External indicators of the respiratory system. Vital and total lung capacity. Composition of inhaled, exhaled and alveolar air. Exchange of gases between alveolar air and blood. (Gas exchange in the lungs)

External respiration - gas exchange between the body and its surroundings atmospheric air. External respiration includes the exchange of gases between atmospheric and alveolar air, as well as gas exchange between the blood of the pulmonary capillaries and the alveolar air.

Vital capacity (VC) - the volume of air that a person can exhale with the deepest possible slow exhalation made after a maximum inhalation.

The value of the vital capacity of human lungs is 3-6 liters. Recently, in connection with the introduction of pneumotachographic technology, the so-called forced vital capacity (FVC) is increasingly being determined. When determining FVC, the subject must, after the deepest possible breath, make the deepest forced exhalation. In this case, the exhalation should be carried out with an effort aimed at achieving the maximum volumetric velocity of the exhaled air flow throughout the entire exhalation. Computer analysis of such a forced expiration allows you to calculate dozens of indicators of external respiration. The composition of alveolar air is significantly different from the composition of atmospheric, inhaled air. It has less oxygen (14.2%) and a large amount of carbon dioxide (5.2%).

Why is there more oxygen in exhaled air than in alveolar air? This is explained by the fact that during exhalation, the air that is in the respiratory organs, in the airways, is mixed with the alveolar air.

The whole process is under the control of the brain. In the medulla oblongata there is a special center for the regulation of respiration. It reacts to the presence of carbon dioxide in the blood. As soon as it becomes smaller, the center sends a signal to the diaphragm along the nerve pathways. There is a process of its contraction, and inhalation occurs. If the respiratory center is damaged, the patient's lungs are ventilated artificially. Oxygen entering the alveoli penetrates the walls of the capillaries. This is because the blood and air contained in the alveoli have different pressures. Venous blood has less pressure than alveolar air. Therefore, oxygen from the alveoli rushes into the capillaries. The pressure of carbon dioxide is less in the alveoli than in the blood. For this reason, carbon dioxide is directed from the venous blood into the lumen of the alveoli.

In the blood there are special cells - erythrocytes containing the protein hemoglobin. Oxygen attaches to hemoglobin and travels in this form throughout the body. Blood enriched with oxygen is called arterial.

The blood is then carried to the heart. The heart, another tireless worker of ours, transports oxygen-enriched blood to tissue cells. And then along the "brooks" blood, along with oxygen, is delivered to all cells of the body.

Mechanism of gas exchange between blood and tissues. Binding and transport of oxygen in the blood. The oxygen capacity of the blood. Binding and transport of carbon dioxide in the blood. The role of erythrocytes and hemoglobin in this process. Importance of the enzyme carbonic anhydrase.

The binding of oxygen to hemoglobin. The transport of O2 from the alveoli to the blood and the transport of CO2 from the blood to the alveoli is carried out by diffusion. The transport of gases is carried out in a physically dissolved and chemically bound form. physical processes, i.e., the dissolution of the gas, cannot meet the demands of the organism in O2. It is estimated that physically dissolved O2 can maintain normal body O2 consumption (250 ml/min) if the cardiac output is approximately 83 L/min at rest. The most optimal mechanism is the transport of O2 in a chemically bound form. Hemoglobin (Hb) is able to selectively bind O2 and form oxyhemoglobin (HbO2) in the area of ​​high O2 concentration in the lungs and release molecular O2 in the area of ​​low O2 content in tissues. At the same time, the properties of hemoglobin do not change and it can perform its function for a long time.

Hemoglobin carries O2 from the lungs to the tissues. This function depends on two properties of hemoglobin: 1) the ability to change from a reduced form, which is called deoxyhemoglobin, to an oxidized one (Hb + O2HbO2) at a high rate (half-time of 0.01 s or less) with normal PO2b alveolar air; 2) the ability to release O2 in tissues (HbO2 Hb + O2) depending on the metabolic needs of body cells.

oxygen capacity of the blood

The amount of oxygen that hemoglobin can bind when it is completely saturated is called the oxygen capacity of the blood (KEK)

1 gram of Hb binds 1.39 ml of O2

Carbon dioxide is transported in the following ways:

Dissolved in blood plasma - about 25 ml / l.

Associated with hemoglobin (carbhemoglobin) - 45 ml / l.

in the form of salts carbonic acid- potassium and sodium bucarbonates in blood plasma - 510 ml / l.

Thus, at rest, the blood transports 580 ml of carbon dioxide per liter. So, the main form of CO2 transport is plasma bicarbonates, which are formed due to the active course of the carbonic anhydrase reaction.

Erythrocytes contain the enzyme carbonic anhydrase (CG), which catalyzes the interaction of carbon dioxide with water to form carbonic acid, decomposes to form a bicarbonate ion and a proton. Bicarbonate inside the erythrocyte interacts with potassium ions released from the potassium salt of hemoglobin during the restoration of the latter. So potassium bicarbonate is formed inside the erythrocyte. But bicarbonate ions are formed in a significant concentration and therefore, along the concentration gradient (in exchange for chloride ions) enter the blood plasma. This is how sodium bicarbonate is formed in the plasma. The proton formed during the dissociation of carbonic acid reacts with hemoglobin to form the weak acid HHb.

In the capillaries of the lungs, these processes go to reverse direction. Carbonic acid is formed from hydrogen ions and bicarbonate ions, which quickly decomposes into carbon dioxide and water. Carbon dioxide is removed to the outside.

So, the role of erythrocytes in the transport of carbon dioxide is as follows:

the formation of salts of carbonic acid;

formation of carbhemoglobin.

The diffusion of gases in tissues obeys general laws (the volume of diffusion is directly proportional to the area of ​​diffusion, the gradient of gas tension in the blood and tissues). The area of ​​diffusion increases, and the thickness of the diffuse layer decreases with an increase in the number of functioning capillaries, which occurs with an increase in the level of functional activity of tissues. Under the same conditions, the gas tension gradient increases due to a decrease in Po2 in actively working organs and an increase in Pco2 (the gas composition of arterial blood, as well as alveolar air, remains unchanged!). All these changes in actively working tissues contribute to an increase in the volume of diffusion of O2 and CO2 in them. The consumption of O2 (CO2) according to the spirogram is determined by the change (shift) of the curve upwards per unit of time (1 minute).

Essence of breath. External respiration. Mechanism of inhalation and exhalation. Types and frequency of respiration in animals different types. Importance of the upper respiratory tract

Respiration is a complex continuous biological process, as a result of which the gas composition of the internal environment of the body is regenerated, which provides all cells and tissues with oxygen.

Meaning: oxygen entering the cell is involved in the reaction of oxidative phosphorylation of the food. and as a result, the hidden ATP molecule is released.

Links: 1) external (pulmonary)

2) transport of gases by blood

3) internal (tissue) respiration.

External respiration is carried out in 2 stages: 1) gas exchange between atm. air and alveolar air; 2) gas exchange between the alveolar air and the blood of the capillaries of the pulmonary circulation.

Oxygen along the concentration gradient is directed from the atm. air to the alveolar, from there into the blood of the small capillaries.

Carbon dioxide is directed along the concentration gradient from the blood of the capillaries of the small cr.cr to the alveolar air, from there to the atmospheric air.

Inhalation mechanism. Inhalation is an active process, because it is caused by the flow of nerve impulses from their respiratory center to the inspiratory muscles. At this time, the inspiratory phase of neuronal activity is noted in the prod. brain, it is due to the excitation of early inspiratory neurons, complete, late inspiratory neurons. Part of the axons of complete and late inspiratory neurons are sent to the spinal cord, excitation of motor neurons innervating the inspiratory muscles. The inspiratory muscles contract and the volume of the cell increases in 3 main directions.

Due to the contraction of the diaphragm, its dome flattens, the volume of the gr.cell increases in the vertical direction. By reducing the intercostal And the intercartilage muscles, the sternum moves a little forward, and the ribs occupy a more horizontal position - the volume of the gr. cell increases in the anterior-posterior and transverse (costal) direction.

The lungs passively follow the gr.cell (stretch) - intrapulmonary pressure becomes slightly lower than atmospheric pressure - air is sucked into the lungs.

exhalation mechanism. 1h-passive exhalation (passive expiration)

2h - active exhalation.

Passive expiration is due to the absence of nerve impulses from neurons to the inspiratory muscles. At this time, a post-inspiratory phase is noted in the pro-brain, it is due to the excitation of post-inspiratory neurons - as a result, the activity of all inspiratory neurons is inhibited - nerve impulses do not come from the pro-brain to the spinal cord. Motor neurons of the spinal cord are not activated - impulses from them do not go to the inspiratory muscles - inspiratory muscles relax - volume chest decreases in 3 main directions. Due to the relaxation of the diaphragm - the dome rises - the volume of the gr. cell decreases in the vertical direction. Due to the relaxation of the external oblique intercostals and intercartilaginous muscles, the sternum returns back - the ribs take a more vertical position - the volume of the gr. cell decreases in the anterior-posterior and costal directions. The chest has decreased - the pressure in the lungs has become higher than atmospheric pressure - the air is squeezed out of the lungs.

Active exhalation. An expiratory phase is noted in the prod.brain, it is due to the excitation of expiratory neurons. All axons of the expiratory neurons from the prod.brain enter the spinal cord and excite the motor neurons that innervate the expiratory muscles. The expiratory muscles contract and additionally reduce the volume of the gr.cell, thereby continuing to exhale.

There are three types of breathing:

thoracic, or costal - it mainly takes part in the muscles of the chest (mainly in women);

abdominal, or diaphragmatic - respiratory movements are performed mainly by the abdominal muscles and the diaphragm (in men);

· thoracic, or mixed - respiratory movements are carried out by the pectoral and abdominal muscles (in all farm animals).

The frequency of respiratory movements depends on the level of metabolism in the body, on temperature environment, age of the animal, atmospheric pressure and some other factors.

In highly productive cows, the metabolism is higher, so the respiratory rate is 30 per 1 min, while in cows with an average productivity it is 15–20. In calves at the age of one year, at an air temperature of 15 0 C, the respiratory rate is 20–24, at a temperature of 30–35 0 C - 50–60, and at a temperature of 38–40 0 C – 70–75.

Young animals breathe faster than adults. In calves at birth, the respiratory rate reaches 60–65, and by the year it decreases to 20–22.

The upper respiratory tract plays a more important role in the life of the body than it was previously thought.

This part of the respiratory system is important for warming, moistening and purifying the inhaled air, for speech function, but its significance is not limited to this. The upper respiratory tract has very sensitive receptor zones, the excitation of which in a reflex way affects various physiological systems. Conversely, the mucous membrane of the nose (and larynx) easily reacts to reflex influences. For example, when the legs are cooled, a vasomotor reaction of the nasal mucosa occurs.

The evolution of breath.

1) Diffuse breathing is the process of equalizing the concentration of oxygen inside the body and in its environment. Oxygen penetrates through the cell membrane in unicellular organisms.

2) Skin respiration- this is the exchange of gases through the skin in lower worms, in vertebrates (fish, amphibians), which have special respiratory organs.

gill breathing

PIRATE GILLS(skin outgrowths on both sides of the body) appear in marine annelids, aquatic arthropods, and mollusks in the mantle cavity.

GILLS- respiratory organs of vertebrates, formed as an invagination of the digestive tube.

In the lancelet, gill slits pierce the pharynx and open into the peribranchial cavity with frequent changes of water.

Fish have gills made from gill arches with gill filaments pierced by capillaries. The water swallowed by the fish enters the oral cavity, passes through the gill filaments to the outside, washes them and supplies the blood with oxygen.

4) Tracheal and pulmonary breathing- more efficient, since oxygen is absorbed immediately from the air, and not from the water. It is typical for terrestrial mollusks (sac-like lungs), arachnids, insects, amphibians, reptiles, birds, mammals.

arachnids have lung sacs (scorpions), tracheas (ticks), and spiders have both.

INSECTS have tracheas - the respiratory organs of terrestrial arthropods - a system of air tubes that open with breathing holes (stigmas) on the lateral surfaces of the chest and abdomen.

AMPHIBIANS have 2/3 cutaneous respiration and 1/3 pulmonary. Airways appear for the first time: larynx, trachea, bronchial rudiments; light - smooth-walled bags.

REPTILES have developed airways; the lungs are cellular, there is no skin respiration.

BIRDS have developed airways, light spongy. Part of the bronchi branches outside the lungs and forms - air sacs.

Air bags- air cavities connected to the respiratory system, 10 times the volume of the lungs, which serve to enhance air exchange in flight, do not perform the function of gas exchange. Breathing at rest is carried out by changing the volume of the chest.

Breathing in flight

1. When the wings are raised, air is sucked through the nostrils into the lungs and posterior air sacs (in the lungs I gas exchange);

Anterior air sacs ← light - posterior air sacs

2. When the wings are lowered, the air sacs are compressed, and air from the rear air sacs enters the lungs (in the lungs II gas exchange).

Front air bags - ← light rear air bags

double breath is the exchange of gases in the lungs during inhalation and exhalation.

MAMMALS- gas exchange almost entirely in the lungs (through the skin and alimentary canal -2%)

airways: nasal cavity → nasopharynx → pharynx → larynx → trachea → bronchi (bronchi branch into bronchioles, alveolar ducts and end with alveoli - pulmonary vesicles). The lungs are spongy and consist of alveoli surrounded by capillaries. The respiratory surface is increased by 50-100 times compared to the body surface. The type of breathing is alveolar. The diaphragm that separates the chest cavity from the abdominal cavity, as well as the intercostal muscles, provide ventilation to the lungs. Complete separation of the oral and nasal cavities. Mammals can breathe and chew at the same time.

Oxygen consumption by respiration is a phenomenon so universal that it is often overlooked. Almost all animals have one or another mechanism by which fresh air enters the body, and the used air is removed outside.

Respiration is a set of physiological processes that ensure the supply of oxygen to the body and the removal of carbon dioxide, i.e. maintaining the relative constancy of carbon dioxide and oxygen in the alveolar air, blood and tissues.
Respiration includes the following physiological processes:

Exchange of gases between external environment and a mixture of gases in the alveoli;
gas exchange between alveolar air and blood gases;
transport of gases by blood;
exchange of gases between blood and tissues;
the use of oxygen by tissues and the formation of carbon dioxide.

The exchange of gases between the external environment and the mixture of gases in the alveoli. The process of gas exchange between the external environment and the mixture of gases in the alveoli is called pulmonary ventilation. The exchange of gases is ensured by respiratory movements - acts of inhalation and exhalation. When inhaling, there is an increase in the volume of the chest, a decrease in pressure in the pleural cavity and, as a result, the flow of air from the external environment into the lungs. When exhaling, the volume of the chest decreases, the air pressure in the lungs increases, and as a result, the alveolar air is forced out of the lungs.

The turtle comes up to breathe. Photo: Ibrahim Iujaz

Mechanism of inhalation and exhalation. Inhalation and exhalation occur because the volume of the chest cavity changes, either increasing or decreasing. Lungs - a spongy mass consisting of alveoli, does not contain muscle tissue. They cannot shrink. Respiratory movements are performed with the help of intercostal and other respiratory muscles and the diaphragm.
When inhaling, the external oblique intercostal muscles and other muscles of the chest and shoulder girdle simultaneously contract, which ensures the raising or abduction of the ribs, as well as the diaphragm, which shifts towards the abdominal cavity. As a result, the volume of the chest increases, the pressure in the pleural cavity and in the lungs decreases, and, as a result, air from the environment enters the lungs. Inhaled air contains 20.97% oxygen, 0.03% carbon dioxide and 79% nitrogen.
During exhalation, the expiratory muscles simultaneously contract, which ensures the return of the ribs to the position before inhalation. The diaphragm returns to its pre-inhalation position. This reduces the volume of the chest, increases the pressure in the pleural cavity and in the lungs, and part of the alveolar air is forced out. Exhaled air contains 16% oxygen, 4% carbon dioxide, 79% nitrogen.

In animals, three types of breathing are distinguished: costal, or chest, - when inhaling, the abduction of the ribs to the sides and forward predominates; diaphragmatic, or abdominal, - inhalation occurs mainly due to the contraction of the diaphragm; costabdominal - inhalation due to contraction of the intercostal muscles, diaphragm and abdominal muscles.

Respiration is becoming a problem of paramount importance in aquatic mammals. Their respiratory systems have amazing adaptations that allow these animals to dive on great depths and stay underwater longer than other mammals can. The muskrat and elephant seal have been reported to be able to stay submerged for 12 minutes, while the bottlenose whale can submerge for 120 minutes.

Breathing indicators

The activity of the respiratory system is characterized by certain external indicators.
The frequency of respiratory movements in 1 min. For a horse it is 8...16, for cattle - 10...30, for sheep - 10...20, for a pig - 8...18, for a rabbit - 15...30, for a dog - 10... 30, cats - 20 ... 30, birds - 18 ... 34, and a person has 12 ... 18 movements per minute. Four primary lung volumes: inspiratory, inspiratory reserve, expiratory reserve, residual volume. Accordingly, cattle and horses have approximately 5 ... 6 liters, 12 ... 18, 10 ... 12, 10 ... 12 liters. Four lung capacities: general, vital, inhalation, functional residual. minute volume. In cattle - 21 ... 30 liters. and horses - 40 ... 60 liters. The content of oxygen and carbon dioxide in the exhaled air. The tension of oxygen and carbon dioxide in the blood.

Breathing regulation

Under the regulation of respiration is understood the maintenance of the optimal content of oxygen and carbon dioxide in the alveolar air and in the blood by changing the frequency and depth of respiratory movements. The frequency and depth of respiratory movements are determined by the rhythm and force of impulse generation in the respiratory center located in the medulla oblongata, depending on its excitability. Excitability is determined by the tension of carbon dioxide in the blood and the flow of impulses from the receptor zones of blood vessels, respiratory tract, and muscles.
Regulation of respiratory rate. The frequency of respiratory movements is regulated by the respiratory center, which includes the centers of inhalation, exhalation and pneumotaxis; the inspiratory center plays a major role. In the center of inhalation, impulses are born rhythmically in bursts per unit time, determining the frequency of breathing. Impulses from the center of inhalation arrive at the inhalatory muscles and the diaphragm, causing a breath of such duration and depth that corresponds to the prevailing conditions and is characterized by a certain volume of air entering the lungs, the force of contraction of the inhalatory muscles. The number of impulses born in the center of inhalation per unit time depends on its excitability: the higher the excitability, the more often impulses are born, and hence the more frequent respiratory movements.
Regulation of the change of inhalation with exhalation, exhalation with inhalation. The regulation of the change of inhalation by exhalation, exhalation by inhalation is carried out reflexively. The excitation that occurs in the center of inspiration provides the act of inspiration, which is accompanied by stretching of the lungs and excitation of the mechanoreceptors of the pulmonary alveoli. Impulses from the receptors along the afferent fibers of the vagus nerves arrive at the exhalation center and excite its neurons. At the same time, directly through the center of pneumotaxis, the inspiratory center also excites the exhalation center. The neurons of the exhalation center, being excited, according to the laws of reciprocal relations, inhibit the activity of the neurons of the inhalation center, and the inhalation stops. The exhalation center sends information to the expiratory muscles, causes them to contract, and the act of exhalation is carried out. So there is an alternation of inhalation and exhalation. The number of bursts of impulses coming from the center of inspiration per unit time, and the strength of these bursts depend on the excitability of the neurons of the respiratory center, the specifics of metabolism, the special sensitivity of neurons to their surrounding humoral environment, to the incoming information from the chemoreceptors of blood vessels, respiratory tract and lungs, muscles and digestive apparatus. An excess of carbon dioxide in the blood and alveolar air and a lack of oxygen, an increase in oxygen consumption and the formation of carbon dioxide in muscles and other organs, with an increase in their activity, cause the following reactions: increased excitability of the respiratory center, an increase in the frequency of impulses in the center of inspiration, increased consequently, the restoration of the optimal content of oxygen and carbon dioxide in the alveolar air and blood. Conversely, an excess of oxygen in the blood and alveolar air leads to a decrease in respiratory movements and a decrease in lung ventilation. In connection with adaptation to changing conditions, the number of respiratory movements in animals can increase by 4 ... 5 times, the respiratory volume of air by 4 ... 8 times, and the minute respiratory volume by 10 ...

Features of the respiratory system in birds

Unlike mammals, the respiratory system in birds has structural and functional features. Structural features. Nasal openings in birds are located at the base of the beak; nasal air passages are short.

Under the external nostril there is a scaly fixed nasal valve, and around the nostrils there is a feather-corolla that protects the nasal passages from dust and water. In waterfowl, the nostrils are surrounded by a waxy skin.
Birds lack an epiglottis. The function of the epiglottis is performed by the back of the tongue. There are two larynxes - upper and lower. There are no vocal cords in the upper larynx. The lower larynx is located at the end of the trachea at the point of its branching into the bronchi and serves as a sound resonator. It has special membranes and special muscles. Air passing through the lower larynx causes the membrane to vibrate, which leads to the appearance of sounds of different heights. These sounds are amplified in the resonator. Chickens are capable of emitting 25 various sounds, each of which reflects a particular emotional state.
The trachea in birds is long and has up to 200 tracheal rings. Behind the lower larynx, the trachea divides into two main bronchi, which enter the right and left lungs. The bronchi pass through the lungs and expand into the abdominal air sacs. Within each lung, the bronchi give rise to secondary bronchi, which run in two directions - to the ventral surface of the lungs and to the dorsal. Ecto - and endobronchus are divided into a large number of small tubes - parabronchi and bronchioles, and the latter are already passing into many alveoli. Parabronchi, bronchioles and alveoli form the respiratory parenchyma of the lungs - the "spider web", where gas exchange takes place.

The lungs are elongated, maloelastic, pressed between the ribs and firmly connected to them. Since they are attached to the dorsal chest wall, they expand in a way that the lungs of mammals that are free in the chest cannot. The weight of the lungs in chickens is approximately 30 g.

Birds have the rudiments of two lobes of the diaphragm: pulmonary and thoracic. The diaphragm is attached to the spinal column with the help of a tendon and small muscle fibers to the ribs. It is reduced in connection with inspiration, but its role in the mechanism of inhalation and exhalation is insignificant. In chickens, the abdominal muscles take a great part in the act of inhalation and exhalation.
The breathing of birds is associated with the activity of large air sacs, which are combined with lungs and pneumatic bones.
Birds have 9 main air sacs - 4 paired, located symmetrically on both sides, and one unpaired. The largest are the abdominal air sacs. In addition to these air sacs, there are also air sacs located near the tail - posterior trunk, or intermediate.

Air sacs are thin-walled formations filled with air; their mucous membrane is lined with ciliated epithelium. From some air sacs there are processes to the bones that have air cavities. There is a network of capillaries in the wall of the air sacs.
The air sacs perform a number of roles:

1) participate in gas exchange;
2) lighten body weight;
3) ensure the normal position of the body during flight;
4) contribute to the cooling of the body during flight;
5) serve as an air reservoir;
6) act as a shock absorber for internal organs.

Pneumatic bones in birds are the cervical and dorsal bones, tail vertebrae, humerus, thoracic and sacral bones, vertebral ends of the ribs.

The lung capacity of chickens is 13 cm 3, ducks - 20 cm 3, the total capacity of the lungs and air sacs, respectively, is 160 ... 170 cm 3, 315 cm 3, 12 ... 15% of it is the respiratory volume of air.
functional features. Birds, like insects, exhale when the respiratory muscles contract; in mammals, the opposite is true - when the muscles of the inhalers contract, they take a breath.
Birds have relatively frequent breathing: chickens - 18 ... 25 times per minute, ducks - 20 ... 40, geese - 20 ... 40, turkeys - 15 ... 20 times per minute. The respiratory system in birds has great functionality - under load, the number of respiratory movements can increase: in agricultural birds up to 200 times per minute.

The air entering the body during inhalation fills the lungs and air sacs. Airspaces are actually spare containers for fresh air. In the air sacs, due to the small number of blood vessels, oxygen uptake is negligible; in general, the air in the bags is saturated with oxygen.
In birds, the so-called double gas exchange occurs in the lung tissue, which occurs during inhalation and exhalation. Due to this, inhalation and exhalation are accompanied by the extraction of oxygen from the air and the release of carbon dioxide.
In general, breathing in birds occurs as follows.

The muscles of the chest wall contract so that the sternum is raised. This means that the chest cavity becomes smaller and the lungs contract to the point where carbon dioxide-laden air is forced out of the breathing spaces.
As air exits the lungs during exhalation, new air from the air spaces passes forward through the lungs. During exhalation, air passes predominantly through the ventral bronchi.

After the muscles of the chest have contracted, the exhalation has taken place and all the used air has been removed, the muscles relax, the sternum moves down, the chest cavity expands, becomes large, a difference in air pressure is created between the external environment and the lungs, and inhalation is carried out. It is accompanied by the movement of air mainly through the dorsal bronchi.
The air sacs are resilient, like lungs, so when the chest cavity expands, they also expand. The elasticity of the air sacs and lungs allows air to enter the respiratory system.

Since muscle relaxation causes air to enter the lungs from the environment, the lungs of a dead bird, whose respiratory muscles are normally relaxed, will be swollen, or filled with air. In dead mammals, they are dormant.
Some diving birds can remain submerged for a significant amount of time, during which time air circulates between the lungs and air sacs, and most of the oxygen passes into the blood, maintaining an optimal oxygen concentration.
Birds are very sensitive to carbon dioxide and respond differently to increases in its content in the air. The maximum allowable increase is not more than 0.2%. Exceeding this level causes inhibition of respiration, which is accompanied by hypoxia - a decrease in the oxygen content in the blood, while the productivity and natural resistance of birds decreases. In flight, breathing slows down due to improved ventilation of the lungs even at an altitude of 3000 ... 400 m: in conditions of low oxygen content, birds provide themselves with oxygen with rare breathing. On the ground, birds die under these conditions.

"Animals of the Baltic Sea" - Toxins from water pollution enter the food of mammals. Common seal. Lives in seas with a water temperature of at least 15 degrees. However, poaching occasionally occurs. Harbour porpoise. The animal is currently on the verge of extinction. It is also dangerous for animals to get caught in fishing gear. The white-sided dolphin is the most gregarious, frisky and fast cetacean mammal. The young generation is born in autumn - at the beginning of winter.

"Wintering Birds of Russia" - Expand your horizons. Why do birds fly south. Bullfinch. Wintering and migratory birds of our area. Martin. Nuthatch. Help. Crow. Heron. Literature work. Waxwing. Woodpecker. Warming methods. Migratory and wintering birds. Wintering birds. Nightingale. Sparrow. Starling. Frosts. The amount of food available. Wild ducks. Crane. Fluff appears. Tits. Birds.

"The journey of a drop of water" - Drops of water from the chilled glass began to fall down. Experiments on the study of the properties of water. Water may also be in gaseous state. Water in nature exists in three states. Fog, ice, stream - it's all water. Acquaintance with the transformation of water in nature. Water also travels. Droplet travel. The water cycle in nature. Water passes from liquid state into solid.

"Dogs in space" - The purpose of the project. Gypsy did not fly into space anymore. The dog will be alive, the astronaut will be alive. Veterans of space flights. The dogs have done their job. Road for Laika. Dog Kozyavka on pre-flight preparation. 9 dog flights. Bee and Mushka - died in orbit. A squad of space mongrels. First orbital flight - Laika. Dog suits. Kozyavka is a spaceflight veteran. Experiments to launch rockets with dogs at a height of up to 100 kilometers.

"Integrated lesson on the world around" - What is the support of the human body. The boundary of the visible space. How many types of odors can a person recognize. Tasks that stimulate cognitive interest. Ravine. Missing letters. The world. Kerosene. How many muscles in the human body. property of coal. The largest desert on earth. How is the word "tundra" translated? ancient geographic Maps. The lowest part of the mountain. The mountains.

"Wind" - Characteristics of the wind. Warm air takes up more space than cold air. Creative task. Air compresses as it cools. Warm air movement. Warm air expands when heated. Wind. How to prove that warm air takes up more space than cold air. Cooler, heavier air will flow in. Aivazovsky I.K. Storm. Now it circles through the forest, then it whistles in the field. Vane. Correct answer.

The set of processes that ensure the consumption of O 2 and the release of CO 2 in the body is called breath. There are processes of external and internal respiration. External respiration ensures the exchange of gases between the body and the external environment, internal respiration - the consumption of O2 and the release of CO 2 by the cells of the body.

The factor that ensures the diffusion of gases through the respiratory surfaces is the difference in their concentrations. The movement of dissolved gases occurs in the direction from the area with their high concentration to the area of ​​low concentration.

In small organisms, gas exchange, as a rule, is carried out diffusely over the entire surface of the body (or cell). In larger animals, gases are transported to the tissues either directly (tracheal system of insects) or with the help of special vehicles (blood, hemolymph).

The amount of oxygen entering the tissues of the animal depends on the area of ​​the respiratory surface and the difference in oxygen concentration on them. Therefore, in all respiratory organs there is an increase in the respiratory epithelium. To maintain a high gradient of oxygen diffusion on the exchange membrane, the movement of the medium (ventilation) is necessary. It is provided by respiratory rhythmic movements of the entire body of the animal (small bristle worm tubifex, leeches) or certain parts of it (crustaceans), as well as the work of the ciliary epithelium (molluscs, lancelet).

A number of fairly large animals do not have specialized respiratory organs. In them, gas exchange is carried out through moist skin, equipped with an abundant network of blood vessels (earthworm). Cutaneous respiration as an additional characteristic of animals with specialized respiratory organs. For example, in eels with gills, 60% of the oxygen demand is provided by skin respiration, in frogs with lungs, this value is more than 50%.

The respiratory organs in the aquatic environment are the gills, in the land-air environment - the lungs and trachea.

Gills are organs located outside the body cavity in the form of epithelial surfaces penetrated by a dense network of blood capillaries. Gill breathing is characteristic of polychaete annelids, most molluscs, crustaceans, fish, and amphibian larvae. Gill respiration is most effective in fish. It is based on backflow phenomenon: blood in the capillaries of the gill filaments flows in the opposite direction to the current of the ox washing the gills.

Lungs, as a rule, are internal organs and are protected from drying out. There are two types of them: diffusion and ventilation. In the lungs of the first type, gas exchange is carried out only by diffusion. Relatively small animals have such lungs: lung mollusks, scorpions, spiders. Only terrestrial vertebrates have ventilatory lungs.

The complication of the structure of the lungs in the series from amphibians to mammals is associated with an increase in the area of ​​the respiratory epithelium. So, in amphibians, 1 cm 3 of lung tissue has a total gas exchange surface of 20 cm 2. The same indicator for human lung epithelium is 300 cm 2 .

Simultaneously with an increase in the respiratory surface, the mechanism of lung ventilation improves, which, starting with reptiles, is carried out by changing the volume of the chest, and in mammals - with the participation of the muscles of the diaphragm. These adaptations allowed warm-blooded animals (birds and mammals) to dramatically increase the intensity of their metabolism.

The third type of respiratory organs - trachea. They are air-filled thin-walled, branching, non-collapsing protrusions inside the body. The tracheae communicate with the external environment through openings in the cuticle - spiracles. In insects, they most often have 12 pairs: 3 pairs on the chest and 9 pairs on the abdomen. The spiracles can close or open depending on the amount of oxygen. With a high degree of development of the tracheal system (in insects), its numerous branches braid all the internal organs and directly provide gas exchange in tissues. The fundamental difference between tracheal respiration and pulmonary and gill respiration is that it does not require the participation of blood as a transport mediator in gas exchange.

The tracheal system is able to support enough high level tissue respiration, thereby providing a high physiological activity of the insect.

Ventilation of the trachea in insects in the absence of flight is carried out most often by rhythmic contractions of the abdomen; during flight, it is enhanced by movements of the chest.

Aquatic larvae of some insects breathe with the help of tracheal gills. In this case, the tracheal system is devoid of spiracles, i.e. it is closed and filled with air. The branches of the closed tracheal system go into the "gills" - appendages with a large surface and a thin cuticle that allows gas exchange between water and air of the tracheal system. Such tracheal gills are present, for example, in mayfly larvae. In the larvae of some dragonflies, the tracheal gills are located in the cavity of the rectum, and the insect ventilates them by taking water into the intestine and pushing it back.