What is the percentage of oxygen in exhaled air? Chemical composition of air and its hygienic importance

Man breathes atmospheric air, which has the following composition: 20.94% oxygen, 0.03% carbon dioxide, 79.03% nitrogen. In the exhaled air 16.3% oxygen, 4% carbon dioxide, 79.7% nitrogen are detected.

Alveolar air its composition differs from that of the atmosphere. In the alveolar air, the oxygen content sharply decreases and the amount of carbon dioxide increases. Percentage content of individual gases in alveolar air: 14.2-14.6% oxygen, 5.2-5.7% carbon dioxide, 79.7-80% nitrogen.

STRUCTURE OF THE LUNGS.

The lungs are paired respiratory organs located in a hermetically sealed chest cavity. Their airways represented by the nasopharynx, larynx, trachea. The trachea in the chest cavity is divided into two bronchi - right and left, each of which, branching repeatedly, forms the so-called bronchial tree. The smallest bronchi - bronchioles at the ends expand into blind vesicles - pulmonary alveoli.

Gas exchange does not occur in the respiratory tract, and the composition of the air does not change. The space enclosed in the respiratory tract is called dead, or harmful. During quiet breathing, the volume of air in the dead space is 140-150 ml.

The structure of the lungs ensures that they perform the respiratory function. The thin wall of the alveoli consists of a single-layer epithelium, easily permeable to gases. The presence of elastic elements and smooth muscle fibers ensures quick and easy stretching of the alveoli, so that they can accommodate large amounts of air. Each alveolus is covered with a dense network of capillaries into which the pulmonary artery branches.

Each lung is covered on the outside with a serous membrane - pleura, consisting of two leaves: parietal and pulmonary (visceral). Between the layers of the pleura there is a narrow gap filled with serous fluid - pleural cavity.

The expansion and collapse of the pulmonary alveoli, as well as the movement of air along the airways, is accompanied by the appearance of respiratory sounds, which can be examined by auscultation (auscultation).

Pressure in the pleural cavity and mediastinum is always normal negative. Due to this, the alveoli are always in a stretched state. Negative intrathoracic pressure plays a significant role in hemodynamics, ensuring venous return of blood to the heart and improving blood circulation in the pulmonary circle, especially during the inhalation phase.

BREATHING CYCLE.

The respiratory cycle consists of inhalation, exhalation and a respiratory pause. Duration inhalation in an adult from 0.9 to 4.7 s, duration exhalation - 1.2-6 s. The breathing pause varies in size and may even be absent.

Breathing movements are performed with a certain rhythm and frequency, which are determined by the number of chest excursions in 1 minute. In an adult, the respiratory rate is 12-18 in 1 min.

Depth of breathing movements determined by the amplitude of chest excursions and using special methods that allow one to study pulmonary volumes.

Inhalation mechanism. Inhalation is ensured by expansion of the chest due to contraction of the respiratory muscles - the external intercostal muscles and the diaphragm. The flow of air into the lungs is largely dependent on the negative pressure in the pleural cavity.

Exhalation mechanism. Exhalation (expiration) occurs as a result of relaxation of the respiratory muscles, as well as due to the elastic traction of the lungs trying to take their original position. The elastic forces of the lungs are represented by the tissue component and surface tension forces, which tend to reduce the alveolar spherical surface to a minimum. However, the alveoli normally never collapse. The reason for this is the presence of a surfactant stabilizing substance in the walls of the alveoli - surfactant produced by alveolocytes.

PULMONARY VOLUME. PULMONARY VENTILATION.

Tidal volume- the amount of air that a person inhales and exhales during quiet breathing. Its volume is 300 - 700 ml.

Inspiratory reserve volume- the amount of air that can be introduced into the lungs if, following a quiet inhalation, a maximum inhalation is made. The inspiratory reserve volume is equal to 1500-2000 ml.

Expiratory reserve volume- the volume of air that is removed from the lungs if, following a calm inhalation and exhalation, a maximum exhalation is made. It amounts to 1500-2000 ml.

Residual volume- this is the volume of air that remains in the lungs after the deepest possible exhalation. The residual volume is equal to 1000-1500 ml air.

Tidal volume, inspiratory and expiratory reserve volumes
constitute the so-called vital capacity.
Vital capacity of the lungs in men young
amounts to 3.5-4.8 l, for women - 3-3.5 l.

Total lung capacity consists of the vital capacity of the lungs and the residual volume of air.

Pulmonary ventilation- the amount of air exchanged in 1 minute.

Pulmonary ventilation is determined by multiplying the tidal volume by the number of breaths per minute (minute volume of breathing). In an adult in a state of relative physiological rest, pulmonary ventilation is 6-8 l per 1 min.

Lung volumes can be determined using special devices - spirometer and spirograph.

TRANSPORT OF GASES BY BLOOD.

Blood delivers oxygen to tissues and carries away carbon dioxide.

The movement of gases from the environment into the liquid and from the liquid into the environment is carried out due to the difference in their partial pressure. Gas always diffuses from an environment where there is high pressure to an environment with lower pressure.

Partial pressure of oxygen in atmospheric air 21.1 kPa (158 mmHg st.), in the alveolar air - 14.4-14.7 kPa (108-110 mm Hg. st.) and in the venous blood flowing to the lungs - 5.33 kPa (40 mmHg st.). In the arterial blood of the capillaries of the systemic circulation, the oxygen tension is 13.6-13.9 kPa (102-104 mmHg), in the interstitial fluid - 5.33 kPa (40 mm Hg), in tissues - 2.67 kPa (20 mm Hg). Thus, at all stages of oxygen movement there is a difference in its partial pressure, which promotes gas diffusion.

The movement of carbon dioxide occurs in the opposite direction. Carbon dioxide tension in tissues is 8.0 kPa or more (60 or more mm Hg), in venous blood - 6.13 kPa (46 mm Hg), in alveolar air - 0.04 kPa (0 .3 mmHg). Hence, the difference in carbon dioxide tension along its route causes gas diffusion from tissues into the environment.

Transport of oxygen by blood. Oxygen in the blood is in two states: physical dissolution and in chemical connection with hemoglobin. Hemoglobin forms a very fragile, easily dissociated compound with oxygen - oxyhemoglobin: 1g of hemoglobin binds 1.34 ml of oxygen. The maximum amount of oxygen that can be bound in 100 ml of blood is blood oxygen capacity(18.76 ml or 19 vol%).

Hemoglobin oxygen saturation ranges from 96 to 98%. The degree of saturation of hemoglobin with oxygen and the dissociation of oxyhemoglobin (formation of reduced hemoglobin) are not directly proportional to oxygen tension. These two processes are not linear, but occur along a curve, which is called oxyhemoglobin binding or dissociation curve.

Rice. 25. Dissociation curves of oxyhemoglobin in an aqueous solution (I) and in blood (II) at a carbon dioxide tension of 5.33 kPa (40 mm Hg) (according to Barcroft).

At zero oxygen tension, there is no oxyhemoglobin in the blood. At low oxygen partial pressures, the rate of oxyhemoglobin formation is low. The maximum amount of hemoglobin (45-80%) binds to oxygen when its tension is 3.47-6.13 kPa (26-46 mm Hg). A further increase in oxygen tension leads to a decrease in the rate of oxyhemoglobin formation (Fig. 25).

The affinity of hemoglobin for oxygen is significantly reduced when the blood reaction shifts to the acidic side, which is observed in the tissues and cells of the body due to the formation of carbon dioxide

The transition of hemoglobin to oxyhemoglobin and from it to reduced one also depends on temperature. At the same partial pressure of oxygen in the environment at a temperature of 37-38 ° C, the largest amount of oxyhemoglobin passes into the reduced form,

Transport of carbon dioxide by blood. Carbon dioxide is transported to the lungs in the form bicarbonates and in a state of chemical bonding with hemoglobin ( carbohemoglobin).

RESPIRATORY CENTER.

The rhythmic sequence of inhalation and exhalation, as well as changes in the nature of respiratory movements depending on the state of the body, are regulated respiratory center located in the medulla oblongata.

There are two groups of neurons in the respiratory center: inspiratory And expiratory. When the inspiratory neurons that provide inspiration are excited, the activity of the expiratory nerve cells is inhibited, and vice versa.

At the top of the pons ( pons) located pneumotaxic center, which controls the activity of the lower inhalation and exhalation centers and ensures the correct alternation of cycles of respiratory movements.

The respiratory center, located in the medulla oblongata, sends impulses to motor neurons of the spinal cord, innervating the respiratory muscles. The diaphragm is innervated by axons of motor neurons located at the level III-IV cervical segments spinal cord. Motor neurons, the processes of which form the intercostal nerves that innervate the intercostal muscles, are located in the anterior horns (III-XII) of the thoracic segments spinal cord.

Air is natural mixture various gases. Most of all it contains elements such as nitrogen (about 77%) and oxygen, less than 2% are argon, carbon dioxide and other inert gases.

Oxygen, or O2, is the second element of the periodic table and the most important component, without which life on the planet would hardly exist. He participates in various processes, on which the vital activity of all living things depends.

In contact with

Air composition

O2 performs the function oxidative processes in the human body, which allow you to release energy for normal life. At rest, the human body requires about 350 milliliters of oxygen, with heavy physical activity this value increases three to four times.

What percentage of oxygen is in the air we breathe? The norm is 20,95% . Exhaled air contains less O2 – 15.5-16%. The composition of exhaled air also includes carbon dioxide, nitrogen and other substances. A subsequent decrease in the percentage of oxygen leads to malfunction, and a critical value of 7-8% causes death.

From the table you can understand, for example, that exhaled air contains a lot of nitrogen and additional elements, but O2 only 16.3%. The oxygen content of the inhaled air is approximately 20.95%.

It is important to understand what an element such as oxygen is. O2 – the most common on earth chemical element, which is colorless, odorless and tasteless. It performs the most important function of oxidation in.

Without the eighth element of the periodic table you can't make fire. Dry oxygen improves the electrical and protective properties of films and reduces their volume charge.

This element is contained in the following compounds:

1. Silicates - they contain approximately 48% O2.
2. (sea and fresh) – 89%.
3. Air – 21%.
4. Other compounds in the earth's crust.

Air contains not only gaseous substances, but also vapors and aerosols, as well as various contaminants. This could be dust, dirt, or other various small debris. It contains microbes, which can cause various diseases. Flu, measles, whooping cough, allergens and other diseases are just a small list of negative consequences that appear when air quality deteriorates and the level of pathogenic bacteria increases.

The percentage of air is the amount of all the elements that make up it. It is more convenient to show clearly what air consists of, as well as the percentage of oxygen in the air, on a diagram.

The diagram shows which gas is found more in the air. The values ​​shown on it will be slightly different for inhaled and exhaled air.

Diagram - air ratio.

There are several sources from which oxygen is formed:

1. Plants. It is also known from a school biology course that plants release oxygen when they absorb carbon dioxide.
2. Photochemical decomposition of water vapor. The process is observed under the influence of solar radiation in the upper layer of the atmosphere.
3. Mixing of air flows in the lower atmospheric layers.

Functions of oxygen in the atmosphere and for the body

For a person, the so-called partial pressure, which the gas could produce if it occupied the entire occupied volume of the mixture. The normal partial pressure at 0 meters above sea level is 160 millimeters of mercury. An increase in altitude causes a decrease in partial pressure. This indicator is important, since the supply of oxygen to all important organs and to the body depends on it.

Oxygen is often used for the treatment of various diseases. Oxygen cylinders and inhalers help human organs function normally in the presence of oxygen starvation.

Important! The composition of air is influenced by many factors; accordingly, the percentage of oxygen may change. The negative environmental situation leads to deterioration in air quality. In megacities and large urban settlements, the proportion of carbon dioxide (CO2) will be greater than in small settlements or in forests and protected areas. Altitude also has a big impact - the percentage of oxygen will be lower in the mountains. You can consider the following example - on Mount Everest, which reaches a height of 8.8 km, the oxygen concentration in the air will be 3 times lower than in the lowlands. To stay safely on high mountain peaks, you need to use oxygen masks.

The composition of the air has changed over the years. Evolutionary processes and natural disasters led to changes in, therefore the percentage of oxygen has decreased, necessary for the normal functioning of biological organisms. Several historical stages can be considered:

1. Prehistoric era. At this time, the oxygen concentration in the atmosphere was about 36%.
2. 150 years ago O2 occupied 26% from the total air composition.
3. Currently, the oxygen concentration in the air is just under 21%.

Subsequent development of the surrounding world can lead to further changes in the composition of the air. In the near future, it is unlikely that the O2 concentration could be below 14%, as this would cause disruption of the body's functioning.

What does lack of oxygen lead to?

Low intake is most often observed in stuffy transport, poorly ventilated areas or at altitude . Decreased oxygen levels in the air can cause negative impact on the body. Mechanisms are depleted; the nervous system is most affected. There are several reasons why the body suffers from hypoxia:

1. Blood shortage. Called for carbon monoxide poisoning. This situation reduces the oxygen content of the blood. This is dangerous because the blood stops delivering oxygen to hemoglobin.
2. Circulatory deficiency. It's possible for diabetes, heart failure. In such a situation, blood transport worsens or becomes impossible.
3. Histotoxic factors affecting the body can cause loss of the ability to absorb oxygen. Arises in case of poisoning with poisons or due to exposure to severe...

A number of symptoms indicate that the body requires O2. First of all breathing rate increases. The heart rate also increases. These protective functions are designed to supply oxygen to the lungs and provide them with blood and tissue.

Lack of oxygen causes headaches, increased drowsiness, deterioration in concentration. Isolated cases are not so terrible; they are quite easy to correct. To normalize respiratory failure, the doctor prescribes bronchodilators and other medications. If hypoxia takes severe forms, such as loss of human coordination or even coma, then treatment becomes more complicated.

If symptoms of hypoxia are detected, it is important consult a doctor immediately and do not self-medicate, since the use of a particular drug depends on the causes of the disorder. Helps for mild cases treatment with oxygen masks and pillows, blood hypoxia requires blood transfusion, and correction of circular causes is possible only with surgery on the heart or blood vessels.

The incredible journey of oxygen through our body

Conclusion

Oxygen is the most important air component, without which it is impossible to carry out many processes on Earth. The air composition has changed over tens of thousands of years due to evolutionary processes, but currently the amount of oxygen in the atmosphere has reached at 21%. The quality of the air a person breathes affects his health Therefore, it is necessary to monitor its cleanliness in the room and try to reduce environmental pollution.

Unlike the hot and cold planets of our solar system, conditions exist on planet Earth that allow life in some form. One of the main conditions is the composition of the atmosphere, which gives all living things the opportunity to breathe freely and protects them from the deadly radiation that reigns in space.

What does the atmosphere consist of?

The Earth's atmosphere consists of many gases. Basically which occupies 77%. Gas, without which life on Earth is unthinkable, occupies a much smaller volume; the oxygen content in the air is equal to 21% of the total volume of the atmosphere. The last 2% is a mixture of various gases, including argon, helium, neon, krypton and others.

The Earth's atmosphere rises to a height of 8 thousand km. Air suitable for breathing is found only in the lower layer of the atmosphere, in the troposphere, which reaches 8 km up at the poles, and 16 km above the equator. As altitude increases, the air becomes thinner and the greater the lack of oxygen. To consider what the oxygen content in the air is at different altitudes, let's give an example. At the peak of Everest (height 8848 m), the air holds 3 times less of this gas than above sea level. Therefore, conquerors of high mountain peaks - climbers - can climb to its peak only in oxygen masks.

Oxygen is the main condition for survival on the planet

At the beginning of the Earth's existence, the air that surrounded it did not have this gas in its composition. This was quite suitable for the life of protozoa - single-celled molecules that swam in the ocean. They didn't need oxygen. The process began approximately 2 million years ago, when the first living organisms, as a result of the reaction of photosynthesis, began to release small doses of this gas, obtained as a result of chemical reactions, first into the ocean, then into the atmosphere. Life evolved on the planet and took on a variety of forms, most of which have not survived into modern times. Some organisms eventually adapted to living with the new gas.

They learned to harness its power safely inside a cell, where it acted as a powerhouse to extract energy from food. This way of using oxygen is called breathing, and we do it every second. It was breathing that made it possible for the emergence of more complex organisms and people. Over millions of years, the oxygen content in the air has soared to modern levels - about 21%. The accumulation of this gas in the atmosphere contributed to the creation of the ozone layer at an altitude of 8-30 km from the earth's surface. At the same time, the planet received protection from the harmful effects of ultraviolet rays. The further evolution of life forms on water and land increased rapidly as a result of increased photosynthesis.

Anaerobic life

Although some organisms adapted to the increasing levels of gas released, many of the simplest forms of life that existed on Earth disappeared. Other organisms survived by hiding from oxygen. Some of them today live in the roots of legumes, using nitrogen from the air to build amino acids for plants. The deadly organism botulism is another refugee from oxygen. It easily survives in vacuum-packed canned foods.

What oxygen level is optimal for life?

Prematurely born babies, whose lungs are not yet fully open for breathing, end up in special incubators. In them, the oxygen content in the air is higher by volume, and instead of the usual 21%, its level is set at 30-40%. Babies with severe breathing problems are surrounded by air with 100 percent oxygen levels to prevent damage to the child's brain. Being in such circumstances improves the oxygen regime of tissues that are in a state of hypoxia and normalizes their vital functions. But too much of it in the air is just as dangerous as too little. Excessive oxygen in a child's blood can damage the blood vessels in the eyes and cause vision loss. This shows the duality of gas properties. We need to breathe it in order to live, but its excess can sometimes become poison for the body.

Oxidation process

When oxygen combines with hydrogen or carbon, a reaction called oxidation occurs. This process causes the organic molecules that are the basis of life to disintegrate. In the human body, oxidation occurs as follows. Red blood cells collect oxygen from the lungs and carry it throughout the body. There is a process of destruction of the molecules of the food we eat. This process releases energy, water and leaves behind carbon dioxide. The latter is excreted by blood cells back into the lungs, and we exhale it into the air. A person may suffocate if they are prevented from breathing for more than 5 minutes.

Breath

Let's consider the oxygen content in the inhaled air. Atmospheric air that enters the lungs from outside during inhalation is called inhaled air, and air that comes out through the respiratory system during exhalation is called exhaled air.

It is a mixture of the air that filled the alveoli with that in the respiratory tract. The chemical composition of the air that a healthy person inhales and exhales under natural conditions practically does not change and is expressed in the following numbers.

Oxygen is the main component of air for life. Changes in the amount of this gas in the atmosphere are small. If the oxygen content in the air near the sea reaches up to 20.99%, then even in the very polluted air of industrial cities its level does not fall below 20.5%. Such changes do not reveal effects on the human body. Physiological disturbances appear when the percentage of oxygen in the air drops to 16-17%. In this case, there is an obvious one that leads to a sharp decline in vital activity, and when the oxygen content in the air is 7-8%, death is possible.

Atmosphere in different eras

The composition of the atmosphere has always influenced evolution. At different geological times, due to natural disasters, rises or falls in oxygen levels were observed, and this entailed changes in the biosystem. About 300 million years ago, its content in the atmosphere rose to 35%, and the planet was colonized by insects of gigantic size. The greatest extinction of living things in Earth's history occurred about 250 million years ago. During it, more than 90% of the inhabitants of the ocean and 75% of the inhabitants of the land died. One version of the mass extinction says that the culprit was low oxygen levels in the air. The amount of this gas dropped to 12%, and this is in the lower layer of the atmosphere up to an altitude of 5300 meters. In our era, the oxygen content in atmospheric air reaches 20.9%, which is 0.7% lower than 800 thousand years ago. These figures were confirmed by scientists from Princeton University, who examined samples of Greenland and Atlantic ice that formed at that time. The frozen water preserved air bubbles, and this fact helps calculate the level of oxygen in the atmosphere.

What determines its level in the air?

Its active absorption from the atmosphere can be caused by the movement of glaciers. As they move away, they reveal gigantic areas of organic layers that consume oxygen. Another reason may be the cooling of the waters of the World Ocean: its bacteria at lower temperatures absorb oxygen more actively. Researchers argue that the industrial leap and, with it, the burning of huge amounts of fuel do not have a particular impact. The world's oceans have been cooling for 15 million years, and the amount of vital nutrients in the atmosphere has decreased regardless of human impact. There are probably some natural processes taking place on Earth that lead to oxygen consumption being higher than its production.

Human impact on the composition of the atmosphere

Let's talk about the human influence on the composition of air. The level we have today is ideal for living beings; the oxygen content in the air is 21%. The balance of it and other gases is determined by the life cycle in nature: animals exhale carbon dioxide, plants use it and release oxygen.

But there is no guarantee that this level will always be constant. The amount of carbon dioxide released into the atmosphere is increasing. This is due to humankind's use of fuel. And, as you know, it was formed from fossils of organic origin and carbon dioxide enters the air. Meanwhile, the largest plants on our planet, trees, are being destroyed at an increasing rate. In a minute, kilometers of forest disappear. This means that some of the oxygen in the air is gradually falling and scientists are already sounding the alarm. The earth's atmosphere is not a limitless storehouse and oxygen does not enter it from the outside. It was constantly being developed along with the development of the Earth. We must always remember that this gas is produced by vegetation during the process of photosynthesis through the consumption of carbon dioxide. And any significant decrease in vegetation in the form of destruction of forests inevitably reduces the entry of oxygen into the atmosphere, thereby disturbing its balance.

Atmospheric air, which a person inhales while outdoors (or in well-ventilated rooms), contains 20.94% oxygen, 0.03% carbon dioxide, 79.03% nitrogen. In enclosed spaces filled with people, the percentage of carbon dioxide in the air may be slightly higher.

Exhaled air contains on average 16.3% oxygen, 4% carbon dioxide, 79.7% nitrogen (these figures are based on dry air, i.e. minus water vapor, which is always saturated in exhaled air).

Composition of exhaled air very fickle; it depends on the intensity of the body's metabolism and the volume of pulmonary ventilation. It is worth making several deep breathing movements or, on the contrary, holding your breath so that the composition of the exhaled air changes.

Nitrogen does not participate in gas exchange, but the percentage of nitrogen in visible air is several tenths of a percent higher than in inhaled air. The fact is that the volume of exhaled air is slightly less than the volume of inhaled air, and therefore the same amount of nitrogen, distributed in a smaller volume, gives a higher percentage. The smaller volume of exhaled air compared to the volume of inhaled air is explained by the fact that slightly less carbon dioxide is released than oxygen is absorbed (part of the absorbed oxygen is used in the body to circulate compounds that are excreted from the body in urine and sweat).

Alveolar air differs from exhaled breath by a larger percentage of non-acid and a smaller percentage of oxygen. On average, the composition of alveolar air is as follows: oxygen 14.2-14.0%, carbon dioxide 5.5-5.7%, nitrogen about 80%.

Definition alveolar air composition important for understanding the mechanism of gas exchange in the lungs. Holden proposed a simple method for determining the composition of alveolar air. After a normal inhalation, the subject exhales as deeply as possible through a tube 1-1.2 m long and 25 mm in diameter. The first portions of exhaled air leaving through the tube contain air from the harmful space; the last portions remaining in the tube contain alveolar air. For analysis, air is taken into the gas receiver from the part of the tube that is closest to the mouth.

The composition of alveolar air differs somewhat depending on whether the air sample is taken for analysis at the height of inhalation or exhalation. If you exhale quickly, briefly, and incompletely at the end of a normal inhalation, the air sample will reflect the composition of the alveolar air after the lungs have been filled with respiratory air, i.e., during inhalation. If you exhale deeply after a normal exhalation, the sample will reflect the composition of the alveolar air during exhalation. It is clear that in the first case the percentage of carbon dioxide will be slightly less, and the percentage of oxygen will be slightly higher than in the second. This can be seen from the results of Holden's experiments, who found that the percentage of carbon dioxide in the alveolar air at the end of inspiration averages 5.54, and at the end of exhalation - 5.72.

Thus, there is a relatively small difference in the content of carbon dioxide in the alveolar air during inhalation and exhalation: only 0.2-0.3%. This is largely explained by the fact that during normal breathing, as mentioned above, only 1/7 of the volume of air in the pulmonary alveoli is renewed. The relative constancy of the composition of alveolar air is of great physiological importance, as will be clarified below.

Gas exchange in the lungs - exchange of gases by diffusion between alveolar air and blood. This set of processes occurs in the alveoli and the elements of the transition zone of the respiratory tract closest to them: bronchioles, alveolar sacs.

The composition of atmospheric air includes almost 21% oxygen, about 79% nitrogen, approximately 0.03% carbon dioxide, a small amount of water vapor and inert gases. This is the air we breathe, and it is called inhaled. The air we exhale is called exhaled. Its composition is different compared to inhaled air: 16.3% oxygen, about 79% nitrogen, about 4% carbon dioxide, etc. The different content of oxygen and carbon dioxide in inhaled and exhaled air is explained by the exchange of gases in the lungs.

Gas exchange in the lungs occurs when diffusion gases through the walls of the alveoli and blood capillaries due to the difference between partial pressure O2 and CO2 in alveolar air and blood.

Partial pressure of O2 and CO2 in alveolar air and blood

For rapid gas exchange in the lungs, the difference between the partial pressure of gases in the alveolar air and their tension in the blood is about 70 mm Hg for O2. St, for CO2 - about 7 mm Hg. Art.

Transportation of gases- transfer of O2 by blood from the lungs to the cells and CO2 from the cells to the lungs.

This stage is carried out by the circulatory system, and the vehicle is blood. The solubility coefficients of respiratory gases are different (O2 - 0.022, CO2 - 0.53), therefore they are transported differently. Oxygen transport is provided by the main oxygen carrier - blood hemoglobin, and a very small part of 02 is dissolved in plasma. A hemoglobin molecule contains one globin molecule and 4 heme molecules, each of which has one divalent iron atom, binds one oxygen molecule: Hb + 4O2 = HbO8. The addition of oxygen to hemoglobin to form oxyhemoglobin occurs at a partial pressure of 70-73 mmHg. Art. One gram of hemoglobin can add 1.34 ml. oxygen. For carbon dioxide transport There are three ways of transferring carbon dioxide in the blood: 1) in a dissolved state - 5%; 2) in the form of carbhemoglobin - 10-20%; 3) in the form of carbonates (mainly sodium and potassium bicarbonates) - 85%.

Gas exchange in tissues - exchange of gases by diffusion between blood and tissues in capillaries. This stage is caused by the tension of gases in the blood and tissues (for O2 - about 70 mm Hg, for CO2 - about 7 mm Hg) and is also carried out due to diffusion. In tissues, the voltage difference is maintained by a continuous process of biological oxidation.

Tissue respiration- consumption of 02 by cells and their release of CO2. This is a multi-stage enzymatic process of using oxygen by cells to oxidize organic compounds to form CO2 and H2O and produce energy for life. In cells, oxygen is delivered to the mitochondria, where the oxidation of organic compounds and the synthesis of ATP occurs. Cellular respiration is studied in more detail by biochemistry.

Basic breathing indicators

There are several indicators that characterize the functional state of the lungs; they are measured using a special device called a spirometer. Basically, vital capacity of the lungs (VC) is determined. Vital capacity of the lungs- this is the largest volume of air that a person can exhale after taking the deepest breath. This indicator consists of the following volumes:

1) tidal volume (BEFORE ) - the volume of air that a person inhales and exhales during quiet breathing (about 500 ml)

2) additional volume (TRP), or inspiratory reserve volume - the maximum volume of air that can be inhaled after the end of a quiet breath (about 1500-2000 ml)

3) expiratory reserve volume (RO ) - the maximum volume of air exhaled after a quiet exhalation (1000-1500 ml)

vital capacity = TO(0.5 l) + TRP(1.5-2 l) + RO(1.5 l) = 3.5-4 l

Normally, vital capacity is about 3/4 of the total lung capacity and characterizes the maximum volume within which a person can change the depth of his breathing. VC depends on age(decreases with age, which is explained by a decrease in the elasticity of the lungs), gender (V women - 3-3.5 l, men - 3.5-4.8 l), physical development(in physically trained people - 6 -7 l), body position(slightly more in a vertical position) growth(in young people this dependence is expressed by the formula: vital capacity = 2.5 × height in meters), etc.

Together with residual volume, that is, the volume of air that remains in the lungs after deep exhalation, vital capacity forms total lung capacity(GREEN).