What is a lymphatic capillary definition. The purpose of lymphatic capillaries in the human body
Lymphatic vessels are divided into:
1) lymphatic capillaries;
2) efferent intraorgan and extraorgan lymphatic vessels;
3) large lymphatic trunks (thoracic lymphatic duct and right lymphatic duct).
In addition, lymphatic vessels are divided into:
1) vessels of the non-muscular (fibrous) type and 2) vessels of the muscular type. Hemodynamic conditions (lymph flow speed and pressure) are close to the conditions in the venous bed. In the lymphatic vessels, the outer shell is well developed, and valves are formed due to the inner shell.
Lymphatic capillaries they begin blindly, are located next to the blood capillaries and are part of the microvasculature, therefore there is a close anatomical and functional connection between the lymphocapillaries and hemocapillaries. From the hemocapillaries, the necessary components of the main substance enter the main intercellular substance, and from the main substance, metabolic products, components of the breakdown of substances during pathological processes, and cancer cells enter the lymphatic capillaries.
Differences between lymphatic capillaries and blood capillaries:
1) have a larger diameter;
2) their endothelial cells are 3-4 times larger;
3) do not have a basement membrane and pericytes, lie on the outgrowths of collagen fibers;
4) end blindly.
Lymphatic capillaries form a network and flow into small intraorgan or extraorgan lymphatic vessels.
Functions of lymphatic capillaries:
1) from the interstitial fluid, its components enter the lymphocapillaries, which, once in the lumen of the capillary, collectively constitute lymph;
2) metabolic products are drained;
3) cancer cells emerge, which are then transported into the blood and spread throughout the body.
Intraorgan efferent lymphatic vessels are fibrous (muscleless), their diameter is about 40 microns. The endothelial cells of these vessels lie on a weakly defined membrane, under which are located collagen and elastic fibers that pass into the outer membrane. These vessels are also called lymphatic postcapillaries; they have valves. Postcapillaries perform a drainage function.
Extraorgan efferent lymphatic vessels larger ones belong to the muscular type vessels. If these vessels are located in the face, neck and upper part of the body, then the muscle elements in their wall are contained in small quantities; if there are more myocytes in the lower body and lower extremities.
Medium-sized lymphatic vessels also refer to muscular type vessels. In their wall, all 3 shells are better expressed: inner, middle and outer. The inner lining consists of endothelium lying on a poorly defined membrane; subendothelium, which contains multidirectional collagen and elastic fibers; plexus of elastic fibers.
Valves of lymphatic vessels formed by the inner shell. The basis of the valves is a fibrous plate, in the center of which there are smooth myocytes. This plate is covered with endothelium.
Median tunica of medium-sized vessels It is represented by bundles of smooth myocytes, directed circularly and obliquely, and layers of loose connective tissue.
Outer lining of medium-sized vessels It is represented by loose connective tissue, the fibers of which pass into the surrounding tissue.
Lymphangion- this is the area located between two adjacent valves of the lymphatic vessel. It includes the muscular cuff, the wall of the valvular sinus, and the insertion of the valve.
Large lymphatic trunks represented by the right lymphatic duct and the thoracic duct. In large lymphatic vessels, myocytes are located in all three membranes.
Thoracic lymphatic duct has a wall whose structure is similar to that of the inferior vena cava. The inner membrane consists of endothelium, subendothelium and a plexus of elastic fibers. The endothelium lies on a poorly defined discontinuous basement membrane; the subendothelium contains poorly differentiated cells, smooth myocytes, collagen and elastic fibers oriented in different directions.
Due to the inner shell, 9 valves are formed, which promote the movement of lymph towards the veins of the neck.
The middle shell is represented by smooth myocytes with circular and oblique directions, multidirectional collagen and elastic fibers.
The outer shell at the level of the diaphragm is 4 times thicker than the inner and middle shells combined; consists of loose connective tissue and longitudinally arranged bundles of smooth myocytes. The duct joins a vein in the neck. The wall of the lymphatic duct near the mouth is 2 times thinner than at the level of the diaphragm.
Functions of the lymphatic system:
1) drainage - metabolic products, harmful substances, and bacteria enter the lymphatic capillaries;
2) filtration of lymph, i.e. cleansing of bacteria, toxins and other harmful substances in the lymph nodes where lymph flows;
3) enrichment of lymph with lymphocytes at the moment when lymph flows through the lymph nodes.
Purified and enriched lymph enters the bloodstream, i.e. the lymphatic system performs the function of updating the main intercellular substance and the internal environment of the body.
Blood supply to the walls of blood and lymphatic vessels. In the adventitia of the blood and lymphatic vessels there are vascular vessels (vasa vasorum) - these are small arterial branches that branch in the outer and middle membranes of the arterial wall and all three membranes of the veins. From the walls of the arteries, the blood of the capillaries collects into venules and veins, which are located next to the arteries. From the capillaries of the inner lining of the veins, blood enters the lumen of the vein.
The blood supply of large lymphatic trunks differs in that the arterial branches of the walls are not accompanied by venous ones, which run separately from the corresponding arterial ones. Arterioles and venules lack vasculature.
Reparative regeneration of blood vessels. If the wall of blood vessels is damaged, after 24 hours rapidly dividing endothelial cells close the defect. Regeneration of smooth myocytes of the vascular wall proceeds slowly, since they divide less frequently. The formation of smooth myocytes occurs due to their division, differentiation of myofibroblasts and pericytes into smooth muscle cells.
If large and medium-sized blood vessels are completely ruptured, their restoration without surgical intervention by a surgeon is impossible. However, the blood supply to the tissues distal to the rupture is partially restored due to collaterals and the appearance of small blood vessels. In particular, protrusion of dividing endothelial cells (endothelial buds) occurs from the walls of arterioles and venules. Then these protrusions (buds) move closer to each other and connect. After this, the thin membrane between the kidneys ruptures and a new capillary is formed.
Regulation of blood vessel function.Nervous regulation carried out by efferent (sympathetic and parasympathetic) and sensory nerve fibers, which are the dendrites of sensory neurons of the spinal ganglia and sensory ganglia of the head.
Efferent and sensory nerve fibers densely entwine and accompany blood vessels, forming nerve plexuses, which include individual neurons and intramural ganglia.
Sensitive fibers end in receptors that have a complex structure, i.e. they are polyvalent. This means that the same receptor simultaneously contacts the arteriole, venule and anastomosis or the vessel wall and connective tissue elements. The adventitia of large vessels can contain a wide variety of receptors (encapsulated and non-encapsulated), which often form entire receptor fields.
Efferent nerve fibers end in effectors (motor nerve endings).
Sympathetic nerve fibers are axons of efferent neurons of the sympathetic ganglia; they end in adrenergic nerve endings.
Parasympathetic nerve fibers are axons of efferent neurons (type I Dogel cells) of the intramural ganglia, they are cholinergic nerve fibers and end in cholinergic motor nerve endings.
When sympathetic fibers are excited, the vessels constrict, while parasympathetic fibers dilate.
Neuroparsis regulation characterized by the fact that nerve impulses enter single endocrine cells along nerve fibers. These cells secrete biologically active substances that affect blood vessels.
Endothelial or intimal regulation characterized by the fact that endothelial cells secrete factors that regulate the contractility of myocytes of the vascular wall. In addition, endothelial cells produce substances that prevent blood clotting and substances that promote blood clotting.
Age-related changes in arteries. Arteries finally develop by the age of 30. After this, their stable condition is observed for ten years.
At the age of 40, their reverse development begins. In the wall of arteries, especially large ones, elastic fibers and smooth myocytes are destroyed, and collagen fibers grow. As a result of the focal proliferation of collagen fibers in the subendothelium of large vessels, the accumulation of cholesterol and sulfated glycosaminoglycans, the subendothelium sharply thickens, the vessel wall thickens, salts are deposited in it, sclerosis develops, and the blood supply to organs is disrupted. In persons over 60-70 years of age, longitudinal bundles of smooth myocytes appear in the outer membrane.
Age-related changes in veins similar to changes in arteries. However, earlier changes take place in the veins. In the subendothelium of the femoral vein of newborns and infants, there are no longitudinal bundles of smooth myocytes; they appear only when the child begins to walk. In young children, the diameter of the veins is the same as the diameter of the arteries. In adults, the diameter of the veins is 2 times the diameter of the arteries. This is due to the fact that blood in the veins flows slower than in the arteries, and in order for the slow blood flow to maintain a balance of blood in the heart, i.e., as much arterial blood leaves the heart as venous blood enters, the veins must be wider.
The wall of veins is thinner than the wall of arteries. This is explained by the peculiarity of hemodynamics in the veins, i.e. low intravenous pressure and slow blood flow.
Heart
Development. The heart begins to develop on the 17th day from two rudiments: 1) mesenchyme and 2) myoepicardial plates of the visceral layer of the splanchnotome at the cranial end of the embryo.
Tubes are formed from the mesenchyme on the right and left, which are invaginated into the visceral layers of the splanchnotomes. That part of the visceral layers that is adjacent to the mesenchymal tubules turns into the myoepicardial plate. Subsequently, with the participation of the trunk fold, the right and left rudiments of the heart come together and then the connection of these rudiments in front of the foregut occurs. The endocardium of the heart is formed from the fused mesenchymal tubes. The cells of the myoepicardial plates differentiate in 2 directions: the mesothelium lining the epicardium is formed from the outer part, and the cells of the inner part differentiate in three directions. From them are formed: 1) contractile cardiomyocytes; 2) conducting cardiomyocytes; 3) endocrine cardiomyocytes.
During the differentiation of contractile cardiomyocytes, the cells acquire a cylindrical shape and are connected at their ends by desmosomes, where intercalated discs (discus intercalates) are subsequently formed. In the developing cardiomyocytes, myofibrils appear, arranged longitudinally, tubules of smooth ER, due to invagination of the sarcolemma, T-channels are formed, and mitochondria are formed.
The conduction system of the heart begins to develop in the 2nd month of embryogenesis and ends in the 4th month.
Heart valves develop from the endocardium. The left atrioventricular valve is formed in the 2nd month of embryogenesis in the form of a fold, which is called endocardial cushion. Connective tissue from the epicardium grows into the cushion, from which the connective tissue base of the valve leaflets is formed, which is attached to the fibrous ring.
The right valve is laid in the form of a myoendocardial cushion, which includes smooth muscle tissue. The connective tissue of the myocardium and epicardium grows into the valve leaflets, while the number of smooth myocytes decreases, they remain only at the base of the valve leaflets.
At the 7th week of embryogenesis, intramural ganglia are formed, including multipolar neurons, between which synapses are established.
1.Blind start.
2. Wall composition:
a) Unlike hemocapillaries, lymphocapillaries do not have pericytes and a basement membrane.
b) That is the wall is formed only by endothelial cells.
3. Diameter – the diameter of lymphatic capillaries is several times wider than that of blood capillaries.
4. Sling filaments:
a) Instead of the basement membrane, the supporting function is performed by sling (anchor, fixing) filaments.
b) They attach to the endothelial cell (usually in the area of contact of the endothelial cell) and are woven into collagen fibers located parallel to the capillary.
c) These elements also contribute to the drainage of the capillary.
Lymphatic postcapillaries– intermediate link between lymphatic capillaries and vessels:
The transition of the lymphatic capillary to the lymphatic postcapillary is determined by first valve in the lumen (valves lymphatic vessels are paired folds of the endothelium and the underlying basement membrane lying opposite each other);
Lymphatic postcapillaries have all the functions of capillaries, but lymph flows through them only in one direction.
Lymphatic vessels are formed from networks of lymphatic postcapillaries (capillaries):
· the transition of a lymphatic capillary into a lymphatic vessel is determined by a change in the structure of the wall: along with the endothelium, it contains smooth muscle cells and adventitia, and valves in the lumen;
· Lymph can flow through vessels only in one direction;
· the area of the lymphatic vessel between the valves is currently designated by the term "lymphangion".
Classification of lymphatic vessels.
I. Depending on the location (above or below the superficial fascia):
1. superficial – lie in the subcutaneous fatty tissue above the superficial fascia;
2. deep.
II. In relation to organs:
1. intraorgan - form broadly looped plexuses. The lymphatic vessels emerging from these plexuses accompany the arteries, veins and exit the organ.
2. extraorganic - sent to nearby groups of regional lymph nodes, usually accompanying blood vessels, often veins.
Along the path of the lymphatic vessels there are lymph nodes. This is what causes foreign particles, tumor cells, etc. are retained in one of the regional lymph nodes. The exceptions are some lymphatic vessels of the esophagus and, in isolated cases, some vessels of the liver, which flow into the thoracic duct, bypassing the lymph nodes.
Regional lymph nodes organs or tissues are lymph nodes that are the first on the path of lymphatic vessels carrying lymph from a given area of the body.
Lymphatic trunks- These are large lymphatic vessels that are no longer interrupted by lymph nodes. They collect lymph from several areas of the body or several organs.
There are four permanent paired lymphatic trunks in the human body:
I. Jugular trunk(right and left) – represented by one or several vessels of small length. It is formed from the efferent lymphatic vessels of the lower lateral deep cervical lymph nodes, located in a chain along the internal jugular vein. Each of them drains lymph from organs and tissues of the corresponding sides of the head and neck.
II. Subclavian trunk(right and left) - formed from the fusion of the efferent lymphatic vessels of the axillary lymph nodes, mainly the apical ones. He collects lymph from the upper limb, from the walls of the chest and mammary gland.
III. Bronchomediastinal trunk(right and left) - formed mainly from the efferent lymphatic vessels of the anterior mediastinal and superior tracheobronchial lymph nodes. He carries lymph from the walls and organs of the chest cavity.
IV. Lumbar trunks(right and left) – formed by the efferent lymphatic vessels of the upper lumbar lymph nodes – drain lymph from the lower limb, walls and organs of the pelvis and abdomen.
V. Fickle intestinal lymphatic trunk– occurs in approximately 25% of cases. It is formed from the efferent lymphatic vessels of the mesenteric lymph nodes and 1-3 vessels flow into the initial (abdominal) part of the thoracic duct.
Lymphatic trunks empty into two ducts:
thoracic duct and
right lymphatic duct,
which flow into the veins of the neck in the area of the so-called venous angle, formed by the connection of the subclavian and internal jugular veins.
It drains into the left venous angle thoracic lymphatic duct , through which lymph flows from 3/4 of the human body:
from the lower extremities,
· belly,
left half of the chest, neck and head,
left upper limb.
It drains into the right venous angle right lymphatic duct , which brings lymph from 1/4 of the body:
from the right half of the chest, neck, head,
· from the right upper limb.
Rice. Diagram of lymphatic trunks and ducts.
1 - lumbar trunk;
2- intestinal trunk;
3 - bronchomediastinal trunk;
4 - subclavian trunk;
5 - jugular trunk;
6 - right lymphatic duct;
7 - thoracic duct;
8 - arc of the thoracic duct;
9 - cervical part of the thoracic duct;
10-11 thoracic and abdominal parts
thoracic duct;
12 - thoracic duct cistern.
Thoracic duct(ductus thoracicus).
· Length – 30 – 45 cm,
· formed at the level of the XI thoracic – 1st lumbar vertebrae merger right and left lumbar trunks.
· Sometimes the thoracic duct is widened at the beginning.
· forms in the abdominal cavity and passes into the chest cavity through the aortic opening of the diaphragm, where it is located between the aorta and the right medial leg of the diaphragm, the contractions of which help push lymph into the thoracic part of the duct.
· At the level of the VII cervical vertebra The thoracic duct forms an arc and, going around the left subclavian artery, flows into the left venous angle or the veins that form it.
At the mouth of the duct there is semilunar valve, preventing blood from entering the vein from the vein.
· The upper part of the thoracic duct flows into:
· left bronchomediastinal trunk, collecting lymph from the left half of the chest,
left subclavian trunk, collecting lymph from the left upper limb,
· the left jugular trunk, which carries lymph from the left half of the head and neck.
Right lymphatic duct(ductus lymphaticus dexter).
· Length – 1 – 1.5 cm,
· is being formed upon merger right subclavian trunk, carrying lymph from the right upper limb, right jugular trunk, collecting lymph from the right half of the head and neck, right bronchomediastinal trunk, bringing lymph from the right half of the chest.
However, more often, the right lymphatic duct absent and the trunks that form it flow into the right venous angle independently.
Lymphatic capillaries
vasa lymphocapillaria , are the initial lymphatic system. When connected to each other, they form closed circuits in organs and tissues. lymphocapillary networks,rete lymphocapillare.
The orientation of the capillaries is determined by the direction of the connective tissue bundles in which the lymphatic capillaries lie, and the position of the structural elements of the organ. Thus, in large organs (muscles, lungs, liver, kidneys, large glands, etc.) lymphocapillary networks have a three-dimensional structure. The lymphatic capillaries in them are oriented in different directions, lying between bundles of muscle fibers, groups of glandular cells, renal corpuscles and tubules, and hepatic lobules. In flat organs (fascia, serous membranes, skin, layers of the walls of hollow organs, walls of large blood vessels), lymphocapillary networks are located in one plane, parallel to the surface of the organ. In some organs, a network of lymphatic capillaries forms protrusions.
Lymphatic vessels
, vasa lymphatica , formed by the fusion of lymphatic capillaries. Intraorgan and often extraorgan lymphatic vessels outside the endothelium have only a thin connective tissue membrane (muscleless vessels). The walls of larger lymphatic vessels consist of an inner lining covered with endothelium, tunica interna, medium - muscular, tunica media, and outer - connective tissue membrane, tunica externa, s. adventitia.
Lymphatic vessels have valves valvulae lymphaticae. Each valve consists of two folds of the inner membrane (leaflets), located opposite each other. The intraorgan lymphatic vessels located nearby form networks (plexuses), the loops of which have different shapes and sizes.
Lymphatic vessels emerge from internal organs and muscles next to blood vessels - this is deep lymphatic vessels,vasa lymphdtica profunda. Superficial lymphatic vessels,vasa lymphdtica superficialia, located next to or near the saphenous veins.
Lymph flow into the venous bed
Through the efferent lymphatic vessels, lymph from one nodes is directed to the next lymph nodes or collector vessels lying in the path of its flow - lymphatic trunks and ducts. In each regional group, the lymph nodes are connected to each other using lymphatic vessels. Through these vessels, lymph flows from one node to another in the direction of its general flow, towards the venous angle formed by the confluence of the internal jugular and subclavian veins. On its way from each organ, lymph passes through at least one lymph node, and more often through several.
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Ticket number 1.
Lymphatic capillaries. Structural features and functions.
Extraorgan lymphatic vessels are also similar in structure to veins, but the basal endothelial membrane is poorly defined and absent in places. The internal elastic membrane is clearly visible in the wall of these vessels. The middle shell receives special development in the lower extremities.
The diameter of the lymphocapillaries is 20-30 microns. They perform a drainage function: they absorb tissue fluid from the connective tissue.
To prevent the capillary from collapsing, there are sling or anchor filaments, which are attached to endothelial cells at one end and woven into loose fibrous connective tissue at the other.
Lamellar bone tissue. Morpho-functional features. Localization in the body.
Lamellar bone tissue forms compact and spongy bone. Bone as an organ. The compact substance that forms the diaphyses of tubular bones consists of bone plates that are arranged in a certain order, forming complex systems. The diaphysis of the tubular bone consists of three layers - a layer of external general plates, a layer of Haversian systems (osteons), and a layer of internal general plates. The outer general plates are located under the periosteum, the inner ones - on the side of the bone marrow. These plates cover the entire bone, forming concentric layers. Channels containing blood vessels pass through the general plates into the bone. Each plate consists of a base substance in which bundles of ossein (collagen) fibers run in parallel rows. Osteocytes lie between the plates. In the middle layer, the bony plates are arranged concentrically around a canal where blood vessels pass, forming an osteon (Haversian system). Osteon is a system of cylinders inserted one into the other. This design gives the bone extreme strength. In two adjacent plates, bundles of ossein fibers run in different directions. Between the osteons there are intercalary (intermediate) plates. These are parts of former osteons. The tubular substance forms flat bones and the epiphyses of tubular bones. Its plates form chambers (cells) containing red bone marrow. The periosteum (periosteum) has two layers: outer (fibrous) and inner (cellular), containing osteoblasts and osteoclasts. The vessels and nerves that supply the bone pass through the periosteum; they take part in trophism, development, growth and bone regeneration.
Regeneration and age-related changes. Processes of destruction and creation occur in bone tissue throughout a person’s life. They continue after bone growth has finished. The reason for this is a change in the physical load on the bone.
3. Organelles for special purposes (microvilli, cilia, tonofibrils, myofibrils), their structure and functions.
Organelles for special purposes are microstructures that are constantly present and obligatory for individual cells, performing special functions that ensure the specialization of tissues and organs. These include:
– eyelashes,
– flagella,
– microvilli,
– myofibrils.
Cilia– organelles, which are thin (constant diameter 300 nm) hair-like structures on the surface of cells, outgrowths of the cytoplasm. Their length can range from 3–15 µm to 2 mm. They can be mobile or not: immobile cilia play the role of receptors and participate in the process of movement.
The cilium is based on an axoneme (axial filament) extending from the basal body.
The axoneme is formed by microtubules according to the scheme: (9 x 2) + 2. This means that nine doublets of microtubules are located along its circumference, and another pair of microtubules runs along the axis of the axoneme and is enclosed in a central case.
Microvillus- a cell outgrowth that has a finger-like shape and contains a cytoskeleton of actin microfilaments inside. In the human body, microvilli have epithelial cells of the small intestine, on the apical surface of which the microvilli form a brush border.
Microvilli do not contain microtubules and are only capable of slow bending (in the intestine) or are immobile.
The framework of each microvillus is formed by a bundle containing about 40 microfilaments lying along its long axis. Auxiliary proteins that interact with actin—fimbrin, spectrin, villin, etc.—are responsible for the ordering of the actin cytoskeleton of microvilli. Microvilli also contain several types of cytoplasmic myosin.
Microvilli increase the absorption surface area many times over. In addition, in vertebrates, digestive enzymes are attached to their plasmalemma, providing parietal digestion.
Myofibrils- organelles of striated muscle cells that ensure their contraction. They serve to contract muscle fibers and consist of sarcomeres.
Ticket number 2.
1. Shells of the brain and spinal cord. Structure and functional significance.
The brain is protected by the bones of the skull, and the spinal cord by the vertebrae and intervertebral discs; they are surrounded by three meninges (from outside to inside): hard, arachnoid and soft, which fix these organs in the skull and spinal canal and perform protective, shock-absorbing functions, ensure the production and absorption of cerebrospinal fluid.
The dura mater is formed by dense fibrous connective tissue with a high content of elastic fibers. In the spinal canal between it and the vertebral bodies there is an epidural space filled with loose fibrous connective tissue rich in fat cells and containing numerous blood vessels.
The arachnoid mater (arachnoidea) is loosely adjacent to the dura mater, from which it is separated by a narrow subdural space containing a small amount of tissue fluid different from the cerebrospinal fluid. The arachnoid membrane is formed by connective tissue with a high content of fibroblasts; between it and the pia mater there is a wide subarachnoid space filled with cerebrospinal fluid, which is crossed by numerous thin branching connective tissue strands (trabeculae) extending from the arachnoid membrane and intertwined into the pia mater. Large blood vessels pass through this space, the branches of which supply the brain. On the surfaces facing the subdural and subarachnoid space, the arachnoid membrane is lined with a layer of flat glial cells covering trabeculae. The villi of the arachnoid membrane - (the largest of them - Pachionian granulations - are visible macroscopically) serve as areas through which substances from the cerebrospinal fluid return to the blood. They are avascular mushroom-shaped outgrowths of the arachnoid membrane of the brain, containing a network of slit-like spaces and protruding into the lumen of the sinuses of the dura mater.
The pia mater, formed by a thin layer of connective tissue with a high content of small vessels and nerve fibers, directly covers the surface of the brain, repeating its relief and penetrating into the grooves. On both surfaces (facing the subarachnoid space and adjacent to the brain tissue) it is covered with meningothelium. The pia mater surrounds the vessels penetrating the brain, forming a perivascular glial membrane around them, which later (as the caliber of the vessel decreases) is replaced by a perivascular limiting glial membrane formed by astrocytes.
2.Red bone marrow. Structure and functional significance.
Red bone marrow is the central organ of hematopoiesis and immunogenesis. It contains the bulk of hematopoietic stem cells, and the development of cells of the lymphoid and myeloid series occurs. . In the embryonic period, the BMC is formed from the mesenchyme in the 2nd month, and by the 4th month it becomes the center of hematopoiesis. KKM is a fabric of semi-liquid consistency, dark red in color due to the high content of red blood cells. A small amount of CMC for research can be obtained by puncture of the sternum or iliac crest.
In embryogenesis, red bone marrow appears at the 2nd month in flat bones and vertebrae, and at the 4th month in tubular bones. In adults, it is found in the epiphyses of tubular bones, spongy matter of flat bones, and bones of the skull. The mass of the red brain is 1.3-3.7 kg.
The structure of the red brain as a whole is subordinate to the structure of parenchymal organs.
Its stroma is represented by:
bone beams;
reticular tissue.
Erythroblastic islets typically form around a macrophage called a nurse cell. The nurse cell captures iron that enters the blood from old red blood cells that die in the spleen and gives it to the newly formed red blood cells for the synthesis of hemoglobin.
Maturing granulocytes form granuloblastic islands. Cells of the platelet series (megakaryoblasts, pro- and megakaryocytes) lie next to the sinusoidal capillaries. Megakaryocyte processes penetrate the capillaries and platelets are constantly separated from them. Small groups of lymphocytes and monocytes are found around blood vessels.
Among the red bone marrow cells, mature cells that are completing differentiation predominate (the depositing function of the bone marrow). They enter the bloodstream when necessary. Normally, only mature cells enter the blood.
Along with red, there is yellow bone marrow. It is usually found in the diaphysis of long bones. It consists of reticular tissue, which in some places is replaced by adipose tissue. There are no hematopoietic cells. Yellow bone marrow is a kind of reserve for red bone marrow. During blood loss, hematopoietic elements populate it, and it turns into red bone marrow. Thus, yellow and red bone marrow can be considered as two functional states of one hematopoietic organ.
Arteries that feed the bone take part in the blood supply to the bone marrow. Therefore, the multiplicity of its blood supply is characteristic. The arteries penetrate the medullary cavity and are divided into two branches: distal and proximal. These branches spiral around the central vein of the bone marrow. The arteries are divided into arterioles, which have a small diameter and are characterized by the absence of precapillary sphincters. Bone marrow capillaries are divided into true capillaries, which arise as a result of the dichotomous division of arterioles, and sinusoidal capillaries, which continue the true capillaries. Sinusoidal capillaries lie mostly near the endosteum of the bone and perform the function of selecting mature blood cells and releasing them into the bloodstream, and also participate in the final stages of blood cell maturation, influencing
In the red bone marrow, antigen-independent differentiation of B-lymphocytes occurs; during differentiation, B-lymphocytes acquire on their surface different receptors for various antigens. Mature B lymphocytes leave the red bone marrow and populate the B zones of the peripheral organs of immunopoiesis.
Up to 75% of B-lymphocytes formed in the red bone marrow die here (apoptosis-programmed cell death in genes). The so-called selection or selection of cells is observed, it can be:
“+” selection allows cells with the required receptors to survive;
"-" selection ensures the death of cells that have receptors for their own cells. Dead cells are phagocytosed by macrophages.
3. Intracellular regeneration. General morpho-functional characteristics. Biological significance.
Regeneration is a universal property of living things, inherent in all organisms, the restoration of lost or damaged organs and tissues, as well as the restoration of the whole organism from its parts (somatic embryogenesis). The term was proposed by Reaumur in 1712.
Intracellular regeneration is the process of restoration of macromolecules and organelles. An increase in the number of organelles is achieved by enhancing their formation, the assembly of elementary structural units, or by dividing them.
There are physiological and reparative regeneration.
Physiological regeneration
- restoration of organs, tissues, cells or intracellular structures after their destruction during the life of the body.
Reparative regeneration – restoration of structures after injury or other damaging factors. During regeneration, processes such as determination, differentiation, growth, integration, etc. occur, similar to the processes that take place in embryonic development.
Reparative is the regeneration that occurs after damage or loss of any part of the body. There are typical and atypical reparative regeneration.
With typical
regeneration, the lost part is replaced by the development of exactly the same part. The cause of the loss may be an external force (for example, amputation), or the animal may deliberately tear off part of its body (autotomy), like a lizard breaking off part of its tail to escape an enemy.
With atypical
During regeneration, the lost part is replaced by a structure that differs from the original quantitatively or qualitatively. The regenerated limb of a tadpole may have fewer fingers than the original one, and a shrimp may grow an antenna instead of an amputated eye.
the intracellular form of regeneration is universal, since it is characteristic of all organs and tissues without exception. However, the structural and functional specialization of organs and tissues in phylo- and ontogenesis “selected” for some the predominantly cellular form, for others - predominantly or exclusively intracellular, for others - both forms of regeneration equally.
Organs and tissues in which the cellular form of regeneration predominates include bones, skin epithelium, mucous membranes, hematopoietic and loose connective tissue, etc. Cellular and intracellular forms of regeneration are observed in glandular organs (liver, kidney, pancreas, endocrine system ), lungs, smooth muscles, autonomic nervous system.
Organs and tissues where the intracellular form of regeneration predominates include myocardium and skeletal muscles; in the central nervous system, this form of regeneration becomes the only form of structural restoration. The predominance of one or another form of regeneration in certain organs and tissues is determined by their functional purpose, structural and functional specialization.
Physiological regeneration is a process of updating the functioning structures of the body. Structural homeostasis is maintained, ensuring the ability of organs to constantly perform their functions. Is a manifestation of the properties of life, likeself-renewal(renewal of the epidermis of the skin, epithelium of the intestinal mucosa).
The value of R. for the body is determined by the fact that, on the basis of cellular and intracellular renewal of organs, a wide range of adaptive fluctuations and functional activity in changing environmental conditions is ensured, as well as restoration and compensation of functions impaired as a result of the action of various pathogenic factors. Physiological and reparative R. is the structural basis of the entire diversity of manifestations of the body’s vital activity in normal and pathological conditions.
Ticket No. 3.
1. Tonsils. Structure and functional significance.
Unlike the lymph nodes and spleen, which belong to the so-called lymphoreticular organs of the immune system, the tonsils are called lymphoepithelial organs. Since they carry out close interaction between epithelium and lymphocytes. The tonsils are located at the border of the oral cavity and the esophagus. There are paired (palatine) and single (pharyngeal and lingual) tonsils. In addition, there is an accumulation of lymphoid tissue in the area of the auditory (Eustachian) tubes (tubal tonsils) and in the ventricle of the larynx (laryngeal tonsils). All these formations form the Pirogov-Waldeyer lymphoepithelial ring surrounding the entrance to the respiratory and digestive tract.
Functions of the tonsils:
antigen-dependent differentiation of T- and B-lymphocytes;
barrier-protective;
censor function - control over the state of food microflora.
Internodular zones are the site of blast transformation of T-lymphocytes and maturation (T-zone). Here are post-capillary venules with high endothelium for the migration of lymphocytes. Plasmocytes, which are formed in B-zones, produce mainly class A immunoglobulin, but can also synthesize immunoglobulins of other classes. The supranodular connective tissue of the lamina propria contains a large number of diffusely located lymphocytes, plasma cells and macrophages. The epithelium in the crypt area is infiltrated with lymphocytes and granular leukocytes.
On the outside, the tonsil is covered with a capsule, which is essentially part of the submucosa. The end sections of the mucous minor salivary glands lie in the submucosa. The excretory ducts of these glands open on the surface of the epithelium between the crypts. Outside the capsule and submucosa lie the muscles of the pharynx.
The diameter of lymphatic capillaries under normal conditions ranges from 10-200 microns. It is several times greater than the diameter of blood capillaries (see figure below), which does not exceed 20 microns.
Blindly starting lymphatic capillary (indicated by two arrows),
the diameter of which exceeds the diameter of the blood capillary (indicated by one arrow)
Peritoneum of a dog. X 300.
The size of the diameter determines the participation of several endothelial cells in the capillary wall, and these diamond-shaped cells are 4 times larger in lymphatic capillaries than in blood capillaries. After fixation with glutaraldehyde, their cytoplasm usually appears more electron-light than the cytoplasm of endothelial cells of blood capillaries. In addition, there are no fenestrae in the wall of the lymphatic capillaries.
On ultrathin sections passed through the wall of the lymphatic capillaries, endothelial cells of two types are visible: one is flattened, spread out, the other is more rounded, with a nuclear-containing zone protruding into the lumen of the capillary (see figure below).
M. cremaster rats. JE - endothelial cell nuclei; CF - collagen fibrils; PA - arteriole lumen; PV - venule lumen; PLC - lumen of the lymphatic capillary. X 5300 (drug by I. D. Senatova).
Both types of cells contain ordinary cellular organelles: mitochondria, lamellar complex (Golgi apparatus), granular cytoplasmic reticulum. In addition, lysosomes, multivesicular and residual bodies are found here (see figure below - a, b).
Lysosome (a) and residual body (b) in the cytoplasm
endothelial cells of lymphatic capillaries
Fibrous capsule of the dog kidney. X 100000.
In the endothelial cells of lymphatic capillaries there are large vacuoles - the so-called symphysiosomes, which are formed as a result of the fusion of small smooth-contour vesicles. It is assumed that symphysiosomes can perform the functions of lysosomes. Sometimes foreign particles accumulate in them, including non-protein particles, which persist for up to 8 months.
The presence of vesicles, among which small ones predominate (up to 50 nm), indicates the participation of cells in transport, and the presence of lysosomes and other bodies in the cytoplasm indicates the absorptive and phagocytic functions of the endothelium of lymphatic capillaries.
“Microlymphology”, V.V. Kupiryanov, Yu.I. Borodin
- Basement membranes
