V. Age features of the circulatory system

From prenatal development to old age, age-related features are observed. cordially- vascular system. Every year there are new changes that ensure the normal functioning of the body.

The aging program is embedded in the human genetic apparatus, which is why this process is an invariable biological law. According to gerontologists real term life expectancy is 110-120 years, but this moment depends only on 25-30% of inherited genes, everything else is the influence of the environment, which affects the fetus in the womb. After birth, you can add on environmental and social conditions, health status, etc.

If you add everything together, not everyone can live more than a century, and there are reasons for that. Today we will consider the age-related features of the cardiovascular system, since the heart with numerous vessels is the “engine” of a person, and life is simply impossible without its contractions.

How does the fetal cardiovascular system develop in the womb?

Pregnancy is physiological period, in which a new life begins to form in the body of a woman.

All intrauterine development can be divided into two periods:

• embryonic– up to 8 weeks (embryo);
• fetal- from 9 weeks to childbirth (fetus).

The heart of the future man begins to develop as early as the second week after the fertilization of the egg by the spermatozoon in the form of two independent heart germs, which gradually merge into one, forming a semblance of a fish heart. This tube grows rapidly and gradually moves down into the chest cavity, where it narrows and bends, taking on a certain shape.

At week 4, a constriction is formed, which divides the organ into two sections:

• arterial;
• venous.

At week 5, a septum appears, with the help of which the right and left atrium appears. It is at this time that the first pulsation of a single-chamber heart begins. At week 6, heart contractions become more intense and clearer.

And by the 9th week of development, the baby has a full four-chamber human heart, valves and vessels to move blood in two directions. The complete formation of the heart ends at week 22, then only the muscle volume increases and the vascular network expands.

You need to understand that such a structure of the cardiovascular system implies some distinctive features:

1. Prenatal development is characterized by the functioning of the "mother-placenta-child" system. Through the umbilical vessels, oxygen, nutrients, as well as toxic substances (medications, alcohol breakdown products, etc.).
2. Only 3 channels work - an open oval ring, botalla (arterial) and arantia (venous) duct. This anatomy creates parallel blood flow as blood flows from the right and left ventricles to the aorta and then through the systemic circulation.
3. Arterial blood flows from mother to fetus umbilical vein, and saturated with carbon dioxide and metabolic products returns to the placenta through 2 umbilical arteries. Thus, we can conclude that the fetus is supplied with mixed blood, when, after birth, arterial blood flows strictly through the arteries, and venous blood through the veins.
4. The pulmonary circulation is open, but a feature of hematopoiesis is the fact that oxygen is not wasted on the lungs, which during intrauterine development do not perform the function of gas exchange. Although not accepted a large number of blood, but this is due to the high resistance created by non-functioning alveoli (respiratory structures).
5. The liver receives about half of the total blood delivered to the baby. Only this organ boasts the most oxygenated blood (about 80%), while others feed on mixed blood.
6. It is also a feature that the blood contains fetal hemoglobin, which differs best ability bind with oxygen. This fact is connected with the special sensitivity of the fetus to hypoxia.

It is this structure that allows the baby to receive vital oxygen with nutrients from the mother. The development of the baby depends on how well a pregnant woman eats and leads a healthy lifestyle, and the price, mind you, is very high.

Life after birth: features in newborns

Termination of the connection between the fetus and the mother begins immediately with the birth of the baby and as soon as the doctor bandages the umbilical cord.

1. With the first cry of the baby, the lungs open and the alveoli begin to function, reducing resistance in the pulmonary circulation by almost 5 times. In this regard, the need for the arterial duct stops, as it was necessary before.
2. The heart of a newborn baby is relatively large and equals approximately 0.8% of body weight.
3. The mass of the left ventricle is greater than the mass of the right.
4. A full circle of blood circulation is carried out in 12 seconds, and blood pressure averages 75 mm. rt. Art.
5. The myocardium of the born baby is presented in the form of undifferentiated syncytium. Muscle fibers are thin, do not have transverse striation and contain a large number of nuclei. Elastic and connective tissue is not developed.
6. From the moment the pulmonary circulation is launched, active substances are released that provide vasodilatation. Aortic pressure significantly exceeds compared with the pulmonary trunk. Also, features of the neonatal cardiovascular system include closure of bypass shunts and overgrowth of the annulus ovale.
7. After birth, well developed and located superficially subpapillary venous plexuses. The walls of the vessels are thin, elastic and muscle fibers are poorly developed in them.

Attention: the cardiovascular system has been improving for a long time and completes its full formation in adolescence.

What changes are typical for children and adolescents

The most important function of the circulatory organs is to maintain a constancy of the body's environment, the delivery of oxygen and nutrients to all tissues and organs, the excretion and removal of metabolic products.

All this happens in close interaction with the digestive, respiratory, urinary, vegetative, central, endocrine system etc. Growth and structural change The cardiovascular system is especially active in the first year of life.

If we talk about the features in children's, preschool and teenage years, the following distinguishing features can be distinguished:

1. By 6 months, the mass of the heart is 0.4%, and by 3 years and beyond, about 0.5%. The volume and mass of the heart increases most intensively in the first years of life, as well as in adolescence. In addition, it happens unevenly. Up to two years, the atria grow more intensively, from 2 to 10 years the entire muscular organ generally.
2. After 10 years, the ventricles increase. The left one is also growing faster than the right one. Speaking of percentage walls of the left and right ventricles, the following figures can be noted: in a newborn - 1.4: 1, at 4 months of life - 2: 1, at 15 years old - 2.76: 1.
3. All periods of growing up in boys, the size of the heart is larger, with the exception of from 13 to 15 years old, when girls begin to grow faster.
4. Up to 6 years, the shape of the heart is more rounded, and after 6 it acquires an oval, characteristic of adults.
5. Up to 2-3 years, the heart is located in horizontal position on a raised diaphragm. By the age of 3-4, due to an increase in the diaphragm and its lower standing, the heart muscle acquires an oblique position with a simultaneous flip around the long axis and the location of the left ventricle forward.
6. Up to 2 years coronary vessels located along loose type, from 2 years to 6 they are distributed according to mixed, and after 6 years the type is already main, characteristic of adults. The thickness and lumen of the main vessels increase, and the peripheral branches are reduced.
7. In the first two years of a baby's life, differentiation and intensive growth of the myocardium occurs. A transverse striation appears, muscle fibers begin to thicken, a subendocardial layer and septal septa are formed. From 6 to 10 years, the gradual improvement of the myocardium continues and, as a result, histological structure becomes adult.
8. Up to 3-4 years, the instruction for the regulation of cardiac activity involves the innervation of the nervous sympathetic system, with which the physiological tachycardia in babies of the first years of life is connected. By the age of 14-15, the development of the conductor system ends.
9. Children early age have a relatively wide lumen of the vessels (in adults 2 times already). Arterial walls are more elastic and that is why the rate of blood circulation, peripheral resistance and blood pressure are lower. Veins and arteries grow unevenly and do not match the growth of the heart.
10. Capillaries in children are well developed, the shape is irregular, tortuous and short. With age, they settle deeper, elongate and take on a hairpin shape. The permeability of the walls is much higher.
11. By the age of 14 full circle circulation is 18.5 seconds.

The heart rate at rest will be equal to the following numbers:

Heart rate according to age. You can learn more about the age-related characteristics of the cardiovascular system in children from the video in this article.

Cardiovascular system in adults and the elderly

Age classification according to WHO is equal to the following data:

1. Young age from 18 to 29 years.
2. Mature age from 30 to 44 years.
3. Average age from 45 to 59 years.
4. Elderly age from 60 to 74 years.
5. Senile age from 75 to 89 years.
6. Long-livers from 90 years and older.

All this time cardiovascular work undergoes changes and has some features:

1. During the day, the heart of an adult pumps more than 6,000 liters of blood. Its dimensions are equal to 1/200 of the body part (for men, the mass of the organ is about 300 g, and for women, about 220 g). The total volume of blood in a person weighing 70 kg is 5-6 liters.
2. The heart rate in an adult is 66-72 beats. in min.
3. At the age of 20-25, the valve flaps become denser, become uneven, and in the elderly and old age partial muscle atrophy occurs.
4. From the age of 40, calcium deposits begin, at the same time, atherosclerotic changes in the vessels progress (see), which leads to a loss of elasticity of the blood walls.
5. Such changes entail an increase in blood pressure, especially this trend is observed from the age of 35.
6. With aging, the number of red blood cells decreases, and, consequently, hemoglobin. In this regard, drowsiness, fatigue, dizziness may be felt.
7. Changes in the capillaries make them permeable, which leads to a deterioration in the nutrition of body tissues.
8. Changes with age and contractility myocardium. In adults and the elderly, cardiomyocytes do not divide, so their number may gradually decrease, and connective tissue is formed at the site of their death.
9. The number of cells of the conducting system begins to decrease from the age of 20, and in old age their number will be only 10% of the original number. All this creates the prerequisites for the violation of the rhythm of the heart in old age.
10. Starting from the age of 40, the efficiency of the cardiovascular system decreases. Increases endothelial dysfunction, both in large and small vessels. This affects changes in intravascular hemostasis, increasing the thrombogenic potential of the blood.
11. Due to the loss of elasticity of large arterial vessels, cardiac activity becomes less and less economical.

Features of the cardiovascular system in the elderly are associated with a decrease in the adaptive capacity of the heart and blood vessels, which is accompanied by a decrease in resistance to unfavorable factors. It is possible to ensure maximum life expectancy by preventing the occurrence of pathological changes.

According to cardiologists, in the next 20 years, diseases of the cardiovascular system will determine almost half of the mortality of the population.

Attention: for 70 years of life, the heart pumps about 165 million liters of blood.

As we can see, the features of the development of the cardiovascular system are really amazing. It is amazing how clearly nature has planned all the changes to ensure normal life person.

To prolong your life and ensure a happy old age, you need to follow all the recommendations for healthy lifestyle life and heart health.

In this part we are talking about the features of the morphological development of the cardiovascular system: about changes in blood circulation in a newborn; about the position, structure and size of the child's heart in postnatal period; O age-related changes heart rate and duration cardiac cycle; about age characteristics external manifestations activity of the heart.

Features of the morphological development of the cardiovascular system.

Changes in blood circulation in a 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 primarily associated with the inclusion 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 altered 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, turn into ligaments. So at the time of birth, the fetal circulatory system acquires all the features of its structure in an adult.

The position, structure and size of the child's heart in the postnatal period.

The heart of a newborn differs from that of an adult in shape, relative mass, and location. It has almost spherical shape, its width is somewhat greater than its length. The walls of the right and left ventricles are the same in thickness.

In a newborn, the heart is very high due to the high position of the arch 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 vertical position(the child is sitting, standing) the heart is in an oblique position. By the age of 2-3, its apex reaches the 5th left rib, by the age of 5 it shifts to the fifth left intercostal space. In 10-year-old children, the boundaries of the heart are almost the same as in adults.

From the moment of separation of the large and small circles of blood circulation, the left ventricle performs significantly great job than the right one, since the resistance in the large circle is greater than in the small one. In this regard, the muscle of the left ventricle develops intensively, and by six months of life the ratio of the wall of the right and left ventricles becomes the same as in an adult - 1: 2.11 (in a newborn it is 1: 1.33). The atria are more developed than the ventricles.

The mass of the heart of a newborn is on average 23.6 g (fluctuations are possible from 11.4 to 49.5 g) and is 0.89% of body weight (in an adult, this percentage ranges from 0.48 to 0.52%). With age, the mass of the heart increases, especially the mass of the left ventricle. During the first two years of life, the heart grows rapidly, and the right ventricle is somewhat behind in growth from the left.

By 8 months of life, the mass of the heart doubles, by 2-3 years - by 3 times, by 5 years - by 4 times, by 6 - by 11 times. From 7 to 12 years of age, the growth of the heart slows down and somewhat lags behind the growth of the body. At the age of 14-15 - during puberty - an increased growth of the heart occurs again. Boys have a larger heart than girls. But at the age of 11, girls begin a period of increased heart growth (for 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 in boys again becomes heavier than in girls.

Age-related changes in heart rate and duration of the cardiac cycle.

In the fetus, the heart rate ranges from 130 to 150 beats per minute. At different times of the day, it can differ in the same fetus by 30-40 contractions. At the moment of fetal movement, it increases by 13-14 beats per minute. With a short-term holding of breath in the mother, the heart rate of the fetus increases by 8-11 beats per minute. The muscular work of the mother does not affect the heart rate of the fetus.

In a newborn, the heart rate is close to its value in the fetus and is 120-140 beats per minute. Only during the first few days there is a temporary slowdown in heart rate to 80-70 beats per minute.

A high heart rate in newborns is associated with an intensive metabolism and the absence of influences from the vagus nerves. But if in the fetus the heart rate is relatively constant, then in the newborn it easily changes under the influence of various stimuli acting on the receptors of the skin, organs of vision and hearing, olfactory, gustatory and on the receptors of internal organs.

With age, the heart rate decreases, and in adolescents it approaches the value of adults.

Changes in heart rate in children with age.

The decrease in the number of heartbeats with age is associated with the influence of vagus nerve on the heart. Gender differences in heart rate were noted: in boys it is less frequent 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. From to school age and up to 14 years it is significant. At the age of 15-16 there are only isolated cases respiratory arrhythmias.

In children, the heart rate is subject to large changes under the influence of various factors. Emotional influences lead, as a rule, to an increase in the rhythm of cardiac activity. It increases significantly with increasing temperature. external environment and during physical work and decreases with decreasing temperature. The heart rate during physical work increases to 180-200 beats per minute. This is due to the insufficient development of mechanisms that provide an increase in oxygen consumption during operation. In older children, more advanced regulatory mechanisms ensure a rapid restructuring of the cardiovascular system in accordance with physical activity.

Due to the high heart rate in children, the duration of the entire cycle of contractions is much less than in adults. If in an adult it leaves 0.8 seconds, then in the fetus - 0.46 seconds, in a newborn child - 0.4-0.5 seconds, in 6-7-year-old children the duration of the cardiac cycle is 0.63 seconds, in children 12 years of age - 0.75 sec, i.e. its size is almost the same as in adults.

In accordance with the change in the duration of the cycle of heart contractions, the duration of its individual phases also changes. By the end of pregnancy in the fetus, the duration of ventricular systole is 0.3-0.5 seconds, and diastole - 0.15-0.24 seconds. The phase of ventricular tension in a newborn lasts - 0.068 seconds, and in infants - 0.063 seconds. The ejection phase in newborns is carried out in 0.188 seconds, and in infants - in 0.206 seconds. Changes in the duration of the cardiac cycle and its phases in other age groups are shown in the table.

The duration of individual phases of the cardiac cycle (in sec) in children of different age groups (according to B.L. Komarov)

With intensive muscle load phases of the cardiac cycle are shortened. The duration of the tension phase and the exile phase at the beginning of work is especially sharply reduced. After some time, their duration slightly increases and becomes stable until the end of the work.

Age features of external manifestations of the activity of the heart.

Cardiac push It is clearly visible to the eye in children and adolescents with poorly developed subcutaneous adipose tissue, and in children with good fatness, the heart impulse is easily determined by palpation.

In newborns and children up to 2-3 years of age, a cardiac impulse is felt in the 4th left intercostal space 1-2 cm outside the nipple line, in children 3-7 years of age and subsequent age groups it is determined in the 5th intercostal space , somewhat varying outside and inside from the nipple line.

Heart sounds children are somewhat shorter than adults. If in adults the first tone lasts 0.1-0.17 seconds, then in children it is 0.1-0.12 seconds.

The second tone in children is longer than in adults. In children, it lasts 0.07-0.1 seconds, and in adults - 0.06-0.08 seconds. Sometimes in children from 1 to 3 years old, there is a splitting of the second tone, associated with a slightly different closure of the semilunar valves of the aorta and pulmonary artery, and a splitting of the first tone, which is due to asynchronous closure of the mitral and tricuspid valves.

Often a third tone is recorded in children, very quiet, deaf and low. It occurs at the beginning of diastole 0.1-0.2 sec after the second tone and is associated with rapid stretching of the ventricular muscle that occurs when blood enters them. In adults, the third tone lasts 0.04-0.09 seconds, in children 0.03-0.06 seconds. In newborns and infants, the third tone is not audible.

During muscle work, positive and negative emotions, the strength of heart tones increases, during sleep it decreases.

Electrocardiogram children differs significantly from the electrocardiogram of adults and in various age periods has its own characteristics in connection with a change in the size of the heart, its position, regulation, etc.

In the fetus, an electrocardiogram is recorded at the 15-17th week of pregnancy.

The time of conduction of excitation from the atria to the ventricles (P-Q interval) in the fetus is shorter than in the newborn. In newborns and children of the first three months of life, this time is 0.09-0.12 seconds, and in older children - 0.13-0.14 seconds.

The QRS complex in newborns is shorter than in older ones. Separate teeth of the electrocardiogram in children of this age are different in different leads.

In infants, the P wave remains strongly pronounced in the electrocardiogram, which explains larger atria. The QRS complex is often polyphasic, with an R wave predominating. Changes in the QRS complex are associated with uneven growth conducting system of the heart.

IN preschool age the electrocardiogram of most children of this age is characterized by a slight decrease in the P and Q waves. The R wave increases in all leads, which is associated with the development of the left ventricular myocardium. At this age, the duration of the QRS complex increases and interval P-Q, which depends on the fixation of the influence of the vagus nerve on the heart.

In school-age children, the duration of the cardiac cycle (R-R) increases even more and averages 0.6-0.85 sec. The value of the R wave in the first lead in adolescents approaches its value in an adult. The Q wave decreases with age, and in adolescents also approaches its size in an adult.

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The cardiovascular system (circulatory system) consists of the heart and blood vessels: arteries, veins, and capillaries.

Heart - a hollow muscular organ that looks like a cone, located in the chest cavity behind the sternum. It is freely suspended on the vessels and can shift somewhat. The mass of the heart depends on age, sex, body size and physical development, in an adult, the mass is 250-300 g.

The heart is placed in the pericardial sac, which has two sheets: external (pericardium)- fused with the sternum, ribs, diaphragm; internal (epicardium)- covers the heart and fuses with its muscle. Between the sheets there is a gap filled with fluid, which facilitates the sliding of the heart during contraction and reduces friction.

The heart is divided by a solid partition into two halves: right and left. Each half consists of two chambers: the atrium and the ventricle, which in turn are separated by cusp valves. IN right atrium fall into upper And inferior vena cava, and four on the left pulmonary veins. Out of the right ventricle pulmonary trunk (pulmonary artery), A from the left aorta. In the place where the vessels exit, are located semilunar valves.

The main function of the heart is to ensure the continuous movement of blood through the vessels. The heart beats rhythmically due to alternating atrial and ventricular contractions. The contraction of the heart is called systole relaxation - diastole. During atrial contraction, the ventricles relax and vice versa. There are three phases of cardiac activity:

1. Atrial systole - 0.1 s.

2. Ventricular systole - 0.3 s.

3. Atrial and ventricular diastole (general pause) - 0.4 s.

The heart rate (HR), or pulse, in an adult at rest is 60-80 beats per minute. The heart has its own conduction system, which provides property of automation(the ability of an organ to be excited without the participation of an external stimulus under the influence of impulses that arise in them themselves).

Blood moves through the vessels that form the large and small circles of blood circulation.

big circle blood circulation begins from the left ventricle with the aorta, from which arteries of a smaller diameter depart, carrying arterial (oxygen-rich) blood to the head, neck, limbs, organs of the abdominal and chest cavities, and the pelvis. As they move away from the aorta, the arteries branch into more small vessels- arterioles, and then capillaries, through the wall of which there is an exchange between blood and interstitial fluid. The blood gives off oxygen and nutrients and takes carbon dioxide and products of cell metabolism. As a result, the blood becomes venous (saturated with carbon dioxide). The capillaries merge into venules and then into veins. Venous blood from the head and neck is collected in the superior vena cava, and from lower extremities, pelvic organs, chest and abdominal cavity- into the inferior vena cava. The veins empty into the right atrium. Thus, the systemic circulation starts from the left ventricle and pumps into the right atrium.

Small circle of blood circulation It begins with the pulmonary artery from the right ventricle, which carries venous (oxygen-poor) blood. Branching into two branches going to the right and left lung, the artery divides into smaller arteries, arterioles and capillaries, from which carbon dioxide is removed in the alveoli and oxygen enriched with air during inspiration occurs.

Pulmonary capillaries pass into venules, then form veins. The four pulmonary veins supply oxygen-rich arterial blood to the left atrium. Thus, the pulmonary circulation starts from the right ventricle and ends in the left atrium.

External manifestations of the work of the heart are not only cardiac impulse and pulse, but also blood pressure. Blood pressure The pressure exerted by blood on the walls of the blood vessels through which it moves. In the arterial part of the circulatory system, this pressure is called arterial. Value blood pressure is determined by the strength of heart contractions, the amount of blood and the resistance and elasticity of blood vessels, blood viscosity. Most high pressure observed at the time of ejection of blood into the aorta; the minimum - at the moment when the blood reaches the hollow veins.

Distinguish between upper (systolic) pressure and lower (diastolic) pressure. Systolic is higher than diastolic. SD is mainly determined by the work of the heart, and DD depends on the state of the vessels, their resistance to fluid flow. The difference between SD and DD is pulse pressure. The smaller its value, the less blood enters the aorta during systole. Blood pressure can change depending on the influence of external and internal factors. So, it increases with muscle activity, emotional excitement, voltage, etc. healthy person pressure is maintained at a constant level (120/70 mm Hg) due to the functioning of regulatory mechanisms.

Ontogenetic features of blood circulation in humans

Age features The functioning of the CCC of a growing organism is due to a 2-fold increase in oxygen demand in comparison with an adult.

WITH With age, the duration of the cardiac cycle increases due to diastole. This allows the growing ventricles to fill with more blood.

The density of capillaries mature age increases and then decreases, their volume and surface in each successive age group decrease. There is also some deterioration in capillary permeability, and the intercapillary distance increases.

Throughout life, the thickness of the arterial wall and its structure slowly change. The thickening of the arterial wall is determined mainly by the thickening and growth of the elastic plates. This process ends with the onset of maturity.

The development of the vessels of the heart and their regulation is reflected in many functions. For example, in children, due to the immaturity of vasoconstrictor mechanisms and dilated skin vessels, heat transfer is increased, so hypothermia can occur very quickly.

A distinctive feature of the structure of the fetal heart is the presence of an oval hole between the right and left atria. Most of the blood from the right atrium flows through the OO into the left atrium. There is also a small amount venous blood from the pulmonary veins. From the left atrium, blood enters the left ventricle, from it into the aorta and moves through the vessels of the BCC, from the arteries of which the umbilical arteries branch off, leading to the placenta.

At the time of birth, the fetal circulatory system acquires all the features of its structure in adults. After the birth, the heart of the child grows and enlarges, the processes of shaping take place in it. The heart of a newborn has a transverse position and a spherical shape, this is due to the fact that a relatively large liver makes high vault diaphragm, so the heart of the newborn is at the level of the 4th left intercostal space.

From the moment of separation of the large and small circles of blood circulation, the left ventricle performs much more work than the right one, and therefore the muscle of the left ventricle develops intensified.

With age, the mass of the heart increases, especially the mass of the left ventricle. By the age of 2-3, the mass of the heart increases by 3 times, by 6 - by 11 times. From 7 to 12 years of age, the growth of the heart slows down and somewhat lags behind the growth of the body. At the age of 14-15, the increased growth of the heart begins again. Boys have more heart mass than girls.

Small mass and systolic volume (10 ml) of the heart of a newborn with increased need in the supply of oxygen to the body, heart rate is compensated. A newborn has a heart rate of 120-140 beats per minute. However, more elastic vessels the child facilitates the work of the heart, and in a child of the first year of life, the maximum blood pressure is low - 70-80 mm Hg. St., the circulation time is 12 s, which is 2 times faster than that of an adult. With age nervous regulation cardiac activity improves and by the age of 14, the heart rate reaches 80 beats per minute, and BP105/60 mm Hg. Art., the mass of the heart increases, but the force of its contraction is still insufficient.

During puberty, there is a disproportion in the development of the body, heart and blood vessels. With an increase in body height, the vessels lengthen and become narrow, which leads to an increase in resistance to blood flow, an increase in the load on the heart and a deterioration in the blood supply to tissues. During this period, when sex hormones enter the bloodstream, vasospasms additionally occur. various areas body, including the vessels of the brain and heart. At excessive loads Adolescents may have fainting spells, palpitations, and abnormal heart rhythms and other CVS disorders. Smoking and drug and alcohol use may exacerbate these disorders.

By the age of 18-21, CCC indicators approach those of adults.

The cardiovascular system is a system of organs that circulate blood and lymph throughout the body.

The cardiovascular system consists of blood vessels and the heart, which is the main organ of this system.

The main function of the circulatory system is to provide organs with nutrients, biologically active substances, oxygen and energy; and also with the blood, decay products “leave” the organs, heading to the departments that remove harmful and unnecessary substances from the body.

The heart is a hollow muscular organ capable of rhythmic contractions, ensuring the continuous movement of blood within the vessels. Healthy heart is a strong, continuously working body, the size of a fist and weighing about half a kilogram. The heart consists of 4 chambers. A muscular wall called the septum divides the heart into left and right right half. Each half has 2 chambers. The upper chambers are called the atria, the lower chambers are called the ventricles. The two atria are separated by the atrial septum, and the two ventricles by the interventricular septum. The atrium and ventricle of each side of the heart are connected by the atrioventricular orifice. This opening opens and closes the atrioventricular valve. The left atrioventricular valve is also known as mitral valve, and the right atrioventricular valve as a tricuspid valve.

The function of the heart is the rhythmic pumping of blood from the veins into the arteries, that is, the creation of a pressure gradient, due to which its constant movement occurs. This means that the main function of the heart is to provide blood circulation by communicating blood with kinetic energy. The heart is therefore often associated with a pump. It features exceptional performance, speed and smoothness. transients, margin of safety and constant renewal of fabrics.

Vessels are a system of hollow elastic tubes different structure, diameter and mechanical properties filled with blood.

IN general case Depending on the direction of blood flow, the vessels are divided into: arteries, through which blood is removed from the heart and enters the organs, and veins - vessels in which blood flows towards the heart and capillaries.

Unlike arteries, veins have thinner walls that contain less muscle and elastic tissue.

Man and all vertebrate animals have a closed circulatory system. The blood vessels of the cardiovascular system form two main subsystems: the vessels of the pulmonary circulation and the vessels of the systemic circulation.

The pulmonary circulation vessels carry blood from the heart to the lungs and vice versa. The pulmonary circulation begins with the right ventricle, from which the pulmonary trunk emerges, and ends with the left atrium, into which the pulmonary veins flow.

The vessels of the systemic circulation connect the heart to all other parts of the body. The systemic circulation begins in the left ventricle, from where the aorta exits, and ends in the right atrium, where the vena cava flows.

Capillaries are the smallest blood vessels that connect arterioles to venules. Thanks very much thin wall capillaries in them there is an exchange of nutrients and other substances (such as oxygen and carbon dioxide) between the blood and cells of various tissues. Depending on the need for oxygen and other nutrients different tissues have different numbers of capillaries.

Age features of the cardiovascular system.

How less baby, topics:

smaller sizes and volumes various departments cardiovascular systems;

the more often the frequency of contractions; So

• 1 day - 150 beats per minute.
• 1 year - 130 beats per minute.
• 3 years - 110 beats per minute.
• 7 years - 85-90 beats per minute.
• 12 years - 90 beats per minute.
• 18 years - 80 beats per minute.

Adult -66-72 beats per minute.

the less the functional capabilities of the body, which increase with age and fitness;

the less economically and efficiently the cardiovascular system works;

the less additional are the reserve and functional capabilities of the cardiovascular system.

Hygiene of the cardiovascular system

The hygiene of the cardiovascular system consists in observing the norms of the functioning of this system, i.e. in accordance with age characteristics, maintain at the level - heart rate norms, the level of minimum and maximum blood pressure, stroke volume (the number of ml. minute. For optimal functioning of the cardiovascular system, the following requirements must be observed:

adherence to the correct daily routine;

correct regulation of physical and mental stress. Based on this, the reduction of static loads and the increase of dynamic ones;

hardening, physical education and sports; warning bad habits; observance of the rules of mental hygiene.

Respiration is the process of constant exchange of gases between the body and environment. Through the respiratory organs, oxygen enters the body, carbon dioxide and water vapor are excreted from the body. Oxygen is needed by the body to carry out oxidative processes, which are the main sources of energy.

The external respiration of a newborn child is characterized by a frequent and not very stable rhythm, uniform distribution time between inhalation and exhalation, small tidal volume, low airflow velocity and short respiratory pauses.

The respiratory rate in newborns ranges from 40 to 70 per minute. During the first year of life, the child is in a state of physical shortness of breath.

With age, the frequency decreases respiratory movements, the breathing rhythm becomes more stable, the inspiratory phase becomes shorter in relation to the entire cycle, and the exhalation and respiratory pause are longer. Diaphragmatic breathing is observed in newborns and infants.

With the growth and development of the body, the total lung capacity and its components change.

With age, the tidal volume (TO) and minute respiratory volume (MOD) increase. Until the age of 8 years, ventilation of the lungs in girls and boys is approximately the same. At the age of 15-16 years, DO corresponds to the values ​​of adults. IN puberty MOD may even exceed its value in adults.

Phases of the cardiac cycle.

The following properties are characteristic of the myocardium: excitability, the ability to contract, conduction and automaticity. To understand the phases of contractions of the heart muscle, it is necessary to remember two basic terms: systole and diastole. Both terms are of Greek origin and are opposite in meaning, in translation systello means "to tighten", diastello - "to expand".

Atrial systole

Blood is sent to the atria. Both chambers of the heart are sequentially filled with blood, one part of the blood is retained, the other goes further into the ventricles through the open atrioventricular openings. It is at this moment that the atrial systole begins, the walls of both atria tense up, their tone begins to grow, the openings of the veins, carrying blood, are closed due to the annular myocardial bundles. The result of such changes is a contraction of the myocardium - atrial systole. At the same time, blood from the atria through the atrioventricular openings quickly tends to get into the ventricles, which does not become a problem, because. the walls of the left and right ventricles are relaxed in a given period of time, and the ventricular cavities expand. The phase lasts only 0.1 s, during which atrial systole is also superimposed on the last moments of ventricular diastole. It is worth noting that the atria do not need to use a more powerful muscle layer, their job is only to pump blood into neighboring chambers. It is precisely because of the lack of functional need muscle layer the left and right atria are thinner than the similar layer of the ventricles.

Ventricular systole

After atrial systole, the second phase begins - ventricular systole, it also begins with a period of tension of the heart muscle. The voltage period lasts an average of 0.08 s. Physiologists managed to divide even this meager time into two phases: within 0.05 s, the muscular wall of the ventricles is excited, its tone begins to increase, as if prompting, stimulating for future action - the phase of asynchronous contraction. The second phase of the period of myocardial stress is the phase of isometric contraction, it lasts 0.03 s, during which there is an increase in pressure in the chambers, reaching significant figures.

Here a natural question arises: why does the blood not rush back into the atrium? This is exactly what would have happened, but she cannot do this: the first thing that begins to be pushed into the atrium is the free edges of the atrioventricular valve cusps floating in the ventricles. It would seem that under such pressure they should have twisted into the atrial cavity. But this does not happen, since the tension increases not only in the myocardium of the ventricles, the fleshy crossbars and papillary muscles also tighten, pulling the tendon filaments, which protect the valve flaps from "falling out" into the atrium. Thus, by closing the leaflets of the atrioventricular valves, that is, by the slamming of the communication between the ventricles and the atria, the period of tension in the systole of the ventricles ends.

After the voltage reaches its maximum, the period of contraction of the ventricular myocardium begins, it lasts for 0.25 s, during this period the actual systole of the ventricles takes place. For 0.13 s, blood is ejected into the holes pulmonary trunk and aorta, the valves are pressed against the walls. This happens due to an increase in pressure up to 200 mm Hg. in the left ventricle and up to 60 mm Hg. in the right. This phase is called the rapid ejection phase. After it, in the remaining time, there is a slower release of blood under less pressure - the phase of slow expulsion. At this moment, the atria are relaxed and begin to receive blood from the veins again, thus, the ventricular systole overlaps with the atrial diastole.

Total diastolic pause (total diastole)

The muscular walls of the ventricles relax, entering into diastole, which lasts 0.47 s. During this period, ventricular diastole is superimposed on the still ongoing atrial diastole, so it is customary to combine these phases of the cardiac cycle, calling them the total diastole, or the total diastolic pause. But that doesn't mean everything has stopped. Imagine, the ventricle contracted, squeezing blood out of itself, and relaxed, creating inside its cavity, as it were, a rarefied space, almost negative pressure. In response, blood rushes back into the ventricles. But the semilunar cusps of the aortic and pulmonary valves, returning the same blood, move away from the walls. They close, blocking the gap. The period lasting 0.04 s, starting from the relaxation of the ventricles until the semilunar valves close the lumen, is called the proto-diastolic period (the Greek word proton means "first"). The blood has no choice but to start its journey along the vascular bed.

In the next 0.08 s after the protodiastolic period, the myocardium enters the phase of isometric relaxation. During this phase, the cusps of the mitral and tricuspid valves are still closed, and blood, therefore, does not enter the ventricles. But calmness ends when the pressure in the ventricles becomes lower than the pressure in the atria (0 or even slightly less in the first and from 2 to 6 mm Hg in the second), which inevitably leads to the opening of the atrioventricular valves. During this time, the blood has time to accumulate in the atria, the diastole of which began earlier. For 0.08 s, it safely migrates to the ventricles, the phase of rapid filling is carried out. Blood for another 0.17 s gradually continues to flow into the atria, a small amount of it enters the ventricles through the atrioventricular openings - the phase of slow filling. The last thing that the ventricles undergo during their diastole is an unexpected flow of blood from the atria during their systole, lasting 0.1 s and constituting the presystolic period of the ventricular diastole. Well, then the cycle closes and begins again.

The duration of the cardiac cycle

Summarize. The total time of the entire systolic work of the heart is 0.1 + 0.08 + 0.25 = 0.43 s, while the diastolic time for all chambers in total is 0.04 + 0.08 + 0.08 + 0.17 + 0.1 \u003d 0.47 s, that is, in fact, the heart "works" for half its life, and "rests" for the rest of its life. If you add the time of systole and diastole, it turns out that the duration of the cardiac cycle is 0.9 s. But there is some convention in the calculations. After all, 0.1 s. systolic time per atrial systole, and 0.1 s. diastolic, allotted for the presystolic period, in fact, the same thing. After all, the first two phases of the cardiac cycle are layered one on top of the other. Therefore, for general timing, one of these figures should simply be canceled. Drawing conclusions, it is possible to fairly accurately estimate the amount of time spent by the heart to complete all phases of the cardiac cycle, the duration of the cycle will be 0.8 s.

Heart sounds

Having considered the phases of the cardiac cycle, it is impossible not to mention the sounds made by the heart. On average, about 70 times per minute, the heart produces two really similar sounds like beats. Knock-knock, knock-knock.

The first "fat", the so-called I tone, is generated by ventricular systole. For simplicity, you can remember that this is the result of the slamming of the atrioventricular valves: mitral and tricuspid. At the moment of rapid myocardial tension, the valves close the atrioventricular orifices, their free edges close, and a characteristic “blow” is heard in order not to release blood back into the atria. To be more precise, the tensing myocardium, trembling tendon filaments, and the oscillating walls of the aorta and pulmonary trunk are involved in the formation of the first tone.

II tone - the result of diastole. It occurs when the semilunar cusps of the aortic and pulmonary valves block the path of blood, which decides to return to the relaxed ventricles, and "knock", connecting the edges in the lumen of the arteries. This, perhaps, is all.

However, there are changes in the sound picture when the heart is in trouble. With heart disease, sounds can become very diverse. Both tones known to us can change (become quieter or louder, bifurcate), appear additional tones(III and IV), various noises, squeaks, clicks, sounds called "swan cry", "whooping cough", etc.

Stages of development of the heart A, B from the ventral side. B from the dorsal side; 1 sip; 2 first aortic arch; 3 endocardial tubes; 4 pericardium and its cavity; 5 epimyocardium (laying myocardium and epicardium); 6 ventricular endocardium; 7 atrial tab; 8 atrium; 9, 11 truncus arteriosus; 10 ventricle; 12 right atrium; 13 left atrium; 14 superior vena cava; 15 inferior vena cava; 16 pulmonary veins; 17 arterial cone; 18 ventricle; 19, 21 right ventricle; 20 left ventricle

The change in blood circulation in the newborn increases CO 2 and decreases the amount of O 2. Such blood activates the respiratory center. the first breath occurs, during which the lungs expand and the vessels in them expand. if the newborn does not begin to breathe on his own immediately, he develops hypoxia, which provides additional stimulation respiratory center and inhalation occurs no later than the next minute after childbirth. delayed activation of spontaneous breathing after childbirth - the danger of hypoxia.

Foramen ovale is a small opening between the two atria, is an adaptive physiological mechanism: due to the inactivity of the lungs, a large supply of blood to them is not required. When open oval window there is a movement of blood around the small (pulmonary) circle of blood circulation.

The heart of a newborn, the heart occupies a transverse position and is pushed back by an enlarged thymus. in the first months of life, atrial growth occurs more intensively than ventricular growth; in the second year of life, their growth is the same. starting from the age of 10, the ventricles are ahead of the atria. from the end of the first year, the heart begins to take an oblique position

Change in heart rate in children Newborn months year year year year year year year year year year year year year year year year 70-76

Youthful heart Complaints: increased, irregular heartbeat, feeling of sinking in the chest, fatigue, poor tolerance physical activity, lack of air, tingling and discomfort in the region of the heart, deterioration in the ability to tolerate oxygen starvation. norm variant Functional disorders, usually pass by years

birth defects heart - an anatomical defect in the structure of the heart or main vessels which has been present since birth. Congenital heart disease of the pale type defect interatrial septum, defect interventricular septum, patent ductus arteriosus Congenital heart disease of the blue type with a venoarterial shunt: Fallot's tetrad, transposition of the great vessels, etc. Congenital heart disease without a shunt, but with obstruction of blood flow stenosis of the aorta and pulmonary artery

Pale-type congenital heart defects Patent ductus arteriosus The ductus arteriosus of a newborn does not close after birth. After birth, the lungs release bradykinin, which contracts the smooth muscles in the walls of the ductus arteriosus and reduces blood flow through it. ductus arteriosus usually narrows and completely grows within hours of life, but no more than 2-8 weeks

Transposition of the great vessels, blood from the right ventricle enters the aorta, and from the left - into pulmonary artery. Severe shortness of breath and cyanosis appear immediately after birth. Without surgical treatment life expectancy of patients usually does not exceed two years.