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The relationship between the structure and functions of organs. Breath. The structure and functions of the respiratory system. Respiratory organs: description

Lecture 7

General structure and functions of the respiratory system

PLAN

1. The biological significance of respiration.

2. The structure of the respiratory system.

3. Breathing movements.

4. Lung volumes. Vital capacity of the lungs.

Basic concepts: respiration, gas exchange, respiratory organs, respiratory cycle, respiratory movements, lung volumes, vital capacity of the lungs.

Literature

1. Bugaev K.E., Markusenko N.N. etc. Age physiology. - Rostov-on-Don: "Voroshilovgradskaya Pravda", 1975.- P.107-115.

2. Ermolaev Yu.A. Age physiology: Proc. allowance for stud. ped. universities. - M.: Higher. school, 1985. S. 293-313.

3. Kiselev F.S. Anatomy and physiology of the child with the basics of school hygiene. - M.: Enlightenment, 1967.- S. 133-143.

4. Starushenko L.I. Clinical anatomy and human physiology: Proc. allowance M.: USMP, 2001. S. 77-86.

5. Khripkova A.G. Age physiology. - M .: Education, 1978. - S. 209-222.

The meaning of breath

Breath is a set of processes that result in the use of oxygen by the body and the release of carbon dioxide. Respiration includes the following processes: a) air exchange between external environment and alveoli of the lungs (pulmonary ventilation); b) exchange of gases between alveolar air and blood (diffusion of gases in the lungs) c) transport of gases by blood d) gas exchange between blood, tissues and cells; e) the use of oxygen by cells and the release of carbon dioxide by them (cellular respiration).

In addition to gas exchange, respiration is an important factor in thermoregulation. The lungs perform the function of excretion, since carbon dioxide, ammonia and some volatile compounds are excreted through them.

During expectoration, along with mucus, metabolic products are removed: urea, uric acid, mineral salts, dust particles and microorganisms.

Almost all complex transformations of substances in the body occur with the obligatory participation of oxygen. Without oxygen, metabolism is impossible and a constant supply of oxygen is necessary to preserve life. Breathing, like blood circulation, is extremely important for ensuring the homeostasis of the body. Respiratory failure leads not only to changes in the gas composition of the internal environment of the body, but also to profound changes in all metabolic reactions, in all life processes.



The structure of the respiratory system

The respiratory organs include the airways (nasal cavity, nasopharynx, larynx, trachea, bronchi) and lungs.

The respiratory system begins with the nasal cavity, which is divided by a cartilaginous septum into two halves, each of which is further divided by the nasal concha into the lower, middle and upper nasal passages. In the first days of life in children, breathing through the nose is difficult. The nasal passages in children are narrower than in adults, and are formed by the age of 14-15.

The walls of the nasal cavity are covered with a mucous membrane with ciliated epithelium, the cilia of which retain and remove mucus and microorganisms that settle on the mucous membranes. The mucous membrane has a dense network of blood vessels and capillaries. The blood flowing through these vessels warms or cools the air, a person inhales. The mucous membrane of the nasal cavity contains receptors that (perceive odors and determine the sense of smell. The nasal cavity is combined with the cavities that are in the bones of the skull: the maxillary, frontal, sphenoid sinuses. The air entering the lungs through the nasal cavity is cleansed, warmed and neutralized. This does not occur when breathing through the oral cavity.The nasal cavity is connected to the nasopharynx through the holes - the choanae.In the mucous membranes of the nasal cavity there are leukocytes that come to the surface of the mucous membrane from the blood vessels.Due to the phagocytic ability, leukocytes destroy microorganisms that enter the nasal cavity with inhaled The substance, lysozyme, which is present in the composition of mucus, has a detrimental effect on microorganisms.

The airways in children are much narrower than in adults. This makes it easier for the infection to enter the body of the child. During inflammatory processes in the nose, the mucous membrane swells, as a result of which breathing through the nose is formed or even becomes impossible, so children are forced to breathe through the mouth. And this contributes to the cooling of the respiratory tract to the lungs and the penetration of microorganisms and dust particles into them.

Nasopharynx- upper part of the pharynx. Pharynx- a muscular tube into which the cavity of the nose, mouth and larynx opens. The auditory tubes open into the nasopharynx and connect the pharyngeal cavity with the middle ear cavity. The nasopharynx in children is wide and short, the auditory tube is low. Diseases of the upper respiratory tract are often complicated by inflammation of the middle ear, because the infection easily penetrates the middle ear.

In 4-10 year old children, the so-called adenoid expansions are formed, that is, the expansion of the lymphatic tissue in the pharynx, as well as in the nose. In addition, adenoid growths can adversely affect the overall health and performance of children.

From the nasopharynx, air enters the pharynx, and then into larynx.

Larynx- located in the middle part of the neck and from the outside its part is visible as an increase, which is called the Adam's apple. The skeleton of the larynx is formed by several cartilages interconnected by joints, ligaments, muscles. The largest of these is the thyroid cartilage. From above, the entrance to the larynx is covered with the epiglottis, which prevents food from entering the larynx and respiratory tract.

The cavity of the larynx is covered with a mucous membrane with ciliated epithelium, which forms two pairs of folds that close the entrance to the larynx during swallowing. The lower pair of folds covers the vocal cords, the space between which is called glottis. During normal breathing, the vocal cords are relaxed and the gap between them narrows. Exhaled air, passing through a narrow gap, causes the vocal cords to vibrate - sound occurs. The pitch of the tone depends on the degree of tension of the vocal cords, and with strained connections, the sound is higher, with relaxation - lower. In addition to the vocal cords, the tongue, lips, cheeks, nasal cavity, resonators (pharynx and oral cavity) are involved in sound production. In men, the vocal cords are longer, which explains the lower voice.

The larynx in children is shorter, narrow and grows rapidly at 1-3 years of age and during puberty.

At the age of 12-14, the Adam's apple begins to grow in boys at the place of conjugation of the plates of the thyroid cartilage. After passing the larynx, the air enters the trachea.

Trachea- the lower part of the larynx is 10-13 cm long, inside it is covered with a mucous membrane. The trachea consists of 16-20 incomplete cartilage rings connected by ligaments. The back wall of the trachea is membranous, it has smooth muscle fibers, and it is adjacent to the esophagus, which creates favorable conditions for the passage of food through it.

At the level of 4-5 thoracic vertebrae, the trachea divides into the right and left bronchi, which are the main ones. They enter the gates of the corresponding lungs, where they divide into the lobar bronchi. Lobar bronchi in the lungs branch into smaller segmental bronchi, which, in turn, are divided (up to the 18th order) to lobular bronchi (up to 1 mm in diameter) and end in terminal bronchioles (0.3-0.5 mm in diameter). The entire branching system of the bronchi, from the main to the terminal bronchioles, is called bronchial tree.

In newborns, the trachea is about 4 cm, at 14-15 years old - about 7 cm. In children, the trachea and bronchi develop gradually. They grow mainly in parallel with the growth of the body. The lumen of the trachea and bronchi in children is much narrower than in adults, their cartilage has not yet grown stronger. Muscle elastic fibers are poorly developed. The mucous membrane that lines the trachea and bronchi is very delicate and rich in blood vessels. Therefore, the trachea and bronchi in children are more easily damaged than in adults.

Bronchioles end in alveolar passages, on the walls of which bubbles - alveoli covered with a dense network of blood capillaries where gas exchange occurs. In the lungs of an adult, there are 300-700 million alveoli, with a total surface area of ​​60-120m2. Such a huge surface provides a high rate of gas exchange in the lungs. The lungs are located in the chest cavity, on the sides of the heart.

The main structural and functional units of the lungs are alveoli. Alveoli- microscopic vesicles of the lungs, where gas exchange takes place between the blood and the inhaled air. The space between the lungs, called the mediastinum, houses the trachea, esophagus, thymus, heart, large vessels, lymph nodes, and some nerves.

The right and left lungs are not the same in both size and shape. The right lung consists of three parts, the left - of two. On the inner surface of the lungs are the gates of the lungs, through which the bronchi, nerves, pulmonary arteries, veins, and lymphatic vessels pass. Each lung is covered with a serous membrane called pleura. The pleura has two layers. One is tightly fused with the lungs, the second is attached to the chest. Between the sheets there is a gap filled with serous fluid. This fluid moisturizes the surfaces of the pleura facing each other, and thereby reduces friction between them during respiratory movements. There is no air in the pleural fissure, the pressure is negative - below atmospheric by 6-9 mm Hg. (0.8-1.2 kPa). The pressure inside the lungs is equal to atmospheric pressure, which ensures the normal function of the lungs: they do not move away from the chest wall during inspiration and stretch when the volume of the chest increases. Negative intrapleural pressure contributes to an increase in the respiratory surface of the lungs during inspiration, the return of blood to the heart and, thus, the improvement of blood circulation and lymphatic drainage.

The lungs in children are still underdeveloped, the alveoli are small, and the elastic tissue in them is underdeveloped. Blood filling of the lungs in children is increased. Up to 3 years in children, the lungs grow intensively, the number of alveoli up to 8 years reaches the number of alveoli in an adult. Between the ages of 3 and 7, the growth rate slows down. After 12 years, the alveoli grow vigorously. The volume of the lungs up to 12 years increases 10 times compared with the volume of the lungs of a newborn, and by the end of puberty - 20 times.

Breathing movements

The respiratory cycle consists of two phases: inhalation and exhalation. Thanks to the acts of inhalation and exhalation, which are carried out rhythmically, there is an exchange of gases between atmospheric air and the alveolar air, which is contained in the pulmonary vesicles. An active role in the act of inhalation belongs to the respiratory muscles.

During inhalation, the chest expands due to the lowering of the diaphragm and the raising of the ribs. Diaphragm- the formation that separates the chest cavity from the abdominal cavity has the form of a transversely placed dome-like muscle-tendon plate, the edges of which are attached to the walls of the chest. The diaphragm is lowered by contraction of the striated muscle fibers. When inhaling, the ribs rise up, with their front ends pushing the sternum forward, with an increase in the chest cavity and due to the contraction of the external intercostal muscles, which are attached obliquely from rib to rib.

In the process of inhalation, the intercartilaginous muscles of the trachea and bronchi participate. Deep inspiration is caused by the simultaneous contraction of the intercostal muscles, diaphragm, muscles of the chest and shoulder girdle. At the same time, a number of obstacles are overcome: the elastic traction of the lungs, the resistance of the costal cartilages, the mass of the chest, rises up, the resistance of the abdominal viscera and abdominal walls.

Between the chest wall and the surface of the lungs (between the parietal and visceral pleura) lies a gap with negative pressure. The pleural fissure is hermetically sealed, therefore, during the expansion of the chest, the lungs follow its walls, which, due to the elasticity of their tissues, are easily stretched. In distended lungs, air pressure drops below atmospheric pressure. The chest cavity is hermetically sealed and environment combined only through the respiratory tract. Therefore, in the presence of a pressure difference between atmospheric and lung air, outside air enters the lungs, that is, inhale.

After the end of the inhalation, the muscles relax and the chest returns to its original position (exhalation). Calm exhalation occurs passively, without the participation of muscles. In a deep exhalation, the abdominal muscles, internal intercostal and other muscles take part. When the muscles of the diaphragm relax, its dome rises under the pressure of the abdominal organs and becomes convex, which reduces the chest cavity in a vertical direction. A decrease in the size of the chest cavity leads to a decrease in the volume of the lungs, to an increase in pressure in the lungs, as a result of which part of the air leaves the lungs to the outside until the air pressure in the lungs is equal to atmospheric pressure.

In humans, either the muscles of the diaphragm or the intercostal muscles can participate in breathing. In the case of the predominance of the participation of the intercostal muscles, they speak of chest breathing, if the diaphragmatic muscles predominate, then such breathing is called abdominal.

In newborns, diaphragmatic breathing predominates with little involvement of the intercostal muscles. The diaphragmatic type of breathing persists until the second half of the first year of life. As the intercostal muscles develop and the child grows, the chest descends and the ribs gain an oblique position. The breathing of infants becomes chest-abdominal with the advantage of diaphragmatic.

At the age of 3 to 7 years, due to the development of the shoulder girdle, the chest type of breathing begins to predominate more and more and up to 7 years it becomes pronounced. At the age of 7-8, gender differences in the type of breathing begin: in boys, the abdominal type of breathing predominates, in girls - chest.

An adult makes about 15-17 breaths per minute and inhales about 500 ml of air in one breath. The ratio of respiratory rate and heart rate is 1: 4-1: 5. During muscular work, breathing increases by 2-3 times. In diseases, the frequency and depth of breathing change.

With deep breathing, alveolar air is ventilated by 80-90%, which ensures greater diffusion of gases. When shallow - most of the inhaled air remains in the dead space - the nasopharynx, oral cavity, trachea, bronchi.

The breathing of a newborn child is 48-63 respiratory movements per minute, frequent, superficial. In children of the first year during wakefulness - 50-60, during sleep 35-40, in children 4-6 years old - 23-26 cycles per minute, in children school age 18-20 times per minute.

Breath- this is a set of processes that ensure the entry of oxygen into the body, its use in the biological oxidation of organic substances and the removal of carbon dioxide from the body, formed in the process of metabolism. As a result of biological oxidation, energy is released in the cells, which is used to strengthen the cardiovascular system, improve the blood supply to all organs and tissues of the body, and increase resistance to various diseases by regular physical exercises and work corresponding to the age and individual capabilities of the body.

It must be remembered that excessive physical and mental stress can cause disruption of the normal functioning of the heart, its overwork.

Especially harmful effects on the cardiovascular system have smoking and drinking alcohol. Alcohol and nicotine (the poison contained in tobacco) poison the heart muscle and nervous system, causing sharp disturbances in the regulation of vascular tone and heart activity. They lead to the development of severe diseases of the cardiovascular system and can be the cause of sudden death. Young people who smoke and drink alcohol are more likely than others to develop spasms of the heart vessels, causing severe heart attacks and sometimes death.

The respiratory organs - the nasal cavity, pharynx, larynx, trachea, bronchi and lungs - provide air circulation and gas exchange (43).

nasal cavity is divided into two halves by an osseocartilaginous septum. Its inner surface is formed by three winding nasal 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. Abundant blood supply to the mucous membrane warms the air. On the moist surface of the mucous membrane, dust particles and microbes that are in the inhaled air are retained, which are neutralized by mucus and leukocytes.

The mucous membrane of the respiratory tract is lined ciliated epithelium, whose cells have the thinnest outgrowths on the outer surface - 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. Air passes through the nasopharynx into the larynx.

Larynx serves to conduct air from the pharynx to the trachea and, together with the oral cavity, is an organ of sound production and articulate speech. The larynx is a hollow organ, the walls of which are formed by paired and unpaired cartilages, connected by ligaments, joints and muscles. Stretched between the anterior and posterior cartilages vocal cords, forming the glottis. Some of the muscles of the larynx narrow the gap during contraction, while others expand. The sound of a voice is the result of the vibration of the vocal cords when air is exhaled. The shades of the voice, its timbre depend on the length of the vocal cords and on the system of resonators, which are the cavities of the larynx, pharynx, mouth, nose and its paranasal sinuses.

Trachea or windpipe is a continuation of the larynx and is a tube 9-11 cm long and 15-18 mm in diameter. Its walls consist of cartilaginous semirings connected 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. The wall of the large bronchi contains incomplete cartilaginous rings, their lumen is always open. The walls of the small bronchi do not have cartilage and consist of elastic and smooth muscle fibers.

Lungs.

In the lungs, the bronchi branch, forming a "bronchial tree", on the terminal bronchial branches of which there are tiny 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 thin film of a substance that prevents them from falling off. The alveoli are surrounded by a dense network of capillaries. Gas exchange takes place through their walls. The lungs are covered with a membrane - pulmonary pleura, which goes into parietal pleura, lining the inner wall of the chest cavity. slit-like pleural space filled in between pleural fluid, facilitating the sliding of the pleura during respiratory movements.

Gas exchange in the lungs and tissues. Gas exchange in the lungs occurs by diffusion. Oxygen passes through the thin walls of the alveoli and capillaries from the air into the blood, and carbon dioxide from the blood into the air (44). In the blood, oxygen enters the red blood cells and combines with hemoglobin. Oxygenated blood becomes arterial and enters the left atrium through the pulmonary veins.

The exchange of gases in tissues is carried out in capillaries. Through their thin walls, oxygen enters from the blood into the tissue fluid and cells, and carbon dioxide from the tissues passes into the blood. The difference in oxygen concentration in tissues and blood contributes to breaking the fragile bond of oxygen with hemoglobin and its diffusion into cells. The concentration of carbon dioxide in the tissues where it is formed is higher than in the blood. Therefore, it diffuses into the blood, where it binds to hemoglobin or plasma chemicals, is transported to the lungs and released into the atmosphere.

Vital capacity consists of tidal volume, inspiratory reserve volume and expiratory reserve volume. Tidal volume called the amount of air entering the lungs during one breath. At rest, it is approximately 500 cm 3 and corresponds to the volume of exhaled air during one exhalation. If, after a calm breath, an enhanced additional breath is taken, then another 1500 cm 3 of air can enter the lungs, which is inspiratory reserve volume.

After a calm exhalation, you can exhale another 1500 cm 3 of air at maximum tension. This expiratory reserve volume.

Thus, the largest amount of air that a person can exhale after the deepest breath is about 3500 cm 3 and is the vital capacity of the lungs. It is greater in athletes than in untrained people, and depends on the degree of development of the chest, sex and age. Under the influence of smoking, the vital capacity of the lungs decreases.

Even after maximum expiration, 1000-1500 cm 3 of air always remains in the lungs, which is called residual volume.

The human respiratory organs include:

  • nasal cavity;
  • paranasal sinuses;
  • larynx;
  • trachea
  • bronchi;
  • lungs.

Consider the structure of the respiratory organs and their functions. This will help you better understand how diseases of the respiratory system develop.

The external nose, which we see on the face of a person, consists of thin bones and cartilage. From above they are covered with a small layer of muscles and skin. The nasal cavity is bounded in front by the nostrils. On the reverse side, the nasal cavity has openings - choanae, through which air enters the nasopharynx.

The nasal cavity is divided in half by the nasal septum. Each half has an inner and outer wall. On the side walls there are three protrusions - nasal conchas that separate the three nasal passages.

There are openings in the two upper passages, through which there is a connection with the paranasal sinuses. The mouth of the nasolacrimal duct opens into the lower passage, through which tears can enter the nasal cavity.

The entire nasal cavity is covered from the inside with a mucous membrane, on the surface of which lies a ciliated epithelium, which has many microscopic cilia. Their movement is directed from front to back, towards the choanae. Therefore, most of the mucus from the nose enters the nasopharynx, and does not go out.

In the zone of the upper nasal passage is the olfactory region. There are sensitive nerve endings - olfactory receptors, which, through their processes, transmit the received information about smells to the brain.

The nasal cavity is well supplied with blood and has many small vessels that carry arterial blood. The mucous membrane is easily vulnerable, so nosebleeds are possible. Particularly severe bleeding occurs when a foreign body is damaged or when the venous plexus is injured. Such plexuses of veins can quickly change their volume, leading to nasal congestion.

Lymphatic vessels communicate with the spaces between the membranes of the brain. In particular, this explains the possibility of rapid development of meningitis in infectious diseases.

The nose performs the function of conducting air, smelling, and is also a resonator for the formation of voice. An important role of the nasal cavity is protective. The air passes through the nasal passages, which have a fairly large area, and is warmed and moistened there. Dust and microorganisms partially settle on the hairs located at the entrance to the nostrils. The rest, with the help of cilia of the epithelium, are transmitted to the nasopharynx, and from there they are removed when coughing, swallowing, blowing your nose. The mucus of the nasal cavity also has a bactericidal effect, that is, it kills some of the microbes that have got into it.

Paranasal sinuses

The paranasal sinuses are cavities that lie in the bones of the skull and have a connection with the nasal cavity. They are covered from the inside with mucous, have the function of a voice resonator. Paranasal sinuses:

  • maxillary (maxillary);
  • frontal;
  • wedge-shaped (main);
  • cells of the labyrinth of the ethmoid bone.

Paranasal sinuses

The two maxillary sinuses are the largest. They are located in the thickness of the upper jaw under the orbits and communicate with the middle course. The frontal sinus is also paired, located in the frontal bone above the eyebrows and has the shape of a pyramid, with the top facing down. Through the nasolabial canal, it also connects to the middle course. The sphenoid sinus is located in the sphenoid bone on the back of the nasopharynx. In the middle of the nasopharynx, holes in the cells of the ethmoid bone open.

The maxillary sinus most closely communicates with the nasal cavity, therefore, often after the development of rhinitis, sinusitis also appears when the outflow of inflammatory fluid from the sinus into the nose is blocked.

Larynx

This is the upper respiratory tract, which is also involved in the formation of the voice. It is located approximately in the middle of the neck, between the pharynx and trachea. The larynx is formed by cartilage, which are connected by joints and ligaments. In addition, it is attached to the hyoid bone. Between the cricoid and thyroid cartilages is a ligament, which is dissected in acute stenosis of the larynx to provide air access.

The larynx is lined with ciliated epithelium, and on the vocal cords, the epithelium is stratified squamous, rapidly renewing and allowing the ligaments to be resistant to constant stress.

Under the mucous membrane of the lower larynx, below the vocal cords, there is a loose layer. It can quickly swell, especially in children, causing laryngospasm.

Trachea

The lower respiratory tract starts from the trachea. She continues the larynx, and then goes into the bronchi. The organ looks like a hollow tube, consisting of cartilaginous half-rings tightly connected to each other. The length of the trachea is about 11 cm.

At the bottom, the trachea forms the two main bronchi. This zone is an area of ​​bifurcation (bifurcation), it has many sensitive receptors.

The trachea is lined with ciliated epithelium. Its feature is a good absorption capacity, which is used for inhalation of drugs.

With stenosis of the larynx, in some cases, a tracheotomy is performed - the anterior wall of the trachea is dissected and a special tube is inserted through which air enters.

Bronchi

This is a system of tubes through which air passes from the trachea to the lungs and vice versa. They also have a cleansing function.

The bifurcation of the trachea is located approximately in the interscapular zone. The trachea forms two bronchi, which go to the corresponding lung and there are divided into lobar bronchi, then into segmental, subsegmental, lobular, which are divided into terminal (terminal) bronchioles - the smallest of the bronchi. This entire structure is called the bronchial tree.

The terminal bronchioles have a diameter of 1–2 mm and pass into the respiratory bronchioles, from which the alveolar passages begin. At the ends of the alveolar passages are pulmonary vesicles - alveoli.

Trachea and bronchi

From the inside, the bronchi are lined with ciliated epithelium. The constant wave-like movement of the cilia brings up the bronchial secret - a liquid that is continuously formed by the glands in the wall of the bronchi and washes away all impurities from the surface. This removes microorganisms and dust. If there is an accumulation of thick bronchial secretions, or a large foreign body enters the lumen of the bronchi, they are removed with the help of a protective mechanism aimed at cleansing the bronchial tree.

In the walls of the bronchi there are annular bundles of small muscles that are able to "block" the air flow when it is contaminated. This is how it arises. In asthma, this mechanism begins to work when a substance that is common to a healthy person, such as plant pollen, is inhaled. In these cases, bronchospasm becomes pathological.

Respiratory organs: lungs

A person has two lungs located in the chest cavity. Their main role is to ensure the exchange of oxygen and carbon dioxide between the body and the environment.

How are the lungs arranged? They are located on the sides of the mediastinum, in which the heart and blood vessels lie. Each lung is covered with a dense membrane - the pleura. Normally, there is a little fluid between its sheets, which ensures the sliding of the lungs relative to the chest wall during breathing. The right lung is larger than the left. Through the root, located on the inside of the organ, the main bronchus, large vascular trunks, and nerves enter it. The lungs are made up of lobes: the right - of three, the left - of two.

The bronchi, getting into the lungs, are divided into smaller and smaller. Terminal bronchioles pass into alveolar bronchioles, which separate and turn into alveolar passages. They also branch out. At their ends are alveolar sacs. On the walls of all structures, starting with the respiratory bronchioles, alveoli (breathing vesicles) open. The alveolar tree consists of these formations. The ramifications of one respiratory bronchiole eventually form the morphological unit of the lungs - the acinus.

The structure of the alveoli

The mouth of the alveoli has a diameter of 0.1 - 0.2 mm. From the inside, the alveolar vesicle is covered with a thin layer of cells lying on a thin wall - the membrane. Outside, a blood capillary is adjacent to the same wall. The barrier between air and blood is called aerohematic. Its thickness is very small - 0.5 microns. An important part of it is the surfactant. It consists of proteins and phospholipids, lines the epithelium and retains the rounded shape of the alveoli during exhalation, prevents the entry of microbes from the air into the blood and fluids from the capillaries into the lumen of the alveoli. Premature babies have poorly developed surfactant, which is why they so often have breathing problems immediately after birth.

In the lungs there are vessels of both circles of blood circulation. The arteries of the great circle carry oxygen-rich blood from the left ventricle of the heart and directly feed the bronchi and lung tissue, like all other human organs. The arteries of the pulmonary circulation bring venous blood from the right ventricle to the lungs (this is the only example when venous blood flows through the arteries). It flows through the pulmonary arteries, then enters the pulmonary capillaries, where gas exchange occurs.

The essence of the breathing process

Gas exchange between the blood and the external environment, which takes place in the lungs, is called external respiration. It occurs due to the difference in the concentration of gases in the blood and air.

The partial pressure of oxygen in air is greater than in venous blood. Due to the pressure difference, oxygen through the air-blood barrier penetrates from the alveoli into the capillaries. There it attaches to red blood cells and spreads through the bloodstream.

Gas exchange through the air-blood barrier

The partial pressure of carbon dioxide in venous blood is greater than in air. Because of this, carbon dioxide leaves the blood and exits with exhaled air.

Gas exchange is a continuous process that continues as long as there is a difference in the content of gases in the blood and the environment.

During normal breathing, about 8 liters of air passes through the respiratory system per minute. With exercise and diseases accompanied by an increase in metabolism (for example, hyperthyroidism), pulmonary ventilation increases, shortness of breath appears. If increased respiration cannot cope with maintaining normal gas exchange, the oxygen content in the blood decreases - hypoxia occurs.

Hypoxia also occurs in high altitude conditions, where the amount of oxygen in the external environment is reduced. This leads to the development of mountain sickness.

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

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

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

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

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

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

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

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

Stages of the breathing process

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

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

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

The value of breathing for a person

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

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

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