Development of the cardiovascular system. Development and age-related features of the cardiovascular system: how the heart and blood vessels change over time Features of the functioning of the cardiovascular system

10.The increase in the mass of which part of the heart predominates in the process of its growth in a child? By what age does a child's heart acquire the main structural parameters of an adult's heart?

The mass of the left ventricle increases. This can be explained by the fact that the load on the left and right ventricles in the fetus is approximately equal, and in the postnatal period, the load on the left ventricle significantly exceeds the load on the right ventricle. By the age of 7, a child's heart acquires the basic structural parameters of an adult's heart.

11. How does the heart rate (HR) change in children of different age groups?

With age, heart rate (pulse) gradually decreases. In children of all ages, the pulse is more frequent than in adults. This is due to faster contractility of the heart muscle due to less influence of the vagus nerve and more intense metabolism. In a newborn, the heart rate is much higher - 140 beats / min. The heart rate gradually decreases with age, especially in the first five years of life: in older preschoolers (6 years old) it is 100–105, and in younger schoolchildren (8–10 years old) it is 80–90 beats / min. By the age of 16, the heart rate approaches the value of an adult - 60-80 beats per 1 min. Excitement, an increase in body temperature cause an increase in heart rate in children.

12. What is the heart rate at ages 1 and 7?

At 1 year 120, at 7 years 85 beats/min.

13. How does systolic blood volume change with age?

The amount of blood ejected by the ventricle in one contraction is called shock, or systolic volume (SV). With age, this figure increases. The amount of blood ejected into the aorta by the heart of a newborn with one contraction is only 2.5 ml; by the first year it increases by 4 times, by 7 years - by 9 times, and by 12 years - by 16.4 times. The left and right ventricles at rest push out 60–80 ml of blood in an adult.

14. What is the minute volume of blood in a newborn child, at the age of 1 year, 10 years old and in an adult?

0.5 l; 1.3 l; 3.5 l; 5l respectively.

16.Compare the values ​​of the relative minute volume of blood (ml / kg) in a newborn and in an adult.

Relative minute volume is 150 ml/kg of body weight in a newborn and 70 ml/kg of body weight in an adult, respectively. This is due to a more intense metabolism in the body of a child compared to adults.

15. What are the features of the development of the cardiovascular system in adolescence?

In adolescence, there is an immature blood flow system. There is a jump in the development of the heart: the volume of its chambers annually increases by 25%, the contractile function of the myocardium increases, and the growth of large (main) vessels lags behind the increase in the capacity of the heart chambers, which is manifested by functional disorders of the cardiovascular system (functional heart murmurs). In most cases, these disorders go away. The rapidly growing heart pushes a large volume of blood through narrow blood vessels, resulting in high blood pressure. During this period, dosing of physical activity is required. Adolescents need to engage in physical culture, alternate training loads with outdoor recreation, avoid physical and psycho-emotional overload.

Regulation of the activity of the heart in children

1. 
   What indicates the absence of the inhibitory effect of the vagus nerve on the activity of the heart of a young child?

2.At what age does the tone of the vagus nerve begin to form and when is it sufficiently pronounced?

Starting from 3 - 4 months of a child's life. After 3 years it is expressed.

3. How the frequency and strength of heart contractions change in a teenager under conditions of significant emotional stress?

With emotional stress, there is an excitation of the sympathetic nervous system and a decrease in the tone of the nuclei of the vagus nerves. At the same time, the hormone adrenaline has the greatest importance in the regulation of the activity of the heart. The mechanism of its influence on the body is carried out through beta-adrenergic receptors: the process of energy supply is stimulated in the myocardium, the intracellular concentration of calcium ions increases when cardiomyocytes are excited, and heart contractions increase, heart rate increases.

4. What is the reaction of blood vessels to a high concentration of adrenaline in the blood during psycho-emotional stress in a schoolchild?

High concentrations of adrenaline, for example, with severe psycho-emotional stress, activate alpha and beta-adrenergic receptors of blood vessels. In this case, the vasoconstrictive effect prevails.

5. What factors contribute to the formation of the vagus nerve tone in ontogenesis?

Growth of motor activity and intensification of the flow of afferent impulses from various types of receptors during the development of analyzers.

6. What changes in the mechanism of regulation of the activity of the heart and blood vessels occur during ontogenesis? What is the role of motor activity in the formation of vagal tone in children?

As they grow older, the tone of the vagus nerves increases. In children with limited movement due to one or another congenital defect, the heart rate is high compared to healthy children. In children with high physical activity, the heart rate is lower than in their less physically active peers.

7. How does the reaction of the child's heart to physical activity change with age?

The older the children, the shorter the period during which the heart rate rises to a level corresponding to a given physical activity, the longer the period of increased heart activity, the shorter the recovery time after finishing work.

1. 
   What are the features of the regulation of the activity of the heart and blood vessels in adolescents?

Age-related features of blood circulation

1. How does the pressure in the vessels of the pulmonary circulation in a child change after birth? How does the blood flow through the lungs change after birth?

It sharply decreases due to a decrease in resistance in the vessels of the lungs due to the relaxation of their smooth muscles after a spasm. This increases the tension of O 2 in the tissues of the lungs. The blood flow increases several times.

2. In what age periods are the features of blood circulation most clearly manifested in children?

In the neonatal period, in the first two years of life and during puberty (14-15 years).

3. How does the level of arterial pressure change in ontogenesis? What are the values ​​of systolic and diastolic blood pressure at rest in newborns, at the age of 1 year and in adults.

Increases in ontogeny. 70/34, 90/40, 120/80mmHg Art. respectively.

4. What are the features of blood circulation in the neonatal period?

1) High heart rate due to lack of tone of the nuclei of the vagus nerves; 2) Low blood pressure due to weak peripheral resistance due to the relatively large width of the lumen, high elasticity and low tone of arterial vessels.

100 + (0.5n), where n is the number of years of life.

6. What is the normal systolic pressure in the pulmonary artery in children aged 1 year, 8-10 years old and in an adult?

At the age of 1 year - 15 mm Hg. Art.; 8 - 10 years - as in an adult - 25 - 30 mm Hg. Art.

7. How does the speed of pulse wave propagation change with age? What are these indicators for children and adults? Increases due to a decrease in the elasticity of blood vessels. In children - 5-6 m / s, in adults - 8 - 9 m / s.

8. What is the intensity of blood flow through the tissues of a child and an adult (ml / min / kg of body weight)?

In a child - 195 ml / min / kg, in adults 70 ml / min / kg. The main reason for intensive blood flow through the tissues of a child is a higher level of metabolic processes in tissues in children compared to adults.

9. What is the circulation of blood? What is its value at rest and during intensive muscular work? What is the rate of blood circulation in children 1–3 years old and in adults?

The time during which the blood once passes through the large and small circles of blood circulation. At rest - 21-23 s, with muscular work - up to 9 s. In children under 3 years old - 15 s, in adults -22 s.

10. What changes in blood pressure occur during puberty?

An increase in blood pressure (“juvenile hypertension”) is caused by a discrepancy between the growth rate of the heart and an increase in the diameter of the main vessels, and also due to an increase in hormonal levels.

11. Why is blood pressure at the age of 11-14 years higher in girls than in boys?

This is the result of earlier puberty in girls and a high concentration of sex hormones, adrenaline, in the blood.

12. What adverse factors contribute to high blood pressure in children and adolescents?

Excessive study load, physical inactivity, violation of the daily routine, negative emotions.

13. What are the blood pressure indicators in children aged 1 year, 4 years, 7 years, 12 years?

Blood pressure indicators in children have their own characteristics. It is much lower than in adults. This is due to the greater elasticity of the vessel walls (diastolic pressure) and the lower force of myocardial contraction (systolic pressure). So, by the end of the first year of life, systolic blood pressure is 90–100 mm Hg. Art. , and diastolic - 42-43 mm Hg. Art. In children 4 years old, systolic pressure is 90–100 mm Hg. By the age of 7, it is equal to 95–105 mm Hg. Art., and by the age of 12 - 100-110 mm Hg. Art. Diastolic pressure by 4 years is 45-55, at 7 years - 50-60, and at 12 years - 55-65 mm Hg. Art. Systolic blood pressure becomes higher at puberty, much like that of an adult.

14. What are the gender differences in BP in adolescence?

Sex differences in the magnitude of blood pressure in children are not detected; they appear during adolescence (12–16 years). At the age of 12–13 years, girls have higher blood pressure than boys. This is the result of earlier puberty in girls compared to boys. At 14–16 years of age, on the contrary, systolic pressure in boys becomes higher than in girls. This pattern persists throughout later life. The value of systolic pressure depends on the physical development. Asthenic children have lower blood pressure than overweight children. The impact of unfavorable factors (physical inactivity, excessive study load) contributes to an increase in blood pressure in children at this age.

Age features of the regulation of vascular tone

1. When does the process of innervation of blood vessels in a child end? How is the violation of the innervation of blood vessels in children?

By the end of the 1st year of life. Violation of the innervation of blood vessels is manifested by the development of vegetative-vascular dystonia.

2. What is the reaction of the child's cardiovascular system during hypoxia (a significant decrease in the concentration of O 2 in the blood) if the child is in a stuffy or smoky room?.

The heart rate increases, blood pressure rises, as a result of which blood flow through all tissues increases, which compensates for the lack of oxygen in the blood.

3. How does the sympathetic nervous system affect vascular tone in children? How does this influence change with age?

Participates in maintaining vascular tone. With age, its influence intensifies.

4. What can be said about the maturity of the central mechanisms of regulation of vascular tone in a child? At what age is this process established? What are violations of the regulatory reactions of the cardiovascular system in adolescence?

The central mechanisms of regulation of the child's vascular tone are immature. The regulation of vascular tone is established by the end of the first year of life as the vasomotor center of the medulla oblongata matures. During adolescence, juvenile hypertension or hypotension may develop.

5. What is the variability of heart rate in children and adolescents and how does this indicator change during physical activity at a physical education lesson?

The values ​​of heart rate and blood pressure in children and adolescents are variable due to increased reactivity. Thus, in a first-grader, the heart rate at rest averages 88 beats/min. At 10 years old - 79 beats / min, at 14 years old - 72 beats / min. In this case, the individual spread of normal values ​​can reach 10 beats / min or more. With physical activity, depending on its intensity, the heart rate increases, and in children and adolescents it can reach 200 beats / min. In schoolchildren, after 20 squats, an increase in heart rate by 30–50% is observed. Normally, after 2–3 minutes, the heart rate is restored.

6. What are the values ​​of blood pressure in schoolchildren and how do they change during physical activity at a physical education lesson? What is the instability of blood pressure in children associated with?

Blood pressure (BP) in children aged 7–10 years 90/50–100/55 mm Hg; 10–12 years old - 95/60–110/60; 13-14 year olds - 105/60-115/60; in 15-16-year-olds - 105/60-120/70 mm Hg. and an increase in systolic blood pressure by 10–20 mm Hg, but a decrease in diastolic blood pressure by 4–10 mm Hg. Normally, after 2–3 minutes, blood pressure is restored. Sharp shifts in blood pressure indicators indicate the pathology of the cardiovascular system. The instability of blood pressure in children is associated with the immaturity of the central regulatory mechanisms, which determines the variability of the reactions of the cardiovascular system in various conditions.

7 . Briefly describe the changes in the regulation of vascular tone in the period from newborn to puberty?

They are becoming more and more resilient. Motor activity, physical education and sports accelerate the development of vascular tone regulation mechanisms.

8. Name the factors contributing to the development of primary arterial hypertension.

Hereditary predisposition, psycho-emotional overstrain, overweight, diabetes mellitus, excessive consumption of salty foods, physical inactivity.

9. What are the basics for the prevention of cardiovascular diseases in school age?

The development of cardiovascular diseases is associated with three main factors: irrational nutrition, physical inactivity and psycho-emotional stress.

When using a large amount of butter, eggs, atherosclerotic changes in blood vessels occur. There is also a relationship between the development of atherosclerosis and the consumption of large amounts of sugar. It has also been proven that overnutrition plays an important role in the development of cardiovascular pathology, when the amount of calories consumed exceeds their utilization during life. A negative effect on the cardiovascular system is exerted by hypodynamia - reduced physical activity.

Of great importance for the normal functioning of the cardiovascular system is the overstrain of the nervous system (psycho-emotional factor). The normal functioning of the cardiovascular system depends on the state of the nervous system. Diseases of the heart and blood vessels are more common in people whose work requires a lot of stress on the nervous system. Contribute to the development of diseases of the heart and blood vessels, alcohol consumption and smoking. However, among the many causes of cardiovascular diseases, non-compliance with food hygiene (irrational nutrition), violation of occupational and rest hygiene is of decisive importance. Therefore, the role of hygienic education in the family and at school is great. From childhood, it is necessary to cultivate healthy hygiene skills and prevent the formation of addictions (nicotine, alcohol, etc.). It is important to educate children and adolescents in ethical behavior, since psycho-emotional breakdowns are an important factor in the development of heart and vascular diseases.

10 . What is the school's role in preventing cardiovascular disease in students?

Teachers should teach children the rational organization of work and rest. For the child's body, the correct organization of rest is as important as the correct organization of training. However, at school and at home, insufficient work is being done to organize a physiologically healthy rest for the child, based on knowledge of the hygiene of the child's body. Schoolchildren need active rest, physical activity. However, during breaks, children are limited in their movements and hypodynamia occurs. It is necessary at school to pay attention to carrying out changes in the fresh air under the supervision of teachers and Sunday rest for children, to conduct appropriate instruction on life safety during vacations.

Age features of hormonal regulation of body functions

1. What is the special significance of hormones for children and adolescents?

Hormones provide physical, sexual and mental development of children and adolescents.

2. List the hormones that play a major role in the physical, mental, and sexual development of children and adolescents.

Growth hormone, thyroid hormones, sex hormones, insulin.

3. What is the peculiarity of the consequences of damage to the endocrine glands in children compared with adults?

Children have more severe, often irreversible disorders of physical, mental and sexual development.

4. What effect do pineal gland hormones have on the child's body? What changes occur in children with hypofunction or hyperfunction of the pineal gland?

They are involved in the regulation of puberty. Hypofunction leads to early puberty, hyperfunction - to obesity and the phenomenon of underdevelopment of the gonads.

5. Until what age does the thymus gland function intensively? What happens to her afterwards? How do dysfunctions of the thymus gland manifest in children?

Up to 7 years, then atrophy begins. In a decrease in immunity and, of course, in a greater susceptibility to infectious diseases.

6. At what period of child development do the adrenal glands begin to function more intensively? How does adrenal hypofunction manifest itself in children?

During puberty. Violation of protein and carbohydrate metabolism, decreased immunity.

7. How does adrenal hyperfunction manifest in children?

Obesity, in boys - premature puberty.

8. What disorders are observed in children with hyperfunction of the thyroid gland?

Increased growth, excessive weight gain and accelerated maturation of the body.

9. What disorders are observed in children with congenital hypothyroidism? What is the specificity of mental activity of children suffering from hypothyroidism?

Congenital hypofunction leads to a delay in the growth and development of the body, especially the nervous and reproductive systems, and underdevelopment of the intellect. With hypothyroidism, there are: apathy, lethargy, slowness. It takes more time to master the learning material.

10.What are the features of the influence of thyroid hormones on adolescents?

In adolescents, the level of energy metabolism is 30% higher than in adults; an increase in general excitability and increased heart rate are characteristic. Under the influence of TSH of the pituitary gland, the activity of the thyroid gland is stimulated. Her thyroid hormones (thyroxine, triiodothyronine), as well as adenohypophysis somatotropin, affect the growth of the body, the intelligence of the student. With a sharp decrease in the secretion of thyroid hormones, cretinism develops - a hereditary endocrine disease in which mental and physical underdevelopment occurs.

11. What disorders are observed in children with hypofunction and hyperfunction of the parathyroid glands?

With hypofunction of the parathyroid glands - an increase in the excitability of the central nervous system and muscles, which leads to tetany (convulsions), impaired bone development, hair and nail growth. With hyperfunction of the parathyroid glands, an increase in the level of calcium in the blood is noted, which causes excessive ossification.

12. What are the manifestations of violations of the internal secretion of the pancreas in children?

In a sharp violation of carbohydrate metabolism: the development of diabetes mellitus, malnutrition, impaired growth and mental development.

13. How does hypo- and hyperfunction of the adenohypophysis manifest itself in children?

With hypofunction: a decrease in basal metabolism and body temperature, growth retardation or dwarfism. With hyperfunction - gigantism.

14. What are the features of the functioning of the sex glands in boys and girls up to and from the age of 7?

In boys under 7 years of age, androgen production decreases and rises again from 7 years of age. In girls under 7 years of age, the production of estrogen is extremely small or absent, from the age of 7 it increases.

15.What is the role of the hypothalamus in ensuring the vital activity of the adolescent organism?

The hypothalamus is a subcortical center for the regulation of autonomic activity and the work of internal organs, metabolism. At the same time, it is very sensitive to the action of damaging factors (trauma, mental stress, etc.), which in the body of an older student leads to a change in its functional activity and various serious consequences. For example, dysfunction of the hypothalamus can lead to an increase in body temperature, hormonal imbalance, dysfunction of the reproductive system and the thyroid gland.

16.How is the effect of sex hormones on the central nervous system of a teenager?

Sex hormones affect the activity of the nervous system and the mental processes of a teenager. Androgens, released in greater quantities in boys, cause increased aggressiveness; estrogens, secreted in greater quantities in the girl's body, - on the contrary, responsiveness, compliance, discipline.

17.What are the manifestations of hormonal imbalance in adolescence?

At the beginning of puberty, there are changes in the work of the GI: the functional activity of the hypothalamus and pituitary gland, which actively produce hormones, increases, and the activity of the gonads has not yet reached the required level. Hence - the instability of the endocrine system, hormonal imbalance, leading to an unbalanced state of the central nervous system and often inadequate behavior.

18. What changes in the activity of the ANS and the behavior of adolescents occur under the influence of excessive secretion of adrenaline?

The activity of the sympathetic department increases and, accordingly, the concentration of the adrenal hormone adrenaline in the blood, resulting in a state of anxiety, tension, behavior becomes unstable and even sometimes aggressive.

19. What are the hormonal mechanisms of regulation of the reproductive system in girls? How to avoid failures in the regulation of the reproductive system?

The work of the hypothalamic-pituitary-ovarian system at a young age is regulated by pituitary hormones: FSH, LH, PL - prolactin. With insufficient production of FSH, the maturation of follicles in the ovary is disrupted or stops and infertility occurs. LH takes part in ovulation and the formation of the corpus luteum, which produces progestins (progesterone). With insufficient concentration of LH, the function of the corpus luteum is impaired, which can lead to a deficiency of progesterone and abortion. With increased production of PL, the formation of follicles stops and infertility occurs. In addition, the work of the reproductive system is regulated by the thyroid gland. A decrease in its function can lead to miscarriage. In order to prevent such failures in the body, it is necessary to: observe a rational regime of work and rest, nutrition, complete rejection of bad habits, regular physical education, creation of a favorable microclimate in the family and team, elimination of stressful situations, satisfaction with work or study, control of hormonal status and other parameters of reproductive, physical and mental health.

1. What type of breathing does a baby have and why?

Diaphragmatic type due to the horizontal position of the ribs.

2. What are the characteristics of the children's trachea and bronchi?

The trachea in children has a narrow lumen, short, elastic, its cartilages are easily displaced and squeezed. Children often have inflammation of the mucous membrane - tracheitis. Its main symptom is a severe cough. The bronchi in children are narrow, soft, elastic, their cartilage is easily displaced. The mucous membrane of the bronchi is rich in blood vessels, but relatively dry, since the secretory apparatus of the bronchi is underdeveloped in children, and the secret of the bronchial glands is viscous. This promotes inflammation of the bronchi. With age, the length of the bronchi increases, their gaps become wider, their secretory apparatus improves, and the secret produced by the bronchial glands becomes less viscous. Perhaps due to such age-related changes, bronchopulmonary diseases in older children are less common.

3. Describe the features of the lungs in childhood. In young children, frequent and shallow breathing, since only 1/3 of all alveoli are used during breathing. In addition, the relatively large liver of the child makes it difficult for the diaphragm to move downward, and the horizontal position of the ribs makes it difficult to raise them. The alveoli are small and contain little air. The lung capacity of a newborn is 67 ml. By the age of 8, the total number of alveoli corresponds to the number of adult alveoli (about 500–600 million). By the age of 10, lung volume increases 10 times, by 14 - 15 times. The lungs complete their development by the age of 18–20.

4. What is the respiratory rate in children?

A newborn breathes at a rate of 40 breaths per minute, that is, four times more often than an adult (12-16 breaths per minute). In a newborn, breathing is irregular: it accelerates, then slows down, then suddenly stops for a short time. The duration of pauses between exhalation and inhalation can be 6–7 s. With age, the frequency of respiratory movements per minute decreases and breathing becomes uniform. The smaller the child, the more often he breathes and the more uneven and shallow his breathing. If interruptions during breathing exceed 10–12 s, then the child should be examined. Age-related changes in the respiratory rate are observed: at 4 years, the respiratory rate is 22–28 cycles / min; at 7 years old - 22-23; 10 years - 16-20; in a teenager 16-18 cycles / min.

5. What is the respiratory volume in a newborn child, at the age of 1 year, 5 years and in an adult? What factors ensure faster diffusion of gases in the lung in children?

30, 60 and 240 ml respectively. In an adult - 500 ml. Factors of faster diffusion of gases in the lung in children: a relatively large surface of the lungs than in adults, a higher rate of blood flow in the lung, a wider network of capillaries in the lungs.

6. What is the value of lung capacity (VC) in children 5, 10 and 15 years of age? How can the volume of the chest and VC of a schoolchild be increased?

VC: 800 ml - 1500 - 2500 ml, respectively. Physical exercise increases the range of motion in the joints between the ribs and vertebrae, which helps to increase the volume of the chest and the vital capacity of the lungs.

7. What is the minute volume of air in children aged 1 year, 5 years, 10 years and in an adult?

In children: 2.7 liters, 3.3 liters, 5 liters. An adult has 6 - 9 liters.

8. How does the percentage of carbon dioxide and oxygen in the mixture of gases in the alveoli change with age? What are these indicators for a child and an adult?

9. What are the features of the transformation of the respiratory system in a teenager?

In a teenager, the chest and respiratory muscles develop intensively, the lungs grow in parallel and their volume increases, the VC and the depth of breathing increase. In this regard, the frequency of respiratory movements is reduced by 2 times compared to a small child. The dominant type of breathing is finally formed: in boys - abdominal, in girls - chest. All of the above transformations of the respiratory system of a growing organism are aimed at maximizing the satisfaction of its need for oxygen. Sometimes there is irregularity in breathing during a period of significant stretching of the body.

10. Describe the mechanisms of respiratory regulation in adolescence? At what age does voluntary regulation of breathing appear, what is it connected with?

In adolescents, the mechanisms of regulation of respiration do not yet work effectively. Under stress, there are signs of tension in the respiratory system, hypoxia may occur, which a teenager endures more difficult than an adult. Hypoxia can cause dizziness and fainting. Therefore, adolescents need aerobic exercises for at least 35 minutes a day, breathing exercises. With the onset of speech, by the age of 2–3, voluntary regulation of breathing appears; it is well developed at 4–6 years.

11. Do preschool children or teenagers tolerate oxygen starvation more easily? Why?

Children aged 1–6 years tolerate hypoxia more easily, because they have a lower excitability of the respiratory center, and it is less sensitive to afferent impulses from vascular chemoreceptors. With age, the sensitivity of the respiratory center to a lack of oxygen increases, so adolescents are more difficult to tolerate hypoxia.

12. What explains the small depth of breathing of a preschool child?

The relatively large liver of the child makes it difficult for the diaphragm to move downward, and the horizontal position of the ribs makes it difficult to raise them. In children under 7 years of age, the chest is cone-shaped, which limits the range of motion of the ribs. The intercostal muscles during this period are poorly developed. In this regard, the indicators of vital capacity of the lungs are low. At 4 years old, VC is 900 ml; at 7 years 1700 ml; at 11 years old -2700 ml. At the same time, the MOD (minute volume of breathing) also increases. From the age of 8–10, sex differences in breathing appear: in girls, the thoracic type of breathing prevails, and in boys, the abdominal type of breathing.

13. What are the basics for the prevention of diseases of the respiratory system in children?

The teacher needs to know the hygienic basics for the prevention of respiratory diseases in childhood: -regular ventilation of the premises at home and in a preschool educational institution; -frequent walks in the fresh air, physical activity during walks, due to which the muscular system and respiratory organs function intensively and blood oxygen delivery is enhanced to organs and tissues, - the inadmissibility of contact between a child and a sick person, since infection can be transmitted by airborne droplets.

14. What are the basics for the prevention of ENT diseases in a child?

Tonsils (palatine, lingual, nasopharyngeal, tubal) develop by the age of 6, play a protective role in the body, protect it from bacteria, viruses, since they consist of lymphoid tissue. In younger children, the tonsils are underdeveloped, the nasopharynx is not protected, so they often have colds. The Eustachian tubes connect the middle ear to the nasopharynx, as a result of which a nasopharyngeal infection can cause otitis media - inflammation of the middle ear, the prevention of which in children is the treatment of infections of the nose and pharynx. Inflammation of the tonsils (tonsillitis), adenoids and the absence of normal nasal breathing can lead to asthenization of the nervous system, rapid fatigue, headaches. In this case, the child needs supportive classes, the help of an otolaryngologist and a pediatric neurologist.

Age features of the urinary and reproductive systems

1. When do fetal kidneys begin to function? What is the proportion of their participation in the implementation of the excretory function in the fetus? Why?

The kidneys begin to function by the end of 3 months of intrauterine development. Their excretory function in the fetus is insignificant, since it is performed mainly by the placenta.

2. What is the difference between glomerular filtration of the kidney in young children from that of an adult? Explain the reasons.

Glomerular filtration is significantly reduced due to low glomerular capillary permeability, low vascular pressure (renal artery), small glomerular filtering surface, reduced blood flow through the kidneys. It corresponds to the level of adults in the second year of life. Reabsorption approaches the level of adults much earlier, by 5–6 months.

3. What is the peculiarity of urine concentration by the kidney of children of the 1st year of life? Explain the reasons.

Insufficient concentration of urine due to short loops of Henle and collecting ducts, insufficient production of ADH, which stimulates reabsorption.

4. What are the daily volumes of urine in children of different ages? As a result, children of all ages have a higher diuresis (per unit body weight), compared to adults by 2-4 times?

Newborn - up to 60 ml; 6 months - 300-500 ml; 1 year - 750-800 ml; 3-5 years - 1000 ml; 7–8 -1200ml; 10-12 years - 1500 ml.

Children have a higher diuresis due to the fact that per unit mass, more water enters the child's body with food than in the body of an adult. In addition, children have a more intense metabolism, which leads to the formation of more water in the body.

5. What is the frequency of urination in children of different ages? What explains the different frequency of urination in children depending on age? A child or an adult has more water loss through the skin (sweat and evaporation), why?

At 1 year - up to 15 times a day, due to the small volume of the bladder, more water consumption and more water formation per unit of body weight; at 3-5 years old - up to 10 times, at 7-8 years old - 7-6 times; at 10-12 years old - 5-6 times a day. The child sweats more, due to the greater surface area of ​​the skin per unit of body weight.

6. How does the formation of urination occur during the development of the child?

Urination is a reflex process. When the bladder is full, afferent impulses arise, reaching the center of urination in the sacral region of the spinal cord. . From here, efferent impulses enter the musculature of the bladder, causing it to contract, while the sphincter relaxes and urine enters the urethra. Involuntary urination occurs in children under 2 years of age. Therefore, in this age period, it is necessary to apply pedagogical and hygienic approaches to the child. Children older than 2 years of age may voluntarily delay urination, which is associated with the maturation of their cortical center for the regulation of urination. Therefore, they must comply with hygiene requirements on their own.

7. What functions do the organs of the reproductive system perform?

Reproductive function (provide the possibility of sexual intercourse, fertilization, the development of the embryo and fetus, as well as childbearing); determine the signs of sex, development and puberty. The genitals continue to develop up to 17 years. This causes the inadmissibility of early sexual intercourse.

8. What are the indicators of the maturity of the reproductive system in boys and girls.

For boys, an indicator of the maturity of the reproductive sphere and the development of the body is the appearance wet dreams(nocturnal involuntary eruptions of seminal fluid). They appear in adolescence, on average by the age of 15. For girls, an indicator of the maturity of the reproductive sphere and the development of the body is menarche. At 12–14 years of age, adolescent girls develop menarche, which indicates the formation of the hypothalamic-pituitary-ovarian system that regulates sexual cycles. About a year before the onset of menarche, the most rapid growth of the body (third stretch) is noted. With the onset of menstruation, body growth in length slows down, but there is an increase in body weight (rounding) and a rapid development of secondary sexual characteristics.

9.Describe the stages of puberty

Prepubertal, or stage of infantilism (9-10 years)- the period before the onset of puberty, characterized by the absence of secondary sexual characteristics and cyclic processes. Beginning of puberty, or pituitary stage (11-12 years old)- activation of the pituitary gland, increased secretion of gonadotropins (GTH) and somatotropin (STH), growth of the external and internal genital organs and swelling of the mammary glands under the influence of HTH The stage corresponds to a growth spurt in girls. Sex hormones are secreted in a very small amount, as a result of which there is a slight pilosis of the pubis and armpits. Followed by puberty (13–16 years), including two periods: activation of the gonads and steroidogenesis. During the period activation of the gonads (13-14 years old) pituitary hormones (FSH) activate the sex glands, therefore their function is enhanced, cyclic processes and pronounced secondary sexual characteristics appear. steroidogenesis (15–16 years) steroid sex hormones are intensively secreted, secondary sexual characteristics are intensively developed: active hair growth according to male and female types; male and female body types are formed, respectively; in boys, the breaking of the voice is completed; Girls have regular periods. Stage of completion of puberty (17–18 years)- the level of sex hormones characteristic of an adult is established, due to stimulation of the sex glands from the pituitary gland. Secondary sexual characteristics are fully expressed.

10. What is puberty in humans?

Puberty is the stage of ontogeny when a person reaches the ability to give birth to a child. Puberty in humans has physiological and social aspects. Physiological - the ability to conceive, bear a fetus and give birth to a child, which is possible after ovulation and can occur even in adolescence. Social - the ability to raise children for a long period: (childhood, general and higher education, vocational training), etc.

11.What are the measures to prevent diseases of the urinary and reproductive systems in schoolchildren?

It is very important for a student to observe the hygiene of the external genital organs, which must be washed with warm water and soap in the morning and evening. Failure to follow the rules of personal hygiene leads to inflammation of the urinary tract and urethra, the mucous membrane of which in children is very vulnerable. In addition, hypothermia can cause inflammation of the bladder. The urethra in girls is short, so they often develop inflammatory diseases of the urinary organs (cystitis, pyelonephritis, etc.). In this regard, the girl's genitals should be kept clean and not subjected to hypothermia.

Prevention of inflammatory diseases of the kidneys is, first of all, the prevention of infectious diseases of the genital organs. There are also rules for the behavior of adolescent girls on critical days. They cannot go on long hikes, actively engage in physical education and sports, sunbathe, swim, take a bath or go to the bath (instead of them - a warm shower), take spicy food. At the same time, there is no need to arrange bed rest, to lead a motionless lifestyle. You need to do your daily work, reducing physical activity.

In boys, by the time of birth, the testicles are lowered into the scrotum, and the penis is closed by the foreskin. By the year, the foreskin becomes more elastic, the opening of the head is easy, and therefore hygiene is required (see phimosis).

12. How should a teenager with enuresis behave?

From 5 to 10% of adolescents 12-14 years old suffer from enuresis. These are children who are in a neurotic state. They need dietary nutrition, without irritating, salty and spicy foods, limiting fluid intake, especially before bedtime, exclusion of physical activity and sports games in the afternoon. In the autumn-winter period, due to the cooling of the body, cases of enuresis become more frequent. With age, enuresis, associated mainly with functional abnormalities in the nervous system of children, disappears. Mental trauma, overwork (especially from physical exertion), hypothermia, sleep disturbance, irritating and spicy foods, as well as an abundance of liquid taken before bed contribute to enuresis.

Age features of the digestive system and digestion

1. What nerve centers coordinate the act of sucking a baby? In what parts of the brain are they located? What centers do they interact with?

Centers located in the medulla oblongata and midbrain in interaction with the centers of swallowing and breathing.

2. How does the pH value of gastric juice change with age? (compare with the norm of an adult). What is the volume of the stomach in a child after birth and by the end of the 1st year of life?

The acidity of gastric juice in children is low, it reaches the level of acidity of an adult only by the age of 10. In newborns, it is about 6 u. units, in young children - 3 - 4 c.u. units (in an adult - 1.5). The volume of the stomach is 30 ml and 300 ml, respectively.

3. What are the age characteristics of the digestive organs in children and adolescents?

Morphologically and functionally, the child's digestive organs are underdeveloped. Differences between the digestive organs of an adult and a child can be traced up to 6-9 years. The shape, size, of these organs, the functional activity of enzymes are changing. The volume of the stomach from birth to 1 year increases 10 times. In preschool children, there is a weak development of the muscular layer of the gastrointestinal tract and underdevelopment of the glands of the stomach and intestines.

4. What are the characteristics of digestion in children?

The number of enzymes and their activity in the gastrointestinal tract in children is significantly lower than in adults. But in the first year of life, the activity of the enzyme chymosin is high, under the influence of which the hydrolysis of milk protein occurs. In adults, it is not found in the stomach. The activity of proteases and lipases of gastric juice is low. The activity of the pepsin enzyme that breaks down proteins increases abruptly: by 3 years, by 6 years, and in adolescence - at 12–14 years. With age, the activity of lipases gradually increases and reaches a maximum only by 9 years. Therefore, fat-containing foods, meat, fish, children under 9 years of age should be given boiled, or stewed with a little vegetable oil. It is necessary to exclude canned food, fatty, smoked, spicy, fried and salty foods. In young children, the low intensity of cavitary digestion in the small intestine, which is compensated by the greater intensity of membrane and intracellular digestion. The low concentration of hydrochloric acid causes weak bactericidal properties of gastric juice in children, and therefore, they often have digestive disorders.

5. What is the physiological significance of the intestinal microflora in a child?

1) It is a protection factor against pathogenic intestinal microorganisms; 2) has the ability to synthesize vitamins (B 2 , B 6 , B 12 , K, pantothenic and folic acids); 3) participates in the breakdown of plant fiber.

6. Why is it important to include fruits and vegetables in children's diets?

Vegetable and fruit juices are introduced from 3–4 months of age. Fruits and vegetables are the most important sources of vitamins A, C and P, organic acids, mineral salts (including calcium ions important for bone growth), various trace elements, pectin, and vegetable fiber (cabbage, beets, carrots, etc.), which activates bowel function.

7. When does teething start? When do permanent teeth erupt? When does this process end?

From 6 months, the eruption of milk teeth begins. At the age of 2–2.5 years, the child already has all 20 milk teeth and can eat more solid food. In subsequent periods of life, milk teeth are gradually replaced by permanent ones. The first permanent teeth begin to appear from 5 to 6 years; This process ends with the appearance of wisdom teeth at the age of 18-25.

8. Give a brief description of the functional state of the liver at the time of the birth of the child. At what age does liver development complete?

The liver of a child is relatively large, accounting for 4% of body weight. In an adult -2.5%. The liver is functionally immature, detoxification and exocrine functions are imperfect. Its development is completed by 8–9 years of age.

9. Give a brief description of the functional state of the pancreas at the time of the birth of the child. What changes does it undergo with age?

Morphologically fully formed. However, the exocrine function remains immature. Despite this, iron ensures the breakdown of substances contained in milk. With age, its secretory function changes: the activity of enzymes - proteases (trypsin, chymotrypsin), lipases increases and reaches a maximum by 6–9 years.

10.List the most common disorders of the digestive system in children and adolescents. What contributes to the violation and preservation of the functions of the gastrointestinal tract?

Gastritis - inflammation of the gastric mucosa, often due to damage to its mucosa by bacteria Helicobacter pylori and peptic ulcer (in children and adolescents more often than the duodenum). Factors of disorders of the digestive system are: poor nutrition, poor-quality food, violation of the diet, exposure to nicotine, alcohol, harmful substances, prolonged psycho-emotional stress. In the educational process of the school, mental hygiene standards must be observed, because the activity of the digestive organs is controlled by the nervous system and depends on its functional states . Teachers need to accustom children to a strict diet, because at lunchtime, when an intensive secretion of gastric juice begins, students should receive hot meals. Therefore, the educational process is built in such a way as not to interfere with the production of gastric juice for a certain time for eating.

11. How is hunger and appetite manifested in children? What can be eating disorders in children and adolescents?

Hunger is the feeling of the need to eat, which organizes human behavior accordingly. In children, it manifests itself in the form of weakness, dizziness, discomfort in the epigastric region, etc. The regulation of hunger is carried out due to the activity of the food center, which consists of the center of hunger and satiety, located in the lateral and central nuclei of the hypothalamus. Appetite is a feeling of need for food as a result of the activation of the limbic structures of the brain and the cerebral cortex. Appetite disorders in adolescence and adolescence may manifest more often as a decrease in appetite (anorexia) or less often as an increase in it (bulimia). With anorexia nervosa, food intake is sharply limited, which can lead to metabolic disorders, anemia, thyroid diseases (hypothyroidism), myocardial dystrophy, pathological changes in appetite, up to the rejection of meat, fish, etc.

12. What are the basics for the prevention of diseases of the digestive system in children?

The organization of rational nutrition of children is one of the prerequisites for education at school and the prevention of diseases of the digestive system. Children stay in schools from 6 to 8 hours, and in the extended day group even longer. During this period, they consume a lot of energy. Therefore, schools need to organize meals that are appropriate for the age and needs of children. They should be provided with hot breakfasts, and children in extended day groups - not only breakfasts, but also lunches. It is necessary to perform a rational diet. Monotonous food, dry food, hastily and overeating are not allowed. It is necessary to teach the child to chew food diligently, to observe oral hygiene. For children suffering from chronic diseases of the gastrointestinal tract, overweight, meat steam cutlets, steamed fish, steam casseroles, soups with vegetable broths, boiled potatoes, vegetables and fruits are recommended. Children's food should contain all nutrients, mineral salts, water, vitamins. The ratio of these components should correspond to age, body weight, and in adolescents also gender. Children should not be addicted to sweets. Food should be taken 4 times a day. An exemplary schoolchildren's menu is presented in Table 13, Appendix 1. To prevent intestinal infections at school, it is important to observe the hygiene of bathrooms and carry out wet cleaning of the premises daily. Schoolchildren and preschoolers should wash their hands with soap, cut their nails short, do not drink raw water, and do not eat unwashed vegetables and fruits. This should be monitored by the teacher. The school health worker draws up a list of students who need diet food, brings this information to teachers, parents and school canteen workers. Teachers should systematically monitor the nutrition of children suffering from chronic gastrointestinal diseases.

Age-related features of metabolism

1. Name the features of metabolism in the child's body

In a child's body, the metabolism is more intense than in adults, and synthetic processes (anabolism) dominate. The predominance of synthesis (anabolism) over decay (catabolism) ensures growth and development. Children and adolescents have an increased need for nutrients per unit of body weight compared to adults, which is due to the following reasons: - children have a high energy expenditure (high energy consumption); - they have a greater ratio of body surface to its mass than adults; -children are more mobile than adults, which requires energy expenditure. In an adult organism, anabolism and catabolism are in dynamic balance.

2. What is the ratio of basal metabolism in children 3-4 years of age, during puberty, aged 18-20 years and adults (kcal / kg / day)?

In children 3-4 years old, the value of the basal metabolism is approximately 2 times greater, during puberty - 1.5 times greater than in adults. At 18 - 20 years old - corresponds to the norm for adults (24 kcal / kg / day).

3. What explains the high intensity of oxidative processes in a growing organism?

A higher level of metabolism in tissues, a relatively large body surface (relative to its mass) and a large expenditure of energy to maintain a constant body temperature, increased secretion of thyroid hormones and norepinephrine.

4. How do energy costs for growth change depending on the age of the child: up to 3 years, before the onset of puberty, during puberty?

They increase in the first years after birth, then gradually decrease, and during puberty increase again, which affects the decrease in basal metabolism during this period.

5. What is the percentage of energy spent in the body in children for basal metabolism, movement and maintaining muscle tone, the specific dynamic effect of food compared to adults?

In a child: 70% is for the main metabolism, 20% for movement and maintaining muscle tone, 10% for the specific dynamic effect of food. In an adult: 50 - 40 - 10%, respectively.

6. What are the age characteristics of fat metabolism?

During the period of intensive growth, the formation of new cells and tissues, the body needs more fat. With fats, fat-soluble vital vitamins (A, D, E) enter the body. When using fats, there should be a sufficient amount of vegetable fiber (complex carbohydrate), since with its deficiency, incomplete oxidation of fats occurs and metabolic products (ketone bodies) accumulate in the blood. The child's body needs fats for the morphological and functional maturation of the nervous system, for example, for the myelination of nerve fibers, the formation of cell membranes. The most valuable are the fat-like substances lecithins, which strengthen the nervous system, contained in butter, egg yolk, and fish. A deficiency in the body of fats leads to a metabolic failure, a decrease in the immune system and increased fatigue. Excess, as well as lack of fat in the body, slows down the immune response.

7. What should be the ratio of proteins, fats and carbohydrates in the diet of children aged one year and older and adults?

At the age of 1 year and older, the ratio of proteins, fats and carbohydrates -

1: 1, 2: 4, 6 - that is, as in adults.

8. Name the features of the exchange of mineral salts and water in children.

A feature of mineral metabolism in children is that the intake of mineral substances into the body exceeds their excretion. The need for sodium, calcium, phosphorus and iron is increased, which is associated with the growth of the body. Children have a higher water content in the body compared to adults, which is due to the greater intensity of metabolic reactions. In the first 5 years, the total water content is 70% of the child's body weight (in adults, about 60%). The daily water requirement for a newborn is 140–150 ml/kg of body weight; at the age of 1-2 years - 120-130 ml / kg; 5-6 years - 90-100 ml / kg; at 7-10 years old - 70-80 ml / kg (1350 ml); at 11-14 years old - 50-60 ml / kg (1500-1700 ml), in an adult - 2000-2500 ml.

9. What changes will occur in the body with a long absence of fats and carbohydrates in the diet of a schoolchild, but with an optimal intake of protein from food (80-100 g per day)?

The consumption of nitrogen will exceed its intake (negative nitrogen balance), weight loss will occur, since energy costs will be compensated mainly by proteins and fat depots.

10. What are the Nutrient Intakesin children, adolescents and adults?

With insufficient intake of nutrients into the child's body, the functions of many organs and body systems are disrupted. Therefore, the body of children and adolescents should receive proteins, fats, carbohydrates in the optimal ratio. From the age of 4, the body's daily need for protein nutrition increases - 49-71 g of protein per day, at 7 years old 74-87 g, at 11-13 years old - 74-102 g, at 14-17 years old -90 -115 g. For children and adolescents, a positive nitrogen balance is characteristic, when the amount of nitrogen supplied with protein foods exceeds the amount of nitrogen excreted from the body. This is due to growth and weight gain. With age, the absolute amount of fat necessary for the normal development of the child increases. From 1 to 3 years old, it requires 44–53 g per day, at 4–6 years old - 50–68 g, at 7 years old 70–82 g, at 11–13 years old - 80–96 g, at 14–17 years old - 93–107. Fat depots in children are quickly depleted with a lack of carbohydrate food. From 1 to 3 years old, a child needs 180-210 g of carbohydrates per day, at 4-6 years old - 220-266 g, at 7 years old - 280-320 g, at 11-13 years old - 324-370 g, by 14- 17 years - 336-420 g. Norms of nutrient intake in adults: proteins - 110 g, fats - 100 g, carbohydrates - 410 g. Ratio 1: 1: 4.

11. How does the state of the body change with excessive intake of fat?

Obesity, atherosclerosis develops, which are a risk factor for the development of cardiovascular diseases. Due to prolonged consumption of rich fatty foods, the work of the islets of Langerhans may be disrupted. Excess consumption of fatty foods combined with a sedentary lifestyle can also lead to the formation of gallstones.

12.What factors contribute to the violation of fat metabolism in children and adolescents?

Factors contributing to the violation of fat metabolism and overweight may be the following: excessive nutrition of the child at an early age; excessive consumption of carbohydrates, fats, family food traditions associated with overeating; sedentary lifestyle.

13. How to determine proper body weight in children and adolescents?

The most common method for determining body weight is the body mass index - the ratio of body weight (kg) to height (m 2). The BMI norm in children and adolescents is 14.0–17.0.

14.What is the importance of carbohydrates for a growing organism?

During the period of growth and development, carbohydrates perform an energy function, participate in the oxidation of protein and fat metabolism products, and thereby help maintain the acid-base balance in the body. The brain is sensitive to low glucose levels. The student feels weak, gets tired quickly. Taking 2-3 sweets improves working condition. Therefore, schoolchildren need to take a limited amount of sweets, but the blood sugar level should not exceed 0.1%. With a sharp emotional arousal, for example, during exams, glucose breaks down, which is why in this case it is recommended to use chocolate, ice cream, etc.

In children, the metabolism of carbohydrates occurs with greater intensity, which is explained by the high level of metabolism in the growing body.

15. How does a deficiency of vitamins and minerals affect the child's body?

The lack of vitamins and minerals in children is largely associated with poor nutrition. Fast food - sandwiches, foods with preservatives, lack of animal protein do not provide the body with the necessary amount of vitamins, calcium, magnesium, iron ions, etc. Strict diets for children can adversely affect growth and development. Symptoms of beriberi and mineral deficiency appear: dryness and peeling of the skin, lips, hair loss, blurred vision, allergic reactions on the skin of the face, loss of appetite, etc. Vitamin and mineral deficiency is detected more often in children who are malnourished at an early and preschool age, which negatively affects the physiological state of the body, performance at school and at home. The class teacher, social teacher, administration should help the child overcome such difficulties, since children from families with low social status can receive hot lunches and breakfasts at school for free.

16. What parameters are taken into account in the hygienic assessment of the schoolchild's diet?

1. Compensation for the body's energy costs. 2- Providing the body's needs for nutrients, vitamins, minerals, water. 3 - Compliance with the diet.

During the development of a child, significant morphological and functional changes occur in his cardiovascular system. The formation of the heart in the embryo begins from the second week of embryogenesis and a four-chambered heart is formed by the end of the third week. The blood circulation of the fetus has its own characteristics, primarily related to the fact that before birth, oxygen enters the body through the placenta and the so-called umbilical vein.

The umbilical vein branches into two vessels, one feeding the liver, the other connected to the inferior vena cava. As a result, oxygen-rich blood (from the umbilical vein) and blood flowing from the organs and tissues of the fetus mix in the inferior vena cava. Thus, mixed blood enters the right atrium. As after birth, the atrial systole of the fetal heart directs blood into the ventricles, from there it enters the aorta from the left ventricle, and from the right ventricle into the pulmonary artery. However, the atria of the fetus are not isolated, but are connected using an oval hole, so the left ventricle sends blood to the aorta partially from the right atrium. A very small amount of blood enters the lungs through the pulmonary artery, since the lungs in the fetus do not function. Most of the blood ejected from the right ventricle into the pulmonary trunk, through a temporarily functioning vessel - the ductus botulinum - enters the aorta.

The most important role in the blood supply to the fetus is played by the umbilical arteries, which branch off from the iliac arteries. Through the umbilical opening, they leave the body of the fetus and, branching, form a dense network of capillaries in the placenta, from which the umbilical vein originates. The fetal circulatory system is closed. The mother's blood never enters the fetal blood vessels and vice versa. The supply of oxygen to the blood of the fetus is carried out by diffusion, since its partial pressure in the maternal vessels of the placenta is always higher than in the blood of the fetus.

After birth, the umbilical arteries and vein become empty and become ligaments. With the first breath of a newborn, the pulmonary circulation begins to function. Therefore, usually the botallian duct and the foramen ovale quickly overgrow. 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 heart grows most intensively in the first years of life and at the end of adolescence. The position and shape of the heart also change with age. In a newborn, the heart is spherical in shape and is located much higher than in an adult. Differences in these indicators are eliminated only by the age of ten. By the age of 12, the main functional differences in the cardiovascular system also disappear.

The heart rate (Table 5) in children under 12 - 14 years of age is higher than in adults, which is associated with the predominance of the tone of sympathetic centers in children.

In the process of postnatal development, the tonic influence of the vagus nerve is constantly increasing, and in adolescence, the degree of its influence in most children approaches the level of adults. A delay in the maturation of the tonic influence of the vagus nerve on cardiac activity could indicate a retardation of the child's development.

Table 5

Resting heart rate and respiration rate in children of different ages.

Table 6

The value of blood pressure at rest in children of different ages.

Blood pressure in children is lower than in adults (Table 6), and the rate of circulation is higher. The stroke volume of blood in a newborn is only 2.5 cm3, in the first year after birth it increases four times, then the growth rate decreases. To the level of an adult (70 - 75 cm3), stroke volume approaches only 15 - 16 years. With age, the minute volume of blood also increases, which provides the heart with increasing opportunities for adaptation to physical exertion.

Bioelectrical processes in the heart also have age-related features, so the electrocardiogram approaches the form of an adult by the age of 13-16.

Sometimes in the pubertal period there are reversible disturbances in the activity of the cardiovascular system associated with the restructuring of the endocrine system. At the age of 13-16, there may be an increase in heart rate, shortness of breath, vasospasm, violations of the electrocardiogram, etc. In the presence of circulatory dysfunctions, it is necessary to strictly dose and prevent excessive physical and emotional stress in a teenager.

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Age features of the cardiovascular system in children

The circulatory system of children changes from birth to adulthood, along with the growth and development of the child himself, his musculoskeletal system and internal organs.

Cardiovascular system of the newborn

With the cardiosystem of a newly born baby, everything is different from that of an adult:

• the heart is located differently, much higher, due to the raised diaphragm;
• its shape resembles a ball, and the width is slightly greater than the length;
• the left and right ventricles have the same wall thickness;
• as a percentage of body weight, in an infant, the heart weighs twice as much as an adult's heart, about 0.9%;
• the average blood pressure is 75 mm Hg;
• a full circle of blood passes through the body of a newborn in 12 seconds.

The cardiovascular system of a newborn develops especially intensively in the first year of life, and the heart grows rapidly:

• at 8 months, a baby's heart weighs twice as much as at birth;
• by 12 months, the baby's blood pressure reaches a maximum of 100 mm Hg.

Age features of the cardiovascular system of preschoolers and schoolchildren

Big changes are taking place in the heart of a child of preschool and primary school age. Age-related features of the cardiovascular system during this period of a baby's life are associated with enhanced physical development, jumps in growth and weight.

There is a growth of the key organ of the cardiosystem, the heart:

• by the age of 3, its mass triples in comparison with birth weight;
• at 5 years old, it already weighs 4 times more;
• at 6 years old - at 11!

The number of heartbeats decreases:

• in a newborn, on average, 120 contractions per minute are recorded;
• in a child by the age of 4, their number decreases to 100;
• after 7 years, the child's heart usually beats at a frequency of 75 beats per minute.

In 5-year-old preschool children, blood pressure usually reaches a maximum value of 104 mmHg, and this value is maintained, as a rule, until 8 years of age. Although significant fluctuations are observed, which in most cases are not symptoms of pathology, but may be associated with emotional factors, physical activity, etc.

The cardiovascular system of adolescents

In teenagers, during puberty, the body and health are formed, with which they will have to live in adulthood. The cardiovascular system of adolescents is also rapidly changing. She, too, "ripens":

• the heart slows down its growth rate and reaches the size of an adult;
• moreover, in girls it grows somewhat differently during the period of protuberance than in boys, sometimes ahead, but by the age of 16, the heart still becomes heavier in the stronger sex;
• by the age of 16, the maximum value of blood pressure can reach 134 mm Hg, while large pressure surges are possible, which are usually not a consequence of heart disease, but only a manifestation of a reaction to stress;
• By the age of 14, blood makes a full circle through the body of a teenager in 18.5 seconds.

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Age features of the cardiovascular system

Fetal circulation. In the process of intrauterine development, a period of lacunar and then placental circulation is distinguished. At very early stages of embryo development, lacunae form between the chorionic villi, into which blood continuously flows from the arteries of the uterine wall. This blood does not mix with the blood of the fetus. From it, selective absorption of nutrients and oxygen occurs through the wall of the vessels of the fetus. Also, from the blood of the fetus, decay products formed as a result of metabolism and carbon dioxide enter the lacunae. Blood flows from the lacunae through the veins into the mother's circulatory system.

Metabolism, carried out through the lacunae, cannot satisfy the needs of a rapidly developing organism for a long time. The lacunar circulation is replaced by placental circulation, which is established in the second month of intrauterine development.

Venous blood from the fetus to the placenta flows through the umbilical arteries. In the placenta, it is enriched with nutrients and oxygen and becomes arterial. Arterial blood to the fetus comes through the umbilical vein, which, heading to the fetal liver, is divided into two branches. One of the branches flows into the inferior vena cava, and the other goes through the liver and in its tissues is divided into capillaries, in which gases are exchanged, after which the mixed blood enters the inferior vena cava and then into the right atrium, where venous blood also enters from the upper vena cava.

A smaller part of the blood from the right atrium goes into the right ventricle and from it into the pulmonary artery. In the fetus, the pulmonary circulation does not function due to the lack of pulmonary respiration, and therefore a small amount of blood enters it. The bulk of the blood flowing through the pulmonary artery encounters great resistance in the collapsed lungs; it enters the aorta through the ductus botalis, which flows into it below the place where the vessels drain to the head and upper limbs. Therefore, these organs receive less mixed blood, containing more oxygen than the blood going to the trunk and lower limbs. This provides better brain nutrition and more intensive development.

Most of the blood from the right atrium flows through the foramen ovale into the left atrium. A small amount of venous blood from the pulmonary veins also enters here.

From the left atrium, blood enters the left ventricle, from it into the aorta and goes through the vessels of the systemic circulation, from the arteries of which two umbilical arteries branch off, leading to the placenta.

Circulatory changes in the newborn. The act of giving birth to a child is characterized by its transition to completely different conditions of existence. Changes occurring in the cardiovascular system are associated primarily with the inclusion of pulmonary respiration. At the time of birth, the umbilical cord (umbilical cord) is bandaged and cut, which stops the exchange of gases in the placenta. At the same time, the content of carbon dioxide in the blood of the newborn increases and the amount of oxygen decreases. This blood, with a changed gas composition, comes to the respiratory center and excites it - the first breath occurs, during which the lungs expand and the vessels in them expand. Air enters the lungs for the first time.

Expanded, almost empty vessels of the lungs have a large capacity and low blood pressure. Therefore, all the blood from the right ventricle through the pulmonary artery rushes to the lungs. The botallian duct gradually overgrows. Due to the changed blood pressure, the oval window in the heart is closed by a fold of the endocardium, which gradually grows, and a continuous septum is created between the atria. From this moment on, the large and small circles of blood circulation are separated, only venous blood circulates in the right half of the heart, and only arterial blood circulates in the left half.

At the same time, the vessels of the umbilical cord cease to function, they overgrow and turn into ligaments. So at the time of birth, the fetal circulatory system acquires all the features of its structure in an adult.

In a newborn, the mass of the heart is on average 23.6 g (from 11.4 to 49.5 g) and is 0.89% of body weight. By the age of 5, the mass of the heart increases by 4 times, by 6 - by 11 times. In the period from 7 to 12 years, the growth of the heart slows down and somewhat lags behind the growth of the body. At the age of 14-15 years (puberty), the increased growth of the heart begins again. Boys have more heart mass than girls. But at the age of 11, girls begin a period of increased heart growth (in boys, it begins at 12 years old), and by the age of 13-14, its mass becomes larger than that of boys. By the age of 16, the heart of boys again becomes heavier than girls.

In a newborn, the heart is located very high due to the high position of the diaphragm. By the end of the first year of life, due to the lowering of the diaphragm and the transition of the child to a vertical position, the heart takes an oblique position.

Changes with age in heart rate. In a newborn, the heart rate is close to its value in the fetus and is 120 - 140 beats per minute. With age, the heart rate decreases, and in adolescents it approaches the value of adults. The decrease in the number of heartbeats with age is associated with an increase in the influence of the vagus nerve on the heart. Gender differences in heart rate were noted: in boys it is less than in girls of the same age.

A characteristic feature of the activity of the child's heart is the presence of respiratory arrhythmia: at the moment of inhalation, an increase in the heart rate occurs, and during exhalation, it slows down. In early childhood, arrhythmia is rare and mild. Starting from preschool age and up to 14 years, it is significant. At the age of 15-16 years, there are only isolated cases of respiratory arrhythmia.

Age features of systolic and minute volumes of the heart. The value of the systolic volume of the heart increases with age more significantly than the value of the minute volume. The change in minute volume is affected by the decrease in the number of heartbeats with age.

The value of systolic volume in newborns is 2.5 ml, in a child of 1 year old - 10.2 ml. The value of minute volume in newborns and children under 1 year old is on average 0.33 l, at the age of 1 year - 1.2 l, in 5-year-old children - 1.8 l, in 10-year-olds - 2.5 l. In children who are more physically developed, the value of systolic and minute volumes is greater.

Features of changes in blood pressure with age. In a newborn child, the average systolic pressure is 60 - 66 mm Hg. Art., diastolic - 36 - 40 mm Hg. Art. In children of all ages, there is a general tendency for systolic, diastolic, and pulse pressure to increase with age. On average, the maximum blood pressure by 1 year is 100 mm Hg. Art., by 5 - 8 years - 104 mm Hg. Art., by 11 - 13 years - 127 mm Hg. Art., by 15 - 16 years - 134 mm Hg. Art. The minimum pressure, respectively, is: 49, 68, 83 and 88 mm Hg. Art. Pulse pressure in newborns, it reaches 24 - 36 mm Hg. Art., in subsequent periods, including in adults, - 40 - 50 mm Hg. Art.

Classes at school affect the value of the blood pressure of students. At the beginning of the school day, there was a decrease in the maximum and an increase in the minimum pressure from lesson to lesson (i.e., the pulse pressure decreases). By the end of the school day, blood pressure rises.

During muscular work in children, the value of the maximum increases and the value of the minimum pressure slightly decreases. During the performance of the maximum muscle load in adolescents and young men, the value of the maximum blood pressure can increase up to 180–200 mm Hg. Art. Since at this time the value of the minimum pressure changes slightly, the pulse pressure increases to 50–80 mm Hg. Art. The intensity of changes in blood pressure during exercise depends on age: the older the child, the greater these changes.

Age-related changes in blood pressure during exercise are especially pronounced in the recovery period. The restoration of the systolic pressure to its original value is carried out the faster, the older the child's age.

During puberty, when the development of the heart is more intense than the vessels, so-called juvenile hypertension can be observed, i.e., an increase in systolic pressure to 130 - 140 mm Hg. Art.

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Features of the cardiovascular system in children and adolescents

heart shape

the shape of the heart of a newborn is completely different from that of an adult. When a baby is born, the main pump of his body looks like a ball. This is due to the fact that different parts of the organ are approximately the same size and the atria are comparable in volume to the ventricles. The ears - adnexal formations of the atria - also have a rather large size. Later, as the heart increases mainly in length, it changes its configuration. So, at the age of 6 in children, it already has a distinctly oval shape. Such outlines create a certain resemblance to the heart of an adult. In addition, the chambers of the organ increase in comparison with the large vessels extending from it, and the heart itself becomes more prominent due to the ventricles, which increase in size and power over the years.

Further changes occur mainly due to the continued growth of the ventricles, as a result of which the heart of a 14-year-old adolescent does not differ in shape from an adult.

Heart position

The heart of a newborn is located quite high. If in an adult its lower part - the apex - is projected between the fifth and sixth ribs, then in an infant it is one intercostal space higher. The base lies close enough to the neck, at the level of the first rib, and as it grows older it drops to the level of the third, where it should eventually be. The heart passes half of this way in the first 1.5 months of the Child's life. At birth, the organ is located not only higher, but also to the left: if, in order to find the top of the heart, in an adult, you need to deviate from the left mid-clavicular line 1-1.5 cm in right side, then the baby must measure the same distance to the left.

The change in the position of the heart in the chest, which occurs with age, is due to changes not so much in the heart itself as in the organs surrounding it. When growing up, all parts of the body are elongated, and the diaphragm acquires a lower position, so the tip goes down and the organ remains in an oblique position. The final version of the location of the heart is established only by the 22-23rd year of life; by this time, the organ has long ceased to grow and change its shape.

Structural features of the myocardium and anatomical features of the fetal heart

The body of an adult is 60% water. The proportion of fluid in the child's body is much larger - it reaches 80%. This is a very significant indicator: for comparison, the body of a jellyfish contains a little more than 90% of water. This feature provides the child's heart with greater elasticity and suppleness. In addition to the general structure of tissues, the organ differs from the adult state in a well-developed vascular network that supplies nutrition and oxygen to the heart muscle. If you examine a section of a child's myocardium under a microscope, differences in the structure of cardiomyocyte cells will also become noticeable. They are thinner, they have many nuclei, there are no powerful connective tissue partitions between them, which provides a more delicate tissue structure. Gradually, the myocardium undergoes changes, and in a 10-year-old child, the structure of the heart muscle already corresponds to the norms of an adult. During intrauterine existence, only one circle of blood circulation, the large one, functions fully. In this regard, the fetal heart has some anatomical features that provide proper blood flow. In the child's body at this time, the blood from the right chambers of the heart mixes with the blood from the left, i.e., arterial with venous. This phenomenon does not cause oxygen starvation, as in adults suffering from heart defects with blood loss. This happens because the fetus receives oxygen through the placental circulation, and not through the lungs.

The mixing of arterial and venous blood in the fetal body occurs in two ways - through the so-called oval window and the Botallian duct. The foramen ovale is a small opening in the interatrial septum, and the Botallian duct is a canal that connects the aorta, which receives blood from the left ventricle, and the pulmonary artery, which exits the right. By the time of birth, at most during the first weeks of life, these messages are closed. Arterial and venous blood flow become isolated from each other, which allows you to establish "adult" blood circulation. In some cases, the holes do not close. Then they talk about congenital heart defects. Such patients need to be operated on, since the mixing of blood leads to severe disorders in the cardiovascular system and throughout the body.

The structure of blood vessels

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As the body develops, arteries and veins acquire structural features that distinguish them from each other. Arteries have a dense-elastic consistency, they have strong walls that collapse only when compressed. When the pressure stops, the vessels immediately restore their lumen. In contrast, the veins are softer, their walls are thinner. If blood stops flowing through them, the lumen collapses. It is possible to clearly feel the walls of the vein only when they are well filled with blood, for example, after physical exertion, when applying a tourniquet, or in persons with poorly developed fatty tissue. The lumen of the arteries is thinner than that of the veins.

At 13-16 years old, there is a sharp jump in the growth rate of internal organs. The vascular network sometimes "does not have time" to grow as quickly. For this reason, some “vascular” diseases, such as migraine, may first appear at this age.

In infants, the structure of arteries and veins is very similar. They have thin walls and wide openings. In addition, the venous network as a whole is not as well developed as the arterial network. It is characteristic that in infants during the first months of life, the veins do not shine through the surface of the skin. In them, the outer part of the venous bed is represented not by separate large vessels, but by plexuses consisting of small veins. For this reason, the skin of children so easily turns red and pale, depending on the intensity of the blood supply. With age, the structure of the veins changes, they become larger and less branched. Capillary vessels also have their own differences - they have a rather large lumen, and their walls are thinner and more permeable. Therefore, in children, gas exchange processes are easier and more intense than in adults, although the number of capillaries in a child's body is less than that of a mature one. Capillaries are most developed in the skin, so young children have the ability to breathe through the skin - they receive about 1% of oxygen through the integument of the body. The arteries passing through the heart also have their own characteristics in children. They branch profusely, forming a fairly dense network of capillaries. Since the heart of the child is surrounded by a large amount of soft and loose adipose tissue, this predisposes the children to the development of inflammatory processes. Consequently, in childhood the risk of myocarditis is much higher than in adults. For this reason, it is necessary to carry out the prevention of such violations. First of all, this concerns the timely treatment of accidental viral infections that can cause complications to the heart muscle. As the arteries, capillaries and veins grow, they acquire physiological features characteristic of an adult state, and they increase in length. In addition, additional messages are formed between the vessels - anastomoses. They are a kind of "bridges" through which blood can pass from one vessel to another. Thus, the density of the vascular network increases.

The listed changes in the structure mainly occur during the first year of life, and the second intensive stage occurs at 9-11 years of age. As a rule, by the age of 12, the main anatomical transformations are completed, and then only growth in length occurs. Vessels located in different areas of the body grow differently. For example, the arteries that supply blood to the lungs are most actively elongated during adolescence, and cerebral vessels - at 3-4 years.

Heart rate in children and adolescents

Regardless of age, the activity of the human heart is regulated by two main mechanisms: its ability to automate, i.e., autonomous contractions, and the influences of the autonomic nervous system. The vegetative part of the nervous system is called, which ensures the work of internal organs and does not depend on the will of a person. For example, it is responsible for perspiration, intestinal motility, pupil constriction and dilation, but does not regulate skeletal muscle contraction. In the same way, it provides the functions of the heart and blood vessels. There are two sections in the autonomic nervous system - sympathetic and parasympathetic. The sympathetic department is responsible for reactions associated with tension, stress, active life. When it is excited, reactions such as a decrease in the secretion of digestive juices, inhibition of the motility of the gastrointestinal tract, dilated pupils, vasoconstriction, and increased heart rate occur. The parasympathetic system has opposite effects, its influence prevails at the moment of rest and sleep. The activation of this department causes an increase in the work of the glands and motility, constriction of the pupils, vasodilation and a decrease in the pulse. In adults, these two systems are balanced with each other and turn on “on demand”: when a person experiences stress, his sympathy automatically reacts, and if he sleeps - parasympathetic. But if we talk about newborns and young children, the sympathetic division of the autonomic nervous system always predominates in them. For this reason, their heart rate is higher than that of adults. Over time, the nerve influences become more balanced, as a result, by about the fifth year of life, the pulse becomes less frequent. In children older than 5-6 years, small heart rhythm disturbances sometimes occur, which manifest themselves in the alternation of rapid and slow heartbeats. Moreover, if you remove the ECG, no disturbances, except for frequency fluctuations, will be detected. Such phenomena at this age may be due to the fact that the parasympathetic nervous system "trains" to exert its influence on the heart and at first does not work constantly, but by impulses. This gives rise to periodic slowdowns in the work of the heart. In adolescence, episodes of the so-called respiratory arrhythmia may occur - changes in heart rate depending on the phases of breathing. The heart beats faster during inhalation and slower during exhalation. This is a functional phenomenon; respiratory arrhythmia is the norm, does not affect the condition of the teenager and does not require treatment. In adulthood, it usually disappears or persists only with deep breathing. The tendency to maintain respiratory arrhythmia is more pronounced in individuals with asthenic physique. At birth, the heart rate is 120-140 beats per minute. By the year it decreases only slightly, to 120-125 strokes. In a 2-year-old child, the pulse is recorded with a frequency of 110-115 beats, in a 3-year-old - 105-110. The average heart rate at 5 years old is 100 beats per minute, and at the age of 7 it decreases by another 10-15 beats. In a 12-year-old, it practically approaches the "adult" norms and is 75-80 beats per minute. It is necessary to note such a property of a child's pulse as lability, that is, the ability to change under the influence of various factors. For example, during exercise and excitement, the heart rate increases much faster and to a greater extent than in adults. In infants, it can increase with crying, at the time of sucking, with movements. Lability persists into adolescence.

The pulse in children and adolescents is evaluated according to the same characteristics as in older people. These are frequency, rhythm, symmetry, tension, content, size, form.

Features of blood pressure in childhood and adolescence

The heart of a child is not as powerful as that of an adult. This feature of the heart muscle is due to the small size of the body, the relatively small vascular tone and the absence of sudden loads, which does not give reasons to enhance the function of the organ. Consequently, the child's blood pressure will be below the usual norm - 120/80 mm Hg, taken as the standard for the elders. Despite the relatively low pressure, the blood circulation rate in children is quite high. If, for example, in a 30-year-old man or woman, the blood passes a full circle in 23-24 seconds, then in a 3-year-old child this time is reduced to 15 seconds, and in a baby who has just been born, to 12.

During maturation, blood pressure figures gradually increase, while the first indicator, systolic pressure, increases to the greatest extent. It grows most intensively during the first year, at 10-12 years old and in adolescents. Doctors consider the blood pressure indicator in children to be very important, since it can indirectly judge the physical development of the child and the rate of maturation of the organs of the endocrine system.

In children and adolescents, heart rate and blood pressure may be affected by body position. So, in the prone position, the number of heart beats and blood pressure decrease, and when moving to a vertical position, especially in the first seconds, they increase markedly.

The spread of blood pressure indicators is quite large, therefore, when calculating the norm of pressure for each age, it is better to use not approximate normal values, but calculation using special formulas.

For babies under 1 year old, use the following formula:

BP = 76 + 2n, where n is the child's age in months.

For children older than a year, there are three different formulas. According to the formula proposed by the domestic pediatrician A. M. Popov, BP = 100 + 2n, where n is the child's age in years. According to V. I. Molchanov, pressure is calculated based on the formula 80 + 2n, according to A. B. Volovik - 90 + 2n. For adolescents and adults (from 17 to 79 years old) The calculation is carried out differently. They separately determine systolic and diastolic pressure. So, SBP (systolic blood pressure) \u003d 109 + (0.5 - age in years) + (0.1 - weight in kg). DBP (diastolic blood pressure) \u003d 63 + ( 0.1 - age in years) + (0.15 - weight in kg). During puberty (13-16 years old), systolic pressure no higher than 129 mm Hg can be considered normal. This is a little more than the ideal “adult” pressure, however, after the development of the cardiovascular system, it usually decreases slightly and begins to correspond to the optimal one.

In childhood, blood pressure may vary depending on the sex of the child. After 5 years, boys usually record higher numbers than girls. This difference persists in adults as well.

"Youth Heart"

In adolescence, people may experience various disorders of the cardiovascular system, accompanied by a variety of complaints. At the same time, examining a teenager, doctors do not find serious abnormalities in the state of these organs. Thus, complaints are associated not with organic (accompanied by a change in the structure of the heart and blood vessels), but with functional (arising due to inferior function) disorders. The set of functional disorders of the heart and blood vessels, which are often noted in adolescents, are combined under the name "youthful heart." "Youthful heart" can be considered more of a normal variant than a pathology. Changes in well-being are caused by instability in blood pressure and heart rate, which most often occur due to insufficient maturity, or vice versa, an overactive development of the endocrine system, which, as you know, greatly affects blood pressure and heart rate. A special role in this belongs to the endocrine glands, which are part of the reproductive system - the ovaries and testicles. Intensive development of the gonads can cause hormonal surges that cause poor health, fluctuations in blood pressure, etc. Most often, among the complaints made by adolescents, there are such as a feeling of increased, uneven heartbeat, the appearance of a feeling of "fading" in the chest. There is fatigue, poor exercise tolerance. There may be a lack of air, a tendency to sweat, tingling or discomfort in the left side of the chest. In adolescence, people often begin to tolerate oxygen starvation worse: when they are in a stuffy room and travel in crowded public transport, they experience a feeling of nausea, nausea, fainting. When examining the borders of the heart, they turn out to be normal, and when listening, additional tones and noises that wear unsharp, reversible character. After a more detailed examination (ultrasound of the heart, ECG), no serious pathology is detected. "Youthful heart" does not require special treatment. To alleviate the condition of a teenager, only activities related to lifestyle and daily routine are used. A person should have enough rest, sleep at least 8 hours a day, eat well, be outdoors more often, engage in light jogging, swimming, and outdoor games. Recommended sea bathing, contrast shower.

Hygiene of the cardiovascular system.

The human body has its own individual development from the moment of fertilization to the natural end of life. This period is called ontogeny. It distinguishes two independent stages: prenatal (from the moment of conception to the moment of birth) and postnatal (from the moment of birth to the death of a person). Each of these stages has its own characteristics in the structure and functioning of the circulatory system. I will consider some of them:

Age features in the prenatal stage. The formation of the embryonic heart begins from the 2nd week of prenatal development, and its development in general terms ends by the end of the 3rd week. The blood circulation of the fetus has its own characteristics, primarily due to the fact that before birth, oxygen enters the body of the fetus through the placenta and the so-called umbilical vein. umbilical vein branches into two vessels, one feeds the liver, the other connects to the inferior vena cava. As a result, oxygen-rich blood mixes with blood that has passed through the liver and contains metabolic products in the inferior vena cava. Through the inferior vena cava, blood enters the right atrium. Further, the blood passes into the right ventricle and then is pushed into the pulmonary artery; a smaller part of the blood flows into the lungs, and most through ductus botulinum enters the aorta. The presence of the ductus arteriosus, which connects the artery to the aorta, is the second specific feature in the fetal circulation. As a result of the connection of the pulmonary artery and the aorta, both ventricles of the heart pump blood into the systemic circulation. Blood with metabolic products returns to the mother's body through the umbilical arteries and the placenta.

Thus, the circulation in the body of the fetus of mixed blood, its connection through the placenta with the mother's circulatory system and the presence of the ductus botulinum are the main features of the fetal circulation.

Age features in the postnatal stage . In a newborn child, the connection with the mother's body is terminated and his own circulatory system takes over all the necessary functions. The ductus botulinum loses its functional significance and soon becomes overgrown with connective tissue. 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.

Are there patterns in the growth of the heart? It can be noted that 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.

The shape and position of the heart in the chest also changes. In newborns, the heart is spherical and located much higher than in an adult. These differences are eliminated only by the age of 10.

Functional differences in the cardiovascular system of children and adolescents persist up to 12 years. The heart rate in children is higher than in adults. Heart rate in children is more susceptible to external influences: physical exercise, emotional stress, etc. Blood pressure in children is lower than in adults. Stroke volume in children is much less than in adults. With age, the minute volume of blood increases, which provides the heart with adaptive opportunities for physical activity.

During puberty, the rapid processes of growth and development occurring in the body affect the internal organs and, especially, the cardiovascular system. At this age, there is a discrepancy between the size of the heart and the diameter of the blood vessels. With the rapid growth of the heart, blood vessels grow more slowly, their lumen is not wide enough, and in connection with this, the adolescent's heart bears an additional load, pushing blood through narrow vessels. For the same reason, a teenager may have a temporary malnutrition of the heart muscle, increased fatigue, easy shortness of breath, discomfort in the region of the heart.

Another feature of the cardiovascular system of a teenager is that the heart of a teenager grows very quickly, and the development of the nervous apparatus that regulates the work of the heart does not keep up with it. As a result, adolescents sometimes experience palpitations, abnormal heart rhythms, and the like. All of these changes are temporary and arise in connection with the peculiarity of growth and development, and not as a result of the disease.

Hygiene SSS. For the normal development of the heart and its activity, it is extremely important to exclude excessive physical and mental stress that disrupts the normal pace of the heart, and also to ensure its training through rational and accessible physical exercises for children.

Gradual training of cardiac activity ensures the improvement of the contractile and elastic properties of the muscle fibers of the heart.

Training of cardiovascular activity is achieved by daily physical exercises, sports activities and moderate physical labor, especially when they are carried out in the fresh air.

The hygiene of the circulatory organs in children imposes certain requirements on their clothing. Tight clothing and tight dresses compress the chest. Narrow collars compress the blood vessels of the neck, which affects the blood circulation in the brain. Tight belts compress the blood vessels of the abdominal cavity and thereby impede blood circulation in the circulatory organs. Tight shoes adversely affect blood circulation in the lower extremities.

Conclusion.

Cells of multicellular organisms lose direct contact with the external environment and are in the surrounding liquid medium - intercellular, or tissue fluid, from where they draw the necessary substances and where they secrete metabolic products.

The composition of the tissue fluid is constantly updated due to the fact that this fluid is in close contact with the continuously moving blood, which performs a number of its inherent functions (see Point I. “Functions of the circulatory system”). Oxygen and other substances necessary for cells penetrate from the blood into the tissue fluid; the products of cell metabolism enter the blood flowing from the tissues.

The diverse functions of blood can be carried out only with its continuous movement in the vessels, i.e. in the presence of blood circulation. Blood moves through the vessels due to the periodic contractions of the heart. When the heart stops, death occurs because the delivery of oxygen and nutrients to the tissues, as well as the release of tissues from metabolic products, stops.

Thus, the circulatory system is one of the most important systems of the body.

List of used literature:

1. S.A. Georgieva and others. Physiology. - M.: Medicine, 1981.

2. E.B. Babsky, G.I. Kositsky, A.B. Kogan and others. Human Physiology. - M.: Medicine, 1984

3. Yu.A. Ermolaev Age physiology. - M .: Higher. School, 1985

4. S.E. Sovetov, B.I. Volkov and others. School hygiene. - M .: Education, 1967

During the development of a child, significant morphological and functional changes occur in his cardiovascular system. The formation of the heart in the embryo begins from the second week of embryogenesis and a four-chambered heart is formed by the end of the third week. The blood circulation of the fetus has its own characteristics, primarily related to the fact that before birth, oxygen enters the body through the placenta and the so-called umbilical vein.

The umbilical vein branches into two vessels, one feeding the liver, the other connected to the inferior vena cava. As a result, oxygen-rich blood (from the umbilical vein) and blood flowing from the organs and tissues of the fetus mix in the inferior vena cava. Thus, mixed blood enters the right atrium. As after birth, the atrial systole of the fetal heart directs blood into the ventricles, from there it enters the aorta from the left ventricle, and from the right ventricle into the pulmonary artery. However, the atria of the fetus are not isolated, but are connected using an oval hole, so the left ventricle sends blood to the aorta partially from the right atrium. A very small amount of blood enters the lungs through the pulmonary artery, since the lungs in the fetus do not function. Most of the blood ejected from the right ventricle into the pulmonary trunk, through a temporarily functioning vessel - the ductus botulinum - enters the aorta.

The most important role in the blood supply to the fetus is played by the umbilical arteries, which branch off from the iliac arteries. Through the umbilical opening, they leave the body of the fetus and, branching, form a dense network of capillaries in the placenta, from which the umbilical vein originates. The fetal circulatory system is closed. The mother's blood never enters the fetal blood vessels and vice versa. The supply of oxygen to the blood of the fetus is carried out by diffusion, since its partial pressure in the maternal vessels of the placenta is always higher than in the blood of the fetus.

After birth, the umbilical arteries and vein become empty and become ligaments. With the first breath of a newborn, the pulmonary circulation begins to function. Therefore, usually the botallian duct and the foramen ovale quickly overgrow. 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 heart grows most intensively in the first years of life and at the end of adolescence. The position and shape of the heart also change with age. In a newborn, the heart is spherical in shape and is located much higher than in an adult. Differences in these indicators are eliminated only by the age of ten. By the age of 12, the main functional differences in the cardiovascular system also disappear.

The heart rate (Table 5) in children under 12 - 14 years of age is higher than in adults, which is associated with the predominance of the tone of sympathetic centers in children.

In the process of postnatal development, the tonic influence of the vagus nerve is constantly increasing, and in adolescence, the degree of its influence in most children approaches the level of adults. A delay in the maturation of the tonic influence of the vagus nerve on cardiac activity could indicate a retardation of the child's development.

Table 5

Resting heart rate and respiration rate in children of different ages.

Table 6

The value of blood pressure at rest in children of different ages.

Blood pressure in children is lower than in adults (Table 6), and the rate of circulation is higher. The stroke volume of blood in a newborn is only 2.5 cm3, in the first year after birth it increases four times, then the growth rate decreases. To the level of an adult (70 - 75 cm3), stroke volume approaches only 15 - 16 years. With age, the minute volume of blood also increases, which provides the heart with increasing opportunities for adaptation to physical exertion.

Bioelectrical processes in the heart also have age-related features, so the electrocardiogram approaches the form of an adult by the age of 13-16.

Sometimes in the pubertal period there are reversible disturbances in the activity of the cardiovascular system associated with the restructuring of the endocrine system. At the age of 13-16, there may be an increase in heart rate, shortness of breath, vasospasm, violations of the electrocardiogram, etc. In the presence of circulatory dysfunctions, it is necessary to strictly dose and prevent excessive physical and emotional stress in a teenager.

The cardiovascular system with its multilevel regulation is a functional system, the end result of which is to provide a given level of functioning of the whole organism. Possessing complex neuro-reflex and neurohumoral mechanisms, the circulatory system provides timely adequate blood supply to the relevant structures. Other things being equal, we can assume that any given level of functioning of the whole organism corresponds to an equivalent level of functioning of the circulatory apparatus (Baevsky R.M., 1979). The human heart is a four-chamber muscular hollow organ. In an adult, it has a mass of 250-300 grams, a length of 12-15 cm. The size of a person's heart approximately corresponds to the size of his clenched fist. The heart consists of the left atrium and left ventricle, the right atrium and the right ventricle.

There are age-related features of the location, condition, weight and function of the heart. The heart of a newborn differs from the heart of an adult in shape, mass and location. It has an almost spherical shape, its width is somewhat greater than its length. In the process of growth and development of the child, the mass of the heart increases. The growth rate of the heart is especially high in the first years of life and during puberty. At the age of 14-15, there is a particularly sharp increase in the size of the heart. Slower heart grows from 7 to 12 years. So, for example, in boys 9-19 years old, the heart mass is 111.1 grams, which is 2 times less than in adults (244.4 grams). Along with this, the ratio of the growth of the heart departments changes. The growth of the atria during the first year of life outstrips the growth of the ventricles, then they grow almost equally, and only after 10 years the growth of the ventricles begins to overtake the growth of the atria. The histological structure of the heart is rebuilt, so, to the greatest extent, the increase in the mass of the heart sections occurs due to the left ventricle.

The main mass of the wall of the heart is a powerful myocardial muscle. The heart muscle of children is characterized by a high level of energy consumption, which determines the significant stress of oxidative processes in the myocardium. This is reflected in the large consumption of oxygen by the muscle. The heart muscle continues to develop and differentiate up to 18-20 years (Farber D.A., 1990).

The bulk of the heart muscle is represented by fibers typical of the heart, which provide contraction of the heart. Their main function is contractility. The heart contracts rhythmically: the contraction of the heart alternates with their relaxation. Contraction of the heart is called systole, and relaxation is called diastole. Each of these periods, in turn, is divided into a number of phases and intervals that characterize various aspects of the activity of the heart. During the total systole of the ventricles, there are two periods that are different in their physiological essence: the period of tension and the period of exile. During a period of tension, the heart prepares for the expulsion of blood into the great vessels. At the beginning of the tension period, depolarization of the fibers of the heart muscle occurs and the contraction of the ventricular myocardium begins. This part of the voltage period is referred to as the asynchronous contraction phase. As soon as the optimal number of myocardial fibers is in a tense state, the atrioventricular valves close and the second part of the tension period begins - the isometric contraction phase. During this phase, the intraventricular pressure rises to the pressure in the aorta. As soon as the pressure in the ventricle exceeds the pressure in the aorta, its valves open and the second period of systole begins - the period of exile.

The duration of diastole is determined by subtracting the duration of the total systole from the total duration of the cardiac cycle. The cardiac cycle is the period of one contraction and relaxation of the heart. The total duration of the cardiac cycle increases with age, the duration of the period of exile increases accordingly. Some researchers believe that the duration of the exile period is due to a number of factors. In particular, Kositsky G.I. (1985), examining age-related changes in the structure of the cardiac cycle, came to the conclusion that in addition to slowing the heart rate, the duration of systole is influenced by age-related changes in hemodynamics: the lengthening of the period of exile in children with age is associated with an increase in cardiac output. The duration of the stress period, according to most authors, increases with age. Some researchers assign the main role in the age dynamics of the stress period to an increase in the duration of the cardiac cycle, others believe that the change in the duration of the stress period is also due to shifts in hemodynamic parameters, such as the volume of the ventricles of the heart and the maximum pressure in the aorta.

The total duration of the cardiac cycle in schoolchildren begins to gradually increase from 7 to 8-9 years, after which it increases sharply at 10 years. In the future, a significant lengthening of cardio intervals occurs at the age of 14-16, when the heart rate is set at a level close to its values ​​in adults (IO Tupitsin, 1985).

Functional differences in the cardiovascular system of children and adolescents persist up to 12 years. The heart rate in children is higher than in adults, which is associated with the predominance of sympathetic nerve tone in children. During the postnatal period, the tonic effect on the heart of the vagus nerve gradually increases (N.P. Gundobin, 1906). the vagus nerve begins to exert a noticeable influence from 2-4 years old, and at a younger age its influence approaches the level of an adult. A delay in the formation of the tonic influence of the vagus nerve on cardiac activity may indicate a delay in the physical development of the child (Ferber D.A. et al., 1990). a low functional reserve of adrenergic influences on the heart rhythm with a corresponding restructuring of metabolism and an increase in its contractile capacity, at the age of 14 - a significant weakening of adrenergic influences and an increase in the tone of the parasympathetic system.

A.S. Golenko (1988) presented the results of a pedagogical experiment conducted to control changes in the static parameters of the heart rate in a state of relative rest before and after exercise. These results indicated that the change in sympathetic and parasympathetic influences on the sinus node and the weakening of centralization in the control of the heart rate by the end of the experiment in girls were less pronounced than in boys. According to Golenko A.S. (1988), at the age of 10-13 years, girls have a clear centralization of heart rate control.

Heart rate in children is more influenced by external influences: physical exercise, emotional stress. Emotional influences lead, as a rule, to an increase in the frequency of cardiac activity. It increases significantly during physical work and decreases with a decrease in the ambient temperature.

The normal heart rate for an adult is 75 times per minute. In a newborn, it is much higher - 140 times per minute. Intensively decreasing during the first years of life, by the age of 8-10 it is 85-90 beats per minute, and by the age of 15 it approaches the value of an adult. With the contraction of the heart in an adult at rest, each ventricle pushes out 60-80 cubic meters. see blood. Blood pressure in children is lower than in adults, and the blood circulation rate is higher (in a newborn, the linear blood flow velocity is 12 s, in 3-year-olds - 15 s, in 14-year-olds - 18.5 s). The stroke volume (the amount of blood ejected by the ventricles in one contraction) in children is much less than in an adult. In a newborn, it is only 2.5 cubic meters. see, during the first year of postnatal development, it increases by 4 times, then the rate of its increase decreases, but it continues to grow until the age of 15-16, only at this stage the stroke volume approaches the level of an adult. With age, the minute and reserve blood volume increase, which provides the heart with increasing adaptive capacity to stress (Yu.A. Ermalaev, 1985). Children and adolescents respond to dynamic physical activity with an increase in heart rate, maximum blood pressure (stroke volume), than younger children, the more, even to less physical activity, they respond with an increase in heart rate, a smaller increase in stroke volume, providing approximately the same increase minute volume. The increase in minute volume in trained people occurs mainly due to an increase in systolic volume. At the same time, heart rate increases slightly. In untrained people, the minute volume of blood increases mainly due to increased heart rate. It is known that with an increase in heart rate, the duration of the general pause of the heart is shortened. It follows from this that the heart of untrained people works less economically and wears out faster. It is no coincidence that cardiovascular diseases are much less common in athletes than in people who are not involved in physical education. In well-trained athletes with great physical exertion, the stroke volume of blood can increase up to 200-300 cc.

Static load (and full tension also belongs to it) is accompanied by other resections of the cardiovascular system. Static load, unlike dynamic load, increases both maximum and minimum blood pressure. This is how schoolchildren of all ages react even to a light static load equal to 30% of the maximum compression force of the dynamometer. At the same time, at the beginning of the academic year, the change in hemodynamic parameters is less sharp than at the end of the year. At the beginning of the year, for example, in boys 8-9 years old, the minimum pressure increases by 5.5% and the maximum by 10%, and at the end of the year, by 11 and 21%, respectively, for the specified static load. Such a reaction is recorded for more than 5 minutes after the cessation of exposure to static force. Prolonged postural tension is accompanied by a spasm of arterioles in schoolchildren, which leads to a general increase in blood pressure. An increase in motor activity during training sessions is one of the measures to prevent cardiovascular disorders in students, in particular, the development of hypertension (A.G. Khripkova, 1990).

The state of the cardiovascular system is influenced by a dosed mental load, and the degree of change in hemodynamic parameters depends on the nature of the duration and intensity of the load. Analysis of studies conducted by Gorbunov N.P. together with Batenkova I.V. (2001) testified that the heart and blood vessels of junior schoolchildren subtly respond to mental stress. The most significant changes in the course of mental load are subject to cardiac output, an increase in which was noted in all the children studied. The degree of increase in cardiac output during the performance of the task depended on the age of the children and on the period of the school year. It has been established that during the academic year, students of the 1st grade undergo changes in the indicators of central hemodynamics, while the heart rate decreases, the maximum arterial pressure decreases, and the cardiac output increases.

In the second year of study, the maximum arterial pressure decreases, and the heart rate does not change significantly. In students of grades 3-4, the maximum blood pressure decreased, the heart rate decreased, and there was a decrease in cardiac output. Adaptive changes in the indicators of central hemodynamics in younger schoolchildren consist in slowing down the heart rate, lowering the maximum blood pressure, and increasing cardiac output. If we trace the age-related shifts in central hemodynamics according to the results obtained at the beginning of each academic year, we can see that adaptive shifts are not accompanied by a violation of the general age-related trend of increasing blood pressure and cardiac output with age while slowing down the heart rate.

The change in the functional state of the cardiovascular system in children and adolescents in the process of their adaptation to mental and physical stress is influenced in certain years of study by gender. According to the work of P.K. Prusova (1987), the dependence of the state of the cardiovascular system on the degree of puberty of adolescents training for endurance, the improvement of the functioning of the cardiorespiratory system does not always occur in parallel with the increase in the degree of puberty. So, at the time of the appearance of secondary signs of puberty, the sympathetic tone of the autonomic nervous system increases and is most pronounced during puberty. The intensity of the functioning of the cardiorespiratory system increases with an increase in the degree of puberty, and in the subsequent period it begins to decrease, a tendency towards more economical functioning appears. The study of regional blood circulation showed a decrease in the volumetric blood flow velocity with age at rest, which also indicates the economization of the blood circulation functions, which occurs as the child develops. The study of cerebral blood flow confirmed its qualitative changes that occur during the growth of the child, as well as the interhemispheric asymmetry of the brain blood supply characteristic of children.

The important role that the heart plays in the body dictates the need for preventive measures that contribute to its normal function, strengthen it, and protect against diseases that cause organic changes in the valvular apparatus and the heart muscle itself. Physical training and labor within the age limits of permissible physical activity is the most important measure to strengthen the heart.