However, the share of skin participation in human breathing is negligible compared to the lungs, because the total surface of the body is less than 2 m2 and does not exceed 3% of the total surface of the pulmonary alveoli.
Main components respiratory organs are the respiratory tract, lungs, respiratory muscles, including the diaphragm. Atmospheric air entering the human lungs is a mixture of gases - nitrogen, oxygen, carbon dioxide and some others (Fig. 2).
Rice. 2. Average values of partial pressure of gases (mm Hg) in dry
inhaled air, alveoli, in exhaled air and in the blood during muscle rest (middle part of the figure). Partial pressure of gases in venous blood flowing from the kidneys and muscles (lower part of the figure)
The partial pressure of a gas in a mixture of gases is the pressure that this gas would create in the absence of other components of the mixture. It depends on the percentage of gas in the mixture: the higher it is, the higher the partial pressure of this gas. The partial pressure of oxygen* in the alveolar air is 105 mmHg. Art., and in venous blood – 40 mm Hg. Art., so oxygen diffuses from the alveoli into the blood. Almost all the oxygen in the blood is chemically bound to hemoglobin. Partial oxygen pressure in tissues is relatively low, so it diffuses from the blood capillaries into the tissue, providing tissue respiration and energy conversion processes.
The transport of carbon dioxide, one of the end products of metabolism, occurs in a similar way in the opposite direction. Carbon dioxide is released from the body through the lungs. Nitrogen is not used in the body. Partial pressure of oxygen, carbon dioxide, nitrogen in atmospheric air and on different levels oxygen transport schemes are shown in Fig. 2.
A– outer cylinder, b– glass window for readings, V– inner cylinder, G– an air cylinder to balance the inner cylinder, d– water
Thanks to diffusion, the composition of the alveolar air continuously changes: the oxygen concentration in it decreases, and the concentration of carbon dioxide increases. To maintain the breathing process, the composition of gases in the lungs must be constantly updated. This occurs during ventilation of the lungs, i.e. breathing in the usual sense of the word. When we inhale, the volume of the lungs increases and air enters them from the atmosphere. At the same time, the alveoli expand. At rest, about 500 ml of air enters the lungs with each breath. This volume of air is called tidal volume. The human lungs have a certain capacity reserve that can be used during intense breathing. After a calm inhalation, a person can inhale about 1500 ml of air. This volume is called inspiratory reserve volume. After a calm exhalation, you can, making an effort, exhale about 1500 ml of air. This expiratory reserve volume. Tidal volume and inspiratory and expiratory reserve volumes add up to vital capacity(VEL). IN in this case it is equal to 3500 ml (500 + 1500 + 1500). To measure vital capacity, they do especially deep breath and after that exhale as much as possible into the tube special device– spirometer. Measurements are taken in a standing position at rest (Fig. 3). The value of vital capacity depends on gender, age, body size and fitness. This figure varies widely, averaging 2.5–4 liters in women and 3.5–5 liters in men. In some cases, people are very tall, for example, among basketball players, vital capacity can reach 9 liters. Under the influence of training, for example when performing special breathing exercises, vital capacity increases (sometimes even by 30%).
Rice. 4. Miller's nomogram for determining the proper vital capacity of the lungs
Vital capacity can be determined using Miller's nomogram (Fig. 4). To do this, you need to find your height on the scale and connect it with a straight line to your age (separately for women and men). This straight line will intersect the vital capacity scale. An important indicator in physical performance research is minute volume of respiration, or ventilation. Ventilation is the actual amount of air that different conditions passes through the lungs within 1 minute. At rest, pulmonary ventilation is 5–8 l/min.
A person is able to control his breathing. You can delay it for a while or intensify it. The ability to increase breathing is measured by the value maximum pulmonary ventilation(MLV). This value, like vital capacity, depends on the degree of development of the respiratory muscles. During physical work, pulmonary ventilation increases and reaches 150–180 l/min. The harder the work, the greater the pulmonary ventilation.
The elasticity of the lung largely depends on the surface tension forces of the wetting fluid. inner surface alveoli (s = 5 x 10–2 n/m). Nature itself took care of making breathing easier and created substances that lower surface tension. They are synthesized by special cells located in the walls of the alveoli. The synthesis of these surfactants continues throughout a person’s life.
In those rare cases when a newborn does not have lung cells producing surfactants, the child cannot take his first breath on his own and dies. Due to the lack or absence of surfactants in the alveoli, about half a million newborns worldwide die every year without taking their first breath.
However, some lung-breathing animals can do without surfactants. First of all, this applies to cold-blooded animals - frogs, snakes, crocodiles. Because these animals do not need to expend energy to stay warm, their oxygen requirements are not as high as those of warm-blooded animals, and therefore they have less lung surface area. If in a person’s lungs the surface area of contact between 1 cm 3 of air and blood vessels is about 300 cm 2, then in a frog it is only 20 cm 2.
The relative decrease in lung area per unit volume in cold-blooded animals is due to the fact that the diameter of their alveoli is approximately 10 times larger than in warm-blooded animals. And from Laplace's law ( p= 4a/R) it follows that the additional pressure that must be overcome during inhalation is inversely proportional to the radius of the alveoli. The large radius of the alveoli in cold-blooded animals allows them to easily inhale even without reducing the size p due to surfactants.
There are no surfactants in the lungs of birds. Birds are warm-blooded animals and lead an active lifestyle. At rest, birds' need for oxygen is higher than that of other vertebrates, including mammals, and during flight it increases many times over. The respiratory system of birds is capable of saturating the blood with oxygen even when flying at high altitudes, where its concentration is much lower than at sea level. Any mammals (including humans), once at such a height, begin to experience oxygen starvation, sharply reduce their motor activity, and sometimes even fall into a semi-fainting state. How can the lungs of birds, in the absence of surfactants, cope with this difficult task?
In addition to the normal lungs, birds have an additional system consisting of five or more pairs of thin-walled air sacs connected to the lungs. The cavities of these bags branch widely in the body and extend into some bones, sometimes even into the small bones of the phalanges of the fingers. As a result, the respiratory system, for example in ducks, occupies about 20% of the body volume (2% lungs and 18% air sacs), while in humans it is only 5%. The walls of the air sacs are poor in blood vessels and do not participate in gas exchange. Air bags not only help to blow air through the lungs in one direction, but also reduce the density of the body, friction between its individual parts, and contribute to effective cooling of the body.
The bird's lung is built from parallel-connected thin tubes, open on both sides, surrounded by blood vessels - air capillaries, extending from the parabronchi. During inhalation, the volumes of the anterior and posterior air sacs increase. Air from the trachea enters directly into the posterior sacs. The anterior sacs do not communicate with the main bronchus and are filled with air leaving the lungs (Fig. 5, A).
Rice. 5 . Air movement in the respiratory system of a bird: A- inhale, b– exhale
(K1 and K2 are valves that change air movement)
When you exhale, the communication between the anterior sacs and the main bronchus is restored, and the communication between the posterior sacs is interrupted. As a result, during exhalation, air flows through the bird’s lung in the same direction as during inhalation (Fig. 5, b). During breathing, only the volume of the air sacs changes, and the volume of the lung remains almost constant. It becomes clear why there are no surfactants in bird lungs: they are simply of no use there, because there is no need to inflate the lungs.
Some organisms use air for more than just breathing. The body of the pufferfish, which lives in the Indian Ocean and the Mediterranean Sea, is dotted with numerous needles - modified scales. In a calm state, the needles fit more or less tightly to the body. When in danger, the pufferfish rushes to the surface of the water and, taking air into the intestines, turns into an inflated ball. In this case, the needles rise and stick out in all directions. The fish stays close to the surface of the water, with its belly turned upside down, and part of its body protrudes above the water. In this position, the pufferfish is protected from predators both below and above. When the danger has passed, the pufferfish releases air, and its body takes on its normal size.
The air shell of the Earth (atmosphere) is held near the Earth due to the forces of gravity and exerts pressure on all bodies with which it comes into contact. The human body is adapted to atmospheric pressure and does not tolerate its decrease well. When climbing mountains (4 thousand meters, and sometimes lower), many people feel unwell and have seizures “ mountain sickness": it becomes difficult to breathe, often from the ears and nose there's blood coming out, loss of consciousness is possible. Since the articular surfaces fit tightly to each other (in the articular capsule covering the joints, the pressure is reduced) due to atmospheric pressure, high in the mountains, where the atmospheric pressure is greatly reduced, the action of the joints is disrupted, the arms and legs do not “listen” well, dislocations easily occur . Climbers and pilots, when climbing to great heights, take oxygen equipment with them and specially train before the ascent.
To the program special training cosmonauts undergo mandatory training in a pressure chamber, which is a hermetically sealed steel chamber connected to a powerful pump that creates high or low pressure in it. IN modern medicine The pressure chamber is used in the treatment of many diseases. Pure oxygen is supplied to the chamber and high pressure is created. Due to the diffusion of oxygen through the skin and lungs, its tension in the tissues increases significantly. This treatment method is very effective, for example, for wound infections (gas gangrene) caused by anaerobic microorganisms for which oxygen is a strong poison.
At the altitudes where modern spaceships fly, there is practically no air, so the cabins of the ships are made hermetically sealed, and normal air pressure and composition, humidity and temperature are created and maintained in them. Violation of the cabin seal leads to tragic consequences.
The Soyuz-11 spacecraft with three cosmonauts on board (G. Dobrovolsky, V. Volkov, V. Patsayev) was launched into low-Earth orbit on June 6, 1971, and on June 30, upon returning to Earth, the crew died as a result of depressurization of the descent module after separation of the compartments at an altitude of 150 km.
Some information about breathing
The person breathes rhythmically. A newborn child makes respiratory movements 60 times per 1 minute, a five-year-old - 25 times per 1 minute, at 15-16 years old the respiratory rate decreases to 16-18 per 1 minute and remains this way until old age, when it becomes more frequent again.
Some animals have a much lower breathing rate: the condor makes one respiratory movement every 10 seconds, and the chameleon every 30 minutes. The chameleon's lungs are connected by special sacs into which it takes in air and at the same time inflates greatly. The low breathing rate allows the chameleon not to detect its presence for a long time.
At rest and at normal temperature, a person consumes approximately 250 ml of oxygen per minute, 15 liters per hour, 360 liters per day. The amount of oxygen consumed at rest is not constant - it is greater during the day than at night, even if a person sleeps during the day. This is probably a manifestation of circadian rhythms in the life of the body. A lying person consumes approximately 15 liters of oxygen in 1 hour, standing - 20 liters, when walking calmly - 50 liters, when walking at a speed of 5 km/h - 150 liters.
At atmospheric pressure a person can breathe pure oxygen about one day, after which it occurs pneumonia ending in death. At a pressure of 2–3 atm, a person can breathe pure oxygen for no more than 2 hours, then a violation of coordination of movements, attention, and memory occurs.
In 1 minute, 7–9 liters of air normally passes through the lungs, but for a trained runner - about 200 liters.
Internal organs during intense work they require an increased supply of oxygen. During strenuous activity, oxygen consumption by the heart increases by 2 times, by the liver by 4 times, and by the kidneys by 10 times.
With each inhalation, a person performs work sufficient to lift a load weighing 1 kg to a height of 8 cm. Using work performed within 1 hour, it would be possible to lift this load to a height of 86 m, and overnight - to 690 m.
It is known that the respiratory center is excited when the concentration of carbon dioxide in the blood increases. If the concentration of carbon dioxide in the blood is reduced, a person may not breathe for a longer period of time than usual. This can be achieved by rapid breathing. Divers use a similar technique, and experienced pearl divers can stay underwater for 5–7 minutes.
Dust is everywhere. Even at the top of the Alps, 1 ml of air contains about 200 dust particles. The same volume of urban air contains more than 500 thousand dust particles. The wind carries dust over very long distances: for example, dust from the Sahara has been discovered in Norway, and volcanic dust from the islands of Indonesia has been found in Europe. Dust particles are retained in the respiratory system and can lead to various diseases.
In Tokyo, where every resident has 40 cm2 of street surface, police officers wear oxygen masks. In Paris, clean air booths have been installed for passers-by. Pathologists recognize Parisians during autopsies by their black lungs. In Los Angeles, plastic palm trees are installed on the street because living ones are dying due to high air pollution.
To be continued
* This refers to the partial pressure of oxygen in the air at which it is in equilibrium with oxygen dissolved in the blood or other medium, also called oxygen tension in this medium.
Tests
706-01. Vertebrates with a three-chambered heart, whose reproduction is closely related to water, are grouped into the class
A) Bony fish
B) Mammals
B) Reptiles
D) Amphibians
Answer
706-02. What class do animals belong to, the diagram of the heart structure of which is shown in the figure?
A) Insects
B) Cartilaginous fish
B) Amphibians
D) Birds
Answer
706-03. The characteristic that distinguishes amphibians from fish is
A) cold-bloodedness
B) structure of the heart
B) development in water
D) isolation circulatory system
Answer
706-04. Amphibians differ from fish in having
A) brain
B) closed circulatory system
B) paired lungs in adults
D) sense organs
Answer
706-05. Which characteristic among those listed distinguishes most animals of the class Amphibians from Mammals?
B) external fertilization
B) sexual reproduction
D) use of the aquatic environment for habitat
Answer
706-06. In the process of evolution, reptiles acquired, unlike amphibians,
A) closed circulatory system
B) high fertility
B) a large egg with embryonic membranes
D) three-chambered heart
Answer
706-07. If, in the process of evolution, an animal has formed the heart shown in the figure, then the animal’s respiratory organs should be 
A) lungs
B) skin
B) lung sacs
D) gills
Answer
706-08. In which group of animals does reproduction not involve water?
A) skullless (lancelets)
B) bony fish
B) amphibians
D) reptiles
Answer
706-09. In which animals does the embryo develop completely inside the egg?
A) bony fish
B) tailed amphibians
B) tailless amphibians
D) reptiles
Answer
706-10. Vertebrates with a three-chambered heart, whose reproduction is not associated with water, are grouped into the class
A) Bony fish
B) Mammals
B) Reptiles
D) Amphibians
Answer
706-11. Vertebrates with unstable body temperature, pulmonary breathing, a three-chambered heart with an incomplete septum in the ventricle are classified as
A) bony fish
B) amphibians
B) reptiles
D) cartilaginous fish
Answer
706-12. Reptiles, unlike amphibians, tend to
A) external fertilization
B) internal fertilization
B) development with the formation of a larva
D) division of the body into head, torso and tail
Answer
706-13. Which of the following animals is cold-blooded?
A) fast lizard
B) Amur tiger
B) steppe fox
D) common wolf
Answer
706-14. What class do animals with dry skin with horny scales and a three-chambered heart with an incomplete septum belong to?
A) Reptiles
B) Mammals
B) Amphibians
D) Birds
Answer
706-15. Birds differ from reptiles by having
A) internal fertilization
B) central nervous system
B) two circles of blood circulation
G) constant temperature body
Answer
706-15. What structural feature is similar in modern reptiles and birds?
A) bones filled with air
B) dry skin, devoid of glands
B) caudal region in the spine
D) small teeth in the jaws
Answer
706-16. In which animal does gas exchange between atmospheric air and blood occur through the skin?
A) killer whale
B) triton
B) crocodile
D) pink salmon
Answer
706-17. Which group of animals has a heart consisting of two chambers?
A) fish
B) amphibians
B) reptiles
D) mammals
Answer
706-18. The development of the baby in the uterus occurs at
A) birds of prey
B) reptiles
B) amphibians
D) mammals
Answer
706-19. Representatives of which class of chordates are characterized by cutaneous respiration?
A) Amphibians
B) Reptiles
B) Birds
D) Mammals
Answer
706-20. The sign of the amphibian class is
A) chitinous cover
B) bare skin
B) live birth
D) paired limbs
Answer
706-21. By what characteristics do representatives of the class Amphibians differ from other vertebrates?
A) spine and free limbs
B) pulmonary breathing and the presence of a cloaca
B) bare mucous skin and external fertilization
D) closed circulatory system and two-chamber heart
Answer
706-22. Which feature among the listed distinguishes animals of the class Reptiles from animals of the class Mammals?
A) closed circulatory system
B) unstable body temperature
C) development without transformation
D) use of the ground-air environment for habitat
Physiology of respiration 1.
1. The essence of breathing. The mechanism of inhalation and exhalation.
2. The emergence of negative pressure in the peripulmonary space. Pneumothorax, atelectasis.
3. Types of breathing.
4. Vital capacity of the lungs and their ventilation.
n 1. The essence of breathing. The mechanism of inhalation and exhalation.
n The set of processes that ensure the exchange of oxygen and carbon dioxide between the external environment and the tissues of the body is called breathing , and the set of organs that provide respiration is respiratory system.
n Types of breathing:
n Cellular - in unicellular organisms across the entire surface of the cell.
n Cutaneous – in multicellular organisms (worms) across the entire surface of the body.
n Tracheal - in insects through special tracheas running along the lateral surface of the body.
n Gill - in fish through the gills.
n Pulmonary - in amphibians through the lungs.
n In mammals, through specialized respiratory organs: nasopharynx, larynx, trachea, bronchi, lungs, and also participate rib cage, diaphragm and muscle group: inspirators and expirators.
n Lungs (0.6-1.4% of body weight) - paired organs, have lobes (right - 3, left - 2), divided into lobules (each with 12-20 acini), bronchi branch into bronchioles, ending in alveoli .
n Morphological and functional unit of the lung - acini (lat. acinus - grape berry)- branching of the respiratory bronchiole into alveolar ducts ending in 400-600 alveolar sacs.
n The alveoli are filled with air and do not collapse due to the presence of surfactants on their walls - surfactants (phospholipoproteins or lipopolysaccharides).
n Breathing stages:
n a) pulmonary ventilation - gas exchange between the lungs and the external environment;
n b) exchange of gases in the lungs between alveolar air and capillaries of the pulmonary circulation;
n c) transport of O2 and CO2 by blood;
n d) exchange of gases between the blood of the capillaries of the systemic circulation and tissue fluid;
n e) intracellular respiration is a multi-stage enzymatic process of oxidation of substrates in cells.
n The main physical process that ensures the movement of O2 from external environment to cells and CO2 in the opposite direction - this is diffusion , i.e., the movement of a gas as a dissolved substance along concentration gradients.
n Inhalation - inspiration .
n The movement of air into and out of the lungs into the environment is caused by changes in pressure within the lungs. When the lungs expand, the pressure in them becomes below atmospheric (by 5-8 mm Hg) and air is sucked into the lungs. The lungs themselves do not have muscle tissue. The change in lung volume depends on the change in chest volume, i.e. the lungs passively follow changes in the chest. When inhaling, the chest expands in the vertical, sagittal and frontal directions. When the inspiratory muscles (inspirators) - the external intercostal muscles and the diaphragm - contract, the ribs rise upward, and the chest expands. The diaphragm takes on a cone shape. All this helps reduce pressure in the lungs and suck in air. The thickness of the alveoli is small, so gases easily diffuse through the wall of the alveoli.
n Exhalation - expiration .
n When you exhale, the inspiratory muscles relax and the chest, due to its heaviness and elasticity of the costal cartilages, returns to its original position. The diaphragm relaxes and becomes dome-shaped. Thus, at rest, exhalation occurs passively, due to the end of inhalation.
n With forced breathing, exhalation becomes active - it is enhanced by the contraction of expiratory muscles (exhalers) - internal intercostal muscles, abdominal muscles - external and internal oblique, transverse and straight abdominal, dorsal serratus exhaler. The pressure in the abdominal cavity increases, which pushes the diaphragm into the chest cavity, the ribs descend and move closer to each other, which reduces the volume of the chest.
n When the lungs collapse, the air is squeezed out, the pressure in them becomes higher than atmospheric (by 3-4 mm Hg).
n 2. The emergence of negative pressure in the peripulmonary space. Pneumothorax, atelectasis
n The lungs in the chest are separated by pleural layers: visceral - adjacent to the lungs, parietal - lining the chest from the inside. Between the leaves is the pleural cavity. It is filled with pleural fluid. The pressure in the pleural cavity is always 4-10 mm Hg lower than atmospheric pressure. Art. (in the lungs 760 mm Hg). This is due to: 1) more rapid growth chest in comparison with lungs in postnatal ontogenesis; 2) elastic traction(elastic tension) of the lungs, i.e., a force counteracting their stretching by air. The pleural cavity is sealed from environment.
n When air enters the pleural cavity (eg during injury), the pressure in the pleural cavity equalizes with atmospheric pressure - pneumothorax , while the lung collapses - atelectasis and breathing may stop.
n Negative pressure of the pleural cavity is formed at birth. During the first inhalation, the chest expands, the lungs expand, because they are hermetically separated - negative pressure is formed in the pleural cavity. In the fetus, the lungs are in a collapsed state, the chest is flattened, the head of the ribs is outside the glenoid fossa. At birth, the fetus accumulates in the blood carbon dioxide, it stimulates the respiratory center. From here, impulses arrive to the inspiratory muscles, which contract, the heads of the ribs enter the articular fossae. The chest increases in volume, the lungs expand.
n The relationship between chest volume and lung volume during breathing is usually illustrated using physical Donders models:
n 1. Glass cover,
n 2. On top there is a plug with a hole,
n 3. Bottom – elastic film with a ring,
n 4. Inside the cap are the lungs of a rabbit.
n When the volume inside the cap increases due to stretching of the elastic film, the pressure in the cavity of the cap decreases, air enters the lungs through the hole in the plug, they expand and vice versa.
n 3. Types of breathing.
n 1. Thoracic or costal – the change in chest volume occurs mainly due to the intercostal muscles (expirators and inspirators). Characteristic of dogs and women.
n 2. Abdominal or diaphragmatic – changes in chest volume occur mainly due to the diaphragm and muscles abdominals. Characteristic for men.
n 3. Mixed or thoracoabdominal – changes in chest volume occur equally with contraction of the intercostal muscles, diaphragm and abdominal muscles. Characteristic of farm animals.
n Types of breathing have diagnostic value: if the abdominal or chest cavity change.
n 4. Vital capacity of the lungs and their ventilation.
n Vital capacity of the lungs (VC) consists of 3 volumes of air entering and leaving the lungs during breathing:
n 1. Respiratory - volume of air during quiet inhalation and exhalation. For small animals (dogs, small animals) - 0.3-0.5 l, for large animals (cattle, horses) - 5-6 l.
n 2. Additional or reserve inspiratory volume– the volume of air that enters the lungs during maximum inspiration after a quiet inhalation. 0.5-1 and 5-15 l.
n 3. Expiratory reserve volume– the volume of air at maximum exhalation after a quiet exhalation. 0.5-1 and 5-15 l.
n Vital capacity is determined by measuring the volume of maximum expiration after the previous maximum inspiration using spirometry. In animals it is determined by inhaling a gas mixture with high content carbon dioxide.
n Residual volume - the volume of air that remains in the lungs even after maximum exhalation.
n Air of “harmful” or “dead” space – the volume of air that does not participate in gas exchange and is located in the upper part of the breathing apparatus – nasal cavity, pharynx, trachea (20-30%).
n The meaning of “harmful” space:
n 1) the air warms up (abundant supply of blood vessels), which prevents hypothermia of the lungs;
n 2) the air is purified and humidified (alveolar macrophages, many mucous glands);
n 3) when the cilia of the ciliated epithelium are irritated, sneezing occurs - reflex removal harmful substances;
n 4) receptors olfactory analyzer(“olfactory labyrinth”);
n 5) regulation of the volume of inhaled air.
n The process of updating the gas composition of alveolar air during inhalation and exhalation – ventilation .
n The intensity of ventilation is determined by the depth of inspiration and the frequency breathing movements.
n Inhalation depth determined by the amplitude of chest movements, as well as by measuring lung volumes.
n Respiratory rate counted by the number of chest excursions over a certain period of time (4-5 times less than heart rate).
n Horse (per minute) – 8-16; Cattle – 12-25; MRS – 12-16; pig – 10-18; dog – 14-24; rabbit – 15-30; fur - 18-40.
n Minute breathing volume is the product of the tidal volume of air and the respiratory rate per minute.
n Ex: horse: 5 l x 8 = 40 l
n Methods for studying breathing:
n 1. Pneumography– registration of respiratory movements using a pneumograph.
n 2. Spirometry– measurement tidal volumes using spirometers.
Lecture 25.
Physiology of respiration 2.
1. Gas exchange between the alveoli and blood. State of blood gases.
2. Transport of gases and factors determining it. Tissue respiration.
3. Lung functions not related to gas exchange.
4. Regulation of breathing, respiratory center and its properties.
5. Peculiarities of breathing in birds.
Gas exchange between the alveoli and blood. State of blood gases.
In the alveoli of the lungs, O2 and CO2 are exchanged between the air and the blood of the capillaries of the pulmonary circulation.
Exhaled air contains more O2 and less CO2 than alveolar air, because the air of the harmful space is mixed with it (7:1).
The amount of gas diffusion between the alveoli and blood is determined by purely physical laws operating in the gas-liquid system separated by a semi-permeable membrane.
The main factor determining the diffusion of gases from the air alveoli into the blood and from the blood into the alveoli is the difference in partial pressure, or partial pressure gradient. Diffusion occurs from an area of higher partial pressure to an area of lower pressure.
Gas composition of air
Partial pressure(lat. partial – partial) - this is the pressure of a gas in a mixture of gases that it would exert at the same temperature, occupying the entire volume
P = RA x a/100,
where P is the partial pressure of the gas, PA is the atmospheric pressure, and is the volume of gas included in the mixture in %, 100 –%.
P O2 inhalation = 760 x 21 / 100 = 159.5 mm Hg. Art.
P CO2 inhalation. = 760 x 0.03 / 100 = 0.23 mm Hg. Art.
P N2 inhale. = 760 x 79 / 100 = 600.7 mm Hg. Art.
Equality P O2 or P CO2 never occurs in interacting media. There is a constant flow in the lungs fresh air due to respiratory movements of the chest, while in the tissues the difference in gas tension is maintained by oxidation processes.
The difference between the partial pressure of O2 in the alveolar air and the venous blood of the lungs is: 100 - 40 = 60 mmHg, which causes the diffusion of O2 into the blood. When the O2 voltage difference is 1 mmHg. Art. In a cow, 100-200 ml of O2 passes into the blood per minute. The average need of an animal for O2 at rest is 2000 ml per 1 min. Pressure differences of 60 ml Hg. Art. more than enough to saturate the blood with O2 both at rest and during exercise.
60 mmHg x 100-200 ml = 6000-12000 ml O2 per min
LECTURE No. 15. Physiology of respiration.
1.
2. External breathing(pulmonary ventilation).
3.
4. Transport of gases (O2, CO2) by blood.
5. Exchange of gases between blood and tissue fluid. Tissue respiration.
6. Regulation of breathing.
1. The essence of breathing. Respiratory system.
Breath physiological function, ensuring gas exchange between the body and the external environment, and the set of organs involved in gas exchange - the respiratory system.
Evolution of the respiratory system.
1.In single-celled organisms respiration occurs through the surface (membrane) of the cell.
2.In lower multicellular animals gas exchange occurs through the entire surface of the external and internal (intestinal) cells of the body.
3.In insects the body is covered with a cuticle and therefore special respiratory tubes (tracheas) appear that penetrate the entire body.
4.In fish The respiratory organs are gills - numerous leaves with capillaries.
5.In amphibians air sacs (lungs) appear, in which the air is renewed with the help of respiratory movements. However, the main exchange of gases occurs through the surface of the skin and accounts for 2/3 of the total volume.
6.In reptiles, birds and mammals the lungs are already well developed, and the skin becomes a protective covering and gas exchange through it does not exceed 1%. In horses at high physical activity respiration through the skin increases to 8%.
Respiratory system.
The respiratory apparatus of mammals is a set of organs that perform air-conducting and gas-exchange functions.
Upper airways: nasal cavity, mouth, nasopharynx, larynx.
Lower airways: trachea, bronchi, bronchioles.
Gas exchange function performed by respiratory porous tissue - lung parenchyma. The structure of this tissue includes pulmonary vesicles - alveoli.
the wall of the airways has cartilaginous skeleton and their lumen never subsides. Mucous membrane breathing tube lined ciliated epithelium with cilia. Trachea before the entrance to the lungs dichotomously is divided into two main bronchi (left and right), which further divide and form bronchial tree. The division ends with finite (terminal) bronchioles (diameter up to 0.5-0.7 mm).
Lungs located in the chest cavity and have the shape of a truncated cone. The base of the lung faces backward and is adjacent to the diaphragm. The outside of the lungs is covered with a serous membrane - visceral pleura. Parietal pleura (bone) lines the chest cavity and fuses tightly with the costal wall. Between these layers of pleura there is a slit-like space (5-10 microns) - pleural cavity filled with serous fluid. The space between the right and left lung called mediastinum. This is where the heart, trachea, blood vessels and nerves are located. The lungs are divided into lobes, segments and lobules. The degree of severity of this division varies among different animals.
The morphological and functional unit of the lung is acinus (lat. acinus - grape berry). Acinus includes respiratory (respiratory) bronchiole and alveolar ducts, which end alveolar sacs. One acini contains 400-600 alveoli; 12-20 acini form the pulmonary lobe.
Alveoli – these are bubbles, the inner surface of which is lined with a single layer flat epithelium. Among epithelial cells there are : alveolocytes of the 1st order, which, together with the endothelium of the lung capillaries, form air-blood barrier And alveocytes of the 2nd order perform a secretory function, secreting biologically active substance surfactant Surfactan (phospholipoproteins - surfactant) lines the inner surface of the alveoli, increases surface tension and prevents the alveoli from collapsing.
Functions of the airways.
Airways(up to 30% of inhaled air is retained in them) do not take part in gas exchange and are called "harmful" space. However, the upper and lower airways play a large role in the life of the body.
Here the inhaled air is warmed, humidified and purified. This is possible thanks to the well-developed mucous membrane of the respiratory tract, which is abundantly vascularized, contains goblet cells, mucous glands and a large number of cilia of the ciliated epithelium. In addition, there are receptors for the olfactory analyzer, receptors for the protective reflexes of coughing, sneezing, snorting, and irritant (irritation) receptors. They are located in the bronchioles and react to dust particles, mucus, and caustic vapors. When irritant receptors are irritated, a burning sensation, soreness occurs, a cough appears, and breathing quickens.
Gas exchange between the body and the external environment is ensured by a set of strictly coordinated processes included in the respiratory structure of higher animals.
2. External respiration (pulmonary ventilation) a constant process of updating the gas composition of the alveolar air, which is carried out when inhalation and exhalation.
Lung tissue does not have active muscle elements and therefore its increase or decrease in volume occurs passively in time with the movements of the chest (inhalation, exhalation). This is due negative intrapleural pressure(below atmospheric: when inhaling by 15-30 mm Hg. Art., when exhaling by 4-6 mm Hg. Art.) in a hermetically sealed chest cavity.
The mechanism of external respiration.
The act of inhalation (lat. inspiration - inspiration) carried out by increasing the volume of the chest. The inspiratory muscles (breathers) take part in this: external intercostal muscles and diaphragm. During forced breathing, the following muscles are activated: levator ribs, scalene supracostalis, serratus dorsalis. The volume of the chest increases in three directions - vertical, sagittal (antero-posterior) and frontal.
The act of exhalation (lat. expiration - expiration) in a state of physiological rest is predominantly passive in nature. As soon as the inhalation muscles relax, the chest, due to its heaviness and the elasticity of the costal cartilages, returns to its original position. The diaphragm relaxes and its dome becomes convex again.
During forced breathing, the act of exhalation is facilitated by the expiratory muscles: internal intercostal, external and internal oblique, transverse and rectus muscles abdominal wall, dorsal serrated exhalator.
Types of breathing.
Depending on the transformation of certain muscles involved in respiratory movements, there are three types of breathing:
1 - thoracic (costal) type of breathing carried out by contraction of the external intercostal muscles and muscles of the pectoral girdle;
2 – abdominal (diaphragmatic) type of breathing– contractions of the diaphragm and abdominal muscles predominate;
3 – mixed (costo-abdominal) type of breathing most common in farm animals.
At various diseases breathing pattern may change. In diseases of the thoracic organs, the diaphragmatic type of breathing predominates, and in diseases of the abdominal organs, the costal type of breathing predominates.
Respiratory frequency.
Respiratory frequency refers to the number of respiratory cycles (inhalation-exhalation) per minute.
Horse 8 - 12 Dog 10 - 30
Croup horn. cattle 10 - 30 Rabbits 50 - 60
Sheep 8 - 20 Chickens 20 - 40
Pig 8 - 18 Ducks 50 - 75
Person 10 - 18 Mouse 200
Please note that the table shows average values. The frequency of respiratory movements depends on the type of animal, breed, productivity, functional state, time of day, age, ambient temperature, etc.
Lung volumes.
There is a distinction between total and vital lung capacity. The vital capacity of the lungs (VC) consists of three volumes: respiratory and reserve volumes of inhalation and exhalation.
1.Tidal volume- this is the volume of air that can be calmly, effortlessly inhaled and exhaled.
2.Inspiratory reserve volume – This is the air that can be additionally inhaled after a calm inhalation.
3.Expiratory reserve volume- this is the volume of air that can be exhaled as much as possible after a quiet exhalation.
After a full, maximally deep exhalation, some air remains in the lungs – residual volume. The sum of vital fluid and residual air volume is total lung capacity.
The sum of the residual volume of air and the expiratory reserve volume is called alveolar air (functional residual capacity).
Lung volumes (in liters).
Horse Man
1. Respiratory V 5-6 0.5
2. Reserve V inhalation 12 1.5
3. Reserve V exhalation 12 1.5
4. Residual V 10 1
Ventilation- This is the renewal of the gas composition of the alveolar air during inhalation and exhalation. When assessing the intensity of lung ventilation, use minute volume of respiration(the amount of air passing through the lungs in 1 minute), which depends on the depth and frequency of respiratory movements.
The horse's tidal volume at rest 5-6 liters , respiratory rate 12 respiratory movements per 1 minute.
Hence: 5 l.*12=60 liters minute volume of breathing. for light work it is equal to 150-200 liters, during hard work 400-500 liters.
During breathing, not all parts of the lungs are ventilated and different intensity. Therefore they calculate alveolar ventilation coefficient is the ratio of inhaled air to alveolar volume. It should be taken into account that when a horse inhales 5 liters, 30% of the air remains in the airways “harmful space”.
Thus, 3.5 liters of inhaled air reaches the alveoli (70% of 5 liters of tidal volume). Therefore, the alveolar ventilation coefficient is 3.5 l.:22 l. or 1:6. That is, with each quiet breath, 1/6 of the alveoli are ventilated.
3. Diffusion of gases (exchange of gases between alveolar air and blood in the capillaries of the pulmonary circulation).
Gas exchange in the lungs occurs as a result of diffusion carbon dioxide (CO 2) from the blood into the alveoli of the lung, and oxygen (O 2) from the alveoli into the venous blood of the capillaries of the pulmonary circulation. It has been calculated that about 5% of the oxygen in the inhaled air remains in the body, and about 4% of carbon dioxide is released from the body. Nitrogen does not take part in gas exchange.
The movement of gases is determined purely physical laws (osmosis and diffusion), operating in a gas-liquid system separated by a semi-permeable membrane. These laws are based on the partial pressure difference or partial pressure gradient of gases.
Partial pressure (lat. partialis - partial) is the pressure of one gas included in the gas mixture.
Diffusion of gases occurs from an area more high pressure to a lower area.
Partial pressure of oxygen in alveolar air 102 mmrt. Art., carbon dioxide 40 mm Hg. Art. Tension in the venous blood of the capillaries of the lungs O2 =40 mm Hg. Art., CO2=46 mm Hg. Art.
Thus, the partial pressure difference is:
oxygen (O2) 102 – 40 = 62 mm Hg. Art.;
carbon dioxide (CO2) 46 – 40 = 6 mm Hg. Art.
Oxygen quickly enters through the pulmonary membranes and completely combines with hemoglobin and the blood becomes arterial. Carbon dioxide, despite the slight difference in partial pressure, has higher diffusion rate (25 times) from venous blood into the alveoli of the lung.
4. Transport of gases (O 2, CO 2) by blood.
Oxygen, passing from the alveoli into the blood, is in two forms - about 3% dissolved in plasma and about 97% of red blood cells combined with hemoglobin (oxyhemoglobin). The saturation of blood with oxygen is called oxygenation.
There are 4 iron atoms in one hemoglobin molecule, therefore, 1 hemoglobin molecule can connect 4 oxygen molecules.
NNb+ 4О 2 ↔ ННb(O 2) 4
Oxyhemoglobin (HHb (O 2) 4) - exhibits the property weak, easily dissociating acid.
The amount of oxygen present in 100 mm of blood when hemoglobin is completely converted to oxyhemoglobin is called oxygen capacity of the blood. It has been established that 1 g of hemoglobin can, on average, bind 1.34 mmoxygen. Knowing the concentration of hemoglobin in the blood, and it averages 15 g. / 100 ml, You can calculate the oxygen capacity of the blood.
15 * 1.34 = 20.4 vol.% (volume percent).
Transport of carbon dioxide in the blood.
The transport of carbon dioxide in the blood is difficult process, in which they take part red blood cells (hemoglobin, carbonic anhydrase enzyme) and blood buffer systems.
Carbon dioxide is found in the blood in three forms: 5% - in physically dissolved form; 10% - in the form of carbohemoglobin; 85% - in the form of potassium bicarbonates in erythrocytes and sodium bicarbonates in plasma.
CO 2 entering the blood plasma from the tissue immediately diffuses into red blood cells, where a hydration reaction occurs with the formation of carbonic acid (H 2 CO 3) and its dissociation. Both reactions are catalyzed by the enzyme carbonic anhydrase, which is contained in red blood cells.
H 2 O + CO 2 → H 2 CO 3
carbonic anhydrase
↓
H 2 CO 3 → H + + HCO 3 -
As the concentration of bicarbonate ions increases (NSO 3 -) in red blood cells, one part of them diffuses into the blood plasma and combines with buffer systems, forming sodium bicarbonate (NaHCO 3). The other part of HCO 3 remains in red blood cells and combines with hemoglobin (carbohemoglobin) and with potassium cations - potassium bicarbonate (KHCO 3).
In the capillaries of the alveoli, hemoglobin combines with oxygen (oxyhemoglobin) - this is a stronger acid that displaces carbonic acid from all compounds. Under the influence of carbonic anhydrase, its dehydration occurs.
H 2 CO 3 → H 2 O + CO 2
Thus, carbon dioxide dissolved and released during the dissociation of carbohemoglobin diffuses into the alveolar air.
5. Exchange of gases between blood and tissue fluid. Tissue respiration.
The exchange of gases between blood and tissues occurs in the same way due to the difference in the partial pressure of gases (according to the laws of osmosis and diffusion). The arterial blood entering here is saturated with oxygen, its voltage is 100 mmrt. Art. In tissue fluid, the oxygen tension is 20 - 40 mm Hg. Art., and in cells its level drops to 0.
Respectively: O 2 100 – 40 = 60 mm Hg. Art.
60 – 0 = 60 mm Hg. Art.
Therefore, oxyhemoglobin picks off oxygen, which quickly passes into the tissue fluid and then into the tissue cells.
Tissue respiration is a process biological oxidation in cells and tissues. Oxygen entering the tissue is affected by the oxidation of fats, carbohydrates and proteins. The energy released in this case accumulates in the form macroergic bonds - ATP. In addition to oxidative phosphorylation, oxygen is also used during microsomal oxidation - in microsomes of the endoplasmic reticulum of cells. In this case, the end products of oxidative reactions become water and carbon dioxide.
Carbon dioxide, dissolving in tissue fluid, creates tension there 60-70 mm Hg. Art., which is higher than in blood (40 mmHg).
CO 2 70 - 40 = 30 mm Hg. Art.
Thus, the high oxygen tension gradient and the difference in the partial pressure of carbon dioxide in the tissue fluid and blood cause its diffusion from the tissue fluid into the blood.
6. Regulation of breathing.
Respiratory center – this is a set of neurons located in all parts of the central nervous system and involved in the regulation of breathing.
The main part of the “core” of the Mislavsky respiratory center located in medulla oblongata, in the area of the reticular formation at the bottom of the fourth cerebral ventricle. Among the neurons of this center there is strict specialization (distribution of functions). Some neurons regulate the act of inhalation, others the act of exhalation.
Bulbar respiratory tract tra has a unique feature – automatic, which persists even with its complete deafferentation (after the cessation of influence from various receptors and nerves).
In area pons located "pneumotaxic center". It does not have automaticity, but it influences the activity of the neurons of the Mislavsky respiratory center, alternately stimulating the activity of the neurons for the act of inhalation and exhalation.
Nerve impulses go from the respiratory center to motor neurons nuclei of the thoracoventral nerve (3-4 cervical vertebrae– center of the diaphragmatic muscles) and to the motor neurons located in lateral horns thoracic spinal cord (innervates the external and internal intercostal muscles).
In the lungs (between the smooth muscles of the airways and around the capillaries of the pulmonary circulation) there are three groups of receptors: distensions and collapses, irritant, juxtacapillary. Information from these receptors about the condition of the lungs (stretching, collapse), their filling with air, entry irritants into the respiratory tract (gas, dust), changes in blood pressure in the pulmonary vessels, and enters the respiratory center via afferent nerves. This affects the frequency and depth of respiratory movements, the manifestation of protective reflexes of coughing and sneezing.
Great importance in the regulation of breathing have humoral factors. Vascular vessels react to changes in blood gas composition reflexogenic zones of the carotid sinus, aorta and medulla oblongata.
An increase in the concentration of carbon dioxide in the blood leads to stimulation of the respiratory center. As a result, breathing becomes faster - dyspnea (shortness of breath). Decreased levels of carbon dioxide in the blood slow down the rhythm of breathing - apnea.
What is gas exchange? Almost no living creature can do without it. Gas exchange in the lungs and tissues, as well as the blood, helps nourish cells nutrients. Thanks to him, we receive energy and vitality.
What is gas exchange?
Living organisms need air to exist. It is a mixture of many gases, the main shares of which are oxygen and nitrogen. Both of these gases are essential components to provide normal life organisms.
During evolution different types have developed their own devices for obtaining them, some have developed lungs, others have gills, and others only use skin. With the help of these organs, gas exchange occurs.
What is gas exchange? This is a process of interaction between the external environment and living cells, during which oxygen and carbon dioxide are exchanged. During breathing, oxygen enters the body along with air. Saturating all cells and tissues, it participates in oxidative reaction, turning into carbon dioxide, which is excreted from the body along with other metabolic products.
Gas exchange in the lungs
Every day we inhale more than 12 kilograms of air. The lungs help us with this. They are the most voluminous organ, capable of holding up to 3 liters of air in one full deep breath. Gas exchange in the lungs occurs with the help of alveoli - numerous bubbles that are intertwined with blood vessels.
Air enters them through the upper respiratory tract, passing through the trachea and bronchi. Capillaries connected to the alveoli take in air and distribute it throughout the circulatory system. At the same time, they release carbon dioxide to the alveoli, which leaves the body along with exhalation.
The process of exchange between alveoli and blood vessels is called bilateral diffusion. It occurs in just a few seconds and is carried out due to the difference in pressure. Oxygen-saturated atmospheric air has more oxygen, so it rushes to the capillaries. Carbon dioxide has less pressure, which is why it is pushed into the alveoli.
Circulation
Without the circulatory system, gas exchange in the lungs and tissues would be impossible. Our body is permeated with many blood vessels various lengths and diameters. They are represented by arteries, veins, capillaries, venules, etc. Blood circulates continuously in the vessels, facilitating the exchange of gases and substances.
Gas exchange in the blood occurs through two circulatory circuits. When breathing, the air begins to move in a large circle. It is carried in the blood by attaching to a special protein called hemoglobin, which is found in red blood cells.
From the alveoli, air enters the capillaries and then into the arteries, heading straight to the heart. In our body, it plays the role of a powerful pump, pumping oxygenated blood to tissues and cells. They, in turn, release blood filled with carbon dioxide, sending it through venules and veins back to the heart.
Passing through the right atrium, deoxygenated blood completes big circle. It begins in the right ventricle. Blood is pumped through it into It moves through the arteries, arterioles and capillaries, where it exchanges air with the alveoli to begin the cycle again.
Exchange in tissues
So, we know what gas exchange between the lungs and blood is. Both systems transport and exchange gases. But the key role belongs to fabrics. The main processes that change the chemical composition air.
Saturates cells with oxygen, which triggers a series of redox reactions in them. In biology they are called the Krebs cycle. For their implementation, enzymes are needed, which also come with the blood.
In the process, citric, acetic and other acids are formed, products for the oxidation of fats, amino acids and glucose. This is one of the most important stages, which accompanies gas exchange in tissues. During its course, the energy necessary for the functioning of all organs and systems of the body is released.
Oxygen is actively used to carry out the reaction. It gradually oxidizes, turning into carbon dioxide - CO 2, which is released from cells and tissues into the blood, then into the lungs and atmosphere.
Gas exchange in animals
The structure of the body and organ systems of many animals varies significantly. Mammals are the most similar to humans. Small animals, such as planaria, do not have complex systems for metabolism. They use their outer coverings to breathe.
Amphibians use their skin, mouth, and lungs to breathe. In most animals that live in water, gas exchange is carried out using gills. They are thin plates connected to capillaries and transport oxygen from water into them.
Arthropods, such as millipedes, woodlice, spiders, and insects, do not have lungs. They have tracheas across the entire surface of their body, which direct air directly to the cells. This system allows them to move quickly without experiencing shortness of breath and fatigue, because the process of energy formation occurs faster.
Exchange of gases in plants
Unlike animals, gas exchange in tissues of plants includes the consumption of both oxygen and carbon dioxide. They consume oxygen during respiration. Plants do not have special organs for this, so air enters them through all parts of the body.
As a rule, the leaves have the largest area, and the main amount of air falls on them. Oxygen enters them through small openings between cells, called stomata, is processed and excreted in the form of carbon dioxide, as in animals.
A distinctive feature of plants is their ability to photosynthesize. Thus, they can convert inorganic components into organic ones with the help of light and enzymes. During photosynthesis, carbon dioxide is absorbed and oxygen is produced, so plants are real “factories” for air enrichment.
Peculiarities
Gas exchange is one of the essential functions any living organism. It is carried out through breathing and blood circulation, promoting the release of energy and metabolism. The peculiarities of gas exchange are that it does not always proceed in the same way.
First of all, it is impossible without breathing; stopping it for 4 minutes can lead to disruptions in the functioning of brain cells. As a result of this, the body dies. There are many diseases in which gas exchange is impaired. Tissues do not receive enough oxygen, which slows down their development and function.
Uneven gas exchange is also observed in healthy people. It increases significantly with increased muscle work. In just six minutes he reaches maximum power and sticks to it. However, as the load increases, the amount of oxygen may begin to increase, which will also have an unpleasant effect on the body’s well-being.
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