Topic 8. AGE CHARACTERISTICS OF THE RESPIRATORY ORGANS

8.1. The structure of the respiratory and vocal apparatus

nasal cavity. When you breathe with your mouth closed, air enters the nasal cavity, and when you breathe open, it enters the oral cavity. The formation of the nasal cavity involves bones and cartilage, which also make up the nasal skeleton. Most of the mucous membrane of the nasal cavity is covered with multirow ciliated columnar epithelium, which contains mucous glands, and its smaller part contains olfactory cells. Thanks to the movement of the cilia of the ciliated epithelium, dust that enters with inhaled air is expelled out.

The nasal cavity is divided in half by the nasal septum. Each half has three turbinates - upper, middle and lower. They form three nasal passages: the upper one is under the upper concha, the middle one is under the middle concha, and the lower one is between the lower concha and the bottom of the nasal cavity. The inhaled air enters through the nostrils and, after passing through the nasal passages of each half of the nasal cavity, exits it into the nasopharynx through two posterior openings - the choanae.

The nasolacrimal canal opens into the nasal cavity, through which excess tears are excreted.

Adjacent to the nasal cavity are adnexal cavities, or sinuses connected to it by openings: maxillary, or maxillary (located in the body of the upper jaw), sphenoid (in the sphenoid bone), frontal (in the frontal bone) and ethmoid labyrinth (in the ethmoid bone). The inhaled air, in contact with the mucous membrane of the nasal cavity and adnexal cavities, in which there are numerous capillaries, is warmed and moistened.

Larynx. The nasopharynx is the upper part of the pharynx that conducts air from the nasal cavity to the larynx, which is attached to the hyoid bone. The larynx forms the initial part of the respiratory tube itself, which continues into the trachea, and at the same time functions as a voice apparatus. It consists of three unpaired and three paired cartilages, connected by ligaments. The unpaired cartilages include the thyroid, cricoid and epiglottis cartilages, and the paired cartilages include the arytenoid, corniculate and sphenoid. The main cartilage is the cricoid. Its narrow part is facing anteriorly, and its wide part is facing the esophagus. At the back of the cricoid cartilage, two triangular arytenoid cartilages are located symmetrically on the right and left sides, movably articulated with its posterior part. When the muscles contracting, pulling back the outer ends of the arytenoid cartilages, and the intercartilaginous muscles relax, these cartilages rotate around their axis and the glottis opens wide, necessary for inhalation. With contraction of the muscles between the arytenoid cartilages and tension of the ligaments, the glottis looks like two tightly stretched parallel muscle ridges, preventing the flow of air from the lungs.

Vocal cords. The true vocal cords are located in the sagittal direction from the internal angle of the junction of the plates of the thyroid cartilage to the vocal processes of the arytenoid cartilages. The true vocal cords include the internal thyroarytenoid muscles. A certain relationship is established between the degree of tension of the vocal cords and the pressure of air from the lungs: the stronger the ligaments are closed, the more pressure the air escaping from the lungs puts on them. This regulation is carried out by the muscles of the larynx and is important for the formation of sounds.

When swallowing, the entrance to the larynx is closed by the epiglottis. The mucous membrane of the larynx is covered with multi-row ciliated epithelium, and the vocal cords - with stratified squamous epithelium.

In the mucous membrane of the larynx there are various receptors that perceive tactile, temperature, chemical and pain stimuli; they form two reflex zones. Part of the laryngeal receptors is located superficially, where the mucous membrane covers the cartilage, and the other part is deep in the perichondrium, at the points of muscle attachment, in the pointed parts of the vocal processes. Both groups of receptors are located on the path of the inhaled air and are involved in the reflex regulation of breathing and in the protective reflex of closing the glottis. These receptors, signaling changes in the position of the cartilage and contractions of the muscles involved in voice formation, reflexively regulate it.

Trachea. The larynx passes into the windpipe, or trachea, which in an adult is 11-13 cm long and consists of 15-20 half-rings of hyaline cartilage connected by membranes of connective tissue. The cartilages are not closed at the back, so the esophagus, located behind the trachea, can enter its lumen when swallowing. The mucous membrane of the trachea is covered with multirow ciliated epithelium, the cilia of which create a flow of fluid secreted by the glands towards the pharynx; it removes dust particles settled from the air. The powerful development of elastic fibers prevents the formation of folds of the mucous membrane, which reduce the access of air. In the fibrous membrane, located outward from the cartilaginous half-rings, there are blood vessels and nerves.

Bronchi. The trachea branches into two main bronchi; each of them enters the gate of one of the lungs and divides into three branches in the right lung, consisting of three lobes, and two branches in the left lung, consisting of two lobes. These branches split into smaller ones. The wall of the large bronchi has the same structure as the trachea, but it contains closed cartilaginous rings; There are smooth muscle fibers in the wall of the small bronchi. The inner lining of the bronchi consists of ciliated epithelium.

The smallest bronchi - up to 1 mm in diameter - are called bronchioles. Each bronchiole is part of a lung lobule (lung lobes are made up of hundreds of lobules). The bronchiole in the lobule is divided into 12-18 terminal bronchioles, which, in turn, are divided into alveolar bronchioles.

Finally, the alveolar bronchioles branch into alveolar ducts, which are made up of alveoli. The thickness of the epithelial layer of the alveoli is 0,004 mm. The capillaries are attached to the alveoli. Gas exchange occurs through the walls of the alveoli and capillaries. The number of alveoli is approximately 700 million. The total surface of all alveoli in a man is up to 130 square meters. m, for a woman - up to 103,5 sq. m.

Outside, the lungs are covered with an airtight serous membrane, or visceral pleura, which passes into the pleura that covers the inside of the chest cavity - the parietal, or parietal, pleura.

8.2. Breathing movements. Acts of inhalation and exhalation

Due to the rhythmically performed acts of inhalation and exhalation, an exchange of gases takes place between atmospheric and alveolar air located in the pulmonary vesicles. There is no muscle tissue in the lungs, so they cannot actively contract. An active role in the act of inhalation and exhalation belongs to the respiratory muscles. With paralysis of the respiratory muscles, breathing becomes impossible, although the respiratory organs are not affected.

When inhaling, the external intercostal muscles and the diaphragm contract. The intercostal muscles lift the ribs and take them somewhat to the side, while the volume of the chest increases. When the diaphragm contracts, its dome flattens, which also leads to an increase in the volume of the chest. Other muscles of the chest and neck also take part in deep breathing. The lungs, being in a hermetically sealed chest, are passive and follow its moving walls during inhalation and exhalation, since they are attached to the chest with the help of the pleura. This is also facilitated by negative pressure in the chest cavity: negative pressure is called pressure below atmospheric. During inspiration, the pressure in the chest cavity is lower than atmospheric by 9-12 mm Hg. Art., and during exhalation - by 2-6 mm Hg. Art.

During development, the chest grows faster than the lungs, so the lungs are constantly (even when exhaling) stretched. The stretched elastic lung tissue tends to shrink. The force with which lung tissue is compressed counteracts atmospheric pressure. Around the lungs, in the pleural cavity, pressure is created equal to atmospheric pressure minus the elastic recoil of the lungs. This creates negative pressure around the lungs. Due to it, in the pleural cavity, the lungs follow the expanded chest; the lungs are stretched. In a distended lung, the pressure becomes lower than atmospheric pressure, due to which atmospheric air rushes into the lungs through the respiratory tract. The more the volume of the chest increases during inhalation, the more the lungs are stretched and the deeper the inhalation.

When the respiratory muscles relax, the ribs descend to their original position, the dome of the diaphragm rises, the volume of the chest and lungs decreases, and air is exhaled outward. In a deep exhalation, the abdominal muscles, internal intercostal and other muscles take part.

Types of breathing. In young children, the ribs have a slight bend and occupy an almost horizontal position. The upper ribs and the entire shoulder girdle are located high, the intercostal muscles are weak. Therefore, in newborns, diaphragmatic breathing predominates with little participation of the intercostal muscles. This 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 moves down and the ribs take on an oblique position. The breathing of infants now becomes thoraco-abdominal with a predominance of diaphragmatic breathing.

At the age of 3 to 7 years, due to the development of the shoulder girdle, the chest type of breathing begins to predominate, and by the age of 7 it becomes pronounced.

At the age of 7-8, gender differences in the type of breathing begin: in boys, the abdominal type of breathing becomes predominant, in girls - chest. The sexual differentiation of respiration ends by the age of 14-17.

Respiration depth and frequency. The unique structure of the chest and the low endurance of the respiratory muscles make breathing movements in children less deep and frequent. An adult makes an average of 15-17 breathing movements per minute; in one breath during quiet breathing, he inhales 500 ml of air. During muscular work, breathing increases 2-3 times. In trained people, during the same work, the volume of pulmonary ventilation gradually increases, as breathing becomes rarer and deeper. During deep breathing, 80-90% of the alveolar air is ventilated. This ensures greater diffusion of gases through the alveoli. With shallow and frequent breathing, ventilation of the alveolar air is much less and a relatively large part of the inhaled air remains in the so-called dead space - in the nasopharynx, oral cavity, trachea, and bronchi. Thus, in trained people, the blood is more saturated with oxygen than in untrained people.

The depth of breathing is characterized by the volume of air entering the lungs in one breath - respiratory air. The breathing of a newborn is frequent and shallow, while its frequency is subject to significant fluctuations: 48-63 respiratory cycles per minute during sleep. The frequency of respiratory movements per minute during wakefulness is: 50-60 - in children of the first year of life; 35-40 - in children 1-2 years old; 25-35 - in children 2-4 years old; 23-26 - in children 4-6 years old. In school-age children, there is a further decrease in breathing - up to 18-20 times per minute.

The high frequency of respiratory movements in the child provides high pulmonary ventilation. The volume of respiratory air in a child is: 30 ml - in 1 month; 70 ml - in 1 year; 156 ml - at 6 years old; 230 ml - at 10 years old; 300 ml - at 14 years old.

Due to the high respiratory rate in children, the minute volume of breathing (in terms of 1 kg of weight) is much higher than in adults. The minute volume of breathing is the amount of air that a person inhales in 1 minute. It is determined by the product of the value of respiratory air by the number of respiratory movements in 1 minute. The minute volume of breathing is:

▪ 650-700 ml of air - in a newborn;

▪ 2600-2700 ml - by the end of the first year of life;

▪ 3500 ml - by 6 years;

▪ 4300 ml - by 10 years;

▪ 4900 ml - at 14 years old;

▪ 5000-6000 ml - in an adult.

Vital capacity of the lungs. At rest, an adult can inhale and exhale about 500 ml of air, and with vigorous breathing - about another 1500 ml of air. The largest amount of air that a person can exhale after a deep breath is called the vital capacity of the lungs.

The vital capacity of the lungs changes with age, depending on gender, the degree of development of the chest, respiratory muscles. As a rule, it is more in men than in women; athletes have more than untrained people. For example, for weightlifters, the vital capacity of the lungs is about 4000 ml, for football players - 4200 ml, for gymnasts - 4300, for swimmers - 4900, for rowers - 5500 ml or more.

Since the measurement of lung capacity requires the active and conscious participation of the subject, it can be determined in a child only after 4-5 years.

By the age of 16-17, the vital capacity of the lungs reaches values ​​characteristic of an adult.

8.3. Gas exchange in the lungs

Composition of inhaled, exhaled and alveolar air. Ventilation of the lungs occurs through inhalation and exhalation. Thus, a relatively constant gas composition is maintained in the alveoli. A person breathes atmospheric air containing oxygen (20,9%) and carbon dioxide (0,03%), and exhales air containing 16,3% oxygen and 4% carbon dioxide. In alveolar air, oxygen is 14,2%, carbon dioxide is 5,2%. The increased content of carbon dioxide in the alveolar air is explained by the fact that when exhaling, air that is in the respiratory organs and airways is mixed with the alveolar air.

In children, the lower efficiency of pulmonary ventilation is expressed in a different gas composition of both exhaled and alveolar air. The younger the child, the greater the percentage of oxygen and the lower the percentage of carbon dioxide in the exhaled and alveolar air, i.e. oxygen is used by the child's body less efficiently. Therefore, in order to consume the same volume of oxygen and release the same volume of carbon dioxide, children need to perform respiratory acts much more often.

Gas exchange in the lungs. In the lungs, oxygen from the alveolar air passes into the blood, and carbon dioxide from the blood enters the lungs.

The movement of gases is provided by diffusion. According to the laws of diffusion, a gas propagates from an environment with a high partial pressure to an environment with a lower pressure. Partial pressure is the part of the total pressure that is accounted for by the proportion of a given gas in a gas mixture. The higher the percentage of gas in the mixture, the higher its partial pressure. For gases dissolved in a liquid, the term "voltage" is used, corresponding to the term "partial pressure" used for free gases.

In the lungs, gas exchange takes place between the air contained in the alveoli and the blood. The alveoli are surrounded by a dense network of capillaries. The walls of the alveoli and the walls of the capillaries are very thin. For the implementation of gas exchange, the determining conditions are the surface area through which the diffusion of gases is carried out, and the difference in the partial pressure (voltage) of the diffusing gases. The lungs ideally meet these requirements: with a deep breath, the alveoli stretch and their surface reaches 100-150 square meters. m (the surface of the capillaries in the lungs is no less large), there is a sufficient difference in the partial pressure of the gases of the alveolar air and the tension of these gases in the venous blood.

Oxygen binding in blood. In the blood, oxygen combines with hemoglobin, forming an unstable compound - oxyhemoglobin, 1 g of which can bind 1,34 cubic meters. see oxygen. The amount of oxyhemoglobin formed is directly proportional to the partial pressure of oxygen. In alveolar air, the partial pressure of oxygen is 100-110 mm Hg. Art. Under these conditions, 97% of the hemoglobin in the blood is bound to oxygen.

In the form of oxyhemoglobin, oxygen is carried from the lungs to the tissues in the blood. Here, the partial pressure of oxygen is low, and oxyhemoglobin dissociates, releasing oxygen, which ensures the supply of oxygen to the tissues.

The presence of carbon dioxide in the air or tissues reduces the ability of hemoglobin to bind oxygen.

Carbon dioxide fixation in the blood. Carbon dioxide is carried in the blood in the chemical compounds sodium bicarbonate and potassium bicarbonate. Part of it is transported by hemoglobin.

In the capillaries of tissues, where the tension of carbon dioxide is high, the formation of carbonic acid and carboxyhemoglobin occurs. In the lungs, carbonic anhydrase, contained in red blood cells, promotes dehydration, which leads to the displacement of carbon dioxide from the blood.

Gas exchange in the lungs in children is closely related to the regulation of acid-base balance. In children, the respiratory center is very sensitive to the slightest changes in the pH reaction of the blood. Therefore, even with minor shifts in balance towards acidification, shortness of breath occurs in children. With development, the diffusion capacity of the lungs increases due to an increase in the total surface of the alveoli.

The body's need for oxygen and the release of carbon dioxide depends on the level of oxidative processes occurring in the body. With age, this level decreases, which means that the amount of gas exchange per 1 kg of weight decreases as the child grows.

8.4. Hygienic requirements for the air environment of educational institutions

The hygienic properties of the air environment are determined not only by its chemical composition, but also by its physical state: temperature, humidity, pressure, mobility, atmospheric electric field voltage, solar radiation, etc. For normal human life, the constancy of body temperature and the environment is of great importance, which has influence on the equilibrium of the processes of heat generation and heat transfer.

The high temperature of the surrounding air makes it difficult to release heat, which leads to an increase in body temperature. At the same time, the pulse and breathing become more frequent, fatigue increases, and working capacity decreases. It also hinders heat transfer and enhances sweating when a person stays in conditions of high relative humidity. At low temperatures, there is a large heat loss, which can lead to hypothermia of the body. With high humidity and low temperatures, the risk of hypothermia and colds increases significantly. In addition, the loss of heat by the body depends on the speed of air movement and the body itself (riding an open car, bicycle, etc.).

The electric and magnetic fields of the atmosphere also affect humans. For example, negative air particles have a positive effect on the body (relieve fatigue, increase efficiency), and positive ions, on the contrary, depress breathing, etc. Negative air ions are more mobile, and they are called light, positive ones are less mobile, therefore they are called heavy . In clean air, light ions predominate, and as it becomes polluted, they settle on dust particles, water droplets, turning into heavy ones. Therefore, the air becomes warm, stale and stuffy.

The air contains impurities of various origins: dust, smoke, various gases. All this adversely affects the health of people, animals and plant life.

In addition to dust, the air also contains microorganisms - bacteria, spores, mold fungi, etc. They are especially numerous in enclosed spaces.

Microclimate of school premises. Microclimate is the totality of physicochemical and biological properties of the air environment. For a school, this environment consists of its premises, for a city - its territory, etc. Hygienically normal air in a school is an important condition for the progress and performance of students. When 35-40 students stay in a classroom or office for a long time, the air ceases to meet hygienic requirements. Its chemical composition, physical properties and bacterial contamination change. All these indicators increase sharply towards the end of the lessons.

An indirect indicator of indoor air pollution is carbon dioxide content. The maximum allowable concentration (MPC) of carbon dioxide in school buildings is 0,1%, but even at a lower concentration (0,08%), a decrease in the level of attention and concentration is observed in young children.

The most favorable conditions in the classroom are a temperature of 16-18 °C and a relative humidity of 30-60%. With these standards, the working capacity and good health of students are preserved for the longest time. At the same time, the difference in air temperature along the vertical and horizontal of the class should not exceed 2-3 ° C, and the air speed should not exceed 0,1-0,2 m / s.

In the sports hall, recreational facilities, workshops, the air temperature should be maintained at 14-15 °C. Estimated norms of air volume per student in a class (the so-called air cube) usually do not exceed 4,5-6 cubic meters. m. But in order for the concentration of carbon dioxide in the air of the class during the lesson not to exceed 0,1%, a child of 10-12 years old needs about 16 cubic meters. m of air. At the age of 14-16 years, the need for it increases to 25-26 cubic meters. m. This value is called the volume of ventilation: the older the student, the greater it is. To ensure the specified volume, a three-fold change of air is necessary, which is achieved by ventilation (airing) of the room.

Natural ventilation. The flow of outside air into the room due to the difference in temperature and pressure through pores and cracks in the building material or through specially made openings is called natural ventilation. To ventilate classrooms of this type, windows and transoms are used. The latter have an advantage over vents, since the outside air first flows upward through the open transom, to the ceiling, where it warms up and descends warmly. At the same time, people in the room do not become overcooled and feel an influx of fresh air. Transoms can be left open during classes, even in winter.

The area of ​​open windows or transoms should not be less than 1/50 of the class floor area - this is the so-called ventilation coefficient. Airing classrooms should be carried out regularly, after each lesson. The most effective is through ventilation, when during the break the vents (or windows) and the doors of the classroom are opened at the same time. Through ventilation allows for 5 minutes to reduce the concentration of CO2 to normal, reduce humidity, the number of microorganisms and improve the ionic composition of the air. However, with such ventilation, there should be no children in the room.

Particular attention is paid to the ventilation of cabinets, chemical, physical and biological laboratories, where toxic gases and vapors may remain after experiments.

Artificial ventilation. This is supply, exhaust and supply and exhaust (mixed) ventilation with natural or mechanical impulse. Such ventilation is most often installed where it is necessary to remove exhaust air and gases generated during experiments. It is called forced ventilation, since the air is exhausted outside using special exhaust ducts that have several holes under the ceiling of the room. Air from the premises is directed to the attic and through pipes removed outside, where to enhance the air flow in the exhaust ducts, thermal stimulators of air movement - deflectors or electric fans - are installed. The installation of this type of ventilation is provided during the construction of buildings.

Exhaust ventilation should work especially well in latrines, cloakrooms, and a canteen so that the air and smells of these rooms do not penetrate into classrooms and other main and service rooms.

Author: Antonova O.A.

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