All about lymph. Rules to know! The overall rate of lymph flow Vessels through which lymph moves in the body

The lymphatic system is closely related to the circulatory system. The supply of tissues with nutrients and oxygen from the blood occurs through the tissue fluid. 1/4 of the total body weight is tissue fluid and lymph. Penetrating into the lumen of the lymphatic capillaries, tissue

"The structure of the lymph circulation system"

The lymphatic system consists of lymphatic capillaries, small and large lymphatic vessels and lymph nodes located along them.

Lymph composition:

There are about 1500 ml of lymph in the body. It consists of lymphoplasm and formed elements suspended in it. Lymphoplasma is similar to blood plasma, but contains fewer proteins. FEK - lymphocytes, erythrocytes are usually absent. The lymph contains fibrinogen, so it is able to coagulate, forming a loose, slightly yellowish clot. Lymph is an almost clear, colorless liquid.

Lymph formation

The source of lymph is tissue fluid. It is formed from the blood in the capillaries and fills all intercellular spaces. Water and substances dissolved in the blood plasma are filtered from the blood capillaries into the tissues, then from the tissues into the lymphatic capillaries. Lymph formation depends on from hydrostatic (blood) oncotic blood pressure in the capillaries and tissue fluid An increase in blood pressure in the capillaries contributes to the filtration of fluid from the vessel into the interstitial spaces, and a decrease causes a reverse flow of fluid from the intercellular spaces of the capillaries. The oncotic pressure of the plasma due to proteins contributes to the retention of water in the capillary blood. The hydrostatic pressure in the capillaries contributes, and the oncotic pressure of the blood plasma prevents the filtration of fluid through the walls of the blood capillaries and the formation of lymph. Filtration of fluid in the blood capillary occurs only at its arterial end, in the initial part of the capillary. At the venous end of the capillary, the opposite process is noted - the flow of fluid from the tissue into the capillaries. This is due to the fact that the blood pressure on its way from the arterial end to the venous one falls, and the oncotic one increases due to some thickening of the blood. The permeability of the walls of lymphocapillaries can change due to the functional state of the organ, under the influence of capillary poisons (histamine) entering the bloodstream, and mechanical factors. In a hard-working organ, the oncotic pressure to the fluid is greatly increased. This causes the flow of water into the tissues from the blood and enhances lymph formation.

Causes of the movement of lymph through the lymphatic vessels

1. The continuous formation of tissue fluid and its transition from the interstitial spaces to the lymphatic vessels ensures a constant flow of lymph.

2. Contractility of some lymphatic vessels.

3. Negative pressure in the chest cavity and an increase in the volume of the chest during inspiration, which causes the expansion of the thoracic lymphatic duct, which leads to suction of lymph from the lymphatic vessels.

4. Muscle work. The movement of lymph, as well as venous blood, is facilitated by flexion and extension of the legs and arms while walking. When the contractions are compressed, the lymphatic vessels, which causes the lymph to move in only one direction.

Functions of the lymphatic system

1. Conductor- Lymphatic vessels serve to drain lymph. They are, as it were, a drainage system that removes excess tissue fluid in the organs.

2. Barrier - The lymph flowing from the tissues passes on its way to the veins through biological filters - the lymph nodes. Here, some foreign bacteria and harmful substances that have entered the body linger and do not enter the bloodstream. They come from the tissues into the lymphatic, and not into the blood capillaries due to the greater permeability of the walls of the former compared to the latter. The lymph contains immune antibodies that phagocytize pathogenic microbes.

3. Exchange - absorption and transfer from the digestive tract of nutrients, relatively large particles of which cannot be absorbed into the blood through the walls of blood capillaries, as well as the transport of metabolic products from organ tissues.

4. Hematopoietic - immune antibodies are produced in the lymph nodes and lymphocytes multiply.

5. With pathology Microorganisms and cells of malignant tumors (metastases) are transferred through the lymphatic system.

1. Lymph capillaries - penetrate all tissues, except for the brain and spinal cord and their membranes, skin, placenta, cornea and lens of the eye.

Peculiarities: begin blindly in the intercellular space, one end of them is closed. Unlike blood capillaries, their wall consists of only one layer of endothelium. Due to the lack of a basement membrane, endotheliocytes are in direct contact with the intercellular connective tissue and tissue fluid. The lumen of the lymphatic capillaries is wider than the blood capillaries, and their walls are more permeable. Larger lymphatic vessels begin from lymphocapillary networks.

2. Lymphatic ducts:thoracic duct, right lymphatic.

These are the largest lymphatic vessels. They go into veins.

thoracic duct- begins in the abdominal cavity at the level of the 2nd lumbar vertebra as a result of the fusion of the right and left lumbar trunks and the intestinal trunk. The initial part of it is expanded - cistern of the thoracic duct. Then, to the left of the spinal column, it rises, enters the chest cavity through the aortic opening of the diaphragm, exits into the neck region, where it flows into left venous angle. Its length is 20 - 40 cm. The left bronchomediastinal, subclavian and jugular lymphatic trunks. Through the thoracic duct, lymph enters the venous blood from the body, except for the right half of the head and neck, the right half of the chest and the right upper limb.

Right lymphatic duct- shorter than the chest, located in the neck on the right; It is formed from the right bronchomediastinal, jugular and subclavian trunks. It collects lymph from the right half of the head, neck, upper limb and right half of the chest and flows into the right venous angle.

The lymph nodes - are small, oval or bean-shaped, located along the lymphatic vessels. The node is covered with a connective tissue capsule, from which thin partitions extend inside - trabeculae, separating from each other sections of the parenchyma of the node, which have the function of support and environment for capillaries. The parenchyma consists of lymphoid tissue - a complex of lymphocytes, plasma cells and macrophages located in a cellular - fibrous connective tissue basis.

The lymph node has convex and concave edges. Through the concave edge - the gate, arteries and nerves enter the nodes, and veins and efferent lymphatic vessels exit, from the convex side, the afferent lymphatic vessels flow into the node. Several lymphatic vessels enter the lymph node, and one comes out. On the cut you can see:

1. Along the periphery of the node - cortex with lymphatic follicles- nodules of a rounded shape; in the loops of the reticular tissue (their stroma) are blood cells; lymphocytes multiply here;

2. Paracortical zone(pericortical) or thymus - dependent; here T-lymphocytes multiply and mature;

3. medulla: stroma - reticular tissue in the form of paths from the periphery to the center - brain cords, in them B - lymphocytes and plasma cells derived from them, which synthesize protective substances - antibodies. Between the capsule and trabeculae, on the one hand, and the follicles and brain cords, on the other hand, the cerebral sinuses are slit-like spaces through which lymph flows, is cleared of foreign structures and carries lymphocytes and immune antibodies through the gate.

Usually lymph nodes are located in groups. Each group receives lymph from a specific area.

Functions of the lymph nodes:

1. Hematopoietic;

2. Immunopoetic;

3. Protective - filtration;

4. Exchange;

5. Reservoir.

Lymphatic trunks: jugular, subclavian, bronchomediastinal, lumbar, intestinal. Several lymphatic vessels that leave the lymph nodes and carry lymph from certain areas are connected to larger vessels - the lymphatic trunks. Distinguish:

1. The jugular trunk, right and left, carries lymph from half of the head and neck;

2. Right and left subclavian trunks - by hand

3. Bronchomediastinal trunk right and left - from the organs and walls of half of the chest

4. Right and left lumbar trunks - from the lower extremities, pelvis and abdominal walls

5. Intestinal trunk - from the organs of the abdomen.

Lymphatic vessels:intraorganic and extraorganic; bringing and taking out; superficial and deep: small, medium, large. Several capillaries merge and form lymphatic vessel. Here is the first valve.

Intraorganic- in the organs they anastomose with each other, forming plexuses. From the organs, lymph flows through extraorganic lymphatic vessels. The lymph goes through the vessels to the lymph nodes. The lymphatic vessels through which lymph enters the lymph nodes are the afferent ones, and through which the lymph flows out of them - the efferent ones.

Depending on the depth of occurrence in a given area or organ, the lymphatic vessels are divided into superficial and deep. Between them are anastomoses.

All lymphatic vessels have valves, allowing the flow of lymph in only one direction: from the organs to the lymphatic ducts, and from them to the veins. The presence of valves gives a clear look.

Lymph nodes of certain areas of the body

Organs of the immune system

Or lymphoid organs; composed of lymphoid tissue.

Approximately 100 ml of lymph flows through the thoracic duct of a person at rest in one hour, and approximately 20 ml of lymph enters the circulation every hour through other channels, so the total lymph flow detected is about 120 ml per hour.

This is 1/120,000 of the calculated rate of fluid diffusion back and forth through the membranes of the capillaries, and it is a tenth of the rate of filtration from the arterial ends of the capillaries into the tissue spaces of the whole body.

These facts indicate that the flow of lymph is relatively small compared to the total fluid exchange between plasma and interstitial fluid. Factors that determine the rate of lymph flow. Interstitial fluid pressure.

An increase in interstitial free fluid pressure compared to its normal level of 6.3 mm Hg. increases the rate of flow in the lymphatic capillaries. The increase in flow rate becomes progressively greater as the pressure of the interstitial fluid increases until this pressure value reaches a value slightly greater than 0 mmHg, in which case the flow rate reaches a maximum, it increases from 10 to 50 times compared to normal.

Thus, some factor, other than the obstruction of the lymphatic system itself, may lead to an increase in interstitial pressure, which increases the speed of lymph flow.

Such factors include: increased capillary flow; reduced osmotic pressure of plasma colloids; increased protein content in the interstitial fluid; increase in capillary permeability.

lymphatic pump. Valves are present in all lymphatic channels into which the lymphatic capillary flows.

In large lymphatic vessels, the valves are located every few millimeters, and in small lymphatic vessels, the valves are located somewhat more often, which indicates a wide distribution of valves. The lymph vessel is compressed under pressure for some reason, the lymph is pushed in both directions, but since the lymph valve is open only in the central direction, the lymph moves in only one direction.

Lymphatic vessels can be compressed either by contraction of the walls of the lymphatic vessel or by pressure from surrounding structures.

Filming of an exposed lymphatic vessel, both in animals and humans, has shown that if at any time the lymphatic vessel is stretched by fluid, the smooth muscle in the vessel wall automatically contracts.

Further, each segment of the lymphatic vessel between the valves acts as a separate automatic pump. Namely, the filling of the segment causes it to contract and the fluid is pumped through the next valve to the next lymphatic segment.

The next segment is thus filled, and after a few seconds it also contracts; this process continues along the entire lymphatic vessel until the fluid finally expires. In a large lymph node, this lymphatic pump can generate a pressure of 25 to 50 mmHg if the vessel outlet is blocked.

In addition to pumping caused by internal contraction of the walls of the lymphatic vessel, pumping can be caused by other external factors that compress the lymphatic vessel. In order of importance, these factors are: muscle contraction; movement of body parts; arterial pulsations; tissue compression by objects outside the body.

The outflow of lymph from the organ, in general, is the more significant, the more intensively the organ works. If, for example, it is irritated in a dog, then the secretion of the submandibular gland increases, and at the same time, the outflow of lymph from the lymphatic vessels of the gland increases.

One might think that this depends on the simultaneous expansion of the blood vessels in the gland; however, if the gland is poisoned with atropine and then the notochord is irritated, then the outflow of lymph does not increase, despite the fact that the blood supply to the gland increases in exactly the same way as before.

Similarly, one can increase the outflow of lymph from the liver, stimulating increased production of bile by intravenous injection of sodium taurocholate or hemoglobin, or from the pancreas, increasing its secretion by injecting secretin.

Further, already Claude Bernard and Ranke observed that an active gland or an active muscle extracts water from the blood flowing through them. When attempting a physicochemical interpretation of these phenomena, one should first of all take into account that, in general, during the process of metabolism in organs, large molecules are split into numerous small ones, and since osmotic pressure is a function of the number of molecules, due to this, hand in hand with an increase metabolism and an increase in osmotic pressure.

This effect of metabolism can be seen if, for example, both kidneys are cut out from a dog. Since the function of the kidneys is to remove excess molecules from the body in the form of metabolic end products, after extirpation of them, even when the animal is starving, the osmotic pressure of the blood grows and grows, and therefore its freezing point decreases, for example from -0.56 to - 0.75.

Thus, one can imagine as a direct effect of the work of the organs an increased absorption of water from the flowing blood by osmosis.

Subsequently, the organs are freed from this excess water, and in this respect a number of factors must be taken into account, namely, firstly, the turgor of the organs; when the working organs are very filled with tissue water, then their capsules, penetrated by elastic fibers, stretch, strain and thus can press the liquid out (at least under the assumption that the resistance to flow periodically changes).

Secondly, any pressure on the organs from the outside contributes to the flow of lymph, and this is all the more so since there are valves in the lymphatic vessels that, like venous valves, allow flow in only one direction - towards the thoracic duct.

Further, the lymphatic vessels reproduce peristaltic contractions (Geller), which again, together with the valves, ensure the outflow of lymph. Then, with each inhalation movement, the lymph is sucked into the thoracic duct due to an increase in negative pressure in the chest cavity.

Finally, there are local special devices for the movement of lymph. These include smooth muscles contained in the capsule and crossbars of the lymph glands; they can squeeze out the contents of the glands during their contraction.

In the same way, the villi of the intestine, by their rhythmic movements, pump the lymph from the central lymphatic vessel to the larger lymphatic vessels of the mesentery, and some animals have special lymphatic hearts as special lymph motors. In a frog, for example, two of these hearts lie on both sides of the sacrum and two above the shoulder girdle.

Heidenhain drew attention to the special chemicals that cause the formation of lymph, the so-called lymphogenous agents. These are substances alien to the body, for example, extracts from leeches, crayfish muscles, shells, strawberries, bacteria, further - tuberculin, peptone, chicken protein, bile. The effect of these funds has not yet been sufficiently analyzed.

There are two types of lymph formation:

1. At zero or even negative interstitial pressure and the absence of interendothelial gaps in the lymphatic capillaries, it is characterized by a diffusion transition of protein and other large molecular compounds into the lymphatic channel in the presence of an appropriate protein concentration gradient between the lymph and interstitial fluid.

2. With a positive interstitial pressure and open interendothelial junctions of the lymphatic capillaries, it is characterized by the transition of the interstitial fluid into the lymphatic channel due to the hydrostatic pressure difference.

Such conditions are typical for hydrated tissues, and the mechanism of lymph formation corresponds to the filtration-resorption theory. The regulation of the lymph formation process is aimed at increasing or decreasing the filtration of water and other elements of the blood plasma (salts, proteins, etc.) by the autonomic nervous system and humoral-vasoactive substances that change blood pressure in arterioles, venules and capillaries, as well as the permeability of vessel walls.

For example, catelchomines (adrenaline and norepinephrine) increase blood pressure in venules and capillaries, thereby increasing fluid filtration into the interstitial space, which enhances lymph formation.

Local regulation is carried out by tissue metabolites and biologically active substances secreted by cells, including the endothelium of blood vessels. Obviously, the lymphatic pump becomes very active during exercise, often increasing lymph flow by 5-15 times.

On the other hand, during rest, the flow of lymph is very weak. Lymphatic capillary pump. Many physiologists suggest that the lymphatic capillary is also capable of pumping lymph, in addition to the lymphatic pump of the large lymphatic vessels. As explained earlier in the chapter, the walls of the lymphatic capillaries are intimately connected to the surrounding cells through their attachment filaments.

Thus, at the time when excess fluid enters the tissues and tissue swellings, the attachment threads cause the lymphatic capillaries to open and fluid flows into the capillary through the junctions between the endothelial cells.

Thus, when the tissue is compressed, the pressure inside the capillary rises and forces the fluid to move in two directions: first, backward, through the openings between the endothelial cells, and second, forward, into the collecting lymphatic vessels.

However, because the edges of endothelial cells normally overlap within the lymphatic capillary, backflow is prevented by overlapping cells over the openings.

Thus, the openings close, they act as one-way valves, and very little fluid flows back into the tissues.

On the other hand, lymph that moves forward into the collecting lymphatic vessel does not return to the capillary after the compression cycle is completed because many valves in the collecting lymphatic vessel block any back flow of lymph.

Thus, some factor that causes constriction of the lymphatic capillaries is likely to cause the fluid to move in the same way that the constriction of large lymph nodes causes the lymph to sway.

The flow of interstitial fluid into the lymphatic capillaries. The walls of the lymphatic capillaries and postcapillaries are represented by a single layer of endothelial cells. The endothelial cells of the lymphatic capillaries are fixed to the surrounding connective tissue by the so-called supporting filaments. At the contact points of endothelial cells, the end of one endothelial cell overlaps the edge of another cell. The overlapping edges of the cells form like valves protruding into the lymphatic capillary. These valves regulate the flow of interstitial fluid into the lumen of the lymphatic capillaries.

Lymph formation.

Lymph formation is associated with the transfer of water and a number of substances dissolved in blood plasma from blood capillaries to tissues, and from tissues to lymphatic capillaries.

With the accumulation of interstitial fluid, the supporting filaments act as cables and open the inlet valves. Since the pressure of the interstitial fluid in this case is higher than the pressure in the lymphatic capillary, the interstitial fluid, together with the blood cells that have left the microvasculature, is directed to the lymphatic capillaries. This movement continues until the lymphatic capillary is full. At the same time, the pressure in it increases and at the moment when it exceeds the pressure of the interstitial fluid, the inlet valves close ( first pump).

Capillary permeability is not the same. Thus, the wall of liver capillaries has a higher permeability than the wall of skeletal muscle capillaries. This explains the fact that approximately more than half of the lymph flowing through the thoracic duct is formed in the liver.

The permeability of blood capillaries can change under various physiological conditions, for example, under the influence of the so-called capillary poisons (histamine, etc.) entering the blood.

In the formation of lymph, the processes of filtration, diffusion and osmosis are important.

Factors that ensure the formation of lymph:

· The difference in hydrostatic pressure in the blood capillaries and interstitial fluid. An increase in hydrostatic pressure increases the production of lymph.

Permeability of the walls of blood capillaries. An increase in the permeability of the capillary walls leads to an increase in the formation of lymph (capillary poisons, istamine, etc.). It can change under various functional states of the organ.

Oncotic blood pressure. It prevents the formation of lymph (plasma proteins).

Osmotic pressure in tissues. Osmotic pressure in tissues can increase when a large number of dissimilation products pass into the tissue fluid and lymph. This increases the flow of water from the blood into the tissues.

The difference between hydrostatic and oncotic pressure corresponds to the filtration pressure (6-10 mm Hg).

Additional factors for the formation of lymph:

Ø Pressure fluctuations in tissues during arterial pulsation,

Ø Muscle contraction (“muscle pump”),

Ø Valves, when squeezing blood vessels, create a suction effect of fluid from tissues,

Ø Lymphogens.

Distinguish lymphogonal I and II order.

Lymphogenic I order are capillary poisons that increase the permeability of their walls (histamine, peptone, strawberry extract).

Lymphogenic II order - substances that enhance the filtration of fluid from the blood (hypertonic solutions of glucose, NaCl, concentrated solutions of some salts), which, once in the blood, quickly leave the bloodstream and create increased osmotic pressure in the interstitial space, contributing to the release of H 2 O from the blood.

Under normal conditions, there is a balance in the body between the rate of lymph formation and the rate of lymph outflow from the tissues. The outflow of lymph from the lymphatic capillaries is carried out through the lymphatic vessels, which are a system of collectors, which are chains lymphangiomas . Lymphangion- intervalvular segment - structural and functional unit. It has a teardrop shape, limited by valves, distally - expanded, proximally - narrowed. In the middle section of the lymphangion there is a muscular "cuff" (longitudinal and circular layers of smooth muscles). Lymphangion - peripheral heart of the system second pumps lymphatic system. Each lymphangion functions as a separate automatic pump. Filling the lymphangion with lymph causes contraction of smooth muscles in the wall of the lymphangion, increases the pressure inside it to a level sufficient to close the distal valve and open the proximal one. The lymph is pumped through the valves to the next segment, and so on, until the lymph enters the bloodstream. In large lymphatic vessels (for example, in the thoracic duct), the lymphatic pump creates a pressure of 50 to 100 mmHg.

The work of the SMC of lymphangions obeys the Frank-Starling law. With an increase in the load on the lymphatic tract (in this case, the volume of lymph increases), the stretching of the walls of the lymphangion increases, which leads to an increase in the force of its contraction, and the lymph flow increases within certain limits.

Third pump in the lymphatic system - a lymph node, it contracts 6 - 8 / min

Additional factors that ensure the movement of lymph through the vessels are:

Interstitial fluid tissue pressure (permanent plasma filtration)

Massaging action of tissues (contraction of skeletal and smooth muscles surrounding the lymphatic vessels, pulsation of the arteries. The presence of valves is a kind of muscular pump).

Any passive movement of the limb or torso. Displacement of internal organs, peristalsis. Compression of blood vessels from the outside - massage.

Respiratory pump (negative pressure in the chest cavity. When inhaling 6-8 cm, exhaling - 3-5 cm of water column).

· Lymphatic pump. Rhythmic contractions (10-15 per minute) of lymphatic vessels (presence of valves).

Diaphragm movement. When inhaling, the pressure of the diaphragm is exerted on the internal organs of the abdominal cavity, squeezing the lymph out of their vessels. They have a suction effect on the lymph flow in the thoracic duct (like a vacuum pump).

At rest, up to 100 ml of lymph per hour passes through the thoracic duct, about 20 ml through the right lymphatic duct. Every day, 2-3 liters of lymph enter the bloodstream.

Thus, the fluid that has left the blood in the capillaries returns to the bloodstream again, bringing a number of cellular metabolic products.

Along the course of the lymphatic vessels are located The lymph nodes, performing the role of organs of lymphopoiesis, lymph depot and performing a barrier-filtration function (macrophages). Passing through the lymph nodes, the lymph is enriched with lymphocytes and antibodies, and is also cleansed of foreign particles - microbial bodies, dead and tumor cells, dust particles, which are trapped here and partially destroyed. In the lymph nodes, tumor cells can multiply, which leads to the formation of a secondary tumor (metastasis). Lymph nodes are located in protected and mobile places, near joints or large vessels. Their size is from 1 to 50 mm.

The sympathetic nervous system is involved in the regulation of lymph drainage. An increase in its tone causes contraction and spasm of the lymphatic vessels up to the cessation of the outflow of lymph. The movement of the lymph changes reflexively during painful stimuli, irritation of the receptors of the blood vessels of the internal organs.

Lymphatic insufficiency. If the load on the lymphatic pathways or the volume of ultrafiltrate increases, then the volume of lymph also increases - the so-called safety valve mechanism (an active mechanism aimed at preventing edema) is activated. However, the volume of lymph can increase only up to a certain limit, limited by the transport capacity of the lymphatic vessels. If the volume of ultrafiltrate formed per unit of time exceeds the transport capacity of the lymphatic vessels, then the reserve of the lymphatic pump is depleted and lymphatic insufficiency occurs, manifested by edema. Any factor that interferes with the normal functioning of lymphangions reduces the transport capacity of the lymphatic vessels. A combined form of lymphatic insufficiency is possible, when excessive accumulation of interstitial fluid is caused not only by an increase in the volume of the ultrafiltrate, but also by a decrease in transport capacity due to the pathology of the lymphatic vessels themselves.

Blood circulation in the myocardium. The heart is supplied with blood by the right and left coronary arteries. The right artery supplies blood to the right ventricle, the interventricular septum, and the posterior wall of the left ventricle. The left artery supplies blood to the rest of the departments. The total surface of the capillaries in the heart is 20 m 2 . The outflow of blood is carried out into the venous sinus, which opens into the right atrium and through the Tebesian veins. At rest, the amount of blood flow in the heart is 200-250 ml / min (5% of the IOC). With exercise, blood flow increases by 3–4 l/min. Blood flow is affected by: fluctuations in blood pressure in the aorta, changes in its shape and size during the cardiac cycle. During systole, the blood vessels are compressed, blood flow weakens, and in diastole, blood flow increases.

Even at rest, the myocardium consumes significantly more oxygen than other organs. The lack of oxygen is a powerful stimulus for the dilatation of the coronary vessels, it occurs already when the oxygen content in the blood decreases by 5%. The cessation of blood flow in the myocardium leads to a state of ischemia. When the supply of oxygen is interrupted, a state of anoxia occurs.

The nervous regulation of blood flow in the heart has not yet been fully elucidated. The sympathetic nervous system can both constrict and dilate blood vessels. With the receipt of frequent pulses, vasoconstriction of the coronary vessels is observed, with rarer pulses, dilation is observed. If frequent impulses come through the parasympathetic nerves, dilation occurs, with rarer ones, the vascular tone increases, some constriction occurs.