The stages of oxygen absorption by the body are summarized. Oxygen supply system for the body (child). Questions and tasks

Chapter 8. oxygen supply system of the body

Redox reactions continuously occurring in every cell of the body require a constant supply of oxidation substrates (carbohydrates, lipids and amino acids) and an oxidizing agent - oxygen. The body has impressive reserves of nutrients - carbohydrate and fat depots, as well as a huge supply of proteins in skeletal muscles, so even a relatively long (several days) fasting does not cause significant harm to a person. But there are practically no reserves of oxygen in the body, except for the small amount contained in the muscles in the form of oxymyoglobin, therefore, without its supply, a person can survive only 2-3 minutes, after which the so-called “clinical death” occurs. If the supply of oxygen to brain cells is not restored within 10-20 minutes, biochemical changes will occur in them that will disrupt their functional properties and lead to the rapid death of the entire organism. Other cells in the body may not be affected to the same extent, but nerve cells are extremely sensitive to lack of oxygen. That is why one of the central physiological systems of the body is functional system oxygen supply, and the state of this particular system is most often used to assess “health”.

The concept of the oxygen regime of the body. Enough oxygen passes through the body a long way(Fig. 18). Getting inside in the form of gas molecules, it already in the lungs takes part in a number of chemical reactions that ensure its further transportation to the cells of the body. There, entering the mitochondria, oxygen oxidizes various organic compounds, ultimately turning them into water and carbon dioxide. In this form, oxygen is removed from the body.

What makes oxygen from the atmosphere penetrate into the lungs, then into the blood, and from there into tissues and cells, where it enters into biochemical reactions? Obviously, there is a certain force that determines exactly this direction of movement of the molecules of this gas. This force is a concentration gradient. The oxygen content in atmospheric air is much greater than in the air of the intrapulmonary space (alveolar). The oxygen content in the alveoli - the pulmonary vesicles in which gas exchange between air and blood occurs - is much higher than in venous blood. Tissues contain much less oxygen than arterial blood, and mitochondria contain an insignificant amount of oxygen, since the molecules of this gas entering them immediately enter into a cycle of oxidative reactions and are converted into chemical compounds. This cascade of gradually decreasing concentrations, reflecting gradients of effort, as a result of which oxygen from the atmosphere penetrates into the cells of the body, is usually called the oxygen regime of the body (Fig. 19). More precisely, the oxygen regime is characterized by the quantitative parameters of the described cascade. The upper step of the cascade characterizes the oxygen content in the atmospheric air, which penetrates into the lungs during inhalation. The second step is the O2 content in the alveolar air. The third step is the O2 content in arterial blood that has just been enriched with oxygen. And finally, the fourth step is the oxygen tension in the venous blood, which gives the oxygen it contains to the tissues. These four steps form three “flights” that reflect the real processes of gas exchange in the body. The “flight” between the 1st and 2nd steps corresponds to pulmonary gas exchange, between the 2nd and 3rd steps - oxygen transport by blood, and between the 3rd and 4th steps - tissue gas exchange. The greater the height of the step, the greater the concentration difference, the higher the gradient at which oxygen is transported at this stage. With age, the height of the first “span” increases, that is, the gradient pulmonary gas exchange; the second “span”, i.e. the gradient of 02 transport by blood, while the height of the third “span”, reflecting the gradient of tissue gas exchange, decreases. An age-related decrease in the intensity of tissue oxidation is a direct consequence of a decrease in the intensity of energy metabolism with age.

Rice. 18. Oxygen transport in humans (direction shown by arrows)

Rice. 19. Cascade of oxygen tension in the inhaled air (I), in the alveoli (A), arteries (a) and veins (K) In a 5-year-old boy, a 15-year-old teenager and a 30-year-old adult

Thus, the absorption of oxygen by the body occurs in three stages, which are separated in space and time. The first stage - pumping air into the lungs and exchanging gases in the lungs - is also called external respiration. The second stage - transport of gases by blood - is carried out by the circulatory system. The third stage - the absorption of oxygen by the cells of the body - is called tissue, or internal respiration.

Exchange of gases in the lungs. The lungs are sealed bags connected to the trachea through large airways - the bronchi. Atmospheric air penetrates through the nasal and oral cavities into the larynx and further into the trachea, after which it is divided into two streams, one of which goes to the right lung, the other to the left (Fig. 20). The trachea and bronchi consist of connective tissue and a frame made of cartilage rings, which do not allow these tubes to bend and block the airways with various changes in body position. Upon entering the lungs, the bronchi divide into many branches, each of which divides again, forming the so-called “bronchial tree”. The thinnest branches of this “tree” are called bronchioles, and at their ends there are pulmonary vesicles, or alveoli (Fig. 21). The number of alveoli reaches 350 million, and their total area- 150 m2. It is this surface that represents the area for the exchange of gases between blood and air. The walls of the alveoli consist of a single layer of epithelial cells, to which the thinnest blood capillaries, also consisting of single-layer epithelium, come close. This design, due to diffusion, ensures relatively easy penetration of gases from the alveolar air into capillary blood(oxygen) and in the opposite direction ( carbon dioxide). This gas exchange occurs as a result of the creation of a gas concentration gradient (Fig. 22). The air in the alveoli contains a relatively large amount of oxygen (103 mm Hg) and a small amount of carbon dioxide (40 mm Hg). In capillaries, on the contrary, the concentration of carbon dioxide is increased (46 mm Hg), and oxygen is reduced (40 mm Hg), since these capillaries contain venous blood, collected after it has been in the tissues and given away they receive oxygen and receive carbon dioxide in return. Blood flows continuously through the capillaries, and the air in the alveoli is renewed with every breath. The blood flowing from the alveoli, enriched with oxygen (up to 100 mm Hg), contains relatively little carbon dioxide (40 mm Hg) and is again ready for tissue gas exchange.

Rice. 20. Scheme of the structure of the lungs (A) and pulmonary alveoli (B)

A: ] - larynx; 2 - trachea; 3 - bronchi; 4 - bronchioles; 5 - light;

B: 1 - vascular network; 2, 3 - alveoli from the outside and in section; 4 -

bronchiole; 5 - artery and vein

Rice. 21. Scheme of branching of the airways (left). The right side of the figure shows a curve of the total cross-sectional area of the airways at the level of each branch (3). At the beginning of the transition zone, this area begins to increase significantly, which continues in the respiratory zone. Br - bronchi; Bl - bronchioles; TBl - terminal bronchioles; DBL - respiratory bronchioles; AH - alveolar ducts; A - alveoli

Rice. 22. Exchange of gases in the pulmonary alveoli: through the wall of the pulmonary alveoli, O2 of inhaled air enters the blood, and CO2 of venous blood enters the alveoli; gas exchange is ensured by the difference in partial pressures (P) of CO2 and O2 in the venous blood and in the cavity of the pulmonary alveoli

To prevent the smallest bubbles - the alveoli - from collapsing during exhalation, their surface is covered from the inside with a layer of a special substance produced by the lung tissue. This substance - surfactant - reduces the surface tension of the walls of the alveoli. It is usually produced in excess to ensure maximum use of the lung surface area for gas exchange.

Diffusion capacity of the lungs. The gas concentration gradient on both sides of the alveolar wall is the force that causes oxygen and carbon dioxide molecules to diffuse and penetrate through this wall. However, at the same atmospheric pressure, the rate of diffusion of molecules depends not only on the gradient, but also on the contact area of the alveoli and capillaries, on the thickness of their walls, on the presence of surfactant and a number of other reasons. In order to evaluate all these factors, the diffusion capacity of the lungs is measured using special instruments, which, depending on age and functional state person can vary from 20 to 50 ml O2/min/mmHg. Art.

Ventilation-perfusion ratio. Gas exchange in the lungs occurs only if the air in the alveoli is periodically (in each respiratory cycle) renewed, and blood continuously flows through the pulmonary capillaries. It is for this reason that cessation of breathing, as well as cessation of blood circulation, equally means death. The continuous flow of blood through the capillaries is called perfusion, and the rhythmic flow of new portions of atmospheric air into the alveoli is called ventilation. It should be emphasized that the composition of the air in the alveoli is very different from that of the atmosphere: the alveolar air contains much more carbon dioxide and less oxygen. The fact is that mechanical ventilation of the lungs does not affect the deepest zones in which the pulmonary vesicles are located, and there gas exchange occurs only due to diffusion, and therefore somewhat slower. Nevertheless, each respiratory cycle brings new portions of oxygen into the lungs and removes excess carbon dioxide. The rate of perfusion of lung tissue with blood must exactly match the rate of ventilation so that an equilibrium is established between these two processes, otherwise either the blood will be oversaturated with carbon dioxide and undersaturated with oxygen, or, conversely, carbon dioxide will be washed out of the blood. Both are bad, since the respiratory center, located in medulla oblongata, generates impulses that force the respiratory muscles to inhale and exhale, under the influence of receptors that measure the content of CO2 and O2 in the blood. If CO2 levels in the blood drop, breathing may stop; if it grows, shortness of breath begins, the person feels suffocated. The relationship between the rate of blood flow through the pulmonary capillaries and the rate of air flow ventilating the lungs is called the ventilation-perfusion ratio (VPR). The ratio of O2 and CO2 concentrations in exhaled air depends on it. If the increase in CO2 (compared to atmospheric air) exactly corresponds to the decrease in oxygen content, then VPO = 1, and this increased level. Normally, the VPO is 0.7-0.8, i.e., perfusion should be somewhat more intense than ventilation. The value of HPE is taken into account when identifying certain diseases bronchopulmonary system and circulatory systems.

If you deliberately sharply intensify your breathing, taking the deepest and most frequent inhalations and exhalations, then the HPE will exceed 1, and the person will soon feel dizzy and may faint - this is the result of “washing out” excess amounts of CO2 from the blood and disrupting acid-base homeostasis. On the contrary, if you hold your breath through an effort of will, then the GPO will be less than 0.6 and after a few tens of seconds the person will feel suffocation and an imperative urge to breathe. At the beginning of muscular work, the VPO changes sharply, first decreasing (perfusion increases, since the muscles, having begun to contract, squeeze out additional portions of blood from their veins), and after 15-20 s rapidly increasing (the respiratory center is activated and ventilation increases). HPE is normalized only 2-3 minutes after the start of muscle work. At the end of muscular work, all these processes occur in reverse order. In children, such a reconfiguration of the oxygen supply system occurs a little faster than in adults, since the body size and, accordingly, the inertial characteristics of the heart, blood vessels, lungs, muscles and other structures involved in this reaction are significantly smaller in children.

Tissue gas exchange. Blood, which brings oxygen to the tissues, releases it (along a concentration gradient) into the tissue fluid, and from there O2 molecules penetrate into the cells, where they are captured by mitochondria. The more intense this capture occurs, the faster the oxygen content in the tissue fluid decreases, the higher the gradient between arterial blood and tissue becomes, the faster the blood releases oxygen, disconnecting from the hemoglobin molecule, which served as a “vehicle” for oxygen delivery. The released hemoglobin molecules can capture CO2 molecules to carry them to the lungs and release them there to the alveolar air. Oxygen, entering the cycle of oxidative reactions in mitochondria, ultimately ends up combined with either hydrogen (H2O is formed) or carbon (CO2 is formed). In free form, oxygen practically does not exist in the body. All carbon dioxide formed in the tissues is removed from the body through the lungs. Metabolic water also partially evaporates from the surface of the lungs, but can also be excreted through sweat and urine.

Respiratory coefficient. The ratio of the amounts of CO2 formed and O2 absorbed is called the respiratory coefficient (RC) and depends on which substrates are oxidized in the tissues of the body. DC in exhaled air ranges from 0.65 to 1. For purely chemical reasons during the oxidation of fats, DC = 0.65; during protein oxidation - about 0.85; during the oxidation of carbohydrates DC = 1.0. Thus, by the composition of exhaled air one can judge what substances are currently used to produce energy by the body’s cells. Naturally, usually DC takes some intermediate value, most often close to 0.85, but this does not mean that proteins are oxidized; rather, it is the result of the simultaneous oxidation of fats and carbohydrates. The value of the DC is closely related to the HPO; there is almost complete correspondence between them, except for periods when the HPO is subject to sharp fluctuations. In children at rest, DC is usually higher than in adults, which is associated with a significantly greater participation of carbohydrates in the energy supply of the body, especially in the activity of nervous structures.

During muscular work, the DC can also significantly exceed the HPO if the processes of anaerobic glycolysis are involved in the energy supply. In this case, homeostatic mechanisms (blood buffer systems) lead to the release of an additional amount of CO2 from the body, which is not due to metabolic needs, but to homeostatic ones. This additional release of CO2 is called “non-metabolic excess.” Its appearance in the exhaled air means that the level of muscle load has reached a certain threshold, after which it is necessary to connect anaerobic energy production systems (“anaerobic threshold”). Children from 7 to 12 years old have higher relative indicators of the anaerobic threshold: with such a load, they have a higher heart rate, pulmonary ventilation, blood flow speed, oxygen consumption, etc. By the age of 12, the load corresponding to the anaerobic threshold decreases sharply, and after 17-18 years old does not differ from the corresponding load in adults. The anaerobic threshold is one of the most important indicators of human aerobic performance, as well as the minimum load that can ensure the achievement of a training effect.

External respiration is a manifestation of the breathing process that is clearly visible without any instruments, since air enters and leaves the airways only due to changes in shape and volume chest. What makes air penetrate deep into the body, ultimately reaching the smallest pulmonary bubbles? IN in this case There is a force caused by the difference in pressure inside the chest and in the surrounding atmosphere. The lungs are surrounded by a connective tissue membrane called the pleura, and between the lungs and the pleural sac there is pleural fluid, which serves as a lubricant and sealant. The intrapleural space is sealed and does not communicate with neighboring cavities and digestive and blood pipes passing through the chest. The entire chest, separated from abdominal cavity not only by the serous membrane, but also by a large circular muscle - the diaphragm. Therefore, the efforts of the respiratory muscles, leading to even a slight increase in its volume during inhalation, provide a fairly significant vacuum inside the pleural cavity, and it is under the influence of this vacuum that air enters the oral and nasal cavities and penetrates further through the larynx, trachea, bronchi and bronchioles into the pulmonary textile.

Organization of the respiratory act. Three muscle groups are involved in organizing the respiratory act, i.e., in moving the walls of the chest and abdominal cavity: inspiratory (providing inhalation) external intercostal muscles; expiratory (providing exhalation) internal intercostal muscles and the diaphragm, as well as the muscles of the abdominal wall. The coordinated contraction of these muscles under the control of the respiratory center, which is located in the medulla oblongata, causes the ribs to move slightly forward and upward relative to their position at the time of exhalation, the sternum rises, and the diaphragm is pressed into the abdominal cavity. Thus, the total volume of the chest increases significantly, a fairly high vacuum is created there, and air from the atmosphere rushes into the lungs. At the end of inhalation, the impulse from the respiratory center to these muscles stops, and the ribs, under the force of their own gravity, and the diaphragm, as a result of its relaxation, return to the “neutral” position. The volume of the chest decreases, the pressure there increases, and excess air from the lungs is expelled through the same tubes through which it entered. If for some reason exhalation is difficult, then the expiratory muscles are activated to facilitate this process. They also work in cases where breathing intensifies or accelerates under the influence of emotional or physical stress. The work of the respiratory muscles, like any other muscular work, requires energy expenditure. It is estimated that during quiet breathing, a little more than 1% of the energy consumed by the body is spent on these needs.

Depending on whether the expansion of the chest during normal breathing is associated primarily with raising the ribs or flattening the diaphragm, costal (thoracic) and diaphragmatic (abdominal) types of breathing are distinguished. At breast type breathing, the diaphragm moves passively in accordance with changes in intrathoracic pressure. With the abdominal type, powerful contractions of the diaphragm greatly displace the organs of the abdominal cavity, so when inhaling, the stomach “sticks out.” The formation of the type of breathing occurs at the age of 5-7 years, and in girls it usually becomes thoracic, and in boys - abdominal.

Pulmonary ventilation. The larger the body and the stronger the respiratory muscles work, the more air passes through the lungs during each respiratory cycle. To assess pulmonary ventilation, the minute volume of breathing is measured, i.e. average amount of air that passes through Airways in 1 min. At rest in an adult, this value is 5-6 l/min. In a newborn child, the minute breathing volume is 650-700 ml/min, by the end of 1 year of life it reaches 2.6-2.7 l/min, by 6 years - 3.5 l/min, at 10 years - 4.3 l /min, and in adolescents - 4.9 l/min. During physical activity, the minute volume of breathing can increase very significantly, reaching 100 l/min or more in young men and adults.

Frequency and depth of breathing. The respiratory act, consisting of inhalation and exhalation, has two main characteristics - frequency and depth. Frequency is the number of respiratory acts per minute. In an adult, this value is usually 12-15, although it can vary widely. In newborns, the respiratory rate during sleep reaches 50-60 per minute, by the age of one year it decreases to 40-50, then as they grow, this indicator gradually decreases. So, in younger children school age The respiratory rate is usually about 25 cycles per minute, and in adolescents it is 18-20. The exact opposite trend age-related changes demonstrates tidal volume, i.e. a measure of the depth of breathing. It represents the average amount of air that enters the lungs during each breathing cycle. In newborns it is very small - only 30 ml or even less, by the age of one it increases to 70 ml, at 6 years it becomes over 150 ml, by 10 years it reaches 240 ml, at 14 years - 300 ml. In an adult, the tidal volume at rest does not exceed 500 ml. Minute respiratory volume is the product of tidal volume and respiratory rate.

If a person performs any physical activity, he requires additional oxygen, and the minute volume of respiration increases accordingly. In children under 10 years of age, this increase is ensured mainly by increased breathing, which can become 3-4 times more frequent than breathing at rest, while tidal volume increases only 1.5-2 times. In adolescents, and even more so in adults, the increase in minute volume is carried out mainly due to tidal volume, which can increase several times, and the respiratory rate usually does not exceed 50-60 cycles per minute. It is believed that this type of respiratory system response is more economical. According to various criteria, the effectiveness and efficiency of external respiration increases significantly with age, reaching maximum values in boys and girls aged 18-20 years. At the same time, the breathing of boys, as a rule, is organized more efficiently than that of girls. The efficiency of breathing and its economy are greatly influenced by physical training, especially in those sports in which oxygen supply plays a decisive role. This includes distance running, skiing, swimming, rowing, cycling, tennis and other types of endurance sports.

When performing a cyclic load, the breathing rhythm usually “adjusts” to the rhythm of skeletal muscle contraction - this makes breathing easier and more efficient. In children, the assimilation of the rhythm of movements of the respiratory muscles occurs instinctively without the intervention of consciousness, however, the teacher can help the child, which contributes to the fastest adaptation to this kind of load.

When performing power and static loads, the so-called Lindhardt phenomenon is observed - holding the breath during straining with a subsequent increase in the frequency and depth of breathing after removing the load. It is not recommended to use heavy power and static loads in training and physical education of children under 13-14 years of age, including due to the immaturity of the respiratory system.

Spirogram. If rubber bellows or a light bell immersed in water is placed in the path of air entering and leaving the lungs, then, thanks to the action of the respiratory muscles, this device will increase its volume when exhaling and decrease when inhaling. If all connections are sealed (a special rubber mouthpiece or a mask worn on the face is used to seal the oral cavity), then you can attach a writing instrument to the moving part of the device and write down everything breathing movements. Such a device, invented back in the 19th century, is called a spirograph, and the recording made with its help is a spirogram (Fig. 23). Using a spirogram made on a paper tape, you can quantitatively measure the most important characteristics human external respiration. Lung volumes and capacities. Thanks to the spirogram, you can clearly see and measure various lung volumes and capacities. In respiratory physiology, volumes are usually called those indicators that dynamically change during the breathing process and characterize the functional state of the respiratory system. A container is a reservoir that cannot be changed in a short time, within which the respiratory cycle and gas exchange occur. The reference point for all pulmonary volumes and capacities is the level of quiet expiration.

Lung volumes. At rest, tidal volume is small compared to the total volume of air in the lungs. Therefore, a person can both inhale and exhale a large additional volume of air. These volumes are called inspiratory reserve volume and expiratory reserve volume, respectively. However, even with the deepest exhalation in the alveoli and airways some air remains. This is the so-called residual volume, which is not measured using a spirogram (to measure it, rather complex equipment and calculations are used, inert gases are used). In an adult it is about 1.5 liters, in children it is significantly less.

Rice. 23. Spirogram: lung capacity and its components

A - spirogram diagram: 1 - inspiratory reserve volume; 2 - tidal volume; 3 - reserve expiratory volume; 4 - residual volume; 5 - functional residual capacity; 6 - inhalation capacity; 7 - vital capacity; 8 - total lung capacity; B - volumes and capacities of the lungs: / - young athletes; // - untrained schoolchildren ( average age 13 years old) (according to A.I. Osipov, 1964). The numbers above the bars are the average values of the total capacity. The numbers in the columns are the average values of lung volumes as a percentage of the total capacity; the numbers to the left of the bars correspond to the designations on the spirogram

Vital capacity of the lungs. The total value of inspiratory reserve volume, tidal volume and expiratory reserve volume is vital capacity lungs (VC) is one of the most important indicators of the state of the respiratory system. To measure it, spirometers of various designs are used, into which you need to exhale as deeply as possible after inhaling as deeply as possible - this will be vital vital capacity. Vital capacity depends on body size, and therefore on age, and also very significantly depends on the functional state and physical fitness of the human body. Men have a higher vital capacity than women if neither of them engages in sports, especially endurance exercises. The value of vital capacity varies significantly among people of different physiques: in brachymorphic types it is relatively small, and in dolichomorphic types it is very large. It is customary to use vital capacity as one of the indicators of the physical development of school-age children, as well as conscripts. Vital vital capacity can only be measured with the active and conscious participation of the child, so there is practically no data on children under 3 years of age.

Table 9

Vital capacity of the lungs in children and adolescents (in ml)

	Age, years

Boys

Despite its name, vital capacity does not reflect breathing parameters in real, “life” conditions, since under no load a person breathes, using the full reserve volume of inhalation and reserve volume of exhalation.

Other containers. The space in the lungs that can be occupied by air in the event of a fullest inhalation after a quiet exhalation is called the inspiratory capacity. This capacity consists of the tidal volume and the inspiratory reserve volume.

The expiratory reserve volume and the residual volume that can never be exhaled together constitute the functional residual capacity (FRC) of the lungs. The physiological meaning of the FRC is that it plays the role of a buffer zone. Thanks to its presence in the alveolar space, fluctuations in O2 and CO2 concentrations during respiration are smoothed out. This stabilizes the function of pulmonary gas exchange, ensuring a uniform flow of oxygen from the alveolar space into the bloodstream, and carbon dioxide in the opposite direction.

Total lung capacity is the sum of vital capacity and residual volume, or all four lung volumes: tidal, residual, inspiratory and expiratory reserve volumes. Total lung capacity increases with age in proportion to body size.

Breath control. Breathing is one of those functions of the body that, on the one hand, are carried out automatically, but on the other hand, can be subject to consciousness. Automatic breathing is provided by the respiratory center located in the medulla oblongata. Destruction of the respiratory center leads to respiratory arrest. Rhythmically arising in the respiratory center, excitation impulses are transmitted through centrifugal neurons to the respiratory muscles, ensuring the alternation of inhalation and exhalation. It is believed that the occurrence of periodic impulses in the respiratory center is due to cyclic metabolic processes in the neurons that make up this area of the brain. The activity of the respiratory center is regulated by a large number of innate and acquired reflexes, as well as impulses from chemoreceptors that control oxygen tension, carbon dioxide and pH levels in the blood, and mechanoreceptors that monitor the degree of stretching of the respiratory muscles, lung tissue and many other parameters. Reflex arcs are designed in such a way that the completion of inhalation stimulates the beginning of exhalation, and the end of exhalation is a reflex stimulus for the beginning of inhalation.

At the same time, all these reflexes can be suppressed for some time due to the activity of the cerebral cortex, which can take over control of breathing. This type of breathing is called voluntary. In particular, it is used when performing breathing exercises, when diving, when exposed to gas or smoke conditions, and in other cases when adaptation to rare factors is required. However, with voluntary breath-holding, sooner or later the respiratory center takes over control of this function and issues an imperative stimulus that consciousness cannot cope with. This happens when the sensitivity threshold of the respiratory center is reached. The more mature and more physically trained the body, the higher this threshold, the greater the deviations in homeostasis the respiratory center can withstand. Specially trained divers, for example, are able to hold their breath for 3-4 minutes, sometimes even for 5 minutes - the time they need to descend to a significant depth under water and search for the desired object there. For example, sea pearls, corals, sponges and some other “seafood” are mined. In children, conscious control of the respiratory center is possible after completing the half-growth leap, i.e. after 6-7 years, usually at this age, children learn to dive and swim in styles that involve holding their breath (crawl, dolphin).

The moment a person is born is the moment of his first breath. Indeed, in the womb, the function of external respiration could not be carried out, and the need for oxygen was provided by its supply through the placenta from the mother’s body. Therefore, although by the time of birth the functional respiratory system normally fully matures, it has a number of features associated with the act of birth and living conditions during the newborn period. In particular, the activity of the respiratory center in children during this period is relatively low and unsteady, so the child often takes his first breath not immediately after leaving the birth canal, but after a few seconds or even minutes. Sometimes a simple slap on the child’s buttocks is enough to initiate the first breath, but sometimes apnea (lack of breathing) drags on, and if it lasts several minutes, it can turn into a state of asphyxia. Being a fairly typical complication of the birth process, asphyxia is extremely dangerous due to its consequences: oxygen starvation of nerve cells can lead to disruption of their normal functioning. This is why the nervous tissue of newborns is much less sensitive to a lack of oxygen and an excess of acidic metabolic products. Nevertheless, prolonged asphyxia (tens of minutes) leads to significant disturbances in the activity of the central nervous system, which can sometimes affect the rest of life.

By the age of 2-3 years, the sensitivity of the respiratory center in children increases sharply and becomes higher than in adults. In the future, it gradually decreases, up to 10-11 years. In adolescence, there is again a temporary increase in the sensitivity of the respiratory center, which is eliminated with the completion of pubertal processes.

Age-related changes in the structure and functionality of the respiratory organs. With age, all anatomical components of the respiratory system increase in size, which largely determines the direction of functional age-related changes. The absolute characteristics of the anatomical lumens of the trachea and bronchi, bronchioles, alveoli, total lung capacity and its components increase approximately in proportion to the increase in body surface area. At the same time, the higher intensity of metabolic, including oxidative, processes at an early age requires an increased supply of oxygen, therefore the relative indicators of the respiratory system reflect a significantly greater oxygen tension in children early age- until about 10-11 years old. However, despite the clearly lower efficiency and effectiveness, respiratory system It works just as reliably in children as in adults. This is favored, in particular, by the large diffusion capacity of the lungs, i.e. better permeability of alveoli and capillaries for oxygen and carbon dioxide molecules.

Transport of gases by blood

Oxygen entering the body through the lungs must be delivered to its consumers - all the cells of the body, sometimes located at a distance of tens of centimeters (and in some large animals - several meters) from the “source”. Diffusion processes are not capable of transporting substances over such distances at a speed sufficient for the needs of cellular metabolism. The most rational way to transport liquids and gases is to use pipelines. In their economic activities, people have long and widely used pipelines wherever the constant movement of significant quantities of water, oil, natural gas and many other substances is required. In order to resist the force of gravity, as well as overcome the force of friction in the pipes through which liquid flows, man invented a pump. And so that the liquid flows only in the right direction, without returning back when the pressure in the pipeline decreases, valves were invented - devices similar to doors that open only in one direction.

The main transport system of the human body, the circulatory system, is structured in exactly the same way. It consists of pipes-vessels, a pump-heart and numerous valves that ensure the unidirectional flow of blood through the heart and prevent the reverse flow of blood in the veins. Branching into tiny tubes - capillaries, blood vessels reach almost every cell, supplying them with nutrients and oxygen and taking away their waste products that other cells need or that the body needs to get rid of. The circulatory system in mammals and humans is a closed network of vessels through which a single blood flow passes, provided by the cyclic contraction of the heart muscle. Since the task of oxygen supply to cells is the first in a number of vital tasks, the circulatory system of higher animals and humans is specially adapted to the most efficient gas exchange in the air. This is ensured by dividing the closed vascular pipeline into two isolated circles - small and large, the first of which ensures gas exchange between the blood and the environment, and the second - between the blood and the cells of the body.

Small and big circle and blood circulation (Fig. 24). Arteries are those vessels that carry blood from the heart to organs and tissues. They have a strong and fairly thick wall, which must withstand the high pressures created by the work of the heart. Gradually branching into smaller and smaller vessels - arterioles and capillaries - arteries bring blood to all tissues. The vessels that carry blood from tissues are called veins. They are formed as smaller vessels - capillaries and venules - merge and enlarge. Veins are not very strong in their walls and collapse easily if there is no blood in them, since they do not have to deal with high blood pressure. To prevent blood from flowing in the opposite direction, the veins have special valves that hold back the blood if something causes it to flow in the opposite direction. Thanks to this design, the veins flowing through the skeletal muscles work as additional pumps: by contracting, the muscles push blood out of the veins, and by relaxing, they allow a new portion of blood to enter the veins. Since the movement of blood in them can only be in one direction - towards the heart - such a “muscle pump” makes a significant contribution to blood circulation during muscle activity.

The pulmonary circulation begins from the right ventricle, from which the pulmonary artery emerges. Almost immediately it divides into two streams - to the right and left lung. Having reached the lungs, the pulmonary arteries are divided into many capillaries, the thinnest of which wash the individual pulmonary vesicles (alveoli). This is where the exchange of gases occurs between the blood and the air in the alveoli. To facilitate gas exchange, the pulmonary capillaries consist of only one layer of cells.

Rice. 24. Blood circulation diagram

Unlike all other arteries in the body, the pulmonary arteries carry oxygen-poor and carbon dioxide-rich blood. This blood is called "venous" because it flows in veins throughout the body (except the pulmonary veins). This blood has already passed through the vessels of the systemic circulation, given up the oxygen it contained and collected carbon dioxide, which needs to be disposed of in the lungs.

The veins leaving the lungs, on the contrary, carry “arterial” blood, that is, blood saturated with oxygen and practically free of carbon dioxide. Thus, the pulmonary circulation is fundamentally different from the systemic circulation in the direction of movement of oxygenated blood.

The pulmonary veins carry oxygenated blood to the left atrium. Once filled with blood, the atrium contracts, pushing this portion of blood into the left ventricle. This is where the large circle of blood circulation begins.

The largest blood vessel in the body, the aorta, emerges from the left ventricle. This is a rather short but very powerful tube that can withstand very large pressure differences that occur during periodic contractions of the heart. Even in the chest, the aorta divides into several large arteries, some of which carry oxygen-rich arterial blood to the head and organs of the upper body, and others to the organs of the lower body. More and more new ones are successively separated from the large main vessels. small vessels, carrying blood to specific parts of the body. Thus, both to the brain and to others the most important bodies Fresh, oxygenated blood is always supplied.

The only exception to this rule is the liver, where arterial and venous blood mix. However, this has a deep physiological meaning. On the one hand, the liver receives fresh arterial blood through the hepatic artery, i.e. its cells are fully provided with the necessary amount of oxygen. On the other hand, the liver enters the so-called portal vein, which carries with it nutrients absorbed in the intestines. All blood flowing from the intestines passes through the liver - the main organ of protection against various kinds of toxins and dangerous substances that could be absorbed in the digestive tract. The liver's powerful oxidative systems “burn” all suspicious molecules, turning them into harmless metabolic products.

From all organs, blood collects in veins, which, merging, form increasingly larger combined vessels. The inferior vena cava, which collects blood from the lower part of the body, and the superior vena cava, which drains blood from the upper part of the body, drain into the right atrium, and from there they are pushed into the right ventricle. From this moment, the blood again enters the pulmonary circulation.

Lymphatic system. The second transport system of the body is the network lymphatic vessels. Lymph practically does not participate in oxygen transport, but has great importance for the distribution of nutrients (especially lipids) throughout the body, as well as to protect the body from the penetration of foreign bodies and dangerous microorganisms. Lymphatic vessels are similar in structure to veins; they also have valves inside them that provide unidirectional fluid flow, but, in addition, the walls of lymphatic vessels are capable of independent contraction (“lymphatic hearts”). Without a central pump, lymphatic system ensures the movement of fluid through these lymphatic hearts and the contraction of skeletal muscles. Along the path of the lymphatic vessels, especially at their confluence, lymph nodes are formed, which perform mainly protective (immune) functions. Negative pressure created in chest cavity when inhaled, also acts as a force to push the lymph towards the chest, where the lymph ducts empty into the veins. Thus, the lymphatic system is combined with the circulatory system into a single transport network of the body.

The heart and its age-related features. The main pump of the circulatory system - the heart - is a muscular bag divided into 4 chambers: two atria and two ventricles (Fig. 25). The left atrium is connected to the left ventricle by an opening in the cusp of which the mitral valve is located. The right atrium is connected to the right ventricle by an opening that closes the tricuspid valve. The right and left halves of the heart are not connected to each other, therefore the “venous” half of the heart is always located in the right half of the heart, i.e. oxygen-poor blood, and in the left - “arterial”, saturated with oxygen. The exit from the right (pulmonary artery) and left (aorta) ventricles is closed with similar designs semilunar valves. They prevent blood from these large outgoing vessels from returning to the heart during the period of its relaxation.

Formation of cardio-vascular system in the fetus it begins very early - already in the 3rd week after conception, a group of cells with periodic contractile activity appears, from which the heart muscle is subsequently formed. However, even at the time of birth, some features of the embryonic blood circulation are preserved (Fig. 26). Since the source of oxygen and nutrients in the embryonic period is not the lungs and digestive tract, but the placenta, connected to the fetus through the umbilical cord, a strict division of the heart into two independent halves is not required. In addition, the pulmonary blood flow does not yet have a functional meaning, and this section should not be included in the main circulation. Therefore, the fetus has an oval foramen that connects both atria, as well as a special ductus arteriosus that connects the aorta and pulmonary artery. Soon after birth, these shunt ducts close and the two circuits begin to function as in adults.

Rice. 25. Structure of the heart

Oval hole

Rice. 26. A - heart of the fetus; B - baby’s heart after birth. Arrows show the direction of blood flow

Although the bulk of the walls of the heart is the muscle layer (myocardium), there are several additional layers of tissue that protect the heart from external influences and strengthen its walls, which experience enormous pressure during operation. These protective layers are called the pericardium. The inner surface of the heart cavity is lined with endocardium, the properties of which make it possible not to harm blood cells during contractions. The heart is located on the left side of the chest (although in some cases there is a different location) with the “top” down.

The weight of the heart in an adult is 0.5% of body weight, i.e. 250-300 g in men and about 200 g in women. In children, the relative size of the heart is slightly larger - approximately 0.7% of body weight. The heart as a whole increases in proportion to the increase in body size. For the first 8 months. after birth, the weight of the heart doubles, by 3 years - three times, by 5 years - 4 times, and by 16 years - 11 times compared to the weight of the heart of a newborn. Boys usually have slightly larger hearts than girls; only during puberty began to mature girls before have a larger heart.

The atrial myocardium is much thinner than the ventricular myocardium. This is understandable: the work of the atria is to pump a portion of blood through the valves into the adjacent ventricle, while the ventricles need to give the blood such an acceleration that will force it to reach the most distant parts of the capillary network from the heart. For the same reason, the myocardium of the left ventricle is 2.5 times thicker than the myocardium of the right ventricle: pushing blood through the pulmonary circulation requires much less effort than through the systemic circulation.

The heart muscle consists of fibers similar to those of skeletal muscles. However, along with structures that have contractile activity, the heart also contains another - conductive - structure, which ensures rapid conduction of excitation to all parts of the myocardium and its synchronous periodic contraction. Each part of the heart is, in principle, capable of independent (spontaneous) periodic contractile activity, but normally, cardiac contraction is controlled by a certain part of the cells, which is called the pacemaker, or pacemaker, and is located in the upper part of the right atrium (sinus node). The impulse automatically generated here with a frequency of approximately 1 time per second (in adults; in children - much more often) spreads through the conduction system of the heart, which includes the atrioventricular node, the Hiss bundle, which breaks up into the right and left legs, branching in the mass of the ventricular myocardium ( Fig. 27). Most cardiac arrhythmias are the result of some kind of damage to the fibers of the conduction system. Myocardial infarction (death of part of the muscle fibers) is most dangerous in cases where both branches of the Hiss bundle are affected at once.

Rice. 27. Schematic representation of a conductive

heart system 1 - sinus node; 2 - atrioventricular node; 3 - Hiss bundle; 4 and 5 - right and left legs of the Hiss bundle; 6 - terminal branches of the conductive system

Cardiac cycle. The excitation that automatically occurs in the sinus node is transmitted to the contractile fibers of the atria, and the atrium muscles contract. This stage cardiac cycle called atrial systole. It lasts approximately 0.1 s. During this time, a portion of the blood accumulated in the atria moves into the ventricles. Immediately after this, ventricular systole occurs, which lasts 0.3 s. During the contraction of the muscles of the ventricles, blood is pushed out of them under high pressure, heading into the aorta and pulmonary arteries. Then comes a period of relaxation (diastole), which lasts 0.4 s. At this time, the blood entering the veins enters the cavity of the relaxed atria.

Quite significant mechanical work of the heart is accompanied by mechanical and acoustic effects. So, if you place the palm of your hand on the left side of your chest, you can feel the periodic beats that the heart makes with each contraction. The pulse (regular wave-like oscillations of the walls of large vessels with a frequency equal to the heart rate) can also be felt on the carotid artery, on the radial artery of the arm and at other points. If you place your ear or a special listening tube (stethoscope) to your chest or back, you can hear the heart sounds that occur at successive stages of its contraction and have their own characteristic features. Heart sounds in children are not the same as in adults, which is well known to pediatricians. Listening to the heart and feeling the pulse are the oldest diagnostic techniques, with the help of which doctors, back in the Middle Ages, determined the patient’s condition and, depending on the observed symptoms, prescribed treatment. In Tibetan medicine, long-term (tens of minutes) continuous monitoring of the pulse still serves as the main diagnostic technique. In modern medicine, the methods of echocardiography (recording of ultrasonic waves reflected from the tissues of the beating heart), phonocardiography (recording of sound waves generated by the heart during contractions), as well as spectral analysis of the heart rhythm (a special method of mathematical processing of a cardiogram) are widely used. The study of heart rate variability in children is used, in particular, to assess their adaptive capabilities during educational and physical activity.

Rice. 28. Normal ECG human, obtained by bipolar abduction from the surface of the body in the direction of the long axis of the heart

Electrocardiogram (Fig. 28). Since the heart is a muscle, its work leads to the appearance of biological electrical potentials that always accompany the contraction of muscles of any type. When strong enough, these contractions cause powerful streams of electrical impulses that spread throughout the body. The current voltage during such contractions is about 1 thousandth of a volt, i.e. a value quite sufficient for recording using a special potentiometer. Device intended for registration electrical activity heart is called an electrocardiograph, and the curve recorded by it is called an electrocardiogram (ECG). It is possible to remove the potential for recording an ECG using current-conducting electrodes (metal plates) from different parts of the body. Most often used in medical practice ECG leads from two arms or from one arm and one leg (symmetrically or asymmetrically), as well as a number of leads from the surface of the chest. Regardless of the lead location, the ECG always has the same waves, alternating in the same sequence. The locations of the ECG leads only affect the height (amplitude) of these waves.

ECG waves are usually designated by the Latin letters P, Q, R, S and T. Each of the waves carries information about electrical, and therefore metabolic processes in various areas myocardium, at different stages of the cardiac cycle. In particular, the P wave reflects atrial systole, the QRS complex characterizes ventricular systole, and the T wave indicates the occurrence of recovery processes in the myocardium during diastole.

Registration of an ECG is possible even in fetuses, since the electrical impulse of the fetus’s heart easily spreads through the conductive tissues of its and the mother’s body. There are no fundamental differences in the ECG of children: the same waves, the same sequence, the same physiological meaning. The differences lie in the amplitude characteristics of the waves and some relationships between the phases of the heart and reflect mainly an age-related increase in the size of the heart and an increase with age in the role of the parasympathetic division of the autonomic nervous system in controlling the contractile activity of the myocardium.

Blood flow speed. With each contraction, the ventricles expel all the blood in them. This volume of fluid that is pushed out by the heart during systole is called stroke output, or stroke (systolic) volume. This indicator increases with age in proportion to the increase in heart size. One-year-old children have a heart that pumps out a little more than 10 ml of blood per contraction; in children from 5 to 16 years old, this value increases from 25 to 62 ml. The product of stroke output and pulse rate shows the amount of blood passing through the heart in 1 minute and is called minute blood volume (MBV). In one-year-old children, the IOC is 1.2 l/min, by school age it increases to 2.6 l/min, and in young men and adults it reaches 4 l/min or more.

Under various loads, when the need for oxygen and nutrients increases, the IOC can increase quite significantly, and in children younger age mainly due to an increase in heart rate, and in adolescents and adults also due to an increase in shock output, which can double during exercise. In trained people, the heart is usually large, often has an inadequately enlarged left ventricle (the so-called “athletic heart”), and the stroke output in such athletes can even at rest be 2.5-3 times higher than that of an untrained person. The value of IOC in athletes is also 2.5-3 times higher, especially under loads that require maximum tension of the oxidative systems in the muscles and, accordingly, the transport systems of the body. At the same time, in trained people, physical activity causes a smaller increase in heart rate than in untrained people. This circumstance is used to assess the level of fitness and “physical performance at a pulse of 170 beats/min.”

The volumetric velocity of blood flow (i.e., the amount of blood passing through the heart per minute) may have little connection with the linear speed of movement of blood and its constituent cells through the vessels. The fact is that the linear speed depends not only on the volume of the transferred liquid, but also on the lumen of the pipe through which this liquid flows (Fig. 29). The further from the heart, the total lumen of the vessels of arteries, arterioles and capillaries becomes larger, since with each subsequent branching the total diameter of the vessels increases. Therefore, the highest linear speed of blood movement is observed in the thickest blood vessel - the aorta. Here blood flows at a speed of 0.5 m/s. Reaching the capillaries, the total lumen of which is approximately 1000 times larger than the cross-sectional area of the aorta, blood flows at a meager speed - only 0.5 mm/s. This slow flow of blood through capillaries located deep in the tissues provides sufficient time for the full exchange of gases and other substances between the blood and surrounding tissues. The speed of blood flow, as a rule, is adequate to the intensity of metabolic processes. This is ensured by homeostatic mechanisms for regulating blood flow. So, in case of excess supply of acid tissues

Redox reactions continuously occurring in every cell of the body require a constant supply of oxidation substrates (carbohydrates, lipids and amino acids) and an oxidizing agent - oxygen. The body has impressive reserves of nutrients - carbohydrate and fat depots, as well as a huge supply of proteins in skeletal muscles, so even a relatively long (several days) fasting does not cause significant harm to a person. But there are practically no reserves of oxygen in the body, except for the small amount contained in the muscles in the form of oxymyoglobin, therefore, without its supply, a person can survive only 2-3 minutes, after which the so-called “clinical death” occurs. If the supply of oxygen to brain cells is not restored within 10-20 minutes, biochemical changes will occur in them that will disrupt their functional properties and lead to the rapid death of the entire organism. Other cells in the body may not be affected to the same extent, but nerve cells are extremely sensitive to lack of oxygen. That is why one of the central physiological systems of the body is the functional oxygen supply system, and the state of this particular system is most often used to assess “health”.

The concept of the oxygen regime of the body. Oxygen travels a fairly long way in the body (Fig. 18). Getting inside in the form of gas molecules, it already in the lungs takes part in a number of chemical reactions that ensure its further transportation to the cells of the body. There, entering the mitochondria, oxygen oxidizes various organic compounds, ultimately turning them into water and carbon dioxide. In this form, oxygen is removed from the body.

What makes oxygen from the atmosphere penetrate into the lungs, then into the blood, and from there into tissues and cells, where it enters into biochemical reactions? Obviously, there is a certain force that determines exactly this direction of movement of the molecules of this gas. This force is a concentration gradient. The oxygen content in atmospheric air is much greater than in the air of the intrapulmonary space (alveolar). The oxygen content in the alveoli - the pulmonary vesicles in which gas exchange between air and blood occurs - is much higher than in venous blood. Tissues contain much less oxygen than arterial blood, and mitochondria contain a small amount of oxygen, since the molecules of this gas entering them immediately enter a cycle of oxidative reactions and are converted into chemical compounds. This cascade of gradually decreasing concentrations, reflecting gradients of effort, as a result of which oxygen from the atmosphere penetrates into the cells of the body, is usually called the oxygen regime of the body (Fig. 19). More precisely, the oxygen regime is characterized by the quantitative parameters of the described cascade. The upper step of the cascade characterizes the oxygen content in the atmospheric air, which penetrates into the lungs during inhalation. The second step is the O2 content in the alveolar air. The third step is the O2 content in arterial blood, just enriched with oxygen. And finally, the fourth step is the oxygen tension in the venous blood, which gives the oxygen it contains to the tissues. These four steps form three “flights” that reflect the real processes of gas exchange in the body. The “flight” between the 1st and 2nd steps corresponds to pulmonary gas exchange, between the 2nd and 3rd steps - oxygen transport by blood, and between the 3rd and 4th steps - tissue gas exchange. The greater the height of the step, the greater the concentration difference, the higher the gradient at which oxygen is transported at this stage. With age, the height of the first “flight” increases, that is, the gradient of pulmonary gas exchange; the second “span”, i.e. the gradient of 02 transport by blood, while the height of the third “span”, reflecting the gradient of tissue gas exchange, decreases. An age-related decrease in the intensity of tissue oxidation is a direct consequence of a decrease in the intensity of energy metabolism with age.

Rice. 19. Oxygen transport in humans (direction shown by arrows)

Rice. 20. Cascade of oxygen tension in the inhaled air (I), in the alveoli (A), arteries (a) and veins (K) In a 5-year-old boy, a 15-year-old teenager and a 30-year-old adult

WHAT IS CARBON DIOXIDE?

Life on Earth has evolved over billions of years high concentration carbon dioxide. And carbon dioxide became a necessary component of metabolism. Animal and human cells require about 7 percent carbon dioxide. And oxygen is only 2 percent. Embryologists have established this fact. In the first days, the fertilized egg is in an almost oxygen-free environment - oxygen is simply destructive for it. And only as implantation and the formation of placental blood circulation gradually begins, the aerobic method of energy production begins to be implemented.

Fetal blood contains little oxygen and a lot of carbon dioxide compared to adult blood.

One of the fundamental laws of biology states that each organism in its own individual development repeats the entire evolutionary path of its species, starting from a single-celled creature and ending with a highly developed individual. And in fact, we all know that in the womb we were first a simple single-celled creature, then a multicellular sponge, then the embryo looked like a fish, then a newt, a dog, a monkey, and, finally, a human.

Not only the fruit itself undergoes evolution, but also its gaseous environment. The fetal blood contains 4 times less oxygen and 2 times more carbon dioxide than that of an adult. If the fetal blood begins to saturate with oxygen, it dies instantly.

Excess oxygen is detrimental to all living things, because oxygen is a strong oxidizing agent that, under certain conditions, can destroy cell membranes.

In a newborn child, after the first respiratory movements, a high level of carbon dioxide was also detected when blood was taken from the umbilical artery. Does this mean that the mother’s body strives to create an environment for the normal development of the fetus, such as it was on the planet billions of years ago?

But take another fact: mountaineers almost do not suffer from such ailments as asthma, hypertension or angina pectoris, which are common among city dwellers.

Is it because at an altitude of three to four thousand meters the oxygen content in the air is much less? As altitude increases, the density of the air decreases, and the amount of oxygen in the inhaled volume decreases accordingly, but paradoxically, this has a positive effect on human health.

It is a remarkable fact that exercises that cause hypoxia on the plains turn out to be more beneficial for health than simply staying in the mountains, even for those who can easily tolerate a mountain climate. This is due to the fact that when breathing rarefied mountain air, a person breathes deeper than usual in order to get more oxygen. Deeper inhalations automatically lead to deeper exhalations, and since we are constantly losing carbon dioxide as we exhale, deepening our breathing causes us to lose too much carbon dioxide, which can adversely affect our health.

Let us note in passing that mountain sickness is associated not only with oxygen deficiency, but also with excessive loss of carbon dioxide during deep breathing.

The benefits of such aerobic cyclic exercises as running, swimming, rowing, cycling, skiing, etc. are largely determined by the fact that a mode of moderate hypoxia is created in the body, when the body’s need for oxygen exceeds the ability of the respiratory apparatus to satisfy this need, and hypercapnia, when The body produces more carbon dioxide than the body can release through the lungs.

Theory of life in summary is this:

carbon dioxide is the basis of nutrition for all life on Earth; if it disappears from the air, all living things will die.
Carbon dioxide is the main regulator of all functions in the body, the main environment of the body, the vitamin of all vitamins. It regulates the activity of all vitamins and enzymes. If there is not enough of it, then all vitamins and enzymes work poorly, defectively, abnormally. As a result, metabolism is disrupted, and this leads to allergies, cancer, and salt deposits.

In the process of gas exchange, oxygen and carbon dioxide are of primary importance.

Oxygen enters the body along with the air, through the bronchi, then enters the lungs, from there into the blood, and from the blood into the tissues. Oxygen seems to be a kind of valuable element, it is like the source of all life, and some even compare it with the well-known concept of “Prana” from yoga. There is no more wrong opinion. In fact, oxygen is a regenerating element, serving to cleanse the cell of all its waste and, in some way, to burn it. Cell waste must be constantly purified, otherwise increased intoxication or death occurs. Brain cells are the most sensitive to intoxication; they die without oxygen (in the case of apnea) after four minutes.
Carbon dioxide goes through this chain in the opposite direction: it is formed in the tissues, then enters the blood and from there it is removed from the body through the respiratory tract.

In a healthy person, these two processes are in a state of constant equilibrium, when the ratio of carbon dioxide and oxygen is 3:1.

Carbon dioxide, contrary to popular belief, is needed by the body no less than oxygen. Carbon dioxide pressure affects the cerebral cortex, respiratory and vasomotor centers, carbon dioxide also provides tone and a certain degree of readiness for activity of various parts of the central nervous system, is responsible for the tone of blood vessels, bronchi, metabolism, hormone secretion, electrolyte composition of blood and fabrics. This means that it indirectly affects the activity of enzymes and the speed of almost all biochemical reactions of the body. Oxygen serves as an energy material, and its regulatory functions are limited.

Carbon dioxide is the source of life and a regenerator of body function, and oxygen is an energy source.
In ancient times, the atmosphere of our planet was highly saturated with carbon dioxide (over 90%), it was, and is now, natural building material living cells. As an example, the reaction of plant biosynthesis is the absorption of carbon dioxide, the utilization of carbon and the release of oxygen, and it was at that time that very lush vegetation existed on the planet.

Carbon dioxide is also involved in the biosynthesis of animal protein, and some scientists see this as possible reason the existence of giant animals and plants many millions of years ago.

The presence of lush vegetation gradually led to a change in the composition of the air, the content of carbon dioxide decreased, but internal conditions Cell performance was still determined by the high carbon dioxide content. The first animals to appear on Earth and eat plants were in an atmosphere with a high carbon dioxide content. Therefore, their cells, and later those created on the basis of the ancient genetic memory The cells of modern animals and humans require a carbon dioxide environment within themselves (6-8% carbon dioxide and 1-2% oxygen) and in the blood (7-7.5% carbon dioxide).

Plants utilized almost all the carbon dioxide from the air and most of it, in the form of carbon compounds, fell into the ground along with the death of the plants, turning into minerals (coal, oil, peat). Currently, the atmosphere contains about 0.03% carbon dioxide and approximately 21% oxygen.

It is known that the air contains approximately 21% oxygen. At the same time, reducing it to 15% or increasing it to 80% will not have any effect on our body. It is known that the air exhaled from the lungs contains another 14 to 15% oxygen, evidence of which is the method artificial respiration mouth-to-mouth, which would otherwise be ineffective. Of the 21% oxygen, only 6% is adsorbed by body tissues. Unlike oxygen, our body immediately reacts to a change in the concentration of carbon dioxide in one direction or another by only 0.1% and tries to return it to normal. From this we can conclude that carbon dioxide is approximately 60-80 times more important than oxygen for our body.

Therefore, we can say that the effectiveness of external respiration can be determined by the level of carbon dioxide in the alveoli.

But for normal life there should be 7-7.5% carbon dioxide in the blood, and 6.5% in the alveolar air.

It cannot be obtained from the outside, since the atmosphere contains almost no carbon dioxide. Animals and humans receive it through the complete breakdown of food, since proteins, fats, and carbohydrates, built on a carbon basis, when burned with the help of oxygen in the tissues, form invaluable carbon dioxide - the basis of life. A decrease in carbon dioxide in the body below 4% is death.

The task of CO 2 is to trigger the respiratory reflex. When its pressure increases, a network of thin nerve endings (receptors) immediately sends a message to the bulbs of the spinal cord and brain, the respiratory centers, from where the command to begin the respiratory act follows. Therefore, carbon dioxide can be considered a watchdog, signaling danger. If hyperventilation occurs, the dog is temporarily placed outside the door.

Carbon dioxide regulates metabolism, as it serves as a raw material, and oxygen is used for combustion organic matter, that is, it is only an energy drink.

The role of carbon dioxide in the life of the body is very diverse. Here are just some of its main properties:

it is an excellent vasodilator;
is a sedative (tranquilizer) of the nervous system, and therefore an excellent anesthetic;
participates in the synthesis of amino acids in the body;
plays an important role in stimulating the respiratory center.

Most often, since carbon dioxide is vitally important, when it is lost excessively, defense mechanisms are activated to varying degrees, trying to stop its removal from the body. These include:

Spasm of blood vessels, bronchi and spasm of smooth muscles of all organs;
- narrowing of blood vessels;
- increased secretion of mucus in the bronchi, nasal passages, development of adenoids, polyps;
- membrane compaction due to cholesterol deposition, which contributes to the development of tissue sclerosis.

All these points, together with the difficulty of oxygen entering the cells when the carbon dioxide content in the blood decreases (Verigo-Bohr effect), leads to oxygen starvation, slowdown of venous blood flow (with subsequent persistent dilatation of the veins).
More than a hundred years ago, the Russian scientist Verigo, and then the Danish physiologist Christian Bohr, discovered the effect named after them.
It lies in the fact that with a deficiency of carbon dioxide in the blood, all biochemical processes of the body are disrupted. This means that the deeper and more intensely a person breathes, the greater the oxygen starvation of the body!
The more CO2 in the body (in the blood), the more CO2 (through arterioles and capillaries) reaches the cells and is absorbed by them.
An excess of oxygen and a lack of carbon dioxide lead to oxygen starvation.
It was discovered that without the presence of carbon dioxide, oxygen cannot be released from its bound state with hemoglobin (Verigo-Bohr effect), which leads to oxygen starvation of the body even with a high concentration of this gas in the blood.

The more noticeable the content of carbon dioxide in arterial blood, the easier it is to separate oxygen from hemoglobin and transfer it to tissues and organs, and vice versa - the lack of carbon dioxide in the blood contributes to the fixation of oxygen in red blood cells. Blood circulates throughout the body, but does not release oxygen! A paradoxical state arises: there is enough oxygen in the blood, but the organs signal its extreme lack. A person begins to choke, tries to inhale and exhale, tries to breathe more often and washes carbon dioxide out of the blood even more, fixing oxygen in red blood cells.

It is well known that during intense sports activities, the content of carbon dioxide in the blood of an athlete increases. It turns out that this is exactly what sport is useful for. And not only sports, but any exercise, gymnastics, physical work, in a word - movement.

Increasing CO 2 levels promote expansion small arteries(the tone of which determines the number of functioning capillaries) and an increase in cerebral blood flow. Regular hypercapnia activates the production of vascular growth factors, which leads to the formation of a more branched capillary network and optimization of tissue blood circulation in the brain.

You can also acidify the blood in the capillaries with lactic acid, and then a second wind effect occurs during prolonged physical exertion. To speed up the appearance of a second wind, athletes are advised to hold their breath as long as possible. An athlete runs a long distance, has no strength, everything is like a normal person. Normal person stops and says: “That’s it, I can’t take it anymore.” The athlete holds his breath and gets a second wind, and he runs on.

Breathing is controlled to some extent by the mind. We can force ourselves to breathe more often or less often, or even hold our breath completely. However, no matter how long we try to hold back our breath, there comes a moment when this becomes impossible. The signal for the next inhalation is not a lack of oxygen, which might seem logical, but an excess of carbon dioxide. It is the carbon dioxide accumulated in the blood that is a physiological stimulator of respiration. After the discovery of the role of carbon dioxide, it began to be added to the gas mixtures of scuba divers to stimulate the functioning of the respiratory center. The same principle is used in anesthesia.

The whole art of breathing consists in exhaling almost no carbon dioxide, losing as little of it as possible. Yogi breathing exactly meets this requirement.

And the breathing of ordinary people is chronic hyperventilation of the lungs, excessive removal of carbon dioxide from the body, which causes the occurrence of about 150 serious diseases, often called diseases of civilization.

ROLE OF CARBON DIOXIDE IN THE DEVELOPMENT OF ARTERIAL HYPERTENSION

Meanwhile, the statement that the root cause of hypertension is precisely the insufficient concentration of carbon dioxide in the blood can be verified very simply. You just need to find out how much carbon dioxide is in the arterial blood of hypertensive patients and healthy people. This is exactly what was done in the early 90s by Russian physiologists.

Conducted studies of the blood gas composition of large groups of the population of different ages, the results of which can be read in the book " Physiological role carbon dioxide and human performance" (N.A. Agadzhanyan, N.P. Krasnikov, I.N. Polunin, 1995) made it possible to draw an unambiguous conclusion about the cause of constant microvascular spasm - arteriolar hypertension. In the vast majority of the elderly people examined, at rest in the arterial blood contains 3.6-4.5% carbon dioxide (the norm is 6-6.5%).

Thus, factual evidence was obtained that the root cause of many chronic ailments characteristic of older people is the loss of their body’s ability to constantly maintain the carbon dioxide content in the arterial blood close to normal. And the fact that young and healthy people have 6 - 6.5% carbon dioxide in their blood is a long-known physiological axiom.

What determines the concentration of carbon dioxide in arterial blood?

Carbon dioxide C0 2 is constantly formed in the cells of the body. The process of its removal from the body through the lungs is strictly regulated by the respiratory center - the part of the brain that controls external respiration. In healthy people, at any given time, the level of ventilation of the lungs (frequency and depth of breathing) is such that CO 2 is removed from the body in exactly such an amount that at least 6% of it always remains in the arterial blood. A truly healthy (in the physiological sense) body does not allow the carbon dioxide content to decrease below this figure or increase by more than 6.5%.

It is interesting to note that the values of a huge number of very different indicators determined in studies conducted in clinics and diagnostic centers, in young and old people they differ by fractions, maximum by a few%. And only the levels of carbon dioxide in the blood differ by about one and a half times. There is no other such clear and concrete difference between healthy and sick people.

CARBON DIOXIDE IS A POWERFUL VASODILATOR (DILADATES VESSELS)

Carbon dioxide is a vasodilator that acts directly on the vascular wall, and therefore, when holding your breath, warm skin is observed. Holding your breath is an important component of the Bodyflex exercise. Everything happens as follows: You perform special breathing exercises(inhale, exhale, then pull in your stomach and hold your breath, take a stretching position, count to 10, then inhale and relax).

Bodyflex exercises help enrich the body with oxygen. If you hold your breath for 8–10 seconds, carbon dioxide accumulates in the blood. This helps dilate the arteries and prepares the cells to absorb oxygen much more efficiently. Supplemental oxygen helps with many problems, such as overweight, lack of energy and poor health.

Currently, medical scientists look at carbon dioxide as a powerful physiological factor regulation of numerous body systems: respiratory, transport, vasomotor, excretory, hematopoietic, immune, hormonal, etc.

It has been proven that the local effect of carbon dioxide on a limited area of tissue is accompanied by an increase in volumetric blood flow, an increase in the rate of oxygen extraction by tissues, an increase in their metabolism, restoration of receptor sensitivity, intensification of reparative processes and activation of fibroblasts. The general reactions of the body to the local effects of carbon dioxide include the development of moderate gas alkalosis, increased erythro- and lymphopoiesis.

Subcutaneous injections of CO 2 achieve hyperemia, which has a resorptive, bactericidal and anti-inflammatory, analgesic and antispasmodic effect. Carbon dioxide improves blood flow, circulation of the brain, heart and blood vessels for a long period. Carboxytherapy helps with the appearance of signs of skin aging, promotes figure correction, eliminates many cosmetic defects and even helps fight cellulite.

Increased blood circulation in the hair growth area allows you to awaken “sleeping” hair follicles, and this effect allows you to use carboxytherapy for baldness. What happens in the subcutaneous tissue? In fat cells, under the influence of carbon dioxide, lipolysis processes are stimulated, as a result of which the volume of adipose tissue decreases. A course of procedures helps get rid of cellulite or, at least, reduces the severity of this unpleasant phenomenon.

Age spots, age-related changes, scar changes and stretch marks are some other indications for this method. In the facial area, carboxytherapy is used to correct the shape of the lower eyelid, as well as to combat a double chin. The technique is prescribed for rosacea and acne.

So, it becomes clear that carbon dioxide in our body performs numerous and very important functions, and oxygen turns out to be only an oxidizer of nutrients in the process of energy production. But not only that, when the “burning” of oxygen does not occur completely, very toxic products are formed - free reactive oxygen species, free radicals. They are the main trigger in triggering the aging and degeneration of body cells, distorting very subtle and complex intracellular structures with uncontrolled reactions.

An unusual conclusion follows from the above:

The art of breathing is to exhale almost no carbon dioxide and lose as little of it as possible.

As for the essence of all breathing techniques, they basically do the same thing - they increase the level of carbon dioxide in the blood by holding the breath. The only difference is that in different techniques this is achieved in different ways - either by holding the breath after inhalation, or after exhalation, or by prolonged exhalation, or by prolonged inhalation, or combinations thereof.

If you add carbon dioxide to pure oxygen and let a seriously ill person breathe, his condition will improve to a greater extent than if he were breathing pure oxygen. It turned out that carbon dioxide, to a certain extent, promotes a more complete absorption of oxygen by the body. This limit is equal to 8% CO2. With an increase in CO2 content to 8%, O2 assimilation increases, and then with an even greater increase in CO2 content, O2 assimilation begins to fall. This means that the body does not excrete, but “loses” carbon dioxide with exhaled air, and some limitation of these losses should have a beneficial effect on the body.

If you reduce breathing even more, as yogis advise, then a person will develop super-endurance, high health potential, and all the prerequisites for longevity will arise.

When performing such exercises, we create hypoxia in the body - a lack of oxygen, and hypercapnia - an excess of carbon dioxide. It should be noted that even with the longest breath holds, the CO 2 content in the alveolar air does not exceed 7%, so you should be afraid harmful effects We don’t need excessive doses of CO 2.

Studies show that exposure to dosed hypoxic-hypercapnic training for 18 days for 20 minutes daily is accompanied by a statistically significant improvement in well-being by 10%, an improvement in logical thinking ability by 25% and an increase in RAM capacity by 20%.

You need to try to breathe shallowly all the time (so that the breathing is neither noticeable nor audible) and rarely, trying to stretch out the automatic pauses as much as possible after each exhalation.

Yogis say that every person is born with a certain number of breaths and needs to take care of this reserve. In this original form, they call for reducing the breathing rate.

Let us recall that Patanjali called pranayama “stopping the movement of inhaled and exhaled air,” that is, in essence, hypoventilation. It should also be remembered that according to the same source, pranayama “makes the mind fit for concentration.”

Indeed, each organ, each cell has its own life reserve - a genetically laid down program of work with a certain limit. Optimal implementation of this program will bring a person health and longevity (as far as genetic code). Neglecting it and violating the laws of nature lead to illness and premature death.

Why in lemonades and mineral water add carbon dioxide?
CO ( carbon monoxide) toxic - not to be confused with CO 2 (carbon dioxide)
Kumbhaka, or hypoventilation techniques in yoga
What we breathe - the meaning of oxygen, nitrogen and carbon dioxide
Carboxytherapy - beauty gas injections
What are the consequences of increasing carbon dioxide in the atmosphere for living organs?
The role of carbon dioxide in maintaining health
The role of carbon dioxide in life

Breathing for Energy

Creating new molecules, and ultimately building new cells, requires energy. No less of it is spent on the work of individual organs and tissues. All energy costs of the body are covered by the oxidation of proteins, fats and carbohydrates, or, simply put, by the combustion of these substances.

Oxygen is required for oxidation. The respiratory organs are busy delivering it. In humans, this function is performed by the lungs. However, one should not call breathing the rhythmic movements of the chest, as a result of which air is either sucked into the lungs or squeezed out. This is not breathing itself, but only the transportation of the oxygen necessary for it.

The essence of breath is oxidative processes, which only vaguely resemble combustion and cannot in any way be identified with it. During normal combustion, oxygen is directly attached to the substance being oxidized. During the biological oxidation of proteins, fats or carbohydrates, hydrogen is removed from them, which, in turn, reduces oxygen, forming water. Remember this pattern of tissue respiration, we will have to return to it later.

Oxidation is the most important way to obtain energy. That is why astronomers, when studying the planets of the solar system, first of all try to find out whether they have oxygen and water. Where they exist, life can be expected to exist. It is not for nothing that the joyful news of the world’s first soft landing of the Soviet interplanetary station “Venera-4” on the planet Venus was overshadowed by the message that in its atmosphere there is practically no free oxygen, very little water and the temperature reaches 300 degrees.

However, there is no need to be discouraged. Even if there are absolutely no traces of life on Venus, all is not lost for this planet. It is possible to settle in the upper layers of its atmosphere, where it is not so hot, primitive single-celled plants that would consume carbon dioxide and produce oxygen. The very high density of the Venusian atmosphere will allow tiny single-celled creatures to swim in it without falling to the surface of the planet. With the help of such organisms, it would ultimately be possible to radically change the gas composition of the atmosphere of Venus.

This task is quite possible for green plants. After all, our earthly atmosphere as we know it was created by living organisms. Now the Earth's plants annually consume 650 billion tons of carbon dioxide, while they produce 350 billion tons of oxygen. Once upon a time, there was much less oxygen in the earth’s atmosphere than there is now, and much more carbon dioxide. You just need to be patient. A few hundred million years will probably be enough to radically transform the atmosphere of Venus. There is reason to believe that by that time the temperature on this planet will drop significantly (after all, it was once hot on Earth). Then earthlings will be able to feel completely at home there!

Oxygen supply

To live, you need to get oxygen somewhere, and then supply it to every cell of the body. Most animals on our planet draw oxygen from the atmosphere or extract oxygen dissolved in water. For this, the lungs or gills are used, and then the blood delivers it to all corners of the body.

At first glance, it may seem that extracting oxygen from water or air is the most difficult part of the task. Nothing happened. The animals did not have to come up with any special devices. Oxygen penetrates into the blood flowing through the lungs or gills only due to diffusion, that is, because there is less of it in the blood than in the environment, and gaseous and liquid substances try to be distributed so that their content is the same everywhere.

Nature did not immediately think of lungs and gills. The first multicellular living organisms did not have them; they breathed through the entire surface of the body. All subsequent more developed animals, including humans, although they acquired special respiratory organs, did not lose the ability to breathe through the skin. Only animals wearing armor: turtles, armadillos, crabs and the like do not enjoy this privilege.

In humans, the entire surface of the body takes part in breathing, from the thickest epidermis of the heels to the hairy scalp. The skin on the chest, back and abdomen breathes especially intensely. Interestingly, these areas of the skin are significantly more intense than the lungs in terms of breathing intensity. So, for example, from a respiratory surface of the same size, oxygen can be absorbed here by 28 percent, and carbon dioxide can be released even by 54 percent more than in the lungs.

What causes this superiority of the skin over the lungs is unknown. Perhaps it’s because our skin breathes clean air, but we don’t ventilate our lungs well. Even with the deepest exhalation, a certain supply of air remains in the lungs, which is far from the best composition, in which there is much less oxygen than in the outside atmosphere, and a lot of carbon dioxide. When we take another breath, the newly incoming air mixes with the air already in the lungs, and this greatly reduces the quality of the latter. It’s no wonder if this is where the advantage of skin breathing lies.

However, the share of skin in the overall respiratory balance of a person is negligible compared to the lungs. After all, its total surface area in humans barely reaches 2 square meters, while the surface of the lungs, if you expand all 700 million alveoli, microscopic bubbles through the walls of which gas exchange occurs between air and blood, is at least 90–100, that is, 45–50 times larger.

Breathing through the outer coverings of the body can only provide oxygen to very small animals. Therefore, even at the dawn of the animal kingdom, nature tried on what to use for this. First of all, the choice fell on the digestive organs.

Coelenterates consist of only two layers of cells. The external extracts oxygen from the environment, the internal from water freely flowing into the intestinal cavity. Already flatworms, owners of more complex digestive organs, they could not use them for breathing. And they were forced to remain flat, since diffusion in a large volume is not able to provide oxygen to deep-lying tissues.

Many of the annelids that appeared on Earth after the flatworms also make do with cutaneous respiration, but this turned out to be possible only because they already had circulatory organs that carry oxygen throughout the body. However, some ringworms acquired the first special organ for extracting oxygen from surrounding water- gills.

In all subsequent animals, similar organs were built mainly according to two schemes. If oxygen had to be obtained from water, then these were special outgrowths or protrusions, freely washed by water. If oxygen was extracted from the air, these were depressions from a simple sac, which is the respiratory organ grape snail or the lungs of newts and salamanders, to the complex, grape-like blocks of microscopic vesicles that became the lungs of mammals.

Breathing conditions in water and on land differ greatly from each other. Under the most favorable conditions, a liter of water contains only 10 cubic centimeters of oxygen, while a liter of air contains 210, that is, 20 times more. It may therefore be surprising that respiratory organs aquatic animals cannot extract sufficient oxygen from such a rich environment as air. The structure of the gills is such that they could successfully cope with their task in the air if their thin plates, deprived of the support provided by water, did not stick together and, deprived of protection, did not dry out. And this causes a cessation of blood circulation and thereby a suspension of respiratory function.

The origin of the respiratory organs is interesting. To create them, nature used what was tested in very lowly organized creatures: the skin and digestive organs. The gills of sea worms are just highly complicated outgrowths of the outer integument. In all vertebrates, the gills and lungs are derived in origin from the foregut.

The respiratory system of insects is very unique. They decided that there was no point in complicating the issue too much. The easiest way is to allow air to directly reach each of the organs, wherever they are located. This is done very simply. The entire body of insects is permeated with a system of complex branching tubes. Even the brain is riddled with air-carrying tracheas, so that the wind literally blows through their heads.

The tracheae, branching, decrease in diameter until they become very thin, thanks to which they can approach literally every cell of the body, and here they often break up into a bunch of very small tracheoles, with a diameter of less than one micron, which enter directly into the protoplasm of the cells, so that oxygen in insects is delivered directly to its destination. There are especially many tracheoles in cells that intensively consume oxygen: in large cells of the flight muscles they create entire plexuses.

The airways of insects can themselves look for places where oxygen becomes scarce. This is how the tracheoles of the epidermis behave, tiny, with a diameter of less than one micron and a length of no more than a third of a millimeter, blindly ending tubes. When tissue areas that intensively consume oxygen appear near them, the surrounding tracheoles begin to stretch, often increasing in length by a whole millimeter.

At first glance, it seems that insects have successfully solved the problem of oxygen supply, but practice does not confirm this. A strong draft in their body can quickly dry out an insect. To prevent this from happening, the tracheal openings open only very short term, and in many aquatic insects they are completely sealed. In this case, oxygen, by diffusion through the integument of the body or gills, seeps into the airways and spreads further along them, also by diffusion.

Large land insects breathe actively. The abdominal muscles contract 70–80 times per minute, it flattens, and the air is squeezed out. Then the muscles relax, the abdomen takes its previous shape, and air is sucked inside. Interestingly, different breathing holes are most often used for inhalation and exhalation; inhalation is through the chest, exhalation through the abdominal.

Often the main respiratory organs are unable to perform their task. This is observed in animals that have moved to an environment that is extremely poor in oxygen or completely unusual for them. And here is something that nature does not attract to help the main respiratory organs.

First of all, already proven means are widely used and modernized. In the south of our homeland, a small fish is widely known - the loach. It is often found in streams that dry up in the summer, in oxbow lakes that have completely lost connection with the river. In such reservoirs the bottom is usually muddy, there is a mass of rotting plants, and therefore in the hot summer there is very little oxygen in the water. To avoid suffocation, loaches have to “feed” on air. Simply put, they eat it, swallow it and pass it through their intestines like food. Digestion occurs in the front of the intestine, breathing in the back.

In order for digestion to interfere with breathing less, in the middle part of the intestine there are special secretory cells that envelop food debris that comes here with mucus, due to which they very quickly pass through the respiratory part of the intestine. Our other two freshwater fish, the loach and the spiny loach, breathe in exactly the same way. It is unlikely that it is convenient for one organ to perform double functions (breathing and digestion). Apparently, this is why a large order of freshwater fish from tropical Asia developed an additional respiratory apparatus - a labyrinth - a system of very complexly intertwined channels and cavities located in the expanded part of the first gill arch.

Scientists did not immediately understand the meaning of the labyrinth. The famous Cuvier, who, while dissecting crappies, first discovered and christened this mysterious organ, suggested that in the labyrinth fish hold water when they climb out of the reservoir. Anabas loves to travel, easily crawling from one body of water to another.

Observations of fish in nature also did not help to clarify the function. The English zoologist Commerson, the first European to meet a rather large fish - gourami, which the local population had long bred in ponds, named it Osphromenus olfacs, which in Latin means olfactory sniffer. Watching the fish, the Englishman saw that they were constantly rising to the surface and, sticking their snout out, sucking in air. In those days, no one could have imagined that fish breathed air! So Commerson decided that gouramis float up to find out what the world smells like.

Much later, when they got to aquarists in Europe, it became clear that labyrinth fish breathe air. Their gills are underdeveloped, and the labyrinth plays a prominent role in providing oxygen. They cannot live without air. If they are placed in an aquarium with the cleanest, oxygen-rich water, but are deprived of the ability to float to the surface and take in air, labyrinth fish will simply “choke” and “drown.”

It's not easy for frogs to breathe either; their lungs are far from first-class, so they sometimes have to get more sophisticated. In 1900, a hairy frog was caught in Gabon, Africa. This news shook the entire scientific world. In scientific circles it was considered precisely established that hair is the prerogative of mammals. Frogs, as you know, “walk” naked. It was not clear why Gabonese fashionistas have fur on their sides and paws. It was hard to imagine that they were cold. After all, if even our northern frogs, living almost at the Arctic Circle, do not freeze, then why did their African sisters become cold?

The secret of frog coats did not last long. As soon as you looked at the strange fur under a microscope, it became clear that these were simple skin outgrowths. Such “wool”, of course, cannot warm, and in Gabon there is no cold weather. Subsequent studies showed that hair in frogs functions as a kind of gills, with the help of which they breathe both in water and on land. Only males grow fur. During the breeding season, considerable physical activity falls on their shoulders, and if they did not have “hair,” shortness of breath and lack of oxygen would prevent it from being completed.

Even more interesting is the mudskipper's breathing. This fish lives in tropical India and not so much in water as in mud. Fish are more likely land creatures. They can travel long distances by land and are even excellent tree climbers. On the shore, these fish breathe with their tail, the skin of which has a highly branched blood network.

A funny mistake occurred while studying the breathing of mudskippers. Simply put, the jumpers turned out to be malicious deceivers. Scientists have noticed that although the fish spend most of the day on land, where they mainly get their food, deftly grabbing insects flying by, they do not like to completely part with water. Most often they sit at the edges of the puddle, with their tails dangling in the water. Having jumped after a butterfly flying past, the fish backs away until it lowers its tail into the water.

Observing such scenes, scientists decided that with the help of the tail the jumper extracts oxygen from the water. However, when they decided to measure the amount of oxygen contained in the water, they saw: there is so little of it there that it makes no sense to wet the tail. As it has now turned out, with the help of its tail, the jumper sucks water, which it really needs in order to moisturize the rest of the body and secrete a sufficient amount of mucus. At this time, it receives almost no oxygen through its tail. But when, having stocked up with a sufficient amount of water, it leaves the reservoir, the tail becomes the main respiratory apparatus.

Umbra, or, as we call it, the eudofish, breathes with a swim bladder. She lives in Moldova in the lower reaches of the Dniester and Danube. The swim bladder of a jewfish is connected to the pharynx by a wide duct. Leaning out of the water, the fish fills the bladder with air. It is densely braided blood vessels, and oxygen easily penetrates the blood here. The umber spits out exhaust air saturated with carbon dioxide from time to time. Breathing through a swim bladder is no fun for an umber. If she is deprived of the ability to swallow air, she will live no more than a day.

Not only for umber, but also for many fish, air is absolutely necessary, although for a different reason. The fry of most fish, having hatched from the egg, must take at least one breath. This is why fish most often spawn in shallow places. Otherwise, weak babies will not have enough strength to float to the surface. The fry need air to fill their swim bladder. In a few days, the duct connecting the bladder with the esophagus will become overgrown, and the fish, deprived of the ability to voluntarily reduce their specific weight, will die from overwork.

In open-bladder fish, the swim bladder duct does not become overgrown. These fish, until a very old age, retain the ability to swallow new portions of air when they are going to swim at the surface, and to squeeze out the excess if they want to go down to the depths. But, apparently, rising to the surface is not always safe, and therefore fish more often use another method to maintain the amount of gases in the bladder at the right level. This method is the active secretion of gases using the gas gland.

Even at the dawn of the study of breathing, it was assumed that oxygen entering the lungs was captured by the wall of the alveoli, which then secreted it into the blood. This theory subsequently did not come true. The point is not that such phenomena are impossible, it’s just that they turned out to be unnecessary in the lungs. For the swim bladder of closed-vesical fish, this method turned out to be the only possible one. The main working organ of the gland is a wonderful network consisting of three capillary plexuses connected in series. It was calculated that the volume of blood that can fit in the wonderful network is small, about one drop, but the area of the network is huge, because it consists of 88 thousand venous and 116 thousand arterial capillaries, the total length of which is almost a kilometer. In addition, the gland has many tubules. It is believed that the secretion she secretes into the lumen of the bladder disintegrates there, releasing oxygen and nitrogen.

Due to the fact that the gas in the swim bladder is created by the gland, and is not taken from the atmosphere, its composition is very different from the outside air. Most often, oxygen predominates there, sometimes up to 90 percent.

Redox reactions continuously occurring in every cell of the body require a constant supply of oxidation substrates (carbohydrates, lipids and amino acids) and an oxidizing agent - oxygen. The body has impressive reserves of nutrients - carbohydrate and fat depots, as well as a huge supply of proteins in skeletal muscles, so even a relatively long (several days) fasting does not cause significant harm to a person. But there are practically no reserves of oxygen in the body, except for the small amount contained in the muscles in the form of oxymyoglobin, therefore, without its supply, a person can survive only 2-3 minutes, after which the so-called “clinical death” occurs. If the supply of oxygen to brain cells is not restored within 10-20 minutes, biochemical changes will occur in them that will disrupt their functional properties and lead to the rapid death of the entire organism. Other cells in the body may not be affected to the same extent, but nerve cells are extremely sensitive to lack of oxygen. That is why one of the central physiological systems of the body is the functional oxygen supply system, and the state of this particular system is most often used to assess “health”.

What makes oxygen from the atmosphere penetrate into the lungs, then into the blood, and from there into tissues and cells, where it enters into biochemical reactions? Obviously, there is a certain force that determines exactly this direction of movement of the molecules of this gas. This force is a concentration gradient. The oxygen content in atmospheric air is much greater than in the air of the intrapulmonary space (alveolar). The oxygen content in the alveoli - the pulmonary vesicles in which gas exchange between air and blood occurs - is much higher than in venous blood. Tissues contain much less oxygen than arterial blood, and mitochondria contain a small amount of oxygen, since the molecules of this gas entering them immediately enter a cycle of oxidative reactions and are converted into chemical compounds. This cascade of gradually decreasing concentrations, reflecting gradients of effort, as a result of which oxygen from the atmosphere penetrates into the cells of the body, is usually called the oxygen regime of the body (Fig. 19). More precisely, the oxygen regime is characterized by the quantitative parameters of the described cascade. The upper step of the cascade characterizes the oxygen content in the atmospheric air, which penetrates into the lungs during inhalation. The second step is the O2 content in the alveolar air. The third step is the O2 content in arterial blood, just enriched with oxygen. And finally, the fourth step is the oxygen tension in the venous blood, which gives the oxygen it contains to the tissues. These four steps form three “flights” that reflect the real processes of gas exchange in the body. The “flight” between the 1st and 2nd steps corresponds to pulmonary gas exchange, between the 2nd and 3rd steps - oxygen transport by blood, and between the 3rd and 4th steps - tissue gas exchange. The greater the height of the step, the greater the concentration difference, the higher the gradient at which oxygen is transported at this stage. With age, the height of the first “flight” increases, that is, the gradient of pulmonary gas exchange; the second “span”, i.e. the gradient of 02 transport by blood, while the height of the third “span”, reflecting the gradient of tissue gas exchange, decreases. An age-related decrease in the intensity of tissue oxidation is a direct consequence of a decrease in the intensity of energy metabolism with age.

Rice. 19. Oxygen transport in humans (direction shown by arrows)

Rice. 20. Cascade of oxygen tension in the inhaled air (I), in the alveoli (A), arteries (a) and veins (K) In a 5-year-old boy, a 15-year-old teenager and a 30-year-old adult

Breath

Exchange of gases in the lungs. The lungs are sealed bags connected to the trachea through large airways - the bronchi. Atmospheric air penetrates through the nasal and oral cavities into the larynx and further into the trachea, after which it is divided into two streams, one of which goes to the right lung, the other to the left (Fig. 20). The trachea and bronchi consist of connective tissue and a framework of cartilaginous rings that prevent these tubes from bending and blocking the airways with various changes in body position. Upon entering the lungs, the bronchi divide into many branches, each of which divides again, forming the so-called “bronchial tree”. The thinnest branches of this “tree” are called bronchioles, and at their ends there are pulmonary vesicles, or alveoli (Fig. 21). The number of alveoli reaches 350 million, and their total area is 150 m2. It is this surface that represents the area for the exchange of gases between blood and air. The walls of the alveoli consist of a single layer of epithelial cells, to which the thinnest blood capillaries, also consisting of single-layer epithelium, come close. This design, due to diffusion, ensures relatively easy penetration of gases from the alveolar air into the capillary blood (oxygen) and in the opposite direction (carbon dioxide). This gas exchange occurs as a result of the creation of a gas concentration gradient (Fig. 22). The air in the alveoli contains a relatively large amount of oxygen (103 mm Hg) and a small amount of carbon dioxide (40 mm Hg). In capillaries, on the contrary, the concentration of carbon dioxide is increased (46 mm Hg), and oxygen is reduced (40 mm Hg), since these capillaries contain venous blood, collected after it has been in the tissues and given away they receive oxygen and receive carbon dioxide in return. Blood flows continuously through the capillaries, and the air in the alveoli is renewed with every breath. The blood flowing from the alveoli, enriched with oxygen (up to 100 mm Hg), contains relatively little carbon dioxide (40 mm Hg) and is again ready for tissue gas exchange.

Rice. 21. Scheme of the structure of the lungs (A) and pulmonary alveoli (B)

A: ] - larynx; 2 - trachea; 3 - bronchi; 4 - bronchioles; 5 - light;

B: 1 - vascular network; 2, 3 - alveoli from the outside and in section; 4 -

bronchiole; 5 - artery and vein

Rice. 22. Scheme of branching of the airways (left). The right side of the figure shows a curve of the total cross-sectional area of the airways at the level of each branch (3). At the beginning of the transition zone, this area begins to increase significantly, which continues in the respiratory zone. Br - bronchi; Bl - bronchioles; TBl - terminal bronchioles; DBL - respiratory bronchioles; AH - alveolar ducts; A - alveoli

Rice. 23. Exchange of gases in the pulmonary alveoli: through the wall of the pulmonary alveoli, O 2 of inhaled air enters the blood, and CO 2 of venous blood enters the alveoli; gas exchange is ensured by the difference in partial pressures (P) of CO 2 and O 2 in the venous blood and in the cavity of the pulmonary alveoli

To prevent the smallest bubbles - the alveoli - from collapsing during exhalation, their surface is covered from the inside with a layer of a special substance produced by the lung tissue. This substance is surfactant- reduces the surface tension of the walls of the alveoli. It is usually produced in excess to ensure maximum use of the lung surface area for gas exchange.

Diffusion capacity of the lungs. The gas concentration gradient on both sides of the alveolar wall is the force that causes oxygen and carbon dioxide molecules to diffuse and penetrate through this wall. However, at the same atmospheric pressure, the rate of diffusion of molecules depends not only on the gradient, but also on the contact area of the alveoli and capillaries, on the thickness of their walls, on the presence of surfactant and a number of other reasons. In order to evaluate all these factors, special instruments are used to measure the diffusion capacity of the lungs, which, depending on the age and functional state of a person, can vary from 20 to 50 ml O 2 / min / mm Hg. Art.

Ventilation-perfusion ratio. Gas exchange in the lungs occurs only if the air in the alveoli is periodically (in each respiratory cycle) renewed, and blood continuously flows through the pulmonary capillaries. It is for this reason that cessation of breathing, as well as cessation of blood circulation, equally means death. The continuous flow of blood through capillaries is called perfusion, and the rhythmic flow of new portions of atmospheric air into the alveoli - ventilation. It should be emphasized that the composition of the air in the alveoli is very different from that of the atmosphere: the alveolar air contains much more carbon dioxide and less oxygen. The fact is that mechanical ventilation of the lungs does not affect the deepest zones in which the pulmonary vesicles are located, and there gas exchange occurs only due to diffusion, and therefore somewhat slower. Nevertheless, each respiratory cycle brings new portions of oxygen into the lungs and removes excess carbon dioxide. The rate of perfusion of lung tissue with blood must exactly match the rate of ventilation so that an equilibrium is established between these two processes, otherwise either the blood will be oversaturated with carbon dioxide and undersaturated with oxygen, or, conversely, carbon dioxide will be washed out of the blood. Both are bad, since the respiratory center, located in the medulla oblongata, generates impulses that force the respiratory muscles to inhale and exhale, under the influence of receptors that measure the content of CO 2 and O 2 in the blood. If CO 2 levels in the blood drop, breathing may stop; if it grows, shortness of breath begins, the person feels suffocated. The relationship between the rate of blood flow through the pulmonary capillaries and the rate of air flow ventilating the lungs is called the ventilation-perfusion ratio (VPR). The ratio of O2 and CO2 concentrations in exhaled air depends on it. If the increase in CO2 (compared to atmospheric air) exactly corresponds to the decrease in oxygen content, then HPO = 1, and this is an increased level. Normally, the VPO is 0.7-0.8, i.e., perfusion should be somewhat more intense than ventilation. The value of HPO is taken into account when identifying certain diseases of the bronchopulmonary system and the circulatory system.

If you deliberately sharply intensify your breathing, taking the deepest and most frequent inhalations and exhalations, then the HPE will exceed 1, and the person will soon feel dizzy and may faint - this is the result of “washing out” excess amounts of CO 2 from the blood and disruption of acid-base homeostasis. On the contrary, if you hold your breath through an effort of will, then the GPO will be less than 0.6 and after a few tens of seconds the person will feel suffocation and an imperative urge to breathe. At the beginning of muscular work, the VPO changes sharply, first decreasing (perfusion increases, since the muscles, having begun to contract, squeeze out additional portions of blood from their veins), and after 15-20 s rapidly increasing (the respiratory center is activated and ventilation increases). HPE is normalized only 2-3 minutes after the start of muscle work. At the end of muscular work, all these processes occur in the reverse order. In children, such a reconfiguration of the oxygen supply system occurs a little faster than in adults, since the body size and, accordingly, the inertial characteristics of the heart, blood vessels, lungs, muscles and other structures involved in this reaction are significantly smaller in children.

Tissue gas exchange. The blood, which brings oxygen to the tissues, releases it (along a concentration gradient) into the tissue fluid, and from there O 2 molecules penetrate into the cells, where they are captured by mitochondria. The more intense this capture occurs, the faster the oxygen content in the tissue fluid decreases, the higher the gradient between arterial blood and tissue becomes, the faster the blood releases oxygen, disconnecting from the hemoglobin molecule, which served as a “vehicle” for oxygen delivery. The released hemoglobin molecules can capture CO2 molecules to carry them to the lungs and release them there to the alveolar air. Oxygen, entering the cycle of oxidative reactions in mitochondria, ultimately ends up combined with either hydrogen (H 2 O is formed) or carbon (CO 2 is formed). In free form, oxygen practically does not exist in the body. All carbon dioxide formed in the tissues is removed from the body through the lungs. Metabolic water also partially evaporates from the surface of the lungs, but can also be excreted through sweat and urine.

Respiratory coefficient. The ratio of the amounts of CO 2 formed and O 2 absorbed is called the respiratory coefficient (RC) and depends on which substrates are oxidized in the tissues of the body. DC in exhaled air ranges from 0.65 to 1. For purely chemical reasons during the oxidation of fats, DC = 0.65; during protein oxidation - about 0.85; during the oxidation of carbohydrates DC = 1.0. Thus, by the composition of exhaled air one can judge what substances are currently used to produce energy by the body’s cells. Naturally, usually DC takes some intermediate value, most often close to 0.85, but this does not mean that proteins are oxidized; rather, it is the result of the simultaneous oxidation of fats and carbohydrates. The value of the DC is closely related to the HPO; there is almost complete correspondence between them, except for periods when the HPO is subject to sharp fluctuations. In children at rest, DC is usually higher than in adults, which is associated with a significantly greater participation of carbohydrates in the energy supply of the body, especially in the activity of nervous structures.

External breathing- these are manifestations of the breathing process that are clearly visible without any instruments, since air enters and exits the airways only due to the fact that the shape and volume of the chest changes. What makes air penetrate deep into the body, ultimately reaching the smallest pulmonary bubbles? In this case, there is a force caused by the difference in pressure inside the chest and in the surrounding atmosphere. The lungs are surrounded by a connective tissue membrane called the pleura, and between the lungs and the pleural sac there is pleural fluid, which serves as a lubricant and sealant. The intrapleural space is sealed and does not communicate with neighboring cavities and digestive and blood pipes passing through the chest. The entire chest is also sealed, separated from the abdominal cavity not only by the serous membrane, but also by a large circular muscle - the diaphragm. Therefore, the efforts of the respiratory muscles, leading to even a slight increase in its volume during inspiration, provide a fairly significant vacuum inside the pleural cavity, and it is under the influence of this vacuum that air enters the oral and nasal cavities and penetrates further through the larynx, trachea, bronchi and bronchioles into the lung tissue .

Organization of the respiratory act. Three muscle groups are involved in organizing the respiratory act, i.e., in moving the walls of the chest and abdominal cavity: inspiratory (providing inhalation) external intercostal muscles; expiratory (providing exhalation) internal intercostal muscles and the diaphragm, as well as the muscles of the abdominal wall. The coordinated contraction of these muscles under the control of the respiratory center, which is located in the medulla oblongata, causes the ribs to move slightly forward and upward relative to their position at the time of exhalation, the sternum rises, and the diaphragm is pressed into the abdominal cavity. Thus, the total volume of the chest increases significantly, a fairly high vacuum is created there, and air from the atmosphere rushes into the lungs. At the end of inhalation, the impulse from the respiratory center to these muscles stops, and the ribs, under the force of their own gravity, and the diaphragm, as a result of its relaxation, return to the “neutral” position. The volume of the chest decreases, the pressure there increases, and excess air from the lungs is expelled through the same tubes through which it entered. If for some reason exhalation is difficult, then the expiratory muscles are activated to facilitate this process. They also work in cases where breathing intensifies or accelerates under the influence of emotional or physical stress. The work of the respiratory muscles, like any other muscular work, requires energy expenditure. It is estimated that during quiet breathing, a little more than 1% of the energy consumed by the body is spent on these needs.

Depending on whether the expansion of the chest during normal breathing is associated primarily with raising the ribs or flattening the diaphragm, costal (thoracic) and diaphragmatic (abdominal) types of breathing are distinguished. With thoracic breathing, the diaphragm moves passively in accordance with changes in intrathoracic pressure. With the abdominal type, powerful contractions of the diaphragm greatly displace the organs of the abdominal cavity, so when inhaling, the stomach “sticks out.” The formation of the type of breathing occurs at the age of 5-7 years, and in girls it usually becomes thoracic, and in boys - abdominal.

Pulmonary ventilation. The larger the body and the stronger the respiratory muscles work, the more air passes through the lungs during each respiratory cycle. To assess pulmonary ventilation, the minute volume of breathing is measured, i.e. the average amount of air that passes through the respiratory tract in 1 minute. At rest in an adult, this value is 5-6 l/min. In a newborn child, the minute breathing volume is 650-700 ml/min, by the end of 1 year of life it reaches 2.6-2.7 l/min, by 6 years - 3.5 l/min, at 10 years - 4.3 l /min, and in adolescents - 4.9 l/min. During physical activity, the minute volume of breathing can increase very significantly, reaching 100 l/min or more in young men and adults.

Frequency and depth of breathing. The respiratory act, consisting of inhalation and exhalation, has two main characteristics - frequency and depth. Frequency is the number of respiratory acts per minute. In an adult, this value is usually 12-15, although it can vary widely. In newborns, the respiratory rate during sleep reaches 50-60 per minute, by the age of one year it decreases to 40-50, then as they grow, this indicator gradually decreases. Thus, in children of primary school age, the respiratory rate is usually about 25 cycles per minute, and in adolescents - 18-20. The exact opposite trend of age-related changes is demonstrated by tidal volume, i.e. a measure of the depth of breathing. It represents the average amount of air that enters the lungs during each breathing cycle. In newborns it is very small - only 30 ml or even less, by the age of one it increases to 70 ml, at 6 years it becomes over 150 ml, by 10 years it reaches 240 ml, at 14 years - 300 ml. In an adult, the tidal volume at rest does not exceed 500 ml. Minute respiratory volume is the product of tidal volume and respiratory rate.

If a person performs any physical activity, he needs additional oxygen, and the minute volume of breathing increases accordingly. In children under 10 years of age, this increase is ensured mainly by increased breathing, which can become 3-4 times more frequent than breathing at rest, while tidal volume increases only 1.5-2 times. In adolescents, and even more so in adults, the increase in minute volume is carried out mainly due to tidal volume, which can increase several times, and the respiratory rate usually does not exceed 50-60 cycles per minute. It is believed that this type of respiratory system response is more economical. According to various criteria, the effectiveness and efficiency of external respiration increases significantly with age, reaching maximum values in boys and girls aged 18-20 years. At the same time, the breathing of boys, as a rule, is organized more efficiently than that of girls. The efficiency of breathing and its economy are greatly influenced by physical training, especially in those sports in which oxygen supply plays a decisive role. This includes distance running, skiing, swimming, rowing, cycling, tennis and other types of endurance sports.

Spirogram. If rubber bellows or a light bell immersed in water is placed in the path of air entering and leaving the lungs, then, thanks to the action of the respiratory muscles, this device will increase its volume when exhaling and decrease when inhaling. If all connections are sealed (a special rubber mouthpiece or a mask worn on the face is used to seal the oral cavity), then you can attach a writing instrument to the moving part of the device and record all breathing movements. Such a device, invented back in the 19th century, is called a spirograph, and the recording made with its help is a spirogram (Fig. 23). Using a spirogram made on a paper tape, you can quantitatively measure the most important characteristics of a person’s external respiration. Lung volumes and capacities. Thanks to the spirogram, you can clearly see and measure various lung volumes and capacities. In respiratory physiology, volumes are usually called those indicators that dynamically change during the breathing process and characterize the functional state of the respiratory system. A container is a reservoir that cannot be changed in a short time, within which the respiratory cycle and gas exchange occur. The reference point for all pulmonary volumes and capacities is the level of quiet expiration.

Lung volumes. At rest, tidal volume is small compared to the total volume of air in the lungs. Therefore, a person can both inhale and exhale a large additional volume of air. These volumes are named accordingly inspiratory reserve volume and expiratory reserve volume. However, even with the deepest exhalation, some air remains in the alveoli and airways. This is the so-called residual volume, which is not measured using a spirogram (to measure it, rather complex equipment and calculations are used, inert gases are used). In an adult it is about 1.5 liters, in children it is significantly less.

Rice. 24. Spirogram: lung capacity and its components

A - spirogram diagram: 1 - inspiratory reserve volume; 2 - tidal volume; 3 - reserve expiratory volume; 4 -- residual volume; 5 - functional residual capacity; 6 - inhalation capacity; 7 - vital capacity; 8 - total lung capacity; B - volumes and capacities of the lungs: / - young athletes; // - untrained schoolchildren (average age 13 years) (according to A.I. Osipov, 1964). The numbers above the bars are the average values of the total capacity. The numbers in the columns are the average values of lung volumes as a percentage of the total capacity; the numbers to the left of the bars correspond to the designations on the spirogram

Vital capacity of the lungs. The total value of inspiratory reserve volume, tidal volume and expiratory reserve volume is vital capacity(VC) is one of the most important indicators of the state of the respiratory system. To measure it, spirometers of various designs are used, into which you need to exhale as deeply as possible after inhaling as deeply as possible - this will be vital vital capacity. Vital capacity depends on body size, and therefore on age, and also very significantly depends on the functional state and physical fitness of the human body. Men have a higher vital capacity than women if neither of them engages in sports, especially endurance exercises. The value of vital capacity varies significantly among people of different physiques: in brachymorphic types it is relatively small, and in dolichomorphic types it is very large. It is customary to use vital capacity as one of the indicators of the physical development of school-age children, as well as conscripts. Vital vital capacity can only be measured with the active and conscious participation of the child, so there is practically no data on children under 3 years of age.