Histological structure of blood vessels in women. Private histology of the cardiovascular system. A. Vessels of the ICR. Arterioles, capillaries, venules

Micropreparation Instructions

A. Vessels of the ICR. Arterioles, capillaries, venules.

Staining - hematoxylin-eosin.

In order to determine the relationship between the links of the microvasculature, it is necessary to stain and examine the total, film preparation, where the vessels are visible not on the cut, but as a whole. We select an area with small vessels on the preparation so that their connection with the capillaries is visible.

Arterioles as the first link in the microvasculature are recognizable by the characteristic placement of smooth myocytes. Light elongated oval nuclei of endotheliocytes shine through the wall of arterioles. Their long axis coincides with the course of the arteriole.

Venules have a thinner wall, darker nuclei of endotheliocytes and several rows of red erythrocytes in the lumen.

Capillaries are thin vessels, have the smallest diameter and the thinnest wall, which includes one layer of endotheliocytes. Erythrocytes are located in the lumen of the capillary in one row. You can also see the places where the capillaries depart from the arterioles and where the capillaries enter the venules. Between the vessels contains loose fibrous connective tissue of a typical structure.

1. On the electron diffraction pattern of the capillary, fenestrae in the endothelium and pores in the basement membrane are clearly defined. Name the type of capillary.

A. Sinusoidal.

B. Somatic.

C. Visceral.

D. Atypical.

E. Shunt.

2. I.M. Sechenov called arterioles "faucets" of the cardiovascular system. What structural elements provide this function of arterioles?

A. Circular myocytes.

B. Longitudinal myocytes.

C. Elastic fibers.

D. Longitudinal muscle fibers.

E. Circular muscle fibers.

3. An electron micrograph of a capillary with a wide lumen clearly shows fenestrae in the endothelium and pores in the basement membrane. Determine the type of capillary.

A. Sinusoidal.

B. Somatic.

C. Atypical.

D. Shunt.

E. Visceral.

4. The presence of what type of capillaries is typical for the microvasculature of the human hematopoietic organs?

A. Perforated.

B. Fenestrated.

C. Somatic.

D. Sinusoidal.

5. In the histological preparation, vessels are found that start blindly, look like flattened endothelial tubes, do not contain a basement membrane and pericytes, the endothelium of these vessels is fixed by tropic filants to the collagen fibers of the connective tissue. What are these vessels?

A. Lymphocapillaries.

B. Hemocapillaries.

C. Arterioles.

D. Venules.

E. Arterio-venular anastomoses.

6. The capillary is characterized by the presence of fenestrated epithelium and a porous basement membrane. Type of this capillary:

A. Sinusoidal.

B. Somatic.

C. Visceral.

D. Lacunar.

E. Lymphatic.

7. Name the vessel of the microvasculature, in which the subendothelial layer is weakly expressed in the inner shell, the inner elastic membrane is very thin. The middle shell is formed by 1-2 layers of spirally directed smooth myocytes.

A. Arteriole.

B. Venule.

C. Somatic type capillary.

D. Fenestrated type capillary.

E. Sinusoidal capillary.

8. In which vessels is the largest common surface observed, which creates optimal conditions for bilateral metabolism between tissues and blood?

A. Capillaries.

B. Arteries.

D. Arterioles.

E. Venules.

9. An electron micrograph of a capillary with a wide lumen clearly shows fenestrae in the endothelium and pores in the basement membrane. Determine the type of capillary.

A. Sinusoidal.

B. Somatic.

C. Atypical.

D. Shunt.

E. Visceral.

Supplement P

(mandatory)

Histofunctional features of MCR vessels

in questions and answers

1. What are the functional links of the ICR?

A. The link in which the regulation of blood flow to the organs occurs. It is represented by arterioles, metarterioles, precapillaries. All of these vessels contain sphincters, the main components of which are circularly located SMCs.

B. Another link is the vessels, which are responsible for the metabolism and gases in the tissues. These vessels are capillaries. The third link is the vessels that provide the drainage-depositing function of the MCR. These include venules.

2. What are the structural features of arterioles?

Each shell consists of one layer of cells. Myocytes in the middle shell form an inclined spiral, located at an angle of more than 45 degrees. Myoendothelial contacts are formed between myocytes and endothelium. Arterioles do not have an elastic membrane.

3. What are the histofunctional features of precapillaries?

Myocytes along the precapillary are at a considerable distance. Instead of the branching of precapillaries from arterioles and the branching of precapillaries into capillaries, there are sphincters in which SMCs are arranged circularly. Sphincters provide selective distribution of blood between the exchange links of the ICR. It should also be noted that the lumen of open precapillaries is smaller than that of capillaries, which can be compared to the bottleneck effect.

4. What are the histofunctional features of arteriolo-venular anastomoses? (addition 7 traits 3)

There are two groups of anastomoses:

1) true (shunts);

2) atypical (semi-shunts).

True shunts carry arterial blood. By structure, true shunts are:

1) simple, where there are no additional contractile apparatuses, that is, the regulation of blood flow is carried out by the SMC of the middle shell of the arteriole;

2) with special contractile apparatus in the form of rollers or pads in the subendothelial layer, which protrude into the lumen of the vessel.

Mixed blood flows through atypical (semi-shunts). By structure, they are a connection of arterioles and venules through a short capillary, the diameter of which is up to 30 microns.

Arterio-venular anastomoses are involved in the regulation of blood supply to organs, local and general blood pressure, and in the mobilization of blood deposited in venules.

Significant role of ABA in the body's compensatory reactions in circulatory disorders and the development of pathological processes.

5. What are the structural bases of hematotissue interaction?

The main component of hematotissue interaction is the endothelium, which is a selective barrier and is also adapted to metabolism. In addition, the control of transcellular and intracellular transport is ensured by the multimembrane principle of cell organization and the dynamic properties of cell membranes.

Annex 2. Table 1– Types of capillaries

Appendix 3. Table 2 - Types of venules

Appendix 4

Picture 1–Types of capillaries (scheme according to Yu.I. Afanasiev):

I-hemocapillary with continuous endothelial lining and basement membrane; II - hemocapillary with fenestrated endothelium and a continuous basement membrane; III-hemocapillary with slit-like holes in the endothelium and a discontinuous basement membrane; 1-endotheliocyte; 2-basement membrane; 3-fenestra; 4-slits (pores); 5-pericite; 6-adventitial cell; 7-contact of endotheliocyte and pericyte; 8-nerve ending

Annex 5

Anterior capillary sphincters

Figure 2–Components of the ICR (according to V. Zweifach):

scheme of vessels of various types that form the terminal vascular bed and regulate microcirculation in it.

Appendix 6

Figure 3–Arterio-venular anastomoses (ABA) (scheme according to Yu.I. Afanasiev):

I-ABA without a special locking device: I-arteriole; 2-venule; 3-anastomosis; 4-smooth myocytes of the anastomosis; II-ABA with a special locking device: A-anastomosis of the type of the locking artery; B-simple anastomosis of the epithelioid type; B-complex anastomosis of the epithelioid type (glomerular): G-endothelium; 2-longitudinally placed bundles of smooth myocytes; 3-inner elastic membrane; 4-arteriole; 5-venule; 6-anastomosis; 7-epithelial cells of the anastomosis; 8 capillaries in the connective tissue sheath; III-atypical anastomosis: 1-arteriole; 2-short hemocapillary; 3-venule

Appendix 8

Figure 4

Annex 9

Figure 5

Module 3. Special histology.

"Special histology of sensory and regulatory systems"

Topic of the lesson

"Heart"

Relevance of the topic. A detailed study of the morphological and functional characteristics of the heart in a normal state predetermines the possibilities of prevention, early diagnosis of structural and functional disorders of the heart. Knowledge of the histological features of the heart muscle helps to understand and explain the pathogenesis of heart disease.

General purpose of the lesson. Be able to:

1. Diagnose structural elements of the heart muscle on micropreparations.

specific goals. Know:

1. Features of the structural and functional organization of the heart.

2. Morphofunctional organization of the conducting system of the heart.

3. Microscopic, ultramicroscopic structure and histophysiology of the heart muscle.

4. The course of the processes of embryonic development, age-related changes and regeneration of the heart.

Initial level of knowledge-skills. Know:

1. Macroscopic structure of the heart, its membranes, valves.

2. Morphofunctional organization of the heart muscle (department of human anatomy).

After mastering the necessary basic knowledge, proceed to the study of the material that you can find in the following sources of information.

A. Basic literature

1. Histology / ed. Yu.I.Afanasiev, N.A.Yurina. - Moscow: Medicine, 2002. - S. 410-424.

2. Histology / ed. V. G. Eliseeva, Yu.

3. Atlas of histology and embryology / ed. I.V. Almazova, L.S. Sutulova. – M.: Medicine, 1978.

4. Histology, cytology and embryology (atlas for independent work of students) / ed. Yu.B.Tchaikovsky, L.M.Sokurenko - Lutsk, 2006.

5. Methodological developments for practical exercises: in 2 parts. - Chernivtsi, 1985.

B. Further Reading

1. Histology (introduction to pathology) / ed. E.G. Ulumbekova, prof. Yu.A. Chelysheva. - M., 1997. - S. 504-515.

2. Histology, cytology and embryology (atlas) / ed. O.V.Volkova, Yu.K.Eletsky - Moscow: Medicine, 1996. - S. 170–176.

3. Private human histology / ed. V.L. Bykov. - SOTIS: St. Petersburg, 1997. - S. 16-19.

B. Lectures on the topic.

Theoretical questions

1. Sources of development of the heart.

2. General characteristics of the structure of the heart wall.

3. Micro and submicroscopic structure of the endocardium and heart valves.

4. Myocardium, micro and ultrastructures of typical cardiomyocytes. Leading system of the heart.

5. Morphofunctional characteristics of atypical myocytes.

6. The structure of the epicardium.

7. Innervation, blood supply and age-related changes in the heart.

8. Modern concepts of heart regeneration and transplantation.

Brief guidelines for work

in a practical session

Homework will be checked at the beginning of the class. Then, on your own, you must study such a micropreparation as the wall of a bull's heart. You perform this work according to the algorithm for studying micropreparations. During independent work, you can consult with a teacher about certain issues on micropreparations.

Technological map of the lesson

To consolidate the material, complete the tasks:

To the structures indicated by numbers, select the descriptions that correspond to them in morphology and function. Name the cell and the labeled structures:

a) these structures are located along the muscle fiber and have anisotropic and isotropic bands (or discs A and I);

b) general-purpose membrane organelles that form and store energy in the form of ATP;

c) a system of components of various shapes, which ensures the transport of calcium ions;

d) a system of narrow tubules, which branches in the muscle fiber and ensures the transmission of a nerve impulse;

e) membrane organelles of general purpose, providing cellular digestion;

f) dark stripes running across the fiber contain three types of intercellular contacts: g) desmosomal; h) nexus; i) adhesive.

Questions for test control

1. What is the main function of the heart?

2. When does the laying of the heart occur?

3. What is the source of endocardial development?

4. What is the source of myocardial development?

5. What is the source of development of the epicardium?

6. When does the formation of the conducting system of the heart begin?

7. What is the name of the inner shell of the heart?

8. Which of the following layers is not part of the endocardium?

9. Which layer of the endocardium has vessels?

10. How is the endocardium nourished?

11. What cells are abundant in the subendothelial layer of the endocardium?

12. What tissue is the basis of the structure of the heart valves?

13. What are the valves of the heart covered with?

14. What does the myocardium consist of?

15. The heart muscle consists of ...

16. Myocardium by structure refers to ...

17. What are myocardial muscle fibers formed by?

18. What is not typical for cardiomyocytes?

19. What is characteristic of the heart muscle?

20. What shell of the heart consists of cardiomyocytes?

21. What is the source of development of cardiomyocytes?

22. What types of cardiomyocytes are divided into?

23. What is not typical for the structure of cardiomyocytes?

24. How do cardiac muscle T-tubules differ from skeletal muscle T-tubules?

25. Why is there no typical pattern of triads in contractile cardiomyocytes?

26. What is the function of the T-tubules of the heart muscle?

27. What is not typical for atrial cardiomyocytes?

28. Where is natriuretic factor synthesized?

29. What is the value of atrial natriuretic factor?

30. What is the value of insert discs?

31. What intercellular connections are located in the areas of intercalary discs?

32. What is the function of desmosomal contacts?

33. What is the function of gap junctions?

34. What cells form the second type of myocardial myocytes?

35. What is not included in the conduction system of the heart?

36. What cells are not included in conducting cardiac myocytes?

37. What is the function of pacemaker cells?

38. Where are pacemaker cells located?

39. What is not typical for the structure of pacemaker cells?

40. What is the function of transitional cells?

41. What is the function of Purkinje fibers?

42. What is not typical for the structure of transitional cells of the conducting system of the heart?

43. What is not typical for the structure of Purkinje fibers?

44. What is the structure of the epicardium?

45. What is the epicardium covered with?

46. ​​What layer is absent in the epicardium?

47. How is the regeneration of the heart muscle in childhood?

48. How is the regeneration of the heart muscle in adults?

49. What tissue does the pericardium consist of?

50. Epicardium is ...

Instructions for the study of micropreparations

A. Bovine heart wall

Stained with hematoxylin-eosin.

With a small increase, it is necessary to orient in the shells of the heart. The endocardium is secreted as a pink strip covered with endothelium with large purple nuclei. Below it is the subendothelial layer - loose connective tissue, deeper - muscular-elastic and outer connective tissue layers.

The main mass of the heart is the myocardium. In the myocardium, we observe strips of cardiomyocytes, the nuclei in which are located in the center. Anastomoses are distinguished between the strips (chains) of cardiomyocytes. Inside the strips (these are functional muscle "fibers"), cardiomyocytes are connected using intercalated discs. Cardiomyocytes have a transverse striation due to the presence of isotropic (light) and anisotropic (dark) disks in the composition of the myofibrils themselves. Between the chains of cardiomyocytes there are light gaps filled with loose fibrous connective tissue.

Clusters of conductive (atypical) cardiomyocytes are located directly under the endocardium. In cross section, they look like large oxyphilic cells. There are fewer myofibrils in their sarcoplasm than in contractile cardiomyocytes.

Tasks for the licensed exam "Krok-1"

1. On a micropreparation - the wall of the heart. In one of the membranes there are contractile and secretory myocytes, endomysium with blood vessels. What shell of the heart do these structures correspond to?

A. Atrial myocardium.

B. Pericardium.

C. Adventitia.

D. Endocardium of the ventricles.

2. The labels of myocardial and skeletal muscle histological preparations were mixed up in the laboratory. What structural feature made it possible to determine the myocardial preparation?

A. Peripheral position of nuclei.

B. The presence of an insert disk.

C. Absence of myofibrils.

D. The presence of transverse striation.

3. As a result of myocardial infarction, a section of the heart muscle was damaged, which was accompanied by a mass death of cardiomyocytes. What cellular elements will ensure the replacement of the formed defect in the structure of the myocardium?

A. Fibroblasts.

B. Cardiomyocytes.

C. Myosatellocytes.

D. Epitheliocytes.

E. Unstriated myocytes.

4. On the histological preparation of the "walls of the heart", the main part of the myocardium is formed by cardiomyocytes, which form muscle fibers with the help of intercalated discs. What type of connection provides electrical connection between neighboring cells?

A. Gap contact (Nexus).

B. Desmosome.

C. Hemidesmosome.

D. Tight contact.

E. Simple contact.

5. A histological specimen shows an organ of the cardiovascular system. One of its membranes is formed by fibers that anastomose with each other, consist of cells, and form intercalated discs at the point of contact. The shell of what organ is represented on the preparation?

A. Hearts.

B. Arteries of the muscular type.

D. Veins of muscular type.

E. Arteries of mixed type.

6. Several membranes are distinguished in the wall of blood vessels and the wall of the heart. Which of the membranes of the heart in terms of histogenesis and tissue composition is similar to the wall of blood vessels?

A. Endocardium.

B. Myocardium.

C. Pericardium.

D. Epicardium.

E Epicardium and myocardium.

7. On the histological preparation of the "walls of the heart" under the endocardium, one can see elongated cells with a nucleus on the periphery with a small number of organelles and myofibrils, which are located chaotically. What are these cells?

A. Striated myocytes.

B. Contractile cardiomyocytes.

C. Secretory cardiomyocytes.

D. Smooth myocytes.

E. Conducting cardiomyocytes.

8. As a result of myocardial infarction, a blockade of the heart has come: the atria and ventricles are contracting out of sync. Damage to what structures is the cause of this phenomenon?

A. Conducting cardiomyocytes of the Hiss bundle.

B. Pacemaker cells of the sinoatrial node.

C. Contractile myocytes of the ventricles.

D. Nerve fibers n.vagus.

E. Sympathetic nerve fibers.

9. A patient with endocarditis has a pathology of the valvular apparatus of the inner lining of the heart. What tissues form the valves of the heart?

A. Dense connective tissue, endothelium.

B. Loose connective tissue, endothelium.

C. Cardiac muscle tissue, endothelium.

D. Hyaline cartilage, endothelium.

E. Elastic cartilage tissue, endothelium.

10. In a patient with pericarditis, serous fluid accumulates in the pericardial cavity. What pericardial cells are affected by this process?

A. Mesothelial cells.

B. Endothelial cells.

C. Smooth myocytes.

D. Fibroblasts.

E. Macrofagov

Appendix V

(mandatory)

conduction system of the heart. Systema conducens cardiacum

In the heart, an atypical ("conducting") muscular system is isolated. The microanatomy of the conduction system of the heart is shown in Scheme 1. This system is represented by: the sinoatrial node (sinoatrial); atrioventricular node (AV); atrioventricular bundle of Hiss.

There are three types of muscle cells, which are in different proportions in different parts of this system.

The sinoatrial node is located almost in the wall of the superior vena cava in the region of the venous sinus, in this node an impulse is formed that determines the automatism of the heart, its central part is occupied by cells of the first type - pacemakers, or pacemaker cells (P-cells). These cells differ from typical cardiomyocytes in their small size, polygonal shape, a small number of myofibrils, the sarcoplasmic reticulum is poorly developed, the T-system is absent, and there are many pinocytic vesicles and caveolae. Their cytoplasm has the ability to spontaneous rhythmic polarization and depolarization. The atrioventricular node is predominantly made up of transitional cells (cells of the second type).

They perform the function of conducting excitation and its transformation (inhibition of the rhythm) from P-cells to bundle cells and contractile ones, but in the pathology of the sinoatrial node, its function passes to atrioventricular. Their cross section is smaller than the cross section of typical cardiomyocytes. Myofibrils are more developed, oriented parallel to each other, but not always. Individual cells may contain T-tubules. Transitional cells are in contact with each other using both simple contacts and intercalary discs.

The atrioventricular bundle of Giss consists of a trunk, right and left legs (Purkinje fibers), the left leg splits into anterior and posterior branches. The Hiss bundle and Purkinje fibers are represented by cells of the third type, which transmit excitation from transitional cells to contractile cardiomyocytes of the ventricles. According to the structure of the cells of the bundle, they are distinguished by large sizes in diameter, the almost complete absence of T-systems, myofibrils are thin, which are randomly located mainly along the periphery of the cell. The nuclei are located eccentrically.

Purkinje cells are the largest not only in the leading system, but throughout the entire myocardium. They have a lot of glycogen, a rare network of myofibrils, no T-tubules. Cells are interconnected by nexuses and desmosomes.

Educational edition

Vasko Ludmila Vitalievna, Kiptenko Lyudmila Ivanovna,

Budko Anna Yurievna, Zhukov Svetlana Vyacheslavovna

Special histology of sensory and

regulatory systems

In two parts

Responsible for the issue Vasko L.V.

Editor T.G. Chernyshova

Computer layout A.A. Kachanova

Signed for publication on 07/07/2010.

Format 60x84/16. Conv. oven l. . Uch. - ed. l. . Circulation copies.

Deputy No. Edition cost

Publisher and manufacturer Sumy State University

st. Rimsky-Korsakov, 2, Sumy, 40007.

Certificate of publishing entity DK 3062 dated 12/17/2007.

others), as well as regulatory substances - caylons, ...

27. Cardiovascular system

Arteriovenular anastomoses are connections of vessels carrying arterial and venous blood, bypassing the capillary bed. Their presence is noted in almost all organs.

There are two groups of anastomoses:

1) true arteriovenular anastomoses (shunts), through which pure arterial blood is discharged;

2) atypical arteriovenular fistulas (semi-shunts), through which mixed blood flows.

The external form of the first group of anastomoses can be different: in the form of straight short anastomoses, loop-like, sometimes in the form of branching connections.

Histostructurally, they are divided into two subgroups:

a) vessels that do not have special locking devices;

b) vessels equipped with special contractile structures.

In the second subgroup, anastomoses have special contractile sphincters in the form of longitudinal ridges or pillows in the subendothelial layer. The contraction of the muscle pads protruding into the lumen of the anastomosis leads to the cessation of blood flow. Simple anastomoses of the epithelioid type are characterized by the presence in the middle shell of the inner longitudinal and outer circular layers of smooth muscle cells, which, as they approach the venous end, are replaced by short oval light cells, similar to epithelial cells, capable of swelling and swelling, due to which the lumen of the anastomosis changes. In the venous segment of the arterio-venular anastomosis, its wall sharply becomes thinner. The outer shell consists of dense connective tissue. Arteriovenular anastomoses, especially of the glomerular type, are richly innervated.

The structure of veins is closely related to the hemodynamic conditions of their functioning. The number of smooth muscle cells in the wall of the veins is not the same and depends on whether the blood moves in them to the heart under the influence of gravity or against it. According to the degree of development of muscle elements in the wall of the veins, they can be divided into two groups: veins of the non-muscular type and veins of the muscular type. Muscular veins, in turn, are divided into veins with weak development of muscle elements and veins with medium and strong development of muscle elements. In the veins (as well as in the arteries), three membranes are distinguished: internal, middle and external, while the degree of expression of these membranes in the veins differs significantly. Veins of the non-muscular type are veins of the dura mater, pia mater, veins of the retina, bones, spleen, and placenta. Under the action of blood, these veins are capable of stretching, but the blood accumulated in them flows relatively easily under the influence of its own gravity into larger venous trunks. Veins of the muscular type are distinguished by the development of muscle elements in them. These veins include the veins of the lower body. Also, in some types of veins there are a large number of valves, which prevents the reverse flow of blood under its own gravity.

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1. According to the diameter of the lumen

Narrow (4-7 microns) are found in the striated muscles, lungs, and nerves.

Wide (8-12 microns) are in the skin, mucous membranes.

Sinusoidal (up to 30 microns) are found in the hematopoietic organs, endocrine glands, and liver.

Lacunas (more than 30 microns) are located in the columnar zone of the rectum, the cavernous bodies of the penis.

2. According to the structure of the wall

Somatic, characterized by the absence of fenestra (local thinning of the endothelium) and holes in the basement membrane (perforations). Located in the brain, skin, muscles.

Fenestrated (visceral type), characterized by the presence of fenestra and the absence of perforations. They are located where the processes of molecular transfer occur most intensively: glomeruli of the kidneys, intestinal villi, endocrine glands).

Perforated, characterized by the presence of fenestra in the endothelium and perforations in the basement membrane. This structure facilitates the transition through the cell capillary wall: sinusoidal capillaries of the liver and hematopoietic organs.

Capillary function- the exchange of substances and gases between the lumen of the capillaries and the surrounding tissues is carried out due to the following factors:

1. Thin wall of capillaries.

2. Slow blood flow.

3. Large area of ​​contact with surrounding tissues.

4. Low intracapillary pressure.

The number of capillaries per unit volume in different tissues is different, but in each tissue there are 50% of non-functioning capillaries that are in a collapsed state and only blood plasma passes through them. When the load on the body increases, they begin to function.

There is a capillary network that is enclosed between two vessels of the same name (between two arterioles in the kidneys or between two venules in the portal system of the pituitary gland), such capillaries are called the “miraculous network”.

When several capillaries merge, they form postcapillary venules or postcapillaries, with a diameter of 12-13 microns, in the wall of which there is a fenestrated endothelium, there are more pericytes. When postcapillaries merge, they form collecting venules, in the middle shell of which smooth myocytes appear, the adventitial shell is better expressed. Collecting venules continue into muscle venules, in the middle shell of which contains 1-2 layers of smooth myocytes.

Venule function:

· Drainage (receipt of metabolic products from the connective tissue into the lumen of the venules).

Blood cells migrate from the venules into the surrounding tissue.

The microcirculation includes arteriolo-venular anastomoses (AVA)- These are the vessels through which blood from the arterioles enters the venules bypassing the capillaries. Their length is up to 4 mm, diameter is more than 30 microns. AVAs open and close 4 to 12 times per minute.

AVAs are classified into true (shunts) through which arterial blood flows, and atypical (semi-shunts) through which mixed blood is discharged, tk. when moving along the half-shunt, a partial exchange of substances and gases with the surrounding tissues occurs.

Functions of true anastomoses:

Regulation of blood flow in capillaries.

Arterialization of venous blood.

Increased intravenous pressure.

Functions of atypical anastomoses:

· Drainage.

· Partial exchange.

Heart

It is the central organ of blood and lymph circulation. Due to the ability to contract, it sets the blood in motion. The wall of the heart consists of three layers: endocardium, myocardium and epicardium.

Development of the heart

It occurs as follows: in the cranial pole of the embryo, on the right and on the left, endocardial tubes are formed from the mesenchyme. At the same time, thickenings appear in the visceral sheets of the splanchnotome, which are called myoepicardial plates. The endocardial tubes are inserted into them. The two formed heart rudiments gradually approach and merge into a single tube consisting of three shells, so a single-chamber model of the heart appears. Then the tube grows in length, it acquires an S-shape and is divided into an anterior section - ventricular and posterior - atrial. Later, septa and valves appear in the heart.

The structure of the endocardium

The endocardium is the inner shell of the heart, which lines the atria and ventricles, consists of four layers and in its structure resembles the wall of an artery.

Layer I is the endothelium, which is located on the basement membrane.

Layer II - subendothelial, represented by loose connective tissue. These two layers are analogous to the inner lining of the arteries.

Layer III - muscular-elastic, consisting of smooth muscle tissue, between the cells of which elastic fibers are located in the form of a dense network. This layer is the "equivalent" of the middle lining of the arteries.

Layer IV - outer connective tissue, consisting of loose connective tissue. It is similar to the outer (adventitial) membrane of the arteries.

There are no vessels in the endocardium, so its nutrition occurs by diffusion of substances from the blood in the cavities of the heart.

Due to the endocardium, atrioventricular valves and valves of the aorta and pulmonary artery are formed.

The cardiovascular system is involved in metabolism, provides and determines the movement of blood, serves as a transport medium between body tissues.

As part of the cardiovascular system, there are: the heart is the central organ that sets the blood in constant motion; blood and lymph vessels; blood and lymph. Hematopoietic organs are associated with this system, which simultaneously perform protective functions.

The organs of the cardiovascular system, hematopoiesis and immunity develop from the mesenchyme, and the membranes of the heart - from the visceral sheet of the mesoderm.

HEART

The central organ of the cardiovascular system is the heart; thanks to its rhythmic contractions, blood circulates through the large (systemic) and small (pulmonary) circulations, that is, throughout the body.

In mammals, the heart is located in the chest cavity between the lungs, in front of the diaphragm in the region from the 3rd to the 6th rib in the plane of the center of gravity of the second quarter of the body. Most of the heart is to the left of the midline, while the right atrium and vena cava are located to the right.

The mass of the heart depends on the type, breed and sex of the animal, as well as on age and physical activity. For example, in a bull, the mass of the heart is 0.42%, and in a cow - 0.5% of body weight.

The heart is a hollow organ divided internally into four cavities, or chambers: two atrium and two ventricle oval-cone-shaped or oval-rounded. In the upper part of each atrium there are protruding parts - ears. The atria are externally separated from the ventricles by the coronal groove, in which the main branches of the blood vessels pass. The ventricles are separated from one another by interventricular grooves. The atria, ascending aorta, and pulmonary trunk face upward and form the base of the heart; the lowest and most of all protruding to the left pointed section of the left ventricle - the apex of the heart.

In the lateral plates of the cervical region, at the end of the second week of development of the embryo, a paired accumulation of mesenchymal cells is formed (Fig. 78). From these cells, two mesenchymal strands are formed, gradually transforming into two elongated tubes, lined from the inside with endothelium. This is how the endocardium is formed, surrounded by a visceral sheet of mesoderm. Somewhat later, in connection with the formation of the trunk fold, two tubular rudiments of the future heart approach and merge into one common unpaired tubular organ.

From the visceral sheet of the mesoderm in the area adjacent to the endocardium, myoepicardial plates are isolated, which subsequently develop into the rudiments of the myocardium and epicardium.

So, at this stage of development, the unpaired heart is initially a tubular organ, in which there are narrowed cranial and caudal expanded sections. Blood enters through the caudal, and exits through the cranial part of the organ, and already at this early stage of development, the first corresponds to the future atria, and the second to the ventricles.

Further formation of the heart is associated with uneven growth of individual sections of the tubular organ, as a result

Rice. 78.

a B C - respectively early, middle, late stages; /-ectoderm; 2-endoderm; 3- mesoderm; -/ - chord; 5-nerve plate; b - paired bookmark of the heart; 7-neural tube; 8- unpaired bookmark of the heart; 9 - esophagus; 10- steam aorta; 11 - endocardium;

12- myocardium

which forms an S-shaped bend. Moreover, the caudal venous section with thinner membranes slightly shifts the dorsal side forward - an atrium is formed. The cranial arterial section, which has more pronounced membranes, remains on the ventral side - a ventricle is formed. So there is a two-chambered heart. A little later, the partitions in the atrium and in the ventricle separate and the two-chamber heart becomes four-chamber. Holes remain in the longitudinal septum: oval - between the atria and small - between the ventricles. The foramen ovale usually heals after birth, while the foramen ovale closes before birth.

The arterial trunk, which is a section of the original heart tube, is divided by a septum formed in the original ventricle, resulting in the aorta and pulmonary artery.

There are three membranes in the heart: the inner one is the endocardium, the middle one is the myocardium and the outer one is the epicardium. The heart is located in the pericardial sac - the pericardium (Fig. 79).

Endocardium (e n doc a rdium) - a membrane lining the inside of the cavity of the heart, muscular papillae, tendon filaments and valves. The endocardium has a different thickness, for example, it is much thicker in the atrium and in the ventricle of the left half. At the mouth of large trunks - the aorta and pulmonary artery, the endocardium is more pronounced, while on the tendon filaments this sheath is very thin.

Microscopic examination reveals layers in the endocardium that have a similar structure to blood vessels. So, from the side of the surface facing the cavity of the heart, the endocardium is lined with endothelium, consisting of endotheliocytes located on the basement membrane. Nearby is the subendothelial layer, formed by loose fibrous connective tissue and containing a lot of poorly differentiated cambial cells. There are also muscle cells - myocytes and intertwining elastic fibers. The outer layer of the endocardium, as in the blood vessels, consists of loose fibrous connective tissue containing small blood vessels.

Derivatives of the endocardium are atrioventricular (atrioventricular) valves: bicuspid in the left half, tricuspid in the right.

The basis, or frame, of the valve leaflet is formed by a thin, but very strong structure - its own, or main, plate, formed by loose fibrous connective tissue. The strength of this layer is due to the predominance of fibrous material over cellular elements. In the areas of attachment of the bicuspid and tricuspid valves, the connective tissue of the valves passes into the fibrous rings. Both sides of the lamina propria are covered with endothelium.

The atrial and ventricular sides of the valve leaflets have a different structure. So, the atrial side of the valves is smooth from the surface, has a dense plexus of elastic fibers and bundles of smooth muscle cells in its own plate. The ventricular side is uneven, with outgrowths (papillae) to which collagen fibers, the so-called tendon fibers, are attached.

Rice. 79.

a- stained with hematoxylin and eosin; b- stained with iron hematoxylin;

BUT - endocardium; B- myocardium; AT- epicardium: / - atypical fibers; 2- cardiomyocytes

threads (chordae tendinae); a small amount of elastic fibers is located only directly under the endothelium.

Myocardium (miocardium) - the middle muscular membrane, represented by typical cells - cardiomyocytes and atypical fibers that form the conduction system of the heart.

cardiac myocytes(myociti cardiaci) perform a contractile function and form a powerful apparatus of striated muscle tissue, the so-called working muscles.

Striated muscle tissue is formed from closely anastomosing (interconnected) cells - cardiomyocytes, which together form a single system of the heart muscle.

Cardiomyocytes have an almost rectangular shape, the length of the cell ranges from 50 to 120 microns, the width is 15...20 microns. In the central part of the cytoplasm there is a large oval nucleus, sometimes binuclear cells are found.

In the peripheral part of the cytoplasm, there are about a hundred contractile protein filaments - myofibrils, with a diameter of 1 to 3 microns. Each myofibril is formed by several hundred protofibrils, which determine the striated striation of myocytes.

Between the myofibrils there are many oval-shaped mitochondria arranged in chains. The mitochondria of the heart muscle are characterized by the presence of a large number of cristae located so close that the matrix is ​​practically invisible. With the presence of a huge number of mitochondria containing enzymes and participating in redox processes, the ability of the heart to work continuously is associated.

Cardiac striated muscle tissue is characterized by the presence of intercalated discs (diski intercalati) - these are areas of contact between adjacent cardiomyocytes. Within the intercalated discs, highly active enzymes are found: ATPase, dehydrogenase, alkaline phosphatase, which indicates an intensive metabolism. There are straight and stepped insert discs. If the cells are limited by straight intercalary discs, then the total length of the protofibrils will be the same; if stepped intercalary discs, then the total length of protofibril bundles will be different. This is explained by the fact that individual bundles of protofibrils are interrupted in the region of the intercalated disks. Intercalated discs are actively involved in the transmission of excitations from cell to cell. With the help of discs, myocytes are connected into muscle complexes, or fibers (miofibra cardiaca).

Between the muscle fibers there are anastomoses that provide contractions of the myocardium as a whole in the atria and ventricles.

In the myocardium, numerous layers of loose fibrous connective tissue are distinguished, in which there are many elastic and very few collagen fibers. Nerve fibers, lymphatic and blood vessels pass here, each myocyte is in contact with two or more capillaries. Muscle tissue is attached to the supporting skeleton located between the atria and ventricles and at the mouths of large vessels. The supporting skeleton of the heart is formed by dense bundles of collagen fibers or fibrous rings.

conduction system of the heart it is represented by atypical muscle fibers (myofibra conducens), which form nodes: the sinoatrial Keith-Fleck, located at the mouth of the cranial vena cava; atrioventricular Ashof-Tavara - near the attachment of the leaflet of the tricuspid valve; the trunk and branches of the atrioventricular system - the bundle of His (Fig. 80).

Atypical muscle fibers contribute to successive contractions of the atria and ventricles throughout the cardiac cycle - automatism of the heart. Therefore, a distinctive feature of the conduction system is the presence of a dense plexus of nerve fibers on atypical muscle fibers.

The muscle fibers of the conduction system have different sizes and directions. For example, in the sinoatrial node, the fibers are thin (from 13 to 17 microns) and densely intertwined in the middle of the node, and as they move away from the periphery, the fibers acquire a more regular arrangement. This node is characterized by the presence of wide layers of connective tissue, in which elastic fibers predominate. The atrioventricular node has a similar structure.

The muscle cells of the conduction system (myociti conducens cardiacus) of the branches of the legs of the trunk of the conduction system (Purkinje fibers) are located in small bundles surrounded by layers of loose fibrous connective tissue. In the region of the ventricles of the heart, atypical fibers have a larger cross section than in other parts of the conduction system.

Rice. 80.

/ - coronary sinus; 2-right atrium; 3 - tricuspid valve; -/- caudal vena cava; 5 - septum between the ventricles; b - branching of the bundle of His; 7- right ventricle; 8- left ventricle; 9- bundle of His; /0 - bicuspid valve; 11- Ashof-Tavar knot; 12- left atrium; 13 - sinoatrial node; //-/-cranial vena cava

Compared with the cells of the working muscles, atypical fibers of the conducting system have a number of distinctive features. Fibers of large size and irregular oval shape. The nuclei are large and light, not always occupy a strictly central position. There is a lot of sarcoplasm in the cytoplasm, but few myofibrils, as a result of which, when stained with hematoxylin and eosin, atypical fibers are light. The cell sarcoplasm contains a lot of glycogen, but few mitochondria and ribosomes. Typically, myofibrils are located at the periphery of cells and are densely intertwined, but do not have such a strict orientation as in typical cardiac myocytes.

Epicardium (epicardium) - the outer shell of the heart. It is a visceral sheet of the serous membrane, which is based on loose fibrous connective tissue. In the atrial region, the layer of connective tissue is very thin and mainly of elastic fibers, which are tightly fused with the myocardium. In the epicardium of the ventricles, in addition to elastic fibers, collagen bundles are found, which make up the denser superficial layer.

The epicardium lines the inner surface of the mediastinum, forming the outer shell of the pericardial cavity, called the parietal layer of the pericardium. Between the epicardium and the pericardium, a cardiac cavity is formed, filled with a small amount of serous fluid.

The pericardium is a three-layer pericardial sac that contains the heart. The pericardium consists of the pericardial pleura, the fibrous layer of the mediastinum, and the parietal layer of the epicardium. The pericardium is attached to the sternum by ligaments, and to the spinal column by vessels entering and leaving the heart. The basis of the pericardium is also loose fibrous connective tissue, but more pronounced than that in the epicardium. From the pericardium of farm animals, substitutes for tanned leather can be obtained.

The surface of the epicardium and the outer surface of the pericardium facing the pericardial cavity are covered with a layer of mesothelium.

The vessels of the heart, mainly the coronary ones, start from the aorta, branch strongly in all membranes into vessels of different diameters, up to the capillaries. From the capillaries, the blood passes into the coronary veins, which flow into the right atrium. In the coronary arteries there are many elastic fibers that create powerful support networks. Lymphatic vessels in the heart form dense networks.

The nerves of the heart are formed from the branches of the border sympathetic trunk, from the fibers of the vagus nerve and spinal fibers. In all three membranes there are nerve plexuses, accompanied by intramural ganglia. In the heart, there are free as well as encapsulated nerve endings. Receptors are found in connective tissue on muscle fibers and in the membranes of blood vessels. Sensory nerve endings perceive changes in the lumen of blood vessels, as well as signals during contraction and stretching of muscle fibers.

Rice. 13.8. Capillary endothelium:

a - planar image; b - sheer cut (scheme according to Yu. I. Afanasiev): 1 - cell boundaries; 2 - cytoplasm; 3 - core; in- fenestra in endotheliocytes of the peritubular capillary of the kidney. Electron micrograph, magnification 20,000 (according to A. A. Mironov); G- paraplasmolemmal layer of the hemocapillary endotheliocyte. Electron micrograph, magnification 80,000 (according to V. V. Kupriyanov, Ya. L. Karaganov and V. I. Kozlov): 1 - capillary lumen; 2 - plasmalemma; 3 - paraplasmolemmal layer; 4 - basement membrane; 5 - pericyte cytoplasm

endotheliocyte skeleton, basement membrane (see below). Pinocytic vesicles and caveolae are located along the inner and outer surfaces of endothelial cells, reflecting the transendothelial transport of various substances and metabolites. There are more of them in the venous part of the capillary than in the arterial part. Organelles, as a rule, are not numerous and are located in the perinuclear zone.

The inner surface of the capillary endothelium, facing the blood flow, may have ultramicroscopic protrusions in the form of individual microvilli, especially in the venous part of the capillary. In these sections of the capillaries, the cytoplasm of endotheliocytes forms valve-like structures. These cytoplasmic outgrowths increase the surface of the endothelium and, depending on the activity of fluid transport through the endothelium, change their size.

The endothelium is involved in the formation of the basement membrane. One of the functions of the endothelium is vasogenesis (neovasculogenesis). Endothelial cells form

they form simple connections between themselves, lock-type contacts and tight contacts with local fusion of the outer plates of the plasmolemma of the contacting endotheliocytes and obliteration of the intercellular gap. Endotheliocytes synthesize and secrete factors that activate the blood coagulation system (thromboplastin, thromboxane), and anticoagulants (prostacycline, etc.). The participation of the endothelium in the regulation of vascular tone is also mediated through receptors. When vasoactive substances bind to receptors in endothelial cells, either a relaxation factor or a contraction factor of smooth myocytes is synthesized. These factors are specific and act only on smooth vascular myocytes. The basement membrane of the capillary endothelium is a thin-fibrillar, porous, semi-permeable plate 30-35 nm thick, which includes type IV and V collagen, glycoproteins, as well as fibronectin, laminin and sulfate-containing proteoglycans. The basement membrane performs supporting, delimiting and barrier functions. Between endothelial cells and pericytes, the basement membrane becomes thinner and interrupted in places, and the cells themselves are interconnected here by means of tight plasmolemma junctions. This area of ​​endotheliopericytic contacts serves as a site for the transfer of various factors from one cell to another.