Anatomical and physiological features of the respiratory system in children.
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The respiratory organs in children not only have an absolutely smaller size, but, in addition, they also differ in some incomplete anatomical and histological structure. The child’s nose is relatively small, its cavities are underdeveloped, and the nasal passages are narrow; The lower nasal passage in the first months of life is completely absent or rudimentarily developed. The mucous membrane is tender, rich in blood vessels, the submucosa in the first years of life is poor in cavernous tissue; at 8-9 years old, the cavernous tissue is already quite developed, and there is especially a lot of it during puberty.
Accessory cavities The noses of young children are very poorly developed or even completely absent. Frontal sinus appears only in the 2nd year of life, by 6 years it reaches the size of a pea and is finally formed only by 15 years. Maxillary cavity, although already present in newborns, is very small and only from 2 years of age begins to noticeably increase in volume; approximately the same must be said about sinus ethmoidalis. Sinus sphenoidalis in young children is very small; up to 3 years of age, its contents are easily emptied into the nasal cavity; from the age of 6 years, this cavity begins to rapidly increase. Due to the poor development of the paranasal cavities in young children, inflammatory processes from the nasal mucosa very rarely spread to these cavities.
The nasolacrimal duct is short, its external opening is located close to the corner of the eyelids, the valves are underdeveloped, which makes it very easy for infection to enter the conjunctival sac from the nose.
The pharynx in children is relatively narrow and has a more vertical direction. Waldeyer's ring in newborns is poorly developed; pharyngeal tonsils are not noticeable when examining the pharynx and become visible only by the end of the 1st year of life; V next years On the contrary, accumulations of lymphoid tissue and tonsils hypertrophy somewhat, reaching maximum expansion most often between 5 and 10 years. During puberty, the tonsils begin to undergo reverse development, and after puberty it is relatively rare to see their hypertrophy. Enlargements of the adenoids are most pronounced in children with exudative and lymphatic diathesis; they especially often experience nasal breathing disorders, chronic catarrhal conditions of the nasopharynx, and sleep disturbances.
The larynx in children of the earliest age has a funnel-shaped shape, later - cylindrical; it is located slightly higher than in adults; its lower end in newborns is at the level of the fourth cervical vertebra (in adults, 1-12 vertebrae lower). The most vigorous growth of the transverse and anteroposterior dimensions of the larynx is observed in the 1st year of life and at the age of 14-16 years; With age, the funnel-shaped shape of the larynx gradually approaches cylindrical. The larynx in young children is relatively longer than in adults.
The cartilage of the larynx in children is delicate, very pliable, the epiglottis is relatively narrow until 12-13 years of age and in infants it can be easily seen even with a routine examination of the pharynx.
Gender differences in the larynx in boys and girls begin to emerge only after 3 years, when the angle between the plates of the thyroid cartilage in boys becomes more acute. From the age of 10, boys already have quite clearly identified features characteristic of the male larynx.
The indicated anatomical and histological features of the larynx explain the mild onset of stenotic phenomena in children, even with relatively moderate inflammatory phenomena. Hoarseness, often observed in young children after a cry, usually does not depend on inflammatory phenomena, but on the lethargy of the easily fatigued muscles of the glottis.
The trachea in newborns has a length of about 4 cm, by the age of 14-15 it reaches approximately 7 cm, and in adults it is 12 cm. In children of the first months of life, it has a somewhat funnel-shaped shape and is located higher in them than in adults; in newborns, the upper end of the trachea is at the level of the IV cervical vertebra, in adults - at the level of VII.
The bifurcation of the trachea in newborns corresponds to the III-JV thoracic vertebrae, in children 5 years old - IV - V and 12 year olds - V - VI vertebrae.
The growth of the trachea is approximately parallel to the growth of the trunk; There is an almost constant relationship between the width of the trachea and the circumference of the chest at all ages. The cross section of the trachea in children in the first months of life resembles an ellipse, in subsequent ages it resembles a circle.
The tracheal mucosa is tender, rich in blood vessels and relatively dry due to insufficient secretion of mucous glands. The muscle layer of the membranous part of the tracheal wall is well developed even in newborns; elastic tissue is found in relatively small quantities.
A child's trachea is soft and easily compressed; under the influence of inflammatory processes, stenotic phenomena easily occur. The trachea is mobile to some extent and can be displaced under the influence of unilateral pressure (exudate, tumor).
Bronchi. The right bronchus is like a continuation of the trachea, the left one extends at a large angle; This explains the more frequent entry of foreign bodies into the right bronchus. The bronchi are narrow, their cartilage is soft, muscle and elastic fibers are relatively poorly developed, the mucous membrane is rich in blood vessels, but relatively dry.
The lungs of a newborn weigh about 50 g, by 6 months their weight doubles, by one year it triples, and by 12 years it reaches 10 times its original weight;
in adults, the lungs weigh almost 20 times more than at birth. The right lung is usually slightly larger than the left. In young children, the pulmonary fissures are often weakly expressed, only in the form of shallow grooves on the surface of the lungs; especially often average share the right lung almost merges with the upper one. The large, or main, oblique fissure separates the lower lobe on the right from the upper and middle lobes, and the small horizontal fissure runs between the upper and middle lobes. There is only one slot on the left.
The differentiation of individual cellular elements must be distinguished from the growth of lung mass. The main anatomical and histological unit of the lung is the acinus, which, however, has a relatively primitive character in children under 2 years of age. From 2 to 3 years, cartilaginous muscular bronchi develop vigorously; from 6 to 7 years of age, the histostructure of the acinus basically coincides with that of an adult; The sacculi that are sometimes encountered no longer have a muscular layer. Interstitial (connective) tissue in children is loose and rich in lymphatic and blood vessels. The children's lung is poor in elastic tissue, especially around the alveoli.
The epithelium of the alveoli in non-breathing stillborns is cubic, in breathing newborns and in older children it is flat.
The differentiation of the child's lung is thus characterized by quantitative and qualitative changes: a decrease in respiratory bronchioles, the development of alveoli from the alveolar ducts, an increase in the capacity of the alveoli themselves, a gradual reverse development of intrapulmonary connective tissue layers and an increase in elastic elements.
The volume of the lungs of already breathing newborns is 70 cm3, by the age of 15 their volume increases 10 times and in adults - 20 times. The overall growth of the lungs occurs mainly due to an increase in the volume of the alveoli, while the number of the latter remains more or less constant.
The breathing surface of the lungs in children is relatively larger than in adults; The contact surface of alveolar air with the vascular pulmonary capillary system decreases relatively with age. The amount of blood flowing through the lungs per unit time is greater in children than in adults, which creates the most favorable conditions for gas exchange.
Children, especially young children, are prone to pulmonary atelectasis and hypostasis, the occurrence of which is favored by the richness of the lungs in blood and insufficient development of elastic tissue.
The mediastinum in children is relatively larger than in adults; in its upper part it contains the trachea, large bronchi, thymus gland and lymph nodes, arteries and large nerve trunks, in its lower part there are the heart, blood vessels and nerves.
The lymph nodes. The following groups of lymph nodes in the lungs are distinguished: 1) tracheal, 2) bifurcation, 3) bronchopulmonary (at the point where the bronchi enter the lungs) and 4) nodes of large vessels. These groups of lymph nodes are connected by lymphatic pathways to the lungs, mediastinal and supraclavicular nodes (Fig. 49).
Rib cage. Relatively large lungs, heart and mediastinum occupy relatively more space in the child's chest and determine some of its features. The chest is always in a state of inhalation, the thin intercostal spaces are smoothed out, and the ribs are pressed quite strongly into the lungs.
The ribs in very young children are almost perpendicular to the spine, and the increase in capacity chest due to raising the ribs is almost impossible. This explains the diaphragmatic nature of breathing at this age. In newborns and children in the first months of life, the anteroposterior and lateral diameters of the chest are almost equal, and the epigastric angle is very obtuse.
As the child ages, the cross-section of the chest takes on an oval or kidney-shaped shape.
The frontal diameter increases, the sagittal diameter decreases relatively, and the curvature of the ribs increases significantly; the epigastric angle becomes more acute.
These ratios are characterized by the thoracic index (the percentage ratio between the anteroposterior and transverse diameters of the chest): in the fetus of the early embryonic period it is 185, in a newborn - 90, by the end of the year - 80, by 8 years - 70, after puberty period, it increases slightly again and fluctuates around 72-75.
The angle between the costal arch and the medial section of the chest in a newborn is approximately 60°, by the end of the 1st year of life - 45°, at the age of 5 years - 30°, at 15 years - 20° and after the end of puberty --about 15°.
The position of the sternum also changes with age; its upper edge, lying in a newborn at the level of the VII cervical vertebra, by the age of 6-7 years descends to the level of the II-III thoracic vertebrae. The dome of the diaphragm reaches in infants top edge The fourth ribs drop slightly lower with age.
From the above it is clear that the chest in children gradually moves from the inspiratory position to the expiratory position, which is the anatomical prerequisite for the development of the thoracic (costal) type of breathing.
The structure and shape of the chest can vary significantly depending on individual characteristics child. The shape of the chest in children is especially easily affected by past diseases (rickets, pleurisy) and various negative environmental influences. Age-related anatomical features of the chest also determine some physiological characteristics breathing of children in different periods of childhood.
The first breath of a newborn. During the period of intrauterine development in the fetus, gas exchange occurs exclusively due to the placental circulation. At the end of this period, the fetus develops regular intrauterine respiratory movements, indicating the ability of the respiratory center to respond to irritation. From the moment the baby is born, gas exchange stops due to the placental circulation and pulmonary respiration begins.
The physiological causative agent of the respiratory center is a lack of oxygen and carbon dioxide, the increased accumulation of which from the moment of cessation of placental circulation is the cause of the first deep breath of the newborn; it is possible that the cause of the first breath should be considered not so much an excess of carbon dioxide in the blood of a newborn, but mainly a lack of oxygen in it.
The first breath, accompanied by the first cry, in most cases appears in the newborn immediately - as soon as the passage of the fetus through the birth canal mother. However, in cases where a child is born with a sufficient supply of oxygen in the blood or there is a slightly reduced excitability of the respiratory center, several seconds, and sometimes even minutes, pass until the first breath appears. This short-term holding of breath is called neonatal apnea.
After the first deep breath, healthy children establish correct and mostly fairly uniform breathing; The uneven breathing rhythm observed in some cases during the first hours and even days of a child’s life usually quickly levels out.
The respiratory rate in newborns is about 40-60 per minute; With age, breathing becomes more rare, gradually approaching the rhythm of an adult. According to our observations, the respiratory rate in children is as follows.
Children's age
Until the age of 8, boys breathe more frequently than girls; In the prepubertal period, girls are ahead of boys in breathing frequency, and in all subsequent years their breathing remains more frequent.
Children are characterized by mild excitability of the respiratory center: mild physical stress and mental arousal, slight increases in body temperature and ambient air almost always cause a significant increase in breathing, and sometimes some disruption of the correct respiratory rhythm.
On average, one respiratory movement in newborns accounts for 2"/2 -3 pulse beats, in children at the end of the 1st year of life and older - 3--4 beats, and, finally, in adults - 4--5 heart beats. contractions These ratios are usually maintained when the pulse and breathing increase under the influence of physical and mental stress.
Breath volume. To assess the functional capacity of the respiratory organs, the volume of one respiratory movement, minute volume of breathing and vital capacity of the lungs are usually taken into account.
The volume of each respiratory movement in a newborn is able to good sleep equal on average to 20 cm3,y one month old baby it rises to approximately 25 cm3, by the end of the year reaches 80 cm3, by 5 years - about 150 cm3, by 12 years - on average about 250 cm3, and by 14-16 years it rises to 300-400 cm3; however, this value, apparently, can fluctuate within fairly wide individual limits, since the data of different authors differ greatly. When screaming, the volume of breathing increases sharply - 2-3 or even 5 times.
The minute volume of breathing (the volume of one breath multiplied by the number of respiratory movements) quickly increases with age and is approximately equal to 800-900 cm3 in a newborn, 1400 cm3 in a child aged 1 month, and about 2600 cm3 by the end of the 1st year. , at the age of 5 years - about 3200 cm3 and at 12-15 years - about 5000 cm3.
The vital capacity of the lungs, i.e. the amount of air maximally exhaled after maximal inhalation, can only be indicated for children starting from 5-6 years old, since the research methodology itself requires the active participation of the child; at 5--6 years old, the vital capacity fluctuates around 1150 cm3, at 9--10 years old - about 1600 cm3 and at 14--16 years old - 3200 cm3. Boys have a larger lung capacity than Girls; The greatest lung capacity occurs with thoracoabdominal breathing, the smallest with purely chest breathing.
The type of breathing varies depending on the age and gender of the child; in children of the newborn period predominates diaphragmatic breathing with minor participation of the costal muscles. In infants, so-called thoracic-abdominal breathing with a predominance of diaphragmatic breathing is detected; excursions of the chest are weakly expressed in its upper parts and, conversely, much stronger in the lower departments With the child's transition from permanent horizontal position in the vertical the type of breathing also changes; at this age (beginning of the 2nd year of life) it is characterized by a combination of diaphragmatic and chest breathing, and in some cases one predominates, in others the other. At the age of 3-7 years, due to the development of the muscles of the shoulder girdle, thoracic breathing becomes more and more clearly visible, beginning to definitely dominate over diaphragmatic breathing.
The first differences in the type of breathing depending on gender begin to clearly appear at the age of 7-14 years; During the prepubertal and pubertal periods, boys develop mainly the abdominal type, and girls develop the thoracic type of breathing. Age-related changes in breathing type are predetermined by the above anatomical features chest of children at different periods of life.
Increasing the capacity of the chest by raising the ribs in infants is almost impossible due to the horizontal position of the ribs; it becomes possible in more later periods when the ribs drop slightly downwards and anteriorly and when they are raised, the anterior-posterior and lateral dimensions of the chest increase.
Features of breathing regulation
As is known, the act of breathing is regulated by the respiratory center, the activity of which is characterized by automaticity and rhythm. The respiratory center is located in middle third medulla oblongata on both sides of the midline. Excitation, rhythmically arising in the cells of the respiratory center, along centrifugal (efferent) nerve pathways transmitted to the respiratory muscles. Various irritations affecting the extero- and interoreceptors of the human body travel through centripetal pathways to the respiratory center and affect the processes of excitation and inhibition that occur in it; The role of impulses coming from the lungs themselves is especially great when irritating numerous receptors located in the bronchioles and alveoli;
the excitation that occurs during inhalation in these interoceptors is transmitted along the fibers of the vagus nerve to the respiratory center and inhibits its activity; the inhibited center does not send exciting impulses to the respiratory muscles, and they relax, and the exhalation phase begins; in a collapsed lung, the afferent endings of the vagus nerve are not excited, therefore, the inhibitory influence coming through its fibers is eliminated, the respiratory center is excited again, the resulting impulses are sent to the respiratory muscles and a new breath occurs; self-regulation occurs: inhalation causes exhalation, and the latter causes inhalation. Of course, the composition of the alveolar air also plays a role.
Consequently, the regulation of breathing in children is carried out mainly by the neuro-reflex pathway. Irritation of the endings of the centripetal nerves of the skin, muscles, vascular reflexogenic zones, endings of the sinocarotid nerve, etc., in the same reflex way, affects the rhythm and depth of breathing. The composition of the blood, the content of oxygen and carbon dioxide in it, the reaction of the blood, the accumulation of lactic acid or various pathological metabolic products in it also affect the function of the respiratory center; these irritations can be transmitted to it as a result of the influence of the blood composition on the receptors embedded in the walls of the vessels themselves, as well as as a result of direct impact on the respiratory center of the composition of the blood washing it (humoral influence).
The function of the respiratory center of the medulla oblongata is constantly regulated by the cerebral cortex. The rhythm of breathing and its depth change under the influence of various emotional moments; an adult and older children can voluntarily change both the depth and frequency of breathing and can hold it for some time. Experiments on animals and observations in humans have proven the possibility of conditioned reflex effects on breathing. All this speaks to the regulatory role of the cerebral cortex. In very young children, it is often necessary to observe disturbances in the rhythm of breathing, even short-term complete cessation of breathing, for example in premature infants, which must be explained by the morphological immaturity of their central and peripheral nervous systems and, in particular, the cerebral cortex. A slight disturbance in the rhythm of breathing during sleep and in older children must be explained by the unique relationship between the cortex and the subcortical region of the brain.
The regulatory role of the central nervous system ensures the integrity of the body and explains the dependence of breathing on the function of other organs - the circulatory system, digestion, blood system, metabolic processes, etc. The close dependence of the function of some organs on the function of others is especially clearly reflected in children with less perfect regulation of cortico-visceral connections.
Protective reflexes from the mucous membranes of the respiratory tract - sneezing and coughing - are expressed, although less clearly, already in children of the newborn period.
The formation of the tracheopulmonary system begins at 3-4 weeks embryonic development. Already by the 5th-6th week of embryo development, second-order branches appear and the formation of three lobes of the right lung and two lobes of the left lung is predetermined. During this period, the trunk of the pulmonary artery is formed, growing into the lungs along the primary bronchi.
In the embryo, at the 6-8th week of development, the main arterial and venous collectors of the lungs are formed. Within 3 months, the bronchial tree grows, segmental and subsegmental bronchi appear.
During the 11-12th week of development, areas of lung tissue are already present. They, together with the segmental bronchi, arteries and veins, form the embryonic segments of the lungs.
Between the 4th and 6th months, rapid growth of the pulmonary vascular system is observed.
In fetuses at 7 months, the lung tissue acquires the features of a porous canal structure; the future air spaces are filled with fluid, which is secreted by the cells lining the bronchi.
At 8-9 months of the intrauterine period, further development occurs functional units lungs.
The birth of a child requires the immediate functioning of the lungs; during this period, with the onset of breathing, significant changes occur in the airways, especially the respiratory part of the lungs. The formation of the respiratory surface in individual parts of the lungs occurs unevenly. For directing the respiratory apparatus of the lungs great value have the condition and readiness of the surfactant film lining the lung surface. Violation of the surface tension of the surfactant system leads to serious illnesses in young children.
In the first months of life, the child maintains the ratio of the length and width of the airways, like a fetus, when the trachea and bronchi are shorter and wider than in adults, and the small bronchi are narrower.
The pleura covering the lungs in a newborn baby is thicker, looser, contains villi and outgrowths, especially in the interlobar grooves. Pathological foci appear in these areas. Before the birth of a child, the lungs are prepared to perform the respiratory function, but individual components are in the development stage, the formation and maturation of the alveoli is rapidly proceeding, the small lumen of the muscular arteries is being reconstructed and the barrier function is being eliminated.
After three months of age, period II is distinguished.
- period of intensive growth of the pulmonary lobes (from 3 months to 3 years).
- final differentiation of the entire bronchopulmonary system (from 3 to 7 years).
Intensive growth of the trachea and bronchi occurs in the 1st–2nd year of life, which slows down in subsequent years, and the small bronchi grow intensively, and the branching angles of the bronchi also increase. The diameter of the alveoli increases, and the respiratory surface of the lungs doubles with age. In children under 8 months, the diameter of the alveoli is 0.06 mm, in 2 years - 0.12 mm, in 6 years - 0.2 mm, in 12 years - 0.25 mm.
In the first years of life, growth and differentiation of elements occur lung tissue, vessels. The ratio of the volumes of shares in individual segments is equalized. Already at 6-7 years of age, the lungs are a fully formed organ and are indistinguishable from the lungs of adults.
Features of the child's respiratory tract
The respiratory tract is divided into upper, which includes the nose, paranasal sinuses, pharynx, Eustachian tubes, and lower, which includes the larynx, trachea, bronchi.
The main function of breathing is to conduct air into the lungs, cleanse it of dust particles, protect the lungs from harmful effects bacteria, viruses, foreign particles. In addition, the airways warm and humidify the inhaled air.
The lungs are represented by small sacs that contain air. They connect with each other. The main function of the lungs is to absorb oxygen from the atmospheric air and release gases into the atmosphere, primarily acid coal.
Breathing mechanism. When inhaling, the diaphragm and chest muscles contract. Exhalation in older age occurs passively under the influence of elastic traction of the lungs. With bronchial obstruction, emphysema, and also in newborns, active inhalation occurs.
Normally, breathing is established at a frequency at which the volume of breathing is performed due to the minimum energy expenditure of the respiratory muscles. In newborn children, the respiratory rate is 30-40, in adults - 16-20 per minute.
The main carrier of oxygen is hemoglobin. In the pulmonary capillaries, oxygen binds to hemoglobin, forming oxyhemoglobin. In newborns, fetal hemoglobin predominates. On the first day of life, it is contained in the body about 70%, by the end of the 2nd week - 50%. Fetal hemoglobin has the ability to easily bind oxygen and difficult to release it to tissues. This helps the child in the presence of oxygen starvation.
Transport of carbon dioxide occurs in dissolved form; blood saturation with oxygen affects the content of carbon dioxide.
The respiratory function is closely related to the pulmonary circulation. This is a complex process.
During breathing, autoregulation is noted. When the lung stretches during inhalation, the inhalation center is inhibited, and exhalation is stimulated during exhalation. Deep breathing or forced inflation of the lungs leads to a reflex expansion of the bronchi and increases the tone of the respiratory muscles. When the lungs collapse and are compressed, the bronchi become narrowed.
IN medulla oblongata The respiratory center is located, from where commands to the respiratory muscles come. The bronchi lengthen when you inhale, and shorten and narrow when you exhale.
The relationship between the functions of breathing and blood circulation appears from the moment the lungs expand during the first breath of a newborn, when both the alveoli and blood vessels expand.
Respiratory diseases in children may cause problems respiratory function and respiratory failure.
Features of the structure of a child's nose
In young children, the nasal passages are short, the nose is flattened due to an insufficiently developed facial skeleton. The nasal passages are narrower, the conchae are thickened. The nasal passages are fully formed only by the age of 4 years. The nasal cavity is relatively small in size. The mucous membrane is very loose and well supplied with blood vessels. The inflammatory process leads to the development of edema and, as a result, a reduction in the lumen of the nasal passages. Mucus often stagnates in the nasal passages. It can dry out, forming crusts.
When the nasal passages close, shortness of breath may occur; during this period, the child cannot suckle at the breast, becomes anxious, abandons the breast, and remains hungry. Children, due to difficulty in nasal breathing, begin to breathe through their mouths, their warming of the incoming air is disrupted and their susceptibility to colds increases.
If nasal breathing is impaired, there is a lack of discrimination of odors. This leads to a disturbance in appetite, as well as a disturbance in the understanding of the external environment. Breathing through the nose is physiological, breathing through the mouth is a sign of nasal disease.
Accessory nasal cavities. The paranasal cavities, or sinuses, as they are called, are limited spaces filled with air. The maxillary (maxillary) sinuses are formed by the age of 7. Ethmoidal - by the age of 12, the frontal is fully formed by the age of 19.
Features of the nasolacrimal duct. The nasolacrimal duct is shorter than in adults, its valves are not sufficiently developed, and the outlet is located close to the corner of the eyelids. Due to these features, the infection quickly spreads from the nose to the conjunctival sac.
Features of the pharynxchild
The pharynx in young children is relatively wide, the palatine tonsils are poorly developed, which explains the rare cases of sore throat in the first year of life. The tonsils are fully developed by the age of 4-5 years. By the end of the first year of life, almond tissue hyperplasias. But its barrier function at this age is very low. Overgrown almond tissue can be susceptible to infection, which is why diseases such as tonsillitis and adenoiditis occur.
The Eustachian tubes open into the nasopharynx and connect it to the middle ear. If an infection enters the middle ear from the nasopharynx, middle ear inflammation occurs.
Features of the larynxchild
The larynx in children is funnel-shaped and is an extension of the pharynx. In children, it is located higher than in adults, and has a narrowing in the area of the cricoid cartilage, where the subglottic space is located. The glottis is formed by the vocal cords. They are short and thin, this is the reason for the child’s high, sonorous voice. The diameter of the larynx in a newborn in the area of the subglottic space is 4 mm, at 5-7 years old - 6-7 mm, by 14 years old - 1 cm. Features of the larynx in children are: its narrow lumen, many nerve receptors, easily occurring swelling of the submucosal layer, which can lead to severe disorders breathing.
The thyroid cartilages form a more acute angle in boys over 3 years of age; from the age of 10, a typical male larynx is formed.
Features of the tracheachild
The trachea is a continuation of the larynx. It is wide and short, the tracheal frame consists of 14-16 cartilaginous rings, which are connected by a fibrous membrane instead of an elastic end plate in adults. Presence in the membrane large coli quality muscle fibers contributes to changes in its lumen.
Anatomically, the trachea of a newborn is located at the level of the IV cervical vertebra, and in an adult - at the level of the VI-VII cervical vertebra. In children, it gradually descends, as does its bifurcation, which is located on the newborn's level III thoracic vertebra, in children 12 years old - at the level of the V-VI thoracic vertebra.
In progress physiological breathing the lumen of the trachea changes. During coughing, it decreases by 1/3 of its transverse and longitudinal dimensions. The mucous membrane of the trachea is rich in glands that secrete a secretion that covers the surface of the trachea with a layer 5 microns thick.
The ciliated epithelium promotes the movement of mucus at a speed of 10-15 mm/min from the inside to the outside.
Features of the trachea in children contribute to the development of its inflammation - tracheitis, which is accompanied by a rough, low-timbre cough, reminiscent of a cough “like in a barrel”.
Features of the child's bronchial tree
The bronchi in children are formed at birth. Their mucous membrane is richly supplied with blood vessels and is covered with a layer of mucus, which moves at a speed of 0.25-1 cm/min. A feature of the bronchi in children is that elastic and muscle fibers are poorly developed.
The bronchial tree branches to the bronchi of the 21st order. With age, the number of branches and their distribution remain constant. The size of the bronchi changes rapidly in the first year of life and during puberty. They are based on cartilaginous semirings in early childhood. Bronchial cartilage is very elastic, pliable, soft and easily displaced. The right bronchus is wider than the left and is a continuation of the trachea, so foreign bodies are more often found in it.
After the birth of a child, a columnar epithelium with a ciliated apparatus is formed in the bronchi. With hyperemia of the bronchi and their swelling, their lumen sharply decreases (up to its complete closure).
Underdevelopment of the respiratory muscles contributes to a weak cough impulse in small child, which can lead to blockage of small bronchi with mucus, and this, in turn, leads to infection of the lung tissue and disruption of the cleansing drainage function of the bronchi.
With age, as the bronchi grow, wide lumens of the bronchi appear, and the bronchial glands produce less viscous secretions, acute diseases of the bronchopulmonary system are less common compared to children of younger ages.
Features of the lungsin children
The lungs in children, as in adults, are divided into lobes, and lobes into segments. The lungs have a lobular structure, the segments in the lungs are separated from each other by narrow grooves and partitions of connective tissue. The main structural unit is the alveoli. Their number in a newborn is 3 times less than in an adult. Alveoli begin to develop from 4-6 weeks of age, their formation occurs up to 8 years. After 8 years, children’s lungs increase due to their linear size, and at the same time, the respiratory surface of the lungs increases.
The following periods can be distinguished in the development of the lungs:
1) from birth to 2 years, when intensive growth of the alveoli occurs;
2) from 2 to 5 years, when elastic tissue intensively develops, bronchi with peribronchial inclusions of lung tissue are formed;
3) from 5 to 7 years, the functional abilities of the lungs are finally formed;
4) from 7 to 12 years, when a further increase in lung mass occurs due to the maturation of lung tissue.
Anatomically right lung consists of three lobes (upper, middle and lower). By 2 years, the sizes of the individual lobes correspond to each other, like in an adult.
In addition to the lobar division, segmental division is distinguished in the lungs, in right lung There are 10 segments, 9 on the left.
The main function of the lungs is breathing. It is believed that 10,000 liters of air pass through the lungs daily. Oxygen absorbed from the inhaled air ensures the functioning of many organs and systems; the lungs take part in all types of metabolism.
The respiratory function of the lungs is carried out with the help of a biologically active substance - surfactant, which also has bactericidal effect, preventing fluid from entering the pulmonary alveoli.
The lungs remove waste gases from the body.
A feature of the lungs in children is the immaturity of the alveoli; they have a small volume. This is compensated by increased breathing: the younger the child, the more shallow his breathing. The respiratory rate in a newborn is 60, in a teenager it is already 16-18 respiratory movements per minute. Lung development is completed by age 20.
A wide variety of diseases can impair life expectancy in children. important function breathing. Due to the characteristics of aeration, drainage function and evacuation of secretions from the lungs, the inflammatory process is often localized in the lower lobe. This occurs in a supine state in infants due to insufficient drainage function. Paravisceral pneumonia most often occurs in the second segment of the upper lobe, as well as in the basal-posterior segment of the lower lobe. The middle lobe of the right lung may often be affected.
Greatest diagnostic value have the following studies: x-ray, bronchological, determination gas composition blood, blood pH, study of external respiration function, study of bronchial secretions, computed tomography.
By the frequency of breathing and its relationship with the pulse, the presence or absence of respiratory failure is judged (see Table 14).
All airways in a child are significantly smaller and have narrower openings than in an adult. The structural features of children in the first years of life are the following: 1) thin, easily wounded, dry mucosa with underdevelopment of glands, reduced production of immunoglobulin A and insufficiency of surfactant; 2) rich vascularization of the submucosal layer, represented by loose fiber and containing few elastic elements; 3) softness and pliability of the cartilaginous frame of the lower respiratory tract, the absence of elastic tissue in them.
Nose and nasopharyngeal space small in size, the nasal cavity is low and narrow due to insufficient development of the facial skeleton. The shells are thick, the nasal passages are narrow, the lower one is formed only by 4 years. Cavernous tissue develops by 8–9 years of age, so nosebleeds in young children are rare and are caused by pathological conditions.
Paranasal sinuses only the maxillary sinuses are formed; The frontal and ethmoid are open protrusions of the mucous membrane, taking shape in the form of cavities only after 2 years; the main sinus is absent. All paranasal sinuses develop completely by the ages of 12-15, however, sinusitis can also develop in children in the first two years of life.
Nasolacrimal duct. Short, its valves are underdeveloped, the outlet is located close to the corner of the eyelids.
Pharynx relatively wide, the palatine tonsils are clearly visible at birth, their crypts and vessels are poorly developed, which explains the rare diseases of sore throat in the first year of life. By the end of the first year, the lymphoid tissue of the tonsils often hyperplasias, especially in children with diathesis. Their barrier function at this age is low, like that of lymph nodes.
Epiglottis. In newborns it is relatively short and wide. The incorrect position and softness of its cartilage can cause a functional narrowing of the entrance to the larynx and the appearance of noisy (stridor) breathing.
Larynx is higher than in adults, lowers with age, and is very mobile. Its position is not constant even in the same patient. It has a funnel-shaped shape with a distinct narrowing in the area of the subglottic space, limited by the rigid cricoid cartilage. The diameter of the larynx in this place in a newborn is only 4 mm and increases slowly (6 - 7 mm at 5 - 7 years, 1 cm by 14 years), its expansion is impossible. The thyroid cartilages form an obtuse angle in young children, which becomes sharper in boys after 3 years of age. From the age of 10, the male larynx is formed. The true vocal cords in children are shorter, which explains the pitch and timbre of the child's voice.
Trachea. In children in the first months of life, the trachea is often funnel-shaped; at older ages, cylindrical and conical shapes predominate. Its upper end is located in newborns much higher than in adults (at the level of the IV and VI cervical vertebrae, respectively), and gradually descends, like the level of the tracheal bifurcation (from the III thoracic vertebra in a newborn to V-VI at 12 - 14 years). The tracheal framework consists of 14-16 cartilaginous half-rings connected posteriorly by a fibrous membrane (instead of an elastic end plate in adults). The child’s trachea is very mobile, which, along with the changing lumen and softness of the cartilage, sometimes leads to a slit-like collapse during exhalation (collapse) and is the cause of expiratory shortness of breath or rough snoring breathing (congenital stridor). Symptoms of stridor usually disappear by age 2 as the cartilage becomes denser.
Bronchial tree formed at birth. The number of branches does not change with growth. They are based on cartilaginous semirings that do not have a closing elastic plate, connected by a fibrous membrane. The cartilage of the bronchi is very elastic, soft, springy and easily displaced. The right main bronchus is usually an almost direct continuation of the trachea, therefore it is in it that they are most often found foreign bodies. The bronchi and trachea are lined with columnar epithelium, the ciliated apparatus of which is formed after the birth of the child. Bronchial motility is insufficient due to underdevelopment of muscles and ciliated epithelium. Incomplete myelination of the vagus nerve and underdevelopment of the respiratory muscles contribute to the weakness of the cough impulse in a small child.
Lungs have a segmental structure. The structural unit is the acinus, but the terminal bronchioles do not end in a cluster of alveoli, as in an adult, but in a sac. New alveoli are gradually formed from the “lace” edges of the latter, the number of which in a newborn is 3 times less than in an adult. The diameter of each alveoli also increases (0.05 mm in a newborn, 0.12 mm at 4-5 years, 0.17 mm at 15 years). At the same time, the vital capacity of the lungs increases. The interstitial tissue in a child's lung is loose, rich in blood vessels, fiber, and contains very little connective tissue and elastic fibers. In this regard, the lungs of a child in the first years of life are more full-blooded and less airy than those of an adult. Underdevelopment of the elastic framework of the lungs contributes to both the occurrence of emphysema and atelectasis of the lung tissue. The tendency to atelectasis increases due to surfactant deficiency. It is this deficiency that leads to insufficient expansion of the lungs in premature infants after birth (physiological atelectasis), and also underlies the respiratory distress syndrome, clinically manifested by severe DN.
Pleural cavity easily extensible due to weak attachment of parietal layers. The visceral pleura, especially relatively thick, loose, folded, contains villi, most pronounced in the sinuses and interlobar grooves. In these areas there are conditions for faster emergence of infectious foci.
Root of the lung. Consists of large bronchi, vessels and lymph nodes. The root is integral part mediastinum. The latter is characterized by easy displacement and is often the site of development of inflammatory foci.
Diaphragm. Due to the characteristics of the chest, the diaphragm plays a large role in the breathing mechanism of a small child, ensuring the depth of inspiration. The weakness of its contractions explains the shallow breathing of the newborn.
Main functional features: 1) the depth of breathing, the absolute and relative volumes of the respiratory act are significantly less than in an adult. When screaming, the volume of breathing increases 2 to 5 times. The absolute value of the minute volume of respiration is less than that of an adult, and the relative value (per 1 kg of body weight) is much greater;
2) the respiratory rate increases, the younger the child. It compensates for the small volume of the respiratory act. Rhythm instability and short apneas in newborns are associated with incomplete differentiation of the respiratory center;
3) gas exchange is carried out more vigorously than in adults, due to the rich vascularization of the lungs, blood flow speed, and high diffusion capacity. At the same time, the function of external respiration is disrupted very quickly due to insufficient excursions of the lungs and straightening of the alveoli. Tissue respiration occurs at higher energy costs than in adults and is easily disrupted with the formation of metabolic acidosis due to the instability of enzyme systems.
The respiratory system consists of airways and a gas exchange apparatus. The upper respiratory tract includes the nasal cavity, pharynx and larynx, and the lower respiratory tract includes the trachea and bronchi. Gas exchange between atmospheric air and blood occurs in the lungs. The respiratory organs are morphologically imperfect at the time of the child. During the first years of life, they grow and differentiate rapidly. By the age of 7, the formation of the respiratory organs ends and in the future there is only an increase in their size. Features of the morphological structure of the respiratory organs are: 1) thin, easily wounded mucosa; 2) underdeveloped glands; 3) reduced production of immunoglobulin A and surfactant; 4) a submucosal layer rich in capillaries, consisting mainly of loose fiber; 5) soft, pliable cartilaginous frame of the lower respiratory tract; 6) insufficient amount of elastic tissue in the respiratory tract and lungs. Nasal cavity. The nose in children of the first three years of life is small, its cavities are underdeveloped, the nasal passages are narrow, and the turbinates are thick. The lower nasal meatus is absent. It is formed by the age of 4. When young children have a runny nose, swelling of the mucous membrane easily occurs, which leads to obstruction of the nasal passages, makes it difficult to suck the breast, and causes shortness of breath. The cavernous tissue of the nasal submucosa is underdeveloped, which explains rare nosebleeds. The paranasal sinuses are not formed at the time of birth. The nasolacrimal duct is wide, which allows infection to penetrate from the nose into the conjunctival sac. Pharynx. In young children it is relatively narrow and small. Eustachian tube. Short and wide, located more horizontally than in older children, its opening is closer to the choanae. This predisposes to easier infection of the tympanic cavity with rhinitis. Epiglottis. In a newborn, it is soft and bends easily, losing the ability to hermetically cover the entrance to the trachea. This partly explains the great danger of aspiration of stomach contents into the respiratory tract during vomiting and regurgitation. Incorrect position and softness of the epiglottis cartilage can cause functional narrowing of the entrance to the larynx and the appearance of noisy (stridorous) breathing. Larynx. It is located higher than in adults, so the child, lying on his back, can swallow liquid food. The larynx has a funnel shape. In the area of the subglottic space there is a clearly pronounced narrowing. The diameter of the larynx in this place in a newborn is only 4 mm and increases slowly with age; by the age of 14 it is 1 cm. Narrow lumen of the larynx, easily occurring swelling of the submucosal layer, spasm smooth muscle due to the abundance of nerve receptors in the subglottic space, they can lead to stenosis (narrowing) of the larynx during a respiratory infection. Trachea. In a newborn child, it is relatively wide, supported by open cartilaginous rings and a wide muscle membrane. Contraction and relaxation of muscle fibers change its lumen. The trachea is very mobile, which, along with the changing lumen and softness of the cartilage, leads to its collapse at the exit and is the cause of expiratory shortness of breath or rough wheezing breathing (congenital stridor). Symptoms of stridor disappear by age two, when the cartilage becomes denser. Bronchial tree. By the time the child is born, it is formed. The bronchi are narrow, their cartilage is soft and pliable, since the basis of the bronchi, like the trachea, is made up of half rings connected by a fibrous film. In young children, the angle of departure of both bronchi from the trachea is the same and foreign bodies can enter both the right and left bronchus. With age, the angle changes; foreign bodies are more often found in the right bronchus, since it is like a continuation of the trachea. In young years bronchial tree does not perform the cleaning function sufficiently. Self-cleaning mechanisms - wave-like movements of the ciliated epithelium of the bronchial mucosa, peristalsis of bronchioles, cough reflex - are much less developed than in adults. Hyperemia and swelling of the mucous membrane, accumulation of infected mucus significantly narrow the lumen of the bronchi until they are completely blocked, which contributes to the development of atelectasis and infection of the lung tissue. Spasm easily develops in the small bronchi, which explains the frequency bronchial asthma and the asthmatic component for bronchitis and pneumonia in childhood. Lungs. In a newborn baby, the lungs are not fully formed. The terminal bronchioles do not end in a cluster of alveoli, as in an adult, but in a sac, from the edges of which new alveoli are formed. The number of alveoli and their diameter increase with age. The vital capacity of the lungs also increases. The interstitial tissue in the lung is loose, contains very little connective tissue and elastic fibers, and is rich in fiber and blood vessels. In this regard, the lungs of a young child are more full-blooded and less airy than those of an adult. The poverty of elastic fibers contributes to the ease of emphysema and atelectasis of lung tissue. The tendency to atelectasis increases due to surfactant deficiency. A surfactant is a surfactant that coats a thin film inner surface alveoli It prevents them from collapsing as you exhale. With surfactant deficiency, the alveoli do not expand and develop enough respiratory failure. Atelectasis most often occurs in the posterior regions of the lungs due to their poor ventilation. The development of atelectasis and ease of infection of the lung tissue is facilitated by blood stagnation as a result of the forced horizontal position of the infant. The lung parenchyma in young children can rupture with a relatively small increase in air pressure in the respiratory tract. This can occur if the technique of artificial ventilation is violated. K o r e n l e g k o g consists of large bronchi, vessels and lymph nodes. Lymph nodes react to the introduction of infection. Pleura well supplied with blood and lymphatic vessels, relatively thick, easily extensible. The parietal layer of the pleura is weakly fixed. Accumulation of fluid in pleural cavity causes displacement of the mediastinal organs. Thorax, diaphragm and mediastinum. The diaphragm is located high. Its contractions increase vertical size chest cavity. Ventilation of the lungs is worsened by conditions that impede the movement of the diaphragm (flatulence, increase in the size of parenchymal organs). The compliance of the child's chest can lead to paradoxical retraction of the intercostal spaces during breathing. At different periods of life, breathing has its own characteristics: 1) shallow and frequent breathing. The younger the child, the higher the respiratory rate. Largest number respirations are noted after birth - 40-60 per 1 minute, which is sometimes called “physiological shortness of breath” of a newborn. In children 1-2 years old, the respiratory rate is 30-35, in 5-6 years old it is about 25, in 10 years old it is 18-20, in adults it is 15-16. The ratio of respiratory rate to pulse rate in newborns is 1: 2.5-3; in children of other ages 1: 3.5-4; in adults 1: 4; 2) respiratory arrhythmia in the first 2-3 weeks of a newborn’s life. It manifests itself as an incorrect alternation of pauses between inhalation and exhalation. The inhalation is much shorter than the exhalation. Sometimes breathing is intermittent. This is due to the imperfection of the function of the respiratory center; 3) the type of breathing depends on age and gender. At an early age, the abdominal (diaphragmatic) type of breathing is noted; at 3-4 years, chest breathing begins to predominate over diaphragmatic breathing. Differences in breathing depending on gender are detected from 7-14 years. During puberty, boys develop abdominal breathing, and girls develop thoracic breathing. To study respiratory function, the respiratory rate is determined at rest and during physical activity; measure the size of the chest and its mobility (at rest, during inhalation and exhalation), determine the gas composition and acid-base state of the blood. Children over 5 years of age undergo spirometry. Anatomical and physiological features respiratory system, imperfect immunity, presence concomitant diseases, influence of factors external environment explain the frequency and severity of respiratory diseases in children.
ANATOMICAL AND PHYSIOLOGICAL FEATURES OF THE RESPIRATORY SYSTEM
The formation of the tracheopulmonary system begins at the 3-4th week of embryonic development. Already by the 5-6th week of embryo development, second-order branches appear and the formation of three lobes of the right lung and two lobes of the left lung is predetermined. During this period, the trunk of the pulmonary artery is formed, growing into the lungs along the primary bronchi.
In the embryo, at the 6-8th week of development, the main arterial and venous collectors of the lungs are formed. Within 3 months, the bronchial tree grows, segmental and subsegmental bronchi appear.
During the 11-12th week of development, areas of lung tissue are already present. They, together with the segmental bronchi, arteries and veins, form the embryonic segments of the lungs.
Between the 4th and 6th months, rapid growth of the pulmonary vascular system is observed.
In fetuses at 7 months, the lung tissue acquires the features of a porous canal structure; the future air spaces are filled with fluid, which is secreted by the cells lining the bronchi.
At 8–9 months of the intrauterine period, further development of the functional units of the lungs occurs.
The birth of a child requires the immediate functioning of the lungs; during this period, with the onset of breathing, significant changes occur in the airways, especially the respiratory part of the lungs. The formation of the respiratory surface in individual parts of the lungs occurs unevenly. For the expansion of the respiratory apparatus of the lungs, the condition and readiness of the surfactant film lining the lung surface are of great importance. Violation of the surface tension of the surfactant system leads to serious illnesses young child.
In the first months of life, the child maintains the ratio of the length and width of the airways, like a fetus, when the trachea and bronchi are shorter and wider than in adults, and the small bronchi are narrower.
The pleura covering the lungs in a newborn baby is thicker, looser, contains villi and outgrowths, especially in the interlobar grooves. Pathological foci appear in these areas. Before the birth of a child, the lungs are prepared to perform the respiratory function, but individual components are at the stage of development, the formation and maturation of the alveoli is rapidly proceeding, the small lumen of the muscular arteries is being reconstructed and the barrier function is being eliminated.
After three months of age, period II is distinguished.
I – period of intensive growth of the pulmonary lobes (from 3 months to 3 years).
II – final differentiation of the entire bronchopulmonary system (from 3 to 7 years).
Intensive growth of the trachea and bronchi occurs in the 1st-2nd year of life, which slows down in subsequent years, and small bronchi grow intensively, and the branching angles of the bronchi also increase. The diameter of the alveoli increases, and the respiratory surface of the lungs doubles with age. In children under 8 months, the diameter of the alveoli is 0.06 mm, in 2 years – 0.12 mm, in 6 years – 0.2 mm, in 12 years – 0.25 mm.
In the first years of life, growth and differentiation of lung tissue elements and blood vessels occur. The ratio of share volumes of individual segments is equalized. Already at 6–7 years of age, the lungs are a mature organ and are indistinguishable from the lungs of adults.
FEATURES OF THE RESPIRATORY TRACT
The respiratory tract is divided into the upper, which includes the nose, paranasal sinuses, pharynx, and Eustachian tubes, and the lower, which includes the larynx, trachea, and bronchi.
The main function of breathing is to conduct air into the lungs, cleanse it of dust particles, and protect the lungs from the harmful effects of bacteria, viruses, and foreign particles. In addition, the airways warm and humidify the inhaled air.
The lungs are represented by small sacs that contain air. They connect with each other. The main function of the lungs is to absorb oxygen from the atmospheric air and release gases, primarily carbon dioxide, into the atmosphere.
Breathing mechanism. When you inhale, the diaphragm and chest muscles contract. Exhalation in older age occurs passively under the influence of elastic traction of the lungs. With bronchial obstruction, emphysema, and also in newborns, active inhalation occurs.
Normally, breathing is established at a frequency at which the volume of breathing is performed due to the minimum energy expenditure of the respiratory muscles. In newborn children, the respiratory rate is 30–40, in adults – 16–20 per minute.
The main carrier of oxygen is hemoglobin. In the pulmonary capillaries, oxygen binds to hemoglobin to form oxyhemoglobin. In newborns, fetal hemoglobin predominates. On the first day of life, it is contained in the body about 70%, by the end of the 2nd week - 50%. Fetal hemoglobin has the ability to easily bind oxygen and difficult to release it to tissues. This helps the child in the presence of oxygen starvation.
Transport of carbon dioxide occurs in dissolved form; blood oxygen saturation affects the carbon dioxide content.
The respiratory function is closely related to pulmonary circulation. This is a complex process.
During breathing, autoregulation is noted. When the lung is stretched during inhalation, the inhalation center is inhibited, while exhalation is stimulated during exhalation. Deep breathing or forced inflation of the lungs leads to a reflex expansion of the bronchi and increases the tone of the respiratory muscles. When the lungs collapse and are compressed, the bronchi become narrowed.
The medulla oblongata contains the respiratory center, from where commands are sent to the respiratory muscles. The bronchi lengthen when you inhale, and shorten and narrow when you exhale.
The relationship between the functions of breathing and blood circulation manifests itself from the moment the lungs expand during the first breath of a newborn, when both the alveoli and blood vessels expand.
With respiratory diseases in children, respiratory dysfunction and respiratory failure may occur.
STRUCTURE FEATURES OF THE NOSE
In young children, the nasal passages are short, the nose is flattened due to an underdeveloped facial skeleton. The nasal passages are narrower, the conchae are thickened. The nasal passages are fully formed only by the age of 4 years. The nasal cavity is relatively small in size. The mucous membrane is very loose and well supplied with blood vessels. The inflammatory process leads to the development of edema and, as a result, a reduction in the lumen of the nasal passages. Mucus often stagnates in the nasal passages. It can dry out, forming crusts.
When the nasal passages close, shortness of breath may occur; during this period, the child cannot suckle, becomes anxious, abandons the breast, and remains hungry. Children, due to difficulty in nasal breathing, begin to breathe through their mouths, their warming of incoming air is disrupted and their susceptibility to colds increases.
If nasal breathing is impaired, there is a lack of discrimination of odors. This leads to a disturbance in appetite, as well as a disturbance in the understanding of the external environment. Breathing through the nose is physiological, breathing through the mouth is a sign of nasal disease.
Accessory nasal cavities. The paranasal cavities, or sinuses as they are called, are confined spaces filled with air. The maxillary (maxillary) sinuses are formed by the age of 7. Ethmoidal - by the age of 12, the frontal is fully formed by the age of 19.
Features of the nasolacrimal canal. The nasolacrimal duct is shorter than in adults, its valves are not sufficiently developed, and the outlet is located close to the corner of the eyelids. Due to these features, the infection quickly spreads from the nose to the conjunctival sac.
FEATURES OF THE PHARYN
The pharynx in young children is relatively wide, the palatine tonsils are poorly developed, which explains the rare cases of sore throat in the first year of life. The tonsils are fully developed by the age of 4–5 years. By the end of the first year of life, almond tissue hyperplasias. But its barrier function at this age is very low. Overgrown almond tissue can be susceptible to infection, which is why diseases such as tonsillitis and adenoiditis occur.
The Eustachian tubes open into the nasopharynx and connect it to the middle ear. If an infection enters the middle ear from the nasopharynx, middle ear inflammation occurs.
FEATURES OF THE LARYNX
The larynx in children is funnel-shaped and is a continuation of the pharynx. In children, it is located higher than in adults, and has a narrowing in the area of the cricoid cartilage, where the subglottic space is located. The glottis is formed by the vocal cords. They are short and thin, which is responsible for the child’s high, sonorous voice. The diameter of the larynx in a newborn in the area of the subglottic space is 4 mm, at 5–7 years old – 6–7 mm, by 14 years old – 1 cm. Features of the larynx in children are: its narrow lumen, many nerve receptors, easily occurring swelling of the submucosal layer, which can lead to severe breathing problems.
The thyroid cartilages form a more acute angle in boys over 3 years of age; from the age of 10, a typical male larynx is formed.
FEATURES OF THE TRACHEA
The trachea is a continuation of the larynx. It is wide and short, and the tracheal frame consists of 14–16 cartilaginous rings, which are connected by a fibrous membrane instead of an elastic end plate in adults. The presence of a large number of muscle fibers in the membrane contributes to changes in its lumen.
Anatomically, the trachea of a newborn is located at the level of the IV cervical vertebra, and in an adult – at the level of the VI–VII cervical vertebra. In children, it gradually descends, as does its bifurcation, which is located in a newborn at the level of the third thoracic vertebra, in children 12 years old - at the level of the V-VI thoracic vertebra.
During physiological breathing, the lumen of the trachea changes. During coughing, it decreases by 1/3 of its transverse and longitudinal dimensions. The mucous membrane of the trachea is rich in glands that secrete a secretion that covers the surface of the trachea with a layer 5 microns thick.
The ciliated epithelium promotes the movement of mucus at a speed of 10–15 mm/min from the inside to the outside.
The characteristics of the trachea in children contribute to the development of its inflammation - tracheitis, which is accompanied by a rough, low-pitched cough, reminiscent of a cough “like a barrel.”
FEATURES OF THE BRONCHIAL TREE
The bronchi in children are formed at birth. Their mucous membrane is richly supplied with blood vessels, covered with a layer of mucus, which moves at a speed of 0.25-1 cm/min. A feature of the bronchi in children is that elastic and muscle fibers are poorly developed.
The bronchial tree branches to bronchi of the 21st order. With age, the number of branches and their distribution remain constant. The size of the bronchi changes rapidly in the first year of life and during puberty. They are based on cartilaginous semirings in early childhood. Bronchial cartilage is very elastic, pliable, soft and easily displaced. The right bronchus is wider than the left and is a continuation of the trachea, so foreign bodies are more often found in it.
After the birth of a child, a columnar epithelium with a flickering apparatus. With hyperemia of the bronchi and their swelling, their lumen sharply decreases (up to its complete closure).
Underdevelopment of the respiratory muscles contributes to a weak cough impulse in a small child, which can lead to blockage of small bronchi with mucus, and this, in turn, leads to infection of the lung tissue and disruption of the cleansing drainage function of the bronchi.
With age, as the bronchi grow, wide lumens of the bronchi appear, and the bronchial glands produce less viscous secretions, acute diseases of the bronchopulmonary system are less common compared to younger children.
FEATURES OF THE LUNG
The lungs in children, as in adults, are divided into lobes, and lobes into segments. The lungs have a lobular structure, the segments in the lungs are separated from each other by narrow grooves and partitions of connective tissue. The main structural unit is the alveoli. Their number in a newborn is 3 times less than in an adult. Alveoli begin to develop from 4-6 weeks of age, their formation occurs up to 8 years. After 8 years, the lungs in children increase due to their linear size, and the respiratory surface of the lungs increases in parallel.
The following periods can be distinguished in the development of the lungs:
1) from birth to 2 years, when intensive growth of the alveoli occurs;
2) from 2 to 5 years, when elastic tissue intensively develops, bronchi with peribronchial inclusions of lung tissue are formed;
3) from 5 to 7 years the functional abilities of the lungs are finally formed;
4) from 7 to 12 years, when a further increase in lung mass occurs due to the maturation of lung tissue.
Anatomically, the right lung consists of three lobes (upper, middle and lower). By 2 years, the sizes of the individual lobes correspond to each other, like in an adult.
In addition to the lobar division, segmental division is distinguished in the lungs: in the right lung there are 10 segments, in the left - 9.
The main function of the lungs is breathing. It is believed that 10,000 liters of air pass through the lungs daily. Oxygen absorbed from the inhaled air ensures the functioning of many organs and systems; the lungs take part in all types of metabolism.
The respiratory function of the lungs is carried out with the help of a biologically active substance - surfactant, which also has a bactericidal effect, preventing fluid from entering the pulmonary alveoli.
The lungs remove waste gases from the body.
A feature of the lungs in children is the immaturity of the alveoli; they have a small volume. This is compensated by increased breathing: the younger the child, the more shallow his breathing. The respiratory rate in a newborn is 60, in a teenager it is already 16–18 respiratory movements per minute. Lung development is completed by age 20.
A variety of diseases can disrupt the vital respiratory function of children. Due to the characteristics of aeration, drainage function and evacuation of secretions from the lungs inflammatory process often localized in the lower lobe. This occurs when infants are lying down due to insufficient drainage function. Paravisceral pneumonia most often occurs in the second segment of the upper lobe, as well as in the basal-posterior segment of the lower lobe. The middle lobe of the right lung may often be affected.
The following studies are of greatest diagnostic importance: X-ray, bronchological, determination of blood gas composition, blood pH, study of external respiration function, study of bronchial secretions, computed tomography.
By the frequency of breathing and its relationship with the pulse, the presence or absence of respiratory failure is judged (see Table 14).
Table 14 Age dynamics of respiratory rate (Fomin V.F., 2003)
source: Directory of Children's Diseases.
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