The muscular layer of the wall of the heart. The middle layer of the wall of the heart is called. The structure and function of the small intestine

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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 It is formed by 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. The inner layer of the 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.

As part of the endocardium, there are: endothelium, subendothelial layer, muscular-elastic and external connective tissue. The endothelium is represented by only one layer of flat cells. The endocardium without a sharp border passes to large cardiac vessels. The cusps of the cuspid valves and the cusps of the semilunar valves represent a duplication of the endocardium.

Myocardium, myocardium, is the most significant shell in thickness and the most important in function. The myocardium is a multitissue structure consisting of striated muscle tissue, loose and fibrous connective tissue, atypical cardiomyocytes, blood vessels, and nerve elements. The collection of contractile muscle cells makes up the heart muscle. The cardiac muscle has a special structure, occupying an intermediate position between striated and smooth muscles. The fibers of the heart muscle are capable of rapid contractions, are interconnected by jumpers, as a result of which a wide-loop network is formed, called syncytium. Muscle fibers are almost devoid of a sheath, their nuclei are in the middle. The contraction of the muscles of the heart is automatic. The muscles of the atria and ventricles are anatomically separate. They are connected only by a system of conductive fibers. The atrial myocardium has two layers: a superficial one, the fibers of which run transversely, covering both atria, and a deep separate one for each atrium. The latter consists of vertical bundles starting from the fibrous rings in the region of the atrioventricular openings and from circular bundles located at the mouths of the hollow and pulmonary veins.

The ventricular myocardium is much more complex than the atrial myocardium. There are three layers: outer (superficial), middle and inner (deep). The bundles of the surface layer, common to both ventricles, start from the fibrous rings, go obliquely - from top to bottom to the top of the heart. Here they turn back, go into the depths, forming in this place a curl of the heart, vortex cordis. Without interruption, they pass into the inner (deep) layer of the myocardium. This layer has a longitudinal direction, forms fleshy trabeculae and papillary muscles.

Between the superficial and deep layers lies the middle - circular layer. It is separate for each of the ventricles, and is better developed on the left. Its bundles also start from the fibrous rings and run almost horizontally. Between all muscle layers there are numerous connecting fibers.

In the wall of the heart, in addition to muscle fibers, there are connective tissue formations - this is the heart's own "soft skeleton". It plays the role of supporting structures from which muscle fibers begin and where the valves are fixed. The soft skeleton of the heart includes four fibrous rings, nnuli fibrosi, two fibrous triangles, trigonum fibrosum, and the membranous part of the interventricular septum, pars membranacea septum interventriculare.

Myocardial muscle tissue

Fibrous rings, annlus fibrosus dexter et sinister, surround the right and left atrioventricular openings. Provide support for tricuspid and bicuspid valves. The projection of these rings on the surface of the heart corresponds to the coronary sulcus. Similar fibrous rings are located in the circumference of the mouth of the aorta and the pulmonary trunk.

The right fibrous triangle is larger than the left one. It occupies a central position and actually connects the right and left fibrous rings and the connective tissue ring of the aorta. From below, the right fibrous triangle is connected to the membranous part of the interventricular septum. The left fibrous triangle is much smaller, it connects to the anulus fibrosus sinister.

The base of the ventricles, the atria are removed. Mitral valve lower left

Atypical cells of the conducting system, which form and conduct impulses, ensure the automaticity of the contraction of typical cardiomyocytes. They make up the conduction system of the heart.

Thus, in the composition of the muscular membrane of the heart, three functionally interconnected apparatuses can be distinguished:

1) Contractile, represented by typical cardiomyocytes;

2) Support formed by connective tissue structures around natural openings and penetrating into the myocardium and epicardium;

3) Conducting, consisting of atypical cardiomyocytes - cells of the conducting system.

Epicardium, epicardium, covers the heart from the outside; under it are the own vessels of the heart and fatty tissue. It is a serous membrane and consists of a thin plate of connective tissue covered with mesothelium. The epicardium is also called the visceral plate of the serous pericardium, lamina visceralis pericardii serosi.

The structure of the walls of the heart

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).

The 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.

The myocardium is formed by 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.

The atrial myocardium is separated by fibrous rings from the ventricular myocardium. 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.

The 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. The inner layer of the 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.

The epicardium 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.

Shells of the heart anatomy

Heart. Endocardium. Myocardium. The structure of the heart.

The heart is the central organ of the blood and lymph circulation system. Due to the ability to contract, the heart sets the blood in motion.

The wall of the heart consists of three layers: endocardium, myocardium and epicardium.

Endocardium. In the inner shell of the heart, the following layers are distinguished: endothelium, lining the inside of the cavity of the heart, and its basement membrane; subendothelial layer, represented by loose connective tissue, in which there are many poorly differentiated cells; muscular-elastic layer, consisting of smooth muscle tissue, between the cells of which elastic fibers are located in the form of a dense network; outer connective tissue layer, consisting of loose connective tissue. The endothelium and subendothelial layers are similar to the inner membrane of the vessels, the musculo-elastic layer is the "equivalent" of the middle membrane, and the outer connective tissue layer is similar to the outer (adventitial) membrane of the vessels.

The surface of the endocardium is ideally smooth and does not interfere with the free movement of blood. In the atrioventricular region and at the base of the aorta, the endocardium forms duplications (folds), called valves. Distinguish between atrioventricular and ventricular-vascular valves. There are fibrous rings at the attachment sites of the valves. Heart valves are dense plates of fibrous connective tissue covered with endothelium. The nutrition of the endocardium occurs by diffusion of substances from the blood located in the cavities of the atria and ventricles.

Myocardium (middle shell of the heart) is a multi-tissue shell, consisting of striated cardiac muscle tissue, intermuscular loose connective tissue, numerous vessels and capillaries, as well as nerve elements. The main structure is cardiac muscle tissue, which in turn consists of cells that form and conduct nerve impulses, and cells of the working myocardium that provide contraction of the heart (cardiomyocytes). Among the cells that form and conduct impulses in the conduction system of the heart, there are three types: P-cells (pacemaker cells), intermediate cells and Purkinya cells (fibers).

P-cells - pacemaker cells, located in the center of the sinus node of the conduction system of the heart. They have a polygonal shape and are determined to spontaneous depolarization of the plasmalemma. Myofibrils and organelles of general importance in pacemaker cells are weakly expressed. Intermediate cells are a heterogeneous group of cells that transmit excitation from P-cells to Purkinya cells. Purkinya cells are cells with a small number of myofibrils and a complete absence of the T-system, with a large amount of cytoplasm compared to working contractile myocytes. Purkinya cells transmit excitation from intermediate cells to contractile cells of the myocardium. They are part of the bundle of His of the conduction system of the heart.

A number of drugs and other factors that can lead to arrhythmias and heart block have an adverse effect on pacemaker cells and Purkinya cells. The presence in the heart of its own conducting system is extremely important, since it provides a rhythmic change in systolic contractions and diastole of the heart chambers (atria and ventricles) and the operation of its valvular apparatus.

The bulk of the myocardium is made up of contractile cells - cardiac myocytes, or cardiomyocytes. These are cells of an elongated shape with an ordered system of transversely striated myofibrils located on the periphery. Between the myofibrils are mitochondria with a large number of cristae. In atrial myocytes, the T-system is weakly expressed. The granular endoplasmic reticulum is poorly developed in cardiomyocytes. In the central part of myocytes there is an oval-shaped nucleus. Sometimes there are binuclear cardiomyocytes. Atrial muscle tissue contains cardiomyocytes with osmiophilic secretory granules containing natriuretic peptide.

In cardiomyocytes, inclusions of glycogen, which serves as the energy material of the heart muscle, are determined. Its content in the myocytes of the left ventricle is greater than in other parts of the heart. The myocytes of the working myocardium and the conducting system are interconnected by means of intercalated discs - specialized intercellular contacts. Actin contractile myofilaments are attached in the region of the intercalated discs, desmosomes and gap junctions (nexuses) are present.

Desmosomes contribute to the strong adhesion of contractile myocytes into functional muscle fibers, and nexuses ensure the rapid propagation of plasma membrane depolarization waves from one muscle cell to another and the existence of a cardiac muscle fiber as a single metabolic unit. Characteristic for myocytes of the working myocardium is the presence of anastomosing bridges - interconnected fragments of the cytoplasms of muscle cells of different fibers with myofibrils located in them. Thousands of such bridges turn the muscle tissue of the heart into a mesh structure capable of synchronously and efficiently contracting and ejecting the necessary systolic blood volumes from the ventricular cavities. After suffering extensive myocardial infarctions (acute ischemic necrosis of the heart wall), when the muscular tissue of the heart, the system of intercalated discs, anastomosing bridges and the conduction system are diffusely affected, disturbances in the rhythm of the heart, up to fibrillation, occur. In this case, the contractile activity of the heart turns into separate uncoordinated twitches of muscle fibers and the heart is not able to eject the necessary systolic portions of blood into the peripheral circulation.

The myocardium consists in general of highly specialized cells that have lost the ability to divide by mitosis. Mitoses of cardiomyocytes are observed only in certain parts of the atria (Rumyantsev P.P. 1982). At the same time, the myocardium is characterized by the presence of polyploid myocytes, which significantly enhances its working potential. The phenomenon of polyploidy is most often observed in compensatory reactions of the myocardium, when the load on the heart increases, and in pathology (failure of heart valves, lung diseases, etc.).

In these cases, cardiac myocytes sharply hypertrophy, and the wall of the heart thickens in one or another section. The myocardial connective tissue contains a richly branched network of blood and lymphatic capillaries, which provides the constantly working heart muscle with nutrition and oxygen. In the layers of connective tissue there are dense bundles of collagen fibers, as well as elastic fibers. In general, these connective tissue structures constitute the supporting skeleton of the heart, to which cardiac muscle cells are attached.

The heart is an organ that has the ability to automatically contract. It can function autonomously within certain limits. However, in the body, the activity of the heart is under the control of the nervous system. In the intramural nerve nodes of the heart there are sensitive autonomic neurons (Type II Dogel cells), small intensely fluorescent cells - MYTH cells and effector autonomic neurons (Type I Dogel cells). MYTH cells are considered as intercalary neurons.

The epicardium - the outer shell of the heart - is a visceral sheet of the pericardial sac (pericardium). The free surface of the epicardium is lined with mesothelium in the same way as the surface of the pericardium facing the pericardial cavity. Under the mesothelium in the composition of these serous membranes is a connective tissue base of loose fibrous connective tissue.

Endocardium, endocardium (see Fig. 704. 709), is formed from elastic fibers, among which are connective tissue and smooth muscle cells. From the side of the cavity of the heart, the endocardium is covered with endothelium.

The endocardium lines all the chambers of the heart, is tightly fused with the underlying muscle layer, follows all its irregularities formed by the fleshy trabeculae, pectinate and papillary muscles, as well as their tendon outgrowths.

On the inner shell of the vessels leaving the heart and flowing into it - the hollow and pulmonary veins, the aorta and the pulmonary trunk - the endocardium passes without sharp boundaries. In the atria, the endocardium is thicker than in the ventricles, especially in the left atrium, and thinner where it covers the papillary muscles with tendon chords and fleshy trabeculae.

In the most thinned sections of the walls of the atria, where gaps form in their muscular layer, the endocardium is in close contact and even fuses with the epicardium. In the region of the fibrous rings of the atrioventricular openings, as well as the openings of the aorta and pulmonary trunk, the endocardium, by doubling its leaf - endocardial duplication - forms the leaflets of the atrioventricular valves and the semilunar valves of the pulmonary trunk and aorta. The fibrous connective tissue between both sheets of each of the cusps and semilunar valves is connected to the fibrous rings and thus fixes the valves to them.

shells of the heart

The heart is located in the pericardial sac - the pericardium. 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.

The outer shell of the heart. epicardium

The epicardium is a smooth, thin and transparent membrane. It is the visceral plate of the pericardial sac (pericardium). The connective tissue base of the epicardium in various parts of the heart, especially in the sulci and in the apex, includes adipose tissue. With the help of the specified connective tissue, the epicardium is most tightly fused with the myocardium in places of the least accumulation or absence of adipose tissue.

The muscular layer of the heart, or myocardium

The middle, muscular membrane of the heart (myocardium), or cardiac muscle, is a powerful and significant part of the wall of the heart in thickness.

Between the muscular layer of the atria and the muscular layer of the ventricles lies dense fibrous tissue, due to which fibrous rings, right and left, are formed. From the side of the outer surface of the heart, their location corresponds to the region of the coronal sulcus.

The right fibrous ring, which surrounds the right atrioventricular orifice, is oval in shape. The left fibrous ring does not completely surround the left atrioventricular opening: on the right, on the left and behind, and has a horseshoe shape.

With its anterior sections, the left fibrous ring is attached to the aortic root, forming triangular connective tissue plates around its posterior periphery - the right and left fibrous triangles.

The right and left fibrous rings are interconnected into a common plate, which completely, with the exception of a small area, isolates the muscles of the atria from the muscles of the ventricles. In the middle of the fibrous plate connecting the rings there is a hole through which the muscles of the atria are connected to the muscles of the ventricles through the neuromuscular atrioventricular bundle conducting impulses.

In the circumference of the openings of the aorta and the pulmonary trunk, there are also interconnected fibrous rings; the aortic ring is connected to the fibrous rings of the atrioventricular orifices.

Muscular layer of the atria

In the walls of the atria, two muscle layers are distinguished: superficial and deep.

The surface layer is common to both atria and represents muscle bundles that run mainly in the transverse direction; they are more pronounced on the anterior surface of the atria, forming here a relatively wide muscle layer in the form of a horizontally located inter-auricular bundle passing to the inner surface of both ears.

On the posterior surface of the atria, the muscle bundles of the superficial layer are partially woven into the posterior sections of the septum.

On the posterior surface of the heart, in the gap formed by the convergence of the borders of the inferior vena cava, the left atrium and the venous sinus, between the bundles of the surface layer of muscles there is a depression covered by the epicardium - the neural fossa. Through this fossa, nerve trunks enter the atrial septum from the posterior cardiac plexus, which innervate the atrial septum, the ventricular septum and the muscle bundle that connects the muscles of the atria with the muscles of the ventricles - the atrioventricular bundle.

The deep layer of muscles of the right and left atria is not common to both atria. It distinguishes ring-shaped, or circular, and loop-shaped, or vertical, muscle bundles.

Circular muscle bundles lie in large numbers in the right atrium; they are located mainly around the openings of the vena cava, passing to their walls, around the coronary sinus of the heart, at the mouth of the right ear and at the edge of the oval fossa; in the left atrium, they lie mainly around the openings of the four pulmonary veins and at the neck of the left ear.

Vertical muscle bundles are located perpendicular to the fibrous rings of the atrioventricular holes, attaching to them with their ends. Part of the vertical muscle bundles enters the thickness of the cusps of the mitral and tricuspid valves.

The crest muscles are also formed by bundles of the deep layer. They are most developed on the inner surface of the anterior right wall of the right atrium, as well as the right and left ears; in the left atrium they are less pronounced. In the intervals between the comb muscles, the wall of the atria and ears is especially thinned.

On the inner surface of both ears there are very short and thin bundles, the so-called fleshy crossbars. Crossing in different directions, they form a very thin loop-like network.

Muscular layer of the ventricles

In the muscular membrane (myocardium) there are three muscle layers: outer, middle and deep. The outer and deep layers, passing from one ventricle to another, are common in both ventricles; the middle one, although connected with the other two, outer and deep, layers, but surrounds each ventricle separately.

The outer, relatively thin, layer consists of oblique, partly rounded, partly flattened bundles. The bundles of the outer layer begin at the base of the heart from the fibrous rings of both ventricles and partly from the roots of the pulmonary trunk and aorta. On the front surface of the heart, the outer bundles go from right to left, and on the back - from left to right. At the apex of the left ventricle, both bundles of the outer layer form the so-called whirlpool of the heart and penetrate into the depths of the walls of the heart, passing into the deep muscle layer.

The deep layer consists of bundles that rise from the top of the heart to its base. They have a cylindrical, partly oval shape, are repeatedly split and reconnected, forming loops of various sizes. The shorter of these bundles do not reach the base of the heart, they are directed obliquely from one wall of the heart to another, in the form of fleshy crossbars. The crossbars are located in large numbers along the entire inner surface of both ventricles and have different sizes in different areas. Only the inner wall (septum) of the ventricles, immediately below the arterial openings, is devoid of these crossbars.

A number of such short, but more powerful muscle bundles, partly connected with both the middle and outer layers, freely protrude into the cavity of the ventricles, forming papillary muscles of various sizes and cones.

There are three papillary muscles in the cavity of the right ventricle, and two in the cavity of the left. Tendon strings begin from the top of each of the papillary muscles, through which the papillary muscles are connected to the free edge and partly the lower surface of the cusps of the tricuspid or mitral valves.

However, not all tendon strings are associated with the papillary muscles. A number of them begin directly from the fleshy crossbars formed by the deep muscle layer and are most often attached to the lower, ventricular, surface of the valves.

The papillary muscles with tendinous strings hold the cusp valves when they are slammed by blood flow from the contracted ventricles (systole) to the relaxed atria (diastole). Encountering, however, obstacles from the valves, the blood rushes not into the atria, but into the opening of the aorta and pulmonary trunk, the semilunar valves of which are pressed by the blood flow against the walls of these vessels and thereby leave the lumen of the vessels open.

Located between the outer and deep muscle layers, the middle layer forms a number of well-defined circular bundles in the walls of each ventricle. The middle layer is more developed in the left ventricle, so the walls of the left ventricle are much thicker than the right one. The bundles of the middle muscle layer of the right ventricle are flattened and have an almost transverse and somewhat oblique direction from the base of the heart to the apex.

In the left ventricle, among the bundles of the middle layer, bundles lying closer to the outer layer and located closer to the deep layer can be distinguished.

The interventricular septum is formed by all three muscular layers of both ventricles. However, the muscle layers of the left ventricle take a large part in its formation. Its thickness is almost equal to the thickness of the wall of the left ventricle. It protrudes towards the cavity of the right ventricle. For 4/5, it represents a well-developed muscle layer. This, much larger, part of the interventricular septum is called the muscular part.

The upper (1/5) part of the interventricular septum is thin, transparent and is called the membranous part. The septal leaflet of the tricuspid valve is attached to the membranous part.

The muscles of the atria are isolated from the muscles of the ventricles. An exception is a bundle of fibers starting in the atrial septum in the region of the coronary sinus of the heart. This bundle consists of fibers with a large amount of sarcoplasm and a small amount of myofibrils; the bundle also includes nerve fibers; it originates at the confluence of the inferior vena cava and goes to the ventricular septum, penetrating into its thickness. In the bundle, the initial, thickened part, called the atrioventricular node, is distinguished, passing into a thinner trunk - the atrioventricular bundle, the bundle goes to the interventricular septum, passes between both fibrous rings and at the upper posterior part of the muscular part of the septum is divided into the right and left legs .

The right leg, short and thinner, follows the septum from the side of the cavity of the right ventricle to the base of the anterior papillary muscle and spreads in the muscular layer of the ventricle in the form of a network of thin fibers (Purkinje).

The left leg, wider and longer than the right one, is located on the left side of the ventricular septum, in its initial sections it lies more superficially, closer to the endocardium. Heading to the base of the papillary muscles, it breaks up into a thin network of fibers that form the anterior, middle and posterior bundles, spreading in the myocardium of the left ventricle.

At the confluence of the superior vena cava into the right atrium, between the vein and the right ear is the sinoatrial node.

These bundles and nodes, accompanied by nerves and their branches, are the conduction system of the heart, which serves to transmit impulses from one part of the heart to another.

Inner lining of the heart, or endocardium

The inner shell of the heart, or endocardium, is formed from collagen and elastic fibers, among which are located connective tissue and smooth muscle cells.

From the side of the cavities of the heart, the endocardium is covered with endothelium.

The endocardium lines all the cavities of the heart, is tightly fused with the underlying muscle layer, follows all its irregularities formed by the fleshy crossbars, the pectinate and papillary muscles, as well as their tendon outgrowths.

On the inner shell of the vessels leaving the heart and flowing into it - the hollow and pulmonary veins, the aorta and the pulmonary trunk - the endocardium passes without sharp boundaries. In the atria, the endocardium is thicker than in the ventricles, while it is thicker in the left atrium, less where it covers the papillary muscles with tendon strings and fleshy crossbars.

In the most thinned sections of the walls of the atria, where gaps form in the muscle layer, the endocardium is in close contact and even fuses with the epicardium. In the area of fibrous rings, atrioventricular openings, as well as openings of the aorta and pulmonary trunk, the endocardium, by doubling its leaf, duplication of the endocardium, forms the leaflets of the mitral and tricuspid valves and the semilunar valves of the pulmonary trunk and aorta. The fibrous connective tissue between both sheets of each of the cusps and semilunar valves is connected to the fibrous rings and thus fixes the valves to them.

Pericardial sac or pericardium

The pericardium, or pericardium, has the shape of an obliquely cut cone with a lower base located on the diaphragm and an apex reaching almost to the level of the angle of the sternum. In width, it extends more to the left than to the right.

In the pericardial sac, there are: an anterior (sternocostal) part, a posterior inferior (diaphragmatic) part, and two lateral - right and left - mediastinal parts.

The sternocostal part of the pericardial sac faces the anterior chest wall and is located, respectively, in the body of the sternum, V-VI costal cartilages, intercostal spaces and the left part of the xiphoid process.

The lateral sections of the sternocostal part of the pericardial sac are covered by the right and left sheets of the mediastinal pleura, which separate it in the anterior sections from the anterior chest wall. The areas of the mediastinal pleura covering the pericardium are distinguished under the name of the pericardial part of the mediastinal pleura.

The middle of the sternocostal part of the bag, the so-called free part, is open in the form of two triangular-shaped spaces: the upper, smaller, corresponding to the thymus gland, and the lower, larger, corresponding to the pericardium, facing their bases up (to the notch of the sternum) and down (to the diaphragm ).

In the region of the upper triangle, the sternocostal part of the pericardium is separated from the sternum by loose connective and adipose tissue, in which the thymus gland is embedded in children. The compacted part of this fiber forms the so-called superior sterno-periocardial ligament, which fixes here the anterior wall of the pericardium to the handle of the sternum.

In the area of the lower triangle, the pericardium is also separated from the sternum by loose tissue, in which a compacted part is isolated, the lower sterno-periocardio-adrenal ligament, which fixes the lower part of the pericardium to the sternum.

In the diaphragmatic part of the pericardial sac, there is an upper section involved in the formation of the anterior border of the posterior mediastinum, and a lower section covering the diaphragm.

The upper section is adjacent to the esophagus, thoracic aorta and unpaired vein, from which this part of the pericardium is separated by a layer of loose connective tissue and a thin fascial sheet.

The lower section of the same part of the pericardium, which is its base, fuses tightly with the tendon center of the diaphragm; extending slightly to the anterior areas of its muscular part, it is connected to them by loose fiber.

The right and left mediastinal parts of the pericardial sac are adjacent to the mediastinal pleura; the latter is connected to the pericardium by means of loose connective tissue and can be separated by careful preparation. In the thickness of this loose fiber, connecting the mediastinal pleura with the pericardium, passes the phrenic nerve and the accompanying pericardial-bag-diaphragmatic vessels.

The pericardium consists of two parts - internal, serous (serous pericardial sac) and external, fibrous (fibrous pericardial sac).

The serous pericardial sac consists of two serous sacs, as it were, nested one inside the other - the outer one, freely surrounding the heart (the serous sac of the pericardium itself), and the inner one - the epicardium, tightly fused with the myocardium. The serous cover of the pericardium is the parietal plate of the serous pericardial sac, and the serous cover of the heart is the visceral plate (epicardium) of the serous pericardial sac.

The fibrous pericardial sac, which is especially pronounced on the anterior wall of the pericardium, fixes the pericardial sac to the diaphragm, the walls of large vessels and through the ligaments to the inner surface of the sternum.

The epicardium passes into the pericardium at the base of the heart, at the confluence of large vessels: the hollow and pulmonary veins and the exit of the aorta and pulmonary trunk.

Between the epicardium and the pericardium there is a slit-like space (the cavity of the pericardial sac), containing a small amount of pericardial sac fluid, which wets the serous surfaces of the pericardium, thereby causing one serous plate to slide over the other during heart contractions.

As indicated, the parietal plate of the serous pericardial sac passes into the splanchnic plate (epicardium) at the site of entry and exit of large blood vessels from the heart.

If, after the removal of the heart, the pericardial sac is examined from the inside, then the large vessels in relation to the pericardium are located along its posterior wall in approximately two lines - the right, more vertical, and the left, somewhat inclined towards it. On the right line, the superior vena cava, two right pulmonary veins and the inferior vena cava lie from top to bottom, along the left line - the aorta, pulmonary trunk and two left pulmonary veins.

At the site of the transition of the epicardium into the parietal plate, several sinuses of various shapes and sizes are formed. The largest of these are the transverse and oblique sinuses of the pericardial sac.

Transverse sinus of the pericardial sac. The initial sections (roots) of the pulmonary trunk and aorta, adjacent to one another, are surrounded by a common leaf of the epicardium; posterior to them are the atria and next to the right is the superior vena cava. The epicardium from the side of the posterior wall of the initial sections of the aorta and the pulmonary trunk goes up and back to the atria located behind them, and from the latter - down and forward again to the base of the ventricles and the root of these vessels. Thus, between the aortic root and the pulmonary trunk in front and the atria behind, a passage is formed - a sinus, which is clearly visible when the aorta and pulmonary trunk are pulled anteriorly, and the superior vena cava - posteriorly. This sinus is bounded from above by the pericardium, from behind by the superior vena cava and the anterior surface of the atria, from the front by the aorta and the pulmonary trunk; the transverse sinus is open on the right and left.

Oblique sinus of the pericardial sac. It is located below and behind the heart and represents a space bounded in front by the posterior surface of the left atrium covered with epicardium, behind - by the posterior, mediastinal, part of the pericardium, on the right - by the inferior vena cava, on the left - by the pulmonary veins, also covered by the epicardium. In the upper blind pocket of this sinus there is a large number of nerve nodes and trunks of the cardiac plexus.

Between the epicardium covering the initial part of the aorta (up to the level of the brachiocephalic trunk leaving it), and the parietal plate continuing from it at this place, a small pocket is formed - the aortic protrusion. On the pulmonary trunk, the transition of the epicardium to the specified parietal plate occurs at the level (sometimes below) of the arterial ligament. On the superior vena cava, this transition is carried out below the place where the unpaired vein flows into it. On the pulmonary veins, the junction almost reaches the hilum of the lungs.

On the posterolateral wall of the left atrium, between the left superior pulmonary vein and the base of the left atrium, a fold of the pericardial sac passes from left to right, the so-called fold of the superior left vena cava, in the thickness of which lie the oblique vein of the left atrium and the nerve plexus.

The structure of the wall of the heart

The wall of the heart consists of three layers: the outer - the epicardium, the middle - the myocardium and the inner - the endocardium.

outer shell of the heart

Epicardium, epicardium (see Fig. 701, 702, 721), is a smooth, thin and transparent shell. It is a visceral plate, lamina visceralis, pericardium, pericardium. The connective tissue base of the epicardium in various parts of the heart, especially in the sulci and in the apex, includes adipose tissue. With the help of connective tissue, the epicardium is fused with the myocardium most tightly in places of the least accumulation or absence of adipose tissue (see "Pericardium").

Muscular layer of the heart

The muscular layer of the heart, or myocardium. The middle, muscular, membrane of the heart, myocardium (see Fig. 703, 704, 705, 706, 707, 708, 709, 710, 711, 712, 713, 714), or the heart muscle, is a powerful and significant part in thickness walls of the heart. The myocardium reaches its greatest thickness in the region of the wall of the left ventricle (11-14 mm), twice the thickness of the wall of the right ventricle (4-6 mm). In the walls of the atria, the myocardium is much less developed and its thickness here is only 2-3 mm.

Between the muscle layer of the atria and the muscle layer of the ventricles lies dense fibrous tissue, due to which fibrous rings are formed, right and left, anuli fibrosi, dexter et sinister (see Fig. 709). From the side of the outer surface of the heart, their location corresponds to the coronary sulcus.

The right fibrous ring, anulus fibrosus dexter, which surrounds the right atrioventricular orifice, is oval in shape. The left fibrous ring, anulus fibrosus sinister, surrounds the left atrioventricular opening on the right, left and behind and is horseshoe-shaped in shape.

With its anterior sections, the left fibrous ring is attached to the aortic root, forming triangular connective tissue plates around its posterior periphery - the right and left fibrous triangles, trigonum fibrosum dextrum et trigonum fibrosum sinistrum (see Fig. 709).

In the circumference of the openings of the aorta and pulmonary trunk (see Fig. 709) there are also interconnected fibrous rings; the aortic ring is connected to the fibrous rings of the atrioventricular orifices.

Muscular layer of the atria

In the walls of the atria, two muscle layers are distinguished: superficial and deep (see Fig. 710).

The superficial layer is common to both atria and consists of muscle bundles that run mainly in the transverse direction. They are more pronounced on the anterior surface of the atria, forming here a relatively wide muscle layer in the form of a horizontally located inter-auricular bundle (see Fig. 710), passing to the inner surface of both ears.

On the posterior surface of the atria, the muscle bundles of the superficial layer are partially woven into the posterior sections of the septum. On the back surface of the heart, between the bundles of the superficial layer of muscles, there is a depression covered with epicardium, limited by the mouth of the inferior vena cava, the projection of the atrial septum and the mouth of the venous sinus (see Fig. 702). In this area, the atrial septum includes nerve trunks that innervate the atrial septum and the ventricular septum - the atrioventricular bundle (Fig. 715).

The deep layer of muscles of the right and left atria is not common to both atria. It distinguishes between circular and vertical muscle bundles.

Circular muscle bundles lie in large numbers in the right atrium. They are located mainly around the openings of the vena cava, passing to their walls, around the coronary sinus of the heart, at the mouth of the right ear and at the edge of the oval fossa; in the left atrium, they lie mainly around the openings of the four pulmonary veins and at the beginning of the left ear.

Comb muscles, mm. pectinati, are also formed by bundles of the deep layer. They are most developed on the inner surface of the anterior right wall of the cavity of the right atrium, as well as the right and left ears; in the left atrium they are less pronounced. In the intervals between the comb muscles, the wall of the atria and ears is especially thinned.

On the inner surface of both ears there are short and thin bundles, the so-called fleshy trabeculae, trabeculae carneae. Crossing in different directions, they form a very thin loop-like network.

Muscular layer of the ventricles

In the muscular membrane (see Fig. 711) (myocardium) there are three muscle layers: outer, middle and deep. The outer and deep layers, passing from one ventricle to another, are common in both ventricles; the middle one, although connected with the other two layers, surrounds each ventricle separately.

The outer, relatively thin layer consists of oblique, partly rounded, partly flattened bundles. The bundles of the outer layer begin at the base of the heart from the fibrous rings of both ventricles and partly from the roots of the pulmonary trunk and aorta. On the sternocostal (anterior) surface of the heart, the external bundles go from right to left, and along the diaphragmatic (lower) surface - from left to right. At the top of the left ventricle, both bundles of the outer layer form the so-called curl of the heart, vortex cordis (see Fig. 711, 712), and penetrate into the depths of the walls of the heart, passing into the deep muscle layer.

The deep layer consists of bundles that rise from the top of the heart to its base. They are cylindrical, and some of the bundles are oval, split many times and reconnect, forming loops of various sizes. The shorter of these bundles do not reach the base of the heart, they are directed obliquely from one wall of the heart to another in the form of fleshy trabeculae. Only the interventricular septum immediately below the arterial openings is devoid of these crossbars.

A number of such short, but more powerful muscle bundles, partly connected with both the middle and outer layers, freely protrude into the cavity of the ventricles, forming cone-shaped papillary muscles of various sizes (see Fig. 704, 705, 707).

The papillary muscles with tendinous chords hold the valve flaps when they are slammed by blood flow from the contracted ventricles (during systole) to the relaxed atria (during diastole). Encountering obstacles from the valves, the blood rushes not into the atria, but into the openings of the aorta and pulmonary trunk, the semilunar valves of which are pressed by the blood flow against the walls of these vessels and thereby leave the lumen of the vessels open.

Located between the outer and deep muscle layers, the middle layer forms a number of well-defined circular bundles in the walls of each ventricle. The middle layer is more developed in the left ventricle, so the walls of the left ventricle are much thicker than the walls of the right. The bundles of the middle muscle layer of the right ventricle are flattened and have an almost transverse and somewhat oblique direction from the base of the heart to the apex.

The interventricular septum, septum interventriculare (see Fig. 704), is formed by all three muscle layers of both ventricles, but there are more muscle layers of the left ventricle. The thickness of the septum reaches mm, somewhat inferior to the thickness of the wall of the left ventricle. The interventricular septum is convex towards the cavity of the right ventricle and represents a well-developed muscle layer for 4/5. This much larger part of the interventricular septum is called the muscular part, pars muscularis.

The upper (1/5) part of the interventricular septum is the membranous part, pars membranacea. The septal leaflet of the right atrioventricular valve is attached to the membranous part.

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The wall of the heart includes three shells: the inner one - the endocardium, the middle one - the myocardium and the outer one - the epicardium.

Endocardium, endocardium, a relatively thin shell that lines the chambers of the heart from the inside. As part of the endocardium, there are: endothelium, subendothelial layer, muscular-elastic and external connective tissue. The endothelium is represented by only one layer of flat cells. The endocardium without a sharp border passes to large cardiac vessels. The cusps of the cuspid valves and the cusps of the semilunar valves represent a duplication of the endocardium.

Myocardium, the most significant membrane in thickness and the most important in function. The myocardium is a multitissue structure consisting of striated muscle tissue, loose and fibrous connective tissue, atypical cardiomyocytes, blood vessels, and nerve elements. The collection of contractile muscle cells makes up the heart muscle. The cardiac muscle has a special structure, occupying an intermediate position between striated and smooth muscles. The fibers of the heart muscle are capable of rapid contractions, are interconnected by jumpers, as a result of which a wide-loop network is formed, called syncytium. Muscle fibers are almost devoid of a sheath, their nuclei are in the middle. The contraction of the muscles of the heart is automatic. The muscles of the atria and ventricles are anatomically separate. They are connected only by a system of conductive fibers. The atrial myocardium has two layers: a superficial one, the fibers of which run transversely, covering both atria, and a deep separate one for each atrium. The latter consists of vertical bundles starting from the fibrous rings in the region of the atrioventricular openings and from circular bundles located at the mouths of the hollow and pulmonary veins.

The base of the ventricles, the atria are removed. Mitral valve lower left

Atypical cells of the conducting system, which form and conduct impulses, ensure the automaticity of the contraction of typical cardiomyocytes. They make up the conduction system of the heart.

Thus, in the composition of the muscular membrane of the heart, three functionally interconnected apparatuses can be distinguished:

1) Contractile, represented by typical cardiomyocytes;

2) Support formed by connective tissue structures around natural openings and penetrating into the myocardium and epicardium;

3) Conducting, consisting of atypical cardiomyocytes - cells of the conducting system.

epicardium, epicardium, covers the outside of the heart; under it are the own vessels of the heart and fatty tissue. It is a serous membrane and consists of a thin plate of connective tissue covered with mesothelium. The epicardium is also called the visceral plate of the serous pericardium, lamina visceralis pericardii serosi.

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Intestines

The intestine (intestinum) is the largest part of the digestive tube, which originates from the pylorus and ends at the anus. The intestine is involved not only in the digestion of food, its assimilation, but also in the production of many biological substances, such as hormones, which play a significant role in the body's immune status.

Its length is on average 4 meters in a living person (tonic state), and from 6 to 8 meters in an atonic state. In children in the neonatal period, the length of the intestine reaches 3.5 meters, increasing by 50% during the first year of life.

The gut undergoes changes with age. So, its length, shape, location changes. More intensive growth is observed from 1 to 3 years, when the child moves from breastfeeding to a common table. The diameter of the intestinum increases markedly during the first 24 months of life and after 6 years.

The length of the small intestine in a newborn is from 1.2 to 2.8 meters, in an adult from 2.3 to 4.2 meters.

The growth of the organism also affects the location of its loops. The duodenum in infants has a semicircular shape, is located at the level of the first lumbar vertebra, descending to 3-4 lumbar vertebrae by the age of 12. Its length does not change from birth to 4 years, and is from 7 to 13 cm, in children older than 7 years, fat deposits form around the duodenum, as a result, it becomes more or less fixed and less mobile.

After 6 months of life in a newborn, you can notice the difference and division of the small intestine into two sections: lean and ileal.

Anatomically, the entire intestine can be divided into thin and thick.

The first after the stomach is the small intestine. It is in it that digestion and absorption of certain substances takes place. The name was given because of the smaller diameter compared to the subsequent sections of the digestive tube.

In turn, the small intestine is divided into duodenal (duodenum), skinny, ileum.

The lower parts of the digestive tract are called the large intestine. The processes of absorption of most substances and the formation of chyme (slurry from digested food) occur here.

The entire large intestine has a more developed muscular and serous layers, a larger diameter, which is why they got their name.

caecum (caecum) and appendix, or appendix;
colon, which is divided into ascending, transverse, descending, sigmoid;
rectum (has departments: ampulla, anal canal and anus).

Parameters of different parts of the digestive tube

The small intestine (intestinum tenue) is 1.6 to 4.3 meters long. For men it is longer. Its diameter gradually decreases from the proximal to the distal part (from 50 to 30 mm). Intestinum tenue lies intraperitoneally, that is, intraperitoneally, its mesentery is a duplicate of the peritoneum. The leaves of the mesentery cover the blood vessels, nerves, lymph nodes and vessels, fatty tissue. The cells of intestinum tenue produce a large number of enzymes that take part in the process of digestion of food along with pancreatic enzymes, in addition, all drugs, toxins, when taken orally, are absorbed here.

The length of the colon is relatively less - 1.5 meters. Its diameter decreases from beginning to end from 7-14 to 4-6 cm. As described above, it has 6 divisions. Caecum has an outgrowth, a vestigial organ, the appendix, which most scientists believe is an important part of the immune system.

Throughout the colon there are anatomical formations - bends. This is the place of transition of one part of it into another. So, the transition of the ascending to the transverse colon is called the hepatic flexure, and the splenic flexure is formed by the transverse descending sections.

The intestines are supplied with blood by the mesenteric arteries (upper and lower). The outflow of venous blood is carried out through the veins of the same name, which make up the pool of the portal vein.

The intestines are innervated by motor and sensory fibers. The motor fibers include the spinal and vagus nerve branches, and the sensory fibers of the sympathetic and parasympathetic nervous systems.

duodenum (duodenum)

It starts from the pyloric zone of the stomach. Its length is on average 20 cm. It bypasses the head of the pancreas in the form of the letter C or a horseshoe. This anatomical formation is surrounded by important elements: the common bile duct and the liver with the portal vein. The loop that forms around the head of the pancreas has a complex structure:

It is the upper part that forms the loop, starting at the level of the 12th thoracic vertebra. It smoothly turns into a descending one, its length is not more than 4 cm, then it goes almost parallel to the spinal column, reaching the 3rd lumbar vertebra, turns to the left. This forms the bottom bend. The descending duodenum is up to 9 cm on average. Important anatomical formations are also located near it: the right kidney, the common bile duct and the liver. Between the descending duodenum and the head of the pancreas there is a groove in which the common bile duct lies. Along the way, it reunites with the pancreatic duct and, on the surface of the major papilla, flows into the cavity of the digestive tube.

The next part is horizontal, which is located horizontally at the level of the third lumbar vertebra. It is adjacent to the inferior vena cava, then gives rise to the ascending duodenum.

The ascending duodenum is short, no more than 2 cm, it turns sharply and passes into the jejunum. This small bend is called the duodenum-skinny, attached to the diaphragm with the help of muscles.

The ascending duodenum passes next to the mesenteric artery and vein, the abdominal aorta.

Its location is retroperitoneal almost throughout, except for its ampullar part.

Skinny (jejunum) and ileum (ileum)

Two departments of intestinum, which have almost the same structure, so they are often described together.

Loops of jejunum are located in the abdominal cavity on the left, it is covered on all sides by serosa (peritoneum). Anatomically, jejunum and ileum are part of the mesenteric part of the intestinum tenue, they have a well-defined serous membrane.

There are no special differences in the anatomy of jejunum and ileum. The exception is a larger diameter, thicker walls, a markedly greater blood supply. The mesenteric part of the small intestine is almost completely covered with an omentum.

The length of the jejunum is up to 1.8 meters in tonic tension, after death it relaxes and increases in length up to 2.4 meters. The muscular layer of its walls provides contractions, peristalsis and rhythmic segmentation.

Ileum is separated from the blind by a special anatomical formation - the Bauhinian damper. It is also called the ileocecal valve.

Jejunum occupies the lower floor of the abdominal cavity, flows into the caecum in the region of the iliac fossa on the right. It is completely covered by the peritoneum. Its length is from 1.3 to 2.6 meters. In the atonic state, it is able to stretch up to 3.6 meters. Among its functions, in the first place are digestion, absorption of food, its promotion to the subsequent sections of the intestinum with the help of peristaltic waves, as well as the production of neurotensin, which is involved in the regulation of drinking and eating behavior of a person.

caecum (caecum)

This is the beginning of the large intestine, the caecum is covered on all sides by the peritoneum. It resembles a bag in shape, in which the length and diameter are almost equal (6 cm and 7-7.5 cm). Caecum is located in the right iliac fossa, bounded on both sides by sphincters, whose function is to ensure one-way flow of chyme. On the border with the intestinum tenue, this sphinker is called the Bauginian damper, and on the border of the cecum and colon, the sphincter of Busi.

It is known that the appendix is a process of the caecum, which extends just below the ileocecal angle (the distance ranges from 0.5 cm to 5 cm). It has a distinctive structure: in the form of a narrow tube (diameter up to 3-4 mm, length from 2.5 to 15 cm). Through a narrow opening, the process communicates with the cavity of the intestinal tube, in addition, it has its own mesentery connected to the caecum and ileum. Typically, the appendix is located in almost all people typically, that is, in the right iliac region, and with its free end reaches the small pelvis, sometimes drops below. There are also atypical location options that are rare and cause difficulties during surgery.

The structure and function of the small intestine

The small intestine is a tubular organ of the digestive system, in which the transformation of the food bolus into a soluble compound continues.

Organ structure

The small intestine (intestinum tenue) departs from the gastric pylorus, forms many loops and passes into the large intestine. In the initial section, the circumference of the intestine is 40-50 mm, at the end 20-30 mm, the length of the intestine can reach up to 5 meters.

The duodenum (duodenum) is the shortest (25–30 cm) and widest part. It has the shape of a horseshoe, comparable in length to the width of 12 fingers, due to which it got its name;
The jejunum (length 2–2.5 meters);
Ileum (length 2.5–3 meters).

The wall of the small intestine is made up of the following layers:

The mucous membrane - lines the inner surface of the body, 90% of its cells are enterocytes, which provide digestion and absorption. Has a relief: villi, circular folds, crypts (tubular protrusions);
Own plate (submucosal layer) - an accumulation of fat cells, nerve and vascular plexuses are also located here;
The muscular layer is formed by 2 shells: circular (inner) and longitudinal (outer). Between the membranes is the nerve plexus, which controls the contraction of the intestinal wall;
Serous layer - covers the small intestine from all sides, with the exception of the duodenum.

The small intestine is supplied with blood by the hepatic and mesenteric arteries. Innervation (supply of nerve fibers) comes from the plexuses of the autonomic nervous system of the abdominal cavity and the vagus nerve.

Digestion process

The following processes of digestion take place in the small intestine:

To digest the food bolus, the intestine produces the following enzymes:

Erepsin - breaks down peptides to amino acids;
Enterokinase, trypsin, kinasogen - break down simple proteins;
Nuclease - digests complex protein compounds;
Lipase - dissolves fats;
Lactose, amylase, maltose, phosphatase - break down carbohydrates.

The mucous membrane of the small intestine produces 1.5–2 liters of juice per day, which consists of:

The small intestine produces the following hormones:

Somatostotin - prevents the release of gastrin (a hormone that enhances the secretion of digestive juices);
Secretin - regulates the secretion of the pancreas;
Vasointestinal peptide - stimulates hematopoiesis, affects the smooth muscles in the intestine;
Gastrin - involved in digestion;
Motilin - regulates intestinal motility);
Cholecystokinin - causes contraction and emptying of the gallbladder;
Gastroinhibiting polypeptide - inhibits the secretion of bile.

Functions of the small intestine

The main functions of the body include:

Secretory: produces intestinal juice;
Protective: the mucus contained in the intestinal juice protects the intestinal walls from chemical influences, aggressive irritants;
Digestive: breaks down the food bolus;
Motor: due to the muscles, the chyme (liquid or semi-liquid contents) moves through the small intestine, mixing with gastric juice;
Suction: the mucous membrane absorbs water, vitamins, salts, nutrients and medicinal substances, which are carried throughout the body through the lymphatic and blood vessels;
Immunocompetent: prevents the penetration and reproduction of opportunistic microflora;
Removes toxic substances, toxins from the body;
Endocrine: produces hormones that affect not only the digestive process, but also other body systems.

Diseases of the small intestine:

Enteritis;
celiac disease

The structure of the small and large intestines for dummies

I was going to write a review about a new type of surgical operations on the intestines, but I thought that first I need to tell about structure this same intestine. When I was in school, I sometimes confused which gut goes for which. Therefore, today we are eliminating this gap. You even know which gut was named hungry and why.

READ ALSO: Where is the intestine and where is the stomach

Will be a short course in anatomy, get ready. Unnecessary thrown out, here - only the most interesting.

human intestine consists of two departments - thin and thick. Why was it called that? The diameter of the small intestine at the beginning is 4-6 cm and gradually decreases up to 2.5-3 cm. The large intestine has average diameter 4-10 cm. In appearance, even a student with a poor student will distinguish them, but more on that below.

(the names are English, although they are similar to Latin)

small intestine- small intestine.

colon- colon(part of the large intestine).

Rectum- rectum.

When I was preparing this material, I almost got confused: textbooks contain different numbers about the length of the small intestine. The solution is simple: alive The length of the human small intestine is 3.5 - 4 meters, a at the dead - about 6-8 m due to loss of bowel tone, that is, 2 times more. Large intestine length much less - 1.5 - 2 meters.

Small intestine

The small intestine has 3 departments:

duodenum 12(lat. duodenum, read "duodenum", stress everywhere on the penultimate syllable, if I did not highlight otherwise): the initial section of the small intestine, has the shape of the letter "C" and length 25-30 cm(21 cm in a living person), goes around the head of the pancreas, they flow into it common bile duct and main pancreatic duct(sometimes there is an additional pancreatic duct). The name is given according to the length of this intestine, which ancient anatomists measured on the fingers(linear was not used). The finger in ancient times in Russia was called finger("index finger").
jejunum(jejunum, jejunum - empty, hungry): represents upper half small intestine. You didn’t have a question why the gut was called “ hungry"? Just at the autopsy, it often turned out to be empty.
ileum(ileum, Ileum - from the Greek ileos to twist): is lower half small intestine. There is no clear boundary between the jejunum and the ileum, and they themselves are very similar in appearance. Therefore, anatomists agreed that the upper 2/5 of the small intestine is jejunum, a lower 3/5 - ileum. Calculate the length in meters yourself.

SECTIONS OF THE SMALL INTESTINE in Latin.

Duodenum- 12-ringed intestine.

Jejunum- skinny intestine.

Ileum- iliac intestine.

Inflammation of the duodenum is called duodenitis(heard the term gastroduodenitis?). In practice, inflammation of the jejunum and ileum is not isolated separately, but is called the general term enteritis(inflammation of the small intestine) from Greek enteron- intestines.

Typical microscopic structure of the intestinal wall is (from the inside to the outside):

mucous membrane,
submucosa,
muscle layer:
- internal circular (circular),
- outer longitudinal (only three ribbons remain from it in the large intestine, about them below),
serous (outer) layer.

LAYERS OF THE INTESTINAL WALL

(see the pronunciation of Latin words in brackets, the rest - in the English-Russian dictionary)

mucosa (mucosa) - mucous membrane,

submucosa (submucosa) - submucosal,

muscularis (muscularis) - muscle layer(inner - inner, outer - outer),

serosa (serosa) - serosa(here is the peritoneum),

Mesentery(mesenterium, mezentErium) is a fold of the peritoneum that attaches the intestines to the back wall of the abdominal cavity; it contains blood vessels and nerves. You can compare the structure of the intestinal wall with the structure of the esophagus wall, which I wrote about earlier in the article on poisoning with vinegar essence.

Colon

Let's move on to large intestine. One of my favorite questions in anatomy is to name the external difference between large intestine and small intestine. There are 5 of them, if I haven't forgotten:

grayish color,
large diameter
the presence of three longitudinal muscle bands(this is what is left of the longitudinal muscle layer of the wall),
Availability swelling(protrusions of the wall) - gaustr (haustrum),
Availability omental processes(fat supplements).

FEATURES OF THE LARGE INTESTINE

(clockwise from its start)

Ileum - ileum

Vermiform appendix - appendix (appendix),

Cecum - caecum

Ileocecal valve - ileocecal valve,

Superior mesenteric artery - superior mesenteric artery,

Right colic flexure - right colon bend,

Transverse mesocolon - mesentery of the transverse colon,

Left colic flexure - left colic bend,

epiploic appendages- fat supplements,

Tenia coli- muscle band,

Inferior mesenteric artery - inferior mesenteric artery,

Sigmoid mesocolon - mesentery of the sigmoid colon,

Rectum - rectum

Anal canal - anal canal.

Colon has several departments:

cecum(cecum or caecum, cecum): length 1 - 13 cm; This is the section of the large intestine below the confluence of the ileum, that is, below the ileocecal valve. A appendix (appendix) departs from the convergence of the three ribbons, which can be directed not only downward, but also in any other direction.
ascending colon(colon ascendens, colon ascendance)
transverse colon(colon transversum, colon transversum)
descending colon(colon descendens, colon descendens)
sigmoid colon(colon sigmoideum, colon sigmoideum): the length is very variable, up to 80-90 cm.
rectum(rectum, rectum): length 12-15 cm. Diseases of this intestine are dealt with by doctors of a separate specialty - proctologists (from the Greek proktos - anus). I will not describe the structure of the rectum here, this is a complex topic.

SECTIONS OF THE LARGE INTESTINE(in order)

cecum- cecum,

ascending colon- ascending colon,

transverse colon- transverse colon,

descending colon- descending colon,

sigmoid-colon sigmoid colon,

rectum- rectum.

I told the structure of the intestines in a simplified form. Students learn in more detail: how they are covered with a peritoneum, whether they have a mesentery, how they are supplied with blood, what they border on, etc.

Inflammation of the large intestine is called colitis. Inflammation of the rectum should be called proctitis, but this term is rarely used. More commonly used paraproctitis- inflammation of the tissue around the rectum (a couple - about).

Update as of February 29, 2008. Inflammation of the caecum is called typhlitis(from the Greek typhlon - caecum). You are unlikely to need a name, but added here for encyclopedic presentation.

What is interesting: the small and large intestines differ not only in structure and function. They get sick differently. Diarrhea (diarrhea) with enteritis sharp in appearance different from diarrhea in colitis. But more about that some other time. If there are people who want to read. 🙂

The automatism of the heart is its ability to rhythmically contract without any visible irritation under the influence of impulses that arise in the organ itself.

Automation of the heart, the nature of the rhythmic excitation of the heart, the structure and functions of the conduction system. Automatic Gradient. Disturbances in the rhythm of the heart (blockade, extrasystole).

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, arise from the superior 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, as well as artery of the 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 of the gastrocnemius muscle and the 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, envelope of the ilium,a. circumflexa iliaca superjicialis, goes in a lateral direction parallel to the 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 of the 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 the 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 off 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, are sent to the 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.

The projection of the mitral valve is 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 bloodstream, on the attachment to the chest of that 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.