In practice great importance has a process of heat transfer through a flat wall, consisting of several layers of material with different thermal conductivity. So, for example, the metal wall of a steam boiler, covered with slag on the outside, and with scale on the inside, is a three-layer wall.
Let us consider the process of heat transfer by thermal conductivity through a flat three-layer wall (Fig. 7). All layers of such a wall are tightly adjacent to each other. The layer thicknesses are designated δ 1, δ 2 and δ 3 and the thermal conductivity coefficients of each material are λ 1, λ 2 and λ 3 respectively. The temperatures of the outer surfaces t l and t 4 are also known. Temperatures t 2 and t 3 are unknown.
The process of heat transfer by thermal conductivity through a multilayer wall is considered in a stationary mode, therefore, the specific heat flux q passing through each layer of the wall is constant in magnitude and the same for all layers, but on its way it overcomes the local thermal resistance δ/λ of each layer of the wall. Therefore, based on formula (54) for each layer, we can write:
Adding the left and right parts of equalities (58), we obtain the total temperature difference, which consists of the sum of temperature changes in each layer:
It follows from equation (59) that the total thermal resistance of a multilayer wall is equal to the sum of the thermal resistances of each layer:
Using formulas (58) and (59), one can obtain the values of unknown temperatures t2 and t3:
 |
The temperature distribution in each layer of the wall at λ-const obeys a linear law, which can be seen from equality (58). For a multilayer wall as a whole, the temperature curve is a broken line (in Fig. 7).
The formulas obtained for a multilayer wall can be used provided there is good thermal contact between the layers. If at least a small air gap appears between the layers, then the thermal resistance will increase markedly, since the thermal conductivity of air is very low:
[λ B03D = 0.023 W/(m deg)].
If the presence of such a layer is unavoidable, then in the calculations it is considered as one of the layers of a multilayer wall.
convective heat transfer. Convective heat transfer is heat exchange between a solid body and a liquid (or gas), accompanied by both heat conduction and convection.
The phenomenon of thermal conductivity in a liquid, as well as in a solid body, is completely determined by the properties of the liquid itself, in particular, the thermal conductivity coefficient and the temperature gradient.
In convection, the transfer of heat is inextricably linked with the transfer of fluid. This complicates the process, since the transfer of fluid depends on the nature and nature of the occurrence of its movement, physical properties liquids, shapes and sizes of surfaces solid body etc.
Consider the case of a liquid flowing near a solid wall, the temperature of which is lower (or higher) than the wall temperature. Heat exchange takes place between the liquid and the wall. The transfer of heat from the wall to the liquid (or vice versa) will be called heat transfer. Newton showed that the amount of heat Q exchanged between each other per unit time by a wall having a temperature T st and a liquid having a temperature T W is directly proportional to the temperature difference T st - T W and the contact surface area S:
Q \u003d αS (T st - T well) (60)
where α is the heat transfer coefficient, which shows how much heat the liquid and the wall exchange during one second, if the temperature difference between them is 1 K, and the surface area washed by the liquid is 1 m 2. In SI, the unit of heat transfer coefficient is W / (m 2 K). The heat transfer coefficient α depends on many factors, and primarily on the nature of the fluid motion.
Turbulent and laminar fluid flow corresponds to a different nature of heat transfer. During laminar motion, heat propagates in a direction perpendicular to the movement of fluid particles, as well as in a solid body, i.e., by heat conduction. Since the coefficient of thermal conductivity of the liquid is small, heat is distributed during laminar flow in the direction perpendicular to the flow, very weakly. During turbulent motion, the fluid layers (more or less heated) are mixed, and the heat exchange between the fluid and the wall under these conditions is more intense than in laminar flow. In the boundary layer of the liquid (near the pipe walls), heat is transferred only by heat conduction. Therefore, the boundary layer represents a large resistance to the flow of heat, and the greatest loss of temperature difference occurs in it.
In addition to the nature of the movement, the heat transfer coefficient depends on the properties of the liquid and solid, the temperature of the liquid, etc. Thus, it is quite difficult to theoretically determine the heat transfer coefficient. Based on a large amount of experimental material, the following values of heat transfer coefficients [in W/(m 2 K)] were found for various cases of convective heat transfer:
Basically, convective heat transfer occurs with a longitudinal forced flow of a liquid, for example, heat transfer between the walls of a pipe and the liquid flowing through it; transverse forced flow, for example, heat transfer during liquid washing of a transverse tube bundle; free movement, such as heat exchange between a fluid and a vertical surface that it washes; a change in the state of aggregation, for example, heat exchange between a surface and a liquid, as a result of which the liquid boils or its vapors condense.
Radiant heat transfer. Radiant heat transfer is the process of transferring heat from one body to another in the form of radiant energy. In heat engineering at high temperatures, heat transfer by radiation is of paramount importance. Therefore, modern heat engineering units, designed for high temperatures, make the most of this type of heat transfer.
Any body whose temperature is different from absolute zero radiates electromagnetic waves. Their energy is able to absorb, reflect, and also pass through itself any other body. In turn, this body also radiates energy, which, together with the reflected and transmitted energy, falls on the surrounding bodies (including the first body) and is again absorbed, reflected by them, etc. Of all the electromagnetic rays, infrared has the greatest thermal effect. and visible rays with a wavelength of 0.4-40 microns. These rays are called heat rays.
As a result of the absorption and emission of radiant energy by bodies, heat exchange occurs between them.
The amount of heat absorbed by a body as a result of radiant heat transfer is equal to the difference between the energy incident on it and radiated by it. Such a difference is non-zero if the temperatures of the bodies participating in the mutual exchange of radiant energy are different. If the temperature of the bodies is the same, then the whole system is in dynamic thermal equilibrium. But even in this case, the bodies still radiate and absorb radiant energy.
The energy emitted by a unit surface of a body per unit time is called its emissivity. The unit of emissivity is W/m a.
If Q 0 energy falls on the body per unit time (Fig. 8), Q R is reflected, Q D passes through it, Q A is absorbed by it, then
| (61) |
where Q A /Q 0 \u003d A is the absorption capacity of the body; Q R /Q o = R - reflectivity of the body; Q D /Q 0 \u003d D is the transmittance of the body.
If A \u003d 1, then R \u003d D \u003d 0, i.e., all the incident energy is completely absorbed. In this case, the body is said to be completely black. If R = 1, then A=D = 0 and the angle of incidence of the rays is equal to the angle of reflection. In this case, the body is absolutely specular, and if the reflection is diffuse (uniform in all directions), it is absolutely white. If D = 1, then A=R= 0 and the body is absolutely transparent. In nature, there are neither absolutely black, nor absolutely white, nor absolutely transparent bodies. Real bodies can only to some extent approach one of these types of bodies.
The absorption capacity of different bodies is different; moreover, the same body absorbs energy of different wavelengths differently. However, there are bodies for which, in a certain range of wavelengths, the absorptivity depends little on the wavelength. Such bodies are commonly referred to as gray bodies for a given wavelength range. Practice shows that in relation to the range of wavelengths used in heat engineering, many bodies can be considered gray.
The energy emitted by a unit surface of a black body per unit time is proportional to the fourth power of the absolute temperature (the Stefan-Boltzmann law):
E 0 \u003d σ "0 T A, where σ" 0 is the radiation constant of a completely black body:
σ "0 \u003d 5.67-10-8 W / (m 2 - K 4).
This law is often written in the form
where is the emissivity of a completely black body; \u003d 5.67 W / (m 2 K 4).
Many of the laws of radiation established for a completely black body have great value for heat engineering. So, the cavity of the furnace of a boiler plant can be considered as a model of a completely black body (Fig. 9). In relation to such a model, the laws of black body radiation are fulfilled with great accuracy. However, these laws should be used with caution in relation to thermal installations. For example, for a gray body, the Stefan-Boltzmann law has a form similar to formula (62):
 | (63) |
where The ratio / is called the degree of emissivity ε (ε is the greater, the more the body under consideration differs from absolute black, Table 4).
Formula (63) is used to determine the emissivity of the furnaces, the surface of the burning fuel layer, etc. The same formula is used when taking into account the heat transferred by radiation in the combustion chamber, as well as by the elements of the boiler unit.
The bodies filling the interior of the furnace continuously radiate and absorb energy. However, the system of these bodies is not in a state of thermal equilibrium, since their temperatures are different: in modern boilers, the temperature of the pipes through which water and steam pass is much lower than the temperature of the furnace space and the inner surface of the furnace. Under these conditions, the emissivity of the pipes is much less
Table 4
emissivity of the furnace and its walls. Therefore, the heat exchange by radiation passing between them is carried out mainly in the direction of energy transfer from the furnace to the surface of the pipes.
During radiant heat exchange between two parallel surfaces with degrees of emissivity ε 3 and ε 2 having temperatures T 1 and T 2 , respectively, the amount of energy they exchange is determined by the formula
If the bodies between which radiative heat exchange occurs are limited by surfaces and S 1 and S 2 located inside each other, then the reduced radiation coefficient is determined by the formula
 | (66) |
Heat transfer
Heat exchange between hot and cold media through a separating solid wall is one of the most important and frequently used processes in engineering. For example, obtaining a steam of given parameters in boiler units is based on the process of heat transfer from one coolant to another. In numerous heat exchange devices used in any industry, the main working process is the process of heat exchange between heat carriers. This heat transfer is called heat transfer.
For example, consider a single-layer (Fig. 10) wall, the thickness of which is equal to δ. The coefficient of thermal conductivity of the wall material is equal to λ. The temperatures of the media washing the wall on the left and right are known and equal to t 1 and t 2 . We accept that t 1 >t 2 . Then the temperatures of the wall surfaces will be respectively t st1 > /t st2. It is required to determine the heat flux q passing through the wall from the heating medium to the heated medium.
Since the heat transfer process under consideration proceeds in a stationary mode, the heat given to the wall by the first heat carrier (hot) is transferred through it to the second heat carrier (cold). Using formula (54), we can write:
Adding these equalities, we get the total temperature difference:
The denominator of equality (68) is the sum of thermal resistances, which consists of the thermal conductivity thermal resistance δ/λ and two thermal heat transfer resistances l/α 1 and 1/α 2 .
We introduce the notation
The value of k is called the heat transfer coefficient.
The reciprocal of the heat transfer coefficient is called the total thermal resistance to heat transfer:
 | (71) |
Trakt. The length of the stomach is about 26 centimeters. Its volume is from one to several liters, it depends on the age and preferences of the person in food. If we project its location onto abdominal wall, then it is located in the epigastric region. The structure of the stomach can be divided into sections and layers.
The structure of the stomach is divided into four sections.
Cardiac
This is the first section. The place where the esophagus communicates with the stomach. The muscle layer of this department forms a sphincter, which prevents reverse course food.
Fornix (bottom) of the stomach
It has a domed shape, it accumulates air. This section contains glands that secrete gastric juice with hydrochloric acid.
The largest section of the stomach. It is located between the pylorus and the bottom.
Pyloric department (pylorus)
The last section of the stomach. It has a cave and a canal. In the cave there is an accumulation of food, which is partially digested. The sphincter is located in the channel, through which food enters the next section of the digestive tract (duodenum). Also, the sphincter prevents the return of food from the intestine to the stomach and vice versa.
The structure of the stomach
It is exactly the same as that of all hollow organs. gastrointestinal tract. There are four layers in the wall. The structure of the stomach is provided so as to perform its main functions. We are talking about digestion, mixing food, partial absorption).
Layers of the stomach
Slime layer
It completely lines the inner surface of the stomach. The entire mucous layer is covered with cylindrical cells that produce mucus. It protects the stomach from the effects of hydrochloric acid due to its bicarbonate content. On the surface of the mucous layer there are pores (mouth glands). also in mucous layer secrete a thin layer of muscle fibers. These fibers form folds.
Submucosal layer
Consists of loose connective tissue, blood vessels and nerve endings. Thanks to him, there is a constant nutrition of the mucous layer and its innervation. Nerve endings regulate the digestive process.
Muscular layer (framework of the stomach)
It is represented by three rows of multidirectional muscle fibers, due to which food is promoted and mixed. The nerve plexus (Auerbach's), which is located here, is responsible for the tone of the stomach.
Serous
This is the outer layer of the stomach, which is a derivative of the peritoneum. It looks like a film that produces a special liquid. Thanks to this fluid, friction between organs is reduced. This layer contains nerve fibers that are responsible for pain symptom that occurs when various diseases stomach.
Glands of the stomach
As already mentioned, they are located in the mucous layer. They have a sac-like shape, due to which they go deep into the submucosal layer. From the mouth of the gland, epithelial cells migrate, which contribute to the constant restoration of the mucous layer. The walls of the gland are represented by three types of cells, which in turn produce hydrochloric acid, pepsin and biologically active substances.
On this topic...
The walls of the heart are made up of three layers:
- endocardium- thin inner layer;
- myocardium- thick muscle layer;
- epicardium- a thin outer layer, which is the visceral sheet of the pericardium - the serous membrane of the heart (heart sac).
Endocardium lines the cavity of the heart from the inside, exactly repeating its complex relief. The endocardium is formed by a single layer of flat polygonal endotheliocytes located on a thin basement membrane.
Myocardium formed by the cardiac striated muscle tissue and consists of cardiac myocytes interconnected by a large number of jumpers, with the help of which they are connected into muscle complexes that form a narrow-loop network. Such a muscular network provides rhythmic contraction of the atria and ventricles. At the atria, the thickness of the myocardium is the smallest; in the left ventricle - the greatest.
atrial myocardium separated by fibrous rings from the myocardium of the ventricles. The synchrony of myocardial contractions is provided by the conduction system of the heart, which is the same for the atria and ventricles. In the atria, the myocardium consists of two layers: superficial (common to both atria), and deep (separate). In the superficial layer, the muscle bundles are located transversely, in the deep layer - longitudinally.
Myocardium of the ventricles consists of three different layers: outer, middle and inner. In the outer layer, the muscle bundles are oriented obliquely, starting from the fibrous rings, continuing down to the apex of the heart, where they form a heart curl. Inner layer myocardium consists of longitudinally arranged muscle bundles. Due to this layer, papillary muscles and trabeculae are formed. The outer and inner layers are common to both ventricles. The middle layer is formed by circular muscle bundles, separate for each ventricle.
epicardium It is built according to the type of serous membranes and consists of a thin plate of connective tissue covered with mesothelium. The epicardium covers the heart, the initial sections of the ascending aorta and pulmonary trunk, the final sections of the caval and pulmonary veins.
Atrial and ventricular myocardium
- atrial myocardium;
- left ear;
- ventricular myocardium;
- left ventricle;
- anterior interventricular sulcus;
- right ventricle;
- pulmonary trunk;
- coronal furrow;
- right atrium;
- superior vena cava;
- left atrium;
- left pulmonary veins.
The wall of the heart consists of three layers: the outer one - the epicardium, the middle one - the myocardium and the inner one - the endocardium.
Name the branches of the aortic arch
1.shoulder head trunk
2.left common carotid artery
3. left subclavian artery
List the branches of a. mesenterica superior and name the areas of their branching.
superior mesenteric artery, a. mesenterica superior, departs from the abdominal part of the aorta behind the body of the pancreas at the level of the XII thoracic - I lumbar vertebra. This artery gives off the following branches:
1) lower pancreat and duodenal arteries, aa. pancreaticoduodenales inferiores, depart from the top mesenteric artery
2) jejunal arteries, aa. jejunales, And ileo-intestinal arteries, aa. iledles, depart from the left semicircle of the superior mesenteric artery.
3) ileocolic-intestinal artery, A. ileocolica, gives back anterior and posterior cecum arteries, aa. caecdles anterior et posterior, and artery appendix, a. appendicularis, And colonic branch, g. colicus, to the ascending colon;
4) right colic artery, a. colica dextra, starts a little higher than the previous one.
5) middle colic artery, a. colica media, departs from the superior mesenteric artery.
Name the branches of the popliteal artery.
Branches of the popliteal artery:
1. Lateral superior genicular artery, a. genus superior lateralis, blood supply to the broad and biceps muscles of the thigh and is involved in the formation of the knee articular network that feeds the knee joint.
2. Medial superior genicular artery, a. genus superior medialis, blood supply to the vastus medialis muscle of the thigh.
3. Middle knee artery, a. media genus, blood supply to the cruciate ligaments and menisci isinovial folds of the capsule.
4. Lateral inferior genicular artery, a. genus inferior lateralis, blood supply to the lateral head calf muscle and plantar muscle.
5. Medial inferior genicular artery, a. genus inferior medialis, blood supply to the medial head of the gastrocnemius muscle and is also involved in the formation knee articular network, rete articulare genus.
Ticket 3
1. What separates the right atrioventricular valve? indicate its folds
The right atrioventricular orifice is closed by the right atrioventricular valve.
It consists of 3 wings:
1.front flap
2.back
3.cloisonné
2. Name the branches of a.femoralis and the areas where they go
femoral artery,a. femoralis, is a continuation of the external iliac artery. Branches from the femoral artery:
1. Superficial epigastric artery,a. epigastric superficialis, blood supply to the lower part of the aponeurosis of the external oblique muscle of the abdomen, subcutaneous tissue and skin.
2. superficial artery circumflex of the ilium,a. circumflexa iliaca superjicialis, goes in a lateral direction parallel inguinal ligament to the superior anterior iliac spine, branches in the adjacent muscles and skin.
3. External pudendal arteries,aa. pudendae externa, exit through the subcutaneous fissure (hiatus saphenus) under the skin of the thigh and go to the scrotum - anterior scrotal branches, rr. scrotdles anteriors, in men or to the labia majora anterior labial branches, rr. labidles anteriores, among women.
4. Deep artery hips, a. profunda femoris, supplies blood to the thigh. The medial and lateral arteries depart from the deep artery of the thigh.
1) Medial circumflex artery femur, a. circumflexa femoris medialis, gives back ascending and deep branches, rr. ascendens et profundus, to iliopsoas, pectineus, obturator externus, piriformis and quadratus femoris muscles. The medial circumflex artery of the femur sends acetabular branch, g. acetabuldris, To hip joint.
2) Lateral circumflex artery of the femur, a. circumflexa femoris latertis, his ascending branch, r. ascendens, blood supply to the gluteus maximus muscle and tensor fascia lata. Descending and transverse branches, rr. descendens and transversus, blood supply to the muscles of the thigh (tailor and quadriceps).
3) Perforating arteries, aa. perfordntes(first, second and third), supply blood to the biceps, semitendinosus and semimembranosus muscles.
3.List the branches of a.mesenterica inferior and name their branching areas.
inferior mesenteric artery,a. mesenterica inferior, starts from the left semicircle of the abdominal part of the aorta at the level of the III lumbar vertebra, gives a number of branches to the sigmoid, descending colon and the left part of the transverse colon. A number of branches depart from the inferior mesenteric artery:
1) left colic artery, a. colica sinistra, Feeds the descending colon and the left section of the transverse colon.
2) sigmoid arteries, aa. sigmoideae, heading towards sigmoid colon;
3) superior rectal artery, a. rectalis superior, blood supply to the upper and middle sections of the rectum.
4. Name the branches of a thoracica interna
internal thoracic artery,a. thoracica interna, departs from the lower semicircle of the subclavian artery, splits into two terminal branches - the muscular-diaphragmatic and superior epigastric arteries. A number of branches depart from the internal mammary artery: 1) mediastinal branches, rr. mediastindles; 2) thymic branches, rr. thymici; 3) bronchial And tracheal branches, rr. bronchiales and tracheales; 4) pericardial diaphragmatic artery, a.pericardiacophrenica; 5) sternal branches, rr. sternales; 6) perforating branches, rr. perfordntes; 7) anterior intercostal branches, rr. intercosldles anteriores; 8) musculophrenic artery, a. muscutophrenica; 9) superior epigastric artery, a. epigdstrica superior.
5. Projection of the heart valves on the anterior chest wall.
Projection mitral valve located on the left above the sternum in the area of attachment of the 3rd rib, the tricuspid valve - on the sternum, in the middle of the distance between the place of attachment to the sternum of the cartilage of the 3rd rib on the left and the cartilage of the 5th rib on the right. The valve of the pulmonary trunk is projected in the II intercostal space to the left of the sternum, the aortic valve - in the middle of the sternum at the level of the third costal cartilages. The perception of sounds arising in the heart depends on the proximity of the projections of the valves, where sound vibrations are manifested, on the conduction of these vibrations along the blood flow, adherence to chest of the part of the heart in which these vibrations are formed. This allows you to find certain areas on the chest, where the sound phenomena associated with the activity of each valve are better heard.
Middle layer of the heart wall myocardium,myocardium, is formed by cardiac striated muscle tissue and consists of cardiac myocytes (cardiomyocytes).
The muscle fibers of the atria and ventricles begin from fibrous rings that completely separate the atrial myocardium from the ventricular myocardium. These fibrous rings are part of its soft skeleton. The skeleton of the heart includes: interconnected right And left fibrous rings, anuli fibrosi dexter et sinister, which surround the right and left atrioventricular openings; right And left fibrous triangles, trigonum fibrosum dextrum et trigonum fibrosum sinistrum. The right fibrous triangle is connected to the membranous part of the interventricular septum.
atrial myocardium separated by fibrous rings from the myocardium of the ventricles. In the atria, the myocardium consists of two layers: superficial and deep. The first contains muscle fibers located transversely, and the second contains two types of muscle bundles - longitudinal and circular. Longitudinally lying bundles of muscle fibers form the pectinate muscles.
Myocardium of the ventricles consists of three different muscle layers: external (superficial), medium and internal (deep). The outer layer is represented by muscle bundles of obliquely oriented fibers, which, starting from the fibrous rings, form curl of the heart, vortex cordis, and pass into the inner (deep) layer of the myocardium, the fiber bundles of which are located longitudinally. Due to this layer, papillary muscles and fleshy trabeculae are formed. The interventricular septum is formed by the myocardium and the endocardium covering it; the basis of the upper section of this septum is a plate of fibrous tissue.
conduction system of the heart. The regulation and coordination of the contractile function of the heart is carried out by its conducting system. These are atypical muscle fibers (cardiac conductive muscle fibers), consisting of cardiac conductive myocytes, richly innervated, with a small number of myofibrils and an abundance of sarcoplasm, which have the ability to conduct irritation from the nerves of the heart to the atrial and ventricular myocardium. The centers of the conduction system of the heart are two nodes: 1) sinoatrial node, nodus si-nuatridlis, located in the wall of the right atrium between the opening of the superior vena cava and the right ear and giving branches to the atrial myocardium, and 2) atrioventricular node, nodus atrioveniricularis, lying in the thickness of the lower part of the interatrial septum. From top to bottom, this node passes into atrioventricular bundle, fasciculus atrioventricularis, which connects the atrial myocardium with the ventricular myocardium. In the muscular part of the interventricular septum, this bundle is divided into the right and left legs, crus dextrum et crus sinistrum. The terminal branches of the fibers (Purkinje fibers) of the conduction system of the heart, into which these legs break up, end in the myocardium of the ventricles.
Pericardium(pericardium), pericardium, delimits the heart from neighboring organs. It consists of two layers: outer - fibrous and inner - serous. outer layer - fibrous pericardium,pericardium fibrosum, near the large vessels of the heart (at its base) passes into their adventitia. serous pericardium,pericardium serosum, has two plates - parietal, lamina parietalis, which lines the fibrous pericardium from the inside, and the visceral, lamina visceralis (epicdrdium), which covers the heart, being its outer shell - the epicardium. The parietal and visceral plates merge into each other at the base of the heart. Between the parietal plate of the serous pericardium from the outside and its visceral plate there is a slit-like space - pericardial cavity,cavitas pericardidis.
The pericardium is divided into three sections: front- sternocostal, which is connected to the posterior surface of the anterior chest wall sternopericardial ligaments, ligamenta sternopericardidca, occupies the area between the right and left mediastinal pleura; lower - diaphragmatic, fused with the tendon center of the diaphragm; mediastinal department (right and left) - the most significant in length. From the lateral sides and in front, this section of the pericardium is tightly fused with the mediastinal pleura. The phrenic nerve and blood vessels pass between the pericardium and pleura on the left and right. Behind the mediastinal pericardium is adjacent to the esophagus, thoracic aorta, unpaired and semi-unpaired veins, surrounded by loose connective tissue.
There are sinuses in the pericardial cavity between it, the surface of the heart and large vessels. First of all, this transverse sinus of the pericardium,sinus transversus pericardium, located at the base of the heart. In front and above, it is limited by the initial section of the ascending aorta and the pulmonary trunk, and behind - by the anterior surface of the right atrium and the superior vena cava. oblique sinus of the pericardium,sinus obliquus pericdrdii, located on the diaphragmatic surface of the heart, limited by the base of the left pulmonary veins on the left and the inferior vena cava on the right. The anterior wall of this sinus is formed by the posterior surface of the left atrium, the posterior by the pericardium.
General anatomy of blood vessels. Patterns of distribution of arteries in hollow and parenchymal organs. Main, extraorganic, intraorganic vessels. microcirculation.
arteries of the heart move away from aortic bulbs, bulbils aortae,- the initial expanded section of the ascending aorta and surround the heart, in connection with which they are called the coronary arteries. The right coronary artery begins at the level of the right sinus of the aorta, and the left coronary artery - at the level of its left sinus. Both arteries depart from the aorta below the free (upper) edges of the semilunar valves, therefore, during contraction (systole) of the ventricles, the valves cover the openings of the arteries and almost do not let blood flow to the heart. With relaxation (diastole) of the ventricles, the sinuses fill with blood, blocking its path from the aorta back to the left ventricle, and suddenly open the access of blood to the vessels of the heart.
right coronary artery, a. coronaria dexira. The largest branch of the right coronary artery is posterior interventricular branch, r. interventricularis posterior. The branches of the right coronary artery supply the wall of the right ventricle and atrium, the posterior part of the interventricular septum, the papillary muscles of the right ventricle, the posterior papillary muscle of the left ventricle, the sinoatrial and atrioventricular nodes of the cardiac conduction system.
left coronary artery,a. coronaria sinistra.It is divided into two branches:anterior interventricular branch, r. interventricularis anterior, And envelope branch, r. circumflexus. The branches of the left coronary artery supply the wall of the left ventricle, including the papillary muscles, most of the interventricular septum, the anterior wall of the right ventricle, and the wall of the left atrium.
Patterns of arterial branching in organs are determined by the plan of the structure of the organ, the distribution and orientation of bundles of connective tissue in it.
Veins of the heart more numerous than arteries. Most of the large veins of the heart are collected in one common wide venous vessel - coronary sinus,sinus corondrius. The tributaries of the coronary sinus are 5 veins: 1) great vein of the heartv. cordis magna, which begins in the region of the apex of the heart on its anterior surface. The vein collects blood from the veins of the anterior surface of both ventricles and the interventricular septum. IN big vein hearts also flow into the veins of the posterior surface of the left atrium and left ventricle; 2) middle vein of the heart,v. cordis Media, is formed in the region of the posterior surface of the apex of the heart and flows into the coronary sinus; 3) small vein hearts,v. cordis Parva, begins on the right pulmonary surface of the right ventricle and flows into the coronary sinus; it collects blood mainly from the right half of the heart; 4) posterior vein of the left ventriclev. posterior ventriculi sinistri, it is formed from several veins on the posterior surface of the left ventricle and flows into the coronary sinus or into a large vein of the heart; 5) oblique vein of the left atrium,v. obliqua dtrii sinistri, follows from top to bottom along the posterior surface of the left atrium and flows into the coronary sinus.
In addition to the veins that flow into the coronary sinus, the heart has veins that open directly into the right atrium. This anterior veins of the heartvv. cordis anteriores andsmallest veins of the heart, vv. cordis minimae, begin in the thickness of the walls of the heart and flow directly into the right atrium and partially into the ventricles and left atrium through openings of the smallest veins, foramina vendrum minimdrum.
cardiac nerves(upper, middle and lower cervical, as well as thoracic) start from the cervical and upper thoracic (II-V) nodes of the right and left sympathetic trunks. Cardiac branches originate from the right and left vagus nerves.
Superficial extraorganic cardiac plexus lies on the anterior surface of the pulmonary trunk and on the concave semicircle of the aortic arch; deep extraorganic cardiac plexus located behind the aortic arch. The upper left cervical cardiac nerve (from the left upper cervical sympathetic ganglion) and the upper left cardiac branch (from the left vagus nerve). All other cardiac nerves and cardiac branches mentioned above enter the deep extraorganic cardiac plexus.
Branches of extraorganic cardiac plexuses pass into a single intraorganic cardiac plexus. It is conventionally subdivided subepicardial, intramuscular and subendocardial plexuses. There are six subepicardial cardiac plexuses: right anterior, left anterior, anterior atrial plexus, right posterior plexus, left posterior plexus, and posterior plexus of the left atrium.
Between the arteries and veins is the distal part of the cardiovascular system - microvasculature, which is the path of local blood flow, where the interaction of blood and tissues is ensured.
Systemic circulation begins in the left ventricle, from where the aorta exits, and ends in the right atrium, into which the superior and inferior vena cava flow. By aoota and its branches arterial blood goes to all parts of the body. Each organ has one or more arteries. Veins emerge from the organs, which form the superior and inferior vena cava, which flow into the right atrium. Between the arteries and veins is the distal part of the cardiovascular system - the microvasculature, which is the path of local blood flow, where the interaction of blood and tissues is ensured. The microcirculatory bed begins with the smallest arterial vessel- arteriole. It includes a capillary link (precapillaries, capillaries and postcapillaries), from which venules are formed. Within the limits of the microcirculatory bed, there are vessels of direct passage of blood from arterioles to venules - arteriovenular anastomoses.
Usually a vessel approaches the capillary network arterial type(arteriole), and venule comes out of it. For some organs (kidney, liver), there is a deviation from this rule. So, an artery approaches the glomerulus of the renal corpuscle - the bringing vessel, vas afferens. An artery also leaves the glomerulus - the efferent vessel, vas effects. A capillary network inserted between two vessels of the same type (arteries) is called arterial miraculous network, rete mirabile arteriosum. According to the type of a wonderful network, a capillary network is built, located between the interlobular and central veins in the liver lobule, - venous miraculous network, rete mirabile venosum.
Small circle of blood circulation begins in the right ventricle, from which the pulmonary trunk emerges, and ends in the left atrium, where the pulmonary veins flow. Venous blood flows from the heart to the lungs (pulmonary trunk), and arterial blood flows to the heart (pulmonary veins). Therefore, the pulmonary circulation is also called pulmonary.
From the aorta (or from its branches) all the arteries of the systemic circulation begin. Depending on the thickness (diameter), the arteries are conditionally divided into large, medium and small. Each artery has a main trunk and its branches.
