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In which human organ are immune cells located? The immune system: what it is, its organs and functions

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Immunity(from Latin immunitas - to free from something) is a physiological function that makes the body immune to foreign antigens. Human immunity makes him immune to many bacteria, viruses, fungi, worms, protozoa, and various animal poisons. In addition, the immune system protects the body from cancer cells.

The task of the immune system is to recognize and destroy all foreign structures. Upon contact with a foreign structure, cells of the immune system trigger an immune response, which leads to the removal of the foreign antigen from the body.

The function of immunity is ensured by the work of the body's immune system, which includes various types of organs and cells. Below we will consider in more detail the structure of the immune system and the basic principles of its functioning.

Anatomy of the immune system
The anatomy of the immune system is extremely heterogeneous. In general, cells and humoral factors of the immune system are present in almost all organs and tissues of the body. The exception is some parts of the eyes, testicles in men, thyroid gland, brain - these organs are protected from the immune system by a tissue barrier, which is necessary for their normal functioning.

In general, the functioning of the immune system is ensured by two types of factors: cellular and humoral (that is, liquid). Cells of the immune system (various types of leukocytes) circulate in the blood and pass into tissues, carrying out constant surveillance of the antigenic composition of tissues. In addition, a large number of different antibodies (humoral, fluid factors) circulate in the blood, which are also capable of recognizing and destroying foreign structures.

In the architecture of the immune system, we distinguish between central and peripheral structures. Central organs of the immune system are bone marrow and thymus (thymus gland). In the bone marrow (red bone marrow), the formation of cells of the immune system occurs from the so-called stem cells, which give rise to all blood cells (erythrocytes, leukocytes, platelets). The thymus gland (thymus) is located in the chest, just behind the sternum. The thymus is well developed in children, but with age it undergoes involution and is practically absent in adults. In the thymus, differentiation of lymphocytes - specific cells of the immune system - occurs. In the process of differentiation, lymphocytes “learn” to recognize “their” and “foreign” structures.

Peripheral organs of the immune system represented by lymph nodes, spleen and lymphoid tissue (such tissue is located, for example, in the palatine tonsils, at the root of the tongue, on the posterior wall of the nasopharynx, in the intestines).

Lymph nodes They are a collection of lymphoid tissue (actually a collection of cells of the immune system) surrounded by a membrane. A lymph node contains lymphatic vessels through which lymph flows. Inside the lymph node, the lymph is filtered and cleared of all foreign structures (viruses, bacteria, cancer cells). The vessels leaving the lymph node merge into a common duct, which flows into a vein.

Spleen is nothing more than a large lymph node. In an adult, the mass of the spleen can reach several hundred grams, depending on the amount of blood accumulated in the organ. The spleen is located in the abdominal cavity to the left of the stomach. A large amount of blood is pumped through the spleen per day, which, like lymph in the lymph nodes, undergoes filtration and purification. Also, a certain amount of blood is stored in the spleen, which the body does not currently need. During physical activity or stress, the spleen contracts and releases blood into the blood vessels in order to satisfy the body's need for oxygen.

Lymphoid tissue scattered throughout the body in the form of small nodules. The main function of lymphoid tissue is to provide local immunity, therefore the largest accumulations of lymphoid tissue are located in the mouth, pharynx and intestines (these areas of the body are abundantly populated by a variety of bacteria).

In addition, in various organs there are so-called mesenchymal cells, which can perform an immune function. There are many such cells in the skin, liver, and kidneys.

Immune system cells
The general name for cells of the immune system is leukocytes. However, the leukocyte family is very heterogeneous. We distinguish two main types of leukocytes: granular and non-granular.

Neutrophils- the most numerous representatives of leukocytes. These cells contain an elongated nucleus divided into several segments, so they are sometimes called segmented leukocytes. Like all cells of the immune system, neutrophils are formed in the red bone marrow and, after maturation, enter the blood. The circulation time of neutrophils in the blood is not long. Within a few hours, these cells penetrate the walls of blood vessels and move into the tissue. After spending some time in the tissues, neutrophils can return to the blood. Neutrophils are extremely sensitive to the presence of inflammation in the body and are able to migrate directionally into inflamed tissues. Once in the tissue, neutrophils change their shape - from round they turn into branched ones. The main function of neutrophils is the neutralization of various bacteria. To move through tissues, the neutrophil is equipped with peculiar legs, which are outgrowths of the cell cytoplasm. Moving towards the bacterium, the neutrophil surrounds it with its processes, and then “swallows” and digests it with the help of special enzymes. Dead neutrophils accumulate in areas of inflammation (for example, in wounds) in the form of pus. The number of blood neutrophils increases during various inflammatory diseases of a bacterial nature.

Basophils take an active part in the development of immediate allergic reactions. Once in the tissue, basophils turn into mast cells containing large amounts of histamine, a biologically active substance that stimulates the development of allergies. Thanks to basophils, the poisons of insects or animals are immediately blocked in the tissues and do not spread throughout the body. Basophils also regulate blood clotting with the help of heparin.

Lymphocytes. There are several types of lymphocytes: B-lymphocytes (read “B-lymphocytes”), T-lymphocytes (read “T-lymphocytes”), K-lymphocytes (read “K-lymphocytes”), NK-lymphocytes (natural killer cells) and monocytes .

B lymphocytes recognize foreign structures (antigens) while producing specific antibodies (protein molecules directed against foreign structures).

T lymphocytes perform the function of regulating immunity. T-helpers stimulate the production of antibodies, and T-suppressors inhibit it.

K lymphocytes capable of destroying foreign structures labeled with antibodies. Under the influence of these cells, various bacteria, cancer cells or cells infected with viruses can be destroyed.

NK lymphocytes exercise control over the quality of body cells. At the same time, NK lymphocytes are capable of destroying cells that differ in their properties from normal cells, for example, cancer cells.

Monocytes These are the largest blood cells. Once in the tissue, they turn into macrophages. Macrophages are large cells that actively destroy bacteria. Macrophages accumulate in large quantities in areas of inflammation.

Compared to neutrophils (see above), some types of lymphocytes are more active against viruses than bacteria, and are not destroyed during a reaction with a foreign antigen, therefore, pus does not form in areas of inflammation caused by viruses. Lymphocytes also accumulate in areas of chronic inflammation.

The leukocyte population is constantly renewed. Millions of new immune cells are formed every second. Some immune system cells only live for a few hours, while others can persist for several years. This is the essence of immunity: once it encounters an antigen (virus or bacteria), the immune cell “remembers” it and reacts faster the next time it encounters it, blocking the infection immediately after it enters the body.

The total mass of organs and cells of the immune system of an adult human body is about 1 kilogram. The interactions between cells of the immune system are extremely complex. In general, the coordinated work of various cells of the immune system ensures reliable protection of the body from various infectious agents and its own mutated cells.

In addition to their protective function, immune cells control the growth and reproduction of body cells, as well as tissue restoration in areas of inflammation.

In addition to the cells of the immune system in the human body, there are a number of nonspecific defense factors that constitute the so-called species immunity. These protective factors are represented by the complement system, lysozyme, transferrin, C-reactive protein, interferons.

Lysozyme is a specific enzyme that destroys the walls of bacteria. Lysozyme is found in saliva in large quantities, which explains its antibacterial properties.

Transferin is a protein that competes with bacteria to capture certain substances (for example, iron) necessary for their development. As a result, the growth and reproduction of bacteria slows down.

C-reactive protein is activated like a compliment when foreign structures enter the blood. The attachment of this protein to bacteria makes them vulnerable to cells of the immune system.

Interferons- These are complex molecular substances that are released by cells in response to the penetration of viruses into the body. Thanks to interferons, cells become immune to the virus.

Bibliography:

Khaitov R.M. Immunogenetics and immunology, Ibn Sina, 1991
Leskov, V.P. Clinical immunology for doctors, M., 1997
Borisov L.B. Medical Microbiology, Virology, Immunology, M.: Medicine, 1994

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Immune system -- system organ system, which exists in vertebrates and includes organs and tissues that protect the body from disease by identifying and destroying tumor cells and pathogens.

Immunity(lat. immunitas- liberation, getting rid of something) - insensitivity, resistance of the body to infections and invasions of foreign organisms (including pathogens), as well as the effects of foreign substances with antigenic properties. Immune reactions also occur against the body’s own cells that are antigenically altered.

Structure and composition of the immune system. The human immune system includes central organs - bone marrow and thymus gland (thymus) - and peripheral organs - spleen, lymph nodes, lymphoid tissue. These organs produce several types of cells, which supervise the constancy of the cellular and antigenic composition of the internal environment.

The main cells of the immune system are phagocytes And lymphocytes (B and T lymphocytes). They circulate through the circulatory and lymphatic systems, and some of them can penetrate tissues. All cells of the immune system have certain functions and work in a complex interaction, which is ensured by the production of special biologically active substances - cytokines . You've probably heard names like interferons , interleukins and the like.

Lymphocytes produce specific proteins ( antibodies ) - immunoglobulins , interacting with certain antigens and binding them. Antibodies neutralize the activity of poisons and microbes, making them more accessible to phagocytes.

The immune system “remembers” those foreign substances that it has encountered and reacted to at least once. The formation of immunity to “foreign” agents, tolerance to one’s own biologically active substances and increased sensitivity to allergens depends on this. A normally functioning immune system does not react to internal factors and, at the same time, rejects foreign influences on the body. It forms immunity - anti-infective, transplantation, anti-tumor. Immunity protects the body from infectious diseases, frees it from dead, degenerated and foreign cells. Immune reactions cause rejection of transplanted organs and tissues. With congenital or acquired defects of the immune system, diseases arise - immunodeficiency, autoimmune or allergic, caused by the body's increased sensitivity to allergens .

Types of immunity . Distinguish between natural and artificial immunity

A person is already immune to many diseases from birth. This immunity is called congenital . For example, people do not get sick from animal plague because their blood already contains ready-made antibodies. Innate immunity is inherited from parents. The body receives antibodies from the mother through the placenta or breast milk. Therefore, children who are bottle-fed often have a weakened immune system. They are more susceptible to infectious diseases and more likely to suffer from diabetes. Innate immunity lasts throughout life, but it can be overcome if the doses of the infecting agent increase or the body’s protective functions weaken.

In some cases, immunity occurs after illness. This acquired immunity . Having been ill once, people become immune to the pathogen. Such immunity can last for decades. For example, measles provides lifelong immunity. But with other infections, for example, influenza, sore throat, immunity does not last long, and a person can suffer from these diseases several times during his life. Innate and acquired immunity are called natural.

The main function of the immune system is to control the qualitative constancy of the genetically determined cellular and humoral composition of the body.

The immune system provides:

-Protection of the body from the introduction of foreign cells and from modified cells that have arisen in the body (for example, malignant);
- destruction of old, defective and damaged own cells, as well as cellular elements that are not characteristic of this phase of development of the body;
-neutralization with subsequent elimination of all high-molecular substances of biological origin that are genetically foreign to a given organism (proteins, polysaccharides, lipopolysaccharides, etc.).

The immune system consists of central (thymus and bone marrow) and peripheral (spleen, lymph nodes, accumulations of lymphoid tissue) organs in which lymphocytes differentiate into mature forms and the immune response occurs.

The functioning basis of the immune system is a complex complex of immunocompetent cells (T-, B-lymphocytes, macrophages).

Specific immune system , or as it is also called acquired, is developed gradually. The body gradually learns to distinguish “friends” from “strangers” thanks to immunological memory. This process is only possible through contact with bacteria, viruses and microorganisms. This protection is formed by two very important and closely related factors - cellular (T- and B-lymphocytes) and humoral (immunoglobulins - antibodies). The cellular factor remembers the foreign substance, and when it encounters it again, it quickly and effectively destroys it - this is immunological memory. This is exactly how vaccinations work - a strain of the virus is purposefully introduced into the body so that the T- and B-lymphocytes remember the virus and, when they encounter it again, quickly destroy it. T-lymphocytes destroy the virus on their own, and B-lymphocytes secrete special antibodies - immunoglobulins. You've probably seen them more than once in test results - they come in 5 types: IgE, IgA, IgG, IgM, IgD.

Immune system unites organs and tissues whose function is to protect the body from genetically foreign substances coming from outside or formed in the body itself. The organs of the immune system produce immunocompetent cells (lymphocytes, plasma cells), biologically active substances (antibodies) that recognize and destroy cells and other foreign substances (antigens) that have entered the body or formed in it.

The immune system includes all organs that are built from lymphoid tissue and carry out protective reactions in the body, create immunity-immunity to foreign antigenic substances.

The organs of the immune system include red bone marrow, thymus, tonsils, appendix, lymph nodes, spleen, accumulation of lymphoid tissue (lymphoid nodules) in the walls of the hollow internal organs of the digestive, respiratory systems and genitourinary apparatus (Fig. 360).

The bone marrow and thymus are the central organs of the immune system, where lymphocytes are formed from bone marrow stem cells. In the bone marrow, B lymphocytes are formed from its stem cells. In the thymus, differentiation of T-lymphocytes (thymus-dependent) occurs. B-lymphocytes and T-lymphocytes from the bone marrow and from the thymus through the bloodstream enter the peripheral organs of the immune system, which include tonsils, lymphoid (Peyr's) patches, appendix, single lymphoid nodules, lymph nodes and spleen.

Central authorities immune systems are located in the human body in well-protected places (bone marrow - in the bone marrow cavities, thymus - in the chest cavity, behind the manubrium of the sternum). Peripheral organs immune systems are located in places of possible penetration of foreign substances into the body or along the paths of their movement in the body itself. The tonsils are located in the walls of the initial section of the digestive tube and respiratory tract, on the border between the oral cavity, nose and the cavity of the pharynx and larynx. Lymphoid (Peyre's) plaques are located in the walls of the small intestine (mainly the ileum), the appendix is near the cecum, with a particularly abundant microflora.

In the mucous membrane of the digestive, respiratory and urinary tract organs there are numerous single lymphoid nodules that perform immune surveillance functions at the border of the body and the external environment (inhaled air, contents of the digestive tract). Lymph nodes, which are biological filters, lie on the paths of lymph flow (tissue fluid) from organs and tissues into the venous system. Particles of dead cells and coarse proteins, together with tissue fluid, enter the lymphatic channel, are retained and neutralized in the lymph nodes. The spleen, whose function is the immune control of blood, is located on the path of its flow from the arterial system to the portal vein.

Diffuse lymphoid tissue, represented by individual scattered cells of the lymphoid series, in some places forming not very dense cell clusters, is present in those organs where the antigenic danger is not very great. In places of constant antigenic potential

Rice. 360.Diagram of the location of the central and peripheral organs of the immune system in the human body.

1 - red bone marrow, 2 - thymus, 3 - lingual tonsil, 4 - palatine tonsil, 5 - tubal tonsil, 6 - pharyngeal tonsil, 7 - lymphoid nodules in the walls of the trachea and bronchi, 8 - lymph nodes (axillary), 9 - spleen, 10 - lymphoid nodules of the appendix, 11 - lymphoid nodules in the walls of the colon.

actions (tonsils, mucous membrane of the stomach, intestines, lymph nodes, spleen), lymphocytes form dense clusters measuring 0.5-1 mm, called lymphoid nodules, with reproduction centers (germentative centers).

Bone marrow(medulla ossium) is a hematopoietic organ and the central organ of the immune system. There are red bone marrow, which in an adult is located in the cells of the spongy substance of flat and short bones, the epiphyses of long (tubular) bones, and yellow bone marrow, which fills the bone marrow cavities of the diaphyses of long (tubular) bones. Red bone marrow contains hematopoietic stem cells - the precursors of all blood cells and the immune system (lymphocytes).

Thymus

Thymus(thymus), which was formerly called the thymus gland, is the central organ of immunogenesis. In the thymus, from stem cells coming here from the bone marrow with the blood flow, T-lymphocytes are formed, which leave the thymus with the blood flow and populate the thymus-dependent zones of the peripheral organs of immunogenesis. The thymus also secretes substances that affect the functions of T-lymphocytes.

The thymus consists of two asymmetrical right and left lobes, which are fused to each other at the level of their middle.

The thymus has a thin connective tissue capsule. The thymic parenchyma consists of darker cortex(cortex thymi) and lighter medulla(medulla thymi), occupying the central part of the thymus lobules. In the loops of the network formed by reticular fibers and cells, there are thymic lymphocytes(thymocytes), which lie more densely in the cortex than in the medulla, and stellate-shaped multi-processed epithelial cells - epithelioreticulocytes. The medulla also contains thymic corpuscles(corpuscula thymici), Hassal's bodies, formed by concentrically lying, highly flattened epithelial cells.

Innervation of the thymus: branches of the right and left vagus nerves, as well as branches of the cervicothoracic (stellate) and superior thoracic nodes of the sympathetic trunk.

Blood supply:branches of the internal mammary artery. Vienna The thymus drains into the brachiocephalic and internal mammary veins.

Tonsils

Tonsils:lingual and pharyngeal (unpaired), palatine and tubal (paired) - located in the area of the root of the tongue, pharynx and nasal part of the pharynx, respectively. They are diffuse accumulations of lymphoid tissue containing small, denser cell masses - lymphoid nodules.

Lingual tonsil (tonsilla lingualis) unpaired, located under the multilayered epithelium of the mucous membrane of the tongue root, often in the form of two accumulations of lymphoid tissue.

The surface of the tongue above the tonsil is lumpy, between the tubercles there are openings of the mucous glands located in the thickness of the root of the tongue.

The lingual tonsil reaches its largest size by the age of 14-20; its length is 18-25 mm and its width is 18-25 mm. The lingual tonsil does not have a capsule.

The lingual tonsil consists of lymphoid nodules, the number of which (80-90) is greatest in childhood, adolescence and young adulthood.

Innervation of the lingual tonsil: branches of the glossopharyngeal and vagus nerves, as well as sympathetic fibers of the external carotid plexus.

Blood supply:branches of the right and left lingual arteries. Venous blood drains into the lingual vein.

Pharyngeal tonsil (tonsilla pharyngealis), unpaired, is located in the vault of the pharynx, where diffuse lymphoid tissue and lymphoid nodules are located, mainly with reproductive centers.

Innervation:branches of the facial, glossopharyngeal, vagus nerves and sympathetic periarterial plexuses.

Blood supply:branches of the ascending pharyngeal arteries. Venous blood

Palatine tonsil (tonsilla palatina) steam room, located in the tonsillar fossa between the palatoglossal and velopharyngeal arches. The medial (free) surface of the tonsil faces the pharynx. On this surface there are almond dimples into which almond crypts open. In the thickness of the tonsil, along its crypts, there are lymphoid nodules, mainly with reproduction centers. Around the lymphoid nodules there is diffuse lymphoid tissue (Fig. 361).

Innervation:branches of the greater palatine nerve (from the pterygopalatine ganglion), the tonsil branch of the glossopharyngeal nerve and sympathetic fibers from the internal carotid plexus.

Blood supply:branches of the lingual, ascending pharyngeal and descending palatine arteries. Venous blood flows into the veins of the pterygoid plexus.

Tubal tonsil (tonsilla tubaria) steam room, located in the area of the tubal ridge, near the pharyngeal opening of the auditory tube. The tonsil consists of diffuse lymphoid tissue and a few lymphoid nodules.

Innervation:branches of the facial, glossopharyngeal and vagus nerves and periarterial sympathetic plexuses.

Blood supply:branches of the ascending pharyngeal artery. Venous blood flows into the veins of the pharyngeal plexus.

Appendix

Appendix (appendix, appendix vermiformis) extends from the lower part of the cecum, has numerous lymphoid nodules in its walls and internodular lymphoid tissue between them. The number of lymphoid nodules in the walls of the appendix in children and adolescents reaches 800, the nodules are located one above the other in 2-3 rows.

Innervation:fibers of the vagus nerves and the celiac (sympathetic) plexus.

Rice. 361.Microscopic structure of the palatine tonsil.

1 - crypts of the tonsil, 2 - integumentary epithelium, 3 - lymphoid nodules of the tonsil.

Blood supply:cecum branches of the ileocolic artery. Venous blood flows into the vein of the same name.

Lymphoid plaques of the small intestine

Lymphoid plaques (noduli lymphoidei aggregati), or group lymphoid nodules (Peyer's patches) are a cluster of lymphoid nodules located in the walls of the small intestine, mainly in its final section (Fig. 362). Lymphoid plaques look like oval or round formations, slightly protruding into the intestinal lumen. One plaque has from 5 to 150 or more lymphoid nodules, between which diffuse lymphoid tissue is located.

Single lymphoid nodules

Single lymphoid nodules (noduli lymphoidei solitarii) are present in the mucous membrane and submucosa of all tubular organs of the digestive, respiratory systems and genitourinary apparatus. Lymphoid nodules are located at different distances from each other and at different depths. Often the nodules lie so close to the epithelial cover that the mucous

Rice. 362.Group and single lymphoid nodules in the wall of the small intestine.

1 - serous membrane, 2 - muscular membrane, 3 - mucous membrane, 4 - mesentery of the small intestine, 5 - single lymphoid nodules, 6 - group lymphoid nodule (Peyer's patch), 7 - circular folds of the mucous membrane.

The melted shell rises above them in the form of small mounds. In the small intestine in childhood, the number of nodules varies from 1200 to 11000, in the large intestine - from 2000 to 9000, in the walls of the trachea - from 100 to 180, in the bladder - from 80 to 530. Diffuse lymphoid tissue is also present in the mucous membrane of all organs of the digestive, respiratory systems and genitourinary apparatus.

Innervationlymphoid nodules and lymphoid plaques are carried out along the branches of the vagus nerves and the celiac plexus.

Blood supply:peri-nodular hemocapillary networks formed by branches of organ arteries. Venous blood flows into the veins of the same name.

Spleen

Spleen(lien, splen), which carries out immune control of the blood, is located in the left hypochondrium, at the level of 9-11 ribs. The spleen has diaphragmatic and visceral surfaces. Diaphragmatic surface(facies diaphragmatica) facing the diaphragm. Anteromedial (visceral) surface(facies visceralis) contains the gate of the spleen, through which the artery and nerves enter the organ and the vein exits.

The spleen is covered on all sides by peritoneum, under which there is a thin fibrous membrane. Connective tissue trabeculae extend from the fibrous membrane into the organ, between which there is parenchyma, or pulp (pulp), spleen(pulpa splenica). Highlight red pulp(pulpa rubra), located between the venous vessels - the sinuses of the spleen, consisting of loops of reticular tissue filled with erythrocytes, leukocytes, lymphocytes, macrophages, and white pulp(pulpa alba), formed by periarterial lymphoid couplings, lymphoid nodules and macrophage-lymphoid couplings (ellipsoids), consisting of lymphocytes and other cells of lymphoid tissue (Fig. 363).

Periarterial lymphoid couplings in the form of several layers of lymphoid cells surround the pulp arteries along their entire length. Lymphoid nodules form in the thickness of the periarterial lymphoid couplings. Around the arterioles and capillaries there are 2-3 layers of cells of the lymphoid series - macrophage-lymphoid couplings (ellipsoids), which have a spindle shape.

Innervation of the spleen: sympathetic fibers from the celiac plexus and branches of the vagus nerves.

Blood supply:splenic artery. Venous blood flows through the splenic vein.

Lymph nodes

Lymph nodes (nodi lymphatici) are located on the paths of lymph flow from organs and tissues to the lymphatic ducts and lymphatic trunks flowing into large veins in the lower parts of the neck. Lymph nodes are biological filters for tissue fluid and the particles of cells contained in it that have died as a result of cellular renewal, and other foreign substances of endogenous and exogenous origin. Lymph flowing through the sinuses of the lymph nodes is filtered through loops of reticular tissue. The lymph receives lymphocytes formed in the lymphoid tissue of these lymph nodes. Lymph nodes are usually located in groups. Groups of lymph nodes are named by the area of their location: (inguinal, lumbar, etc.) or by the name of the blood vessel next to which they are located (celiac, iliac lymph nodes). Lymph nodes adjacent to the walls of cavities are called parietal, parietal lymph nodes(nodi lymphatici parietales), located near the internal organs - visceral lymph nodes(nodi lymphatici

Rice. 363.Diagram of the location of white pulp in the parenchyma of the spleen.

1 - fibrous membrane, 2 - trabecula of the spleen, 3 - venous sinuses, 4 - ellipsoid arteriole (ellipsoid), 5 - brush arterioles, 6 - central artery, 7 - lymphoid nodule, 8 - lymphoid periarterial coupling, 9 - red pulp , 10 - pulp artery, 11 - splenic vein, 12 - splenic artery, 13 - trabecular artery and vein.

viscerales). There are superficial and deep lymph nodes. The shape of the lymph nodes is very different.

On the outside, the lymph node is covered with a connective tissue capsule, from which capsular trabeculae extend into the organ. At the point where the lymphatic vessels exit the lymph node, there is a slight depression - gates(hilus), in the area of which the capsule thickens, forms a portal (hilar) thickening (Fig. 364). Portal (hilar) trabeculae extend from the portal thickening into the node. Through the gate, an artery, nerves enter the lymph node, veins and efferent lymphatic vessels exit. Between the trabeculae of the lymph node there are reticular fibers that form a network in the loops of which lymphoid tissue is located. The parenchyma of the lymph node is divided into cortex and medulla. Cortex(cortex) darker, occupies the peripheral parts of the node. Lighter medulla(medulla) lies closer to the gate of the lymph node. The cortex contains lymphoid nodules with and without a reproductive center. Around the lymphoid nodules there is diffuse lymphoid tissue, in which an internodular zone is distinguished - the cortical plateau. Inward from the lymphoid nodules, at the border with the medulla, there is a strip of lymphoid tissue called pericortical

Rice. 364.Microscopic structure of the lymph node.

1 - capsule, 2 - trabecula, 3 - afferent lymphatic vessel, 4 - subcapsular lymphatic sinus, 5 - cortical substance, 6 - poracortical (thymus-dependent) zone, 7 - lymphoid nodule, 8 - proliferation center of the lymphoid nodule, 9 - cortical lymphatic sinus , 10 - pulpal cords, 11 - cerebral sinuses, 12 - portal sinuses, 13 - efferent lymphatic vessel, 14 - portal thickening, 15 - blood vessels.

(paracortical) substance (paracortex), where there are mainly T-lymphocytes, as well as post-capillary venules. Through the walls of the venules, lymphocytes migrate into the bloodstream from the parenchyma of the lymph node and back. The medulla is formed by strands of lymphoid tissue - pulpy cords(chordae medullares), going from the cortex to the gate of the lymph node. Together with the lymphoid nodules, the pulp cords form the B-dependent zone.

lymphatic sinuses (sinus marginalis) to portal sinus(sinus hilaris). Along the capsular trabeculae lie cortical sinuses(sinus corticalis), along the pulpy cords are the sinuses of the medulla (sinus medullaris), which reach the gates of the lymphatic channel. Near the portal thickening, the sinuses of the medulla flow into the portal sinus located here. In the sinuses there is a fine-mesh network formed by reticular fibers and cells.

The parenchyma of the lymph node is penetrated by a dense network of narrow slits - lymphatic sinuses(sinus lymphaticus), through which the lymph entering the node flows from subcapsular (marginal) sinus(sinus marginalis) to portal sinus(sinus hilaris). Along the capsular trabeculae lie

cortical sinuses (sinus corticalis), along the pulpy cords - medullary sinuses(sinus medullaris), which reach the gates of the lymphatic bed. Near the portal thickening, the sinuses of the medulla flow into the portal sinus located here. In the sinuses there is a fine-mesh network formed by reticular fibers and cells.

Lymphatic system

Lymph nodes, lymphatic capillaries and vessels, ducts and trunks through which lymph flows are united under the general name - lymphatic system(systema lymphaticum) (Fig. 365).

Lymphatic capillaries (vasa lymphocapillaria) are the initial link of the lymphatic system. Tissue fluid, together with the substances it contains (large protein molecules, particles of dead cells, tumor cells), including foreign particles, is absorbed into the lumen of the lymphatic capillaries and is called lymph(lymph). Lymphatic capillaries are present in all organs and tissues of the human body, except for the brain and spinal cord, eyeball, inner ear, epithelial skin and mucous membranes, cartilage, splenic parenchyma, bone marrow and placenta. The diameter of lymphatic capillaries varies from 10 to 200 microns. When connected to each other, capillaries form in organs and tissues closed lymphocapillary networks(rete lymphocapillaria). The walls of lymphatic capillaries are built from a single layer of endothelial cells.

Lymphatic vessels (vasa lymphatica) are formed by the fusion of lymphatic capillaries. The walls of the lymphatic vessels are thicker, they consist of three layers (inner shell- tunica intima, middle shell- tunica media and outer shell- tunica externa). Lymphatic vessels have valves, the presence of which gives these vessels a characteristic bead-shaped appearance. The valves of the lymphatic vessels, formed by the folds of the inner membrane, allow lymph to pass in one direction - from the place of its formation in the capillaries towards the lymph nodes. From the lymph nodes, through their efferent lymphatic vessels, lymph flows either to the next (along the lymph flow) lymph nodes, or to the collector vessels - lymphatic trunks and lymphatic ducts, which flow into the venous angle formed on the right and left at the connection of the internal jugular and subclavian veins of the corresponding sides

Rice. 365.Human lymphatic system. Front view.

1 - lymphatic vessels of the face, 2 - submandibular lymph nodes, 3 - mental lymph nodes, 4 - mouth of the thoracic duct, 5 - anterior mediastinal lymph nodes, 6 - axillary lymph nodes, 7 - superficial ulnar lymph node, 8 - superficial lymphatic vessels of the forearm , 9 - lumbar lymph nodes, 10 - subaortic lymph node, 11 - common iliac lymph nodes, 12 - superficial inguinal lymph nodes, 13 - medial group of superficial lymphatic vessels of the leg, 14 - lateral group of superficial lymphatic vessels of the leg, 15 - superficial lymphatic vessels feet, 16 - deep lymphatic vessels of the foot, 17 - deep lymphatic vessels of the leg, 18 - deep lymphatic vessels of the thigh, 19 - deep lymphatic vessels of the palm, 20 - deep inguinal lymph nodes, 21 - external and internal iliac lymph nodes, 22 - deep lymphatics vessels of the forearm, 23 - thoracic duct, 24 - deep ulnar lymph node, 25 - intercostal lymph nodes, 26 - subclavian trunk, 27 - jugular trunk, 28 - deep cervical lymph nodes, 29 - jugular-digastric lymph node, 30 - mastoid lymph nodes nodes, 31 - preauricular lymph nodes.

Lymphatic trunks (trunci lymphatici) and lymphatic ducts(ductus lymphatici) are large lymphatic vessels that collect lymph (tissue fluid) from large parts of the body. There are six large lymphatic ducts and trunks in the human body. The thoracic duct, left jugular and left subclavian trunks flow into the left venous angle) into the right venous angle - the right lymphatic duct, right jugular and right subclavian trunks.

IN right subclavian trunk(truncus subclavius dexter) lymph flows from the right upper limb, into right jugular trunk(truncus jugularis dexter) - from the right half of the head and neck. IN right lymphatic duct(ductus lymphaticus dexter) the right bronchomediastinal trunk flows into, collecting lymph from the organs of the right half of the thoracic cavity.

Left subclavian trunk (truncus subclavius sinister) collects lymph from the left upper limb, left jugular trunk(truncus jugularis sinister) - from the left half of the head and neck. The largest lymphatic vessel, which also flows into the left venous angle, is thoracic duct(ductus thoracicus), through which lymph flows from the lower extremities, walls and organs of the pelvis and abdominal cavity, as well as the left half of the chest cavity.

The body is constantly under vigilant protection, which protects it from foreign particles. The defense system is immunity. It can be a collection of organs and tissues whose cells neutralize and remove harmful agents. Thanks to this defense system, people can fight diseases. Where is the human immune system located?

There is no clear answer to this question. Immunity is an abstract concept; it is not concentrated in one place, but is scattered throughout the body. Its failure leads to many adverse consequences. A person becomes vulnerable to foreign agents. He cannot fight infections and maintain his health. A number of pathological conditions arise. Depending on the mechanism of operation, immunity can be:

Cellular;
Humoral.

Each of them carries out its protective function through special cells. The first type is through T cells or T lymphocytes, which are divided into killer T cells, helper T cells, macrophages and neutrophils. Humoral is carried out thanks to B-lymphocytes and the antibodies they produce.

Another classification of immunity divides it into:

Nonspecific, otherwise congenital;
Specific, which is produced throughout life.

And also the protective system can be:

Natural, developed after an illness;
Artificial or passive, resulting from medical interventions - vaccination.

Where is

Immunity is a broad concept that combines many systems and tissues involved in the production of special substances. All protection bodies are divided into two large groups:

Central – thymus and bone marrow, which are responsible for the production of lymph cells;
Peripheral - spleen, lymph nodes, tonsils and groups of lymphoid formations. Their task is differentiation.

It is impossible to say where immunity is located in the human body. This is a general concept that reflects the work of many tissues and systems. The thymus, or otherwise the thymus gland, is the site of formation of cellular immunity, that is, T cells. This organ is located behind the sternum and has age-related characteristics. In children and young people it is actively developed, and involution occurs over the years. This is reflected in a decrease in protective activity among older people.

Another central organ of the immune system is the bone marrow. It is represented by soft spongy tissue, which is located in tubular and flat bones. Its task is the formation of blood cells - leukocytes and erythrocytes, as well as platelets. The bone marrow produces B lymphocytes, which are the weapon of the humoral response.

One of the organs of peripheral immunity is the spleen. Its role is reduced to lymph production, disposal of old and defective red blood cells, as well as storage of blood cells. The spleen is often called a blood depot and a graveyard of red blood cells. It is located in the abdominal area under the left hypochondrium.

Lymph nodes are called biological filters. These are small spherical formations, normally up to 1 cm in size. Lymph nodes follow the course of the arteries. There are submandibular, postauricular, supra- and subclavian, axillary, popliteal, inguinal nodes. They are connected by ducts and together form the lymphatic system. Inflammatory processes are often accompanied by an increase in these nodes. They can reach the size of a chicken egg.

lymphoid tissue that is located on both sides of the pharynx - these are the tonsils. Another similar island is localized in the intestinal walls and is called Peyer's patches. The exact place of their concentration is the appendix, which is also considered an immune organ. The ducts connecting the lymphoid formations contain lymph, a colorless liquid that includes a large number of defense cells.

Where is immunity located? It permeates the entire human body. Even where there are no protective tissues, there are lymph nodes and ducts. Defense never leaves its post. A person is under the control of a security system 24 hours a day.

How is it produced?

The role of all immune organs comes down to one thing – protective cells. Some form them, others differentiate, and others accumulate, while others act as a reservoir. The most important immune cell products include:

Thanks to the immune organs, the production of these cells is possible. They are direct participants in the battlefield. “Soldiers” of the defense system who fight against strangers who have broken into the body.

Functions

The main task of immunity is defense against unwanted substances. Among the main ones are:

Preventing the introduction of foreign agents through the presence of biological barriers;
Destruction of defective and old cells of the body whose life cycle has come to an end;
Neutralization of a harmful microbe when it enters;
Elimination, that is, removal of antigens.

What does human immunity depend on?

Defense mechanisms are formed under the influence of many factors that determine the strength of the response against antigens. An important role is played by:

Heredity is the genetic predisposition of a person, which he inherited from his parents. Immunity will directly depend on this factor;
The environment can also influence defense mechanisms to a large extent. Two twins who have similar genetic material but live in different environments will have different immune status;
The quality and quantity of food consumed, and, more precisely, its vitamin and mineral composition;
Lifestyle – his daily routine, work and rest schedule, the presence of bad habits;
Physical activity or lack thereof. Physical inactivity leads to the fact that the patient will be in a state of reduced muscle tone, gas exchange and, as a result, susceptible to immune disorders;
Acquired and congenital diseases.

These factors will be the answer to the question “what does human immunity depend on?”

Causes of weakened human immunity

The following diseases and conditions can trigger the process of reducing the body’s protective arsenal:

The causes of the external environment are:

Incorrect lifestyle, with increased psycho-emotional or physical stress, unbalanced diet and sleep disturbances;
Negative environmental conditions;
Addiction to alcohol, smoking;
Lack of vitamins and minerals.

The state of decreased protective function of the body requires mandatory correction. You need to increase your immunity under the supervision of a doctor. By studying the patient's medical history, conducting an examination and using diagnostic methods, the doctor can prescribe the necessary treatment without requiring the person to take medications. Raising your immune status is not an easy task, but it is doable. You can’t boost your immunity on your own without a doctor’s advice. The main thing is to strengthen your body wisely and prepare for it. Then climbing the ladder of health will be much more pleasant and interesting.

The environment around us - air, water, soil, objects - contain a lot of microorganisms that can harm human health. But thanks to the fact that the immune system guards our well-being, in most cases this does not happen. The immune system “fights” every minute with an army of bacteria and viruses, successfully “fighting off” all these harmful “attacks”.

The human immune system is very complex. It includes several organs connected to each other by a continuous network of lymphatic ducts.

The structure of the human immune system

The organs of the immune system include:

bone marrow;
thymus (thymus gland);
spleen;
lymph nodes and islands of lymphatic tissue.

Bone marrow

Bone marrow is located in the spongy bone tissue. The total weight of this organ is 2.5–3 kg. Bone marrow is a concentration of stem cells, which are the ancestors of all the formed blood elements we need.

Approximately 50% of the main weight of the bone marrow is a cluster of hematopoietic vessels that ensure the delivery of oxygen and necessary chemical compounds to the tissues. The porous structure of the vascular wall creates conditions for the penetration of nutrients inside.

There are two different types of bone marrow - red and yellow, between which there is no clearly defined boundary. The basis of red bone marrow is hematopoietic tissue, and yellow bone marrow is made up of adipose tissue. The red marrow produces blood cells, monocytes and B-lymphocytes. The yellow marrow is not involved in the formation of blood cells, but in some situations (for example, with blood loss), small foci of hematopoiesis may appear in it.

Over the years, the volume of red bone marrow in bone tissue decreases, and yellow bone marrow, on the contrary, increases. This is due to the fact that from the moment of puberty until old age, the processes of hematopoiesis begin to steadily fade away.

Thymus

The thymus (thymus gland) is located in the middle of the chest, in the retrosternal space. The shape of the thymus gland is a little like a fork with two prongs (hence the name thymus gland). At the time of birth, the weight of the thymus is 10–15 grams. In the first three years of life, the thymus gland grows extremely quickly.

From three to twenty years of age, the mass of the thymus remains the same and is about 26-29 grams. Then the involution (reverse development) of the organ begins. In older people, the mass of the thymus does not exceed 15 grams. With age, the structure of the thymus gland also changes - the thymus parenchyma is replaced by adipose tissue. In old people, this organ is 90% fatty.

The thymus gland has a bilobed structure. The upper and lower lobes of the gland have different sizes and shapes. On the outside it is covered with a connective tissue capsule. The connective tissue also penetrates into the thymus, thereby dividing it into lobules. The gland is divided into a cortical layer, in which growth and “instilling working skills” occurs in lymphocytes “born” in the bone marrow, and a medulla, the bulk of which consists of glandular cells.

The process of “reaching maturity” by lymphocytes, which occurs in the thymus gland, is extremely significant for the human immune system. In infants with congenital defects of the thymus - underdevelopment or complete absence of this organ, the functional development of the entire lymphatic system is disrupted, so life expectancy with this pathology rarely exceeds 12 months.

Spleen

The spleen is located on the left under the ribs and has the shape of a flattened and elongated hemisphere. In adults, the length of the spleen is 10-14 cm, width 6-10 cm, and thickness 3-4 cm. The weight of the organ in a man aged 20-40 is 192 grams, in a woman - 153 grams. Scientists have found that between 750 and 800 ml of blood passes through the spleen every day. Here, the formation of immunoglobulins of class M and J occurs as a reaction to the arrival of antigens, and the synthesis of factors that stimulate phagocytosis by leukocytes and macrophages. In addition, the spleen is a biological filter for xenobiotics, dead blood cells, bacteria and microflora.

Lymph nodes

Lymph nodes act as biological filters in the body for the lymphatic fluid flowing through them. They are located along the flow of lymph through the lymphatic vessels from organs and tissues.

As a rule, lymph nodes occur in groups of two to several dozen nodes. On the outside, the lymph nodes are protected by a capsule, inside of which there is a stroma consisting of reticular cells and fibers. Each lymph node includes from 1-2 to 10 small arteries that supply it with blood.

Islands of lymphatic tissue

Accumulations of lymphatic tissue located in the mucous membrane are also called lymphoid formations. Lymphoid formations are present in the pharynx, esophagus, stomach, intestines, respiratory organs, and urinary tract.

Islands of lymphatic tissue in the pharynx are represented by 6 tonsils of the lymphoid pharyngeal ring. Tonsils are a powerful collection of lymphoid tissue. They are uneven on top, which promotes food retention and creates a breeding ground for bacterial growth, which, in turn, serves as a trigger for immunological processes.

Lymphoid formations of the esophagus are lymph nodes deep in the folds of the esophagus. The task of the lymphoid formations of the esophagus is to protect the walls of this organ from foreign tissue and antigens that enter the body with food.

Lymphoid formations of the stomach are represented by B- and T-lymphocytes, macrophages and plasma cells. The lymphatic network of the stomach begins with lymphatic capillaries located in the mucous membrane of the organ. Lymphatic vessels depart from the lymphatic network and pass through the thickness of the muscle layer. Vessels from the plexuses lying between the muscular layers flow into them.

Islands of intestinal lymphatic tissue are represented by Peyer's patches - group lymph nodes, single lymph nodes, diffusely located lymphocytes and the lymphatic apparatus of the appendix.

The appendix or vermiform appendix is an appendage of the cecum and extends from its posterolateral wall. The thickness of the appendix contains a large amount of lymphoid tissue. It is believed that the lymphoid tissue of the appendix makes up 1% of all human lymphoid tissue. The cells produced here protect the body from foreign substances that enter the digestive tract along with food.

Lymphoid formations of the respiratory system are accumulations of lymphatic tissue in the mucous membrane of the larynx, trachea and bronchi, as well as lymphoid cells diffusely located in the mucosa of the respiratory apparatus, called lymphoid tissue associated with the bronchi. The lymphoid formations of the respiratory system protect the body from foreign particles that enter the respiratory organs along with the air flow.

Lymphoid formations of the urinary tract are located in the walls of the ureters and bladder. According to scientists, in infancy the number of lymph nodes in the ureters ranges from 2 to 11, and then increases to 11-14. In old age, the number of lymph nodes again decreases to 6-8. Lymph nodes in the urinary tract protect us from foreign substances that enter the body from the outside through the ascending route.

How the immune system works

The human body’s immunity and immune system is a highly precise, well-coordinated mechanism that fights bacteria and xenobiotics. All organs of the human immune system work together, complementing each other. The main task of immunity and the immune system is to recognize, destroy and remove from the body harmful infectious agents and foreign substances, as well as the resulting mutated cells and decay products.

All substances unknown to the body that penetrate it are called antigens. After the immune system detects an antigen and recognizes it, it begins to produce special cells called antibodies that bind the antigen and destroy it.

There are two types of immune defense in humans - innate and acquired immunity. Innate resistance is a very ancient defense system that all living beings have. Innate immunity is aimed at destroying the cell membrane of a foreigner that has entered the body.

If the destruction of the foreign cell does not occur, another line of defense comes into play - acquired immunity. The principle of its operation is as follows: when bacteria or a foreign substance enters the human body, leukocytes begin to produce antibodies. These antibodies are strictly specific, that is, they correspond to the substance that has entered the body like two adjacent puzzles to each other. Antibodies bind and destroy the antigen, thereby protecting our body from disease.

Allergy

In some situations, the human body's immune system reacts violently to harmless environmental factors. This condition is called allergy. Substances that provoke the manifestation of allergies are called allergens.

Allergens are divided into external and internal. External allergens are those that enter the body from the environment. This could be some types of food, mold, wool, pollen, etc. The internal allergen is our own tissue, usually with altered properties. This happens, for example, with bee stings, when the affected tissue begins to be identified as foreign.

When an allergen first enters the human body, it usually does not cause any external changes, but the processes of production and accumulation of antibodies occur. If the allergen enters the body again, an allergic reaction begins, which can occur in different ways: in the form of skin rashes, tissue swelling or an attack of suffocation.

Why don't all people suffer from allergies? There are several reasons for this. Firstly, heredity. Scientists have proven that the tendency to develop allergies is passed on from generation to generation. Moreover, if the mother has allergies, then the child will have an allergy with a probability of 20-70%, and if the father - only 12-40%.

The likelihood of an allergy in a child is especially high if both parents have this disease. In this case, the allergy will be inherited with a probability of 80%. In addition, allergic reactions are more likely to occur in people who were sick a lot in childhood.

Another factor that contributes to the development of allergies in a person is the unfavorable environmental situation in the area of residence. Scientists have proven that in areas with polluted air the number of children with allergies is significantly higher than in areas with a favorable environment. This especially applies to allergic diseases such as bronchial asthma and allergic rhinitis (hay fever).

And there is a scientific explanation for this: microscopic particles suspended in polluted air irritate the epithelial cells of the mucous membrane of the respiratory tract, thereby activating them and promoting the release of anti-inflammatory cytokines.

Thus, allergic reactions are another manifestation of the work of the immune system, the very case when, caring for our safety, the immune system, like a loving parent, shows excessive zeal.