The concept of segmental division of the lungs. X-ray examination of lung segments in the practice of a pulmonologist Number of bronchopulmonary segments in the right lung
The lungs are paired respiratory organs. The characteristic structure of the lung tissue is formed in the second month of intrauterine development of the fetus. After the birth of a child, the respiratory system continues its development, finally forming around 22–25 years. After 40 years of age, lung tissue begins to gradually age.
This organ received its name in Russian due to its property of not sinking in water (due to the air content inside). The Greek word pneumon and the Latin word pulmunes are also translated as “lung.” Hence the inflammatory lesion of this organ is called “pneumonia”. A pulmonologist treats this and other diseases of the lung tissue.
Location
A person's lungs are in the chest cavity and occupy most of it. The chest cavity is bounded in front and behind by the ribs, and below is the diaphragm. It also contains the mediastinum, which contains the trachea, the main circulatory organ - the heart, large (main) vessels, the esophagus and some other important structures of the human body. The chest cavity does not communicate with the external environment.
Each of these organs is completely covered on the outside with pleura - a smooth serous membrane with two layers. One of them fuses with the lung tissue, the second with the chest cavity and mediastinum. A pleural cavity is formed between them, filled with a small amount of fluid. Due to the negative pressure in the pleural cavity and the surface tension of the fluid in it, the lung tissue is kept in a straightened state. In addition, the pleura reduces its friction against the costal surface during the act of breathing.
External structure
Lung tissue resembles a finely porous pink sponge. With age, as well as with pathological processes of the respiratory system, long-term smoking, the color of the pulmonary parenchyma changes and becomes darker.
Lung looks like an irregular cone, the top of which faces upward and is located in the neck area, protruding several centimeters above the collarbone. Below, at the border with the diaphragm, the pulmonary surface has a concave appearance. Its front and back surfaces are convex (and sometimes there are imprints of ribs on it). The inner lateral (medial) surface borders the mediastinum and also has a concave appearance.
On the medial surface of each lung there are the so-called gates, through which the main bronchus and vessels - an artery and two veins - penetrate into the lung tissue.
The sizes of both lungs are not the same: the right one is about 10% larger than the left one. This is due to the location of the heart in the chest cavity: to the left of the midline of the body. This “neighborhood” also determines their characteristic shape: the right one is shorter and wider, and the left one is long and narrow. The shape of this organ also depends on the person’s physique. Thus, in thin people, both lungs are narrower and longer than in obese people, which is due to the structure of the chest.
There are no pain receptors in human lung tissue, and the occurrence of pain in some diseases (for example, pneumonia) is usually associated with the involvement of the pleura in the pathological process.
WHAT ARE THE LUNGS MADE OF?
The human lungs are anatomically divided into three main components: bronchi, bronchioles and acini.
Bronchi and bronchioles
The bronchi are hollow tubular branches of the trachea and connect it directly to the lung tissue. The main function of the bronchi is air circulation.
At approximately the level of the fifth thoracic vertebra, the trachea divides into two main bronchi: right and left, which then go to the corresponding lungs. In the anatomy of the lungs The branching system of the bronchi is important, the appearance of which resembles a tree crown, which is why it is called “bronchial tree”.
When the main bronchus enters the pulmonary tissue, it is first divided into lobar and then into smaller segmental ones (corresponding to each pulmonary segment). Subsequent dichotomous (paired) division of the segmental bronchi ultimately leads to the formation of terminal and respiratory bronchioles - the smallest branches of the bronchial tree.
Each bronchus consists of three membranes:
- external (connective tissue);
- fibromuscular (contains cartilage tissue);
- internal mucosa, which is covered with ciliated epithelium.
As the diameter of the bronchi decreases (during the process of branching), the cartilage tissue and mucous membrane gradually disappear. The smallest bronchi (bronchioles) no longer contain cartilage in their structure, and the mucous membrane is also absent. Instead, a thin layer of cubic epithelium appears.
Acini
The division of the terminal bronchioles leads to the formation of several respiratory orders. From each respiratory bronchiole, alveolar ducts branch in all directions, which blindly end in alveolar sacs (alveoli). The membrane of the alveoli is densely covered with a capillary network. This is where gas exchange occurs between inhaled oxygen and exhaled carbon dioxide.
The diameter of the alveoli is very small and ranges from 150 µm in a newborn child to 280–300 µm in an adult.
The inner surface of each alveoli is covered with a special substance - surfactant. It prevents its collapse, as well as the penetration of fluid into the structures of the respiratory system. In addition, surfactant has bactericidal properties and is involved in some immune defense reactions.
The structure, which includes the respiratory bronchiole and the alveolar ducts and sacs emanating from it, is called the primary lobule of the lung. It has been established that approximately 14–16 respiratory tracts arise from one terminal bronchiole. Consequently, this number of primary lung lobules forms the main structural unit of the lung tissue parenchyma - the acinus.
This anatomical and functional structure received its name because of its characteristic appearance, reminiscent of a bunch of grapes (Latin Acinus - “bunch”). There are approximately 30 thousand acini in the human body.
The total area of the respiratory surface of the lung tissue due to the alveoli ranges from 30 square meters. meters when exhaling and up to about 100 square meters. meters when inhaling.
LOLES AND SEGMENTS OF THE LUNG
Acini form lobules, from which are formed segments, and from segments – shares, making up the whole lung.
There are three lobes in the right lung, and two in the left lung (due to its smaller size). In both lungs, the upper and lower lobes are distinguished, and the middle lobe is also distinguished on the right. The lobes are separated from each other by grooves (fissures).
Shares divided into segments, which do not have visible demarcation in the form of connective tissue layers. Usually there are ten segments in the right lung, eight in the left. Each segment contains a segmental bronchus and a corresponding branch of the pulmonary artery. The appearance of the pulmonary segment is similar to an irregularly shaped pyramid, the apex of which faces the pulmonary hilum and the base faces the pleural layer.
The upper lobe of each lung has an anterior segment. The right lung also has an apical and posterior segment, and the left lung has an apical-posterior segment and two lingular segments (superior and inferior).
In the lower lobe of each lung, there are superior, anterior, lateral and posterobasal segments. In addition, the mediobasal segment is determined in the left lung.
There are two segments in the middle lobe of the right lung: medial and lateral.
Separation by segment of the human lung is necessary to determine the clear localization of pathological changes in the lung tissue, which is especially important for practicing physicians, for example, in the process of treating and monitoring the course of pneumonia.
FUNCTIONAL PURPOSE
The main function of the lungs is gas exchange, in which carbon dioxide is removed from the blood while simultaneously saturating it with oxygen, necessary for the normal metabolism of almost all organs and tissues of the human body.
Oxygenated when inhaled air enters the alveoli through the bronchial tree.“Waste” blood from the pulmonary circulation, containing a large amount of carbon dioxide, also enters there. After gas exchange, carbon dioxide is again expelled through the bronchial tree during exhalation. And oxygenated blood enters the systemic circulation and is sent further to the organs and systems of the human body.
The act of breathing in humans is involuntary, reflexive. A special structure of the brain is responsible for this - the medulla oblongata (respiratory center). The degree of saturation of the blood with carbon dioxide regulates the rate and depth of breathing, which becomes deeper and more frequent as the concentration of this gas increases.
There is no muscle tissue in the lungs. Therefore, their participation in the act of breathing is exclusively passive: expansion and contraction during movements of the chest.
The muscle tissue of the diaphragm and chest is involved in breathing. Accordingly, there are two types of breathing: abdominal and thoracic.
On inhalation, the volume of the thoracic cavity increases, in it negative pressure is created(below atmospheric), which allows air to flow freely into the lungs. This is accomplished by contraction of the diaphragm and the muscular frame of the chest (intercostal muscles), which leads to the raising and divergence of the ribs.
On exhalation, on the contrary, the pressure becomes higher than atmospheric pressure, and the removal of air saturated with carbon dioxide is carried out almost passively. In this case, the volume of the chest cavity decreases due to relaxation of the respiratory muscles and lowering of the ribs.
In some pathological conditions, the so-called auxiliary respiratory muscles are also included in the act of breathing: neck, abdominal, etc.
The amount of air that a person inhales and exhales at one time (tidal volume) is about half a liter. An average of 16–18 respiratory movements are performed per minute. More than one day passes through the lung tissue 13 thousand liters of air!
The average lung capacity is approximately 3–6 liters. In humans it is excessive: during inhalation we use only about one-eighth of this capacity.
In addition to gas exchange, the human lungs have other functions:
- Participation in maintaining acid-base balance.
- Removing toxins, essential oils, alcohol fumes, etc.
- Maintaining the body's water balance. Normally, about half a liter of water per day evaporates through the lungs. In extreme situations, daily water excretion can reach 8–10 liters.
- The ability to retain and dissolve cell conglomerates, fatty microemboli and fibrin clots.
- Participation in blood clotting processes (coagulation).
- Phagocytic activity – participation in the functioning of the immune system.
Consequently, the structure and functions of the human lungs are closely interconnected, which allows for the smooth functioning of the entire human body.
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A segment is a cone-shaped section of the lung lobe, whose base faces the surface of the lung and its apex faces the root, ventilated by a third-order bronchus, and consisting of pulmonary lobes. The segments are separated from each other by connective tissue. In the center of the segment there are a segmental bronchus and an artery, and in the connective tissue septum there is a segmental vein.
According to the International Anatomical Nomenclature, the right and left lungs are distinguished by 10 segments. The names of the segments reflect their topography and correspond to the names of the segmental bronchi.
Right lung.
IN upper lobe the right lung has 3 segments:
– apical segment ,segmentum apicale, occupies the superomedial portion of the upper lobe, enters the upper opening of the chest and fills the dome of the pleura;
– posterior segment , segmentum posterius, its base is directed outward and backward, bordering there with the II-IV ribs; its apex faces the upper lobe bronchus;
– anterior segment , segmentum anterius, its base is adjacent to the anterior wall of the chest between the cartilages of the 1st and 4th ribs, as well as to the right atrium and the superior vena cava.
Average share has 2 segments:
– lateral segment, segmentum laterale, its base is directed forward and outward, and its apex is directed upward and medially;
– medial segment, segmentum mediale, comes into contact with the anterior chest wall near the sternum, between the IV-VI ribs; it is adjacent to the heart and diaphragm.
Rice. 1.37. Lungs.
1 – larynx, larynx; 2 – trachea, trachea; 3 – apex of the lung, apex pulmonis; 4 – costal surface, facies costalis; 5 – bifurcation of the trachea, bifurcatio tracheae; 6 – upper lobe of the lung, lobus pulmonis superior; 7 – horizontal fissure of the right lung, fissura horizontalis pulmonis dextri; 8 – oblique fissure, fissura obliqua; 9 – cardiac notch of the left lung, incisura cardiaca pulmonis sinistri; 10 – middle lobe of the lung, lobus medius pulmonis; 11 – lower lobe of the lung, lobus inferior pulmonis; 12 – diaphragmatic surface, facies diaphragmatica; 13 – base of the lung, basis pulmonis.
IN lower lobe There are 5 segments:
– apical segment, segmentumapicale (superius), occupies the wedge-shaped apex of the lower lobe and is located in the paravertebral region;
– medial basal segment, segmentum basale mediale (cardiacum), The base occupies the mediastinal and partly the diaphragmatic surface of the lower lobe. It is adjacent to the right atrium and the inferior vena cava;
– anterior basal segment , segmentum basale anterius, is located on the diaphragmatic surface of the lower lobe, and the large lateral side is adjacent to the chest wall in the axillary region between the VI-VIII ribs;
– lateral basal segment , segmentum basale laterale, wedged between other segments of the lower lobe so that its base is in contact with the diaphragm, and its side is adjacent to the chest wall in the axillary region, between the VII and IX ribs;
– posterior basal segment , segmentum basale posterius, located paravertebrally; it lies posterior to all other segments of the lower lobe, penetrating deeply into the costophrenic sinus of the pleura. Sometimes it is separated from this segment .
Left lung.
It also distinguishes 10 segments.
The upper lobe of the left lung has 5 segments:
– apical-posterior segment , segmentum apicoposterius, corresponds in shape and position apical segment ,segmentum apicale, and posterior segment , segmentum posterius, upper lobe of the right lung. The base of the segment is in contact with the posterior sections of the III-V ribs. Medially, the segment is adjacent to the aortic arch and subclavian artery; may be in the form of two segments;
– anterior segment , segmentum anterius, is the largest. It occupies a significant part of the costal surface of the upper lobe, between the I-IV ribs, as well as part of the mediastinal surface, where it comes into contact with truncus pulmonalis ;
– upper lingual segment, segmentumlingulare superius, is a section of the upper lobe between ribs III-V in front and ribs IV-VI in the axillary region;
– lower lingual segment, segmentum lingulare inferius, is located below the upper one, but almost does not come into contact with the diaphragm.
Both lingular segments correspond to the middle lobe of the right lung; they come into contact with the left ventricle of the heart, penetrating between the pericardium and the chest wall into the costomediastinal sinus of the pleura.
In the lower lobe of the left lung there are 5 segments, which are symmetrical to the segments of the lower lobe of the right lung:
– apical segment, segmentum apicale (superius), occupies a paravertebral position;
– medial basal segment, segmentum basale mediale, in 83% of cases it has a bronchus that begins with a common trunk with the bronchus of the next segment, segmentum basale anterius. The latter is separated from the lingular segments of the upper lobe, fissura obliqua, and participates in the formation of the costal, diaphragmatic and mediastinal surfaces of the lung;
– lateral basal segment , segmentum basale laterale, occupies the costal surface of the lower lobe in the axillary region at the level of the XII-X ribs;
– posterior basal segment, segmentum basale posterius, is a large area of the lower lobe of the left lung located posterior to other segments; it comes into contact with the VII-X ribs, the diaphragm, the descending aorta and the esophagus;
– segmentum subapicale (subsuperius) this one is not always available.
Pulmonary lobules.
The lung segments consist of fromsecondary pulmonary lobules, lobuli pulmones secundarii, in each of which includes a lobular bronchus (4-6 orders). This is a pyramidal-shaped area of pulmonary parenchyma up to 1.0-1.5 cm in diameter. Secondary lobules are located on the periphery of the segment in a layer up to 4 cm thick and are separated from each other by connective tissue septa, which contain veins and lymphocapillaries. Dust (coal) is deposited in these partitions, making them clearly visible. In both lungs there are up to 1 thousand secondary lobules.
5) Histological structure. alveolar tree, arbor alveolaris.
The pulmonary parenchyma, according to its functional and structural features, is divided into two sections: conductive - this is the intrapulmonary part of the bronchial tree (mentioned above) and respiratory, which carries out gas exchange between the venous blood flowing to the lungs through the pulmonary circulation and the air in the alveoli.
The respiratory section of the lung consists of acini, acinus , – structural and functional units of the lung, each of which is a derivative of one terminal bronchiole. The terminal bronchiole divides into two respiratory bronchioles, bronchioli respiratorii , on the walls of which appear alveoli, alveoli pulmones,- cup-shaped structures lined from the inside with flat cells, alveolocytes. Elastic fibers are present in the walls of the alveoli. At the beginning, along the respiratory bronchiole, there are only a few alveoli, but then their number increases. Epithelial cells are located between the alveoli. In total, there are 3-4 generations of dichotomous division of respiratory bronchioles. Respiratory bronchioles, expanding, give rise to alveolar ducts, ductuli alveolares (from 3 to 17), each of which ends blindly alveolar sacs, sacculi alveolares. The walls of the alveolar ducts and sacs consist only of alveoli, intertwined with a dense network of blood capillaries. The inner surface of the alveoli, facing the alveolar air, is covered with a film of surfactant - surfactant, which equalizes surface tension in the alveoli and prevents their walls from gluing - atelectasis. In the lungs of an adult there are about 300 million alveoli, through the walls of which gases diffuse.
Thus, respiratory bronchioles of several orders of branching, extending from one terminal bronchiole, alveolar ducts, alveolar sacs and alveoli form pulmonary acinus, acinus pulmonis . The respiratory parenchyma of the lungs has several hundred thousand acini and is called the alveolar tree.
The terminal respiratory bronchiole and the alveolar ducts and sacs extending from it form primary lobule lobulus pulmonis primarius . There are about 16 of them in each acini.
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6) Age characteristics. The lungs of a newborn have an irregular cone shape; the upper lobes are relatively small in size; The middle lobe of the right lung is equal in size to the upper lobe, and the lower lobe is relatively large. In the 2nd year of a child’s life, the size of the lobes of the lung relative to each other becomes the same as in an adult. The weight of the newborn’s lungs is 57 g (from 39 to 70 g), volume 67 cm³. Age-related involution begins after 50 years. The boundaries of the lungs also change with age.
7) Developmental anomalies. Pulmonary agenesis – absence of one or both lungs. If both lungs are missing, the fetus is not viable. Lung hypogenesis – underdevelopment of the lungs, often accompanied by respiratory failure. Anomalies of the terminal parts of the bronchial tree – bronchiectasis – irregular saccular dilatations of terminal bronchioles. Reverse position of the thoracic cavity organs, while the right lung contains only two lobes, and the left lung consists of three lobes. The reverse position can be only thoracic, only abdominal and total.
8) Diagnostics. An x-ray examination of the chest clearly shows two light “lung fields”, which are used to judge the lungs, since due to the presence of air in them, they easily transmit x-rays. Both pulmonary fields are separated from each other by an intense central shadow formed by the sternum, spinal column, heart and large vessels. This shadow constitutes the medial border of the lung fields; the upper and lateral borders are formed by ribs. Below is the diaphragm. The upper part of the pulmonary field is crossed by the clavicle, which separates the supraclavicular region from the subclavian region. Below the clavicle, the anterior and posterior parts of the ribs intersecting each other are layered onto the pulmonary field.
The X-ray method of research allows you to see changes in the relationships of the chest organs that occur during breathing. When you inhale, the diaphragm lowers, its domes flatten, the center moves slightly downwards - the ribs rise, the intercostal spaces become wider. The pulmonary fields become lighter, the pulmonary pattern becomes clearer. The pleural sinuses “clear up” and become noticeable. The position of the heart approaches vertical, and it takes on a shape close to triangular. When you exhale, the opposite relationship occurs. Using X-ray kymography, you can also study the work of the diaphragm during breathing, singing, speech, etc.
With layer-by-layer radiography (tomography), the structure of the lung is revealed better than with ordinary radiography or fluoroscopy. However, even on tomograms it is not possible to differentiate individual structural formations of the lung. This becomes possible thanks to a special method of x-ray examination (electroradiography). The radiographs obtained using the latter show not only the tubular systems of the lung (bronchi and blood vessels), but also the connective tissue frame of the lung. As a result, it is possible to study the structure of the parenchyma of the entire lung in a living person.
Pleura.
In the chest cavity there are three completely separate serous sacs - one for each lung and one, middle, for the heart.
The serous membrane of the lung is called the pleura, p1eura. It consists of two sheets:
visceral pleura pleura visceralis ;
pleura parietal, parietal pleura parietalis .
The lungs are a paired organ consisting of tubular systems. They are formed by segmental bronchi, their branches, pulmonary, blood, and lymphatic vessels. The growth of tubular formations is parallel to each other. They form bundles of bronchi, veins, and arteries. The image shows that each lobe of the organ consists of small sections that determine the segmental structure of the lungs.
Description and classification of bronchopulmonary segments
The bronchopulmonary segment is a functional part of the main respiratory organ. In medicine, there are several versions of the classification of lobar areas. Specialists of different profiles (radiologists, thoracic surgeons, pathologists) divide the lobes of the lung into an average of 4-12 segments. In relation to the official classification, in accordance with the anatomical nomenclature, it is customary to distinguish 10 segments of the organ.
All sectors figuratively resemble pyramids or irregular cones. They are located in a horizontal plane, with their base towards the outer surface of the lung, and their apex towards the hilum (the entry point of nerves, main bronchi, blood vessels). The sections differ in pigmentation, so their boundaries are visually visible.
Segmental constitution of the right lung
The number of segment plots depends on the shared structure.
The upper lobe of the right lung includes three lobes:
- S1 – located under the pleural vault, protruding in the upper aperture of the chest (the opening formed by the sternum, ribs, thoracic vertebra);
- S2 – lies posteriorly on the border with 2-4 ribs;
- S3 – partially intervening with the vena cava coming from the head and the right atrium, the base abuts the anterior chest wall.
The middle lobe is divided into 2 segments. S4 – moves forward. S5 – touches the sternum and anterior chest wall, fully communicates with the diaphragm and heart.
The lower lobe is formed by 5 sectors:
- S6 – basal section, lies near the spinal column in the area of the wedge-shaped lobar apex;
- S7 – contacts the mediastinum and diaphragm;
- S8 – the lateral part is in contact with the chest wall, the entire segment lies on the surface of the diaphragm;
- S9 – looks like a wedge between other areas, the base touches the diaphragm, the side – the area of the chest near the armpits, anatomically located between the 7th and 9th ribs;
- S10 - lies along the paravertebral line, is located further away from all other segments, penetrates into the depths of the organ, into the sinus of the pleura (the depression formed by the ribs and the diaphragm).
Segmental structure of the left lung
Segments of the left lung are different from the right. This is due to the different structure of the lobes and the organ as a whole. The left lung is 10% smaller in volume. At the same time, it is longer and narrower. The dome of the organ is lowered. The width is smaller due to the heart located on the left side of the chest.
Dividing the upper lobe into segments:
- S1+2 – the base touches 3-5 ribs, the inner part is adjacent to the subclavian artery and the arch of the main blood vessel (aorta), can be in the form of one or two segments;
- S3 is the largest section of the upper lobe, located in the area of ribs 1-4, touching the pulmonary trunk;
- S4 – in front of the chest is located between 3-5 ribs, in the axillary region – between 4-6 ribs;
- S5 – located under S4, but does not touch the diaphragm.
S4 and S5 are lingular segments that topographically correspond to the middle lobe of the right lung. From the inside, they touch the left ventricle of the heart, pass between the pericardial sac and the chest wall into the pleural sinus.
Segmental structure of the lower lobe of the lung
- S6 – located paravertebrally;
- S7 – in most cases includes the bronchus (trunk and beginning of the bronchus of the underlying segment);
- S8 – participates in the formation of the diaphragmatic, costal and inner surface of the left lung;
- S9 – located at the level of 7-9 ribs in the axillary region.
- S10 is a large section located posteriorly in the area of ribs 7-10, touching the esophagus, descending line of the aorta, diaphragm, the segment is unstable.
What do the segments look like on an x-ray?
Since the structural unit of the lung (acinus) is not determined on x-ray, lobar segments are assessed to identify pathological processes. In the photographs they give a distinct shadow with the exact localization of altered or inflamed tissues (parenchyma).
To determine the boundaries of areas, diagnosticians use special markers. First, the lobes are isolated, and then the segments of the lungs are identified on the radiograph.. All sections of the organ are conventionally separated by an interlobar oblique strip or fissure.
To separate the upper lobe, focus on the following indicators:
- in the rear view of the chest, the line begins from the process of the 3rd thoracic vertebra;
- at the level of the 4th rib it passes into the horizontal plane;
- then rushes to the highest midpoint of the diaphragm;
- in the lateral projection, the horizontal gap starts from the 3rd thoracic vertebra;
- goes through the root of the lung;
- ends at the diaphragm (midpoint).
The line in the right lung separating the middle and upper lobes runs along the 4th rib to the root of the organ. If you look at the picture from the side, it starts from the root, runs horizontally and leads to the sternum.
In the diagram, the slots are indicated by a straight line or a dotted line. Knowledge of the topography of the segments and the ability to correctly decipher images determines how accurately the diagnosis will be made and successful treatment will be carried out.
When examining X-ray films, it is necessary to be able to distinguish pathological processes from the abnormal structure of the chest organs, individual human anatomy, and congenital defects.
How are segments determined on computed tomography?
The tomography method is fundamentally different from x-rays. Lung segments on CT and their structure can be viewed layer by layer in several projections.
On cross-sections of a CT scan, the layers of the pleura, connective tissue layers between parts of the lung, and fissures are not visible. Their location can be guessed from the vascular pattern. In the area of the pleura, arteries into veins are not visualized, therefore, in places where there should be interlobar fissures, an area without vessels is determined. High-resolution tomography, in which the pattern thickness can be reduced to 1.5 mm, allows you to see the layers of the pulmonary membrane.
In the frontal projection, the main interlobar line departs from the chest and goes to the mediastinum. It ends on the back at the level of the 3rd thoracic vertebra. Passing through the organ, it affects the root and a third of the diaphragm. If you make a thin axial cut, the main gap between the lobes will look like an even horizontal line of white color.
If there is an additional interlobar fissure in the image, this is the right lung. In the area of the white zone without blood vessels, there are ring-shaped stripes of low density with blurred contours. This is due to the fact that the right lung is larger than the left. This sign is also characteristic of thickening of the pleural film between the lobes and indicates an inflammatory process.
The localization of bronchopulmonary segments is distinguished by the direction of blood vessels and bronchi of different sizes. Each segmental section faces the root with its apex, and its base faces the muscular septum and chest wall. In the root region, arterial and venous vessels, bronchi are clearly visible in transverse and longitudinal projection. At the base of each section, the vessels decrease in size.
Differences in segmental anatomy of the lungs in children
The peak of segmental formation of the respiratory organ occurs in the first 7 years of a child’s life. The size of the structural units of the parenchyma (alveoli) in children of the first year of life is half that of children 12 years old. In terms of their structure, the bronchi penetrating the segments are not yet fully formed.
There is a denser layer between the segments themselves, which clearly delimits them. The structure of the interlobar pleura is loose and easily amenable to morphological changes.
On x-rays and CT scans, the lines between the segments are unclear. In infants under 2 years of age, they resemble notches on the surface of the organ. Groups of lymph nodes flow into the main fissures, which is associated with close.
Externally, the boundaries of the lobes are determined by passing furrows. In children, to distinguish segments, the arrangement of the bronchial tree and branches extending from it is used.
Each segment is independently supplied with blood, innervated and ventilated. This fact helps to highlight individual areas with their projection on the chest. This is important during lung operations and detection of focal inflammation.
The lungs (pulmones) are a paired organ that occupies almost the entire chest cavity and is the main organ of the respiratory system. Their size and shape are not constant and can change depending on the phase of breathing.
Each lung has the shape of a truncated cone, the rounded apex (apex pulmonis) (Fig. 202, 203, 204) of which is directed to the supraclavicular fossa and through the upper opening of the chest protrudes into the neck to the level of the neck of the 1st rib, and a slightly concave base (basis pulmonis ) (Fig. 202) facing the dome of the diaphragm. The outer convex surface of the lungs is adjacent to the ribs; on the inner side they include the main bronchi, pulmonary artery, pulmonary veins and nerves that form the root of the lungs (radix pulmonis). The right lung is wider and shorter. In the lower anterior edge of the left lung there is a depression to which the heart is adjacent. It is called the cardiac notch of the left lung (incisura cardiaca pulmonis sinistri) (Fig. 202, 204). In addition, it contains many lymph nodes. On the concave surface of the lungs there is a depression called the hilus pulmonum. At this point, the pulmonary and bronchial arteries, bronchi and nerves enter the lungs and the pulmonary and bronchial veins, as well as lymphatic vessels, exit.
The lungs consist of lung lobes (lobi pulmones). Deep grooves, each of which is called an oblique fissure (fissura obliqua) (Fig. 202, 203, 204), the right lung is divided into three lobes. Among them, the upper lobe (lobus superior) (Fig. 202, 203, 204), the middle lobe (lobus medius) (Fig. 202, 203) and the lower lobe (lobus inferior) (Fig. 202, 204) are distinguished, and the left - into two: upper and lower. The upper interlobar groove of the right lung is called the horizontal fissure (fissura horizontalis) (Fig. 202). The lungs are divided into the costal surface (facies costalis) (Fig. 202, 203, 204), the diaphragmatic surface (facies diaphragmatica) (Fig. 202, 203, 204) and the medial surface (facies medialis), in which the vertebral part (pars vertebralis) is distinguished ) (Fig. 203), mediastinal, or mediastinal, part (pars mediastinalis) (Fig. 203, 204) and cardiac indentation (impressio cardica) (Fig. 203, 204).
| Rice. 202. Lungs: 1 - larynx; |
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 | Rice. 203. Right lung: 1 - apex of the lung; |
 | Rice. 204. Left lung: 1 - root of the lung; |
 | Rice. 205. Lobule of lung: 1 - bronchiole; |
  | Rice. 206. Bronchopulmonary segments A - front; B - behind; B - right; G - left; D - from the inside and to the right; |
 | Rice. 207. Boundaries of the lungs A - front view: |
 | Rice. 207. Boundaries of the lungs B - rear view: |
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| Rice. 208. Boundaries of the right lung (side view): 1 - upper lobe; | Rice. 209. Borders of the left lung (side view): 1 - upper lobe; |
The peculiar skeletal basis of the organ is made up of the main bronchi, which are woven into the lungs, forming the bronchial tree (arbor bronchialis), with the right bronchus forming three branches, and the left - two. The branches, in turn, are divided into bronchi of the 3rd–5th order, the so-called subsegmental, or middle, bronchi, and those into small bronchi, the cartilaginous rings in the walls of which decrease and turn into small plaques.
The smallest of them (1–2 mm in diameter) are called bronchioli (Fig. 205), they do not contain glands and cartilage at all, branch into 12–18 border, or terminal, bronchioles (bronchioli terminales), and those - to the respiratory, or respiratory, bronchioles (bronchioli respiratorii) (Fig. 205). The branches of the bronchi supply air to the lobes of the lungs, into which they are intertwined, thereby carrying out gas exchange between tissues and blood. Respiratory bronchioles supply air to small areas of the lung, which are called acini (acini) and represent the main structural and functional unit of the respiratory department. Within the acinus, the respiratory bronchioles branch, expand and form alveolar ducts (ductuli alveolares) (Fig. 205), each of which ends in two alveolar sacs. On the walls of the alveolar ducts and sacs there are vesicles, or alveoli, of the lungs (alveoli pulmonis) (Fig. 205). In an adult, their number reaches 400 million. One acini contains approximately 15–20 alveoli. The walls of the alveoli are lined with single-layer squamous epithelium, under which in the connective tissue septa there are blood capillaries, which represent an aerohematic barrier (between blood and air), but do not interfere with gas exchange and the release of vapors.
The lungs are also divided into bronchopulmonary segments (segmenta bronchopulmonalia): the right - into 11, and the left - into 10 (Fig. 206). These are areas of the pulmonary lobe that are ventilated by only one third-order bronchus and supplied with blood by one artery. Veins are usually common to two adjacent segments. The segments are separated from each other by connective tissue partitions and have the shape of irregular cones or pyramids. The apex of the segments faces the hilum, and the base faces the outer surface of the lungs.
Outside, each lung is surrounded by pleura (Fig. 205), or pleural sac, which is a thin, shiny, smooth, moist serous membrane (tunica serosa). There are parietal, or parietal, pleura (pleura parietalis), lining the inner surface of the chest walls, and pulmonary (pleura pulmonalis), tightly fused with lung tissue, which is also called visceral. Between these pleurae a gap is formed, called the pleural cavity (cavum pleurae) and filled with pleural fluid (liquor pleurae), which facilitates the respiratory movements of the lungs.
A space is formed between the pleural sacs, which is limited in front by the sternum and costal cartilages, behind by the spinal column, and below by the tendon part of the diaphragm. This space is called the mediastinum and is conventionally divided into anterior and posterior mediastinum. In the anterior are the heart with the pericardial sac, large vessels of the heart, phrenic vessels and nerves, as well as the thymus gland. In the posterior part lie the trachea, thoracic aorta, esophagus, thoracic lymphatic duct, azygos and semi-gypsy veins, sympathetic nerve trunks and vagus nerves.
Segment S1 (apical or apical) of the right lung. Refers to the upper lobe of the right lung. Topographically projected onto the chest along the anterior surface of the 2nd rib, through the apex of the lung to the spine of the scapula.
Segment S2 (posterior) of the right lung. Refers to the upper lobe of the right lung. Topographically projected onto the chest along the posterior surface paravertebrally from the upper edge of the scapula to its middle.
Segment S3 (anterior) of the right lung. Refers to the upper lobe of the right lung. Topographically, 2 to 4 ribs are projected onto the chest in front.
Segment S4 (lateral) of the right lung. Refers to the middle lobe of the right lung. Topographically projected onto the chest in the anterior axillary region between the 4th and 6th ribs.
Segment S5 (medial) of the right lung. Refers to the middle lobe of the right lung. Topographically projected onto the chest between the 4th and 6th ribs closer to the sternum.
Segment S6 (superior basal) of the right lung. Refers to the lower lobe of the right lung. Topographically projected onto the chest in the paravertebral region from the middle of the scapula to its lower angle.
Segment S7 (medial basal) of the right lung. Refers to the lower lobe of the right lung. Topographically localized on the inner surface of the right lung, located below the root of the right lung. It is projected onto the chest from the 6th rib to the diaphragm between the sternum and midclavicular lines.
Segment S8 (anterior basal) of the right lung. Refers to the lower lobe of the right lung. Topographically delimited anteriorly by the main interlobar groove, inferiorly by the diaphragm, and posteriorly by the posterior axillary line.
Segment S9 (lateral basal) of the right lung. Refers to the lower lobe of the right lung. Topographically projected onto the chest between the scapular and posterior axillary lines from the middle of the scapula to the diaphragm.
Segment S10 (posterior basal) of the right lung. Refers to the lower lobe of the right lung. Topographically projected onto the chest from the lower angle of the scapula to the diaphragm, delimited on the sides by the paravertebral and scapular lines.
Segment S1+2 (apical-posterior) of the left lung. It is a combination of C1 and C2 segments, which is due to the presence of a common bronchus. Refers to the upper lobe of the left lung. Topographically projected onto the chest along the anterior surface from the 2nd rib and upward, through the apex to the middle of the scapula.
Segment S3 (anterior) of the left lung. Refers to the upper lobe of the left lung. Topographically, the 2nd to 4th ribs are projected onto the chest in front.
Segment S4 (superior lingular) of the left lung. Refers to the upper lobe of the left lung. Topographically projected onto the chest along the anterior surface of the 4th to 5th ribs.
Segment S5 (lower lingular) of the left lung. Refers to the upper lobe of the left lung. Topographically projected onto the chest along the anterior surface from the 5th rib to the diaphragm.
Segment S6 (superior basal) of the left lung. Refers to the lower lobe of the left lung. Topographically projected onto the chest in the paravertebral region from the middle of the scapula to its lower angle.
Segment S8 (anterior basal) of the left lung. Refers to the lower lobe of the left lung. Topographically delimited anteriorly by the main interlobar groove, inferiorly by the diaphragm, and posteriorly by the posterior axillary line.
Segment S9 (lateral basal) of the left lung. Refers to the lower lobe of the left lung. Topographically projected onto the chest between the scapular and posterior axillary lines from the middle of the scapula to the diaphragm.
Segment S10 (posterior basal) of the left lung. Refers to the lower lobe of the left lung. Topographically projected onto the chest from the lower angle of the scapula to the diaphragm, delimited on the sides by the paravertebral and scapular lines.
An X-ray of the right lung is presented in a lateral projection indicating the topography of the interlobar fissures.
The lungs are located in the chest, occupying most of it, and are separated from each other by the mediastinum. The sizes of the lungs are unequal due to the higher position of the right dome of the diaphragm and the position of the heart, shifted to the left.
Each lung has lobes separated by deep fissures. The right lung consists of three lobes, the left - of two. The right upper lobe accounts for 20% of the lung tissue, the middle lobe - 8%, the lower right lobe - 25%, the upper left lobe - 23%, the lower left lobe - 24%.
The main interlobar fissures are projected on the right and left in the same way - from the level of the spinous process of the 3rd thoracic vertebra they are directed obliquely down and forward and cross the 6th rib at the place where its bony part transitions into the cartilaginous part.
An additional interlobar fissure of the right lung is projected onto the chest along the 4th rib from the midaxillary line to the sternum.
The figure shows: Upper Lobe - upper lobe, Middle Lobe - middle lobe, Lower Lobe - lower lobe.
