Respiration is a complex of physiological processes that ensure the exchange of oxygen and carbon dioxide between the cells of the body and the external environment. It includes next steps:

1. External breathing or ventilation. This is the exchange of respiratory gases between atmospheric air and the alveoli.

2. Diffusion of gases in the lungs, i.e. their exchange between the air of the alveoli and the blood.

3. Transport of gases by blood.

4. Diffusion of gases in tissues. Exchange of gases between blood and intracellular fluid.

5. Cellular respiration. Absorption of oxygen and formation of carbon dioxide in cells.

The mechanism of external respiration.

External breathing occurs as a result of rhythmic movements of the chest. The respiratory cycle consists of the phases of inhalation (inspiratio) and exhalation (expiratio), between which there is no pause. At rest in an adult, the frequency breathing movements 16-20 per minute. Inhalation is an active process. With a calm inhalation, the external intercostal and intercartilaginous muscles contract. They raise the ribs and push the sternum forward. This leads to an increase in the sagittal and frontal dimensions of the thoracic cavity. At the same time, the muscles of the diaphragm contract. Its dome lowers, and the abdominal organs move down, to the sides and forward. Due to this, the chest cavity increases in the vertical direction. After the end of inhalation, the respiratory muscles relax. Exhalation begins. Calm exhalation is a passive process. During it, the chest returns to its original state. This happens under the influence of her own weight, tense ligamentous apparatus and pressure on the diaphragm of the abdominal organs. At physical activity, pathological conditions accompanied by shortness of breath (pulmonary tuberculosis, bronchial asthma etc.) forced breathing occurs. Accessory muscles are involved in the act of inhalation and exhalation. With forced inhalation, the sternocleidomastoid, scalene, pectoral and trapezius muscles additionally contract. They promote additional elevation of the ribs. With forced exhalation, the internal intercostal muscles contract, which enhance the lowering of the ribs, i.e. it is an active process. There are thoracic and abdominal types of breathing. In the first, breathing is mainly carried out by the intercostal muscles, in the second - by the muscles of the diaphragm. Chest or costal breathing is typical for women. Abdominal or diaphragmatic - for men. Physiologically, the abdominal type is more advantageous, because it is carried out with less energy consumption. In addition, the movement of the abdominal organs during breathing prevents their inflammatory diseases. Sometimes a mixed type of breathing occurs.

Despite the fact that the lungs are not fused with the chest wall, they repeat its movements. This is explained by the fact that there is a closed pleural fissure between them. From the inside, the wall of the chest cavity is covered with the parietal layer of the pleura, and the lungs with its visceral layer. There is a small amount of serous fluid in the interpleural fissure. When you inhale, the volume of the chest cavity increases, and since the pleural cavity is isolated from the atmosphere, the pressure in it decreases. The lungs expand, the pressure in the alveoli becomes lower than atmospheric pressure. Air enters the alveoli through the trachea and bronchi. During exhalation, the volume of the chest decreases. The pressure in the pleural fissure increases, air leaves the alveoli. Movements or excursions of the lungs are ensured by fluctuations in negative interpleural pressure. After a quiet exhalation, it is 4-6 mm Hg below atmospheric. At the height of a quiet inspiration at 8-9 mm Hg. After forced exhalation it is lower by 1-3 mm Hg, and after forced inspiration by 10-15 mm Hg. The presence of negative interpleural pressure is explained by elastic traction of the lungs. This is the force with which the lungs tend to contract towards the roots, counteracting atmospheric pressure. It is due to the elasticity of the lung tissue, which contains many elastic fibers. In addition, elastic traction increases the surface tension of the alveoli. From the inside they are covered with a film of surfactant. This is a lipoprotein produced by mitochondria of the alveolar epithelium. Due to the special structure of its molecules, during inhalation it increases the surface tension of the alveoli, and on exhalation, when their size decreases, on the contrary, it decreases. This prevents the alveoli from collapsing, i.e. the occurrence of atelectasis. With genetic pathology, the production of surfactant is disrupted in some newborns. Atelectasis occurs and the child dies. In old age, as well as in some chronic lung diseases, the number of elastic fibers increases. This phenomenon is called pulmonary fibrosis. Breathing excursions become difficult. With emphysema, elastic fibers, on the contrary, are destroyed, and the elastic thrust of the lungs decreases. The alveoli swell, and the amount of lung excursion also decreases. When air enters the pleural cavity, pneumothorax occurs. There are the following types:

1. According to the mechanism of occurrence: pathological (lung cancer, abscess, penetrating chest injury) and artificial (treatment of tuberculosis).

2. Depending on which layer of the pleura is damaged, external and internal pneumothorax are distinguished.

3. According to the degree of communication with the atmosphere, open pneumothorax is distinguished, when the pleural cavity is constantly communicating with the atmosphere. Closed if there is a single entry of air. Valvular, when when you inhale, air from the atmosphere enters the pleural fissure, and when you exhale, the hole closes.

4. Depending on the side of the injury - unilateral (right-sided, left-sided), bilateral.

Pneumothorax is a life-threatening complication. As a result, the lung collapses and is switched off from breathing. Valvular pneumothorax is especially dangerous.

Ticket 22

23. Hormonal regulation of calcium metabolism in the body. Parathyroid hormones, calcitonin, calcitriol, their functions

Simultaneously with the mechanism provided by the existence of exchangeable calcium salts in the bones, which acts as a buffer system in relation to the concentration of calcium ions in the intercellular fluid, both hormones (parathyroid hormone and calcitonin) begin to act within 3-5 minutes after a rapid change in the concentration of calcium ions. The rate of PTH secretion increases; as already explained, this sets into motion numerous mechanisms aimed at reducing the concentration of calcium ions. Simultaneously with the decrease in PTH concentration, the concentration of calcitonin increases in young animals and, probably, in small children (and in adults, but to a lesser extent). Calcitonin causes a rapid entry of calcium into the bones, and possibly also into many cells of other tissues, so in very young animals, excess calcitonin may cause the high concentration of calcium ions to return to normal much more quickly than buffering alone can do. a system mediated by the mechanism of easily exchangeable calcium salts. In the case of long-term calcium excess or deficiency, only the effects of PTH are truly important in normalizing the concentration of calcium ions in the plasma. In cases of long-term dietary calcium deficiency, PTH can often stimulate the release of calcium from bones in quantities sufficient to maintain normal plasma concentrations for one year, but it is clear that even this source of calcium can become depleted. Based on the detectable effect, bone can be considered a buffer reserve of calcium, which is controlled by parathyroid hormone. If the bones as a source of calcium are depleted or, on the contrary, are overfilled with calcium, PTH and vitamin D will act as a long-term mechanism that controls the concentration of calcium in the extracellular fluid, regulating the absorption of calcium in the intestine and its excretion in the urine.

If the parathyroid glands do not secrete a sufficient amount of parathyroid hormone, this leads to a decrease in the leaching of easily exchangeable calcium from the bones by osteocytes with almost complete and widespread inactivation of osteoclasts. As a result, the absorption of calcium from the bones is so reduced that it leads to a decrease in the level of calcium in body fluids. Because calcium and phosphate are no longer washed out of the bones, the bones usually remain strong.

Calcitonin- a peptide hormone consisting of 12 amino acids, the physiological function of which is to regulate the metabolism of calcium and phosphorus. Interest in this hormone is explained, first of all, by its participation in ensuring a relatively constant level of calcium.
The main and direct factor that acts on the thyroid gland and activates the synthesis of calcitonin secretion. there is a concentration of calcium in the serum of the crop. An increase in the level of calcium in the blood, especially its ionized form, increases the secretion of calcitonin, and a decrease inhibits it.
The indirect pathway for regulating the secretion of calcitonin is associated with the secretion of gastrin and some other entohormones. A decrease in calcium levels in the digestive tract promotes the secretion of gastrin, which, in turn, leads to increased synthesis and release of calcitonin by the thyroid gland.
Calcitonin acts on cAMP through specific receptors (in bones, kidneys). As a result, first of all, bone resorption is inhibited and their mineralization is stimulated. In particular, it is manifested by a decrease in the level of calcium and phosphorus in the blood serum and the excretion of hydroxyproline.

Parathyroid hormone (PGT) is a functional antagonist of calcitonin: the first ensures an increase in calcium composition, and the second - its decrease. A low concentration of calcium in the blood plasma stimulates the release of a significant amount of PTH into the blood. which increases the reabsorption of calcium in the kidney tubules and the secretion of phosphates, and in bone tissue - accelerates the process of resorption and release of calcium into the intercellular space.
At the cellular level, calcitonin affects the transport of calcium across its membrane. It stimulates the uptake of calcium by mitochondria and thereby delays the outflow of calcium from cells. This process is associated with the activity of adenosine triphosphoric acid (ATP) of the cell membrane and depends on the ratio of sodium and potassium. Calcitonin affects the organic composition of bone: it inhibits the breakdown of collagen, which is manifested by a decrease in urinary excretion of hydroxyproline

Biomechanics of breathing. Biomechanics of inspiration.

Parameter name	Meaning
Article topic:	Biomechanics of breathing. Biomechanics of inspiration.
Rubric (thematic category)	Medicine

Rice. 10.1. The effect of contraction of the diaphragmatic muscle on the volume of the thoracic cavity. Contraction of the diaphragmatic muscle during inhalation (dashed line) causes the diaphragm to move downward, displacing the abdominal organs downward and forward. As a result, the volume of the chest cavity increases.

Increase in volume of the chest cavity during inhalation occurs as a result of contraction of inspiratory muscles: the diaphragm and external intercostal muscles. The main respiratory muscle is the diaphragm, which is located in the lower third of the thoracic cavity and separates the thoracic and abdominal cavities. When the diaphragmatic muscle contracts, the diaphragm moves downward and displaces the abdominal organs downward and anteriorly, increasing the volume of the thoracic cavity mainly vertically (Fig. 10.1).

Increased volume of the chest cavity during inhalation promotes contraction of the external intercostal muscles, which lift the chest upward, increasing the volume of the chest cavity. This effect of contraction of the external intercostal muscles is due to the peculiarities of the attachment of muscle fibers to the ribs - the fibers go from top to bottom and from back to front (Fig. 10.2). With a similar direction of the muscle fibers of the external intercostal muscles, their contraction rotates each rib around an axis passing through the points of articulation of the rib head with the body and transverse process of the vertebra. As a result of this movement, each underlying costal arch rises upward more than the one above it descends. The simultaneous upward movement of all costal arches leads to the fact that the sternum rises upward and anteriorly, and the volume of the chest increases in the sagittal and frontal planes. Contraction of the external intercostal muscles not only increases the volume of the chest cavity, but also prevents the chest from descending downwards. For example, in children with undeveloped intercostal muscles, rib cage decreases in size during contraction of the diaphragm (paradoxical movement).

Rice. 10.2. Direction of the fibers of the external intercostal muscles and an increase in the volume of the thoracic cavity during inhalation. a - contraction of the external intercostal muscles during inhalation raises the lower rib more than lowers the upper one. As a result, the costal arches rise upward and increase (b) the volume of the thoracic cavity in the sagittal and frontal plane.

When breathing deeply biomechanism of inhalation, as a rule, auxiliary respiratory muscles are involved - sternocleidomastoid and anterior scalene muscles, and their contraction further increases the volume of the chest. Specifically, the scalene muscles elevate the upper two ribs, and the sternocleidomastoid muscles elevate the sternum. Inhalation is an active process and requires the expenditure of energy during contraction of the inspiratory muscles, which is spent on overcoming the elastic resistance of the relatively rigid tissues of the chest, the elastic resistance of the easily extensible lung tissue, the aerodynamic resistance of the respiratory tract to the air flow, as well as the increase in intra-abdominal pressure and the resulting displacement abdominal organs downwards.

Exhale at rest in humans, it is carried out passively under the influence of elastic traction of the lungs, which returns the volume of the lungs to its original value. However, during deep breathing, as well as when coughing and sneezing, exhalation must be active, and the decrease in the volume of the chest cavity occurs due to contraction of the internal intercostal muscles and abdominal muscles. Muscle fibers The internal intercostal muscles run relative to the points of their attachment to the ribs from bottom to top and from back to front. When they contract, the ribs rotate around an axis passing through the points of their articulation with the vertebra, and each superior costal arch moves downward more than the underlying one rises upward. As a result, all the costal arches, together with the sternum, move down, reducing the volume of the thoracic cavity in the sagittal and frontal planes.

When a person breathes deeply, the abdominal muscles contract in expiratory phase increases pressure in the abdominal cavity, which promotes the upward displacement of the dome of the diaphragm and reduces the volume of the chest cavity in the vertical direction.

Contraction of the respiratory muscles of the chest and diaphragm during inhalation causes increase in lung capacity, and when they relax during exhalation, the lungs collapse to their original volume. The volume of the lungs, both during inhalation and exhalation, changes passively, since, due to their high elasticity and extensibility, the lungs follow changes in the volume of the chest cavity caused by contraction of the respiratory muscles. This position is illustrated by the following model of passive increasing lung capacity(Fig. 10.3). In this model, the lungs are considered as an elastic balloon placed inside a container made of rigid walls and a flexible diaphragm. The space between the elastic balloon and the walls of the container is sealed. This model allows you to change the pressure inside the container by moving the flexible diaphragm down. As the volume of the container increases, caused by the downward movement of the flexible diaphragm, the pressure inside the container, i.e., outside the container, becomes lower than atmospheric pressure in accordance with the ideal gas law. The balloon inflates because the pressure inside it (atmospheric) becomes higher than the pressure in the container around the balloon.

Rice. 10.3. Schematic of a model demonstrating passive inflation of the lungs as the diaphragm descends. When the diaphragm is lowered, the air pressure inside the container becomes below atmospheric pressure, which causes the elastic balloon to inflate. P - atmospheric pressure.

Applied to human lungs, which completely fill chest cavity volume, their surface and the inner surface of the chest cavity are covered with a pleural membrane. The pleural membrane on the surface of the lungs (visceral pleura) is not physically in contact with the pleural membrane covering the chest wall (parietal pleura), because between these membranes there is pleural space(synonym - intrapleural space), filled with a thin layer of fluid - pleural fluid. This fluid moisturizes the surface of the lung lobes and promotes their sliding relative to each other during lung inflation, and also facilitates friction between the parietal and visceral layers of the pleura. The liquid is incompressible and its volume does not increase with decreasing pressure in pleural cavity. For this reason, highly elastic lungs exactly repeat the change in the volume of the chest cavity during inhalation. Bronchi, blood vessels, nerves and lymphatic vessels form the root of the lung, with the help of which the lungs are fixed in the mediastinum. The mechanical properties of these tissues determine the main degree of force, and the respiratory muscles must develop during contraction in order to cause increase in lung capacity. Under normal conditions, the elastic traction of the lungs creates an insignificant amount of negative pressure in a thin layer of fluid in the intrapleural space relative to atmospheric pressure. Negative intrapleural pressure varies according to the phases of the respiratory cycle from -5 (exhalation) to -10 cm aq. Art. (inhalation) below atmospheric pressure (Fig. 10.4). Negative intrapleural pressure can cause a decrease (collapse) in the volume of the chest cavity, which the chest tissue counteracts with its extremely rigid structure. The diaphragm, compared to the chest, is more elastic, and its dome rises under the influence of the pressure gradient existing between the pleural and abdominal cavities.

In a state where the lungs do not expand or collapse (a pause after inhalation or exhalation, respectively), there is no air flow in the respiratory tract and the pressure in the alveoli is equal to atmospheric pressure. In this case, the gradient between atmospheric and intrapleural pressure will exactly balance the pressure developed by the elastic traction of the lungs (see Fig. 10.4). Under these conditions, the value of intrapleural pressure is equal to the difference between the pressure in the respiratory tract and the pressure developed by the elastic traction of the lungs. For this reason, the more the lungs are stretched, the stronger the elastic traction of the lungs will be and the more negative the value of intrapleural pressure relative to atmospheric pressure will be. This happens during inhalation, when the diaphragm moves down and the elastic traction of the lungs counteracts the inflation of the lungs, and the intrapleural pressure becomes more negative. During inhalation, this negative pressure forces air through the respiratory tract towards the alveoli, overcoming airway resistance. As a result, air enters the alveoli from the external environment.

Rice. 10.4. Pressure in the alveoli and intrapleural pressure during the inhalation and exhalation phases of the respiratory cycle. In the absence of air flow in the respiratory tract, the pressure in them is equal to atmospheric pressure (A), and the elastic traction of the lungs creates pressure E in the alveoli. Under these conditions, the value of intrapleural pressure is equal to the difference A - E. When inhaling, contraction of the diaphragm increases the amount of negative pressure in the pleural space cavities up to -10 cm aq. Art., ĸᴏᴛᴏᴩᴏᴇ helps to overcome resistance to air flow in the respiratory tract, and air moves from the external environment into the alveoli. The magnitude of intrapleural pressure is determined by the difference between pressures A - R - E. When exhaling, the diaphragm relaxes and intrapleural pressure becomes less negative relative to atmospheric pressure (-5 cm water column). The alveoli, due to their elasticity, reduce their diameter, and the pressure E in them increases. The pressure gradient between the alveoli and the external environment facilitates the removal of air from the alveoli through the respiratory tract into the external environment. The value of intrapleural pressure is determined by the sum of A + R minus the pressure inside the alveoli, i.e. A + R - E. A - atmospheric pressure, E - pressure in the alveoli arising due to elastic traction of the lungs, R - pressure ensuring overcoming resistance to air flow in the respiratory tract, P - intrapleural pressure.

When you exhale, the diaphragm relaxes and the intrapleural pressure becomes less negative. Under these conditions, the alveoli, due to the high elasticity of their walls, begin to decrease in size and push air out of the lungs through the respiratory tract. The airway's resistance to airflow maintains positive pressure in the alveoli and prevents their rapid collapse. However, in a calm state during exhalation, the flow of air in the respiratory tract is due only to the elastic traction of the lungs.

Pneumothorax. If air enters the intrapleural space, for example through a wound opening, a collapse occurs in the lungs, the chest increases slightly in volume, and the diaphragm moves down as soon as the intrapleural pressure becomes equal to atmospheric pressure. This condition is usually called pneumothorax, in which the lungs lose the ability to follow changes in volume of the chest cavity during breathing movements. Moreover, during inhalation, air enters the chest cavity through the wound opening and exits during exhalation without changing the volume of the lungs during respiratory movements, which makes gas exchange between the external environment and the body impossible.

External respiration process is caused by changes in the volume of air in the lungs during the inhalation and exhalation phases of the respiratory cycle. During quiet breathing, the ratio of the duration of inhalation to exhalation in the respiratory cycle is on average 1:1.3. External breathing of a person is characterized by the frequency and depth of respiratory movements. Respiration rate a person is measured by the number of respiratory cycles within 1 minute and its value at rest in an adult varies from 12 to 20 per 1 minute. This indicator of external respiration increases with physical work, increasing ambient temperature, and also changes with age. For example, in newborns the respiratory rate is 60-70 per 1 min, and in people aged 25-30 years - an average of 16 per 1 min. The depth of breathing is determined by the volume of air inhaled and exhaled during one respiratory cycle. The product of the frequency of respiratory movements and their depth characterizes the basic value of external respiration - ventilation. A quantitative measure of lung ventilation is the minute volume of respiration - this is the volume of air that a person inhales and exhales in 1 minute. The minute volume of a person's breathing at rest varies between 6-8 liters. During physical work, a person's minute breathing volume can increase 7-10 times.

Rice. 10.5. Volumes and capacities of air in the lungs and a curve (spirogram) of changes in air volume in the lungs during quiet breathing, deep inhalation and exhalation. FRC - functional residual capacity.

Pulmonary air volumes. IN respiratory physiology A unified nomenclature has been adopted for pulmonary volumes in humans, which fill the lungs during quiet and deep breathing during the inhalation and exhalation phases of the respiratory cycle (Fig. 10.5). The pulmonary volume that is inhaled or exhaled by a person during quiet breathing is usually called tidal volume. Its value during quiet breathing averages 500 ml. Maximum quantity air that a person can inhale in excess of the tidal volume is usually called inspiratory reserve volume(average 3000 ml). The maximum amount of air that a person can exhale after a quiet exhalation is usually called the expiratory reserve volume (on average 1100 ml). Finally, the amount of air that remains in the lungs after maximum exhalation is usually called residual volume, its value is approximately 1200 ml.

The sum of the values ​​of two lung volumes and more commonly called pulmonary capacity. Air volume in human lungs it is characterized by inspiratory lung capacity, vital lung capacity and functional residual lung capacity. The inspiratory capacity of the lungs (3500 ml) is the sum of the tidal volume and the inspiratory reserve volume. Vital capacity of the lungs(4600 ml) includes tidal volume and inspiratory and expiratory reserve volumes. Functional residual lung capacity(1600 ml) is the sum of expiratory reserve volume and residual lung volume. Sum vital capacity of the lungs And residual volume It is commonly called the total lung capacity, the average value of which in humans is 5700 ml.

When inhaling, the human lungs due to contraction of the diaphragm and external intercostal muscles, they begin to increase their volume from the level, and its value during quiet breathing is tidal volume, and with deep breathing - reaches different values reserve volume inhale. When exhaling, the volume of the lungs returns to the original level of functional function. residual capacity passively, due to elastic traction of the lungs. If air begins to enter the volume of exhaled air functional residual capacity, which occurs during deep breathing, as well as when coughing or sneezing, then exhalation is carried out due to muscle contraction abdominal wall. In this case, the value of intrapleural pressure, as a rule, becomes higher than atmospheric pressure, which determines the highest speed of air flow in the respiratory tract.

When inhaling, the increase in the volume of the chest cavity is prevented elastic traction of the lungs, the movement of the rigid chest, the abdominal organs and, finally, the resistance of the airways to the movement of air towards the alveoli. The first factor, namely the elastic traction of the lungs, to the greatest extent prevents the increase in lung volume during inspiration.

Biomechanics of breathing. Biomechanics of inspiration. - concept and types. Classification and features of the category "Biomechanics of breathing. Biomechanics of inhalation." 2017, 2018.

Forced inhalation.

Transport of substances in the gastrointestinal tract.

Oral cavity– essential oils in small quantities.

Stomach– water, alcohol, mineral salts, monosaccharides.

Duodenum– monomers, liquid crystals.

Jejunum– up to 80% monomers.

In the upper section– monosaccharides, amino acids, fatty acids.

In the lower section- water, salt.

3. Biomechanics of inhalation and exhalation. Overcoming forces when inhaling. Primary pulmonary volumes and capacities

Respiration is a set of processes resulting in the consumption of O 2, the release of CO 2 and the conversion of energy chemicals into biologically useful forms.

Stages of the respiratory process.

1) Ventilation.

2) Diffusion of gas in the lungs.

3) Transport of gases.

4) Exchange of gases in tissues.

5) Tissue respiration.

Biomechanics of active inspiration. Inhalation (inspiration) is an active process.

When you inhale, the chest expands in three directions:

1) in vertical- due to contraction of the diaphragm and lowering of its tendon center. At the same time they move down internal organs;

2) in the sagittal direction – associated with contraction of the external intercostal muscles and movement of the end of the sternum forward;

3) in the frontal– the ribs move upward and outward due to contraction of the external intercostal and intercartilaginous muscles.

1) Provided by increased contraction of inspiratory muscles (external intercostal muscles and diaphragm).

2) Contraction of auxiliary muscles:

a) extension thoracic region spine and fixing and abducting shoulder girdle back - trapezoid, rhomboid, levator scapulae, pectoralis minor and major, serratus anterior;

b) levator ribs.

During forced inspiration, the reserve of the pulmonary system is used.

Inhalation is an active process, because when inhaling, the following forces are overcome:

1) elastic resistance of muscles and lung tissue (a combination of stretching and elasticity).

2) inelastic resistance - overcoming the frictional force when moving the ribs, resistance of internal organs to the diaphragm, heaviness of the ribs, resistance to air movement in the bronchi of medium diameter. Depends on the tone of the bronchial muscles (10–20 mm Hg in adults, healthy people). It can increase up to 100mm with bronchospasm and hypoxia.

The process of inhalation.

When inhaling, the volume of the chest increases, the pressure in the pleural fissure increases from 6 mm Hg. Art. increases to – 9, and with a deep breath – to 15 – 20 mm Hg. Art. This is negative pressure (i.e. below atmospheric pressure).

The lungs passively expand, the pressure in them becomes 2 - 3 mm below atmospheric pressure and air enters the lungs.

There was an inhalation.

Passive process. When the inhalation is completed, the respiratory muscles are relaxed, under the influence of gravity the ribs lower, and the internal organs return the diaphragm to its place. The volume of the chest decreases, passive exhalation occurs. The pressure in the lungs is 3–4 mm higher than atmospheric pressure.

During forced exhalation, the internal intercostal muscles, the flexor muscles of the spine and the abdominal muscles are involved.

Role of surfactant.

This is a phospholipid substance produced by granular pneumocytes. The stimulus for its production is deep breaths.

During inhalation, surfactant is distributed over the surface of the alveoli with a film 10–20 µm thick. This film prevents the alveoli from collapsing during exhalation, since the surfactant during inhalation increases the surface tension forces of the layer of liquid lining the alveoli.

When exhaling, it reduces them.

Pneumothorax– air entering the pleural fissure.

Open;

Closed;

Unilateral;

Bilateral.

Thoracic and abdominal type of breathing.

More effective than abdominal, because intra-abdominal pressure increases and the return of blood to the heart increases.

4. Methods for studying human reflexes: tendon (knee, Achilles), Aschner, pupillary.

Ticket No. 4

1. Principles of coordination of reflex activity: relationships between excitation and inhibition, principle feedback, the principle of dominance.

Coordination is ensured by selective excitation of some centers and inhibition of others. Coordination is the unification of the reflex activity of the central nervous system into a single whole, which ensures the implementation of all functions of the body. The following basic principles of coordination are distinguished:

The principle of irradiation of excitations. Neurons of different centers are interconnected by interneurons, so impulses arriving during strong and prolonged stimulation of receptors can cause excitation not only of the neurons of the center of a given reflex, but also of other neurons. Irradiation of excitation ensures inclusion in the response during strong and biologically significant stimuli more motor neurons.

The principle of a common final path. Impulses arriving in the central nervous system through different afferent fibers can converge (converge) to the same intercalary, or efferent, neurons. The same motor neuron can be excited by impulses coming from different receptors (visual, auditory, tactile), i.e. participate in many reflex reactions (be included in various reflex arcs).

The principle of dominance. It was discovered by A.A. Ukhtomsky, who discovered that irritation of the afferent nerve (or cortical center), usually leading to contraction of the muscles of the limbs when the animal’s intestines are full, causes an act of defecation. In this situation, the reflex excitation of the defecation center suppresses and inhibits the motor centers, and the defecation center begins to react to signals that are foreign to it.

A.A. Ukhtomsky believed that in every at the moment life, a defining (dominant) focus of excitation arises, subordinating the activity of all nervous system and the determining nature of the adaptive reaction. Excitations from various areas of the central nervous system converge to the dominant focus, and the ability of other centers to respond to signals coming to them is inhibited. Thanks to this, conditions are created for the formation of a certain reaction of the body to the stimulus that has the greatest biological significance, i.e. satisfying a vital need.

Under natural conditions of existence, dominant excitation can cover entire systems of reflexes, resulting in food, defensive, sexual and other forms of activity. The dominant excitation center has a number of properties:

1) its neurons are characterized by high excitability, which promotes the convergence of excitations from other centers to them;

2) its neurons are able to summarize incoming excitations;

3) excitement is characterized by persistence and inertia, i.e. the ability to persist even when the stimulus that caused the formation of the dominant has ceased to act.

4. Feedback principle. The processes occurring in the central nervous system cannot be coordinated if there is no feedback, i.e. data on the results of function management. Feedback allows you to correlate the severity of changes in system parameters with its operation. The connection between a system's output and its input with a positive gain is called positive feedback, and with a negative gain is called negative feedback. Positive feedback is mainly characteristic of pathological situations.

Negative feedback ensures the stability of the system (its ability to return to its original state after the influence of disturbing factors ceases). There are fast (nervous) and slow (humoral) feedbacks. Feedback mechanisms ensure the maintenance of all homeostasis constants.

5. The principle of reciprocity. It reflects the nature of the relationship between the centers responsible for the implementation of opposite functions (inhalation and exhalation, flexion and extension of the limbs), and lies in the fact that the neurons of one center, when excited, inhibit the neurons of the other and vice versa.

6. The principle of subordination (subordination). The main trend in the evolution of the nervous system is manifested in the concentration of regulation and coordination functions in the higher parts of the central nervous system - cephalization of the functions of the nervous system. There are hierarchical relationships in the central nervous system - the highest center of regulation is the cerebral cortex, the basal ganglia, middle, medulla and spinal cord obey its commands.

7. The principle of compensation of functions. The central nervous system has a huge compensatory capacity, i.e. can restore some functions even after the destruction of a significant part of the neurons that form the nerve center (see plasticity of nerve centers). If individual centers are damaged, their functions can transfer to other brain structures, which is carried out with the obligatory participation of the cerebral cortex. In animals in which the cortex was removed after restoration of lost functions, their loss occurred again.

With a local insufficiency of inhibitory mechanisms or with an excessive increase in excitation processes in a particular nerve center, a certain set of neurons begins to autonomously generate pathologically enhanced excitation - a generator of pathologically enhanced excitation is formed.

At high generator power, a whole system of nonironal formations functioning in a single mode appears, which reflects a qualitatively new stage in the development of the disease; tight connections between individuals constituent elements Such a pathological system underlies its resistance to various therapeutic influences. Its essence is that the structure of the central nervous system, which forms the functional premise, subjugates those parts of the central nervous system to which it is addressed and forms a pathological system with them, determining the nature of its activity. Such a system is biologically negative. If, for one reason or another, the pathological system disappears, then the formation of the central nervous system, which played main role, loses its determinant meaning.

2. Digestion in the oral cavity and swallowing (its phases). Reflex regulation of these acts

Search Lectures

The respiratory muscles are the “engine” of ventilation. Quiet and forced breathing differ in many respects, including the number of respiratory muscles performing breathing movements. Distinguish inspiratory(responsible for inhalation) and expiratory(responsible for exhalation) muscles. The respiratory muscles are also divided into basic And auxiliary. TO main inspiratory muscles include: a) diaphragm; b) external intercostal muscles; c) internal intercartilaginous muscles.

Fig. 4. Mechanism of respiratory movements (change in chest volume) due to the diaphragm and muscles abdominals(A) and contraction of the external intercostal muscles (B) (on the left - a model of rib movement)

During quiet breathing, 4/5 of inspiration is carried out by the diaphragm. The contraction of the muscular part of the diaphragm, transmitted to the tendon center, leads to a flattening of its dome and an increase in the vertical dimensions of the thoracic cavity. During quiet breathing, the dome of the diaphragm lowers by about 2 cm. The internal intercostal and intercartilaginous muscles are involved in raising the ribs. They run obliquely from rib to rib posteriorly and superiorly, anteriorly and inferiorly (dorsocranial and ventrocaudal). Due to their contraction, the lateral and saggital dimensions of the chest increase. During quiet breathing, exhalation occurs passively with the help of elastic return forces (just as a stretched spring itself returns to starting position).

During forced breathing, the main inspiratory muscles are attached auxiliary: pectoralis major and minor, scalene, sternocleidomastoid, trapezoid.

Fig.5. The most important accessory inspiratory muscles (A) and accessory expiratory respiratory muscles (B)

In order for these muscles to participate in the act of inhalation, it is necessary that their attachment sites be fixed. A typical example is the behavior of a patient with difficulty breathing. Such patients rest their hands on a stationary object, as a result of which the shoulders become fixed and the head tilts back.

Exhalation during forced breathing is ensured expiratory muscles: main– internal intercostal muscles and auxiliary- muscles of the abdominal wall (external and internal oblique, transverse, rectus).

Depending on whether the expansion of the chest during normal breathing is associated primarily with raising the ribs or flattening the diaphragm, they distinguish thoracic (costal) and abdominal types of breathing.

Security questions

1. What muscles are the main inspiratory and expiratory muscles?

2. What muscles are used to carry out a calm breath?

3. What muscles are classified as auxiliary inspiratory and expiratory muscles?

4. What muscles are used to perform forced breathing?

5. What are thoracic and abdominal types of breathing?

Breathing resistance

The respiratory muscles perform work equal to 1–5 J at rest, which overcomes breathing resistance and creates an air pressure gradient between the lungs and the external environment. During quiet breathing, only 1% of the oxygen consumed by the body is spent on the work of the respiratory muscles (the central nervous system consumes 20% of all energy). Energy consumption to ensure external respiration is insignificant, because:

1. when inhaling, the chest expands itself due to its own elastic forces and helps to overcome the elastic traction of the lungs;

2. the external link of the respiratory system works like a swing (a significant part of the energy of muscle contraction is converted into potential energy of elastic traction of the lungs)

3. little inelastic resistance to inhalation and exhalation

There are two types of resistance:

1) viscous inelastic resistance of tissues

2) elastic (elastic) resistance of the lungs and tissues.

Viscous inelastic resistance is due to:

— aerodynamic resistance of the airways

Viscous resistance of tissues

More than 90% of inelastic resistance occurs in aerodynamic airway resistance (occurs when air passes through a relatively narrow part of the respiratory tract - the trachea, bronchi and bronchioles). As the bronchial tree branches towards the periphery, the airways become increasingly narrow and it can be assumed that it is the narrowest branches that provide the greatest resistance to breathing. However, the total diameter towards the periphery increases, and the resistance decreases. Thus, at the level of generation 0 (trachea) the total cross-sectional area is about 2.5 cm2, at the level of terminal bronchioles (generation 16) - 180 cm2, respiratory bronchioles (from the 18th generation) - about 1000 cm2 and further >10,000 cm2. Therefore, airway resistance is mainly localized in the mouth, nose, pharynx, trachea, lobar and segmental bronchi until approximately the sixth generation of branching. Peripheral airways with a diameter of less than 2 mm account for less than 20% of respiratory resistance. It is these sections that have the greatest extensibility ( With -compliance).

Compliance, or extensibility (C) is a quantitative indicator characterizing the elastic properties of the lungs

C= D V/ D P

where C is the degree of extensibility (ml/cm water column); DV - change in volume (ml), DP - change in pressure (cm water column)

The total compliance of both lungs (C) in an adult is about 200 ml of air per 1 cm of water column. This means that with an increase in transpulmonary pressure (Ptp) by 1 cm of water column. Lung volume increases by 200 ml.

R= (RA-Rao)/V

where PA is alveolar pressure

Rao - pressure in the oral cavity

V – volumetric ventilation rate per unit time.

Alveolar pressure cannot be measured directly, but it can be inferred from pleural pressure. Pleural pressure can be determined by direct methods or indirectly by integral plethysmography.

Thus, the higher V, i.e. The harder we breathe, the higher the pressure difference should be at constant resistance. The higher, on the other hand, the airway resistance, the higher the pressure difference must be to obtain a given respiratory flow intensity. Inelastic breathing resistance depends on the lumen of the airways - especially the glottis and bronchi. The adductor and abductor muscles of the vocal folds, which regulate the width of the glottis, are controlled through the inferior laryngeal nerve by a group of neurons that are concentrated in the ventral region. respiratory group medulla oblongata. This proximity is not accidental: during inhalation, the glottis expands somewhat, and during exhalation it narrows, increasing resistance to air flow, which is one of the reasons for the longer duration of the expiratory phase. In the same way, the lumen of the bronchi and their patency change cyclically.

The tone of the smooth muscles of the bronchi depends on the activity of its cholinergic innervation: the corresponding efferent fibers pass as part of the vagus nerve.

Sympathetic (adrenergic) innervation, as well as the recently discovered “non-adrenergic inhibitory” system, have a relaxing effect on bronchial tone. The influence of the latter is mediated by certain neuropeptides, as well as microganglia found in the muscular wall of the airways; a certain balance between these influences helps to establish the optimal lumen of the tracheobronchial tree for a given speed of air flow.

Dysregulation of bronchial tone in humans forms the basis of bronchospasm , as a result of which the patency of the airways (obstruction) sharply decreases and breathing resistance increases. The cholinergic system of the vagus nerve is also involved in the regulation of mucus secretion and movements of the cilia of the ciliated epithelium of the nasal passages, trachea and bronchi, thereby stimulating mucociliary transport - release of foreign particles trapped in the airways. Excess mucus, characteristic of bronchitis, also creates obstruction and increases breathing resistance.

Elastic resistance of the lungs and tissues includes: 1) elastic forces of the lung tissue itself; 2) elastic forces caused by the surface tension of the layer of fluid on the inner surface of the walls of the alveoli and other airways of the lungs.

Collagen and elastic fibers woven into the lung parenchyma create elastic traction of the lung tissue. In collapsed lungs, these fibers are in an elastically contracted and twisted state, but when the lungs expand, they stretch and straighten, while lengthening and developing more and more elastic traction. The magnitude of tissue elastic forces causing the collapse of air-filled lungs is only 1/3 of the total elasticity of the lungs

At the interface between air and liquid, covering the alveolar epithelium with a thin layer, surface tension forces arise. Moreover, the smaller the diameter of the alveoli, the greater the surface tension force. On the inner surface of the alveoli, the fluid tends to contract and squeeze air from the alveoli to the bronchi, as a result of which the alveoli begin to collapse. If these forces acted unhindered, then, thanks to the anastomosis between the individual alveoli, air would pass from the small alveoli to the large ones, and the small alveoli themselves would have to disappear. To reduce surface tension and preserve the alveoli in the body, there is a purely biological adaptation. This - surfactants(surfactants) that act as a detergent.

Surfactant is a mixture that essentially consists of phospholipids (90-95%), including primarily phosphatidylcholine (lecithin). Along with this, it contains four surfactant-specific proteins, as well as a small amount of carbon hydrate. The total amount of surfactant in the lungs is extremely small. There is about 50 mm3 of surfactant per 1 m2 of alveolar surface. The thickness of its film is 3% of the total thickness of the airborne barrier. Surfactant is produced by type II alveolar epithelial cells. The surfactant layer reduces the surface tension of the alveoli by almost 10 times. The decrease in surface tension occurs due to the fact that the hydrophilic heads of these molecules bind tightly to water molecules, and their hydrophobic ends are very weakly attracted to each other and other molecules in solution. The repulsive forces of surfactant counteract the attractive forces of water molecules.

Surfactant functions:

1) stabilization of the size of the alveoli in extreme positions - on inhalation and exhalation

2) protective role: protects the walls of the alveoli from the damaging effects of oxidants, has bacteriostatic activity, provides reverse transport of dust and microbes through the airways, reduces the permeability of the pulmonary membrane (prevention of pulmonary edema).

Surfactants begin to be synthesized at the end of the prenatal period. Their presence makes it easier to take the first breath. During premature birth, the baby's lungs may not be prepared to breathe. Lack or defects of surfactant cause severe illness (respiratory distress syndrome). The surface tension in the lungs of such children is high, so many alveoli are in a collapsed state.

Security questions

1. Why is energy consumption to provide external respiration insignificant?

2. What types of resistance are there in the respiratory tract?

3. What causes viscous inelastic resistance?

4. What is extensibility, how to determine it?

5. What factors does viscous inelastic resistance depend on?

6. What determines the elastic resistance of the lungs and tissues?

7. What are surfactants, what functions do they perform?

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The mechanism of external respiration. Biomechanics of inhalation and exhalation.

External breathing represents the exchange of gases between the body and the external environment. It is carried out through two processes - pulmonary respiration and respiration through the skin.

Pulmonary respiration involves the exchange of gases between alveolar air and the environment and between alveolar air and capillaries. During gas exchange with the external environment, air enters containing 21% oxygen and 0.03-0.04% carbon dioxide, and exhaled air contains 16% oxygen and 4% carbon dioxide. Oxygen flows from atmospheric air into the alveolar air, and carbon dioxide is released in the opposite direction.

When exchanged with the capillaries of the pulmonary circulation in the alveolar air, the oxygen pressure is 102 mmHg. Art., and carbon dioxide - 40 mm Hg. Art., venous blood oxygen tension - 40 mm Hg. Art., and carbon dioxide - 50 mm Hg. Art. As a result of external respiration, arterial blood, rich in oxygen and poor in carbon dioxide, flows from the lungs.

External respiration is carried out as a result of the rhythmic movements of the difficult cell. The respiratory cycle consists of inhalation and exhalation phases, with no pause between them. At rest, an adult has a respiratory rate of 16-20 per minute.

Inhale is an active process. With a calm inhalation, the external intercostal and intercartilaginous muscles contract. They raise the ribs, and the sternum moves forward. This leads to an increase in the sagittal and frontal dimensions of the thoracic cavity. At the same time, the muscles of the diaphragm contract. its dome lowers, and the abdominal organs move down, to the sides and forward. Due to this, the chest cavity increases in the vertical direction.

After the end of inhalation, the respiratory muscles relax - the exhalation. Calm exhalation is a passive process.

During it, the chest returns to its original state under the influence of its own weight, tense ligamentous apparatus and pressure on the diaphragm of the abdominal organs. During physical exertion, pathological conditions accompanied by shortness of breath (pulmonary tuberculosis, bronchial asthma, etc.), forced breathing occurs. Accessory muscles are involved in the act of inhalation and exhalation. With forced inhalation, the sternocleidomastoid, scalene, pectoral and trapezius muscles additionally contract. They promote additional elevation of the ribs. With forced exhalation, the internal intercostal muscles contract, which increase the lowering of the ribs. Those. forced exhalation is an active process.

Pressure in the pleural cavity and its origin and role in the mechanism of external respiration. Changes in pressure in the pleural cavity during different phases of the respiratory cycle.

The pressure in the pleural cavity is always below atmospheric - negative pressure.

The amount of negative pressure in the pleural cavity:

• by the end of maximum exhalation - 1-2 mmHg. Art.,
• by the end of a quiet exhalation - 2-3 mmHg. Art.,
• by the end of a quiet inspiration - 5-7 mmHg. Art.,
• at the end of maximum inspiration - 15-20 mmHg. Art.

The growth rate of the chest is higher than that of the lung tissue. This leads to an increase in the volume of the pleural cavity, and since it is sealed, the pressure becomes negative.

Elastic traction of the lungs- the force with which the fabric tends to collapse.

Elastic traction of the lungs is due to :

1) surface tension of the liquid film covering inner surface alveoli;

2) the elasticity of the tissue of the walls of the alveoli due to the presence of elastic fibers in them;

3) tone of the bronchial muscles.

1. Biomechanics of inhalation and exhalation

Vital fluid and its components. Methods for their determination. Residual air.

The functioning of the external respiration apparatus can be judged by the volume of air entering the lungs during one respiratory cycle. The volume of air entering the lungs during maximum inspiration forms the total lung capacity. It is approximately 4.5-6 liters and consists of the vital capacity of the lungs and residual volume.

Vital capacity of the lungs- the amount of air that a person can exhale after a deep breath. It is one of the indicators physical development body and is considered pathological if it is 70-80% of the proper volume. During life, this value may change. This depends on a number of reasons: age, height, body position in space, food intake, physical activity, presence or absence of pregnancy.

The vital capacity of the lungs consists of tidal and reserve volumes. Tidal volume- this is the amount of air that a person inhales and exhales in a calm state. Its size is 0.3-0.7 liters. It maintains the partial pressure of oxygen and carbon dioxide in the alveolar air at a certain level. Inspiratory reserve volume is the amount of air that a person can additionally inhale after a quiet breath. As a rule, it is 1.5-2.0 liters. It characterizes the ability of lung tissue to undergo additional stretching. Expiratory reserve volume is the amount of air that can be exhaled following a normal exhalation.

Residual volume- a constant volume of air in the lungs even after maximum exhalation. It is about 1.0-1.5 liters.

An important characteristic of the respiratory cycle is the frequency of respiratory movements per minute. Normally it is 16-20 movements per minute. The duration of the respiratory cycle is calculated by dividing 60 s by the breathing frequency.

Entry and expiration times can be determined using a spirogram.

Lung volumes:

1. Tidal volume (TO) = 500 ml

2. Inspiratory reserve volume (IRV) = 1500-2500 ml

3. Expiratory reserve volume (ERV) = 1000 ml

4. Residual volume (VR) = 1000 -1500ml

Pulmonary capacities:

— total lung capacity (TLC) = (1+2+3+4) = 4-6 liters

— vital capacity of the lungs (VC) = (1+2+3) =3.5-5 liters

— functional residual capacity of the lungs (FRC) = (3+4) = 2-3 liters

— inhalation capacity (IV) = (1+2) = 2-3 liters

Minute volume of pulmonary ventilation and its changes under various loads, methods for its determination. “Harmful space” and effective pulmonary ventilation. Why rare and deep breathing is more effective.

Minute volume- the amount of air exchanged with the environment during quiet breathing. It is determined by the product of the tidal volume and the respiratory frequency and is 6-8 liters.

Its value, on average, is 500 ml, the respiratory rate per minute is 12-16 and, therefore, the minute volume of breathing, on average, is 6-8 liters.

However, not all air entering the respiratory system takes part in gas exchange. Some of the air fills the airways (larynx, trachea, bronchi, bronchioles) and does not reach the alveoli, since it leaves the body first when exhaling.

This air is called - air of harmful space. Its volume, on average, is 140-150 ml. Therefore, the concept of effective pulmonary ventilation is introduced. This is the amount of air in one minute that takes part in gas exchange. Effective pulmonary ventilation at the same minute volume of breathing can be different. So, the larger the tidal volume, the smaller the relative volume of air in the harmful space. Therefore, rare and deep breathing is more effective in supplying the body with oxygen, as ventilation of the alveoli increases.

Breathing, its main stages. Mechanisms of external respiration. Biomechanics of inhalation and exhalation.

Breathing is a complex continuous process, as a result of which the gas composition of the blood is constantly updated.

In the process of breathing, three parts are distinguished: external, or pulmonary respiration, gas transport by blood, and internal, or tissue, respiration.

Breathing is a set of physiological processes that ensure a continuous supply of oxygen to tissues, its use in oxidative reactions, as well as the removal from the body of carbon dioxide and partially water formed during metabolism. The respiratory system includes the nasal cavity, larynx, bronchi and lungs. Breathing consists of the following main stages:

external respiration, which ensures gas exchange between the lungs and the external environment;

gas exchange between alveolar air and venous blood flowing to the lungs;

transport of gases by blood; gas exchange between arterial blood and tissues;

tissue respiration.

External respiration is the exchange of gases between the body and the surrounding atmospheric air. It is carried out in two stages - the exchange of gases between atmospheric and alveolar air and gas exchange between the blood of the pulmonary capillaries and the alveolar air.

The external respiration apparatus includes the airways, lungs, pleura, chest skeleton and muscles, and the diaphragm. The main function of the external respiration apparatus is to provide the body with oxygen and relieve it of excess carbon dioxide. ABOUT functional state The external respiration apparatus can be judged by the rhythm, depth, frequency of breathing, the size of the lung volumes, the indicators of oxygen absorption and carbon dioxide release, etc.

Transport of gases is carried out by blood. It is provided by the difference in partial pressure (tension) of gases along their path: oxygen from the lungs to the tissues, carbon dioxide from the cells to the lungs.

Internal or tissue respiration can also be divided into two stages. The first stage is the exchange of gases between blood and tissues. The second is the consumption of oxygen by cells and the release of carbon dioxide by them (cellular respiration).

Inhale and exhale

Inhalation begins with contraction of the respiratory (respiratory) muscles.

The muscles whose contraction leads to an increase in the volume of the thoracic cavity are called inspiratory, and the muscles whose contraction leads to a decrease in the volume of the thoracic cavity are called expiratory. The main inspiratory muscle is the diaphragm muscle. Contraction of the diaphragm muscle leads to the fact that its dome is flattened, the internal organs are pushed down, which leads to an increase in the volume of the chest cavity in the vertical direction. Contraction of the external intercostal and intercartilaginous muscles leads to an increase in the volume of the thoracic cavity in the sagittal and frontal directions.

The lungs are covered with a serous membrane - the pleura, consisting of visceral and parietal layers. The parietal layer is connected to the chest, and the visceral layer is connected to the lung tissue. As the volume of the chest increases, as a result of contraction of the inspiratory muscles, the parietal layer will follow the chest. As a result of the appearance of adhesive forces between the layers of the pleura, the visceral layer will follow the parietal layer, and after them the lungs. This leads to an increase in negative pressure in the pleural cavity and to an increase in the volume of the lungs, which is accompanied by a decrease in pressure in them, it becomes below atmospheric pressure and air begins to enter the lungs - inhalation occurs.

Between the visceral and parietal layers of the pleura there is a slit-like space called the pleural cavity. The pressure in the pleural cavity is always below atmospheric pressure; it is called negative pressure. The magnitude of negative pressure in the pleural cavity is: at the end of maximum exhalation - 1-2 mm Hg. Art., by the end of a quiet exhalation - 2-3 mmHg. Art., by the end of a quiet inspiration -5-7 mmHg. Art., by the end of maximum inspiration - 15-20 mm Hg. Art.

Negative pressure in the pleural cavity is caused by the so-called elastic traction of the lungs - the force with which the lungs constantly strive to reduce their volume. Elastic traction of the lungs is due to two reasons:

Presence in the wall of the alveoli large quantity elastic fibers;

Surface tension of the film of liquid that covers the inner surface of the walls of the alveoli.

The substance covering the inner surface of the alveoli is called surfactant.

Biomechanics of exhalation

Surfactant has a low surface tension and stabilizes the condition of the alveoli, namely, when inhaling, it protects the alveoli from overstretching (surfactant molecules are located far from each other, which is accompanied by an increase in surface tension), and when exhaling, from collapse (surfactant molecules are located close to each other). friend, which is accompanied by a decrease in surface tension).

The value of negative pressure in the pleural cavity during the act of inspiration manifests itself when air enters the pleural cavity, i.e. pneumothorax. If a small amount of air enters the pleural cavity, the lungs partially collapse, but their ventilation continues. This condition is called closed pneumothorax. After some time, air is absorbed from the pleural cavity and the lungs expand.

If the tightness of the pleural cavity is violated, for example, with penetrating wounds of the chest or with rupture of lung tissue as a result of its damage by some disease, the pleural cavity communicates with the atmosphere and the pressure in it becomes equal to atmospheric pressure, the lungs collapse completely, and their ventilation stops. This type of pneumothorax is called open. Open bilateral pneumothorax is incompatible with life.

Partial artificial closed pneumothorax (introduction of a certain amount of air into the pleural cavity using a needle) is used for therapeutic purposes, for example, in tuberculosis, partial collapse of the affected lung promotes the healing of pathological cavities (cavities).

When breathing deeply, a number of auxiliary respiratory muscles are involved in the act of inhalation, which include: muscles of the neck, chest, and back. The contraction of these muscles causes movement of the ribs, which assists the inspiratory muscles.

During quiet breathing, inhalation is active and exhalation is passive. Forces that ensure a calm exhalation:

Chest gravity;

Elastic traction of the lungs;

Abdominal pressure;

Elastic traction of costal cartilages twisted during inspiration.

The internal intercostal muscles, the posterior inferior serratus muscle, and the abdominal muscles take part in active exhalation.

Biomechanics of quiet inhalation and exhalation

Biology and genetics

Biomechanics of quiet inhalation and exhalation Biomechanics of quiet inhalation In the development of quiet inhalation, a role is played by: contraction of the diaphragm and contraction of the external oblique intercostal and intercartilaginous muscles. Under the influence of a nerve signal, the diaphragm is most strong muscle Inhalation contracts; the muscles are located radially in relation to the tendon center; therefore, the dome of the diaphragm flattens by 1520 cm; with deep breathing, the pressure in the abdominal cavity increases by 10 cm. Under the influence of a nerve signal, the external oblique intercostal and intercartilaginous muscles contract. U...

69. Biomechanics of quiet inhalation and exhalation...

Biomechanics of quiet inspiration

The following play a role in the development of quiet inhalation:contraction of the diaphragm and contraction of the external oblique intercostal and intercartilaginous muscles.

Under the influence of a nerve signal aperture / the strongest inspiratory muscle/contracts, her muscles are locatedradial to the tendon center, so the diaphragm domeflattens by 1.5-2.0 cm, with deep breathing - by 10 cm, pressure in the abdominal cavity increases.The size of the chest increases in vertical dimension.

Under the influence of a nerve signal they contractexternal oblique intercostal and interchondral muscles. U muscle fiberplace of its attachment tothe underlying rib further away from the spine than its place attachment to the overlying rib, That's why the moment of force of the underlying rib during contraction of this muscle is always greater than that of the overlying rib.This leads to the fact thatthe ribs seem to rise, and the thoracic cartilaginous ends seem to curl slightly. Because when exhaling, the thoracic ends of the ribs are located lowerthan vertebrates /arch at an angle/, then contraction of the external intercostal musclesbrings them to a more horizontal position, the chest circumference increases, the sternum rises and comes forward, the intercostal distance increases. Rib cage not only rises, but alsoincreases its sagittal and frontal dimensions. Due to contraction of the diaphragm, external oblique intercostal and intercartilaginous muscles increases the volume of the chest. The movement of the diaphragm accounts for approximately 70-80% of the ventilation of the lungs.

Rib cage lined from the insideparietal layer of pleura, with which it is firmly fused. Lung covered visceral layer of pleura, with which it is also firmly fused. Under normal conditions, the layers of the pleura fit tightly to each other and canslide / due to the secretion of mucus/ relative to each other. The adhesion forces between them are great and the layers of the pleura cannot be separated.

When inhaling parietal pleurafollows the expanding chest, pulls alongvisceral layerand he stretches lung tissue , which leads to an increase in their volume. Under these conditions, the air in the lungs /alveoli/ is distributed in a new, larger volume, which leads to a drop in pressure in the lungs. There is a pressure difference between the environment and the lungs /transrespiratory pressure/.

Transrespiratory pressure(R trr ) is the difference between the pressure in the alveoli (P alv) and external /atmospheric/ pressure (P ext). R trr = R alv. - P external,. Equal to inhalation - 4 mm Hg. Art.This difference makes you entera portion of air through the airways into the lungs. This is inhalation.

Biomechanics of quiet expiration

Calm exhalation is carried out passively , i.e. no muscle contraction occurs, and the chest collapses due to the forces that arose during inhalation.

Causes of exhalation:

1. Heaviness of the chest. Raised ribs are lowered by gravity.

2. The organs of the abdominal cavity, pushed down by the diaphragm during inhalation, raise the diaphragm.

3. Elasticity of the chest and lungs. Due to them, the chest and lungs take their original position

Transrespiratoryend expiratory pressure is=+ 4 mmHg

Biomechanics of forced inspiration

Forced inspiration is carried out due to the participation extra muscles. In addition to the diaphragm and external oblique intercostal muscles, it involves the neck muscles, spinal muscles, scapular muscles, and serratus muscles.

Biomechanics of forced expiration

Forced expiration is active. It is carried out by contracting muscles - internal oblique intercostal muscles, abdominal muscles.

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