The respiratory system performs the function of gas exchange, but also takes part in such important processes as thermoregulation, air humidification, water-salt exchange and many others. The respiratory organs are represented by the nasal cavity, nasopharynx, oropharynx, larynx, trachea, bronchi, and lungs.

nasal cavity

It is divided by a cartilaginous septum into two halves - right and left. On the septum there are three nasal conchas that form the nasal passages: upper, middle and lower. The walls of the nasal cavity are lined with a mucous membrane with ciliated epithelium. The cilia of the epithelium, moving sharply and quickly in the direction of the nostrils and smoothly and slowly in the direction of the lungs, trap and bring out the dust and microorganisms that have settled on the mucus of the shell.

The mucous membrane of the nasal cavity is abundantly supplied with blood vessels. The blood flowing through them warms or cools the inhaled air. The glands of the mucous membrane secrete mucus, which moisturizes the walls of the nasal cavity and reduces the vital activity of bacteria from the air. On the surface of the mucous membrane there are always leukocytes that destroy a large number of bacteria. In the mucous membrane upper division nasal cavities are endings nerve cells that form the organ of smell.

The nasal cavity communicates with the cavities located in the bones of the skull: the maxillary, frontal and sphenoid sinuses.

Thus, the air entering the lungs through the nasal cavity is purified, warmed and disinfected. This does not happen to him if he enters the body through oral cavity. From the nasal cavity through the choanae, air enters the nasopharynx, from it into the oropharynx, and then into the larynx.

It is located on the front side of the neck and from the outside, its part is visible as an elevation called the Adam's apple. The larynx is not only an air-bearing organ, but also an organ for the formation of voice, sound speech. It is compared with a musical apparatus that combines elements of wind and string instruments. From above, the entrance to the larynx is covered by the epiglottis, which prevents food from entering it.

The walls of the larynx consist of cartilage and are covered from the inside by a mucous membrane with ciliated epithelium, which is absent on the vocal cords and on part of the epiglottis. The cartilages of the larynx are represented in the lower section by the cricoid cartilage, in front and from the sides - by the thyroid cartilage, from above - by the epiglottis, behind by three pairs of small ones. They are interconnected semi-movably. Muscles and vocal cords are attached to them. The latter consist of flexible, elastic fibers that run parallel to each other.

Between the vocal cords of the right and left halves is the glottis, the lumen of which varies depending on the degree of tension of the ligaments. It is caused by contractions of special muscles, which are also called voice. Their rhythmic contractions are accompanied by contractions of the vocal cords. From this, the air stream coming out of the lungs acquires an oscillatory character. There are sounds, voices. The shades of the voice depend on the resonators, the role of which is played by the cavities of the respiratory tract, as well as the pharynx, and the oral cavity.

Anatomy of the trachea

The lower part of the larynx passes into the trachea. The trachea is located in front of the esophagus and is a continuation of the larynx. Trachea length 9-11cm, diameter 15-18mm. At the fifth level thoracic vertebra it is divided into two bronchi: right and left.

The wall of the trachea consists of 16-20 incomplete cartilaginous rings that prevent the narrowing of the lumen, interconnected by ligaments. They extend over 2/3 circles. The posterior wall of the trachea is membranous, contains smooth (non-striated) muscle fibers and adjacent to the esophagus.

Bronchi

Air enters from the trachea into two bronchi. Their walls also consist of cartilaginous semirings (6-12 pieces). They prevent the collapse of the walls of the bronchi. Together with blood vessels and nerves, the bronchi enter the lungs, where, branching, they form bronchial tree lung.

From the inside, the trachea and bronchi are lined with a mucous membrane. The thinnest bronchi are called bronchioles. They end in alveolar passages, on the walls of which there are pulmonary vesicles, or alveoli. The diameter of the alveoli is 0.2-0.3 mm.

The wall of the alveolus consists of one layer squamous epithelium and a thin layer of elastic fibers. The alveoli are covered with a dense network blood capillaries where gas exchange takes place. They form a respiratory part of a lung, and the bronchi are the air-bearing department.

In the lungs of an adult, there are about 300-400 million alveoli, their surface is 100-150m 2, i.e. the total respiratory surface of the lungs is 50-75 times larger than the entire surface of the human body.

The structure of the lungs

The lungs are paired organ. The left and right lungs occupy almost the entire chest cavity. The right lung is larger in volume than the left, and consists of three lobes, the left - of two lobes. On the inner surface of the lungs are the gates of the lungs, through which the bronchi, nerves, pulmonary arteries, pulmonary veins and lymphatic vessels.

Outside, the lungs are covered with a connective tissue membrane - the pleura, which consists of two sheets: the inner sheet is fused with the air-bearing tissue of the lung, and the outer one - with the walls of the chest cavity. Between the sheets there is a space - the pleural cavity. The contact surfaces of the inner and outer layers of the pleura are smooth, constantly moistened. Therefore, normally, their friction during respiratory movements is not felt. In the pleural cavity, the pressure is 6-9 mm Hg. Art. below atmospheric. The smooth, slippery surface of the pleura and the reduced pressure in its cavities favor the movements of the lungs during the acts of inhalation and exhalation.

The main function of the lungs is to exchange gases between external environment and organism.

The respiratory system performs the function of gas exchange, delivering oxygen to the body and removing carbon dioxide from it. The airways are the nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles and lungs.

In the upper respiratory tract, the air is warmed, cleared of various particles and moisturized. Gas exchange takes place in the alveoli of the lungs.

nasal cavity It is lined with a mucous membrane, in which two parts differ in structure and function: respiratory and olfactory.

The respiratory part is covered with ciliated epithelium that secretes mucus. Mucus moisturizes the inhaled air, envelops solid particles. The mucous membrane warms the air, as it is abundantly supplied with blood vessels. Three turbinates increase the overall surface of the nasal cavity. Under the shells are the lower, middle and upper nasal passages.

Air from the nasal passages enters through the choanae into the nasal, and then into the oral part of the pharynx and larynx.

Larynx performs two functions - respiratory and voice formation. The complexity of its structure is associated with the formation of voice. The larynx is located at the level of the IV-VI cervical vertebrae and is connected by ligaments to the hyoid bone. The larynx is formed by cartilage. Outside (in men this is especially noticeable) the "Adam's apple" protrudes, " adam's apple"- thyroid cartilage. At the base of the larynx is the cricoid cartilage, which is connected by joints to the thyroid and two arytenoid cartilages. The cartilaginous vocal process departs from the arytenoid cartilages. The entrance to the larynx is covered by an elastic cartilaginous epiglottis attached to the thyroid cartilage and hyoid bone by ligaments.

Between the arytenoids and the inner surface of the thyroid cartilage are vocal cords, consisting of elastic fibers of connective tissue. Sound is produced by the vibration of the vocal cords. The larynx takes part only in the formation of sound. Articulate speech involves lips, tongue, soft sky, paranasal sinuses. The larynx changes with age. Its growth and function are associated with the development of the gonads. The size of the larynx in boys during puberty increases. The voice changes (mutates).

Air enters the trachea from the larynx.

Trachea- a tube, 10-11 cm long, consisting of 16-20 cartilaginous rings not closed behind. The rings are connected by ligaments. The posterior wall of the trachea is made up of dense fibrous connective tissue. A food bolus passing through the esophagus adjacent to back wall trachea, does not experience resistance from her side.

The trachea divides into two elastic main bronchi. The right bronchus is shorter and wider than the left. The main bronchi branch into smaller bronchi - bronchioles. The bronchi and bronchioles are lined ciliated epithelium. The bronchioles contain secretory cells that produce enzymes that break down surfactant, a secret that helps maintain the surface tension of the alveoli, preventing them from collapsing when exhaled. It also has a bactericidal effect.

Lungs, paired organs located in the chest cavity. The right lung has three lobes, the left has two. The lobes of the lung, to a certain extent, are anatomically isolated areas with a bronchus that ventilates them and their own vessels and nerves.

The functional unit of the lung is the acinus, a branching system of one terminal bronchiole. This bronchiole is divided into 14-16 respiratory bronchioles, forming up to 1500 alveolar passages, bearing up to 20,000 alveoli. The pulmonary lobule consists of 16-18 acini. Segments are made up of lobules, lobes are made up of segments, and a lung is made up of lobes.

Outside, the lung is covered with an internal pleura. Its outer layer (parietal pleura) lines the chest cavity and forms a sac in which the lung is located. Between the outer and inner sheets is the pleural cavity, filled with a small amount of fluid that facilitates the movement of the lungs during breathing. The pressure in the pleural cavity is less than atmospheric and is about 751 mm Hg. Art.

When inhaling, the chest cavity expands, the diaphragm descends, and the lungs expand. When exhaling, the volume of the chest cavity decreases, the diaphragm relaxes and rises. The respiratory movements involve the external intercostal muscles, the muscles of the diaphragm, and the internal intercostal muscles. With increased breathing, all the muscles of the chest are involved, lifting the ribs and sternum, the muscles of the abdominal wall.

Tidal volume is the amount of air inhaled and exhaled by a person at rest. It is equal to 500 cm 3.

Extra volume - the amount of air that a person can inhale after a normal breath. This is another 1500 cm 3.

The reserve volume is the amount of air that a person can exhale after a normal exhalation. It is equal to 1500 cm 3. All three quantities make up the vital capacity of the lungs.

Residual air is the amount of air that remains in the lungs after the deepest exhalation. It is equal to 1000 cm 3.

Breathing movements controlled by the respiratory center of the medulla oblongata. The center has departments of inhalation and exhalation. From the center of inhalation, impulses are sent to the respiratory muscles. There is a breath. Impulses from the respiratory muscles are sent to respiratory center on vagus nerve and inhibit the inspiratory center. There is an exhalation. The activity of the respiratory center is affected by the level blood pressure, temperature, pain and other stimuli. Humoral regulation occurs when the concentration of carbon dioxide in the blood changes. Its increase excites the respiratory center and causes quickening and deepening of breathing. The ability to arbitrarily hold your breath for a while is explained by the controlling influence on the breathing process of the cerebral cortex.

Gas exchange in the lungs and tissues occurs by diffusion of gases from one medium to another. The partial pressure of oxygen in atmospheric air is higher than in alveolar air, and it diffuses into the alveoli. From the alveoli, for the same reasons, oxygen penetrates into venous blood, saturating it, and from the blood - into the tissue.

The partial pressure of carbon dioxide in the tissues is higher than in the blood, and in the alveolar air is higher than in atmospheric (). Therefore, it diffuses from the tissues into the blood, then into the alveoli and into the atmosphere.

The air passage system through our body is complex structure. Nature has created a mechanism for delivering oxygen to the lungs, where it enters the bloodstream so that it is possible to exchange gases between environment and every cell in our body.

Under the scheme respiratory system a person means the respiratory tract - upper and lower:

• The top ones are nasal cavity, including the paranasal sinuses, and the larynx - a voice-forming organ.
• The lower ones are the trachea and the bronchial tree.
• The respiratory organs are the lungs.

Each of these components is unique in its functions. Together, all these structures work as one well-coordinated mechanism.

nasal cavity

The first structure through which air passes when inhaling is the nose. Its structure:

1. The frame is made up of many small bones on which cartilage is attached. Depends on their shape and size appearance a person's nose.
2. Its cavity, according to anatomy, communicates with the external environment through the nostrils, while with the nasopharynx through special openings in the bone base of the nose (choana).
3. On the outer walls of both halves of the nasal cavity, 3 nasal passages are located from top to bottom. Through openings in them, the nasal cavity communicates with the paranasal sinuses and tear duct eyes.
4. From the inside, the nasal cavity is covered with a mucous membrane with a single-layer epithelium. She has many hairs and cilia. In this area, the air is sucked in, and also warmed and humidified. The hairs, cilia, and mucus layer in the nose act as an air filter, trapping dust particles and trapping microorganisms. The mucus secreted by epithelial cells contains bactericidal enzymes that can destroy bacteria.

Another important function of the nose is olfactory. V upper parts mucosa contains receptors olfactory analyzer. This area has a different color from the rest of the mucous membranes.

The olfactory zone of the mucous membrane is colored in yellowish color. From the receptors in its thickness, a nerve impulse is transmitted to specialized areas of the cerebral cortex, where the sense of smell is formed.

Paranasal sinuses

In the thickness of the bones that take part in the formation of the nose, there are voids lined from the inside with a mucous membrane - the paranasal sinuses. They are filled with air. This markedly reduces the weight of the skull bones.

The nasal cavity, together with the sinuses, takes part in the process of voice formation (the air resonates, and the sound becomes louder). There are such paranasal sinuses:

• Two maxillary (maxillary) - inside the bone of the upper jaw.
• Two frontal (frontal) - in the cavity frontal bone, above the superciliary arches.
• One wedge-shaped - at the base sphenoid bone(it is inside the skull).
• Cavities within the ethmoid bone.

All these sinuses communicate with the nasal passages through openings and channels. This leads to the fact that the inflammatory exudate from the nose enters the sinus cavity. The disease quickly spreads to nearby tissues. As a result, their inflammation develops: sinusitis, frontal sinusitis, sphenoiditis and ethmoiditis. These diseases are dangerous for their consequences: pus in advanced cases melts the walls of the bones, getting into the cranial cavity, causing irreversible changes in the nervous system.

Larynx

After passing through the nasal cavity and nasopharynx (or oral cavity, if a person breathes through the mouth), the air enters the larynx. It is a tubular organ of a very complex anatomy, which consists of cartilage, ligaments and muscles. It is here that the vocal cords are located, thanks to which we can make sounds of different frequencies. The functions of the larynx are air conduction, voice formation.

Structure:

1. The larynx is located at the level of 4-6 cervical vertebrae.
2. Its anterior surface is formed by the thyroid and cricoid cartilages. The back and upper parts are the epiglottis and small wedge-shaped cartilages.
3. The epiglottis is a "lid" that closes the larynx during a sip. This device is needed so that food does not get into airways.
4. From the inside, the larynx is lined with a single-layer respiratory epithelium, the cells of which have thin villi. They move by directing mucus and dust particles towards the throat. Thus, there is a constant purification of the airways. Only the surface of the vocal cords is lined with stratified epithelium, which makes them more resistant to damage.
5. There are receptors in the thickness of the mucous membrane of the larynx. When these receptors are irritated by foreign bodies, excess mucus, or waste products of microorganisms, a reflex cough occurs. This defensive reaction larynx, aimed at cleansing its lumen.

Trachea

From the lower edge of the cricoid cartilage begins the trachea. This organ belongs to the lower divisions respiratory tract. It ends at the level of 5–6 thoracic vertebrae at the site of its bifurcation (bifurcation).

The structure of the trachea:

1. The framework of the trachea forms 15–20 cartilaginous semirings. Behind, they are connected by a membrane that is adjacent to the esophagus.
2. At the point of division of the trachea into the main bronchi, there is a protrusion of the mucous membrane, which deviates to the left. This fact determines that foreign bodies that get here are more often found in the right main bronchus.
3. The mucous membrane of the trachea has good absorbability. It is used in medicine for intratracheal administration of drugs, by inhalation.

bronchial tree

The trachea divides into two main bronchi - tubular formations consisting of cartilage tissue that enter the lungs. The walls of the bronchi form cartilaginous rings and connective tissue membranes.

Inside the lungs, the bronchi are divided into lobar bronchi (second order), which, in turn, bifurcate several times into bronchi of the third, fourth, etc. up to the tenth order - terminal bronchioles. They give rise to respiratory bronchioles, components of the pulmonary acini.

Respiratory bronchioles pass into the respiratory passages. Alveoli are attached to these passages - sacs filled with air. It is at this level that gas exchange occurs, air cannot seep into the blood through the walls of the bronchioles.

Throughout the tree, bronchioles are lined from the inside with respiratory epithelium, and their wall is formed by cartilage elements. The smaller the caliber of the bronchus, the less cartilage tissue in its wall.

Smooth muscle cells appear in small bronchioles. This causes the ability of bronchioles to expand and narrow (in some cases even spasm). This happens under the influence external factors, impulses of the autonomic nervous system and some pharmaceuticals.

Lungs

The human respiratory system also includes the lungs. In the thickness of the tissues of these organs, gas exchange occurs between air and blood (external respiration).

Under the path of simple diffusion, oxygen moves to where its concentration is lower (into the blood). By the same principle, carbon monoxide is removed from the blood.

The exchange of gases through the cell is carried out due to the difference in the partial pressure of gases in the blood and the cavity of the alveoli. This process is based on the physiological permeability of the walls of the alveoli and capillaries to gases.

These are parenchymal organs that are located in the chest cavity on the sides of the mediastinum. The mediastinum contains the heart and large vessels(pulmonary trunk, aorta, superior and inferior vena cava), esophagus, lymphatic ducts, sympathetic nerve trunks and other structures.

The chest cavity is lined from the inside with a special membrane - the pleura, its other sheet covers each lung. As a result, two closed pleural cavities are formed, in which a negative (relative to atmospheric) pressure is created. This provides the person with the opportunity to inhale.

Its gate is located on the inner surface of the lung - this includes the main bronchi, vessels and nerves (all these structures form lung root). Right human lung consists of three parts, and the left - of two. This is due to the fact that the place of the third lobe of the left lung is occupied by the heart.

The parenchyma of the lungs consists of alveoli - cavities with air up to 1 mm in diameter. The walls of the alveoli are formed by connective tissue and alveolocytes - specialized cells that are able to pass oxygen and carbon dioxide bubbles through themselves.

The inside of the alveolus is covered thin layer viscous substance - surfactant. This fluid begins to be produced in the fetus at the 7th month of intrauterine development. It creates a surface tension force in the alveolus, which prevents it from subsiding during exhalation.

Together, the surfactant, the alveolocyte, the membrane on which it lies, and the wall of the capillary form an air-blood barrier. Microorganisms do not penetrate through it (normal). But if it occurs inflammatory process(pneumonia), capillary walls become permeable to bacteria.

Respiration is the process of exchanging gases such as oxygen and carbon between the internal environment of a person and the outside world. Human breathing is difficult regulated act joint work nerves and muscles. Their well-coordinated work ensures the implementation of inhalation - the supply of oxygen to the body, and exhalation - the removal of carbon dioxide into the environment.

The respiratory apparatus has a complex structure and includes: organs of the human respiratory system, muscles responsible for the acts of inhalation and exhalation, nerves that regulate the entire process of air exchange, as well as blood vessels.

Vessels are of particular importance for the implementation of breathing. Blood through the veins enters the lung tissue, where the exchange of gases takes place: oxygen enters, and carbon dioxide leaves. The return of oxygenated blood is carried out through the arteries, which transport it to the organs. Without the process of tissue oxygenation, breathing would have no meaning.

Respiratory function is assessed by pulmonologists. Important indicators while are:

1. Bronchial lumen width.
2. Breathing volume.
3. Inspiratory and expiratory reserve volumes.

A change in at least one of these indicators leads to a deterioration in well-being and is an important signal to additional diagnostics and treatment.

In addition, there are secondary functions that the breath performs. This:

1. Local regulation of the breathing process, due to which the vessels are adapted to ventilation.
2. Synthesis of various biologically active substances, carrying out the narrowing and expansion of blood vessels as needed.
3. Filtration, which is responsible for the resorption and decay of foreign particles, and even blood clots in small vessels.
4. Deposition of cells of the lymphatic and hematopoietic systems.

Stages of the breathing process

Thanks to nature, which invented such a unique structure and functions of the respiratory organs, it is possible to carry out such a process as air exchange. Physiologically, it has several stages, which, in turn, are regulated by the central nervous system, and only thanks to this they work like clockwork.

So, as a result of many years of research, scientists have identified the following stages, which collectively organize breathing. This:

1. External respiration - the delivery of air from the external environment to the alveoli. All organs of the human respiratory system take an active part in this.
2. Delivery of oxygen to organs and tissues by diffusion, as a result of this physical process tissue oxygenation occurs.
3. Respiration of cells and tissues. In other words, the oxidation of organic substances in cells with the release of energy and carbon dioxide. It is easy to understand that without oxygen, oxidation is impossible.

The value of breathing for a person

Knowing the structure and functions of the human respiratory system, it is difficult to overestimate the importance of such a process as breathing.

In addition, thanks to him, the exchange of gases between the internal and external environment is carried out. human body. The respiratory system is involved:

1. In thermoregulation, that is, it cools the body when elevated temperature air.
2. In the function of releasing random foreign substances such as dust, microorganisms and mineral salts, or ions.
3. In creating speech sounds, which is extremely important for social sphere person.
4. In the sense of smell.

Human breathing is complex physiological mechanism, which provides the exchange of oxygen and carbon dioxide between cells and the external environment.

Oxygen is constantly absorbed by cells and at the same time the process of removing carbon dioxide from the body, which is formed as a result of biochemical reactions flowing in the body.

Oxygen is involved in the oxidation reactions of complex organic compounds with their final decay to carbon dioxide and water, during which the energy necessary for life is formed.

In addition to the vital gas exchange, external respiration provides other important features in organism, for example, the ability to sound production.

This process involves the muscles of the larynx, respiratory muscles, vocal cords and oral cavity, and it itself is possible only when exhaling. The second important "non-respiratory" function is sense of smell.

Oxygen in our body is contained in a small amount - 2.5 - 2.8 liters, and about 15% of this volume is in a bound state.

At rest, a person consumes approximately 250 ml of oxygen per minute and removes about 200 ml of carbon dioxide.

Thus, when breathing stops, the supply of oxygen in our body is enough for only a few minutes, then damage and cell death occur, and the cells of the central nervous system suffer first of all.

For comparison: a person can live without water for 10-12 days (in the human body, the water supply, depending on age, is up to 75%), without food - up to 1.5 months.

With intensive physical activity oxygen consumption increases sharply and can reach up to 6 liters per minute.

Respiratory system

The function of respiration in the human body is carried out by the respiratory system which includes the organs external respiration(upper respiratory tract, lungs and chest, including its bone-cartilaginous frame and neuromuscular system), organs for the transport of gases by blood ( vascular system lungs, heart) and regulatory centers that ensure the automatism of the respiratory process.

Rib cage

The thorax forms the walls of the chest cavity, which houses the heart, lungs, trachea, and esophagus.

It consists of 12 thoracic vertebrae, 12 pairs of ribs, sternum and connections between them. front wall chest short, it is formed by the sternum and costal cartilages.

The back wall is formed by the vertebrae and ribs, the vertebral bodies are located in the chest cavity. The ribs are connected to each other and to the spine by movable joints and take an active part in breathing.

The spaces between the ribs are filled with intercostal muscles and ligaments. From the inside, the chest cavity is lined with parietal, or parietal, pleura.

respiratory muscles

The respiratory muscles are divided into those that inhale (inspiratory) and those that exhale (expiratory). The main inspiratory muscles include the diaphragm, external intercostal and internal intercartilaginous muscles.

The accessory inspiratory muscles include the scalene, sternocleidomastoid, trapezius, pectoralis major and minor.

The expiratory muscles include the internal intercostal, rectus, subcostal, transverse, as well as the external and internal oblique muscles of the abdomen.

The mind is the master of the senses, and the breath is the master of the mind.

Diaphragm

Since the thoracic septum, the diaphragm, has an extremely importance in the process of breathing, consider its structure and functions in more detail.

This extensive curved (bulge upward) plate completely delimits the abdominal and chest cavity.

The diaphragm is the main respiratory muscle and the most important organ of the abdominal press.

In it, a tendon center and three muscle parts are distinguished with names according to the organs from which they begin, respectively, the costal, sternal and lumbar regions are distinguished.

During contraction, the dome of the diaphragm moves away from the chest wall and flattens, thereby increasing the volume of the chest cavity and decreasing the volume abdominal cavity.

With simultaneous contraction of the diaphragm with the abdominal muscles, intra-abdominal pressure increases.

It should be taken into account that for tendon center diaphragms are attached parietal pleura, pericardium and peritoneum, that is, the movement of the diaphragm displaces the organs of the chest and abdominal cavity.

Airways

The airway refers to the path that air travels from the nose to the alveoli.

They are divided into airways located outside the chest cavity (these are nasal passages, pharynx, larynx and trachea) and intrathoracic airways (trachea, main and lobar bronchi).

The process of respiration can be conditionally divided into three stages:

External, or pulmonary, human respiration;

Transport of gases by blood (transportation of oxygen by blood to tissues and cells, while removing carbon dioxide from tissues);

Tissue (cellular) respiration, which is carried out directly in cells in special organelles.

External respiration of a person

We will consider the main function of the respiratory apparatus - external respiration, in which gas exchange occurs in the lungs, that is, the supply of oxygen to the respiratory surface of the lungs and the removal of carbon dioxide.

In the process of external respiration, the respiratory apparatus itself takes part, including the airways (nose, pharynx, larynx, trachea), lungs and inspiratory (respiratory) muscles, which expand the chest in all directions.

It is estimated that the average daily ventilation of the lungs is about 19,000-20,000 liters of air, and more than 7 million liters of air pass through the human lungs per year.

Pulmonary ventilation provides gas exchange in the lungs and is supplied by alternating inhalation (inspiration) and exhalation (expiration).

Inhale is active process due to the inspiratory (respiratory) muscles, the main of which are the diaphragm, external oblique intercostal muscles and internal intercartilaginous muscles.

The diaphragm is a muscle-tendon formation that delimits the abdominal and thoracic cavities, with its contraction, the volume of the chest increases.

With calm breathing, the diaphragm moves down by 2-3 cm, and with deep forced breathing, the excursion of the diaphragm can reach 10 cm.

When inhaling, due to the expansion of the chest, the volume of the lungs passively increases, the pressure in them becomes lower than atmospheric pressure, which makes it possible for air to penetrate into them. During inhalation, air initially passes through the nose, pharynx, and then enters the larynx. nasal breathing in humans it is very important, since when air passes through the nose, humidification and warming of the air occur. In addition, the epithelium lining the nasal cavity is able to retain small foreign bodies that enter with air. Thus, the airways also perform a cleansing function.

The larynx is located in the anterior region of the neck, from above it is connected to the hyoid bone, from below it passes into the trachea. Front and sides are right and left lobe thyroid gland. The larynx is involved in the act of breathing, protection of the lower respiratory tract and voice formation, consists of 3 paired and 3 unpaired cartilages. Of these formations in the process of breathing important role performs the epiglottis, which protects the airways from getting foreign bodies and food. The larynx is conventionally divided into three sections. In the middle section are the vocal cords, which form the narrowest point of the larynx - the glottis. Vocal cords play a major role in the process of sound formation, and the glottis - in breathing practice.

Air enters the trachea from the larynx. The trachea begins at the level of the 6th cervical vertebra; at the level of the 5th thoracic vertebrae, it divides into 2 main bronchi. The trachea itself and the main bronchi consist of open cartilaginous semicircles, which provides them permanent form and doesn't let them fall. The right bronchus is wider and shorter than the left, is located vertically and serves as a continuation of the trachea. It is divided into 3 lobar bronchus, as the right lung is divided into 3 lobes; left bronchus - into 2 lobar bronchi (the left lung consists of 2 lobes)

Then the lobar bronchi divide dichotomously (in two) into bronchi and bronchioles more small sizes, ending with respiratory bronchioles, at the end of which there are alveolar sacs, consisting of alveoli - formations in which, in fact, gas exchange occurs.

The walls of the alveoli contain a large number of tiny blood vessels- capillaries, which serve for gas exchange and further transportation of gases.

Bronchi with their branching into smaller bronchi and bronchioles (up to the 12th order, the wall of the bronchi includes cartilage tissue and muscles, this prevents the bronchi from collapsing during exhalation) outwardly resemble a tree.

Terminal bronchioles approach the alveoli, which are a branching of the 22nd order.

The number of alveoli in the human body reaches 700 million, and their total area is 160 m2.

By the way, our lungs have a huge reserve; at rest, a person uses no more than 5% of the respiratory surface.

Gas exchange at the level of the alveoli is continuous, it is carried out by the method of simple diffusion due to the difference in the partial pressure of gases (the percentage of the pressure of various gases in their mixture).

The percentage pressure of oxygen in the air is about 21% (in the exhaled air its content is approximately 15%), carbon dioxide - 0.03%.

Video "Gas exchange in the lungs":

calm exhalation- passive process due to several factors.

After the cessation of contraction of the inspiratory muscles, the ribs and sternum descend (due to gravity) and the chest decreases in volume, respectively, intrathoracic pressure increases (becomes higher than atmospheric pressure) and air rushes out.

The lungs themselves have elastic elasticity, which is aimed at reducing the volume of the lungs.

This mechanism is due to the presence of a film lining inner surface alveoli, which contains a surfactant - a substance that provides surface tension inside the alveoli.

So, when the alveoli are overstretched, the surfactant limits this process, trying to reduce the volume of the alveoli, while at the same time not allowing them to subside completely.

The mechanism of elastic elasticity of the lungs is also provided by the muscle tone of the bronchioles.

Active process involving accessory muscles.

During deep expiration, the abdominal muscles (oblique, rectus and transverse) act as expiratory muscles, with the contraction of which the pressure in the abdominal cavity increases and the diaphragm rises.

The auxiliary muscles that provide exhalation also include the intercostal internal oblique muscles and the muscles that flex the spine.

External respiration can be assessed using several parameters.

Respiratory volume. The amount of air that enters the lungs at rest. At rest, the norm is approximately 500-600 ml.

The volume of inhalation is slightly larger, since less carbon dioxide is exhaled than oxygen is supplied.

Alveolar volume. The part of the tidal volume that participates in gas exchange.

anatomical dead space. It is formed mainly due to the upper respiratory tract, which are filled with air, but do not themselves participate in gas exchange. It makes up about 30% of the respiratory volume of the lungs.

Inspiratory reserve volume. The amount of air that a person can additionally inhale after a normal breath (can be up to 3 liters).

Expiratory reserve volume. Residual air that can be exhaled after a quiet expiration (up to 1.5 liters in some people).

Breathing rate. The average is 14-18 respiratory cycles per minute. It usually increases with physical activity, stress, anxiety, when the body needs more oxygen.

Minute volume of lungs. It is determined taking into account the respiratory volume of the lungs and the respiratory rate per minute.

V normal conditions the duration of the exhalation phase is longer than the inhalation, approximately 1.5 times.

Of the characteristics of external respiration, the type of respiration is also important.

It depends on whether breathing is carried out only with the help of an excursion of the chest (thoracic, or costal, type of breathing) or the diaphragm takes the main part in the process of breathing (abdominal, or diaphragmatic, type of breathing).

Breathing is above consciousness.

For women, the thoracic type of breathing is more characteristic, although breathing with the participation of the diaphragm is physiologically more justified.

With this type of breathing, they are better ventilated lower divisions lungs, the respiratory and minute volume of the lungs increases, the body expends less energy on the breathing process (the diaphragm moves more easily than the bone and cartilage frame of the chest).

Breathing parameters throughout a person's life are automatically adjusted, depending on the needs at a certain time.

The respiratory control center consists of several links.

As the first link in regulation the need to maintain a constant level of oxygen and carbon dioxide tension in the blood.

These parameters are constant; with severe disorders, the body can exist for only a few minutes.

The second link of regulation- peripheral chemoreceptors located in the walls of blood vessels and tissues that respond to a decrease in the level of oxygen in the blood or to an increase in the level of carbon dioxide. Irritation of chemoreceptors causes a change in the frequency, rhythm and depth of breathing.

The third link of regulation- the respiratory center itself, which consists of neurons (nerve cells) located at various levels of the nervous system.

There are several levels of the respiratory center.

spinal respiratory center located at the level spinal cord, innervates the diaphragm and intercostal muscles; its significance is in changing the force of contraction of these muscles.

Central respiratory mechanism(rhythm generator) located in medulla oblongata and the pons, has the property of automatism and regulates breathing at rest.

Center located in the cortex hemispheres and hypothalamus, ensures the regulation of breathing during physical exertion and in a state of stress; the cerebral cortex allows you to arbitrarily regulate breathing, produce an unauthorized breath hold, consciously change its depth and rhythm, and so on.

It should be noted one more important point: deviation from the normal rhythm of breathing is usually accompanied by changes in other organs and systems of the body.

Simultaneously with a change in the respiratory rate, the heart rate is often disturbed and blood pressure becomes unstable.

We offer to watch the video a fascinating and informative film "The Miracle of the Respiratory System":

Breathe properly and stay healthy!