Topography of the main bronchi. Internal organs of the chest cavity trachea bronchi topography blood supply
To study the structure and topography of the trachea, bronchi, lungs for the purposes of theoretical and practical medicine.
II. Lesson equipment:
Preparations of the trachea, bronchi, lungs, dummies, tables.
III. Methodical instructions:
On preparations we study the structure of the trachea. It consists of 16-20 cartilaginous half-rings connected by annular ligaments, forming a membranous wall at the back, to which the esophagus is adjacent. We determine its boundaries (begins at the level of the upper edge of the VII cervical vertebra, ends at the level of the upper edge of the V thoracic vertebra), parts (cervical and thoracic) and formations located in front, on the sides and behind the trachea. Follow the trachea to the place of its division (bifurcation) into two main bronchi, which are part of the roots of the lungs. Follow the main bronchi (bronchi of the 1st order) from the bifurcation of the trachea to the gates of the lungs, where they are divided on the right into three, and on the left into two lobar bronchi (bronchi of the 2nd order). We pay attention to the structure and topography of the main bronchi. The right one is wider and shorter, consists of 6-8 cartilaginous half-rings, an unpaired vein is thrown over it, and the right pulmonary artery is located below. The left main bronchus is narrower and longer, consists of 9-12 cartilaginous half-rings, the left pulmonary artery and the aortic arch are located on top, the esophagus and the descending part of the aorta are behind. Considering the structure of the lungs, we distinguish their surfaces (costal, diaphragmatic, medial, interlobar) and edges (anterior, lower and posterior). On the medial surface we find the gates of the lungs and the roots of the lungs, as part of the root of the right lung, the bronchus occupies an upper position in relation to the pulmonary artery and veins, and in the left - the bronchus lies between the pulmonary artery from above and the veins - from below. On the costal surface we find an oblique and horizontal gap separating the lobes of the lung, we determine their boundaries. On the model of the right lung, we consider the segments of the upper lobe (superior, anterior and posterior), middle lobe (medial and lateral), lower lobe (apical or superior, anterior basal, posterior basal, medial basal and lateral basal). In the upper lobe of the left lung, the apical-posterior, anterior, and superior reed segments. The segments of the lower lobe of the left lung correspond to the segments of the lower lobe of the right lung. The main bronchi in the gates of the lungs are divided into lobar, segmental, lobular, terminal they form the respiratory tree. The alveolar tree performs a respiratory function (the function of gas exchange), it consists of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli, which form the structural unit of the lung - the acinus. On the tables and the skeleton, we determine the upper, lower, anterior and posterior boundaries of the lungs in their projection onto the chest.
IV. Tests and sample answers to the topic:
1. Specify the epithelium lining the mucous membrane of the trachea
A. multilayer
b. simple squamous (flat)
V. ciliated
g. cylindrical
d. everything is correct
2. Indicate at the level of which vertebra is the beginning of the trachea in an adult
A. IV cervical vertebra
b. VI cervical vertebra
V. V cervical vertebra
d. 1st thoracic vertebra
d. everything is correct
3. Specify the anatomical formation at the level of which the tracheal bifurcation is located in an adult
A. sternum angle
b. V thoracic vertebra
V. jugular notch of sternum
d. upper edge of the aortic arch
d. everything is correct
4. Specify the anatomical formations located behind the trachea
A. esophagus
b. nervus vagus
V. aortic arch
d. everything is correct
5. Specify the correct topographic-anatomical relationship of the main bronchus and blood vessels (from top to bottom) in the hilum of the left lung
A. pulmonary artery, main bronchus, pulmonary veins
b. main bronchus, pulmonary artery, pulmonary veins
V. main bronchus, pulmonary veins, pulmonary artery
d. pulmonary veins, pulmonary artery, main bronchus
d. everything is correct
6. Specify the anatomical formations located above the root of the left lung
A. aortic arch
b. unpaired vein
V. semi-unpaired vein
d. everything is correct
7. Specify the anatomical formations located above the right main bronchus
A. semi-unpaired vein
b. arch of the thoracic lymphatic duct
V. unpaired vein
bifurcation of the pulmonary trunk
d. everything is correct
8. Specify the anatomical formations that enter the hilum of the lung
A. pulmonary artery
b. pulmonary vein
V. main bronchus
g. lymphatic vessels.
d. everything is correct
9. Specify the segmental bronchi formed during branching
right upper lobe bronchus
A. anterior basal
b. apical
V. medial
g. front
d. everything is correct
10. Specify the segmental bronchi formed by branching of the left lower lobe bronchus
A. posterior basal
b. lateral basal
V. inferior reed
medial basal
d. everything is correct
1.a c, 2.b, 3.b, 4.a, 5.a, 6.a, 7.c, 8.a c, 9.b d, 10.a b d.
Lesson No. 11
Topic: Anatomy and topography of the pleura and mediastinum.
I. Purpose and motivational characteristics of the lesson:
Know the structure of pleural sacs, their boundaries, relation to the lungs and mediastinal organs and be able to show parts of the pleura, pleural cavity, pleural sinuses on the preparation. Know the boundaries of the mediastinum and be able to show the mediastinum, its parts and organs on the preparation. To study the structure of the pleura, mediastinal organs and their topographic relationships, to apply the acquired knowledge in the study of other sections of anatomy and clinical disciplines.
II. Lesson equipment: Skeleton, small organ complex, tables, diagrams, dummies. Textbook of anatomy. Atlas of human anatomy. Tests of the I level of assimilation and standards of answers to them.
III. Guidelines
The lungs (pulmonis) are located in the right and left pleural sacs. The visceral pleura covers the surfaces and fuses tightly with the surface of the lung and lines the interlobar fissures. It forms the inner wall of the pleural cavity and passes along the root of the lung into the parietal pleura, which forms the outer wall of the pleural cavity. To study parts of the parietal pleura lining the walls of the chest cavity from the inside: mediastinal from the side of the mediastinum, diaphragmatic on the diaphragm and costal on the inner surface of the chest wall and the dome of the pleura. Then know the places of transition of the diaphragmatic pleura to the costal one on the right and left, study the right and left costal-diaphragmatic sinuses, the places of transition of the mediastinal pleura to the costal one (in front); and in the diaphragmatic (bottom) pleura. To study the boundaries of the pleural sacs and their projections on the surface of the chest. When studying the anterior borders of the pleural sacs, it is necessary to note their closest convergence at the level from the II to IV ribs and the divergence above and below this area, where the triangular upper and lower interpleural fields are distinguished, to which are adjacent: the thymus gland to the upper, the pericardium to the lower and heart. The mediastinum (mediastinum) forms a complex of organs located between the pleural sacs. The borders of the mediastinum are in front - the sternum and cartilages of the ribs, behind - the thoracic spine, below - the diaphragm, above - the upper aperture of the chest, and on the sides - the mediastinal pleura. The superior mediastinum lies above the horizontal plane, which runs from the angle of the sternum to the cartilaginous disc between the IV and V thoracic vertebrae. The organs of the upper mediastinum: behind the handle of the sternum lies the thymus gland, behind it are large vessels, part of the trachea of the esophagus and nerves. The inferior mediastinum is located below this plane and is divided into anterior, middle and posterior. The anterior mediastinum, located between the posterior surface of the sternum and the anterior surface of the pericardium, contains the parasternal lymph nodes, internal mammary arteries and veins. Posterior mediastinum, located behind the heart and pericardium. Below the roots of the lungs, they are located - the esophagus with vagus nerves along its course, the thoracic aorta, the semi-unpaired vein (left), the thoracic duct, the unpaired vein (right), as well as the sympathetic trunks and celiac nerves on both sides. In the middle mediastinum - the pericardium, the heart and, located between the pericardium and the mediastinal pleura, the phrenic nerves.
IV. Tests and sample answers to the topic
1. Specify the anatomical structures bordering the mediastinal pleura on the right:
A. thoracic aorta
b. superior vena cava
V. unpaired vein
esophagus
d. everything is correct
2. Specify the anatomical formations with which it borders
mediastinal pleura on the left:
A. esophagus
b. superior vena cava
V. thoracic aorta
g. unpaired foam
d. everything is correct
3. Specify the structures limiting the costophrenic sinus:
A. costal and diaphragmatic pleura
b. visceral and costal pleura
V. costal and mediastinal pleura
d. diaphragmatic and mediastinal pleura
d. everything is correct
4. Specify the location of the upper interpleural field:
A. behind the pericardium
b. above the sternum
V. behind the manubrium of the sternum
near the spine
d. everything is correct
5. Indicate the places where the projections of the borders of the lungs and pleura coincide:
A. dome of the pleura and apex of the lung
b. posterior border of lung and pleura
V. anterior border of the lung and pleura on the right
d. anterior border of the lung and pleura on the left
d. everything is correct
6. Specify the anatomical formations that are in front of the dome of the pleura:
A. head of 1st rib
b. longus neck muscle
V. subclavian artery
subclavian vein
d. everything is correct
7. Specify the anatomical formations that are behind the dome of the pleura:
A. longus neck muscle
b. posterior scalene muscle
V. head of 1st rib
d. subclavian artery
d. everything is correct
8. Specify the anatomical structures to which the dome of the pleura is fixed:
A. pretracheal plate of the fascia of the neck
b. prevertebral plate of the fascia of the neck
V. longus neck muscle
d. longus capitis
d. everything is correct
9. Specify the anatomical formations that are located in the middle part of the mediastinum:
A. trachea
b. main bronchi
V. pulmonary veins
d. internal mammary arteries and veins
d. everything is correct
10. Specify the organs that are located in the posterior mediastinum
A. main bronchi
b. vagus nerves
V. unpaired and semi-unpaired vein
trachea
d. everything is correct
Sample answers: 1. b, c, d; 2. in; 3. a; 4. in; 5. a, b, c; 6. c, d; 7. a, c; 8. b, c; 9. b, c; 10. b, c.
The trachea is a non-collapsing tube that starts from the lower end of the larynx and goes into the chest cavity, where at the level of the V-VII thoracic vertebrae it is divided into the right and left main bronchi, forming a fork - a bifurcation of the trachea. In the area of division of the trachea, a spur protrudes into its lumen, deviated to the left, so the passage to the right bronchus is wider. There is a short neck part and a longer chest part. The length of the trachea is 8-13 cm, the diameter is 1.5-2.5 cm. In men, the trachea is longer than in women. In newborns, the trachea is relatively short, its bifurcation is at the level of the III-IV thoracic vertebrae and has a fusiform shape. The growth of the trachea is accelerated in the first 6 months, and then slows down until the age of 10 years. By the age of 14-16, the length of the trachea doubles, and by the age of 25 it triples.
The structure of the trachea. The wall of the trachea is formed by 16-20 hyaline tracheal cartilages, which look like incomplete cartilaginous rings. The tracheal cartilages are interconnected by annular ligaments. Behind, between the ends of the tracheal cartilages, a membranous wall of the trachea is formed, consisting of bundles of smooth muscle tissue, located mainly circularly and partially longitudinally. The tracheal muscle causes active changes in the lumen of the trachea during breathing and coughing.
Outside, the trachea is covered with a thin outer connective tissue membrane, and from the inside - with a mucous membrane, which is tightly connected with the tracheal cartilage and ligaments and does not form folds. It is covered, like the larynx, with multi-row ciliated epithelium, between the cells of which there are many goblet mucous cells. In its own layer of the mucous membrane contains protein-mucous tracheal glands and lymphatic follicles.
Topography of the trachea. The trachea is projected at the level from the upper edge of the VII cervical to IV-VII thoracic vertebrae. In people with a wide chest, the projection of the bifurcation of the trachea falls on the VI-VII thoracic vertebrae, and in people with a narrow chest, on V.
The anterior surface of the cervical part of the trachea is adjacent to the isthmus of the thyroid gland, to the sternohyoid and sternothyroid muscles, the posterior one to the esophagus, the lateral ones to the lobes of the thyroid gland and the neurovascular bundles of the neck. The aortic arch with its branches is adjacent to the anterior surface of the thoracic part of the trachea, the esophagus and pericardium to the posterior, the unpaired vein, the right vagus nerve, lymph nodes to the right side, the aortic arch, the left recurrent nerve and lymph nodes to the left side.
The blood supply to the cervical part of the trachea is carried out at the expense of the inferior thyroid arteries. The thoracic part receives branches from the bronchial and esophageal arteries. The outflow of venous blood occurs in the inferior thyroid, unpaired and semi-unpaired veins.
Lymphatic vessels drain lymph into the tracheal and tracheobronchial nodes.
Innervation is carried out by branches of the cervicothoracic nerve plexus.
The main (primary) bronchi, right and left, depart from the trachea, forming its bifurcation, and go to the corresponding lung, where they are divided into bronchi of the second, third and other orders, which, decreasing in caliber, form the bronchial tree. As the bronchi branch out, they lose cartilage, so that the basis of the walls of the small bronchi is predominantly elastic and smooth muscle fibers. The angle between the trachea and the right bronchus is usually 150-160°, and between the trachea and the left bronchus - 130-140°. The right bronchus is shorter and wider than the left. The length of the right bronchus is 1-2 cm, and the diameter is 1.5-2.5 cm. It usually consists of 6-8 cartilaginous rings. The length of the left bronchus is 4-6 cm, and the diameter is 1-2 cm; it is composed of 9-12 cartilaginous rings. Due to the fact that the right bronchus is more vertical and wider than the left, foreign bodies of the respiratory tract often enter the right bronchus. The structure of the bronchi is similar to the structure of the trachea.
In women, the bronchi are somewhat narrower and shorter than in men. In newborns, the bronchi are wide, along with cartilaginous half-rings, hyaline plates are also found. The mucous membrane is thin, covered with cuboidal epithelium. The mucous glands are poorly developed. The bronchi grow especially intensively in the first year of life, and then up to 10 years - more slowly. By the age of 13, the length of the bronchi doubles. After 40 years, the rings begin to calcify slightly.
Topography of the bronchi. The right bronchus, with its upper surface, is adjacent to the unpaired vein and tracheobronchial lymph nodes, the posterior one to the right vagus nerve, its branches and the posterior right bronchial artery, the anterior one to the ascending aorta, anterior bronchial artery and pericardium, the lower one to the bifurcation lymph nodes. The left bronchus is adjacent to the aortic arch from above, from behind - to the descending aorta, the left vagus nerve, its branches and to the esophagus, in front - to the left anterior bronchial artery, tracheobronchial nodes, from below - to the bifurcation lymph nodes.
The device of the respiratory tract provides direct and open communication with atmospheric air, which, in contact with a warm, moist and mucous membrane, is warmed, moistened and freed from dust particles, which move upward with ciliated epithelium and are removed with coughing and sneezing. Microbes here are neutralized by the activity of wandering cells of lymphatic follicles, scattered in many in the mucous membrane.
The smooth muscles of the bronchi are supplied with centrifugal fibers of the vagus and sympathetic nerves. The vagus nerves cause contraction of the bronchial muscles and constriction of the bronchi, while the sympathetic nerves relax the bronchial muscles and dilate the bronchi.
Trachea, trachea, a hollow organ that provides air conduction, its partial warming, moisturizing and the formation of a cough reflex.
Holotopia: located in the neck and in the chest cavity (in the posterior mediastinum).
Skeletotopia:
begins at the level of the lower edge of C6;
at the level of the lower edge of Th4, the trachea forms a bifurcation, bifurcatio tracheae, (a protrusion protrudes into the lumen of the trachea - a keel, carina tracheae).
Sh. Syntopia:
in the cervical part in front and on the side - the thyroid gland and neck muscles lying below the hyoid bone; on the side - the neurovascular bundle of the neck;
in the ore part in front are located: the handle of the sternum, the thymus gland, the left brachiocephalic vein, the aortic arch, the beginning of the brachiocephalic trunk;
behind the trachea lies the esophagus throughout;
IV. Macroscopic structure:
1.By location in the trachea secrete:
a) cervical part, pars cervicalis;
b) the thoracic part, pars thoracica.
2.By structure:
a) cartilaginous part, pars cartilaginea;
cartilaginous semirings, cartilagines tracheales (15-20);
ring ligaments, ligg. annularia, - interconnect cartilagines tracheales;
b) the membranous part, pars membranacea, consists of bundles of smooth muscles, musculi tracheales, and connective tissue, which fill the space between the cartilage semirings and annular ligaments from behind;
v. Microscopic structure:
the mucous membrane, tunica mucosa, is lined with ciliated epithelium;
the submucosa, tela submucosa, is well defined;
The trachea continues into the main bronchi, bronchi principales, which at the gates of the lung branch into lobar bronchi, bronchi lobares.
Main bronchi (right and left), bronchi principales (dexter et sinister):
depart from the trachea at the level of Th4;
bronchus principalis dexter has a more vertical direction; it is shorter and wider than the left; in the direction it is a continuation of the trachea - foreign bodies get into it more often than into the left main bronchus;
above bronchus principalis dexter is v.azygos; below lies a. pulmonalis dextra;
above the bronchus principalis sinister is located a. pulmonalis sinistra et arcus aortae; behind - esophagus et aorta descendens;
the wall of the bronchi principales in its structure resembles the wall of the trachea (contains cartilaginous half rings).
2. Lobar bronchi, bronchi lobares:
in the left lung there are two lobar bronchi (bronchus lobaris superior et bronchus lobaris inferior),
in the right lung there are three lobar bronchi (bronchus lobaris superior, bronchus lobaris medius et bronchus lobaris inferior);
almost completely closed cartilaginous rings are located in the wall of the lobar bronchi.
3. Segmental bronchi, bronchi segmentales, are named according to the segments (in the left - 10, in the right - 11); the cartilage in their wall becomes segmented.
4. Branches of segmental bronchi, rami bronchiales segmentorum (subsegmental bronchi, bronchi subsegmentales):
9-10 branching orders (dichotomous division) in each segment;
the size of cartilaginous fragments decreases in the distal direction.
Lobular bronchus, bronchus lobularis (1000 in each lung), ventilates the lung lobule; cartilage in its wall is represented by single inclusions.
Final (terminal) bronchiole, bronchiola terminalis:
in the terminal bronchioles, smooth muscles predominate in the wall; no cartilage; glands disappear; ciliated epithelium is preserved;
The organ has 3 types of innervation:
afferent (sensory) innervation
efferent parasympathetic innervation
and efferent sympathetic innervation
thoracic n. vagus and as part of n.spinalis.
thoracic n. vagus
from the upper thoracic nodes truncus sympathicus
Trachea(from Greek trachus - rough), being a continuation of the larynx, begins at the level of the lower edge of the VI cervical vertebra and ends at the level of the upper edge of the V thoracic vertebra, where it is divided into two bronchi - right and left. The division of the trachea is called the bifurcatio tracheae. The length of the trachea ranges from 9 to 11 cm, the transverse diameter is on average 15 - 18 mm. Topography of the trachea. The cervical region is covered at the top by the thyroid gland, behind the trachea is adjacent to the esophagus, and on the sides of it are the common carotid arteries. In addition to the isthmus of the thyroid gland, the trachea is also covered in front by mm. sternohyoideus and sternothyroideus, except in the midline, where the inner edges of these muscles diverge. The space between the posterior surface of these muscles with the fascia covering them and the anterior surface of the trachea, spatium pretracheale, is filled with loose fiber and blood vessels of the thyroid gland (a. thyroidea ima and venous plexus). The thoracic trachea is covered in front by the handle of the sternum, thymus, and vessels. The position of the trachea in front of the esophagus is associated with its development from the ventral wall of the foregut. The structure of the trachea. The wall of the trachea consists of 16 - 20 incomplete cartilaginous rings, cartilagines tracheales, connected by fibrous ligaments - ligg. annularia; each ring extends only two-thirds of the circumference. The posterior membranous wall of the trachea, paries membranaceus, is flattened and contains bundles of unstriated muscle tissue that run transversely and longitudinally and provide active movements of the trachea during breathing, coughing, etc. The mucous membrane of the larynx and trachea is covered with ciliated epithelium (with the exception of the vocal cords and part of the epiglottis ) and is rich in lymphoid tissue and mucous glands. The trachea (trachea) has:- cervical part(pars cervicalis; pars colli);- chest part(pars thoracica). The cervical part of the trachea is covered in front with muscles that lie below the hyoid bone (oshyoideum), as well as the isthmus of the thyroid, which corresponds to the level of the second or third half-ring of the trachea. The esophagus (oesophagus) passes behind the trachea (trachea). The thoracic part of the trachea (pars thoracica tracheae) is located in the superior mediastinum (mediastinum superius) Main bronchi, right and left, bronchi principales (bronchus, Greek - breathing tube) dexter et sinister, depart at the bifurcatio tracheae site almost at a right angle and go to the gate of the corresponding lung. The right bronchus is somewhat wider than the left, since the volume of the right lung is larger than the left. At the same time, the left bronchus is almost twice as long as the right, cartilaginous rings in the right 6-8, and in the left 9-12. The right bronchus is located more vertically than the left, and, thus, is, as it were, a continuation of the trachea. Through the right bronchus it is thrown arcuately from back to front v. azygos heading towards v. cava superior, the aortic arch lies above the left bronchus. The mucous membrane of the bronchi is similar in structure to the mucous membrane of the trachea. In a living person during bronchoscopy (i.e., when examining the trachea and bronchi by introducing a bronchoscope through the larynx and trachea), the mucous membrane has a grayish color; cartilaginous rings are clearly visible. The angle at the site of the division of the trachea into the bronchi, which has the form of a ridge protruding between them, carina, should normally be located along the midline and move freely during breathing. main bronchi(bronchi principales) are bronchi first order , the bronchial tree (arbor bronchialis) begins from them. The main bronchi (bronchi principales), entering the gates of the lungs (hilum pulmonum), branch into bronchi of the second order , which ventilate the corresponding lobes of the lungs and are therefore called lobar bronchi ((bronchi lobares). In the left lung (pulmo sinister) there are two lobar bronchi, and in the right there are three lobar bronchi. Lobar bronchi (bronchi lobares) branch into bronchi of the third order, which ventilate the areas of the lungs, which are separated by layers of connective tissue, - lung segments(segmenta pulmonalia). All segmental bronchi (bronchі segmentales) branch dichotomously (that is, each into two) to lobular bronchi(bronchi lobulares), which ventilate the lobules of the lungs. This area is called lung lobule (lobulus pulmonis), and the bronchi that ventilate it are called lobular bronchi(bronchioli lobulares). The lobular bronchus (bronchus lobularis) has a diameter of about 1 mm and enters the top of the lobule (apex lobuli), where it branches into 12–18 terminal bronchioles (bronchioli terminales), which have a diameter of 0.3–0.5 mm their wall no longer has cartilaginous tissue, and the middle layer of the wall is represented only by smooth muscle tissue (textus muscularis glaber). Therefore, small bronchi and terminal bronchioles (bronchioli terminales) perform the function of not only conducting, but also regulating the flow of air into certain sections of the lungs. End | terminal | bronchioles (bronchioli terminales) ends bronchial tree (arbor bronchialis) and the functional unit of the lungs begins, which is called pulmonary acinus ((acinus pulmonalis), which translates as a bunch, or aalveolar tree(arbor alveolaris), there are up to 30,000 of them in the lungs.
64. Trachea and bronchi: topography, structure, functions, blood supply, innervation, regional lymph nodes.
Bronchi Trachea (trachea) (windpipe) - an unpaired organ (10-13 cm), which serves to pass air into the lungs and back, begins at the lower edge of the cricoid cartilage of the larynx. The trachea is formed by 16-20 semirings of hyaline cartilage. The first half ring is connected to the cricoid cartilage by the cricotracheal ligament. Between themselves, the cartilaginous semirings are connected by a dense connective tissue. Behind the rings is a connective tissue membrane (membrane) with an admixture of smooth muscle fibers. Thus, the trachea is cartilaginous in front and laterally, and connective tissue in the back. The upper end of the tube is located at the level of the 6th cervical vertebra. Lower - at the level of 4-5 thoracic vertebrae. The lower end of the trachea is divided into two main primary bronchi, the place of division is called the bifurcation of the trachea. Due to the presence of elastic fibers in the connective tissue between the half rings, the trachea can lengthen when the larynx moves up and shorten when it is lowered. Numerous small mucous glands are located in the submucosal layer.
Bronchi (bronchi) are a continuation of the windpipe both functionally and morphologically. The walls of the main bronchi consist of cartilaginous semirings, the ends of which are connected by a connective tissue membrane. The right main bronchus is shorter and wider. Its length is about 3 cm, consists of 6-8 half rings. The left main bronchus is longer (4-5 cm) and narrower, consists of 7-12 half-rings. The main bronchi enter the gate of the corresponding lung. The main bronchi are the bronchi of the first order. Bronchuses of 2 orders depart from them - lobar (3 in the right lung and 2 in the left), which give segmental bronchi (3 orders), and the latter branch dichotomously. There are no cartilaginous semirings in the segmental bronchi, the cartilage breaks up into separate plates. The segments are formed by pulmonary lobules (up to 80 pieces in 1 segment), which include the lobular bronchus (8th order). In small bronchi (bronchioles) with a diameter of 1-2 mm, cartilaginous plates and glands gradually disappear. Intralobular bronchioles break up into 18-20 terminal (terminal) ones with a diameter of about 0.5 mm. In the ciliated epithelium of the terminal bronchioles, there are separate secretory cells (Clark), which produce enzymes that break down the surfactant. These cells are also a source of restoration of the epithelium of the terminal bronchioles. All bronchi, starting from the main bronchi and including the terminal bronchioles, make up the bronchial tree, which serves to conduct a stream of air during inhalation and exhalation; respiratory gas exchange between air and blood does not occur in them.
65. Lungs: boundaries, structure, blood supply, innervation, regional lymph nodes.
Branching of the terminal bronchiole is the structural unit of the lung acinus. Terminal bronchioles give rise to 2-8 respiratory (respiratory) bronchioles, pulmonary (alveolar) vesicles already appear on their walls. From each respiratory bronchiole, alveolar passages extend radially, blindly ending in alveolar sacs (alveoli). In the walls of the alveolar ducts and alveoli, the epithelium becomes a single-layer flat. In the cells of the alveolar epithelium, a factor is formed that lowers the surface tension of the alveoli - a surfactant. This substance consists of phospholipids and lipoproteins. The surfactant prevents the lungs from collapsing during exhalation, and the surface tension of the alveolar walls prevents the lungs from overstretching during inhalation. During forced inspiration, the elastic structures of the lungs also prevent overstretching of the pulmonary alveoli. The alveoli are surrounded by a dense network of capillaries where gas exchange takes place. The respiratory bronchioles, alveolar ducts, and sacs make up the alveolar tree, or respiratory parenchyma of the lungs. Person 2 lungs (pulmones) - left and right. These are rather voluminous organs, occupying almost the entire volume of the chest, with the exception of its middle part. The lungs are cone shaped. The lower expanded part - the base - is adjacent to the diaphragm and is called the diaphragmatic surface. According to the dome of the diaphragm, there is a recess at the base of the lung. The narrowed rounded upper part - the apex of the lung - exits through the upper opening of the chest into the neck area. In front, it is located 3 cm above the 1st rib, behind its level corresponds to the neck of the 1st rib. On the lung, in addition to the diaphragmatic surface, there is an external convex - costal. On this surface of the lung there are imprints of the ribs. The medial surfaces face the mediastinum and are called mediastinal. In the central part of the mediastinal surface of the lung, its gates are located. The gates of each lung include the primary (main) bronchus, a branch of the pulmonary artery that carries venous blood to the lung, and a small bronchial artery (branch of the thoracic aorta) that carries arterial blood to feed the lung. In addition, the vessels include nerves that innervate the lungs. Two pulmonary veins exit the gates of each lung, which carry arterial blood to the heart, and lymphatic vessels. The bifurcation of the trachea, all structural formations passing through the gates of the lungs, and the lymph nodes together form the root of the lung. At the point of transition of the costal surface of the lung to the diaphragmatic, a sharp lower edge is formed. Between the costal and mediastinal surfaces in front - a sharp edge, behind - blunt, rounded. The lung has deep grooves dividing it into lobes. On the right lung there are two grooves that divide it into three lobes: upper, middle and lower; on the left - one, dividing the lung into two lobes: upper and lower. According to the nature of the branching of the bronchi and blood vessels in each lobe, segments are distinguished. In the right lung, 3 segments are distinguished in the upper lobe, 2 segments in the middle lobe, and 5-6 segments in the lower lobe. In the left lung in the upper lobe - 4 segments, in the lower lobe 5-6 segments. Thus, in the right lung 10-11, in the left 9-10 segments. The left lung is narrower, but longer than the right, the right lung is wider, but shorter than the left, which corresponds to a higher standing of the right dome of the diaphragm due to the liver located in the right hypochondrium.
Blood circulation in the lungs has its own characteristics. In connection with the function of gas exchange, the lungs receive not only arterial, but also venous blood. Venous blood enters through the branches of the pulmonary arteries, each of which enters the gates of the lung and divides to capillaries, where gas exchange occurs between the blood and the air of the alveoli: oxygen enters the blood, and carbon dioxide enters the alveoli from it. The capillaries form the pulmonary veins, which carry arterial blood to the heart. Arterial blood enters the lungs through the bronchial arteries (from the aorta, posterior intercostal and subclavian arteries). They nourish the bronchial wall and lung tissue. From the capillary network, which is formed by branching of these arteries, bronchial veins are collected, flowing into the unpaired and semi-unpaired veins, partly into the pulmonary veins from small bronchioles. Thus, the systems of the pulmonary and bronchial veins anastomose with each other.
The upper parts of the respiratory system are supplied with blood by branches of the external carotid artery (facial, superior thyroid artery, lingual). The nerves of the lungs come from the pulmonary plexus, formed by branches of the vagus nerves and sympathetic trunks.
