Upper parts of the respiratory system. Human respiratory system: organs, diseases, functions, structure
Without food, a person can live for several weeks, without water - only a few days, and without air, after 4 minutes, damage to brain cells occurs and eventually death. our body is truly a wonderful device.
How does a person work?
The respiratory tract consists of interconnected passages and tubes. Which way does air travel before it reaches the lungs? This long journey begins when air enters the throat through the mouth or nose. As you know, in the pharynx, the respiratory and digestive tracts intersect. To prevent food or liquid from entering the respiratory tract during swallowing, there is a small cover, known as the epiglottis, which closes the entrance to them.
Through the larynx past the air rushes into the trachea or windpipe(its length is 12 cm). Throughout its length, the trachea is reinforced by about twenty horseshoe-shaped cartilages. At the end, the trachea is divided into two tubes of 2.5 cm each - the main bronchi. They enter the right and left lungs, where they branch into many bronchi.
The branching of the bronchi resembles the structure of a tree with a trunk, branches, and thin branches and twigs. Each new branch becomes thinner. The air is directed into small branches - small vessels up to 1 mm in diameter, called bronchioles.
Further, the air fills 300,000 even smaller channels - the sacs of the alveoli. They are located in clusters in the lungs and look like tiny bubbles. This is where the tree-like respiratory system is completed and the air reaches its final destination.
The structure of the lungs - the main organ of the respiratory system
It is worth mentioning how ideally the lungs are located in our body - on both sides of the heart. Right lung includes three shares, and the left - two. Surgeons are helped by such anatomy: the respiratory system will work quite successfully even after some diseased lobe of the lung is removed.
Lung tissue resembles the structure of a sponge. His bottom the lungs are attached to the diaphragm. This is a strong muscular septum that separates the chest cavity from the abdominal cavity. The diaphragm is called the most important muscle of breathing, it is involved in the constant expansion and contraction of the lungs.
Each lung is covered by a thin membrane called the pleura. Inner side chest also covered with a similar shell. Between the layers is a lubricating fluid. Thanks to this structure, both the lungs and the chest slide freely during breathing.
Terminal vestibule of inhaled air
When the air reaches the alveoli, it comes into contact with the network of the finest blood vessels- pulmonary capillaries. Red blood cells (red blood cells) can pass through the capillaries only one at a time, their diameters are so narrow. Through thinnest walls(0.5 µm) passes into the alveolus. Oxygen leaves the alveoli and is taken up by red blood cells.
Only three quarters of one second a red blood cell remains in the capillaries. In this short time, carbon dioxide and oxygen have time to swap places. This amazing process of gas exchange is called diffusion. The blood enriched with oxygen enters the pulmonary veins and reaches the left half of the heart and from there is pumped throughout the body.
Imagine, it will take only a minute for all the blood to complete this whole complex respiratory relay race!
Breathing is an automatic system
Healthy lungs automatically take in air approximately 14 times per minute during breathing. Although this automation can be consciously suspended, it can only be done for a couple of minutes. For example, this is necessary while diving or in a gassed room, but after this time, the lungs, according to the ingenious program laid down in them, will inevitably switch back to automatic mode of operation. Where is the control center of this "automatic"? In the brainstem, special receptors monitor the amount of carbon dioxide in the blood. When the level exceeds the allowable mark, the brain will send signals through the network of nerves and the respiratory muscles will be forcibly activated by the body.
What a miracle it is - the respiratory system, presented to us by the Creator!
Breath- a set of processes that ensure the continuous supply of all organs and tissues of the body with oxygen and the removal from the body of carbon dioxide constantly formed in the process of metabolism.
There are several stages in the process of respiration:
1) external respiration, or ventilation of the lungs - the exchange of gases between the alveoli of the lungs and atmospheric air;
2) exchange of gases in the lungs between alveolar air and blood;
3) transport of gases by blood, i.e. the process of transferring oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs;
4) the exchange of gases between the blood of the capillaries of the systemic circulation and tissue cells;
5) internal respiration - biological oxidation in the mitochondria of the cell.
The main function of the respiratory system- ensuring the supply of oxygen to the blood and the removal of carbon dioxide from the blood.
Other functions of the respiratory system include:
– Participation in the processes of thermoregulation. The temperature of the inhaled air to a certain extent affects the body temperature. Together with the exhaled air, the body releases external environment warm, cooling down if possible (if the ambient temperature is below body temperature).
– Participation in the selection process. Together with the exhaled air, in addition to carbon dioxide, water vapor is removed from the body, as well as vapors of some other substances (for example, ethyl alcohol when intoxicated).
– Participation in immune responses. Some lung cells respiratory tract have the ability to neutralize pathogenic bacteria, viruses and other microorganisms.
The specific functions of the respiratory tract (nasopharynx, larynx, trachea and bronchi) are:
- warming or cooling of the inhaled air (depending on the ambient temperature);
- Humidification of the inhaled air (to prevent drying of the lungs);
- purification of the inhaled air from foreign particles - dust and others.
The human respiratory organs are represented by the airways through which inhaled and exhaled air passes, and the lungs, where gases are exchanged (Fig. 14).
nasal cavity. The respiratory tract begins with the nasal cavity, which is separated from the oral cavity in front by a hard palate and behind by a soft palate. The nasal cavity has a bone and cartilaginous framework and is divided by a solid partition into the right and left parts. It is divided by three nasal conchas into nasal passages: upper, middle and lower, through which the inhaled and exhaled air passes.
The nasal mucosa contains a number of devices for processing the inhaled air.
Firstly, it is covered with ciliated epithelium, the cilia of which form a continuous carpet on which dust settles. Thanks to the flickering of the cilia, the settled dust is expelled from the nasal cavity. The hairs located at the outer edge of the nasal openings also contribute to the retention of foreign particles.
Secondly, the mucous membrane contains mucous glands, the secret of which envelops dust and promotes its expulsion, and also humidifies the air. The mucus in the nasal cavity has bactericidal properties - it contains lysozyme, a substance that reduces the ability of bacteria to reproduce or kills them.
Thirdly, the mucous membrane is rich in venous vessels, which can swell when various conditions; damage to them causes nosebleeds. The significance of these formations is to heat the stream of air passing through the nose. Special studies have established that when air passes through the nasal passages with a temperature of +50 to -50 ° C and humidity from 0 to 100%, air “reduced” to 37 ° C and 100% humidity always enters the trachea.
On the surface of the mucosa from the blood vessels, leukocytes come out, which also perform protective function. Carrying out phagocytosis, they die, and therefore the mucus secreted from the nose contains many dead leukocytes.
Rice. 14. The structure of the human respiratory system
From the nasal cavity, air passes into the nasopharynx, from where it passes into the nasal part of the pharynx, and then into the larynx.
Rice. 15. The structure of the human larynx
Larynx. The larynx is located in front of the laryngeal part of the pharynx at the level of IV - VI cervical vertebrae and is formed by cartilages: unpaired - thyroid and cricoid, paired - arytenoid, corniculate and wedge-shaped (Fig. 15). The epiglottis is attached to the upper edge of the thyroid cartilage, which closes the entrance to the larynx during swallowing and thus prevents food from entering it. From the thyroid cartilage to the arytenoid (front to back) are two vocal cords. The space between them is called the glottis.
Rice. 16. The structure of the human trachea and bronchi
Trachea. The trachea, being a continuation of the larynx, begins at the level of the lower edge of VI cervical vertebra and ends at the level top edge V thoracic vertebra, where it divides into two bronchi - right and left. The place where the trachea divides is called the tracheal bifurcation. The length of the trachea ranges from 9 to 12 cm, with an average transverse diameter of 15–18 mm (Fig. 16).
The trachea consists of 16 to 20 incomplete cartilaginous rings connected by fibrous ligaments, each ring extending only two-thirds of the circumference. Cartilaginous semirings give elasticity to the airways and make them non-collapsible and thus easily passable for air. The posterior, membranous wall of the trachea is flattened and contains bundles of smooth muscle tissue running transversely and longitudinally and providing active movements of the trachea during breathing, coughing, etc. The mucous membrane of the larynx and trachea is covered with ciliated epithelium (with the exception of the vocal cords and part of the epiglottis) and is rich in lymphoid tissue and mucous glands.
Bronchi. The trachea divides into two bronchi, which enter the right and left lungs. In the lungs, the bronchi branch in a tree-like manner into smaller bronchi, which enter the pulmonary lobules and form even smaller respiratory branches - bronchioles. The smallest respiratory bronchioles with a diameter of about 0.5 mm branch into alveolar passages that end in alveolar sacs. Alveolar passages and sacs on the walls have protrusions in the form of bubbles, which are called alveoli. The diameter of the alveoli is 0.2 - 0.3 mm, and their number reaches 300 - 400 million, which creates a large respiratory surface of the lungs. It reaches 100 - 120 m 2.
Alveoli consist of a very thin squamous epithelium, which is surrounded on the outside by a network of tiny, also thin-walled, blood vessels, which facilitates the exchange of gases.
Lungs located in a hermetically sealed chest cavity. Back wall chest cavity is formed thoracic region spine and extending from the vertebrae, movably attached ribs. From the sides it is formed by the ribs, in front - by the ribs and the sternum. Between the ribs are the intercostal muscles (external and internal). From below, the chest cavity is separated from the abdominal cavity by the abdominal obstruction, or diaphragm, dome-shaped curved into the chest cavity.
A person has two lungs - right and left. The right lung has three lobes, the left has two. The narrowed upper part of the lungs is called the apex, and the expanded lower part is called the base. There are gates of the lung - a depression on their inner surface through which the bronchi, blood vessels (the pulmonary artery and two pulmonary veins) pass, lymphatic vessels and nerves. The combination of these formations is called lung root.
The tissue of the lung is made up of small structures called pulmonary lobules, which are small pyramid-shaped (0.5 - 1.0 cm across) sections of the lung. The bronchi included in the pulmonary lobule - the final bronchioles - are divided into 14 - 16 respiratory bronchioles. At the end of each of them there is a thin-walled extension - the alveolar duct. The system of respiratory bronchioles with their alveolar passages is the functional unit of the lungs and is called acinus.
The lungs are covered with a membrane - pleura, which consists of two sheets: internal (visceral) and external (parietal) (Fig. 17). The inner pleura covers the lungs and is their outer shell, which easily passes through the root into the outer pleura lining the walls of the chest cavity (it is its inner shell). Thus, between the inner and outer sheets of the pleura, a hermetically closed smallest capillary space is formed, which is called the pleural cavity. It contains not a large number of(1 - 2 ml) of pleural fluid, which wets the pleura and facilitates their sliding relative to each other.
Rice. 17. The structure of the lung human
One of the main reasons for the change of air in the lungs is a change in the volume of the chest and pleural cavities. The lungs passively follow the change in their volume.
The mechanism of the act of inhalation and exhalation
The exchange of gases between atmospheric air and the air in the alveoli occurs due to the rhythmic alternation of inhalation and exhalation. There is no muscle tissue in the lungs, and therefore they cannot actively contract. An active role in the act of inhalation and exhalation belongs to the respiratory muscles. With paralysis of the respiratory muscles, breathing becomes impossible, although the respiratory organs are not affected.
The act of inhalation, or inspiration- an active process, which is provided by an increase in the volume of the chest cavity. The act of exhalation, or expiration- a passive process that occurs as a result of a decrease in the volume of the chest cavity. The phases of inhalation and subsequent exhalation are respiratory cycle. During inhalation, atmospheric air enters the lungs through the airways, and during exhalation, part of the air leaves them.
In the implementation of inspiration, the external oblique intercostal muscles and the diaphragm take part (Fig. 18). With the contraction of the external oblique intercostal muscles, which go from top to front and down, the ribs rise, and at the same time, the volume of the chest cavity increases due to the displacement of the sternum forward and the departure of the lateral parts of the ribs to the sides. The diaphragm, contracting, occupies a flatter position. In this case, the incompressible organs of the abdominal cavity are pushed down and to the sides, stretching the walls of the abdominal cavity. With a quiet breath, the dome of the diaphragm descends by approximately 1.5 cm, respectively increases vertical dimension chest cavity.
With very deep breathing, a number of auxiliary respiratory muscles participate in the act of inhalation: scalene, pectoralis major and minor, serratus anterior, trapezius, rhomboid, levator scapulae.
The lungs and the wall of the chest cavity are covered with a serous membrane - the pleura, between the sheets of which there is a narrow gap - the pleural cavity containing serous fluid. The lungs are constantly in a stretched state, because the pressure in the pleural cavity is negative. It is due elastic traction lungs, i.e., the constant desire of the lungs to reduce their volume. At the end of a quiet exhalation, when almost all respiratory muscles are relaxed, the pressure in the pleural cavity is approximately -3 mm Hg. Art., i.e. below atmospheric.
Rice. 18. Muscles that provide inhalation and exhalation
During inhalation, due to the contraction of the respiratory muscles, the volume of the chest cavity increases. The pressure in the pleural cavity becomes more negative. By the end of a quiet breath, it decreases to -6 mm Hg. Art. At the time of a deep breath, it can reach -30 mm Hg. Art. The lungs expand, their volume increases, and air is sucked into them.
At different people the intercostal muscles or the diaphragm may be of primary importance in the implementation of the act of inhalation. Therefore, they speak of different types of breathing: chest, or costal, and abdominal, or diaphragmatic. It has been established that in women, the thoracic type of breathing mainly prevails, and in men - abdominal.
With calm breathing, exhalation is carried out due to the elastic energy accumulated during the previous inhalation. When the respiratory muscles relax, the ribs passively return to their original position. The cessation of contraction of the diaphragm leads to the fact that it takes its former domed position due to pressure on it from the abdominal organs. The return of the ribs and the diaphragm to its original position leads to a decrease in the volume of the chest cavity, and, consequently, to a decrease in pressure in it. At the same time, when the ribs return to their original position, the pressure in the pleural cavity increases, i.e., the negative pressure in it decreases. All these processes, which provide an increase in pressure in the chest and pleural cavities, lead to the fact that the lungs are compressed, and air is passively released from them - exhalation is carried out.
Forced exhalation is an active process. The following are involved in its implementation: internal intercostal muscles, the fibers of which run in the opposite direction compared to the external ones: from bottom to top and forward. With their contraction, the ribs go down, and the volume of the chest cavity decreases. Strengthened exhalation is also facilitated by contraction of the abdominal muscles, as a result of which the volume of the abdominal cavity decreases and the pressure in it increases, which is transmitted through the abdominal organs to the diaphragm and raises it. Finally, the muscles of the girdle of the upper extremities, contracting, squeeze the chest in the upper part and reduce its volume.
As a result of a decrease in the volume of the chest cavity, pressure increases in it, as a result of which air is pushed out of the lungs - an active exhalation occurs. At the apex of exhalation, the pressure in the lungs can be 3–4 mm Hg greater than atmospheric pressure. Art.
The acts of inhalation and exhalation rhythmically replace each other. An adult does 15 - 20 cycles per minute. The breathing of physically trained people is rarer (up to 8 - 12 cycles per minute) and deep.
Respiratory organs include: nasal cavity, pharynx. larynx, trachea, bronchi and lungs. The nasal cavity is divided by an osteochondral septum into two halves. Its inner surface is formed by three winding passages. Through them, air entering through the nostrils passes into the nasopharynx. Numerous glands located in the mucous membrane secrete mucus, which moisturizes the inhaled air. An extensive blood supply to the mucous membrane warms the air. On the moist surface of the mucous membrane, dust particles and microbes, which are neutralized by mucus and leukocytes, are retained in the inhaled air.
The mucous membrane of the respiratory tract is lined with ciliated epithelium, whose cells have on outside the surface of the thinnest outgrowths - cilia that can contract. The contraction of the cilia occurs rhythmically and is directed towards the exit from the nasal cavity. In this case, mucus and dust particles and microbes adhering to it are carried out of the nasal cavity. So the air passing through nasal cavity, warmed and cleaned of dust and some germs. This does not happen when air enters the body through the mouth. That is why you should breathe through your nose and not through your mouth. Through the nasopharynx, air enters the larynx.
The larynx has the appearance of a funnel, the walls of which are formed by several cartilages. The entrance to the larynx during swallowing food is closed by the epiglottis, the thyroid cartilage, which can be easily felt from the outside. The larynx serves to conduct air from the pharynx to the trachea.
The trachea, or windpipe, is a tube about 10 cm long and 15–18 mm in diameter, the walls of which consist of cartilaginous half-rings interconnected by ligaments. The back wall is membranous, contains smooth muscle fibers, adjacent to the esophagus. The trachea divides into two main bronchi, which enter the right and left lungs and branch into them, forming the so-called bronchial tree.
On the terminal bronchial branches there are the smallest pulmonary vesicles - alveoli, 0.15–0.25 mm in diameter and 0.06–0.3 mm deep, filled with air. The walls of the alveoli are lined with a single-layer squamous epithelium, covered with a dense film of a substance that prevents them from falling off. The alveoli are permeated with a dense network of blood vessels - capillaries. Gas exchange occurs through their walls.
The lungs are covered with a membrane - the pulmonary pleura, which passes into the parietal pleura, lining inner wall chest cavity. The narrow space between the pulmonary and parietal pleura forms pleural fissure filled pleural fluid. Its role is to facilitate the sliding of the pleura during respiratory movements.
Human breathing is complex physiological mechanism, which provides the exchange of oxygen and carbon dioxide between cells and the external environment.
Oxygen is constantly taken up by cells and at the same time there is a process removal of carbon dioxide from the body, which is formed as a result of biochemical reactions occurring in the body.
Oxygen is involved in the oxidation reactions of complex organic compounds with their final decomposition 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 the body, 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 lasts 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 intense physical activity, oxygen consumption increases dramatically 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 of external respiration (upper respiratory tract, lungs and chest, including its bone and cartilage 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. The anterior wall of the chest is 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 thoracic cavities.
The diaphragm is the main respiratory muscle and the most important body 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 of the abdominal cavity.
With simultaneous contraction of the diaphragm with the abdominal muscles, intra-abdominal pressure increases.
It should be noted that the parietal pleura, pericardium and peritoneum are attached to the tendon center of the diaphragm, 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 the 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).
Inhalation is an 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 muscular-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 is very important, because when air passes through the nose, the air is moistened and warmed. 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. In front and from the sides are the right and left lobes of the 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, the epiglottis plays an important role in the process of breathing, which protects the respiratory tract from 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. The vocal cords play a major role in the process of sound production, and the glottis plays a major role 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 ensures their constant shape and prevents them from collapsing. 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 bronchi, 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 of smaller 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.
In the walls of the alveoli there is 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 the inner surface of the 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.
AT 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, the lower sections of the lungs are better ventilated, 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 on various levels 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 cerebral cortex 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 unauthorized breath holding, consciously change its depth and rhythm, and so on.
It should be noted one more important point: deviation from normal rhythm 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!
Functions of the respiratory system
STRUCTURE OF THE RESPIRATORY SYSTEM
Control questions
1. What organs are called parenchymal?
2. What membranes are isolated in the walls of hollow organs?
3. What organs form the walls of the oral cavity?
4. Tell us about the structure of the tooth. How do different types of teeth differ in shape?
5. What are the terms of eruption of milk and permanent teeth. Write the complete formula of milk and permanent teeth.
6. What papillae are there on the surface of the tongue?
7. Name the anatomical muscle groups of the tongue, the function of each muscle of the tongue.
8. List the groups of small salivary glands. Where do the ducts of the major salivary glands open in the oral cavity?
9. Name the muscles soft palate, places of their origin and attachment.
10. In what places does the esophagus have narrowings, what causes them?
11. At the level of which vertebrae are the entrance and exit openings of the stomach located? Name the ligaments (peritoneal) of the stomach.
12. Describe the structure and functions of the stomach.
13. What is the length and thickness of the small intestine?
14. What anatomical formations are visible on the surface of the mucous membrane of the small intestine throughout its entire length?
15. How does the structure of the large intestine differ from the small intestine?
16. Where on the front abdominal wall converge lines of projections of the upper and lower boundaries of the liver? Describe the structure of the liver and gallbladder.
17. What organs does the visceral surface of the liver come into contact with? Name the size and volume of the gallbladder.
18. How is digestion regulated?
1. Supplying the body with oxygen and removing carbon dioxide;
2. Thermoregulatory function (up to 10% of the heat in the body is spent on the evaporation of water from the surface of the lungs);
3. Excretory function - removal of carbon dioxide, water vapor, volatile substances (alcohol, acetone, etc.) with exhaled air;
4. Participation in water exchange;
5. Participation in maintaining acid-base balance;
6. The largest blood depot;
7. Endocrine function - hormone-like substances are formed in the lungs;
8. Participation in sound reproduction and speech formation;
9. Protective function;
10. Perception of smells (smell), etc.
Respiratory system ( systems respiratorium) consists of the airways and respiratory organs- lungs (Fig. 4.1; Table 4.1). The airways are divided into upper and lower airways according to their position in the body. lower divisions. The upper respiratory tract includes the nasal cavity, the nasal part of the pharynx, the oral part of the pharynx, and the lower respiratory tract includes the larynx, trachea, bronchi, including the intrapulmonary branches of the bronchi.
Rice. 4.1. Respiratory system. 1 - oral cavity; 2 - nasal part of the pharynx; 3 - soft palate; 4 - language; 5 - oral part of the pharynx; 6 - epiglottis; 7- guttural part pharynx; 8 - larynx; 9 - esophagus; 10 - trachea; 11 - the top of the lung; 12 - upper lobe of the left lung; 13 - left main bronchus; 14 - lower lobe of the left lung; 15 - alveoli; 16 - right main bronchus; 17 - right lung; 18 - hyoid bone; 19 - lower jaw; 20 - vestibule of the mouth; 21 - oral fissure; 22 - hard palate; 23 - nasal cavity
The respiratory tract consists of tubes, the lumen of which is preserved due to the presence of a bone or cartilaginous skeleton in their walls. This morphological feature is fully consistent with the function of the respiratory tract - conducting air into the lungs and out of the lungs. The inner surface of the respiratory tract is covered with a mucous membrane, which is lined with ciliated epithelium, contains significant
Table 4.1. The main characteristic of the respiratory system
| Oxygen transport | Oxygen delivery route | Structure | Functions |
| upper respiratory tract | nasal cavity | The beginning of the respiratory tract. From the nostrils, air passes through the nasal passages, lined with mucous and ciliated epithelium. | Humidification, warming, air disinfection, removal of dust particles. Olfactory receptors are located in the nasal passages |
| Pharynx | Consists of the nasopharynx and the oral part of the pharynx, passing into the larynx | Carrying warm and purified air into the larynx | |
| Larynx | A hollow organ, in the walls of which there are several cartilages - thyroid, epiglottis, etc. Between the cartilages are the vocal cords that form the glottis | Conduction of air from the pharynx to the trachea. Protection of the respiratory tract from food ingestion. Formation of sounds by vibration of the vocal cords, movement of the tongue, lips, jaw | |
| Trachea | The respiratory tube is about 12 cm long, cartilaginous semirings are located in its wall. | ||
| Bronchi | The left and right bronchi are formed by cartilaginous rings. In the lungs, they branch into small bronchi, in which the amount of cartilage gradually decreases. The terminal branches of the bronchi in the lungs are the bronchioles. | Free air movement | |
| Lungs | Lungs | The right lung has three lobes, the left has two. They are located in the chest cavity of the body. covered with pleura. They lie in pleural sacs. Have spongy structure | Respiratory system. Breathing movements carried out under the control of the central nervous system and the humoral factor contained in the blood - CO 2 |
| Alveoli | Pulmonary vesicles, consisting of a thin layer of squamous epithelium, densely entwined with capillaries, form the endings of bronchioles. | Increase the area of the respiratory surface, carry out gas exchange between the blood and the lungs |
the number of glands that secrete mucus. Due to this, it performs a protective function. Passing through the respiratory tract, the air is purified, warmed and humidified. In the process of evolution, a larynx was formed on the path of the air stream - it is difficult organized body, which performs the function of voice formation. Through the respiratory tract, air enters the lungs, which are the main organs of the respiratory system. In the lungs, gas exchange occurs between air and blood by diffusion of gases (oxygen and carbon dioxide) through the walls of the pulmonary alveoli and adjacent blood capillaries.
nasal cavity (cavitalis nasi) includes the external nose and the nasal cavity proper (Fig. 4.2).
Rice. 4.2. Nasal cavity. Sagittal section.
External nose includes the root, back, apex and wings of the nose. nose root located in the upper part of the face and separated from the forehead by a notch - the nose bridge. The sides of the external nose are connected along the midline and form the back of the nose, and the lower parts of the sides are the wings of the nose, which limit the nostrils with their lower edges , serving for the passage of air into the nasal cavity and out of it. Along the midline, the nostrils are separated from each other by the movable (webbed) part of the nasal septum. The external nose has a bone and cartilaginous skeleton formed by the nasal bones, frontal processes upper jaws and several hyaline cartilages.
The actual nasal cavity divided by the nasal septum into two almost symmetrical parts, which open in front on the face with nostrils , and behind through the choanae , communicate with the nasal part of the pharynx. In each half of the nasal cavity, a nasal vestibule is isolated, which is bounded from above by a small elevation - the threshold of the nasal cavity, formed by the upper edge of the large cartilage of the wing of the nose. The vestibule is covered from the inside by the skin of the external nose continuing here through the nostrils. The skin of the vestibule contains sebaceous, sweat glands and hard hair - vibris.
Most of The nasal cavity is represented by the nasal passages, with which the paranasal sinuses communicate. There are upper, middle and lower nasal passages, each of them is located under the corresponding nasal concha. Behind and above the superior turbinate is a sphenoid-ethmoid depression. Between the nasal septum and the medial surfaces of the turbinates is a common nasal passage, which looks like a narrow vertical slit. The posterior cells of the ethmoid bone open into the upper nasal passage with one or more openings. Side wall middle nasal passage forms a rounded protrusion towards the nasal concha - a large ethmoid vesicle. In front and below the large ethmoid vesicle there is a deep semilunar cleft , through which the frontal sinus communicates with the middle nasal passage. Middle and anterior cells (sinuses) of the ethmoid bone, frontal sinus, maxillary sinus open into the middle nasal passage. The lower opening of the nasolacrimal duct leads to the inferior nasal passage.
Nasal mucosa continues into the mucous membrane of the paranasal sinuses, lacrimal sac, nasal part of the pharynx and soft palate (through the choanae). It is tightly fused with the periosteum and perichondrium of the walls of the nasal cavity. In accordance with the structure and function in the mucous membrane of the nasal cavity, the olfactory (part of the membrane covering the right and left upper nasal conchas and part of the middle ones, as well as the corresponding upper section of the nasal septum containing olfactory neurosensory cells) and the respiratory region (the rest of the mucous membrane nose). The mucous membrane of the respiratory region is covered with ciliated epithelium, it contains mucous and serous glands. In the region of the lower shell, the mucous membrane and submucosa are rich in venous vessels, which form cavernous venous plexuses of the shells, the presence of which contributes to the warming of the inhaled air.
Larynx(larynx) performs the functions of breathing, voice formation and protection of the lower respiratory tract from foreign particles entering them. It occupies a middle position in the anterior region of the neck, forms a barely noticeable (in women) or strongly protruding forward (in men) elevation - a protrusion of the larynx (Fig. 4.3). Behind the larynx is the laryngeal part of the pharynx. The close connection of these organs is explained by the development of the respiratory system from the ventral wall of the pharyngeal intestine. In the pharynx there is a crossroads of the digestive and respiratory tracts.
larynx cavity can be divided into three sections: the vestibule of the larynx, the interventricular section and the subvocal cavity (Fig. 4.4).
Throat vestibule extends from the entrance to the larynx to the folds of the vestibule. The anterior wall of the vestibule (its height is 4 cm) is formed by a mucous membrane-covered epiglottis, and the posterior (1.0–1.5 cm in height) is formed by arytenoid cartilages.
Rice. 4.3. Larynx and thyroid gland.
Rice. 4.4. The cavity of the larynx on the sagittal section.
Interventricular department- the narrowest, extending from the folds of the vestibule above to the vocal folds below. Between the fold of the vestibule (false vocal fold) and the vocal fold on each side of the larynx is the ventricle of the larynx . The right and left vocal folds limit the glottis, which is the narrowest part of the larynx cavity. The length of the glottis (anteroposterior size) in men reaches 20-24 mm, in women - 16-19 mm. The width of the glottis during quiet breathing is 5 mm, during voice formation it reaches 15 mm. With the maximum expansion of the glottis (singing, screaming), tracheal rings are visible up to its division into the main bronchi.
lower division laryngeal cavity located under the glottis subvocal cavity, gradually expands and continues into the tracheal cavity. The mucous membrane lining the cavity of the larynx is pink color, covered with ciliated epithelium, contains many serous-mucous glands, especially in the region of the folds of the vestibule and ventricles of the larynx; glandular secretion moisturizes the vocal folds. In the region of the vocal folds, the mucous membrane is covered with stratified squamous epithelium, tightly fuses with the submucosa and does not contain glands.
Cartilages of the larynx. The skeleton of the larynx is formed by paired (arytenoid, corniculate and wedge-shaped) and unpaired (thyroid, cricoid and epiglottis) cartilages.
Thyroid cartilage – hyaline, unpaired, the largest of the cartilages of the larynx, consists of two quadrangular plates connected to each other in front at an angle of 90 o (in men) and 120 o (in women) (Fig. 4.5). In front of the cartilage there is an upper thyroid notch and a weakly expressed inferior thyroid notch. The posterior edges of the plates of the thyroid cartilage form a longer upper horn on each side and a short lower horn.
Rice. 4.5. Thyroid cartilage. A - front view; B - rear view. B - top view (with cricoid cartilage).
Cricoid cartilage- hyaline, unpaired, shaped like a ring, consists of an arc and a quadrangular plate. On the upper edge of the plate at the corners there are two articular surfaces for articulation with the right and left arytenoid cartilages. At the point of transition of the arc of the cricoid cartilage into its plate, on each side there is an articular platform for connection with the lower horn of the thyroid cartilage.
arytenoid cartilage – hyaline, paired, similar in shape to a trihedral pyramid. The vocal process protrudes from the base of the arytenoid cartilage, formed by elastic cartilage to which the vocal cord is attached. Laterally from the base of the arytenoid cartilage, its muscular process departs for muscle attachment.
At the apex of the arytenoid cartilage in the thickness back section aryepiglottic fold lies corniculate cartilage. This is a paired elastic cartilage that forms a corniculate tubercle protruding above the top of the arytenoid cartilage.
sphenoid cartilage – paired, elastic. The cartilage is located in the thickness of the scoop-epiglottic fold, where it forms a wedge-shaped tubercle protruding above it. .
Epiglottis is based on epiglottic cartilage - unpaired, elastic in structure, leaf-shaped, flexible. The epiglottis is located above the entrance to the larynx, covering it from the front. The narrower lower end is the stalk of the epiglottis , attached to the inner surface of the thyroid cartilage.
Cartilage joints of the larynx. The cartilages of the larynx are connected to each other, as well as to the hyoid bone with the help of joints and ligaments. The mobility of the cartilage of the larynx is ensured by the presence of two paired joints and the action of the corresponding muscles on them (Fig. 4.6).
Rice. 4.6. Joints and ligaments of the larynx. Front view (A) and rear view (B)
cricothyroid joint- This is a paired, combined joint. Movement is carried out around the frontal axis passing through the middle of the joint. Leaning forward increases the distance between the angle of the thyroid cartilage and the arytenoid cartilages.
cricoarytenoid joint- paired, formed by a concave articular surface on the basis of the arytenoid cartilage and a convex articular surface on the plate of the cricoid cartilage. Movement in the joint occurs around a vertical axis. When rotating right and left arytenoid cartilages inward (under the action of the corresponding muscles), the vocal processes, together with the vocal cords attached to them, converge (the glottis narrows), and when rotated outward, they are removed, diverge to the sides (the glottis expands). In the cricoarytenoid joint, sliding is also possible, in which the arytenoid cartilages either move away from each other or approach each other. When the arytenoid cartilages slide, approaching each other, the posterior intercartilaginous part of the glottis narrows.
Along with the joints, the cartilages of the larynx are connected to each other, as well as to the hyoid bone by means of ligaments ( continuous connections). Between the hyoid bone and the upper edge of the thyroid cartilage, the median shield-hyoid ligament is stretched. Along the edges, the lateral shield-hyoid ligaments can be distinguished. The anterior surface of the epiglottis is attached to the hyoid bone by the hyoid-epiglottic ligament, and to the thyroid cartilage by the thyroid-epiglottic ligament.
Muscles of the larynx. All muscles of the larynx can be divided into three groups: dilators of the glottis (posterior and lateral cricoarytenoid muscles, etc.), constrictors (thychoarytenoid, anterior and oblique arytenoid muscles, etc.) and muscles that stretch (strain) the vocal cords (cricothyroid and vocal muscles).
Trachea ( trachea) is an unpaired organ that serves to pass air into and out of the lungs. It starts from the lower border of the larynx at the level of the lower edge of the VI cervical vertebra and ends at the level of the upper edge of the V thoracic vertebra, where it divides into two main bronchi. This place is called bifurcation of the trachea (Fig. 4.7).
The trachea is in the form of a tube 9 to 11 cm long, somewhat compressed from front to back. The trachea is located in the neck area - the cervical part , and in the thoracic cavity - the thoracic part. In the cervical region, the thyroid gland is adjacent to the trachea. Behind the trachea is the esophagus, and on the sides of it are the right and left neurovascular bundles (common carotid artery, internal jugular vein and vagus nerve). In the chest cavity in front of the trachea are the aortic arch, the brachiocephalic trunk, the left brachiocephalic vein, the beginning of the left common carotid artery and the thymus (thymus gland).
To the right and left of the trachea is the right and left mediastinal pleura. The wall of the trachea consists of a mucous membrane, submucosa, fibrous-muscular-cartilaginous and connective tissue membranes. The basis of the trachea are 16–20 cartilaginous hyaline semirings, occupying about two thirds of the circumference of the trachea, with the open part facing backwards. Thanks to the cartilaginous half-rings, the trachea has flexibility and elasticity. Neighboring cartilages of the trachea are interconnected by fibrous annular ligaments.
Rice. 4.7. Trachea and bronchi. Front view.
main bronchi ( bronchi principales)(right and left) depart from the trachea at the level of the upper edge of the V thoracic vertebra and go to the gate of the corresponding lung. The right main bronchus has a more vertical direction, it is shorter and wider than the left one, and serves (in direction) as if a continuation of the trachea. Therefore, foreign bodies get into the right main bronchus more often than into the left one.
The length of the right bronchus (from the beginning to branching into the lobar bronchi) is about 3 cm, the left - 4-5 cm. Above the left main bronchus lies the aortic arch, above the right - the unpaired vein before it flows into the superior vena cava. The wall of the main bronchi in its structure resembles the wall of the trachea. Their skeleton is cartilaginous half-rings (in the right bronchus 6-8, in the left 9-12), behind the main bronchi have a membranous wall. From the inside, the main bronchi are lined with a mucous membrane, outside they are covered with a connective tissue membrane (adventitia).
Lung (rito). The right and left lungs are located in the chest cavity, in its right and left halves, each in its own pleural sac. Lungs located in pleural sacs, separated from each other mediastinum which contains the heart, large vessels(aorta, superior vena cava), esophagus and other organs. Below the lungs are adjacent to the diaphragm, in front, side and back, each lung is in contact with the chest wall. The left lung is narrower and longer, here part of the left half of the chest cavity is occupied by the heart, which is turned to the left with its apex (Fig. 4.8).
Rice. 4.8. Lungs. Front view.
The lung has the shape of an irregular cone with a flattened one side (facing the mediastinum). With the help of slits deeply protruding into it, it is divided into lobes, of which the right has three (upper, middle and lower), the left has two (upper and lower).
On the medial surface of each lung, slightly above its middle, there is an oval depression - the gate of the lung, through which the main bronchus, pulmonary artery, nerves enter the lung, and the pulmonary veins and lymphatic vessels exit. These formations make up the root of the lung.
At the gates of the lung, the main bronchus splits into lobar bronchi, of which there are three in the right lung, and two in the left, which are also divided into two or three segmental bronchi each. The segmental bronchus is included in the segment, which is a section of the lung, the base facing the surface of the organ, and the apex - to the root. The pulmonary segment consists of pulmonary lobules. The segmental bronchus and segmental artery are located in the center of the segment, and the segmental vein is located on the border with the neighboring segment. The segments are separated from each other by connective tissue (small vascular zone). The segmental bronchus is divided into branches, of which there are approximately 9–10 orders (Fig. 4.9, 4.10).
Rice. 4.9. Right lung. Medial (inner) surface. 1-apex of the lung: 2-furrow subclavian artery; 3-pressure of the unpaired vein; 4-broncho-pulmonary The lymph nodes; 5-right main bronchus; 6-right pulmonary artery; 7-furrow - unpaired vein; 8-posterior edge of the lung; 9-pulmonary veins; 10-pi-aqueous impression; 11-pulmonary ligament; 12- depression of the inferior vena cava; 13-diaphragmatic surface (lower lobe of the lung); 14-lower edge of the lung; 15-middle lobe of the lung:. 16-heart depression; 17-oblique slot; 18-front edge of the lung; 19-upper lobe of the lung; 20-visceral pleura (cut off): 21-sulcus of the right and leuchocephalic vein
Rice. 4.10. Left lung. Medial (inner) surface. 1-apex of the lung, 2-groove of the left subclavian artery, 2-groove of the left brachiocephalic vein; 4-left pulmonary artery, 5-left main bronchus, 6-anterior edge of the left lung, 7-lung veins (left), 8-upper lobe of the left lung, 9-cardiac depression, 10-cardiac notch of the left lung, 11- oblique fissure, 12-uvula of the left lung, 13-inferior edge of the left lung, 14-diaphragmatic surface, 15-lower lobe of the left lung, 16-pulmonary ligament, 17-broncho-pulmonary lymph nodes, 18-aortic groove, 19-visceral pleura (cut off), 20-oblique slit.
A bronchus with a diameter of about 1 mm, still containing cartilage in its walls, enters a lung lobule called a lobular bronchus. Inside the pulmonary lobule, this bronchus divides into 18–20 terminal bronchioles. , of which there are about 20,000 in both lungs. The walls of the terminal bronchioles do not contain cartilage. Each terminal bronchiole is divided dichotomously into respiratory bronchioles, which have pulmonary alveoli on their walls.
From each respiratory bronchiole, alveolar passages depart, bearing the alveoli and ending in the alveolar and sacs. The bronchi of various orders, starting from the main bronchus, which serve to conduct air during breathing, make up the bronchial tree (Fig. 4.11). Respiratory bronchioles extending from the terminal bronchioles, as well as alveolar ducts, alveolar sacs and alveoli of the lung form the alveolar tree (pulmonary acinus). The alveolar tree, in which gas exchange between air and blood occurs, is a structural and functional unit of the lung. The number of pulmonary acini in one lung reaches 150,000, the number of alveoli is approximately 300–350 million, and the respiratory surface area of all alveoli is about 80 m 2 ..
Rice. 4.11. Branching of the bronchi in the lung (scheme).
Pleura (pleura) - the serous membrane of the lung, is divided into visceral (pulmonary) and parietal (parietal). Each lung is covered with a pleura (pulmonary), which, along the surface of the root, passes into the parietal pleura, which lines the walls of the chest cavity adjacent to the lung and delimits the lung from the mediastinum. Visceral (lung) pleura densely fuses with the tissue of the organ and, covering it from all sides, enters the gaps between lung lobes. Down from the root of the lung, the visceral pleura descends from the anterior and rear surfaces root of the lung, forms a vertically located pulmonary ligament, llgr. pulmonale, lying in the frontal plane between the medial surface of the lung and the mediastinal pleura and descending almost to the diaphragm. Parietal (parietal) pleura is a continuous sheet that fuses with inner surface chest wall and in each half of the chest cavity forms a closed sac containing the right or left lung, covered with a visceral pleura. Based on the position of the parts of the parietal pleura, the costal, mediastinal and diaphragmatic pleura are distinguished in it.
RESPIRATORY CYCLE consists of inhalation, exit and respiratory pause. The duration of inhalation (0.9-4.7 s) and exhalation (1.2-6 s) depends on reflex influences from the side lung tissue. The frequency and rhythm of breathing is determined by the number of chest excursions per minute. At rest, an adult makes 16-18 breaths per minute.
Table 4.1. The content of oxygen and carbon dioxide in the inhaled and exhaled air
Rice. 4.12. The exchange of gases between the blood and air of the alveoli: 1 - the lumen of the alveoli; 2 - wall of the alveoli; 3 - wall blood capillary; 4 – capillary lumen; 5 - erythrocyte in the lumen of the capillary. The arrows show the path of oxygen, carbon dioxide through the air-blood barrier (between blood and air).
Table 4.2. Respiratory volumes.
| Index | Peculiarities |
| Tidal volume (TO) | The amount of air that a person inhales and exhales during quiet breathing (300-700 ml) |
| Inspiratory reserve volume (RIV) | The volume of air that can be inhaled after a normal breath (1500-3000 ml) |
| Expiratory reserve volume (ERV) | The volume of air that can be exhaled additional after a normal exhalation (1500-2000 ml) |
| Residual volume (RO) | The volume of air that remains in the lungs after the deepest exhalation (1000-1500 ml) |
| Vital capacity (VC) | Most deep breathing, which a person is capable of: DO + ROVD + ROVID (3000-4500ml) |
| Total lung capacity (TLC) | YEL+OO. The amount of air in the lungs after maximum inspiration (4000-6000 ml) |
| Pulmonary ventilation or respiratory minute volume (MV) | DO * number of breaths in 1 minute (6-8 l / min). An indicator of the renewal of the composition of the alveolar gas. Associated with overcoming the elastic resistance of the lungs and resistance to the respiratory air flow (neelatic resistance) |
MEDIASTINUM (mediastinum) is a complex of organs located between the right and left pleural cavities. The mediastinum is bounded anteriorly by the sternum, posteriorly by the thoracic region spinal column, from the sides - by the right and left mediastitial pleura. Currently, the mediastinum is conditionally divided into the following:
| Posterior mediastinum | superior mediastinum | inferior mediastinum |
| Esophagus, thoracic descending aorta, unpaired and semi-unpaired veins, corresponding sections of the left and right sympathetic trunks, splanchnic nerves, vagus nerves, esophagus, thoracic lymphatic vessels | thymus, brachiocephalic veins, top part superior vena cava, aortic arch and vessels extending from it, trachea, upper esophagus and corresponding sections of the thoracic (lymphatic) duct, right and left sympathetic trunks, vagus and phrenic nerves | pericardium with the heart located in it and intracardiac divisions of large blood vessels, main bronchi, pulmonary arteries and veins, phrenic nerves with accompanying phrenic-pericardial vessels, lower tracheobronchial and lateral pericardial lymph nodes |
| Between the organs of the mediastinum is adipose connective tissue |