infectious diseases (measles, chicken pox, mumps). It is noted that the development of the disease contributes to overeating, especially the excess of carbohydrate-rich foods.

Hormone secretion pituitary gland growth hormone increases gradually, and at the age of 6 increases more significantly, causing a noticeable increase in the growth of the child. However, the most significant increase in the secretion of this hormone occurs during the transition period, causing a sharp increase in body length.

epiphysis V preschool age carries out the most important processes of regulation of water and salt metabolism in the child's body. The vigorous activity of the pineal gland suppresses the underlying structures of the hypothalamus during this period.

With the weakening of the inhibitory effects of the pineal gland after the age of 7, the activity of the hypothalamus increases and a close relationship is formed between its functions and the pituitary gland, i.e. the hypothalamic-pituitary system is formed, transmitting the influence of the central nervous system through various endocrine glands to all organs and systems of the body.

^ VIII. SOME FEATURES OF ONTOGENESIS OF THE NERVOUS SYSTEM

Age-related changes in the morphofunctional organization of the neuron. In the early stages of embryonic development, a nerve cell is characterized by the presence of a large nucleus surrounded by a small amount of cytoplasm. In the process of development, the relative volume of the nucleus decreases. In the third month of intrauterine development, axon growth begins. Dendrites grow later than the axon. The growth of the myelin sheath leads to an increase in the speed of conduction of excitation along the nerve fiber and, as a result, the excitability of the neuron increases.

Myelination was first noted in the peripheral nerves, then the fibers of the spinal cord, the brain stem, the cerebellum, and later the fibers of the cerebral hemispheres are exposed to it. Motor nerve fibers are covered with a myelin sheath already at the time of birth. By the age of three, the myelination of nerve fibers is basically completed.

^ Development of the spinal cord. The spinal cord develops earlier than other parts of the nervous system. When the embryo's brain is at the stage of cerebral vesicles, the spinal cord already reaches a considerable size. In the early stages of fetal development, the spinal cord fills the entire cavity of the spinal canal. Then spinal column overtakes the spinal cord in growth. In newborns, the length of the spinal cord is 14-16 cm, by the age of 10 it doubles. The spinal cord grows slowly in thickness. In young children, the predominance of the anterior horns over the posterior ones is noted. Enlargement nerve cells spinal cord is observed in children during school years.

^ Growth and development of the brain. The mass of the brain of a newborn is 340-400 g, which is 1/8-1/9 of its body weight, while in an adult, the brain mass is 1/40 of the body weight. The most intensive brain growth occurs in the first three years of a child's life.

Until the 4th month of fetal development, the surface of the cerebral hemispheres is smooth. By 5 months of intrauterine development, lateral, then central, parietal-occipital sulci are formed. By the time of birth, the cerebral cortex has the same type of structure as in an adult. But the shape and size of the furrows and convolutions change significantly even after birth.

The nerve cells of the newborn have a simple spindle shape with a very a small amount processes, the cortex in children is much thinner than in adults.

Myelination of nerve fibers, the arrangement of layers of the cortex, the differentiation of nerve cells are mostly completed by 3 years. The subsequent development of the brain is characterized by an increase in the number of associative fibers and the formation of new neural connections. The mass of the brain in these years increases slightly.

All reactions of adaptation to the conditions of the new environment require rapid development brain, especially its higher parts - the cerebral cortex.

However, different zones of the bark do not mature at the same time. First of all, in the very first years of life, the projection zones of the cortex (primary fields) - visual, motor, auditory, etc., mature, then the secondary fields (the periphery of the analyzers) and, last of all, up to the adult state - tertiary, associative fields of the cortex (zones of higher analysis and synthesis). Thus, the motor zone of the cortex (primary field) is mainly formed by the age of 4, and the associative fields of the frontal and lower parietal cortex in terms of the territory occupied, the thickness and degree of cell differentiation by the age of 7-8 years mature only by 80%, especially lagging behind in development. in boys compared to girls.

Formed the fastest functional systems, including vertical connections between the cortex and peripheral organs and providing vital skills - sucking, defensive reactions (sneezing, blinking, etc.), elementary movements. Very early in infants in the region of the frontal region, a center for the identification of familiar faces is formed. However, the development of processes of cortical neurons and myelination of nerve fibers in the cortex, the processes of establishing horizontal intercentral relationships in the cerebral cortex, are slower. As a result, the first years of life are characterized by a lack of intersystem relationships in the body (for example, between the visual and motor systems, which underlies the imperfection of visual-motor reactions).

For the nervous system children of preschool and primary school age characterized by high excitability and weakness of inhibitory processes, which leads to a wide irradiation of excitation through the cortex and insufficient coordination of movements. However, long-term maintenance of the excitation process is still impossible, and children quickly get tired. It is especially important to strictly dose the loads, since children of this age are characterized by an underdeveloped sense of fatigue. They poorly assess changes in the internal environment of the body during fatigue and cannot fully reflect them in words even when completely exhausted.

With the weakness of cortical processes in children, subcortical processes of excitation predominate. Children at this age are easily distracted by any external stimuli. This extreme intensity of the orienting reaction reflects the involuntary nature of their attention. Arbitrary attention is very short-term: children 5-7 years old are able to focus only for 15-20 minutes.

A child of the first years of life has a poorly developed subjective sense of time. The body scheme is formed in a child by the age of 6, and more complex spatial representations - by the age of 9-10, which depends on the development of the cerebral hemispheres and the improvement of sensorimotor functions.

Higher nervous activity of children of preschool and primary school age is characterized by the slow development of individual conditioned reflexes and the formation of dynamic stereotypes, as well as the particular difficulty of their alteration. Of great importance for the formation of motor skills is the use of imitative reflexes, the emotionality of classes, and game activity.

Children of 2-3 years old are distinguished by a strong stereotypical attachment to an unchanged environment, to familiar faces around them and to acquired skills. Alteration of these stereotypes occurs with great difficulty, often leading to disruptions in higher nervous activity. In 5-6-year-old children, the strength and mobility of nervous processes increase. They are able to consciously build programs of movements and control their implementation, it is easier to rebuild programs.

At primary school age, the predominant influences of the cortex on subcortical processes already arise, the processes of internal inhibition and voluntary attention intensify, the ability to master complex programs of activity appears, and characteristic individual typological features of the child's higher nervous activity are formed.

Of particular importance in the behavior of the child is the development of speech. Until the age of 6, reactions to direct signals predominate in children (the first signal system, according to I.P. Pavlov), and from the age of 6, speech signals begin to dominate (the second signal system).

Middle and high school age significant development is noted in all higher structures of the central nervous system. By the period of puberty, the weight of the brain in comparison with the newborn increases 3.5 times in boys and 3 times in girls.

Up to 13-15 years, the development of the diencephalon continues. There is an increase in the volume and nerve fibers of the thalamus, differentiation of the nuclei of the hypothalamus. By the age of 15, the cerebellum reaches adult size. In the cerebral cortex, the total length of the furrows by the age of 10 increases by 2 times, and the area of the cortex - by 3 times. In adolescents, the process of myelination of the nerve pathways ends.

The period from 9 to 12 years is characterized by sharp increase interconnections between different cortical centers, mainly due to the growth of neuronal processes in the horizontal direction. This creates a morphological and functional basis for the development of the integrative functions of the brain, the establishment of intersystem relationships.

At the age of 10-12 years, the inhibitory effects of the cortex on the subcortical structures increase. Cortical-subcortical relationships close to the adult type are formed with the leading role of the cerebral cortex and the subordinate role of the subcortex.

A functional basis is being created for systemic processes in the cortex, which provide a high level of useful information extraction from afferent messages and the construction of complex multi-purpose behavioral programs. In 13-year-old adolescents, the ability to process information, make quick decisions, and increase the efficiency of tactical thinking are significantly improved. The time for solving tactical tasks is significantly reduced in comparison with 10-year ones. It changes little by the age of 16, but does not yet reach adult values.

The noise immunity of behavioral reactions and motor skills reaches an adult level by the age of 13 years. This ability has great individual differences, it is genetically controlled and changes little during training.

The smooth improvement of brain processes in adolescents is disturbed as they enter puberty - in girls at 11-13 years old, in boys at 13-15 years old. This period is characterized by a weakening of the inhibitory influences of the cortex on the underlying structures, causing strong excitation throughout the cortex and an increase in emotional reactions in adolescents. The activity of the sympathetic department of the nervous system and the concentration of adrenaline in the blood increase. The blood supply to the brain is deteriorating.

Such changes lead to a violation of the fine mosaic of excited and inhibited areas of the cortex, disrupt the coordination of movements, impair memory and sense of time. Adolescents' behavior becomes unstable, often unmotivated and aggressive. Significant changes also occur in interhemispheric relations - the role of the right hemisphere in behavioral reactions temporarily increases. In a teenager, the activity of the second signaling system (speech functions) worsens, the importance of visual-spatial information increases. Violations of higher nervous activity are noted - all types of internal inhibition are violated, the formation of conditioned reflexes, the consolidation and alteration of dynamic stereotypes are hindered. There are sleep disorders.

Hormonal and structural changes in the transitional period slow down the growth of the body in length, reduce the rate of development of strength and endurance.

With the end of this period of restructuring in the body (after 13 years in girls and 15 years in boys), the leading role of the left hemisphere of the brain again increases, cortical-subcortical relationships are established with the leading role of the cortex. The increased level of cortical excitability decreases and the processes of higher nervous activity are normalized.

The transition from the age of adolescents to adolescence is marked by an increased role of the anterior frontal tertiary fields and the transition of the dominant role from the right to the left hemisphere (in right-handers). This leads to a significant improvement in abstract-logical thinking, the development of a second signal system and extrapolation processes. The activity of the central nervous system is very close to the adult level. However, it is also distinguished by smaller functional reserves, lower resistance to high mental and physical stress. All reactions of adaptation to the conditions of a new environment require the rapid development of the brain, especially its higher sections - the cerebral cortex.

^ Age dynamics of sensory processes is determined by the gradual maturation of the various parts of the analyzer. Receptor apparatuses mature in the prenatal period and are the most mature by the time of birth. The conducting system and the perceiving apparatus of the projection zone undergo significant changes, which leads to a change in the parameters of the reaction to an external stimulus. A consequence of the complication of the ensemble organization of neurons and the improvement of the mechanisms of information processing carried out in the projection cortical zone is the complication of the possibilities for analyzing and processing the stimulus, which is observed already in the first months of a child's life. At the same stage of development, myelination of afferent pathways occurs. This leads to a significant reduction in the time of receipt of information by cortical neurons: the latent (hidden) period of the reaction is significantly reduced. Further changes in the processing of external signals are associated with the formation of complex neural networks, including various cortical zones and determining the formation of the process of perception as a mental function.

The development of sensory systems mainly occurs during preschool and primary school age.

^ visual sensory system especially rapidly develops during the first 3 years of life, then its improvement continues up to 12-14 years. In the first 2 weeks of life, coordination of the movements of both eyes (binocular vision) is formed. At 2 months, eye movements are noted when tracing objects. From the age of 4 months, the eyes accurately fix the object and eye movements are combined with hand movements.

In children of the first 4-6 years of life eyeball not grown long enough yet. Although the lens of the eye has high elasticity and focuses light rays well, the image falls behind the retina, i.e., children's farsightedness occurs. At this age, colors are still poorly distinguished. In the future, with age, the manifestations of farsightedness decrease, the number of children with normal refraction increases.

In the transition from preschool to primary school age, as the relationship between visual information and motor experience improves, the assessment of the depth of space improves. The field of view increases sharply from the age of 6, reaching adult values by the age of 8. A qualitative restructuring of visual perceptions occurs at the age of 6 years, when the associative lower parietal areas of the brain begin to be involved in the analysis of visual information. At the same time, the mechanism of recognition of integral images is significantly improved.

The maturation of the frontal association zones provides another qualitative restructuring at the age of 9-10 years. visual perception, providing a fine analysis of the complex forms of the picture of the outside world, selective perception of individual components of the image, an active search for the most informative signals of the environment.

By the age of 10-12 years, the formation visual function basically ends, reaching the level of an adult organism.

^ auditory sensory system the child is of paramount importance for the development of speech, providing not only the perception of the speech of strangers, but also playing the formative role of the feedback system in their own pronunciation of words. It is in the range of speech frequencies (1000-3000 Hz) that the greatest sensitivity of the auditory system is observed. Her excitability to verbal signals especially noticeably increases at the age of 4 years and continues to increase by 6-7 years. However, hearing acuity in children aged 7-13 (hearing thresholds) is still worse than in 14-19 years, when the highest sensitivity is reached. Children have a particularly wide range of audible sounds - from 16 to 22,000 Hz. By the age of 15, the upper limit of this range drops to 15,000-20,000 Hz, which corresponds to the level of adults.

The auditory sensory system, analyzing the duration of sound signals, the tempo and rhythm of movements, is involved in the development of a sense of time, and due to the presence of two ears (binaural hearing), it is included in the formation of the child's spatial representations.

^ motor sensory system matures in humans one of the first. The subcortical sections of the motor sensory system mature earlier than the cortical ones: by the age of 6-7 years, the volume of subcortical formations increases to 98% of the final value in adults, and cortical formations - only up to 70-80%.

At the same time, the thresholds for distinguishing the strength of muscle tension in preschoolers are still several times higher than the level of indicators of an adult organism. By the age of 12-14, the development of the motor sensory system reaches an adult level. An increase in muscle sensitivity can continue further - up to 16-20 years, contributing to the fine coordination of muscle efforts.

^ vestibular sensory system is one of the most ancient sensory systems of the body and during ontogenesis it also develops quite early. The receptor apparatus begins to form from the age of 7 weeks of intrauterine development, and in a 6-month-old fetus it reaches the size of an adult organism.

Vestibular reflexes appear in the fetus as early as 4 months of age, causing tonic reactions and contractions of the muscles of the trunk, head and limbs. Reflexes from vestibular receptors are well expressed during the first year after the birth of a child. With age, the analysis of vestibular stimuli improves in a child, and the excitability of the vestibular sensory system decreases, and this reduces the manifestation of adverse motor and autonomic reactions. At the same time, many children show high vestibular resistance to rotations and turns.

^ Tactile touch system develops early, revealing already in newborns a general motor excitation when touched. Tactile sensitivity increases with the growth of the child's motor activity and reaches its maximum values by the age of 10 years.

^ Pain reception already present in newborns, especially in the face, but at an early age it is still not perfect enough. It improves with age. Thresholds of pain sensitivity decrease from infancy to 6 years by 8 times.

^ Temperature reception in newborns, it manifests itself as a sharp reaction (cry, breath holding, generalized motor activity) to an increase or decrease in ambient temperature. Then this reaction is replaced by more local manifestations with age, the reaction time is shortened from 2-11 s in the first months of life to 0.13-0.79 s in adults.

^ Taste and olfactory sensations although they are already present from the first days of life, they are still inconsistent and inaccurate, often inadequate to stimuli, and are of a generalized nature. The sensitivity of these sensory systems noticeably increases by the age of 5-6 years in preschool children and at primary school age practically reaches adult values.

breathing age hygienic air

Fetal respiration. Respiratory movements in the fetus occur long before birth. The stimulus for their occurrence is a decrease in the oxygen content in the blood of the fetus.

The respiratory movements of the fetus consist of a slight expansion of the chest, which is replaced by a longer fall, and then an even longer pause. When inhaling, the lungs do not expand, but only a slight negative pressure arises in the pleural space, which is absent at the time of the collapse of the chest. The significance of fetal respiratory movements lies in the fact that they contribute to an increase in the speed of blood movement through the vessels and its flow to the heart. And this leads to an improvement in the blood supply to the fetus and the supply of tissues with oxygen. In addition, fetal breathing movements are considered as a form of lung function training.

Breath of a newborn. The occurrence of the first breath of a newborn is due to a number of reasons. After the umbilical cord is ligated, the placental exchange of gases between the blood of the fetus and the mother stops in the newborn. This leads to an increase in the content of carbon dioxide in the blood, which irritates the cells of the respiratory center and causing the occurrence rhythmic breathing.

The reason for the first breath of a newborn is a change in the conditions of its existence. The action of various environmental factors on all receptors on the surface of the body becomes the stimulus that reflexively contributes to the occurrence of inspiration. A particularly powerful factor is the irritation of skin receptors.

The first breath of a newborn is especially difficult. In its implementation, the elasticity of the lung tissue is overcome, which is increased due to the surface tension forces of the walls of the collapsed alveoli and bronchi. After the appearance of the first 1-3 respiratory movements, the lungs are completely straightened and evenly filled with air.

The chest grows faster than the lungs, therefore, negative pressure arises in the pleural cavity, and conditions are created for the constant stretching of the lungs. The creation of negative pressure in the pleural cavity and maintaining it at a constant level also depends on the properties of the pleural tissue. It has a high absorption capacity. Therefore, the gas introduced into the pleural cavity and reducing the negative pressure in it is quickly absorbed, and the negative pressure in it is restored again.

Features of the child's breathing are associated with the structure and development of his chest. In a newborn, the chest has a pyramidal shape, by the age of 3 it becomes cone-shaped, and by the age of 12 it is almost the same as in an adult. Newborns have an elastic diaphragm, its tendon part occupies a small area, and the muscular part occupies a large one. As it develops, the muscular part of the diaphragm increases even more. It begins to atrophy from the age of 60, and instead of it, the tendon part increases. Since infants are mainly diaphragmatic breathing, during inspiration, the resistance of the internal organs located in the abdominal cavity must be overcome. In addition, when breathing, one has to overcome the elasticity of the lung tissue, which in newborns is still large and decreases with age. It is also necessary to overcome bronchial resistance, which in children is much greater than in adults. Therefore, the work expended on breathing is much greater in children than in adults.

Diaphragmatic breathing persists until the second half of the first year of life. As the child grows, the chest descends and the ribs take on an oblique position. At the same time, mixed breathing (chest-abdominal) occurs in infants, and stronger mobility of the chest is observed in its lower sections. In connection with the development of the shoulder girdle (3-7 years), chest breathing begins to predominate. From 8 to 10 years, there are gender differences in the type of breathing: in boys, a predominantly diaphragmatic type of breathing is established, and in girls - chest.

In newborns and infants, breathing is irregular. Arrhythmia is expressed in the fact that deep breathing is replaced by shallow breathing, pauses between inhalations and exhalations are uneven. The duration of inhalation and exhalation in children is shorter than in adults: inhalation is 0.5 - 0.6 s (in adults - 0.98 - 2.82 s), and exhalation - 0.7 - 1 s (in adults - from 1.62 to 5.75 s). Already from the moment of birth, the same ratio between inhalation and exhalation is established as in adults: inhalation is shorter than exhalation.

The frequency of respiratory movements in children decreases with age. In the fetus, it fluctuates between 46 - 64 per minute. Up to 8 years, the respiratory rate (RR) in boys is higher than in girls. By the time of puberty, BH in girls becomes larger, and this ratio is maintained throughout life. By the age of 14 - 15, the respiratory rate approaches the value of an adult.

The respiratory rate in children is much greater than in adults, it changes under the influence of various influences. It increases with mental arousal, small physical exercises, a slight increase in body temperature and the environment.

In a newborn child, the lungs are malelastic and relatively large. During inspiration, their volume increases slightly, by only 10 - 15 mm. Providing the child's body with oxygen occurs by increasing the frequency of breathing. The tidal volume of the lungs increases with age, along with a decrease in the respiratory rate.

With age, the absolute value of MOD increases, but the relative MOD (ratio of MOD to body weight) decreases. In newborns and children of the first year of life, it is twice as large as in adults. This is due to the fact that in children with the same relative tidal volume, the respiratory rate is several times greater than in adults. In this regard, pulmonary ventilation per 1 kg of body weight in children is greater (in newborns it is 400 ml, at 5-6 years of age it is 210, at 7 years of age - 160, at 8 - 10 years of age - 150, 11 - 13-year-olds - 130 - 145, 14-year-olds - 125, and 15 - 17-year-olds - 110). Due to this, a large need for a growing organism in O 2 is provided.

The value of VC increases with age due to the growth of the chest and lungs. In a child of 5-6 years old, it is 710-800 ml, in 14-16 years old - 2500-2600 ml. From 18 to 25 years, the vital capacity of the lungs is maximum, and after 35-40 years it decreases. The value of the vital capacity of the lungs varies depending on age, height, type of breathing, gender (girls are 100-200 ml less than boys).

In children, during physical work, breathing changes in a peculiar way. During the load, the RR increases and the TO almost does not change. Such breathing is uneconomical and cannot ensure long-term performance of work. Pulmonary ventilation in children during physical work increases by 2-7 times, and at high loads (mid-distance running) by almost 20 times. In girls, when performing maximum work, oxygen consumption is less than in boys, especially at 8-9 years old and at 16-18. All this should be taken into account when doing physical labor and sports with children of different ages.

Age features of the respiratory system. Children under 8-11 years of age have an underdeveloped nasal cavity, swollen mucous membrane and narrowed nasal passages. This makes it difficult to breathe through the nose and therefore children often breathe with their mouth open, which can contribute to colds, inflammation of the pharynx and larynx. In addition, constant mouth breathing can lead to frequent otitis media, bronchitis, dry mouth, abnormal development of the hard palate, disruption of the normal position of the nasal septum, etc. and to the narrowed nasal passages in children, further complicates their breathing through the nose. Therefore, colds in children require quick and effective treatment, especially since the infection can enter the cavities of the bones of the skull, causing the corresponding inflammation of the mucous membrane of these cavities and the development chronic rhinitis. From the nasal cavity, air enters through the choanae into the pharynx, where they also open oral cavity(calling), auditory (Eustachian canals) tubes, and originate the larynx and esophagus. In children under 10-12 years old, the pharynx is very short, which leads to the fact that infectious diseases of the upper respiratory tract are often complicated by inflammation of the middle ear, since the infection easily gets there through a short and wide auditory tube. This should be remembered in the treatment of colds in children, as well as in the organization of physical education classes, especially on the basis of water pools, in winter sports, and the like. Around the openings of the mouth, nose and eustachian tubes in the pharynx are nodes designed to protect the body from pathogens that can enter the mouth and throat with the air that is inhaled, or with food or water consumed. These formations are called adenoids or tonsils (tonsils).

From the nasopharynx, air enters the larynx, which consists of cartilage, ligaments and muscles. The cavity of the larynx from the side of the pharynx when swallowing food is covered with elastic cartilage - the epiglottis, which prevents food from entering the respiratory tract. In general, the larynx in children is shorter than in adults. This organ grows most intensively in the first 3 years of a child's life, and during puberty. In the latter case, gender differences are formed in the structure of the larynx: in boys, it becomes wider (especially at the level of the thyroid cartilage), the Adam's apple appears and the vocal cords become longer, which causes the final voice to be brittle and form a lower voice in men.

The trachea departs from the lower edge of the larynx, which further branches into two bronchi, which supply air in accordance with the left and right lung. The mucous membrane of the tracts of children (up to 15-16 years old) is very vulnerable to infections due to the fact that it contains fewer mucous glands and is very tender.

The functional indicators include primarily the type of breathing. Children under 3 years of age have a diaphragmatic type of breathing. From 3 to 7 years, all children develop a chest type of breathing. From the age of 8, sexual characteristics of the type of breathing begin to appear: in boys, the belly gradually develops - the diaphragmatic type of breathing, and in girls the thoracic type of breathing improves. The consolidation of such differentiation is completed at the age of 14-17. It should be noted that the type of breathing may vary depending on physical activity. With intensive breathing, not only the diaphragm, but also the chest begins to work actively in the guys, and in the girls, the diaphragm is activated along with the chest.

The second functional indicator of respiration is the respiratory rate (the number of breaths or exhalations per minute), which decreases significantly with age.

The human respiratory organs are very important for the life of the body, as they supply oxygen to tissues and remove carbon dioxide from them. The upper respiratory tract includes the nasal passages that reach the vocal cords, and the lower respiratory tract includes the bronchi, trachea and larynx. At the time of the birth of a child, the structure of the respiratory system is not yet fully developed, which makes up the features of the respiratory system in infants.

By the time of the birth of a child, his nervous system, compared with other organs and systems, is the least developed and differentiated. At the same time, great demands are placed on this system, since it ensures the adaptation of the organism to the conditions of the new external environment and regulates the vital functions of a newborn child.

In the process of adaptation, metabolism should be established, the work of the respiratory, circulatory, and digestive organs should be reorganized. All these systems after the birth of a child begin to function in a new way. It is the nervous system that should ensure the coordinated activity of these organs.

In a newborn, the weight of the brain is relatively large, accounting for 1/8 - 1/9 of the body weight, while in an adult, the brain is 1/40 of the body weight. During the first 6 months of life, the weight of the brain increases by 86.3%. In the period from 2 to 8 years, the growth of the brain slows down and subsequently its weight changes slightly.

The brain tissue of a child is rich in water, contains little lecithin and other specific protein substances. Furrows and convolutions are poorly expressed, the gray matter of the brain is poorly differentiated from the white matter. After birth, the development of the shape, size of the furrows and convolutions continues: the furrows become deeper, the convolutions become larger and longer. This process is especially vigorous in the first 5 years, which leads to an increase in the total surface of the cerebral hemispheres. The process of maturation of nerve cells in different parts of the brain is carried out unequally vigorously: for cortical cells, it ends by 18-20 months. IN medulla oblongata this process is completed by the age of 7. Around this age, myelination of nerve fibers ends.

The spinal cord at the time of the birth of the child is more complete in its structure. It is relatively longer than in an adult (therefore, spinal functions in children are performed in the III-IV interlumbar space).

Because the bark pyramidal pathways, the striatum by the birth of a child is underdeveloped, all vital functions in a newborn, they are regulated by the interstitial brain, subcortical centers.

From the moment of birth, a full-term baby has a number of congenital, or unconditioned, reflexes. These include sucking, swallowing, blinking, coughing, sneezing, defecation, urination, and some others. The vital role of these reflexes is indisputable - they carry out the adaptation of the organism to the environment and by the end of the first year of life undergo rapid and significant evolution.

Based on the indicated unconditioned reflexes the child develops conditioned reflexes that are of primary importance in human life, in other words, the first signal system develops.

The development of higher nervous activity, i.e. the acquisition of conditioned reflexes proceeds at a very rapid pace. A child is much easier than an adult to form conditional connections with the external environment. These connections are stable and bright. This means that the child can relatively quickly acquire certain behavioral skills, habits, which then remain for a long time, often for life.

The development of a child's complex behavior is closely related to a certain level of development of the sense organs, as peripheral perceived organs. The child has a well-developed taste, he distinguishes between bitter sweet medicines, he drinks sweet mixtures more willingly. The sense of smell is worse developed, however, the child distinguishes some sharp smells. The sense of touch is quite well developed, for example, touching the lips causes a sucking movement. The skin of the face, palms and soles is most sensitive to touch. The most difficult is the development of hearing and vision. From the moment of birth, the child sees and hears, but his perception is not clear. Auditory receptors in a newborn are sufficiently developed and he reacts to strong sound stimuli with a shudder.

A huge role in the behavior of the child is played by speech - the second signaling system. The formation of children's speech occurs according to the laws of the formation of conditioned reflexes and goes through several stages. At 2-3 months, the child usually "gurgles" - these are speech noises, the germ of future words. In the second half of the year, speech begins to form. The child begins to pronounce individual syllables, and sometimes repeated syllables have a certain meaning. By the age of one, children usually know 5-10 words. In the 2-3rd year of life, the development of speech is especially rapid and intensive. By 2 years lexicon child should be 200 words. Speech, arising on the basis of the first signal system and being closely connected with it, becomes the leading link in the child's later developing nervous activity. With the development of speech, the child's knowledge of the world around him goes unusually quickly and rapidly.

The cardiovascular system

The heart and blood vessels in a child are significantly different from the heart vascular system adult. After birth, the functional state of the circulatory organs changes especially sharply. With the ligation of the umbilical cord, the placental circulation stops. With the first breath, the blood vessels of the lungs expand, their resistance to blood flow is greatly reduced. The filling of the lungs with blood through the pulmonary artery increases dramatically. The pulmonary circulation begins to function. Then comes the complete cessation of communication between the left and right halves of the heart, and as a result, the separation of the small and great circle circulation. At the same time, new conditions are being created for the development of the cardiovascular system.

The heart of a newborn is relatively large, it weighs 20-25 g, which is 0.8% of the total body weight. The heart grows most vigorously in the first 2 years of life. In preschool and primary school age, it slows down.

The position of the heart depends on its age. In newborns and children of the first 1-2 years of life, the heart is located transversely and higher. After two years, the heart begins to take on an oblique position. This is due to the transition of the child to a vertical position, the growth of the lungs and chest, the lowering of the diaphragm, etc.

The shape of the heart in infancy and early age can be oval, cone-shaped, spherical. After 6 years, the child's heart takes on the shape characteristic of adults, most often an elongated oval.

The arteries in children are relatively wide and more developed than the veins. The ratio of the lumen of the artery to the lumen of the veins in childhood is 1:1, while in adults it is 1:2. of the large vessels, the pulmonary trunk in children under the age of 10 is wider than the aorta, then their lumen equalizes, and during puberty, the aorta exceeds the pulmonary trunk in width.

Consequently, the cardiovascular system in children is characterized by a relatively large mass of the heart, a large width of the holes and a wider lumen of the vessels, which greatly facilitates blood circulation.

Children have distinctive features in the functions of the cardiovascular system. The pulse in children is more frequent than in adults, and the pulse rate is higher, the younger the child. This is due to the prevailing influence sympathetic innervation, while cardiac branches vagus nerve much less developed. With age, there is a gradual increase in the role of the vagus nerve in the regulation of cardiac activity and this is expressed in a slowing of the pulse in children.

Blood pressure in children is lower than in adults. This is explained by the large width of the lumen of the vascular system, the great compliance of the vascular walls and the lower pumping capacity of the heart. In a newborn, the maximum pressure averages 70-74 mm Hg. Art. and by the year of life it becomes equal to 80-85 mm Hg. Art.

Blood pressure in children is also characterized by great lability. With the horizontal position of the child, especially in sleep, it decreases, physical activity and mental experiences cause it to increase.

Blood circulation in newborns takes place almost twice as fast as in an adult; one blood circulation occurs in newborns in 12 seconds; in a child of 3 years - in 15 seconds; in an adult - in 22 seconds.

So, the child's body is always in the process of growth and development, which take place continuously in a certain regular sequence. From the moment of birth to an adult, a child comes through certain age periods. child in different periods life is characterized by certain anatomical and physiological features, the totality of which leaves an imprint on the reactive properties of the body's resistance. Human life is a continuous process of development. The first steps and further development of motor function, the first words and the development of speech function, the transformation of a child into a teenager during puberty, continuous development central nervous system, the complication of reflex activity - these are just examples of a huge number of continuous changes in the body. The child's organism develops in specific environmental conditions, continuously operating the course of its development. More I.M. Sechenov noted that “... an organism without an external environment that supports its existence is impossible, therefore, the scientific definition of an organism should also include an environment that affects it, and since the existence of an organism is impossible without the latter, then disputes about what is more important in life - the environment or the body itself - do not have the slightest meaning. Depending on the specific environmental conditions, the development process can be accelerated or slowed down, and its age periods can come earlier or later and have different durations.

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Age features of the respiratory system.

breathing age hygienic air

Fetal respiration. Respiratory movements in the fetus occur long before birth. The stimulus for their occurrence is a decrease in the oxygen content in the blood of the fetus.

Breath of a newborn.The occurrence of the first breath of a newborn is due to a number of reasons. After the umbilical cord is ligated, the placental exchange of gases between the blood of the fetus and the mother stops in the newborn. This leads to an increase in the content of carbon dioxide in the blood, which irritates the cells of the respiratory center and causes rhythmic breathing.

The mechanism of the act of breathing in a newborn.Features of the child's breathing are associated with the structure and development of his chest. In a newborn, the chest has a pyramidal shape, by the age of 3 it becomes cone-shaped, and by the age of 12 it is almost the same as in an adult. Newborns have an elastic diaphragm, its tendon part occupies a small area, and the muscular part occupies a large one. As it develops, the muscular part of the diaphragm increases even more. It begins to atrophy from the age of 60, and instead of it, the tendon part increases. Since infants are mainly diaphragmatic breathing, during inspiration, the resistance of the internal organs located in the abdominal cavity must be overcome. In addition, when breathing, one has to overcome the elasticity of the lung tissue, which in newborns is still large and decreases with age. It is also necessary to overcome bronchial resistance, which in children is much greater than in adults. Therefore, the work expended on breathing is much greater in children than in adults.

Change with age in the type of breathing.Diaphragmatic breathing persists until the second half of the first year of life. As the child grows, the chest descends and the ribs take on an oblique position. At the same time, mixed breathing (chest-abdominal) occurs in infants, and stronger mobility of the chest is observed in its lower sections. In connection with the development of the shoulder girdle (3-7 years), chest breathing begins to predominate. From 8 to 10 years, there are gender differences in the type of breathing: in boys, a predominantly diaphragmatic type of breathing is established, and in girls - chest.

Change with age in the rhythm and frequency of breathing.In newborns and infants, breathing is irregular. Arrhythmia is expressed in the fact that deep breathing is replaced by shallow breathing, pauses between inhalations and exhalations are uneven. The duration of inhalation and exhalation in children is shorter than in adults: inhalation is 0.5 - 0.6 s (in adults - 0.98 - 2.82 s), and exhalation - 0.7 - 1 s (in adults - from 1.62 to 5.75 s). Already from the moment of birth, the same ratio between inhalation and exhalation is established as in adults: inhalation is shorter than exhalation.

Change with age in respiratory and minute volumes lungs, their vital capacity.In a newborn child, the lungs are malelastic and relatively large. During inspiration, their volume increases slightly, by only 10 - 15 mm. Providing the child's body with oxygen occurs by increasing the frequency of breathing. The tidal volume of the lungs increases with age, along with a decrease in the respiratory rate.

With age, the absolute value of MOD increases, but the relative MOD (ratio of MOD to body weight) decreases. In newborns and children of the first year of life, it is twice as large as in adults. This is due to the fact that in children with the same relative tidal volume, the respiratory rate is several times greater than in adults. In this regard, pulmonary ventilation per 1 kg of body weight in children is greater (in newborns it is 400 ml, at 5-6 years of age it is 210, at 7 years of age - 160, at 8 - 10 years of age - 150, 11 - 13-year-olds - 130 - 145, 14-year-olds - 125, and 15 - 17-year-olds - 110). This provides a large need for a growing organism in O 2 .

Age features of the respiratory system.Children under 8-11 years of age have an underdeveloped nasal cavity, swollen mucous membrane and narrowed nasal passages. This makes it difficult to breathe through the nose and therefore children often breathe with their mouth open, which can contribute to colds, inflammation of the pharynx and larynx. In addition, constant mouth breathing can lead to frequent otitis media, bronchitis, dry mouth, abnormal development of the hard palate, disruption of the normal position of the nasal septum, etc. and to the narrowed nasal passages in children, further complicates their breathing through the nose. Therefore, colds in children require quick and effective treatment, especially since the infection can enter the cavities of the bones of the skull, causing corresponding inflammation of the mucous membrane of these cavities and the development of chronic rhinitis. From the nasal cavity, air enters through the choanae into the pharynx, where the oral cavity (calling), auditory (Eustachian canals) tubes also open, and the larynx and esophagus originate. In children under 10-12 years old, the pharynx is very short, which leads to the fact that infectious diseases of the upper respiratory tract are often complicated by inflammation of the middle ear, since the infection easily gets there through a short and wide auditory tube. This should be remembered in the treatment of colds in children, as well as in the organization of physical education classes, especially on the basis of water pools, in winter sports, and the like. Around the openings of the mouth, nose and eustachian tubes in the pharynx are nodes designed to protect the body from pathogens that can enter the mouth and throat with the air that is inhaled, or with food or water consumed. These formations are called adenoids or tonsils (tonsils).

From the nasopharynx, air enters the larynx, which consists of cartilage, ligaments and muscles. The cavity of the larynx from the side of the pharynx when swallowing food is covered with elastic cartilage - the epiglottis, which prevents food from entering the respiratory tract.The vocal cords are also located in the upper part of the larynx.In general, the larynx in children is shorter than in adults. This organ grows most intensively in the first 3 years of a child's life, and during puberty. In the latter case, gender differences are formed in the structure of the larynx: in boys, it becomes wider (especially at the level of the thyroid cartilage), the Adam's apple appears and the vocal cords become longer, which causes the final voice to be brittle and form a lower voice in men.

The trachea departs from the lower edge of the larynx, which further branches into two bronchi, which supply air in accordance with the left and right lungs. The mucous membrane of the tracts of children (up to 15-16 years old) is very vulnerable to infections due to the fact that it contains fewer mucous glands and is very tender.

The state of external respiration is characterized by functional and volume indicators.The functional indicators include primarily the type of breathing. Children under 3 years of age have a diaphragmatic type of breathing. From 3 to 7 years, all children develop a chest type of breathing. From the age of 8, sexual characteristics of the type of breathing begin to appear: in boys, the belly gradually develops - the diaphragmatic type of breathing, and in girls the thoracic type of breathing improves. The consolidation of such differentiation is completed at the age of 14-17. It should be noted that the type of breathing may vary depending on physical activity. With intensive breathing, not only the diaphragm, but also the chest begins to work actively in the guys, and in the girls, the diaphragm is activated along with the chest.

The second functional indicator of respiration is the respiratory rate (the number of breaths or exhalations per minute), which decreases significantly with age.

Analysis of the age characteristics of two organ systems: the nervous system and the cardiovascular system in children.

The brain tissue of a child is rich in water, contains little lecithin and other specific protein substances. Furrows and convolutions are poorly expressed, the gray matter of the brain is poorly differentiated from the white matter. After birth, the development of the shape, size of the furrows and convolutions continues: the furrows become deeper, the convolutions become larger and longer. This process is especially vigorous in the first 5 years, which leads to an increase in the total surface of the cerebral hemispheres. The process of maturation of nerve cells in different parts of the brain is carried out unequally vigorously: for cortical cells, it ends by 18-20 months. In the medulla oblongata, this process is completed by the age of 7. Around this age, myelination of nerve fibers ends.

Since the cortex, pyramidal tracts, striatum are not sufficiently developed by the birth of a child, all vital functions in a newborn are regulated by the interstitial brain, subcortical centers.

On the basis of these unconditioned reflexes, the child develops conditioned reflexes that are of primary importance in human life, in other words, the first signal system develops.

A huge role in the behavior of the child is played by speech - the second signaling system. The formation of children's speech occurs according to the laws of the formation of conditioned reflexes and goes through several stages. At 2-3 months, the child usually "gurgles" - these are speech noises, the germ of future words. In the second half of the year, speech begins to form. The child begins to pronounce individual syllables, and sometimes repeated syllables have a certain meaning. By the age of one, children usually know 5-10 words. In the 2-3rd year of life, the development of speech is especially rapid and intensive. By the age of 2, a child's vocabulary should consist of 200 words. Speech, arising on the basis of the first signal system and being closely connected with it, becomes the leading link in the child's later developing nervous activity. With the development of speech, the child's knowledge of the world around him goes unusually quickly and rapidly.

The cardiovascular system

The heart and blood vessels in a child are significantly different from the cardiovascular system of an adult. After birth, the functional state of the circulatory organs changes especially sharply. With the ligation of the umbilical cord, the placental circulation stops. With the first breath, the blood vessels of the lungs expand, their resistance to blood flow is greatly reduced. The filling of the lungs with blood through the pulmonary artery increases dramatically. The pulmonary circulation begins to function. Then comes the complete cessation of communication between the left and right halves of the heart, and as a result, the separation of the small and large circles of blood circulation. At the same time, new conditions are being created for the development of the cardiovascular system.

The shape of the heart in infancy and early age can be oval, cone-shaped, spherical. After 6 years, the child's heart takes on the shape characteristic of adults, most often an elongated oval.

Children have distinctive features in the functions of the cardiovascular system. The pulse in children is more frequent than in adults, and the pulse rate is higher, the younger the child. This is due to the prevailing influence of sympathetic innervation, while the cardiac branches of the vagus nerve are much less developed. With age, there is a gradual increase in the role of the vagus nerve in the regulation of cardiac activity and this is expressed in a slowing of the pulse in children.

So, the child's body is always in the process of growth and development, which take place continuously in a certain regular sequence. From the moment of birth to an adult, a child comes through certain age periods. A child in different periods of life is characterized by certain anatomical and physiological features, the totality of which leaves an imprint on the reactive properties of the body's resistance. Human life is a continuous process of development. The first steps and the further development of motor function, the first words and the development of speech function, the transformation of a child into a teenager during puberty, the continuous development of the central nervous system, the complication of reflex activity - these are just examples of a huge number of continuous changes in the body. The child's organism develops in specific environmental conditions, continuously operating the course of its development. More I.M. Sechenov noted that “... an organism without an external environment that supports its existence is impossible, therefore, the scientific definition of an organism should also include an environment that affects it, and since the existence of an organism is impossible without the latter, then disputes about what is more important in life - the environment or the body itself - do not have the slightest meaning. Depending on the specific environmental conditions, the development process can be accelerated or slowed down, and its age periods can come earlier or later and have different durations.

Modern ideas about the development of the respiratory system in ontogeny are based on numerous studies carried out in our country and abroad. In many works, their dependence on anthropometric indicators has been studied. The dynamics of morphological transformations of the lungs in human ontogeny has been considered in a number of studies.

The respiratory system is one of the leading and largely determining both mental and physical performance. A close relationship between the formation of the respiratory system and the physical development and maturation of other physiological systems of the body was noted. Given that the process of puberty affects the age-related development in general, its influence on the nature of the age-related transformations of the respiratory system of a teenager is noted.

The respiratory system of a person in different age periods has not only quantitative, but also qualitative differences. They are based on the processes of continuous development of morphological structures and functional processes.

Most researchers assign a significant role in the development of respiratory function to the following periods: newborns, up to 1 year, from 5 to 7 years and from 11 to 12 years, when the greatest quantitative changes in the parameters of the studied function are noted.

Respiration is a process of constant exchange of gases between the body and the environment, necessary for life. The exchange of gases between atmospheric air and the air in the alveoli occurs due to the rhythmic alternation of inhalation and exhalation. The gradual maturation of the musculoskeletal apparatus of the respiratory system and the peculiarities of its development in boys and girls determine the age and sex differences in the types of breathing. In newborns, diaphragmatic breathing predominates with little involvement of the intercostal muscles. The breathing of infants is thoracoabdominal, with diaphragmatic predominance. At the age of 3 to 7 years, the chest type of breathing begins to predominate, and by the age of 7 it becomes pronounced. At the age of 7-8 years, positive differences in the type of breathing are revealed: in boys, the abdominal type of breathing prevails, in girls - chest. The sexual differentiation of respiration ends by the age of 14-17. The type of breathing in boys and girls can vary depending on sports, work activities. Farber D.A. and Kozlov V.I. emit mixed breathing in newborns.

Age-related features of the structure of the chest and muscles determine the features of the depth and frequency of breathing in childhood. The volume of air entering the lungs in one breath characterizes the depth of breathing. The number of breaths in children per minute (according to A.F. Tour): From 7 to 12 years - 30-35, from 2 to 3 years - 25-30, from 5 to 6 years - about 25, from 10 to 12 years - 20-22\, from 14 to 15 years old - 18-20

Until the age of 8, boys have a higher respiratory rate than girls. Before puberty, the respiratory rate in girls is greater, and in the future this ratio is maintained throughout life. The respiratory center in children is easily excitable. Breathing in children increases significantly with mental excitations, small physical exercises, a slight increase in t 0 of the body and the environment.

The high frequency of respiratory movements in the child provides high pulmonary ventilation. The volume of inhaled air in children at the age of 10 is 239 ml, at 14 years is 300 ml. Due to the high respiratory rate in children, the minute volume of breathing (in terms of 1 kg of weight) is much higher than in adults. At 6 years old it is 3500 ml, at 10 years old - 4300 ml, at 14 years old - 4900 ml, in an adult - 5000-6000 ml.

An important characteristic of the functioning of the respiratory system is the vital capacity of the lungs - the maximum amount of air that a person can exhale after a deep breath. VC changes with age (table - see below) depends on body length, the degree of development of the chest and respiratory muscles, gender. VC is an important indicator of physical development. By the age of 16-17, VC reaches values characteristic of adults.

Average VC (in ml)

A person can arbitrarily regulate the frequency and depth of breathing, hold the breath. But holding the breath cannot be too long, since CO 2 accumulates in the blood of a person who has held his breath, and when its concentration reaches a superthreshold level, the respiratory center is excited and breathing resumes against the will of the person. Since the excitability of the respiratory center is different for different people, the duration of an arbitrary breath holding is different for them. The breath holding time can be lengthened if the lungs are hyperventilated (several frequent and deep breaths and exhalations within 20-30 0 C).

During hyperventilation, CO 2 is “washed out” of the blood, and the time it takes to accumulate to a level that excites the respiratory center increases. This allows, after hyperventilation of the lungs, to hold the breath for significantly more time. During hyperventilation and breath holding in the exhaled air, the content of CO 2 changes significantly and the content of O 2 almost does not change. Therefore, the humoral factor that excites the respiratory center and affects the duration of breath holding is CO 2 .

In modern physiology, voluntary breath holding is used to study the voluntary regulation of breathing, while the duration of the test serves as a measure of a person's ability to voluntarily control breathing. It is used to determine the individual characteristics of the regulation of breathing. Of the various options for conducting arbitrary breath holding, the Stange test is widely used - holding the breath, carried out at the height of a normal inhalation and the Gench test - holding the breath, carried out at the height of a normal exhalation.

When holding the breath, the conditioned reflex is quickly consolidated for a time than during normal breathing. Individual features of reactions are due to unequal sensitivity to humoral (hypercapnia and hypoxia), neurogenic and mechanical factors that arise during the test and placement in the mechanisms of these reactions.

To characterize the functional state of the cardiovascular system and respiratory systems, another method is used - determination by the Rufier test. This test is the most objective and simple criterion for assessing the interaction between the SS and the respiratory systems.

Age features of the cardiovascular system

The effectiveness of training and education of the younger generation depends on how much the adaptive capabilities of schoolchildren at different stages of individual development are taken into account, when periods of greatest susceptibility are replaced by periods of reduced resistance to environmental factors.

The development of all body systems places increased demands on the CVS as a life support system. It is the activity of the CCC that is one of the most important factors limiting the development of adaptive reactions of a growing organism in the process of its adaptation to the conditions of education and upbringing of the blood in a child of 6-16 years old up to 7%, i.e. 1 kg of body weight accounts for approximately 70 g of blood. Usually in children older than one year, many hematological parameters approach the values characteristic of an adult organism.

In children, the relative mass of the heart and the total lumen of the vessels are greater than in adults, which greatly facilitates the processes of blood circulation. The growth of the heart is closely related to the overall growth of the body. The most intensive growth of the heart is observed in the first years of development and at the end of adolescence (Kalyuzhnaya. Functional differences in the cardiovascular system of children and adolescents persist up to 12 years. The heart rate in children is greater than in adults, which is associated with the predominance of the tone of sympathetic centers in children according to compared with the vagus nerves.In the process of postnatal development, the tonic effect on the heart of the vagus nerve gradually increases.Delay in the formation of the tonic effect of the vagus nerve on cardiovascular activity may indicate a delay in the physical development of the child.The tone of the vagus nerve increases with age, especially in well-developed children and teenagers.

Heart rate is usually measured by pulse, since each release of blood into the vessels leads to a change in their blood supply, stretching of the vascular wall, which is felt as a push, the highest pulse rate is observed in newborns, in whom the number of heart contractions is 120-140 per minute, and to 12-13 years old - 75-80 beats / min. By the age of 15, this value approaches that of adults and is 65-75 beats / min.

The integral criterion of the state of blood circulation - the level of arterial pressure was not studied in our work. In general, it should be noted that blood pressure in children is much lower than in adults. The smaller the child, the larger the capillary network and the wider the lumen of the blood vessels, and consequently, the lower the blood pressure. It should also be mentioned that the age of 9-10 years should be considered as a turning point in the development of CVS, because. during this period, the direction of age-related changes in blood pressure indicators in boys and girls is opposite. With the end of puberty in girls (14-15 years old) and boys (15-16 years old), the values of hemodynamic parameters are set at the level characteristic of adults.

In general, the activity of the entire circulatory system is aimed at providing the body in various conditions with the necessary amount of O 2 and nutrients, at removing metabolic products from cells and organs, and at maintaining a constant level of blood pressure. This creates conditions for maintaining the constancy of the internal environment of the body.

The physiology of the development of the cardiovascular system in a growing organism is characterized by a gradual economization of the function, which is expressed as the child grows and develops in a decrease in the heart rate, an increase in the power of the contractile myocardium.

Age-related changes in the blood system.

Blood is an intermediate internal environment that is in the vessels and does not come into direct contact with most cells of the body. However, blood and lymph, being in continuous motion, ensure the constancy of the composition and properties of the tissue fluid.

The most important function of blood is respiratory, i.e. It delivers oxygen to cells and removes carbon dioxide from them. The enrichment of blood with oxygen occurs through the thinnest walls of the epithelial cells of the capillaries surrounding the pulmonary vesicles; In the same place, the blood gives off carbon dioxide, which is removed into the environment with exhaled air. Flowing through the capillaries of various tissues and organs, blood gives them oxygen and absorbs carbon dioxide.

Blood, being in constant motion, performs a transport function in the body. With blood, various nutrients are transferred from the digestive organs to the tissues: amino acids, glucose, fats, minerals: substances, vitamins. They are assimilated by various tissues, cells of the body, and their excess is deposited in the reserve. This is how the nourishing function of the blood is carried out.

Blood carries the metabolic products of urea, uric acid, etc. from the place of formation to the place of their excretion from the body, so the blood participates in the excretory function of the body. Blood transports hormones (secrets of endocrine glands) and other physiologically active substances and carries out humoral regulation of body functions.

Due to the fact that there is a lot of water in the blood, and it has a high thermal conductivity and specific heat capacity, the importance of blood in raising or lowering, in maintaining a constant temperature of heat is a thermoregulatory function. The protective function of the blood is special, since everything connected with the activity of the blood has a protective value for the body. Blood protects the cells of a living organism from the harmful effects of excessively strong fluctuations in environmental conditions. Blood clotting, due to its plasma proteins and platelets, protects against blood loss. This function also includes protecting the body from foreign substances: proteins of bacteria, viruses, various toxins. Antibodies are produced against them in the body. The protective function depends on the activity of leukocytes, which have the ability to absorb and digest foreign substances. Leukocytes are also involved in the formation of antibodies, i.e. in creating immune properties of blood.

The amount of blood in the human body changes (I age. In children, blood, relative to body weight, is greater than in adults (Table 1). In terms of 1 kg of body weight, there are 150 ml in newborns, in 6-11-year-olds - 70 ml, and in adults - 50 ml.This is due to a more intense metabolism in the child's body.In adults weighing 60-70 kg, the total amount of blood is 5-5.5 liters.

The amount of blood in children and adolescents

Important in maintaining the relative constancy of the composition and amount of blood in the body is its reservation in special blood depots. This function is performed by the spleen, liver, lungs, skin, subcutaneous layers, where up to 50% of the blood is reserved. For example, up to 1 liter of blood can be stored in the blood vessels of the skin.

In those cases when a lack of oxygen occurs in the human body - with increased muscular work, with the loss of large amounts of blood during injuries and surgical operations, and some diseases - blood supplies from the depot enter the general circulation. Loss of 50% of blood is fatal.

Blood is the fluid connective tissue of the body. It consists of formed elements (blood cells) and plasma (the liquid part of blood). The red blood cells are the formed elements of blood. blood cells- erythrocytes, white blood cells - leukocytes and platelets - platelets. In an adult, they make up 45% of the blood volume, and 55% of the volume is plasma. The children have shaped elements in the blood more and percent. In infants, 55-50% of formed elements, 45-50% - plasma, in children of primary school age - 50% to 50%. The blood plasma contains 90-92% water, 8-10% is dry matter. Of these, 6.5-8.2% are proteins and only 2% are all other organic and inorganic substances. Plasma inorganic substances are chlorides, phosphates, carbonates and sulfites of sodium, potassium, calcium and magnesium. Organic substances include proteins: albumins, globulins, fibrinogen and prothrombin, amino acids, urea, uric acid, glucose and other substances.

Erythrocytes. The most numerous formed elements of blood are erythrocytes - red blood cells. They are non-nuclear, biconcave. This form increases their surface by more than 1.5 times and provides faster and more uniform diffusion of oxygen into the erythrocytes, which contributes to a better performance of the transport function of the blood. Young erythrocytes have nuclei, but in the process of maturation, the nuclei disappear, which ensures more economical work of erythrocytes.

1 cubic mm of blood contains 4-5 million erythrocytes (for men, 4.5-5 million, and at women 4-4.5 million). So the total number of them is huge. It is estimated that the sum of the surfaces of all red blood cells of one person is 1500 times the surface of his body. The number of red blood cells is not strictly constant. It can increase significantly with a lack of oxygen for high altitudes during muscular work. When the need for oxygen decreases, the number of red blood cells in the blood decreases. The content of red blood cells also changes with the age of the child.

In children of 6-10 years of age, their number ranges from 4.1-6.4 million per 1 ml of blood. In children, not only the number, but also the size of red blood cells changes. Thus, the diameter of erythrocytes in children ranges from 3.5 to 10 microns, while in adults it is 6-9 microns. Approximately by the age of 9-10, i.e. by the end of the period of primary school age, both the shape and size of erythrocytes become the same as in adults.

A large number of red blood cells characteristic of children makes the blood of children more viscous and thick. The implementation of the respiratory function by erythrocytes is associated with the presence in them of a special substance - hemoglobin, which is an oxygen carrier. This substance contains a protein-globin and a non-protein substance - heme, which contains ferrous iron. Thanks to this compound, hemoglobin in the capillaries of the lungs combines with oxygen and forms oxyhemoglobin. This substance has a bright red color, and the blood containing oxyhemoglobin is called arterial. In tissue capillaries, oxyhemoglobin breaks down into free oxygen and hemoglobin. The latter combines with carbon dioxide to form carbhemoglobin. This substance is dark red in color. The blood is called venous.

Leukocytes colorless nuclear cells of various shapes are called. In an adult, 1 cubic mm of blood contains 6-8 thousand leukocytes. According to the shape of the cell and nucleus, they are divided into lymphocytes, monocytes, neutrophips, eosinophils and basophils.

Lymphocytes are produced in lymph nodes and, by producing antibodies, are involved in the formation of the body's immune properties. They occupy an important place in ensuring the protection of the body from foreign formations.

Neutrophils are produced in the red bone marrow. These are the most numerous leukocytes and play a major role in phagocytosis. The absorption and digestion by leukocytes of various microbes, protozoa, foreign substances that enter the body is called phagocytosis, and the leukocytes themselves are called phagocytes. The phenomenon of phagocytosis would have been studied by well-known Russian scientists. I.I. Mechnikov. One neutrophil can absorb 20-30 microbes. After an hour, all of them are digested inside the neutrophil. Capable of phagocytosis and monocytes - cells formed in the spleen and liver. There is a certain ratio between different types of leukocytes, expressed as a percentage of the so-called leukocyte formula.

In pathological conditions, both the total pure leukocytes and the leukocyte formula change.

The number of leukocytes and their ratio change with age. A newborn has significantly more leukocytes than an adult (up to 20,000 per 1 ml of blood. On the first day of life, the number of leukocytes increases (resorption of decay products of the baby’s tissues, tissue hemorrhages that are possible during childbirth) up to 30,000 per 1 ml of blood The largest number of leukocytes in children at 2-3 months, and then it gradually decreases in waves and reaches the level of adults by the age of 13-15. The younger the child, the more blood contains immature forms leukocytes.

The blood of a child in the first years of life contains more lymphocytes and a reduced number of neutrophils. By the age of 5-6, their number levels off, then the number of neutrophils increases rapidly, and the number of lymphocytes decreases. Low in early periods life and phagocytic function of neutrophils. All this explains the great susceptibility of young children to infectious diseases. On the other hand, frequent colds lead to the death of a large number of leukocytes, especially neutrophils.

An increase in the total number of leukocytes in the blood is called leukocytosis, and a decrease is called leukopenia. Unlike erythrocytes, the content of leukocytes in the blood fluctuates dramatically. Leukocytosis is observed in a painful condition, during muscular work, after eating. Leukopenia is observed with ionizing radiation. In most children under 12 years of age, the study load causes leukocytosis, especially an increase in the number of lymphocytes. Although younger schoolchildren have more leukocytes in their blood than older children and adults, their mobility and phagocytic activity are lowered. Consequently, in younger schoolchildren, the ability of the blood to form specific protective cells is also reduced, and this increases the susceptibility of children to infectious diseases.

platelets or platelets - very small, irregularly shaped blood cells. The number of platelets in 1 ml of blood ranges from 200 thousand to 400 thousand. There are more of them during the day, less at night. Muscular work increases their amount in the blood, because. platelets are intensively ejected into the blood from the depot, namely from the spleen, and also due to increased hematopoiesis. Eating proteins and fats and the process of digestion cause a decrease in the number of platelets in the blood. The same phenomenon is observed with a lack of vitamins of groups A and B in food and after ionizing radiation. Children have fewer platelets than adults.

It was found that any kind of load, including mental, leads to an increase in the number of platelets and a decrease in blood clotting time. For example, in boys, after 40 squats, platelets increase by 13.3%, in girls - by 8.7%. In general, 7-10 year old boys have 12-13% more platelets than girls, but the blood clotting time is shorter in girls. All these changes and differences are mainly due to the higher motor skills of boys.

Platelets are formed in the red bone marrow and spleen. Their main function is to ensure blood clotting. Platelets contain the active enzyme fibrinaea, which is involved in the conversion of the fibrinogen protein (dissolved in the blood) into fibrin - a thrombus necessary for the formation blood clot. During school year in schoolchildren of grades 1-3, there is a decrease in the activity of the most important enzyme - fibrin. Such a decrease in fibrinase activity is especially noted in the second half of the year. Studies show that fibrinase activity can decrease by 4 times by the end of the school year. These data apparently reflect shifts in the metabolic processes of cells and tissues that occur as elementary school students adapt to the learning load.

Blood coagulation in children in the first days after birth is slow, this is especially noticeable in the first days of a child's life. From the 3rd to the 7th day of life, blood clotting accelerates and approaches the norm for adults. In children of preschool and school age, blood clotting time has wide individual fluctuations. On average, the onset of coagulation in a drop of blood occurs in 1-2 minutes; the end of coagulation - after 3-4 minutes. This feature must always be taken into account when organizing the educational process, especially when organizing excursions, when conducting physical education lessons, labor, etc., since students can lose a large amount of blood when injured.

Hematopoiesis. In an adult, hematopoiesis occurs in red bone marrow skull, sternum, ribs, vertebrae, pelvis and epiphyses of tubular bones. Lymphocytes are produced in the spleen and lymph nodes. In children, the restoration of blood cells occurs much faster than in adults. The ratio of various formed elements of the blood during the development of the child periodically changes. The frequency of these changes coincides with the frequency in relation to the activity of the hematopoietic organs: the bone marrow, spleen and liver, which are in the closest relationship due to the nervous system.

The bone marrow has a dual function. On the one hand, it takes part in the process of growth and development of bone tissue, and on the other hand, it is a hematopoietic organ. Already in the first year of life, the replacement of part of the red bone marrow with fat begins. During periods of increased growth of the body, the bone marrow is in a state of tension due to the large demands placed on it, associated with intensive growth and hematopoiesis. And during periods of especially rapid growth or during severe, prolonged illnesses in children, the bone marrow does not keep up with hematopoiesis. And then the hematopoietic function is partially taken over by the liver, sometimes the yellow bone marrow temporarily passes into the red bone marrow. But after recovery, it turns back into yellow bone marrow. With age, the intensity of the formation of blood cells gradually decreases.