Sinusitis

Pressure in the pleural cavity and its change during breathing. Pleural cavity - structure and functions The pressure in the pleural cavity is

a physical quantity characterizing the state of the contents of the pleural cavity. This is the amount by which the pressure in the pleural cavity is lower than atmospheric pressure ( negative pressure); with quiet breathing it is equal to 4 mm Hg. Art. at end expiration and 8 mmHg. Art. at the end of the inhalation. Created by surface tension forces and elastic traction of the lung

Rice. 12.13. Pressure changes during inhalation and exhalation

INHALE(inspiration) is the physiological act of filling the lungs with atmospheric air. It is carried out thanks to the active activity of the respiratory center and respiratory muscles, which increases the volume of the chest, resulting in a decrease in pressure in the pleural cavity and alveoli, which leads to the entry of environmental air into the trachea, bronchi and respiratory zones of the lung. Occurs without the active participation of the lungs, since there are no contractile elements in them

EXHALATION(expiration) is the physiological act of removing from the lung part of the air that takes part in gas exchange. First, the air of the anatomical and physiological dead space, which differs little from atmospheric air, is removed, then the alveolar air, enriched in CO 2 and poor in O 2 as a result of gas exchange. Under resting conditions the process is passive. It is carried out without the expenditure of muscle energy, due to the elastic traction of the lung, chest, gravitational forces and relaxation of the respiratory muscles

With forced breathing, the depth of exhalation increases with the help of abdominal and internal intercostal muscles. The abdominal muscles compress the abdominal cavity from the front and increase the rise of the diaphragm. The internal intercostal muscles move the ribs down and thereby reduce the cross-section of the thoracic cavity, and therefore its volume

Mechanism of inhalation and exhalation

Static indicators of external respiration (pulmonary volumes)

values characterizing potential breathing capabilities, depending on anthropometric data and characteristics of the functional volumes of the lung

PULMONARY VOLUME	CHARACTERISTIC	Volume in an adult, ml
Tidal volume (TO)	the volume of air that a person can inhale (exhale) during quiet breathing
Inspiratory reserve volume (IR) Vd )	the amount of air that can be additionally introduced during maximum inspiration
Expiratory reserve volume (ERV) Vyd )	the volume of air that a person can exhale additionally after a quiet exhalation
Residual volume (VR)	volume of air that remains in the lungs after maximum exhalation
Vital capacity of the lungs (VC)	The maximum volume of air that can be exhaled after a maximum inhalation. Depends on total lung capacity, strength of respiratory muscles, chest and lungs (YEL) = RO in + DO + RO in	For men – 3500-5000 For women – 3000-3500
Total lung capacity (TLC)	The greatest amount of air that completely fills the lungs. Characterizes the degree of anatomical development of the organ (VEL) = vital capacity + OO
Functional residual capacity (FRC)	The amount of air remaining in the lungs after a quiet exhalation (FOE) = RO Ext + OO

Static breathing parameters are determined by spirometry.

Spirometry– determination of static indicators of respiration (volumes - except residual; capacities - except FRC and TEL) by exhaling air through a device that records its quantity (volume). In modern dry vane spirometers, air rotates an air turbine connected to a needle

Rice. 12.14. Lung volumes and capacities

Pressure in the pleural cavity (clefts)

The lungs and the walls of the chest cavity are covered with a serous membrane - the pleura. Between the layers of the visceral and parietal pleura there is a narrow (5-10 microns) gap containing serous fluid, similar in composition to lymph. The lungs are constantly in a stretched state.

If a needle connected to a pressure gauge is inserted into the pleural fissure, it can be established that the pressure in it is below atmospheric. Negative pressure in the pleural fissure is caused by elastic traction of the lungs, i.e., the constant desire of the lungs to reduce their volume. At the end of quiet expiration, when almost all respiratory muscles are relaxed, the pressure in the pleural fissure (PPl) is approximately 3 mm Hg. Art. The pressure in the alveoli (Pa) at this time is equal to atmospheric pressure. Difference Pa-- -- РРl = 3 mm Hg. Art. is called transpulmonary pressure (P1). Thus, the pressure in the pleural fissure is lower than the pressure in the alveoli by the amount created by the elastic traction of the lungs.

When you inhale, due to contraction of the inspiratory muscles, the volume of the thoracic cavity increases. The pressure in the pleural fissure becomes more negative. By the end of a quiet inspiration it decreases to -6 mmHg. Art. Due to an increase in pulmonary pressure, the lungs expand and their volume increases due to atmospheric air. When the inspiratory muscles relax, the elastic forces of the stretched lungs and abdominal walls reduce transpulmonary pressure, the volume of the lungs decreases - exhalation occurs.

The mechanism of change in lung volume during breathing can be demonstrated using the Donders model.

With a deep breath, the pressure in the pleural fissure can decrease to -20 mm Hg. Art.

During active exhalation, this pressure can become positive, nevertheless remaining below the pressure in the alveoli by the amount of elastic traction of the lungs.

Under normal conditions, there are no gases in the pleural fissure. If you introduce a certain amount of air into the pleural fissure, it will gradually resolve. The absorption of gases from the pleural fissure occurs due to the fact that in the blood of small veins of the pulmonary circulation the tension of dissolved gases is lower than in the atmosphere. The accumulation of fluid in the pleural slit is prevented by oncotic pressure: the protein content in pleural fluid is significantly lower than in blood plasma. The relatively low hydrostatic pressure in the vessels of the pulmonary circulation is also important.

Elastic properties of the lungs. Elastic traction of the lungs is caused by three factors:

1) surface tension of the liquid film covering the inner surface of the 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. Eliminating surface tension forces (filling the lungs with saline solution) reduces the elastic traction of the lungs by 2/3. If the inner surface of the alveoli were covered with an aqueous solution, the surface

the tension tension should be 5-8 times greater. Under such conditions, there would be a complete collapse of some alveoli (atelectasis) with overextension of others. This does not happen because the inner surface of the alveoli is lined with a substance that has low surface tension, the so-called surfactant. The lining has a thickness of 20-100 nm. It consists of lipids and proteins. Surfactant is produced by special cells of the alveoli - type II pneumocytes. The surfactant film has a remarkable property: a decrease in the size of the alveoli is accompanied by a decrease in surface tension; this is important for stabilizing the condition of the alveoli. The formation of surfactant is enhanced by parasympathetic influences; after transection of the vagus nerves it slows down.

The elastic properties of the lungs are usually expressed quantitatively by the so-called extensibility: where D V1 is the change in lung volume; DR1 - change in transpulmonary pressure.

In adults, it is approximately 200 ml/cm of water. Art. In infants, lung compliance is much lower - 5-10 ml/cm of water. Art. This indicator changes in lung diseases and is used for diagnostic purposes.

A. I. KIENYA

PHYSIOLOGY

BREATHING

Ministry of Health of the Republic of Belarus

Gomel State Medical Institute

Department of Human Physiology

A. I. KIENYA

Doctor of Biological Sciences, Professor

PHYSIOLOGY

BREATHING

Tutorial

Reviewers:

Ruzanov D.Yu., Candidate of Medical Sciences, Head of the Department of Phthisiopulmonology, Gomel State Medical Institute.

Kienya A.I.

K38 Physiology of respiration: Textbook. - Gomel.-2002.- p.

The manual is based on the material of lectures on the section “Physiology of Respiration” of normal physiology, given by the author to students of the Faculty of Medicine and the Faculty of Training of Specialists for Foreign Countries.

For students, teachers, graduate students of medical and biological universities and related specialties.

PREFACE

This manual is a summary of lectures on the section “Physiology of Respiration” of normal physiology, given by the author to students of the Gomel State Medical Institute. The material of the manual is presented in accordance with the Program on Normal Physiology for Students of the Medical and Prophylactic Faculty of Higher Medical Educational Institutions No. 08-14/5941, approved by the Ministry of Health of the Republic of Belarus on September 3, 1997.

The manual presents modern information about respiration as a system that serves metabolic processes in the body. The main stages of breathing, mechanisms of respiratory movements (inhalation and exhalation), the role of negative pressure in the pleural cavity, ventilation of the lungs and pulmonary volumes and capacities, anatomical and functional dead space, their physiological significance, gas exchange processes in the lungs, gas transport (O 2 and CO 2) blood, factors influencing the formation of hemoglobin compounds with O 2 and CO 2 and their dissociation, gas exchange between blood and tissues. Neurohumoral mechanisms of respiration regulation are considered, the structural organization of the respiratory center, the role of gas composition and various receptors in the regulation of respiration are analyzed. The features of breathing under different conditions are described. The mechanism and theories of the occurrence of the first breath of a newborn are outlined. Age-related breathing features are considered.

The age-related characteristics of the respiratory system are considered separately.

At the end of the manual, the main blood constants of a healthy person are presented.

At the same time, the author is aware that in this manual, due to its small volume, it was not possible to cover in detail all aspects of respiratory physiology, therefore some of them are presented in summary form, more extensive information about which can be found in the literature sources given at the end of the manual.

The author will be very grateful to everyone who considers it possible to express their critical comments to the proposed manual, which will be perceived as an expression of desire to assist in its improvement during subsequent republication.

EXTERNAL RESPIRATION

The generation of energy necessary to ensure the vital functions of the human body occurs on the basis of oxidative processes. For their implementation, a constant influx of O 2 from the external environment and continuous removal of CO 2 from it, formed in tissues as a result of metabolism, are necessary.

The set of processes that ensure the entry of O 2 into the body, its delivery and consumption to tissues and the release of the final product of respiration CO 2 into the external environment is called respiration. This is a physiological system.

A person can live without:

food for less than a month,

· water - 10 days,

· oxygen - 4-7 minutes (no reserve). In this case, first of all, the death of nerve cells occurs.

The complex process of gas exchange with the environment consists of a number of sequential processes.

External respiration (pulmonary):

1. Exchange of gases between pulmonary air and atmospheric air (pulmonary ventilation).

2. Exchange of gases between the pulmonary air and the blood of the capillaries of the pulmonary circulation.

Internal:

3. Transport of O 2 and CO 2 by blood.

4. Exchange of gases between blood and cells (tissue respiration), that is, consumption of O 2 and release of CO 2 during metabolism.

The function of external respiration and renewal of the blood gas composition in humans is performed by the airways and lungs.

Respiratory tract: nasal and oral cavity, larynx, trachea, bronchi, bronchioles, alveolar ducts. The trachea in humans is approximately 15 cm and is divided into two bronchi: right and left. They branch into smaller bronchi, and the latter into bronchioles (up to 0.3 - 0.5 mm in diameter). The total number of bronchioles is approximately 250 million. The bronchiole branches into alveolar ducts, and they end in blind sacs - alveoli. The alveoli are lined internally with respiratory epithelium. The surface area of all alveoli in humans reaches 50-90 m2.

Each alveolus is intertwined with a dense network of blood capillaries.

There are two types of cells in the mucous membrane of the respiratory tract:

a) ciliated epithelial cells;

b) secretory cells.

On the outside, the lungs are covered with a thin, serous membrane - the pleura.

In the right lung there are three lobes: upper (apical), middle (cardiac), lower (diaphragmatic). The left lung has two lobes (upper and lower).

To carry out gas exchange processes in the structure of the lungs, there are a number of adaptive features:

1. The presence of an air and blood channel, separated from each other by a thin film consisting of a double layer - the alveoli itself and the capillary (the section of air and blood - thickness 0.004 mm). Diffusion of gases occurs through this air-hematic barrier.

2. The extensive respiratory area of the lungs, 50-90 m2, is approximately equal to the increase in body surface (1.7 m20) by several tens of times.

3. The presence of a special - pulmonary circulation, specifically performing an oxidative function (functional circle). A blood particle passes through a small circle in 5 seconds, and the time of its contact with the alveolar wall is only 0.25 - 0.7 seconds.

4. The presence of elastic tissue in the lungs, which promotes the expansion and collapse of the lungs during inhalation and exhalation. The lungs are in a state of elastic tension.

5. The presence of supporting cartilaginous tissue in the respiratory tract in the form of cartilaginous bronchi. This prevents the airways from collapsing and allows air to pass through quickly and easily.

Breathing movements

Ventilation of the alveoli, necessary for gas exchange, is carried out by alternating inhalation (inspiration) and exhalation (expiration). When you inhale, air saturated with O2 enters the alveoli. When exhaling, air is removed from them, poor in O 2, but richer in CO 2. The inhalation phase and the following exhalation phase are respiratory cycle.

The movement of air is caused by an alternating increase and decrease in the volume of the chest.

The mechanism of inhalation (inspiration).

Enlargement of the chest cavity in the vertical, sagittal, frontal planes. This is ensured by: raising the ribs and flattening (lowering) the diaphragm.

Movement of the ribs. The ribs form movable connections with the bodies and transverse processes of the vertebrae. The axis of rotation of the ribs passes through these two points. The axis of rotation of the upper ribs is almost horizontal, so when the ribs are raised, the size of the chest increases in the anteroposterior direction. The axis of rotation of the lower ribs is located more sagittally. Therefore, when the ribs are raised, the volume of the chest increases laterally.

Since the movement of the lower ribs has a greater impact on the volume of the chest, the lower lobes of the lung are better ventilated than the apexes.

Raising the ribs occurs due to contraction of the inspiratory muscles. These include: external intercostal, internal intercartilaginous muscles. Their muscle fibers are oriented in such a way that their point of attachment to the lower rib is located further from the center of rotation than the point of attachment to the overlying rib. Their direction: behind, above, forward and down.

As a result, the chest increases in volume.

In a healthy young man, the difference between the chest circumference in the inhalation and exhalation positions is 7-10 cm, in women it is 5-8 cm. During forced breathing, the auxiliary inspiratory muscles are activated:

· - pectoralis major and minor;

· - stairs;

· - sternocleidomastoid;

· - (partially) toothed;

· - trapezoidal, etc.

Connection of auxiliary muscles occurs when pulmonary ventilation is over 50 l/min.

Aperture movement. The diaphragm consists of a tendon center and muscle fibers extending from this center in all directions and are attached to the thoracic opening. It has the shape of a dome, protruding into the chest cavity. When you exhale, it is adjacent to the inner wall of the chest for an area approximately equal to 3 ribs. When you inhale, the diaphragm flattens as a result of contraction of its muscle fibers. At the same time, it moves away from the inner surface of the chest and the costophrenic sinuses open.

Innervation of the diaphragm is by phrenic nerves from C 3 -C 5. Unilateral transection of the phrenic nerve on the same side, the diaphragm is strongly pulled into the chest cavity under the influence of the pressure of the viscera and the thrust of the lungs. The movement of the lower parts of the lungs is limited. Thus, inspiration is active act.

Mechanism of exhalation (expiration) is ensured through:

· Heaviness of the chest.

· Elasticity of costal cartilages.

· Elasticity of the lungs.

· Pressure of the abdominal organs on the diaphragm.

At rest, exhalation occurs passively.

In forced breathing, expiratory muscles are used: internal intercostal muscles (their direction is from above, back, front, down) and auxiliary expiratory muscles: muscles that flex the spine, abdominal muscles (oblique, rectus, transverse). When the latter contract, the abdominal organs put pressure on the relaxed diaphragm and it protrudes into the chest cavity.

Types of breathing. Depending primarily on which component (raising the ribs or the diaphragm) the chest volume increases, there are 3 types of breathing:

· - thoracic (costal);

· - abdominal;

· - mixed.

To a greater extent, the type of breathing depends on age (the mobility of the chest increases), clothing (tight bodices, swaddling), profession (for people engaged in physical labor, the abdominal type of breathing increases). Abdominal breathing becomes difficult in the last months of pregnancy, and then chest breathing is additionally activated.

The most effective type of breathing is abdominal:

· - deeper ventilation of the lungs;

· - facilitates the return of venous blood to the heart.

The abdominal type of breathing predominates among manual workers, rock climbers, singers, etc. In a child, after birth, the abdominal type of breathing is first established, and later, by the age of 7, chest breathing.

Pressure in the pleural cavity and its change during breathing.

The lungs are covered with visceral pleura, and the film of the chest cavity is covered with parietal pleura. Between them there is serous fluid. They fit tightly to each other (gap 5-10 microns) and slide relative to each other. This sliding is necessary so that the lungs can follow the complex changes of the chest without deforming. With inflammation (pleurisy, adhesions), ventilation of the corresponding areas of the lungs decreases.

If you insert a needle into the pleural cavity and connect it to a water pressure gauge, you will find that the pressure in it is:

· when inhaling - by 6-8 cm H 2 O

· when exhaling - 3-5 cm H 2 O below atmospheric.

This difference between intrapleural and atmospheric pressure is usually called pleural pressure.

Negative pressure in the pleural cavity is caused by elastic traction of the lungs, i.e. tendency of the lungs to collapse.

When inhaling, an increase in the thoracic cavity leads to an increase in negative pressure in the pleural cavity, i.e. transpulmonary pressure increases, leading to expansion of the lungs (demonstration using the Donders apparatus).

When the inspiratory muscles relax, transpulmonary pressure decreases and the lungs collapse due to elasticity.

If you introduce a small amount of air into the pleural cavity, it will dissolve, because in the blood of small veins of the pulmonary circulation the tension of dissolved gases is less than in the atmosphere.

The accumulation of fluid in the pleural cavity is prevented by the lower oncotic pressure of pleural fluid (less proteins) than in plasma. A decrease in hydrostatic pressure in the pulmonary circulation is also important.

The change in pressure in the pleural cavity can be measured directly (but lung tissue may be damaged). Therefore, it is better to measure it by inserting a 10 cm long balloon into the esophagus (into the thoracic part). The walls of the esophagus are very pliable.

Elastic traction of the lungs is caused by 3 factors:

1. Surface tension of the liquid film covering the inner surface of the alveoli.

2. The elasticity of the tissue of the walls of the alveoli (contain elastic fibers).

3. Tone of the bronchial muscles.

At any interface between air and liquid, intermolecular cohesion forces act, tending to reduce the size of this surface (surface tension forces). Under the influence of these forces, the alveoli tend to contract. Surface tension forces create 2/3 of the elastic traction of the lungs. The surface tension of the alveoli is 10 times less than theoretically calculated for the corresponding water surface.

If the inner surface of the alveoli were covered with an aqueous solution, then the surface tension should have been 5-8 times greater. Under these conditions there would be collapse of the alveoli (atelectasis). But this doesn't happen.

This means that in the alveolar fluid on the inner surface of the alveoli there are substances that reduce surface tension, i.e. surfactants. Their molecules are strongly attracted to each other, but have a weak interaction with liquid, as a result of which they collect on the surface and thereby reduce surface tension.

Such substances are called surface active substances (surfactants), the role of which in this case is played by the so-called surfactants. They are lipids and proteins. They are formed by special cells of the alveoli - type II pneumocytes. The lining has a thickness of 20-100 nm. But lecithin derivatives have the greatest surface activity of the components of this mixture.

When the size of the alveoli decreases. surfactant molecules come closer together, their density per unit surface area is greater and surface tension decreases - the alveolus does not collapse.

As the alveoli enlarge (expand) their surface tension increases, as the density of surfactant per unit surface area decreases. This enhances the elastic traction of the lungs.

During the process of breathing, the strengthening of the respiratory muscles is spent on overcoming not only the elastic resistance of the lungs and chest tissues, but also on overcoming the inelastic resistance to gas flow in the airways, which depends on their lumen.

Impaired formation of surfactants leads to the collapse of a large number of alveoli - atelectasis - lack of ventilation of large areas of the lungs.

In newborns, surfactants are necessary for the expansion of the lungs during the first respiratory movements.

There is a disease of newborns in which the surface of the alveoli is covered with fibrin precipitate (gealin membranes), which reduces the activity of surfactants - reduced. This leads to incomplete expansion of the lungs and severe disruption of gas exchange.

When air (pneumothorax) enters the pleural cavity (through a damaged chest wall or lungs), due to the elasticity of the lungs, they collapse and are pressed towards the root, occupying 1/3 of their volume.

With unilateral pneumothorax, the lung on the undamaged side can provide sufficient saturation of the blood with O 2 and removal of CO 2 (at rest). In case of bilateral - if artificial ventilation of the lungs is not performed, or sealing of the pleural cavity - to death.

Unilateral pneumothorax is sometimes used for therapeutic purposes: introducing air into the pleural cavity to treat tuberculosis (cavities).

The lungs are constantly in the chest cavity in an extended state. It is formed as a result of the existence of the pleural cavity and the presence of negative pressure in it.

The pleural cavity is formed as follows: the lungs and walls of the chest cavity are covered with a serous membrane - pleura. Between the layers of the visceral and parietal pleura there is a narrow (5-10 µm) gap, a cavity is formed containing serous fluid, similar in composition to lymph. This fluid has a low concentration of proteins, which causes low oncotic pressure compared to blood plasma. This circumstance prevents the accumulation of fluid in the pleural cavity.

The pressure in the pleural cavity is below atmospheric pressure, which is defined as negative pressure. It is caused by elastic traction of the lungs, i.e. the constant desire of the lungs to reduce their volume. The pressure in the pleural cavity is lower than the alveolar pressure by the amount created by the elastic traction of the lungs: P pl = P alv – P e.t.l. . Elastic traction of the lungs is caused by three factors:

1) Surface tension a film of liquid covering the inner surface of the alveoli - surfactant. This substance has low surface tension. Surfactant is produced by type II pneumocytes and consists of proteins and lipids. It has the property of reducing the surface tension of the alveolar wall while reducing the size of the alveoli. This stabilizes the condition of the alveolar wall when their volume changes. If the surface of the alveoli were covered with a layer of aqueous solution, this would increase the surface tension by 5-8 times. Under such conditions, complete collapse of some alveoli (atelectasis) was observed while others were overstretched. The presence of surfactant prevents the development of this lung condition in a healthy body.

2) The elasticity of the tissue of the walls of the alveoli, which have elastic fibers in the wall.

3) Tone of the bronchial muscles.

Elastic traction of the lungs determines the elastic properties of the lungs. The elastic properties of the lungs are usually expressed quantitatively extensibility lung tissue WITH :

Where ∆ V – increase in lung volume when stretched (in ml),

∆Р– change in transpulmonary pressure when the lungs are stretched (in cm water column).

In adults, C is 200 ml/cm of water. Art., in newborns and infants - 5-10 ml/cm of water. Art. This indicator (its decrease) changes in lung diseases and is used for diagnostic purposes.

Pleural pressure changes with the dynamics of the respiratory cycle. At the end of a quiet exhalation, the pressure in the alveoli is equal to atmospheric pressure, and in the pleural cavity - 3 mm Hg. Art. The difference R alv – R pl = R l is called transpulmonary pressure and equal to +3 mm Hg. Art. It is this pressure that maintains the distended state of the lungs at the end of exhalation.

When inhaling, due to contraction of the inspiratory muscles, the volume of the chest increases. Pleural pressure (P pl) becomes more negative - by the end of a quiet inspiration it is equal to –6 mm Hg. Art., transpulmonary pressure (P l) increases to +6 mm Hg, as a result of which the lungs expand, their volume increases due to atmospheric air.

With a deep breath, Ppl can drop to −20 mmHg. Art. During deep exhalation, this pressure can become positive, nevertheless remaining below the pressure in the alveoli by the amount of pressure created by the elastic traction of the lungs.

If a small amount of air enters the pleural fissure, the lung partially collapses, but ventilation continues. This condition is called closed pneumothorax. After some time, air is absorbed from the pleural cavity and the lung expands (Aspiration of gases from the pleural cavity occurs due to the fact that in the blood of small veins of the pulmonary circulation the tension of dissolved gases is lower than in the atmosphere).

RESPIRATION is a set of processes that ensure the body consumes oxygen (O2) and releases carbon dioxide (CO2)

STEPS OF BREATHING:

1. External respiration or ventilation of the lungs - exchange of gases between atmospheric and alveolar air

2. Exchange of gases between the alveolar air and the blood of the capillaries of the pulmonary circulation

3. Transport of gases by blood (O 2 and CO 2)

4. Exchange of gases in tissues between the blood of the capillaries of the systemic circulation and tissue cells

5. Tissue, or internal, respiration - the process of tissue absorption of O 2 and release of CO 2 (redox reactions in mitochondria with the formation of ATP)

RESPIRATORY SYSTEM

A set of organs that supply the body with oxygen, remove carbon dioxide and release energy necessary for all forms of life.

FUNCTIONS OF THE RESPIRATORY SYSTEM:

Ø Providing the body with oxygen and using it in redox processes

Ø Formation and release of excess carbon dioxide from the body

Ø Oxidation (decomposition) of organic compounds with the release of energy

Ø Release of volatile metabolic products (water vapor (500 ml per day), alcohol, ammonia, etc.)

Processes underlying the execution of functions:

a) ventilation (airing)

b) gas exchange

STRUCTURE OF THE RESPIRATORY SYSTEM

Rice. 12.1. The structure of the respiratory system

1 – Nasal passage

2 – Nasal concha

3 – Frontal sinus

4 – Sphenoid sinus

5 – Throat

6 – Larynx

7 – Trachea

8 – Left bronchus

9 – Right bronchus

10 – Left bronchial tree

11 – Right bronchial tree

12 – Left lung

13 – Right lung

14 – Aperture

16 – Esophagus

17 – Ribs

18 – Sternum

19 – Clavicle

the organ of smell, as well as the external opening of the respiratory tract: serves to warm and purify the inhaled air

NASAL CAVITY

The initial section of the respiratory tract and at the same time the organ of smell. Stretches from the nostrils to the pharynx, divided by a septum into two halves, which are in front through nostrils communicate with the atmosphere, and behind with the help joan- with nasopharynx

Rice. 12.2. Structure of the nasal cavity

Larynx

a piece of breathing tube that connects the pharynx to the trachea. Located at the level of IV-VI cervical vertebrae. It is an entrance hole that protects the lungs. The vocal cords are located in the larynx. Behind the larynx is the pharynx, with which it communicates through its superior opening. Below the larynx passes into the trachea

Rice. 12.3. Structure of the larynx

Glottis- the space between the right and left vocal folds. When the position of the cartilage changes, under the action of the muscles of the larynx, the width of the glottis and the tension of the vocal cords can change. Exhaled air vibrates the vocal cords ® sounds are produced

Trachea

a tube that communicates with the larynx at the top and ends with a division at the bottom ( bifurcation ) into two main bronchi

Rice. 12.4. Main airways

Inhaled air passes through the larynx into the trachea. From here it is divided into two streams, each of which goes to its own lung through a branched system of bronchi

BRONCHI

tubular formations representing the branches of the trachea. They depart from the trachea almost at a right angle and go to the gates of the lungs

Right bronchus wider but shorter left and is like a continuation of the trachea

The bronchi are similar in structure to the trachea; they are very flexible due to cartilaginous rings in the walls and are lined with respiratory epithelium. The connective tissue base is rich in elastic fibers that can change the diameter of the bronchus

Main bronchi(first order) are divided into equity (second order): three in the right lung and two in the left - each goes to its own lobe. Then they are divided into smaller ones, going into their own segments - segmental (third order), which continue to divide, forming "bronchial tree" lung

BRONCHIAL TREE– the bronchial system, through which air from the trachea enters the lungs; includes main, lobar, segmental, subsegmental (9-10 generations) bronchi, as well as bronchioles (lobular, terminal and respiratory)

Within the bronchopulmonary segments, the bronchi divide successively up to 23 times until they end in a dead end of alveolar sacs

Bronchioles(diameter of the respiratory tract less than 1 mm) divide until they form end (terminal) bronchioles, which are divided into the thinnest short airways - respiratory bronchioles, turning into alveolar ducts, on the walls of which there are bubbles - alveoli (air sacs). The main part of the alveoli is concentrated in clusters at the ends of the alveolar ducts, formed during the division of respiratory bronchioles

Rice. 12.5. Lower respiratory tract

Rice. 12.6. Airway, gas exchange area and their volumes after quiet exhalation

Functions of the airways:

1. Gas exchange - delivery of atmospheric air to gas exchange area and conduction of the gas mixture from the lungs into the atmosphere

2. Non-gas exchange:

§ Air purification from dust and microorganisms. Protective breathing reflexes (coughing, sneezing).

§ Humidification of inhaled air

§ Warming of inhaled air (at the level of the 10th generation up to 37 0 C

§ Reception (perception) of olfactory, temperature, mechanical stimuli

§ Participation in the processes of thermoregulation of the body (heat production, heat evaporation, convection)

§ They are a peripheral sound generation apparatus

Acinus

a structural unit of the lung (up to 300 thousand), in which gas exchange occurs between the blood located in the capillaries of the lung and the air filling the pulmonary alveoli. It is a complex from the beginning of the respiratory bronchiole, resembling a bunch of grapes in appearance

The acini includes 15-20 alveoli, into the pulmonary lobule - 12-18 acini. Lobes of the lung are made up of lobules

Rice. 12.7. Pulmonary acinus

Alveoli(in the lungs of an adult there are 300 million, their total surface area is 140 m2) - open vesicles with very thin walls, the inner surface of which is lined with single-layer squamous epithelium lying on the main membrane, to which blood capillaries entwining the alveoli are adjacent, forming together with epithelial cells barrier between blood and air (air-blood barrier) 0.5 microns thick, which does not interfere with the exchange of gases and the release of water vapor

Found in the alveoli:

§ macrophages(protective cells) that absorb foreign particles entering the respiratory tract

§ pneumocytes- cells that secrete surfactant

Rice. 12.8. Ultrastructure of the alveoli

SURFACTANT– a pulmonary surfactant containing phospholipids (in particular lecithin), triglycerides, cholesterol, proteins and carbohydrates and forming a 50 nm thick layer inside the alveoli, alveolar ducts, sacs, bronchioles

Surfactant value:

§ Reduces the surface tension of the fluid covering the alveoli (almost 10 times) ® facilitates inhalation and prevents atelectasis (sticking together) of the alveoli during exhalation.

§ Facilitates the diffusion of oxygen from the alveoli into the blood due to the good solubility of oxygen in it.

§ Performs a protective role: 1) has bacteriostatic activity; 2) protects the walls of the alveoli from the damaging effects of oxidizing agents and peroxides; 3) provides reverse transport of dust and microbes through the airway; 4) reduces the permeability of the pulmonary membrane, which prevents the development of pulmonary edema due to a decrease in the exudation of fluid from the blood into the alveoli

LUNGS

The right and left lung are two separate objects located in the chest cavity on either side of the heart; covered with a serous membrane - pleura, which forms around them two closed pleural sac. They have an irregular cone shape with the base facing the diaphragm and the apex protruding 2-3 cm above the collarbone in the neck area

Rice. 12.10. Segmental structure of the lungs.

1 – apical segment; 2 – posterior segment; 3 – anterior segment; 4 – lateral segment (right lung) and superior lingular segment (left lung); 5 – medial segment (right lung) and lower lingular segment (left lung); 6 – apical segment of the lower lobe; 7 – basal medial segment; 8 – basal anterior segment; 9 – basal lateral segment; 10 – basal posterior segment

ELASTICITY OF THE LUNGS

the ability to respond to load by increasing voltage, which includes:

§ elasticity– the ability to restore its shape and volume after the cessation of external forces causing deformation

§ rigidity– the ability to resist further deformation when elasticity is exceeded

Reasons for the elastic properties of the lungs:

§ elastic fiber tension lung parenchyma

§ surface tension fluid lining the alveoli - created by surfactant

§ blood filling of the lungs (the higher the blood filling, the less elasticity

Extensibility– the inverse property of elasticity is associated with the presence of elastic and collagen fibers that form a spiral network around the alveoli

Plastic– property opposite to rigidity

FUNCTIONS OF THE LUNGS

Gas exchange– enrichment of blood with oxygen used by body tissues and removal of carbon dioxide from it: achieved through pulmonary circulation. Blood from the body's organs returns to the right side of the heart and travels through the pulmonary arteries to the lungs

Non-gas exchange:

Ø Z protective – formation of antibodies, phagocytosis by alveolar phagocytes, production of lysozyme, interferon, lactoferrin, immunoglobulins; microbes, aggregates of fat cells, and thromboemboli are retained and destroyed in the capillaries

Ø Participation in thermoregulation processes

Ø Participation in allocation processes – removal of CO 2, water (about 0.5 l/day) and some volatile substances: ethanol, ether, nitrous oxide, acetone, ethyl mercaptan

Ø Inactivation of biologically active substances – more than 80% of bradykinin introduced into the pulmonary bloodstream is destroyed during a single passage of blood through the lung, angiotensin I is converted to angiotensin II under the influence of angiotensinase; 90-95% of prostaglandins of groups E and P are inactivated

Ø Participation in the production of biologically active substances –heparin, thromboxane B 2, prostaglandins, thromboplastin, blood coagulation factors VII and VIII, histamine, serotonin

Ø They serve as an air reservoir for voice production

EXTERNAL BREATHING

The process of ventilation of the lungs, providing gas exchange between the body and the environment. It is carried out due to the presence of the respiratory center, its afferent and efferent systems, and respiratory muscles. It is assessed by the ratio of alveolar ventilation to minute volume. To characterize external respiration, static and dynamic indicators of external respiration are used

Respiratory cycle– rhythmically repeating change in the state of the respiratory center and executive respiratory organs

Rice. 12.11. Respiratory muscles

Diaphragm- a flat muscle that separates the chest cavity from the abdominal cavity. It forms two domes, left and right, with their bulges pointing upward, between which there is a small depression for the heart. It has several holes through which very important structures of the body pass from the thoracic region to the abdominal region. By contracting, it increases the volume of the chest cavity and provides air flow into the lungs

Rice. 12.12. Position of the diaphragm during inhalation and exhalation

pressure in the pleural cavity

Rice. 12.13. Pressure changes during inhalation and exhalation