Breathing is the process of gas exchange between the body and the environment. Human life is closely related to biological oxidation reactions and is accompanied by the absorption of oxygen. To maintain oxidative processes, a continuous supply of oxygen is necessary, which is carried by the blood to all organs, tissues and cells, where most of it is associated with the final products of breakdown, and the body is freed from carbon dioxide. The essence of the breathing process is the consumption of oxygen and the release of carbon dioxide. (N.E. Kovalev, L.D. Shevchuk, O.I. Shchurenko. Biology for preparatory departments of medical institutes.)

Functions of the respiratory system.

Oxygen is found in the air around us.
It can penetrate the skin, but only in small quantities, completely insufficient to support life. There is a legend about Italian children who were painted gold to participate in a religious procession; the story goes on to say that they all died of suffocation because “the skin could not breathe.” Based on scientific evidence, death from suffocation is completely excluded here, since the absorption of oxygen through the skin is barely measurable, and the release of carbon dioxide is less than 1% of its release through the lungs. The respiratory system supplies oxygen to the body and removes carbon dioxide. Transport of gases and other substances necessary for the body is carried out using the circulatory system. The function of the respiratory system is simply to supply the blood with sufficient oxygen and remove carbon dioxide from it. The chemical reduction of molecular oxygen to form water serves as the main source of energy for mammals. Without it, life cannot last more than a few seconds. The reduction of oxygen is accompanied by the formation of CO 2 . The oxygen in CO 2 does not come directly from molecular oxygen. The use of O 2 and the formation of CO 2 are interconnected by intermediate metabolic reactions; theoretically, each of them lasts for some time. The exchange of O 2 and CO 2 between the body and the environment is called respiration. In higher animals, the process of respiration is carried out through a series of sequential processes. 1. Exchange of gases between the environment and the lungs, which is usually referred to as “pulmonary ventilation.” 2. Exchange of gases between the alveoli of the lungs and the blood (pulmonary respiration). 3. Exchange of gases between blood and tissues. Finally, gases move within the tissue to sites of consumption (for O 2) and from sites of production (for CO 2) (cellular respiration). The loss of any of these four processes leads to breathing problems and poses a danger to human life.

Anatomy.

The human respiratory system consists of tissues and organs that provide pulmonary ventilation and pulmonary respiration. The airways include: nose, nasal cavity, nasopharynx, larynx, trachea, bronchi and bronchioles. The lungs consist of bronchioles and alveolar sacs, as well as arteries, capillaries and veins of the pulmonary circulation. Elements of the musculoskeletal system associated with breathing include the ribs, intercostal muscles, diaphragm, and accessory respiratory muscles.

Airways.

The nose and nasal cavity serve as conduits for air, where it is heated, humidified, and filtered. The nasal cavity also contains olfactory receptors.
The outer part of the nose is formed by a triangular osteochondral frame, which is covered with skin; two oval openings on the lower surface - the nostrils - each open into the wedge-shaped cavity of the nose. These cavities are separated by a partition. Three light spongy whorls (turbinates) protrude from the side walls of the nostrils, partially dividing the cavities into four open passages (nasal passages). The nasal cavity is lined with a richly vascularized mucous membrane. Numerous hard hairs, as well as epithelial and goblet cells equipped with cilia, serve to clean the inhaled air from particulate matter. In the upper part of the cavity lie the olfactory cells.

The larynx lies between the trachea and the root of the tongue. The laryngeal cavity is divided by two folds of mucous membrane that do not completely converge along the midline. The space between these folds - the glottis - is protected by a plate of fibrocartilage - the epiglottis. Along the edges of the glottis in the mucous membrane lie fibrous elastic ligaments, which are called the lower, or true, vocal folds (ligaments). Above them are the false vocal folds, which protect the true vocal folds and keep them moist; they also help to hold your breath, and when swallowing, they prevent food from entering the larynx. Specialized muscles tighten and relax the true and false vocal folds. These muscles play an important role in phonation and also prevent any particles from entering the respiratory tract.

The trachea begins at the lower end of the larynx and descends into the chest cavity, where it divides into the right and left bronchi; its wall is formed by connective tissue and cartilage. In most mammals, cartilage forms incomplete rings. The parts adjacent to the esophagus are replaced by a fibrous ligament. The right bronchus is usually shorter and wider than the left. Having entered the lungs, the main bronchi gradually divide into smaller and smaller tubes (bronchioles), the smallest of which, the terminal bronchioles, are the last element of the airways. From the larynx to the terminal bronchioles, the tubes are lined with ciliated epithelium.

Lungs

In general, the lungs have the appearance of spongy, thick cone-shaped formations lying on both halves of the chest cavity. The smallest structural element of the lung, the lobule, consists of a terminal bronchiole leading to the pulmonary bronchiole and alveolar sac. The walls of the pulmonary bronchiole and alveolar sac form depressions called alveoli. This structure of the lungs increases their respiratory surface, which is 50-100 times greater than the surface of the body. The relative size of the surface area through which gas exchange occurs in the lungs is greater in animals with high activity and mobility. The walls of the alveoli consist of a single layer of epithelial cells and are surrounded by pulmonary capillaries. The inner surface of the alveoli is covered with a surfactant. The surfactant is believed to be a secretion product of granule cells. An individual alveolus, in close contact with neighboring structures, has the shape of an irregular polyhedron and approximate dimensions of up to 250 µm. It is generally accepted that the total surface area of ​​the alveoli through which gas exchange occurs depends exponentially on body weight. With age, there is a decrease in the surface area of ​​the alveoli.

Pleura

Each lung is surrounded by a sac called pleura. The outer (parietal) layer of the pleura is adjacent to the inner surface of the chest wall and the diaphragm, the inner (visceral) layer covers the lung. The gap between the layers is called the pleural cavity. When the chest moves, the inner leaf usually slides easily over the outer one. The pressure in the pleural cavity is always less than atmospheric (negative). Under resting conditions, intrapleural pressure in humans is on average 4.5 torr below atmospheric pressure (-4.5 torr). The interpleural space between the lungs is called the mediastinum; it contains the trachea, the thymus gland and the heart with large vessels, lymph nodes and the esophagus.

Blood vessels of the lungs

The pulmonary artery carries blood from the right ventricle of the heart, it divides into right and left branches, which go to the lungs. These arteries branch following the bronchi, supply the large structures of the lung and form capillaries that weave around the walls of the alveoli.

The air in the alveolus is separated from the blood in the capillary by the alveolar wall, the capillary wall, and in some cases an intermediate layer between them. From the capillaries, blood flows into small veins, which eventually join to form the pulmonary veins, which deliver blood to the left atrium.
The bronchial arteries of the great circle also bring blood to the lungs, namely, they supply the bronchi and bronchioles, lymph nodes, walls of blood vessels and the pleura. Most of this blood flows into the bronchial veins, and from there into the azygos (right) and semi-unpaired (left). A very small amount of arterial bronchial blood enters the pulmonary veins.

Respiratory muscles

Respiratory muscles are those muscles whose contractions change the volume of the chest. Muscles extending from the head, neck, arms and some of the upper thoracic and lower cervical vertebrae, as well as the external intercostal muscles connecting rib to rib, elevate the ribs and increase the volume of the chest. The diaphragm is a muscle-tendon plate attached to the vertebrae, ribs and sternum, separating the chest cavity from the abdominal cavity. This is the main muscle involved in normal inhalation. With increased inhalation, additional muscle groups contract. With increased exhalation, the muscles attached between the ribs (internal intercostal muscles), to the ribs and lower thoracic and upper lumbar vertebrae, as well as the abdominal muscles, act; they lower the ribs and press the abdominal organs against the relaxed diaphragm, thus reducing the capacity of the chest.

Pulmonary ventilation

As long as the intrapleural pressure remains below atmospheric pressure, the size of the lungs closely follows the size of the chest cavity. Lung movements occur as a result of contraction of the respiratory muscles in combination with the movement of parts of the chest wall and diaphragm.

Breathing movements

Relaxation of all muscles associated with breathing gives the chest a position of passive exhalation. Appropriate muscle activity can transform this position into inhalation or increase exhalation.
Inhalation is created by the expansion of the thoracic cavity and is always an active process. Due to their articulation with the vertebrae, the ribs move upward and outward, increasing the distance from the spine to the sternum, as well as the lateral dimensions of the thoracic cavity (costal or thoracic breathing). Contraction of the diaphragm changes its shape from dome-shaped to flatter, which increases the size of the chest cavity in the longitudinal direction (diaphragmatic or abdominal type of breathing). Typically, diaphragmatic breathing plays the main role in inhalation. Since humans are bipedal creatures, with every movement of the ribs and sternum, the center of gravity of the body changes and it becomes necessary to adapt different muscles to this.
During quiet breathing, a person usually has enough elastic properties and the weight of the displaced tissues to return them to the position preceding inspiration. Thus, exhalation at rest occurs passively due to a gradual decrease in the activity of the muscles that create the conditions for inhalation. Active expiration may occur due to contraction of the internal intercostal muscles in addition to other muscle groups that lower the ribs, reduce the transverse dimensions of the thoracic cavity and the distance between the sternum and the spine. Active exhalation can also occur due to contraction of the abdominal muscles, which presses the viscera against the relaxed diaphragm and reduces the longitudinal size of the thoracic cavity.
Expansion of the lung reduces (temporarily) the total intrapulmonary (alveolar) pressure. It is equal to atmospheric when the air does not move and the glottis is open. It is below atmospheric until the lungs are full when you inhale, and above atmospheric when you exhale. Intrapleural pressure also changes during the respiratory movement; but it is always below atmospheric (i.e., always negative).

Changes in lung volume

In humans, the lungs occupy about 6% of the body's volume, regardless of its weight. The volume of the lung does not change equally when inhaling. There are three main reasons for this: firstly, the chest cavity increases unevenly in all directions, and secondly, not all parts of the lung are equally extensible. Thirdly, the existence of a gravitational effect is assumed, which contributes to the downward displacement of the lung.
The volume of air inhaled during normal (non-forced) inhalation and exhaled during normal (non-forced) exhalation is called respiratory air. The volume of maximum exhalation after the previous maximum inhalation is called vital capacity. It is not equal to the entire volume of air in the lung (total lung volume) because the lungs do not collapse completely. The volume of air that remains in the rested lungs is called residual air. There is additional volume that can be inhaled at maximum effort after a normal inhalation. And the air that is exhaled with maximum effort after normal exhalation is the reserve volume of exhalation. Functional residual capacity consists of expiratory reserve volume and residual volume. This is the air in the lungs in which normal breathing air is diluted. As a result, the composition of the gas in the lungs usually does not change dramatically after one breathing movement.
Minute volume V is the air inhaled in one minute. It can be calculated by multiplying the average tidal volume (Vt) by the number of breaths per minute (f), or V=fVt. Part of V t, for example, the air in the trachea and bronchi to the terminal bronchioles and in some alveoli, does not participate in gas exchange, since it does not come into contact with the active pulmonary blood flow - this is the so-called “dead” space (V d). The part of Vt that participates in gas exchange with pulmonary blood is called alveolar volume (VA). From a physiological point of view, alveolar ventilation (VA) is the most essential part of external respiration V A = f (V t -V d), since it is the volume of air inhaled per minute that exchanges gases with the blood of the pulmonary capillaries.

Pulmonary respiration

Gas is a state of matter in which it is uniformly distributed over a limited volume. In the gas phase, the interaction of molecules with each other is insignificant. When they collide with the walls of a closed space, their movement creates a certain force; this force applied per unit area is called gas pressure and is expressed in millimeters of mercury.

Hygiene recommendations in relation to the respiratory organs, they include warming the air, purifying it from dust and pathogens. This is facilitated by nasal breathing. On the surface of the mucous membrane of the nose and nasopharynx there are many folds that ensure that air passes through, warming it, which protects a person from colds during the cold season. Thanks to nasal breathing, dry air is moistened, settled dust is removed by the ciliated epithelium, and tooth enamel is protected from damage that would occur when inhaling cold air through the mouth. Through the respiratory organs, pathogens of influenza, tuberculosis, diphtheria, tonsillitis, etc. can enter the body along with air. Most of them, like dust particles, stick to the mucous membrane of the airways and are removed from them by the ciliary epithelium, and microbes are neutralized by mucus. But some microorganisms settle in the respiratory tract and can cause various diseases.
Correct breathing is possible with normal development of the chest, which is achieved by systematic physical exercise in the open air, correct posture while sitting at a table, straight posture when walking and standing. In poorly ventilated areas, the air contains from 0.07 to 0.1% CO 2 , which is very harmful.
Smoking causes great harm to health. It causes constant poisoning of the body and irritation of the mucous membranes of the respiratory tract. The dangers of smoking are also evidenced by the fact that smokers are much more likely to get lung cancer than non-smokers. Tobacco smoke is harmful not only to smokers themselves, but also to those who remain in an atmosphere of tobacco smoke - in a residential area or at work.
The fight against air pollution in cities includes a system of treatment plants at industrial enterprises and extensive landscaping. Plants, releasing oxygen into the atmosphere and evaporating large quantities of water, refresh and cool the air. Tree leaves trap dust, making the air cleaner and clearer. Proper breathing and systematic hardening of the body are important for health, for which you need to often be in the fresh air, take walks, preferably outside the city, into the forest.

Line UMK Ponomareva (5-9)

Biology

The structure of the human respiratory system

Since life emerged from the sea onto land, the respiratory system, which ensures gas exchange with the external environment, has become an important part of the human body. Although all body systems are important, it is wrong to assume that one is more important and another less important. After all, the human body is a finely regulated and quickly reacting system that strives to ensure the constancy of the internal environment of the body, or homeostasis.

The respiratory system is a set of organs that ensure the supply of oxygen from the surrounding air to the respiratory tract and carry out gas exchange, i.e. bringing oxygen into the bloodstream and removing carbon dioxide from the bloodstream back into the atmosphere. However, the respiratory system is not only about providing the body with oxygen - it is also about human speech, and the capture of various odors, and heat exchange.

Organs of the human respiratory system conditionally divided into respiratory tract, or conductors, through which the air mixture enters the lungs, and lung tissue, or alveoli.

The respiratory tract is conventionally divided into upper and lower according to the level of attachment of the esophagus. The top ones include:

• nose and paranasal sinuses
• oropharynx
• larynx

The lower respiratory tract includes:

• trachea
• main bronchi
• bronchi of the following orders
• terminal bronchioles.

The nasal cavity is the first boundary when air enters the body. Numerous hairs located on the nasal mucosa stand in the way of dust particles and purify the passing air. The nasal turbinates are represented by a well-supplied mucous membrane and, passing through the convoluted nasal turbinates, the air is not only purified, but also warmed.

The nose is also the organ through which we enjoy the aroma of fresh baked goods, or can accurately determine the location of a public toilet. And all because sensitive olfactory receptors are located on the mucous membrane of the upper nasal concha. Their quantity and sensitivity are genetically programmed, thanks to which perfumers create memorable perfume aromas.

Passing through the oropharynx, air enters larynx. How is it that food and air pass through the same parts of the body and do not mix? When swallowing, the epiglottis covers the airway and food enters the esophagus. If the epiglottis is damaged, a person may choke. Inhalation of food requires immediate attention and can even lead to death.

The larynx consists of cartilage and ligaments. The cartilage of the larynx is visible to the naked eye. The largest of the cartilages of the larynx is the thyroid cartilage. Its structure depends on sex hormones and in men it moves forward strongly, forming adam's apple, or Adam's apple. It is the cartilage of the larynx that serves as a guide for doctors when performing tracheotomy or conicotomy - operations that are performed when a foreign body or tumor blocks the lumen of the respiratory tract, and a person cannot breathe in the usual way.

Next, the vocal cords get in the way of the air. It is by passing through the glottis and causing the tense vocal cords to tremble that a person has access to not only the function of speech, but also singing. Some unique singers can make the chords tremble at a frequency of 1000 decibels and explode crystal glasses with the power of their voices
(in Russia, Svetlana Feodulova, a participant in the show “Voice-2”, has the widest voice range of five octaves).

The trachea has a structure cartilaginous half rings. The anterior cartilaginous part ensures the unhindered passage of air due to the fact that the trachea does not collapse. The esophagus is adjacent to the trachea, and the soft part of the trachea does not delay the passage of food through the esophagus.

Then the air travels through the bronchi and bronchioles, lined with ciliated epithelium, to the final section of the lungs - alveoli. Lung tissue, or alveoli - terminal, or terminal parts of the tracheobronchial tree, similar to blindly ending bags.

Many alveoli form the lungs. The lungs are a paired organ. Nature took care of her careless children, and created some important organs - lungs and kidneys - in duplicate. A person can live with only one lung. The lungs are located under the reliable protection of a frame made of strong ribs, sternum and spine.

The textbook complies with the Federal State Educational Standard for Basic General Education, is recommended by the Ministry of Education and Science of the Russian Federation and is included in the Federal List of Textbooks. The textbook is addressed to 9th grade students and is part of the educational and methodological complex “Living Organism”, built on a linear principle.

Functions of the respiratory system

Interestingly, the lungs are devoid of muscle tissue and cannot breathe on their own. Breathing movements are ensured by the work of the diaphragm and intercostal muscles.

A person performs breathing movements thanks to the complex interaction of various groups of intercostal muscles, abdominal muscles during deep breathing, and the most powerful muscle involved in breathing is diaphragm.

The experiment with the Donders model, described on page 177 of the textbook, will help you visualize the work of the respiratory muscles.

The lungs and chest are lined pleura. The pleura, which lines the lungs, is called pulmonary, or visceral. And the one that covers the ribs - parietal, or parietal. The structure of the respiratory system provides the necessary gas exchange.

When inhaling, the muscles stretch the lung tissue, like a skilled musician playing a button accordion, and the air mixture of atmospheric air, consisting of 21% oxygen, 79% nitrogen and 0.03% carbon dioxide, enters through the respiratory tract to the final section, where the alveoli, entwined with a fine network of capillaries, are ready to receive oxygen and release waste carbon dioxide from the human body. The composition of exhaled air has a significantly higher content of carbon dioxide – 4%.

To imagine the scale of gas exchange, just think that the area of ​​all the alveoli in the human body is approximately equal to a volleyball court.

To prevent the alveoli from sticking together, their surface is lined surfactant- a special lubricant containing lipid complexes.

The terminal sections of the lungs are densely woven with capillaries and the wall of the blood vessels is in close contact with the wall of the alveoli, which allows the oxygen contained in the alveoli to differ in concentrations, without the participation of carriers, by passive diffusion into the blood.

If we remember the basics of chemistry, and specifically the topic solubility of gases in liquids, the especially meticulous may say: “What nonsense, because the solubility of gases decreases with increasing temperature, but here you are saying that oxygen dissolves perfectly in a warm, almost hot - approximately 38-39 ° C, salty liquid.”
And they are right, but they forget that the red blood cell contains the invader hemoglobin, one molecule of which can attach 8 oxygen atoms and transport them to the tissues!

In the capillaries, oxygen binds to the carrier protein on red blood cells and oxygenated arterial blood returns to the heart through the pulmonary veins.
Oxygen participates in oxidation processes, and the cell as a result receives the energy necessary for life.

Breathing and gas exchange are the most important functions of the respiratory system, but they are far from the only ones. The respiratory system maintains thermal balance by evaporating water during breathing. An attentive observer has noticed that in hot weather a person begins to breathe more often. In humans, however, this mechanism does not work as efficiently as in some animals, such as dogs.

Hormonal function through the synthesis of important neurotransmitters(serotonin, dopamine, adrenaline) are provided by pulmonary neuroendocrine cells ( PNE-pulmonary neuroendocrine cells). Arachidonic acid and peptides are also synthesized in the lungs.

Biology. 9th grade. Textbook

A biology textbook for grade 9 will help you get an idea of ​​the structure of living matter, its most general laws, the diversity of life and the history of its development on Earth. When working, you will need your life experience, as well as the knowledge of biology acquired in grades 5–8.

Regulation

It would seem that there is nothing complicated here. The oxygen content in the blood has decreased, and here it is - a command to inhale. However, in reality the mechanism is much more complicated. Scientists have not yet figured out the mechanism by which a person breathes. Researchers only put forward hypotheses, and only some of them are proven by complex experiments. It is only certain that there is no true pacemaker in the respiratory center, similar to the pacemaker in the heart.

The brainstem contains the respiratory center, which consists of several separate groups of neurons. There are three main groups of neurons:

• dorsal group- the main source of impulses that ensure a constant breathing rhythm;
• ventral group- controls the level of ventilation of the lungs and can stimulate inhalation or exhalation depending on the moment of excitation. It is this group of neurons that controls the abdominal and abdominal muscles for deep breathing;
• pneumotaxic center - thanks to its work, there is a smooth change from exhalation to inhalation.

To fully provide the body with oxygen, the nervous system regulates the rate of ventilation of the lungs by changing the rhythm and depth of breathing. Thanks to well-functioning regulation, even active physical activity has virtually no effect on the concentration of oxygen and carbon dioxide in arterial blood.

The following are involved in the regulation of breathing:

• carotid sinus chemoreceptors, sensitive to the content of O 2 and CO 2 gases in the blood. The receptors are located in the internal carotid artery at the level of the upper edge of the thyroid cartilage;
• lung stretch receptors located in the smooth muscles of the bronchi and bronchioles;
• inspiratory neurons, located in the medulla oblongata and pons (divided into early and late).

Signals from various groups of receptors located in the respiratory tract are transmitted to the respiratory center of the medulla oblongata, where, depending on the intensity and duration, an impulse to the respiratory movement is formed.

Physiologists have suggested that individual neurons are combined into neural networks to regulate the sequence of changes in inhalation-exhalation phases, registering their flow of information by individual types of neurons, and changing the rhythm and depth of breathing in accordance with this flow.

The respiratory center located in the medulla oblongata monitors the level of blood gas tension and regulates ventilation of the lungs using respiratory movements so that the concentration of oxygen and carbon dioxide is optimal. Regulation is carried out using a feedback mechanism.

You can read about the regulation of breathing using the protective mechanisms of coughing and sneezing on page 178 of the textbook.

What can be called the main indicator of human vitality? Of course, we are talking about breathing. A person can go without food and water for some time. Without air, life is not possible at all.

General information

What is breathing? It is the link between the environment and people. If the supply of air is difficult for some reason, then the human heart and respiratory organs begin to function in an enhanced mode. This occurs due to the need to provide sufficient oxygen. Organs are able to adapt to changing environmental conditions.

Scientists were able to establish that the air entering the human respiratory system forms two streams (conditionally). One of them penetrates the left side of the nose. shows that the second one is coming from the right side. Experts have also proven that the arteries of the brain are divided into two streams of air. Thus, the breathing process must be correct. This is very important for maintaining the normal functioning of people. Let's consider the structure of the human respiratory organs.

Important Features

When we talk about breathing, we are talking about a set of processes that are aimed at ensuring a continuous supply of oxygen to all tissues and organs. In this case, substances that are formed during the exchange of carbon dioxide are removed from the body. Breathing is a very complex process. It goes through several stages. The stages of entry and exit of air into the body are as follows:

1. We are talking about gas exchange between atmospheric air and the alveoli. This stage is considered
2. Exchange of gases carried out in the lungs. It occurs between the blood and alveolar air.
3. Two processes: the delivery of oxygen from the lungs to the tissues, as well as the transport of carbon dioxide from the latter to the former. That is, we are talking about the movement of gases using the bloodstream.
4. The next stage of gas exchange. It involves tissue cells and capillary blood.
5. Finally, internal breathing. This refers to what occurs in the mitochondria of cells.

Main tasks

The human respiratory organs remove carbon dioxide from the blood. Their task also includes saturating it with oxygen. If we list the functions of the respiratory organs, then this is the most important.

Additional purpose

There are other functions of the human respiratory organs, among them the following can be distinguished:

1. Taking part in thermoregulation processes. The fact is that the temperature of the inhaled air affects a similar parameter of the human body. During exhalation, the body releases heat to the external environment. At the same time, it is cooled, if possible.
2. Taking part in excretory processes. During exhalation, water vapor is eliminated from the body along with air (except carbon dioxide). This also applies to some other substances. For example, ethyl alcohol during alcohol intoxication.
3. Taking part in immune reactions. Thanks to this function of the human respiratory organs, it becomes possible to neutralize some pathologically dangerous elements. These include, in particular, pathogenic viruses, bacteria and other microorganisms. Certain lung cells are endowed with this ability. In this regard, they can be classified as elements of the immune system.

Specific tasks

There are very narrowly focused functions of the respiratory organs. In particular, specific tasks are performed by the bronchi, trachea, larynx, and nasopharynx. Among these narrowly focused functions are the following:

1. Cooling and warming of incoming air. This task is performed according to the ambient temperature.
2. Humidification of the air (inhaled), which prevents the lungs from drying out.
3. Purification of incoming air. In particular, this applies to foreign particles. For example, to dust entering with the air.

The structure of the human respiratory organs

All elements are connected by special channels. Air enters and exits through them. This system also includes the lungs, the organs where gas exchange occurs. The structure of the entire complex and the principle of its operation are quite complex. Let's look at the human respiratory system (pictures below) in more detail.

Information about the nasal cavity

The respiratory tract begins with it. The nasal cavity is separated from the oral cavity. The front is the hard palate, and the back is the soft palate. The nasal cavity has a cartilaginous and bone skeleton. It is divided into left and right parts thanks to a continuous partition. There are also three. Thanks to them, the cavity is divided into passages:

1. Lower.
2. Average.
3. Upper.

Exhaled and inhaled air passes through them.

Features of the mucosa

It has a number of devices that are designed to process inhaled air. First of all, it is covered by ciliated epithelium. Its cilia form a continuous carpet. Due to the fact that the eyelashes flicker, dust is quite easily removed from the nasal cavity. The hairs that are located at the outer edge of the holes also help retain foreign elements. contains special glands. Their secretion envelops dust and helps eliminate it. In addition, air humidification occurs.

The mucus that is found in the nasal cavity has bactericidal properties. It contains lysozyme. This substance helps reduce the ability of bacteria to reproduce. It also kills them. The mucous membrane contains many venous vessels. Under different conditions they can swell. If they are damaged, nosebleeds begin. The purpose of these formations is to heat the air stream passing through the nose. Leukocytes leave the blood vessels and end up on the surface of the mucosa. They also perform protective functions. During the process of phagocytosis, leukocytes die. Thus, the mucus that comes out of the nose contains many dead “defenders”. Next, the air passes into the nasopharynx, and from there to other organs of the respiratory system.

Larynx

It is located in the anterior laryngeal part of the pharynx. This is the level of the 4th-6th cervical vertebrae. The larynx is formed by cartilage. The latter are divided into paired (sphenoid, corniculate, arytenoid) and unpaired (cricoid, thyroid). In this case, the epiglottis is attached to the upper edge of the last cartilage. During swallowing, it closes the entrance to the larynx. Thus, it prevents food from entering it.

General information about the trachea

It is a continuation of the larynx. It is divided into two bronchi: left and right. The bifurcation is where the trachea branches. It is characterized by the following length: 9-12 centimeters. On average, the transverse diameter reaches eighteen millimeters.

The trachea may include up to twenty incomplete cartilaginous rings. They are connected by fibrous ligaments. Thanks to cartilaginous half-rings, the airways become elastic. In addition, they are made to flow down, therefore, they are easily passable for air.

The membranous posterior wall of the trachea is flattened. It contains smooth muscle tissue (bundles that run longitudinally and transversely). This ensures active movement of the trachea when coughing, breathing, and so on. As for the mucous membrane, it is covered by ciliated epithelium. In this case, the exception is part of the epiglottis and vocal cords. It also has mucous glands and lymphoid tissue.

Bronchi

This is a paired element. The two bronchi into which the trachea is divided enter the left and right lungs. There they branch tree-like into smaller elements, which are included in the pulmonary lobules. Thus, bronchioles are formed. We are talking about even smaller respiratory branches. The diameter of the respiratory bronchioles can be 0.5 mm. They, in turn, form the alveolar ducts. The latter end with corresponding bags.

What are alveoli? These are protrusions that look like bubbles, which are located on the walls of the corresponding sacs and passages. Their diameter reaches 0.3 mm, and the number can reach up to 400 million. This makes it possible to create a large breathing surface. This factor significantly affects lung volume. The latter can be increased.

The most important human respiratory organs

They are considered lungs. Serious illnesses associated with them can be life-threatening. The lungs (photos presented in the article) are located in the chest cavity, which is hermetically sealed. Its posterior wall is formed by the corresponding part of the spine and ribs, which are movably attached. Between them are the internal and external muscles.

The chest cavity is separated from the abdominal cavity from below. The abdominal obstruction, or diaphragm, is involved in this. The anatomy of the lungs is not simple. A person has two of them. The right lung includes three lobes. At the same time, the left consists of two. The apex of the lungs is their narrowed upper part, and the expanded lower part is considered the base. The gates are different. They are represented by depressions on the inner surface of the lungs. Blood nerves as well as lymphatic vessels pass through them. The root is represented by a combination of the above formations.

The lungs (the photo illustrates their location), or rather their tissue, consist of small structures. They are called lobules. We are talking about small areas that have a pyramidal shape. The bronchi, which enter the corresponding lobule, are divided into respiratory bronchioles. The alveolar duct is present at the end of each of them. This entire system represents the functional unit of the lungs. It is called the acini.

The lungs are covered with pleura. This is a shell consisting of two elements. We are talking about the outer (parietal) and inner (visceral) lobes (a diagram of the lungs is attached below). The latter covers them and at the same time is the outer shell. It makes a transition to the outer layer of the pleura along the root and represents the inner lining of the walls of the chest cavity. This leads to the formation of a geometrically closed, minute capillary space. We are talking about the pleural cavity. It contains a small amount of the corresponding liquid. She moistens the pleura. This makes it easier for them to slide together. Changes in air in the lungs occur for many reasons. One of the main ones is the change in the size of the pleural and chest cavities. This is the anatomy of the lungs.

Features of the air inlet and outlet mechanism

As mentioned earlier, an exchange occurs between the gas that is in the alveoli and the atmospheric gas. This is due to the rhythmic alternation of inhalations and exhalations. The lungs do not have muscle tissue. For this reason, their intensive reduction is impossible. In this case, the most active role is given to the respiratory muscles. When they are paralyzed, it is not possible to breathe. In this case, the respiratory organs are not affected.

Inspiration is the act of breathing in. We are talking about an active process during which the chest enlarges. Expiration is the act of exhalation. This process is passive. It occurs because the chest cavity becomes smaller.

The respiratory cycle is represented by the phases of inhalation and subsequent exhalation. The diaphragm and external oblique muscles take part in the process of air entry. As they contract, the ribs begin to rise. At the same time, the chest cavity enlarges. The diaphragm contracts. At the same time, it takes a flatter position.

As for the incompressible organs, during the process under consideration they are pushed to the sides and down. During a quiet inhalation, the dome of the diaphragm lowers by about one and a half centimeters. Thus, the vertical size of the thoracic cavity increases. In the case of very deep breathing, auxiliary muscles take part in the act of inhalation, among which the following stand out:

1. Rhomboids (which elevate the scapula).
2. Trapezoidal.
3. Small and large pectorals.
4. Anterior serratus.

The wall of the chest cavity and the lungs are covered by a serous membrane. The pleural cavity is represented by a narrow gap between the layers. It contains serous fluid. The lungs are always stretched. This is due to the fact that the pressure in the pleural cavity is negative. We are talking about elastic traction. The fact is that lung volume constantly tends to decrease. At the end of a quiet exhalation, almost every respiratory muscle relaxes. In this case, the pressure in the pleural cavity is below atmospheric. For different people, the main role in the act of inhalation is played by the diaphragm or intercostal muscles. In accordance with this, we can talk about different types of breathing:

1. Reburn.
2. Diaphragmatic.
3. Abdomen.
4. Grudny.

It is now known that the latter type of breathing predominates in women. In men, most cases are abdominal. During quiet breathing, exhalation occurs due to elastic energy. It accumulates during the previous inhalation. As the muscles relax, the ribs can passively return to their original position. If the contractions of the diaphragm decrease, it will return to its previous dome-shaped position. This is due to the fact that the abdominal organs act on it. Thus, the pressure in it decreases.

All of the above processes lead to compression of the lungs. Air comes out of them (passively). Forced exhalation is an active process. The internal intercostal muscles take part in it. Moreover, their fibers go in the opposite direction when compared with external ones. They contract and the ribs move down. The chest cavity also shrinks.

Functions of the respiratory system

STRUCTURE OF THE RESPIRATORY SYSTEM

Test questions

1. What organs are called parenchymal?

2. What membranes are found 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. Name the timing of the eruption of milk and permanent teeth. Write the complete formula of primary 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 minor salivary glands. In what places in the walls of the oral cavity do the ducts of the major salivary glands open?

9. Name the muscles of the soft palate, their places of origin and insertion.

10. In what places does the esophagus have narrowings, what causes them?

11. At what level of vertebrae are the inlet and outlet openings of the stomach located? Name the ligaments (peritoneal) of the stomach.

12. Describe the structure and functions of the stomach.

13. How long and thick is the small intestine?

14. What anatomical formations are visible on the surface of the mucous membrane of the small intestine along its entire length?

15. How does the large intestine differ in structure from the small intestine?

16. Where on the anterior abdominal wall do the lines of projections of the upper and lower borders of the liver converge? Describe the structure of the liver and gall bladder.

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 body’s heat 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. 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 respiratory) consists of the respiratory tract and paired respiratory organs - the lungs (Fig. 4.1; Table 4.1). The respiratory tract, according to its position in the body, is divided into upper and lower sections. 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 – tongue; 5 – oral part of the pharynx; 6 – epiglottis; 7 – laryngeal part of the pharynx; 8 – larynx; 9 – esophagus; 10 – trachea; 11 – apex 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 maintained due to the presence of a bone or cartilaginous skeleton in their walls. This morphological feature fully corresponds to the function of the respiratory tract - carrying air into the lungs and from the lungs out. The inner surface of the respiratory tract is covered with a mucous membrane, which is lined with ciliated epithelium and contains significant

Table 4.1. Main characteristics of the respiratory system

Oxygen transport	Oxygen delivery route	Structure	Functions
Upper respiratory tract	Nasal cavity	Initial section 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. The nasal passages contain olfactory receptors
Pharynx	Consists of the nasopharynx and the oropharynx, which passes into the larynx	Passing warmed 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 there are vocal cords that form the glottis	Conduction of air from the pharynx into the trachea. Protecting the respiratory tract from food ingress. The formation of sounds by vibration of the vocal cords, movement of the tongue, lips, jaw
Trachea	The breathing tube is about 12 cm long; there are cartilaginous half-rings 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 bronchioles.	Free air movement
Lungs	Lungs	The right lung consists of three lobes, the left - of two. Located in the thoracic cavity of the body. Covered with pleura. They lie in the pleural sacs. Have a spongy structure	Respiratory organs. Respiratory movements are 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 respiratory surface area, carry out gas exchange between the blood and the lungs

the number of glands that secrete mucus. Thanks to this, it performs a protective function. Passing through the respiratory tract, the air is cleaned, warmed and moistened. In the process of evolution, along the path of the air stream, the larynx was formed - a complex organ that performs the function of voice production. 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 through the diffusion of gases (oxygen and carbon dioxide) through the walls of the pulmonary alveoli and the blood capillaries adjacent to them.

Nasal cavity (cavitalis nasi) includes the external nose and the nasal cavity itself (Fig. 4.2).

Rice. 4.2. Nasal cavity. Sagittal section.

External nose includes the root, dorsum, 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 bridge of the nose. The sides of the external nose meet along the midline and form the dorsum of the nose, and the lower parts of the sides represent the wings of the nose, which limit the nostrils with their lower edges , serving to pass air into and out of the nasal cavity. Along the midline, the nostrils are separated from each other by a movable (membranous) part of the nasal septum. The external nose has a bony and cartilaginous skeleton formed by the nasal bones, the frontal processes of the upper jaws and several hyaline cartilages.

The nasal cavity itself 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 there is a vestibule of the nose, which is limited from above by a small elevation - the threshold of the nasal cavity, formed by the upper edge of the large cartilage of the nasal wing. The vestibule is covered from the inside by the skin of the external nose, which extends here through the nostrils. The skin of the vestibule contains sebaceous, sweat glands and coarse 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 there is a sphenoethmoidal recess. Between the nasal septum and the medial surfaces of the turbinates there 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. The lateral wall of the middle nasal meatus forms a rounded protrusion towards the nasal concha - a large ethmoidal vesicle. In front and below the large ethmoidal vesicle there is a deep cleft semilunaris , through which the frontal sinus communicates with the middle meatus. The middle and anterior cells (sinuses) of the ethmoid bone, the frontal sinus, and the maxillary sinus open into the middle meatus. The inferior opening of the nasolacrimal duct leads into the inferior nasal passage.

Nasal mucosa continues into the mucous membrane of the paranasal sinuses, lacrimal sac, nasal 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 superior nasal conchas and part of the middle ones, as well as the corresponding upper part of the nasal septum, containing olfactory neurosensory cells) and respiratory regions (the rest of the mucous membrane) are distinguished nose). The mucous membrane of the respiratory region is covered with ciliated epithelium and contains mucous and serous glands. In the area of ​​the inferior concha, the mucous membrane and submucosa are rich in venous vessels, which form cavernous venous plexus of conchae, the presence of which helps to warm the inhaled air.

Larynx(larynx) performs the functions of breathing, voice production and protecting the lower respiratory tract from foreign particles entering them. It occupies a mid-position in the anterior region of the neck, forms a barely noticeable (in women) or strongly protruding (in men) elevation - the 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 gut. The crossroads of the digestive and respiratory tracts occurs in the pharynx.

Laryngeal cavity can be roughly divided into three sections: the vestibule of the larynx, the interventricular section and the subglottic cavity (Fig. 4.4).

Vestibule of the larynx 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 the epiglottis covered with mucous membrane, and the posterior wall (height 1.0–1.5 cm) is formed by the arytenoid cartilages.

Rice. 4.3. Larynx and thyroid gland.

Rice. 4.4. The laryngeal cavity in a sagittal section.

Interventricular department- the narrowest, extends 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 laryngeal ventricle. . The right and left vocal folds define the glottis, which is the narrowest part of the laryngeal cavity. The length of the glottis (antero-posterior size) in men reaches 20-24 mm, in women – 16-19 mm. The width of the glottis during quiet breathing is 5 mm, and during voice production it reaches 15 mm. With maximum expansion of the glottis (singing, screaming), the rings of the trachea are visible up to its division into the main bronchi.

Lower section laryngeal cavity, located under the glottis - subglottic cavity, gradually expands and continues into the tracheal cavity. The mucous membrane lining the laryngeal cavity is pink, covered with ciliated epithelium, and contains many serous-mucosal glands, especially in the area of ​​​​the folds of the vestibule and the ventricles of the larynx; The secretion of the glands moisturizes the vocal folds. In the area of ​​the vocal folds, the mucous membrane is covered with stratified squamous epithelium, tightly fuses with the submucosa and does not contain glands.

Laryngeal cartilages. The skeleton of the larynx is formed by paired (arytenoid, corniculate and sphenoid) 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 the anterior part of the cartilage there is a superior thyroid notch and a poorly defined inferior thyroid notch. The posterior edges of the plates of the thyroid cartilage form a longer superior 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 junction of the cricoid cartilage arch and 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 triangular pyramid. From the base of the arytenoid cartilage the vocal process protrudes forward, formed by elastic cartilage to which the vocal cord is attached. Laterally from the base of the arytenoid cartilage its muscular process extends for muscle attachment.

At the apex of the arytenoid cartilage, in the thickness of the posterior section of the aryepiglottic fold, lies corniculate cartilage. This paired elastic cartilage forms a cornuform tubercle protruding above the apex of the arytenoid cartilage.

Sphenoid cartilage – paired, elastic. The cartilage is located in the thickness of the aryepiglottic 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.

Connections of cartilage of the larynx. The cartilages of the larynx are connected to each other, as well as to the hyoid bone, using 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 (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. When bending forward, the distance between the angle of the thyroid cartilage and the arytenoid cartilages increases.

Cricoarytenoid joint– paired, formed by a concave articular surface on the base 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 the right and left arytenoid cartilages rotate inward (under the action of the corresponding muscles), the vocal processes, together with the vocal cords attached to them, come closer (the glottis narrows), and when they rotate outward, they move away and diverge to the sides (the glottis expands). Sliding is also possible in the cricoarytenoid joint, in which the arytenoid cartilages either move away from each other or move closer to each other. When the arytenoid cartilages slide and approach 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, using ligaments (continuous connections). The median thyrohyoid ligament is stretched between the hyoid bone and the upper edge of the thyroid cartilage. Along the edges, the lateral thyrohyoid ligaments can be distinguished. The anterior surface of the epiglottis is attached to the hyoid bone by the hypoglottic ligament, and to the thyroid cartilage by the thyroepiglottic 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 (thyroarytenoid, anterior and oblique arytenoid muscles, etc.) and muscles that tension (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 has the shape of a tube from 9 to 11 cm long, somewhat compressed in the direction from front to back. The trachea is located in the neck area - cervical part , and in the chest 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 there 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 are the right and left mediastinal pleura. The tracheal wall consists of mucous membrane, submucosa, fibrous-muscular-cartilaginous and connective tissue membranes. The basis of the trachea is 16–20 cartilaginous hyaline half-rings, occupying about two-thirds of the circumference of the trachea, with the open part facing backwards. Thanks to cartilaginous half-rings, the trachea has flexibility and elasticity. Adjacent tracheal cartilages are connected to each other 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, and serves (in direction) as a continuation of the trachea. Therefore, foreign bodies enter the right main bronchus more often than the left.

The length of the right bronchus (from the beginning to the 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 is the azygos vein before its flow into the superior vena cava. The wall of the main bronchi is similar in structure to the wall of the trachea. Their skeleton is made up of cartilaginous semirings (6–8 in the right bronchus, 9–12 in the left); at the rear, the main bronchi have a membranous wall. The inside of the main bronchi is lined with mucous membrane, and the outside is covered with a connective tissue membrane (adventitia).

Lung (rilto). The right and left lungs are located in the chest cavity, in its right and left halves, each in its own pleural sac. The lungs, located in the pleural sacs, are separated from each other mediastinum , which includes 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 with its apex is turned to the left (Fig. 4.8).

Rice. 4.8. Lungs. Front view.

The lung has the shape of an irregular cone with one side flattened (facing the mediastinum). With the help of slits protruding deeply into it, it is divided into lobes, of which the right one 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 hilum of the lung, the main bronchus divides into lobar bronchi, of which there are three in the right lung and two in the left, which are also each divided into two or three segmental bronchi. The segmental bronchus enters a segment, which is a section of the lung whose base faces the surface of the organ and its apex faces the root. The pulmonary segment consists of pulmonary lobules. In the center of the segment there is a segmental bronchus and a segmental artery, and on the border with the adjacent segment there is a segmental vein. The segments are separated from each other by connective tissue (little-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-groove of the subclavian artery; 3-depression of the azygos vein; 4-bronchopulmonary lymph nodes; 5th right main bronchus; 6th right pulmonary artery; 7-groove - azygos vein; 8-posterior edge of the lung; 9-pulmonary veins; 10-pi-shevod depression; 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-cardial depression; 17-oblique slit; 18-anterior edge of the lung; 19-upper lobe of the lung; 20-visceral pleura (cut off): 21-sulcus of the right and lechecephalic vein

Rice. 4.10. Left lung. Medial (inner) surface. 1-apex of the lung, 2-sulcus of the left subclavian artery, 2-sulcus of the left brachiocephalic vein; 4-left pulmonary artery, 5-main bronchus, 6-anterior edge of the left lung, 7-pulmonary veins (left), 8-upper lobe of the left lung, 9-cardiac depression, 10-cardiac notch of the left lung, 11- oblique fissure, 12-lingula of the left lung, 13-lower edge of the left lung, 14-diaphragmatic surface, 15-lower lobe of the left lung, 16-pulmonary ligament, 17-bronchopulmonary lymph nodes, 18-aortic groove, 19-visceral pleura (cut off), 20-oblique slot.

The bronchus, about 1 mm in diameter, still containing cartilage in its walls, enters a lobe of the lung called the lobular bronchus. Inside the pulmonary lobule, this bronchus is divided 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.

Alveolar ducts depart from each respiratory bronchiole, carrying alveoli and ending in the alveolar sacs. Bronchi of various orders, starting from the main bronchus, which serve to conduct air during breathing, make up the bronchial tree (Fig. 4.11). The respiratory bronchioles extending from the terminal bronchiole, as well as the alveolar ducts, alveolar sacs and alveoli of the lung form the alveolar tree (pulmonary acinus). The alveolar tree, in which gas exchange occurs between air and blood, is the 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 area of ​​the respiratory surface of all alveoli is about 80 m2.

Rice. 4.11. Branching of bronchi in the lung (diagram).

Pleura (pleura) – the serous membrane of the lung, divided into visceral (pulmonary) and parietal (parietal). Each lung is covered with pleura (pulmonary), which along the surface of the root passes into the parietal pleura, lining the walls of the chest cavity adjacent to the lung and delimiting the lung from the mediastinum. Visceral (pulmonary) pleura tightly fuses with the tissue of the organ and, covering it on all sides, enters the cracks between the lobes of the lung. Down from the root of the lung, the visceral pleura, descending from the anterior and posterior surfaces of the lung root, 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 down almost to the diaphragm. Parietal (parietal) pleura It is a continuous sheet that fuses with the inner surface of the chest wall and in each half of the chest cavity forms a closed sac containing the right or left lung, covered with visceral pleura. Based on the position of the parts of the parietal pleura, it is divided into the costal, mediastinal and diaphragmatic pleura.

RESPIRATION CYCLE consists of inhalation, exit and breathing pause. The duration of inhalation (0.9-4.7 s) and exhalation (1.2-6 s) depends on the reflex effects of the lung tissue. The frequency and rhythm of breathing is determined by the number of chest excursions per minute. At rest, an adult takes 16-18 breaths per minute.

Table 4.1. Content of oxygen and carbon dioxide in inhaled and exhaled air

Rice. 4.12. Exchange of gases between the blood and air of the alveoli: 1 – lumen of the alveoli; 2 – alveolar wall; 3 – wall of the blood capillary; 4 – capillary lumen; 5 – erythrocyte in the lumen of the capillary. The arrows show the path of oxygen and carbon dioxide through the aerohematic barrier (between blood and air).

Table 4.2. Respiratory volumes.

Indicator	Peculiarities
Tidal volume (TO)	The amount of air that a person inhales and exhales during quiet breathing (300-700 ml)
Inspiratory reserve volume (IRV)	The volume of air that can be inhaled additionally after a normal inhalation (1500-3000 ml)
Expiratory reserve volume (ERV)	The volume of air that can be exhaled additionally after a normal exhalation (1500-2000 ml)
Residual volume (VR)	The volume of air that remains in the lungs after the deepest exhalation (1000-1500 ml)
Vital capacity of the lungs (VC)	The deepest breathing a person is capable of: DO+ROvd+ROvyd (3000-4500ml)
Total lung capacity (TLC)	VEL + OO. The amount of air found in the lungs after maximum inspiration (4000-6000 ml)
Pulmonary ventilation or minute volume of respiration (MVR)	DO*number of breaths in 1 minute (6-8 l/min). Alveolar gas composition renewal indicator. Associated with overcoming the elastic resistance of the lungs and resistance to respiratory air flow (non-elastic resistance)

MEDIASTINUM (mediastinum) is a complex of organs located between the right and left pleural cavities. The mediastinum is bounded in front by the sternum, in the back by the thoracic spine, and on the sides by the right and left mediastinal pleura. Currently, the mediastinum is conventionally divided into the following:

Posterior mediastinum	Superior mediastinum	Inferior mediastinum
Esophagus, thoracic part of the descending aorta, azygos and semi-gypsy veins, corresponding sections of the left and right sympathetic trunks, splanchnic nerves, vagus nerves, esophagus, thoracic lymphatic vessels	Thymus, brachiocephalic veins, upper part of the superior vena cava, aortic arch and vessels extending from it, trachea, upper part of the esophagus and corresponding parts of the thoracic (lymphatic) duct, right and left sympathetic trunks, vagus and phrenic nerves	pericardium with the heart and intracardial sections of large blood vessels located in it, main bronchi, pulmonary arteries and veins, phrenic nerves with accompanying phrenic-pericardial vessels, lower tracheobronchial and lateral pericardial lymph nodes
Between the mediastinal organs there is adipose connective tissue

Respiration is a complex and continuous biological process, as a result of which the body consumes free electrons and oxygen from the external environment, and releases carbon dioxide and water saturated with hydrogen ions.

The human respiratory system is a set of organs that provide the function of human external respiration (gas exchange between inhaled atmospheric air and blood circulating in the pulmonary circulation).

Gas exchange takes place in the alveoli of the lungs, and is normally aimed at capturing oxygen from the inhaled air and releasing carbon dioxide formed in the body into the external environment.

An adult, being at rest, takes an average of 15-17 breaths per minute, and a newborn baby takes 1 breath per second.

Ventilation of the alveoli is carried out by alternating inhalation and exhalation. When you inhale, atmospheric air enters the alveoli, and when you exhale, air saturated with carbon dioxide is removed from the alveoli.

A normal calm inhalation is associated with the activity of the muscles of the diaphragm and external intercostal muscles. When you inhale, the diaphragm lowers, the ribs rise, and the distance between them increases. Normal calm exhalation occurs largely passively, with the internal intercostal muscles and some abdominal muscles actively working. When you exhale, the diaphragm rises, the ribs move down, and the distance between them decreases.

Types of breathing

The respiratory system performs only the first part of gas exchange. The rest is done by the circulatory system. There is a deep relationship between the respiratory and circulatory systems.

There are pulmonary respiration, which provides gas exchange between air and blood, and tissue respiration, which provides gas exchange between blood and tissue cells. It is carried out by the circulatory system, since the blood delivers oxygen to the organs and removes decay products and carbon dioxide from them.

Pulmonary breathing. The exchange of gases in the lungs occurs due to diffusion. The blood entering from the heart into the capillaries that encircle the pulmonary alveoli contains a lot of carbon dioxide; there is little of it in the air of the pulmonary alveoli, so it leaves the blood vessels and passes into the alveoli.

Oxygen also enters the blood due to diffusion. But in order for this gas exchange to occur continuously, it is necessary that the composition of gases in the pulmonary alveoli be constant. This constancy is maintained by pulmonary respiration: excess carbon dioxide is removed outside, and oxygen absorbed by the blood is replaced with oxygen from a fresh portion of the outside air.

Tissue respiration. Tissue respiration occurs in the capillaries, where the blood gives off oxygen and receives carbon dioxide. There is little oxygen in the tissues, therefore, oxyhemoglobin breaks down into hemoglobin and oxygen. Oxygen passes into tissue fluid and is used there by cells for the biological oxidation of organic substances. The energy released in this process is used for the vital processes of cells and tissues.

If there is insufficient oxygen supply to the tissues: the function of the tissue is disrupted because the breakdown and oxidation of organic substances stops, energy ceases to be released, and cells deprived of energy supply die.

The more oxygen is consumed in the tissues, the more oxygen is required from the air to compensate for the costs. That is why during physical work both cardiac activity and pulmonary respiration simultaneously increase.

Types of breathing

Based on the method of chest expansion, two types of breathing are distinguished:

• chest breathing(expansion of the chest is produced by raising the ribs), more often observed in women;
• abdominal breathing(expansion of the chest is produced by flattening the diaphragm) is more often observed in men.

Breathing happens:

• deep and superficial;
• frequent and rare.

Special types of respiratory movements are observed during hiccups and laughter. With frequent and shallow breathing, the excitability of the nerve centers increases, and with deep breathing, on the contrary, it decreases.

System and structure of the respiratory organs

The respiratory system includes:

• upper respiratory tract: nasal cavity, nasopharynx, pharynx;
• lower respiratory tract: larynx, trachea, main bronchi and lungs covered with pulmonary pleura.

The symbolic transition of the upper respiratory tract to the lower one occurs at the intersection of the digestive and respiratory systems in the upper part of the larynx. The respiratory tract provides connections between the environment and the main organs of the respiratory system - the lungs.

The lungs are located in the chest cavity, surrounded by the bones and muscles of the chest. The lungs are located in hermetically sealed cavities, the walls of which are lined with parietal pleura. Between the parietal and pulmonary pleura there is a slit-like pleural cavity. The pressure in it is lower than in the lungs, and therefore the lungs are always pressed against the walls of the chest cavity and take its shape.

Having entered the lungs, the main bronchi branch, forming a bronchial tree, at the ends of which there are pulmonary vesicles, alveoli. Along the bronchial tree, air reaches the alveoli, where gas exchange occurs between the atmospheric air that has reached the pulmonary alveoli (lung parenchyma), and the blood flowing through the pulmonary capillaries, which ensure the supply of oxygen to the body and the removal of gaseous waste products, including carbon dioxide. gas

Breathing process

Inhalation and exhalation are carried out by changing the size of the chest using the respiratory muscles. During one breath (at rest), 400-500 ml of air enters the lungs. This volume of air is called tidal volume (TIV). The same amount of air enters the atmosphere from the lungs during a quiet exhalation.

The maximum deep breath is about 2,000 ml of air. After maximum exhalation, about 1,200 ml of air remains in the lungs, called residual lung volume. After a quiet exhalation, approximately 1,600 ml remains in the lungs. This volume of air is called the functional residual capacity (FRC) of the lungs.

Thanks to the functional residual capacity (FRC) of the lungs, a relatively constant ratio of oxygen and carbon dioxide content is maintained in the alveolar air, since the FRC is several times larger than the tidal volume (TI). Only 2/3 of the DO reaches the alveoli, which is called the alveolar ventilation volume.

Without external respiration, the human body can usually survive up to 5-7 minutes (the so-called clinical death), after which loss of consciousness, irreversible changes in the brain and its death (biological death) occur.

Breathing is one of the few functions of the body that can be controlled consciously and unconsciously.

Functions of the respiratory system

• Breathing, gas exchange. The main function of the respiratory organs is to maintain a constant gas composition of the air in the alveoli: remove excess carbon dioxide and replenish oxygen carried away by the blood. This is achieved through breathing movements. When you inhale, the skeletal muscles expand the chest cavity, followed by the lungs, the pressure in the alveoli drops and outside air enters the lungs. When you exhale, the chest cavity decreases, its walls compress the lungs and air leaves them.
• Thermoregulation. In addition to ensuring gas exchange, the respiratory organs perform another important function: they participate in heat regulation. When breathing, water evaporates from the surface of the lungs, which leads to cooling of the blood and the entire body.
• Voice formation. The lungs create air currents that vibrate the vocal cords of the larynx. Speech is achieved through articulation, which involves the tongue, teeth, lips and other organs that direct sound flows.
• Air purification. The inner surface of the nasal cavity is lined with ciliated epithelium. It secretes mucus that moisturizes the incoming air. Thus, the upper respiratory tract performs important functions: warming, humidifying and purifying the air, as well as protecting the body from harmful influences through the air.

Lung tissue also plays an important role in processes such as hormone synthesis, water-salt and lipid metabolism. In the abundantly developed vascular system of the lungs, blood is deposited. The respiratory system also provides mechanical and immune protection against environmental factors.

Breathing regulation

Nervous regulation of breathing. Breathing is regulated automatically by the respiratory center, which is represented by a collection of nerve cells located in different parts of the central nervous system. The main part of the respiratory center is located in the medulla oblongata. The respiratory center consists of inhalation and exhalation centers, which regulate the functioning of the respiratory muscles.

Nervous regulation has a reflex effect on breathing. The collapse of the pulmonary alveoli, which occurs during exhalation, reflexively causes inhalation, and the expansion of the alveoli reflexively causes exhalation. Its activity depends on the concentration of carbon dioxide (CO2) in the blood and on nerve impulses coming from receptors in various internal organs and skin.A hot or cold irritant (sensory system) of the skin, pain, fear, anger, joy (and other emotions and stressors), physical activity quickly change the nature of respiratory movements.

It should be noted that there are no pain receptors in the lungs, therefore, in order to prevent diseases, periodic fluorographic examinations are carried out.

Humoral regulation of respiration. During muscle work, oxidation processes intensify. Consequently, more carbon dioxide is released into the blood. When blood with excess carbon dioxide reaches the respiratory center and begins to irritate it, the activity of the center increases. The person begins to breathe deeply. As a result, excess carbon dioxide is removed, and the lack of oxygen is replenished.

If the concentration of carbon dioxide in the blood decreases, the work of the respiratory center is inhibited and involuntary holding of breath occurs.

Thanks to nervous and humoral regulation, in any conditions the concentration of carbon dioxide and oxygen in the blood is maintained at a certain level.

When problems with external respiration arise, certain

Vital capacity of the lungs

The vital capacity of the lungs is an important indicator of breathing. If a person takes the deepest breath and then exhales as much as possible, then the exchange of exhaled air will make up the vital capacity of the lungs. The vital capacity of the lungs depends on the age, gender, height, and also on the degree of training of the person.

To measure the vital capacity of the lungs, a device such as a Spirometer is used. For humans, not only the vital capacity of the lungs is important, but also the endurance of the respiratory muscles. A person whose lung vital capacity is small and whose respiratory muscles are also weak has to breathe frequently and shallowly. This leads to the fact that fresh air remains mainly in the airways and only a small part of it reaches the alveoli.

Breathing and exercise

During physical activity, breathing usually increases. Metabolism accelerates, muscles require more oxygen.

Instruments for studying breathing parameters

• Capnograph- a device for measuring and graphically displaying the carbon dioxide content in the air exhaled by a patient over a certain period of time.
• Pneumograph- a device for measuring and graphically displaying the frequency, amplitude and shape of respiratory movements over a certain period of time.
• Spirograph- a device for measuring and graphically displaying the dynamic characteristics of breathing.
• Spirometer- a device for measuring vital capacity (vital capacity of the lungs).

OUR LUNGS LOVE:

1. Fresh air(with insufficient oxygen supply to the tissues: tissue function is impaired because the breakdown and oxidation of organic substances stops, energy ceases to be released, and cells deprived of energy supply die. Therefore, staying in a stuffy room leads to headaches, lethargy, and decreased performance ).

2. Exercises(during muscular work, oxidation processes intensify).

OUR LUNGS DO NOT LIKE:

1. Infectious and chronic respiratory diseases(sinusitis, sinusitis, tonsillitis, diphtheria, influenza, sore throat, acute respiratory infections, tuberculosis, lung cancer).

2. Polluted air(car exhausts, dust, polluted air, smoke, vodka fumes, carbon monoxide - all these components have an adverse effect on the body. Hemoglobin molecules that have captured carbon monoxide are permanently deprived of the ability to transfer oxygen from the lungs to the tissues. There is a lack of oxygen in the blood and tissues, which affects the functioning of the brain and other organs).

3. Smoking(narcogenic substances contained in nicotine are included in the metabolism and interfere with nervous and humoral regulation, disrupting both. In addition, substances in tobacco smoke irritate the mucous membrane of the respiratory tract, which leads to an increase in mucus secreted by it).

Now let's look at and analyze the respiratory process as a whole, and also trace the anatomy of the respiratory tract and a number of other features associated with this process.