The human body has a complex structure and includes several systems, the work of which ensures proper functioning internal organs. One of important systems- lymphatic, which includes lymphatic vessels. Thanks to the work of this system, the immune and hematopoietic function of the body is ensured, as a result of the drainage of lymph from organs and tissues.
The functioning of lymphatic vessels is in close contact with blood vessels, largely in the direction of microcirculation, where tissue fluid is formed and penetrates into the general channel. Due to this, lymphocytes are released from the general circulation, and they are absorbed from the lymph nodes into the blood.
These vessels include:
- Capillaries are the initial section in the structure of the system, performing the function of drainage. From the tissues of organs, part of the plasma is absorbed into them together with metabolic products; in case of diseases, foreign bodies and microorganisms are absorbed. It is also possible for malignant tumor cells to spread.
- Outflow vessels. The circulatory and lymphatic systems are similar in structure, but the main difference is that the lymphatic vessels include a significant number of valves and their membrane is well developed. They ensure the outflow of formed fluid from organs ( abdominal cavity, intestines and others) to the heart. Based on size, they are divided into: small, medium and large size. Large lymphatic vessels empty into veins.
- Thoracic lymphatic duct. The structure of the wall is different relative to their location. It is most strongly developed in the area of the diaphragm (the unpaired muscle that separates the chest cavity from the abdominal cavity).
- Valves. In the area of the thoracic duct there are up to nine semilunar valves. At the beginning of the valve in the wall of the duct there is an expansion created as a result of the accumulation of connective and muscle tissue.
The peculiarity of the position of the lymphatic vessels is that, when leaving the muscles and organs (lungs, abdominal cavity), they most often exit with the blood vessels. Superficial vessels are located next to the saphenous veins. Their structure has the peculiarity of branching before the joint and then reconnecting.
Lymphatic vessels of body parts and organs
Lymphatic vessels are found in almost all organs, with only a small number. Thus, the lymphatic vessels of the heart begin in the subepicardial cardiac plexus and are located in the longitudinal and coronary grooves. There are no lymphatic capillaries in the heart muscle valves and tendon threads. The lymphatic vessels of the heart are located along the movement of the coronary arteries and are included in the mediastinal nodes anteriorly and posteriorly.
The lymphatic vessels and nodes of the head and neck unite into the jugular trunks (in Latin, trunci jugulares dexter et sinister). Before lymph from the head and neck enters the venous flow, it must pass through the regional lymph nodes. The vessels of the upper part of the abdominal cavity are directed upward, and the lower part, vice versa. The abdominal cavity contains: pariental and visceral lymph nodes. The number of parietal lymph nodes in the abdominal cavity is 30-50. The visceral lymph nodes of the abdominal cavity are divided into 2 groups: along the branches of the celiac trunk and along the mesenteric artery.
Lymphatic vessels and nodes upper limb There are two types, the movement along them is directed to the lymph nodes located in the elbow and armpit area. Superficial lymphatic vessels are located near the saphenous veins. With the help of deep ones, lymph moves from tendons, muscle tissue, joints, ligamentous apparatus, nerve endings, accompany large arteries and veins of the arms.
The lymphatic vessels of the small and large intestines (in Latin, vasa lymphatica intestinalia) create a network of capillaries in the intestinal lining.
The vessels of the membrane originate in the villi from the central lacteal sinuses, which are channels formed at the top of the villi. Intestinal villi– growth of the lamina propria of the intestinal mucosa. They are located in the central part of the villi parallel to their long axis and enter the capillary system of the intestinal mucosa.
Possible diseases
When the correct functioning of any of the body systems is disrupted, the development of various pathologies. Lymphatic is no exception. If the functioning of blood vessels is disrupted, the following pathologies may occur:
- Inflammation of the lymphatic vessels (Lymphostasis). The pathology is secondary. Its development occurs as a result of purulent-inflammatory processes of the skin. The disease can occur in acute and chronic form. Characteristic symptoms are: weakness, increased fatigue, general malaise, increased body temperature. A distinctive symptom is pain in the area of the lymph nodes. The causative agent of the disease can be a pyogenic type bacterium (Escherichia coli, enterococcus, staphylococcus), benign and malignant tumors.
- Hodgkin's disease (lymphogranulomatosis). The development of the disease is typical mainly for young patients. At the beginning of development, there are no symptoms, enlarged lymph nodes do not bother the patient. Subsequently, metastases spread, the tumor spreads to other lymph nodes and organs. Symptoms such as fever, weakness, increased sweating, itching of the skin, weight loss.
- Lymphadenopathy - a condition accompanied by inflammation of the lymph nodes, refers to benign tumors. The disease has two forms: reactive and tumor. Tumor lymphadenopathy can be inflammatory or non-inflammatory. Inflammatory diseases are classified into: infectious and non-communicable diseases. They are often accompanied allergic reaction, rheumatoid arthritis. An increase (tumor) occurs as a result of toxic damage to the body or infection, a progressive inflammatory process.
- Ductal sarcoma – malignant tumor. The manifestation of pathology is possible at any age. The onset of the course is characterized by enlargement (tumor) of the lymph nodes on one side. The progression of the disease is rapid, the process of metastasis is very fast. In a short period of time, the patient’s well-being deteriorates greatly. A person suffering from lymphosarcoma develops a fever, a sharp decrease in body weight, and severe sweating at night.
Vascular diseases, like any other disease, require mandatory consultation with a doctor. After the examination, the specialist will prescribe appropriate examination and treatment. The circulatory and lymphatic systems are the object of examination of angiologists. They have more in-depth knowledge in this area of medicine.
Lymphatic vessels play an important role in the life of the human body. Violation of their functioning in any of the organs entails serious disorders. Thanks to the lymphatic vessels, many substances beneficial to the body are absorbed and subsequently released into the blood.
With cellular immunitycytotoxic T lymphocytes, or killer lymphocytes(killers) that are directly involved in the destruction of foreign cells of other organs or pathological own (for example, tumor) cells and secrete lytic substances. This reaction underlies the rejection of foreign tissues during transplantation or when the skin is exposed to chemical (sensitizing) substances that cause hypersensitivity (delayed hypersensitivity), etc.
At humoral immunity effector cells are plasma cells, which synthesize and release antibodies into the blood.
Cellular immune response is formed during transplantation of organs and tissues, infection with viruses, and malignant tumor growth.
Humoral immune response provided by macrophages (antigen-presenting cells), Tx and B lymphocytes. The antigen that enters the body is absorbed by the macrophage. The macrophage breaks it down into fragments, which, in combination with MHC class II molecules, appear on the cell surface.
Cell cooperation. T-lymphocytes implement cellular forms of the immune response, B-lymphocytes determine the humoral response. However, both forms of immunological reactions cannot take place because of the participation of auxiliary cells, which, in addition to the signal received by antigen-reactive cells from the antigen, form a second, nonspecific signal, without which the T-lymphocyte does not perceive the antigenic effect, and the B-lymphocyte is not capable of proliferation .
Intercellular cooperation is one of the mechanisms of specific regulation of the immune response in the body. It involves specific interactions between specific antigens and the corresponding structures of antibodies and cellular receptors.
Bone marrow- the central hematopoietic organ, which contains a self-sustaining population of hematopoietic stem cells and produces cells of both the myeloid and lymphoid series.
Bag of Fabritius- the central organ of immunopoiesis in birds, where the development of B-lymphocytes occurs, is located in the cloaca. Its microscopic structure is characterized by the presence of numerous folds covered with epithelium, in which lymphoid nodules are located, bounded by a membrane. The nodules contain epithelial cells and lymphocytes at various stages of differentiation.
B-lymphocytes and plasmacytes. B lymphocytes are the main cells involved in humoral immunity. In humans, they are formed from red bone marrow SCM, then enter the blood and further populate the B-zones of peripheral lymphoid organs - the spleen, lymph nodes, and lymphoid follicles of many internal organs.
B lymphocytes are characterized by the presence on the plasmalemma of surface immunoglobulin receptors (SIg or mlg) for antigens.
When exposed to an antigen, B lymphocytes in peripheral lymphoid organs are activated, proliferate, and differentiate into plasma cells that actively synthesize antibodies of various classes that enter the blood, lymph, and tissue fluid.
Differentiation. There are antigen-independent and antigen-dependent differentiation and specialization of B and T lymphocytes.
Antigen-independent proliferation and differentiation genetically programmed to form cells capable of giving a specific type of immune response when encountering a specific antigen due to the appearance of special “receptors” on the plasmalemma of lymphocytes. It takes place in central authorities immunity (thymus, bone marrow or bursa of Fabricius in birds) under the influence of specific factors produced by cells that form the microenvironment (reticular stroma or reticuloepithelial cells in the thymus).
Antigen-dependent proliferation and differentiation T- and B-lymphocytes occur when they encounter antigens in peripheral lymphoid organs, and effector cells and memory cells (retaining information about the active antigen) are formed.
№ 6 Involvement of blood cells and connective tissue in protective reactions (granulocytes, monocytes - macrophages, mast cells).
Granulocytes. Granulocytes include neutrophil, eosinophil and basophil leukocytes. They are formed in the red bone marrow and contain specific granularity in the cytoplasm and segmented nuclei.
Neutrophil granulocytes- the most numerous group of leukocytes, making up 2.0-5.5 10 9 liters of blood. Their diameter in a blood smear is 10-12 µm, and in a drop of fresh blood 7-9 µm. The population of blood neutrophils may contain cells of varying degrees of maturity - young, rod-nuclear And segmented. Granularity is visible in the cytoplasm of neutrophils.
In the surface layer cytoplasm granularity and organelles are absent. Glycogen granules, actin filaments and microtubules are located here, providing the formation of pseudopodia for cell movement.
In the inner part organelles are located in the cytoplasm (Golgi apparatus, granular endoplasmic reticulum, single mitochondria).
In neutrophils, two types of granules can be distinguished: specific and azurophilic, surrounded by a single membrane.
Main function of neutrophils- phagocytosis of microorganisms, which is why they are called microphages.
Lifespan neutrophils is 5-9 days. Eosinophilic gramulocytes. The number of eosinophils in the blood is 0.02-0.3 10 9 l. Their diameter in a blood smear is 12-14 microns, in a drop of fresh blood - 9-10 microns. The cytoplasm contains organelles - the Golgi apparatus (near the nucleus), a few mitochondria, actin filaments in the cytoplasmic cortex under the plasmalemma and granules. Among the granules there are azurophilic (primary) And eosinophilic (secondary).
Basophilic granulocytes. The number of basophils in the blood is 0-0.06 10 9 /l. Their diameter in a blood smear is 11 - 12 microns, in a drop of fresh blood - about 9 microns. All types of organelles are detected in the cytoplasm - endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria, actin filaments.
Functions. Basophils mediate inflammation and secrete eosinophilic chemotactic factor, form biologically active metabolites of arachidonic acid - leukotrienes, prostaglandins.
Lifespan. Basophils remain in the blood for about 1-2 days.
Monocytes. In a drop of fresh blood there are 9-12 microns of these cells, in a blood smear there are 18-20 microns.
In the core A monocyte contains one or more small nucleoli.
Cytoplasm monocytes is less basophilic than the cytoplasm of lymphocytes; it contains varying numbers of very small azurophilic granules (lysosomes).
Characterized by the presence of finger-shaped outgrowths of the cytoplasm and the formation of phagocytic vacuoles. The cytoplasm contains many pinocytotic vesicles. There are short tubules of the granular endoplasmic reticulum, as well as small mitochondria. Monocytes belong to the macrophage system of the body, or the so-called mononuclear phagocytic system (MPS). The cells of this system are characterized by their origin from bone marrow promonocytes, the ability to attach to the glass surface, the activity of pinocytosis and immune phagocytosis, and the presence of receptors for immunoglobulins and complement on the membrane.
Monocytes moving into tissues turn into macrophages, at the same time they have a large number of lysosomes, phagosomes, phagolysosomes.
Mast cells(tissue basophils, mast cells). These terms refer to cells in the cytoplasm of which there is a specific granularity, reminiscent of granules of basophilic leukocytes. Mast cells are regulators of local connective tissue homeostasis. They take part in reducing blood coagulation, increasing the permeability of the blood-tissue barrier, in the process of inflammation, immunogenesis, etc.
In humans, mast cells are found wherever there are layers of loose fibrous connective tissue. There are especially many tissue basophils in the wall of the gastrointestinal tract, uterus, mammary gland, thymus (thymus gland), and tonsils.
Mast cells are capable of secreting and releasing their granules. Mast cell degranulation can occur in response to any change in physiological conditions and the action of pathogens. The release of granules containing biologically active substances alters local or general homeostasis. But the release of biogenic amines from the mast cell can also occur through the secretion of soluble components through the pores cell membranes with depletion of granules (secretion of histamine). Histamine immediately causes dilation of blood capillaries and increases their permeability, which manifests itself in local edema. It also has a pronounced hypotensive effect and is an important mediator of inflammation.
№ 7 Histo-functional characteristics and features of the organization of gray and white matter in the spinal cord, cerebellar trunk and cerebral hemispheres.
Spinal cord Gray matter white matter.
Gray matter
horns. Distinguish front, or ventral, posterior, or dorsal, And lateral, or lateral, horns
White matter
Cerebellum white matter
The cerebellar cortex has three layers: outer - molecular, average - ganglionic layer, or layer piriform neurons, and internal - grainy.
Large hemispheres. The outside of the cerebral hemisphere is covered with a thin plate of gray matter - the cerebral cortex.
The cerebral cortex (cloak) is represented by gray matter located on the periphery of the cerebral hemispheres.
In addition to the bark forming the surface layers telencephalon, the gray matter in each of the cerebral hemispheres lies in the form of separate nuclei, or nodes. These nodes are located in the thickness of the white matter, closer to the base of the brain. Due to their position, accumulations of gray matter are called basal (subcortical, central) nuclei (nodes). TO basal ganglia the hemispheres include the striatum, consisting of the caudate and lenticular nuclei; fence and amygdala.
№ 8 Brain. General morpho-functional characteristics cerebral hemispheres. Embryogenesis. Neural organization of the cerebral cortex. The concept of columns and modules. Myeloarchitecture. Age-related changes in the cortex.
In the brain distinguish between gray and white matter, but the distribution of these two components is much more complex here than in the spinal cord. Most of The gray matter of the brain is located on the surface of the cerebrum and in the cerebellum, forming their cortex. A smaller part forms numerous nuclei of the brain stem.
Structure. The cerebral cortex is represented by a layer of gray matter. It is most strongly developed in the anterior central gyrus. The abundance of grooves and convolutions significantly increases the area of the gray matter of the brain. Its different sections, which differ from each other in certain features of the location and structure of cells (cytoarchitectonics), the arrangement of fibers (myeloarchitectonics) and functional significance, are called fields. They represent places of higher analysis and synthesis of nerve impulses. There are no sharply defined boundaries between them. The cortex is characterized by an arrangement of cells and fibers in layers .
Development of the cortex of large The human hemispheres (neocortex) in embryogenesis originates from the ventricular germinal zone of the telencephalon, where low-specialized proliferating cells are located. From these cells differentiate neurocytes of the neocortex. In this case, the cells lose their ability to divide and migrate into the developing cortical plate. First, neurocytes of future layers I and VI enter the cortical plate, i.e. the most superficial and deep layers of the cortex. Then neurons of layers V, IV, III and II are built into it in the direction from the inside and outside. This process is carried out due to the formation of cells in small areas of the ventricular zone during different periods of embryogenesis (heterochronous). In each of these areas, groups of neurons are formed, sequentially aligned along one or more radial glia fibers in the form of a column.
Cytoarchitecture of the cerebral cortex. Multipolar neurons of the cortex are very diverse in shape. Among them we can highlight pyramidal, stellate, fusiform, arachnid And horizontal neurons.
The neurons of the cortex are located in vaguely delimited layers. Each layer is characterized by the predominance of one type of cell. In the motor zone of the cortex there are 6 main layers: I - molecular,II- external granular,III- nuramid neurons,IV- internal granular, V- ganglionic,VI- layer of polymorphic cells.
Molecular bark layer contains a small number of small spindle-shaped association cells. Their neurites run parallel to the surface of the brain as part of the tangential plexus of nerve fibers of the molecular layer.
External granular layer formed by small neurons having a round, angular and pyramidal shape, and stellate neurocytes. The dendrites of these cells rise into the molecular layer. Neurites either extend into the white matter or, forming arcs, also enter the tangential plexus of fibers of the molecular layer.
The widest layer of the cerebral cortex is pyramidal . The main dendrite extends from the top of the pyramidal cell, which is located in molecular layer. The neurite of a pyramidal cell always extends from its base.
Internal grainy layer formed by small stellate neurons. It contains a large number of horizontal fibers.
Ganglionic layer cortex is formed by large pyramids, and the area of the precentral gyrus contains giant pyramids.
Layer of polymorphic cells formed by neurons of various shapes.
Module. The structural and functional unit of the neocortex is module. The module is organized around the cortico-cortical fiber, which is a fiber coming either from the pyramidal cells of the same hemisphere (association fiber) or from the opposite one (commissural).
The inhibitory system of the module is represented by the following types of neurons: 1) cells with an axonal brush; 2) basket neurons; 3) axoaxonal neurons; 4) cells with a double bouquet of dendrites.
Myeloarchitecture of the cortex. Among the nerve fibers of the cerebral cortex we can distinguish association fibers, connecting separate areas of the cortex of one hemisphere, commissural, connecting the cortex of different hemispheres, and projection fibers, both afferent and efferent, which connect the cortex with the nuclei of the lower parts of the central nervous system.
Age-related changes. In the 1st year life, typification of the shape of pyramidal and stellate neurons, their increase, the development of dendritic and axonal arborizations, and intra-ensemble vertical connections are observed. By 3 years in the ensembles, “nested” groups of neurons, more clearly formed vertical dendritic bundles and bundles of radial fibers are revealed. TO 5-6 years polymorphism of neurons increases; The system of horizontal intra-ensemble connections becomes more complex due to the growth in length and branching of the lateral and basal dendrites of pyramidal neurons and the development of the lateral terminals of their apical dendrites. By 9-10 years Cell groups increase, the structure of short-axon neurons becomes significantly more complex, and the network of axon collaterals of all forms of interneurons expands. By 12-14 years in ensembles, specialized forms of pyramidal neurons are clearly indicated; all types of interneurons reach high level differentiation. By the age of 18 The ensemble organization of the cortex, in terms of the main parameters of its architectonics, reaches the level of that of adults.
№ 9 Cerebellum. Structure and functional characteristics. Neuronal composition of the cerebellar cortex. Gliocytes. Interneuronal connections.
Cerebellum. It is the central organ of balance and coordination of movements. It is connected to the brain stem by afferent and efferent conductive bundles, which together form three pairs of cerebellar peduncles. There are many convolutions and grooves on the surface of the cerebellum, which significantly increase its area. The grooves and convolutions create a “tree of life” picture on the section that is characteristic of the cerebellum. The bulk of the gray matter in the cerebellum is located on the surface and forms its cortex. A smaller portion of the gray matter lies deep in white matter in the form of central nuclei. In the center of each gyrus there is a thin layer of white matter, covered with a layer of gray matter - the cortex.
In the cerebellar cortex There are three layers: outer - molecular, average - ganglionic layer, or layer piriform neurons, and internal - grainy.
Ganglion layer contains piriform neurons. They have neurites, which, leaving the cerebellar cortex, form the initial link of its efferent inhibitory pathways. 2-3 dendrites extend from the pyriform body into the molecular layer, which penetrate the entire thickness of the molecular layer. From the base of the bodies of these cells, neurites extend through the granular layer of the cerebellar cortex into the white matter and end on the cells of the cerebellar nuclei. Molecular layer contains two main types of neurons: basket and stellate. Basket neurons are located in the lower third of the molecular layer. Their thin long dendrites branch predominantly in a plane located transverse to the gyrus. The long neurites of the cells always run across the gyrus and parallel to the surface above the piriform neurons.
Stellate neurons lie above the basket-like ones and are of two types. Small stellate neurons equipped with thin short dendrites and weakly branched neurites that form synapses. Large stellate neurons have long and highly branched dendrites and neurites.
Granular layer. First type cells of this layer can be considered granular neurons, or granule cells. The cell has 3-4 short dendrites, ending in the same layer with terminal branches in the form of a bird's foot.
The neurites of the granule cells pass into the molecular layer and in it are divided into two branches, oriented parallel to the surface of the cortex along the gyri of the cerebellum.
The second type cells of the granular layer of the cerebellum are inhibitory large stellate neurons. There are two types of such cells: with short and long neurites. Neurons with short neurites lie near the ganglion layer. Their branched dendrites spread in the molecular layer and form synapses with parallel fibers - axons of granule cells. The neurites are directed into the granular layer to the glomeruli of the cerebellum and end with synapses on the terminal branching of the dendrites of the granule cells. Few stellate neurons with long neurites have dendrites and neurites abundantly branching in the granular layer, extending into the white matter.
Third type cells make up spindle-shaped horizontal cells. They have a small elongated body, from which long horizontal dendrites extend in both directions, ending in the ganglion and granular layers. The neurites of these cells give collaterals to the granular layer and go into the white matter.
Gliocytes. The cerebellar cortex contains various glial elements. The granular layer contains fibrous And protoplasmic astrocytes. The processes of fibrous astrocytes form perivascular membranes. All layers in the cerebellum contain oligodendrocytes. The granular layer and white matter of the cerebellum are especially rich in these cells. In the ganglion layer between the piriform neurons lie glial cells with dark nuclei. The processes of these cells are directed to the surface of the cortex and form the glial fibers of the molecular layer of the cerebellum.
Interneuronal connections. Afferent fibers entering the cerebellar cortex are represented by two types - mossy and the so-called climbing fibers.
Mossy fibers They are part of the olivocerebellar and pontocerebellar pathways and indirectly through granule cells have an exciting effect on the piriform cells.
Climbing fibers They enter the cerebellar cortex, apparently through the spinocerebellar and vestibulocerebellar pathways. They cross the granular layer, adjoin the piriform neurons and spread along their dendrites, ending synapses on their surface. Climbing fibers transmit excitation directly to piriform neurons.
№ 10 Spinal cord. Morpho-Functional characteristics. Development. The structure of gray and white matter. Neuronal composition. Sensory and motor pathways spinal cord, as examples of reflex blows.
Spinal cord consists of two symmetrical halves, delimited from each other in front by a deep central fissure, and behind by a connective tissue septum. The inside of the organ is darker - this is its Gray matter. On the periphery of the spinal cord there is a lighter white matter.
Gray matter The spinal cord consists of neuronal cell bodies, unmyelinated and thin myelinated fibers, and neuroglia. The main component of gray matter, distinguishing it from white matter, are multipolar neurons.
The projections of gray matter are usually called horns. Distinguish front, or ventral, posterior, or dorsal, And lateral, or lateral, horns. During the development of the spinal cord, neurons are formed from the neural tube, grouped in 10 layers, or plates. The following architecture of the indicated plates is characteristic of humans: I-V plates correspond to the posterior horns, VI-VII plates - the intermediate zone, VIII-IX plates - the anterior horns, X plate - the zone of the pericentral canal.
The gray matter of the brain consists of three types of multipolar neurons. The first type of neurons is phylogenetically more ancient and is characterized by a few long, straight and weakly branching dendrites (isdendritic type). The second type of neurons has a large number of highly branching dendrites that intertwine to form “tangles” (idiodendritic type). The third type of neurons, in terms of the degree of development of dendrites, occupies an intermediate position between the first and second types.
White matter The spinal cord is a collection of longitudinally oriented predominantly myelinated fibers. The bundles of nerve fibers that communicate between different parts of the nervous system are called spinal cord pathways.
Neurocytes. Cells similar in size, fine structure and functional significance lie in the gray matter in groups called cores. Among the neurons of the spinal cord, the following types of cells can be distinguished: radicular cells, whose neurites leave the spinal cord as part of its anterior roots, internal cells, the processes of which end in synapses within the gray matter of the spinal cord, and tuft cells, the axons of which pass through the white matter in separate bundles of fibers, carrying nerve impulses from certain nuclei of the spinal cord to its other segments or to the corresponding parts of the brain, forming pathways. Individual areas of the gray matter of the spinal cord differ significantly from each other in the composition of neurons, nerve fibers and neuroglia.
№ 11 Arteries. Morpho-functional characteristics. Classification, development, structure and function of arteries. The relationship between the structure of arteries and hemodynamic conditions. Age-related changes.
Classification. According to the structural features of arteries, there are three types: elastic, muscular and mixed (muscular-elastic).
Elastic arteries are characterized by a pronounced development of elastic structures (membranes, fibers) in their middle shell. These include large-caliber vessels such as the aorta and pulmonary artery. Large-caliber arteries perform mainly a transport function. As an example of an elastic type vessel, the structure of the aorta is considered.
Inner shell aorta includes endothelium, subendothelial layer And plexus of elastic fibers. Endothelium The human aorta consists of cells of various shapes and sizes located on the basement membrane. In endothelial cells, the endoplasmic reticulum of the granular type is poorly developed. Subendothelial layer consists of loose, fine-fibrillar connective tissue rich in stellate-shaped cells. The latter contain a large number of pinocytotic vesicles and microfilaments, as well as a granular-type endoplasmic reticulum. These cells support the endothelium. In the subendothelial layer there are smooth muscle cells(smooth myocytes).
Deeper than the subendothelial layer, the inner membrane contains a dense plexus of elastic fibers, appropriate internal elastic membrane.
The inner lining of the aorta at its origin from the heart forms three pocket-like valves (“semilunar valves”).
Middle shell the aorta consists of a large number elastic fenestrated membranes, interconnected by elastic fibers and forming a single elastic frame together with the elastic elements of other shells.
Between the membranes of the middle membrane of the artery of the elastic type lie smooth muscle cells, obliquely located in relation to the membranes.
Outer shell the aorta is built of loose fibrous connective tissue with a large number of thick elastic And collagen fibers.
To arteries of muscular type These include mainly vessels of medium and small caliber, i.e. most arteries of the body (arteries of the body, limbs and internal organs).
The walls of these arteries contain a relatively large number of smooth muscle cells, which provides additional pumping force and regulates blood flow to the organs.
Part inner shell included endothelium With basement membrane, subendothelial layer And internal elastic membrane.
Middle shell arteries contains smooth muscle cells, between which are connective tissue cells And fibers(collagen and elastic). Collagen fibers form a supporting framework for smooth myocytes. Type I, II, IV, V collagen was found in the arteries. The spiral arrangement of muscle cells ensures that during contraction, the volume of the vessel decreases and blood is pushed through. The elastic fibers of the artery wall at the border with the outer and inner membranes merge with elastic membranes.
Smooth muscle cells in the middle lining of muscular arteries maintain blood pressure through their contractions and regulate blood flow into the microvasculature of organs.
On the border between the middle and outer shells is located outer elastic membrane . It consists of elastic fibers.
Outer shell comprises loose fibrous connective tissue. In this sheath, nerves and blood vessels, feeding the wall.
Arteries of the muscular-elastic type. These include, in particular, the carotid and subclavian arteries. Inner shell these vessels consist of endothelium, located on the basement membrane, subendothelial layer And internal elastic membrane. This membrane is located on the border of the inner and middle shells.
Middle shell arteries mixed type comprises smooth muscle cells spirally oriented elastic fibers And fenestrated elastic membranes. A small amount is found between smooth muscle cells and elastic elements fibroblasts And collagen fibers.
In the outer shell arteries, two layers can be distinguished: the inner layer, containing individual bundles of smooth muscle cells, and external, consisting mainly of longitudinally and obliquely located bundles collagen And elastic fibers And connective tissue cells.
Age-related changes. The development of blood vessels under the influence of functional load ends at approximately 30 years of age. Subsequently, connective tissue grows in the walls of the arteries, which leads to their compaction. After 60-70 years in inner shell In all arteries, focal thickenings of collagen fibers are detected, as a result of which in large arteries the inner membrane approaches the average size. In small and medium-sized arteries, the inner lining grows weaker. The internal elastic membrane gradually becomes thinner and splits with age. The muscle cells of the tunica media atrophy. Elastic fibers undergo granular disintegration and fragmentation, while collagen fibers proliferate. At the same time, calcareous and lipid deposits appear in the inner and middle membranes of older people, which progress with age. In the outer shell, in persons over 60-70 years of age, longitudinally lying bundles of smooth muscle cells appear.
№ 12 Lymphatic vessels. Classification. Morpho-functional characteristics. Sources of development. The structure and functions of lymphatic capillaries and lymphatic vessels.
Lymphatic vessels- part of the lymphatic system, which also includes The lymph nodes. Functionally, lymphatic vessels are closely related to blood vessels, especially in the area where microvasculature vessels are located. It is here that tissue fluid is formed and penetrates into the lymphatic bed.
Through small lymphatic pathways, constant migration of lymphocytes from the bloodstream and their recirculation from lymph nodes into the blood.
Classification. Among the lymphatic vessels there are lymphatic capillaries, intra- And extraorgan lymphatic vessels, draining lymph from organs, and the main lymphatic trunks of the body are the thoracic duct and the right lymphatic duct, flowing into large veins of the neck. Based on their structure, lymphatic vessels are classified into non-muscular (fibrous-muscular) types.
Lymphatic capillaries. Lymphatic capillaries - primary departments the lymphatic system, into which tissue fluid enters from the tissues along with metabolic products.
Lymphatic capillaries are a system of tubes closed at one end, anastomosing with each other and penetrating organs. The wall of lymphatic capillaries consists of endothelial cells. The basement membrane and pericytes are absent in the lymphatic capillaries. The endothelial lining of the lymphatic capillary is closely connected with the surrounding connective tissue by means of slings, or fixing filaments, which are woven into collagen fibers located along the lymphatic capillaries. Lymphatic capillaries and the initial sections of efferent lymphatic vessels provide hematolymphatic balance as a necessary condition for microcirculation in a healthy body.
Efferent lymphatic vessels. The main distinctive feature of the structure of lymphatic vessels is the presence of valves and a well-developed outer membrane. At the locations of the valves, the lymphatic vessels dilate in a flask-shaped manner.
Lymphatic vessels, depending on their diameter, are divided into small, medium and large. These vessels can be non-muscular or muscular in structure.
In small vessels muscular elements are absent and their wall consists of endothelium and connective tissue membrane, except for valves.
Medium and large lymphatic vessels have three well-developed shells: internal, middle And external
In inner shell, covered with endothelium, there are longitudinally and obliquely directed bundles of collagen and elastic fibers. The duplication of the inner shell forms numerous valves. The areas located between two adjacent valves are called valve segment, or lymphangion. The lymphangion contains the muscle cuff, the wall of the valvular sinus, and the area of valve attachment.
Middle shell. In the wall of these vessels there are bundles of smooth muscle cells that have a circular and oblique direction. The elastic fibers in the tunica media can vary in number, thickness and direction.
Outer shell lymphatic vessels are formed by loose fibrous unformed connective tissue. Sometimes individual longitudinally directed smooth muscle cells are found in the outer shell.
As an example structure of a large lymphatic vessel, let's consider one of the main lymphatic trunks - thoracic lymphatic duct. The inner and middle shells are relatively weakly expressed. Cytoplasm endothelial cells rich in pinocytotic vesicles. This indicates active transendothelial fluid transport. The basal part of the cells is uneven. There is no continuous basement membrane.
IN subendothelial layer bundles of collagen fibrils lie. Somewhat deeper are single smooth muscle cells, which have a longitudinal direction in the inner shell, and an oblique and circular direction in the middle layer. At the border of the inner and middle shells there is sometimes a dense a plexus of thin elastic fibers, which is compared to the internal elastic membrane.
In the middle shell the arrangement of elastic fibers generally coincides with the circular and oblique direction of bundles of smooth muscle cells.
Outer shell The thoracic lymphatic duct contains longitudinally lying bundles of smooth muscle cells separated by layers of connective tissue.
№ 13 The cardiovascular system. General morpho-functional characteristics. Classification of vessels. Development, structure, relationship between hemodynamic conditions and the structure of blood vessels. The principle of vascular innervation. Vascular regeneration.
The cardiovascular system- a set of organs (heart, blood and lymphatic vessels) that ensures the distribution of blood and lymph throughout the body, containing nutrients and biologically active substances, gases, and metabolic products.
Blood vessels are a system of closed tubes of various diameters that perform transport functions, regulate blood supply to organs and exchange substances between blood and surrounding tissues.
The circulatory system is distinguished arteries, arterioles, hemocapillaries, venules, veins And arteriolovenular anastomoses. The relationship between arteries and veins is carried out by the vascular system microvasculature.
Arteries carry blood from the heart to the organs. As a rule, this blood is saturated with oxygen, with the exception of the pulmonary artery, which carries venous blood. Through the veins, blood flows to the heart and, unlike the blood of the pulmonary veins, contains little oxygen. Hemocapillaries connect the arterial link circulatory system with venous, except the so-called wonderful networks, in which the capillaries are located between two vessels of the same name (for example, between the arteries in the glomeruli of the kidney).
Hemodynamic conditions(blood pressure, blood flow speed), which are created in various parts of the body, determine the appearance of specific structural features of the walls of intraorgan and extraorgan vessels.
Vessels (arteries, veins, lymphatic vessels) have a similar structure plan. With the exception of capillaries and some veins, they all contain 3 membranes:
Inner shell: Endothelium is a layer of flat cells (lying on the basement membrane) that faces the vascular bed.
The subendothelial layer consists of loose connective tissue. and smooth myocytes. Special elastic structures (fibers or membranes).
Middle shell: smooth myocytes and intercellular substance (proteoglycans, glycoproteins, elastic and collagen fibers).
Outer shell: loose fibrous connective tissue, contains elastic and collagen fibers, as well as adipocytes, bundles of myocytes. Vascular vessels (vasa vasorum), lymphatic capillaries and nerve trunks.
Article navigation:
Lymphocapillary vessels constitute one of the links in the microvasculature. The lymphocapillary vessel passes into the initial, or collecting, lymphatic vessel, which then passes into the efferent lymphatic vessel.
The transition of lymphocapillary vessels into lymphatic vessels is determined by a change in the structure of the wall, and not by the appearance of valves, which are also found in capillaries. Intraorgan lymphatic vessels form wide-loop plexuses and go together with blood vessels, located in the connective tissue layers of the organ. From each organ or part of the body, drainage lymphatic vessels emerge and go to various lymph nodes.
The main lymphatic vessels, resulting from the fusion of secondary and accompanying arteries or veins, are called collectors. After passing through the last group of lymph nodes, the lymphatic collectors are connected into lymphatic trunks, corresponding in number and location to large parts of the body. Thus, the main lymphatic trunk for lower limb and the pelvis is truncus lumbalis, formed from the efferent vessels of the lymph nodes lying near the aorta and inferior vena cava, for the upper limb - truncus subclavius, running along v. subclavia, for the head and neck - truncus jugularis, running along v. jugularis interna. IN chest cavity In addition, there is a paired truncus bronchomediastinalis, and in the abdominal one there is sometimes an unpaired truncus intestinalis. All these trunks eventually connect into two terminal ducts - ductus lymphaticus dexter and ductus thoracicus, which flow into large veins, mainly into the internal jugular.
If we talk about the work of the body and in particular about the fluids that flow in the body, then not many people immediately name lymph.
However, lymph has great value for the body and has very significant functions that allow the body to function normally.
What is the lymphatic system?
Many people know about the body’s need for blood circulation and the functioning of other systems, but not many know about high value lymphatic system. If lymph does not circulate throughout the body for just a couple of hours, then such an organism can no longer function.
Thus, every human body experiences continuous need in the functioning of the lymphatic system.
It is easiest to compare the lymphatic system with the circulatory system and distinguish the following differences:
- Openness, unlike the circulatory system, the lymphatic system is open, that is, there is no circulation as such.
- Unidirectionality, if the circulatory system provides movement in two directions, then the lymph moves in the direction only from the peripheral to the central parts of the system, that is, the liquid first collects in the smallest capillaries and then moves into larger vessels, and the movement occurs only in this direction.
- There is no central pump. In order to ensure the movement of fluid in the desired direction, only a valve system is used.
- More slow motion fluids compared to the circulatory system.
- The presence of special anatomical elements– lymph nodes, which perform a significant function and are a kind of warehouse for lymphocytes.
The lymphatic vascular system is of greatest importance for metabolism and providing immunity. It is in the lymph nodes that the bulk of foreign elements that enter the body are processed.
If there is any virus in the body, then it is in the lymph nodes that work begins to study and displace this virus from the body.
You yourself can notice this activity when you have signs that indicate the body's fight against the virus. In addition, lymph regularly cleanses the body and removes unnecessary elements from the body.
Learn more about the lymphatic system from the video:
Functions
If we talk in more detail about the functions, we should note the connection between the lymphatic system and the cardiovascular system. It is thanks to lymph that the delivery of various items, which cannot immediately end up in the cardiovascular system:
- proteins;
- fluid from tissue and intertissue space;
- fats that come mainly from the small intestine.
These elements are transported to the venous bed and thus end up in the circulatory system. These components can then be removed from the body.
At the same time, many inclusions unnecessary for the body are processed at the lymph stage, in particular we are talking about viruses and infections that are neutralized by lymphocytes and destroyed in the lymph nodes.
It should be noted special function lymphatic capillaries, which are larger in size compared to the capillaries of the circulatory system and have thinner walls. Thanks to this, from the interstitial space into the lymph proteins and other components may be supplied.
Additionally, the lymphatic system can be used to cleanse the body, since the intensity of lymph flow largely depends on the compression of blood vessels and muscle tension.
Thus, massage and physical activity allow you to make the movement of lymph more efficient. Thanks to this, additional cleansing and healing of the body becomes possible.
Peculiarities
Actually, the word “lymph” comes from the Latin “lympha”, which translates as moisture or pure water. Just from this name it is possible to understand a lot about the structure of lymph, which washes and cleanses the entire body.
Many could observe lymph, since this liquid secreted on the surface when there are wounds on the skin. Unlike blood, the liquid is almost completely transparent.
By anatomical structure lymph refers to connective tissue and contains a large number of lymphocytes in the complete absence of red blood cells and platelets.
In addition, lymph, as a rule, contains various waste products of the body. In particular, the previously noted large protein molecules that cannot be absorbed into the venous vessels.
Such molecules are often may be viruses Therefore, the lymphatic system is used to absorb such proteins.
Lymph may contain various hormones, which are produced by endocrine glands. Fats and some other nutrients come here from the intestines, and protein from the liver.
Direction of lymph movement
The figure below shows a diagram of the movement of lymph in the human lymphatic system. It does not display every lymphatic vessel and the entire lymph nodes, which about five hundred in the human body.
Pay attention to the direction of movement. Lymph moves from the periphery to the center and from bottom to top. Liquid leaks from small capillaries, which are further connected into larger vessels.
The movement occurs through the lymph nodes, which contain a huge number of lymphocytes and cleanse the lymph.
Typically to the lymph nodes comes more vessels than departs, that is, lymph enters through many channels and leaves through one or two. Thus, the movement continues to the so-called lymphatic trunks, which are the largest lymphatic vessels.
The largest is thoracic duct
, which is located near the aorta and passes through itself lymph from:
- all organs that are located below the ribs;
- the left side of the chest and the left side of the head;
- left hand.
This duct connects to left subclavian vein, which you can see marked in blue in the picture on the left side. This is where lymph flows from the thoracic duct.
It should also be noted right duct, which collects fluid from the right upper side of the body, in particular from the chest and head, arms.
From here the lymph enters right subclavian vein, which is located symmetrically to the left in the figure. Additionally, it should be noted such large vessels that belong to the lymphatic system as:
- right and left jugular trunks;
- left and right subclavian trunks.
It should be said about the frequent location of lymphatic vessels along blood vessels, in particular venous vessels. If you pay attention to the picture, you will see some similar arrangement of vessels of the circulatory and lymphatic systems.
Lymphatic system It has great importance for the human body.
Many doctors consider a lymph analysis to be no less relevant than a blood test, since lymph can indicate some factors that are not detected in other tests.
In general, lymph, in combination with blood and intercellular fluid, constitutes the internal fluid environment in the human body.
If there is a system in the body, then there is something that fills it. The activity of the branches of the structure depends on the quality of the content. This situation can be fully attributed to the work of the human circulatory and lymphatic systems. The healthy contents of these structures are integral factor stable functioning of the whole organism. Next, we will look in more detail at the importance of blood and lymphatic vessels. Let's start with the last ones.
General information
Human lymphatic vessels are represented by different structures that perform certain functions. So, they distinguish:
- Capillaries.
- Large trunks (thoracic and right ducts).
- Extra- and intraorgan vessels.
Also, structures are of muscular and non-muscular types. The flow rate and pressure (hemodynamic conditions) are close to those that occur in the venous bed. If we talk about the structure of the lymphatic vessels, then it is necessary to note the well-developed outer membrane. Due to the internal coating, valves are formed.
Capillary
This lymphatic vessel has a fairly permeable wall. The capillary is capable of absorbing suspensions and colloidal solutions. The channels form networks that represent the beginning of the lymphatic system. By connecting, the capillaries form larger channels. Each lymphatic vessel formed passes to the subclavian veins through the neck and sternum.
Moving content along channels
The movement of lymph through the lymphatic vessels is carried out along the cervical duct into the venous bed. By thoracic region there is an outflow from virtually the entire (except the head) body. Both ducts enter the subclavian veins. In other words, all the fluid that enters the tissues returns to the blood. In this regard, as the lymph moves through the lymphatic vessels, drainage occurs. When there are outflow disturbances, pathological condition. It is called lymphostasis. Its most characteristic symptoms include swelling in the extremities.
System functions
Lymphatic vessels and nodes primarily ensure the maintenance of constancy in the internal environment. In addition, the system performs the following functions:
- Transports from the intestines nutrients into the veins.
- Provides communication between blood, organs and tissues.
- Takes part in immunological processes.
- Provides return of electrolytes, water, protein into the blood from the intercellular space.
- Neutralizes harmful compounds.
Along the lymphatic vessels there are nodes. Liquid is deposited in them. Lymph nodes provide fluid production and barrier-filtration protection (by producing macrophages). The outflow is regulated by the sympathetic nervous system.
Interaction of structures
Located in close proximity to the blood vessels, the lymphatic capillaries begin blindly. They are part of the structure of the microvasculature. This determines the close functional and anatomical connection between the blood and lymphatic vessels. The necessary elements enter the ground substance from the hemocapillaries. From it, in turn, they penetrate into the lymphocapillaries various substances. These are, in particular, products metabolic processes, breakdown of compounds against the background of pathological disorders, cancer cells. Enriched and purified lymph penetrates the bloodstream. This is how the internal environment in the body and the intercellular (basic) substance are renewed.
Structure differences
Small blood and lymphatic vessels have different diameters (the latter are larger). The endothelial cells of the former are 3-4 times larger than those of the latter. Lymph capillaries do not have a basement membrane and pericytes and end blindly. These structures form a network and flow into small extraorgan or intraorgan channels.
Postcapillaries
Intraorgan outflow channels are muscleless (fibrous) structures. Each such lymphatic vessel has a diameter of about 40 microns. Endotheliocytes in the channels lie on a weakly defined membrane. Underneath it are elastic and collagen fibers that pass into the outer shell. Postcapillary channels perform the function of drainage.
Extraorgan beds
These vessels are distinguished by a larger caliber than the previous ones and are considered superficial. They belong to muscle-type structures. If the superficial lymphatic vessel (Latin - vasa lymphatica superficialia) is located in the upper zone of the torso, neck, face, then there are quite a few myocytes in it. If the channel runs along the lower body and legs, then there are more muscle elements.
Medium-caliber structures
These are muscular type channels. The structure of the lymphatic vessels of this group has some features. In their walls, all three shells are quite clearly expressed: outer, middle and inner. The latter is represented by endothelium lying on a weakly defined membrane, subendothelium (it contains multidirectional elastic and collagen fibers), as well as plexuses of elastic fibers.
Valves and shells
These elements interact quite closely with each other. The valves are formed due to the inner shell. The fibrous plate serves as the basis. In its center there are smooth muscle elements. The plate is covered by endothelium. The middle shell of the ducts is formed by bundles of smooth muscle elements. They are directed obliquely and circularly. The shell is also represented by layers of connective (loose) tissue. These same fibers form the outer structure. Its elements merge into the surrounding tissue.
Thoracic duct
This lymphatic vessel has a wall whose composition is similar to the structure of a hollow inferior vein. The inner lining is represented by endothelium, subendothelium and a plexus of elastic internal fibers. The first lies on a discontinuous, weakly defined basement membrane. The subendothelium contains poorly differentiated cells, elastic and collagen fibers that are oriented in different directions, as well as smooth muscle elements. The inner shell forms 9 valves that promote the movement of lymph to the veins of the neck. The middle shell is represented by smooth muscle elements. They have an oblique and circular direction. Also in the shell there are multidirectional elastic and collagen fibers. The outer structure at the diaphragmatic level is four times thicker than the inner and middle structures combined. The membrane is represented by loose connective tissue and bundles of smooth myocytes located longitudinally. The superficial lymphatic vessel enters the jugular vein. Near the mouth, the wall of the duct is 2 times thinner than at the diaphragmatic level.
Other items
There is a special area between two valves located next to each other in a lymphatic vessel. It's called lymphangion. It is represented by a muscular cuff, the wall of the valvular sinus and the attachment site of the valve itself. The right and thoracic ducts are represented as large trunks. In these elements of the lymphatic system, myocytes (muscle elements) are present in all membranes (there are three of them).
Nutrition of the duct walls
The outer lining of the blood and lymphatic channels contains vascular vessels. These arterial small branches diverge along the integument: the middle and outer ones in the arteries and all three in the veins. From the arterial walls, capillary blood converges into veins and venules. They are located next to the arteries. From the capillaries in the inner lining of the veins, blood moves into the venous lumen. The nutrition of large lymphatic ducts has a peculiarity. It lies in the fact that the arterial branches are not accompanied by venous branches, which run separately. Vascular vessels are not found in venules and arterioles.
Inflammation of the lymphatic vessels
This pathology is considered secondary. It is a complication of purulent-inflammatory processes skin(furuncle, carbuncle, any purulent wound) and infections of a specific type (tuberculosis, syphilis and others). The course of the process can be acute or chronic. Nonspecific and specific inflammation of lymphatic vessels are also distinguished. The disease is characterized by malaise and weakness. Patients also develop a fever. A characteristic feature pathology is pain in the lymph nodes. The causative agent of the pathology can be any pyogenic type bacteria (Escherichia coli, enterococcus, staphylococcus). The disease is diagnosed without much difficulty. Therapeutic measures are prescribed in accordance with the stage of the pathology. As conservative method sulfonamides and antibiotics are used. In advanced cases, the superficial lymphatic vessel is drained through the opening of the abscess.
Tumor
Hodgkin's disease - lymphogranulomatosis - affects mainly young people (15-10 years). Symptoms of pathology on initial stages are absent, and the patient is not bothered by enlarged lymph nodes. As the disease progresses, metastasis occurs. The tumor spreads to other lymph nodes and organs, among which the spleen is usually the first to be affected. After this, signs of pathology begin to appear. In particular, the patient experiences fever, general weakness, sweating, itchy skin, and weight loss. The disease is diagnosed by studying the leukocyte formula, as well as biopsy material.
Lymphadenopathy
It is quite simple to distinguish this pathology from others. In some cases, however, difficulties may arise with enlarged cervical elements. Lymphodenopathy is divided into reactive and tumor - non-inflammatory and inflammatory. The latter are classified into infectious and non-infectious diseases of the lymphatic vessels. They accompany diffuse pathologies in connective tissue, allergies, and rheumatoid arthritis. Reactive enlargement in the lymph nodes indicates cell proliferation due to an immune response to autoimmune, allergic, toxic attacks or an infectious process of an inflammatory nature. Against the background of a tumor, an increase in structural elements is caused by infiltration of malignant cells coming from other organs (with lymphocytic leukemia or cancer metastasis) or arising in the system itself against the background of malignant lymphomas and lymphosarcoma. Pathologies can be generalized or limited. The latter, however, can transform into the former. At first, lymphogranulomatosis is classified as limited lymphadenopathy, and then, after a while, it becomes generalized. The reactive group includes enough wide range pathologies that are a diagnostic sign.
Ductal sarcoma
This is another malignant tumor. Lymphosarcoma can appear at absolutely any age. As a rule, it begins with enlargement of the lymph nodes on one side. characterized by a fairly high rate of progression, active metastasis and particular malignancy. Within a short time, the patient's condition may deteriorate significantly. The patient develops a fever, rapidly decreases body weight, and increases sweating at night. Diagnosis consists of histology and the affected lymph node.
