Multifunctional structure of human lymph nodes

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The structure of the human lymphatic system has long seemed a mystery. It was known to consist of large and small blood vessels, like blood vessels, and lymph nodes.

Lymph circulates through them - a whitish liquid containing a large number of immune cells. The interlacing of these vessels for a long time seemed chaotic to anatomists. This was partly due to the difficulties in studying the lymphatic system - its vessels are thin, stained with difficulty and it is not easy to trace their path from the skin to the internal organs.

The authors of this article are practicing surgeons: Head of the Department of Surgical Diseases No. 2 of the Hospital named after N. A. Semashko, professor E. V. Yautsevich and head of the department, professor G. V. Chepelenko. For many years, observing patients with edema of the lymphatic system in the clinic, they drew attention to the following phenomenon: the edema is often separated from the site of injury by a zone of healthy tissues. This fact, well known to many surgeons, suggested an ordered structure of the lymphatic system. It took about fifteen years to test the hypothesis; in the process of research, new details were revealed in the organization of the lymphatic system. It turned out that the skin and internal organs of a person are "divided" into special territories from which lymph is collected into strictly defined lymphatic vessels, and the entire system has an ordered structure, with features characteristic only of it.

The theory of the ordered structure of the lymphatic system immediately made it possible to obtain practical results. Already today, in our country and abroad, it is actively used in planning plastic surgery and surgery to lengthen the limbs, in the treatment of lymphatic edema.

Doctors of Medical Sciences E. LUTSEVICH and G. CHEPELENKO.

Double circulatory system

The lymphatic system plays a primary role in immunity - it is designed to protect the body from bacteria, viruses, foreign molecules. It is the counterpart of the circulatory system, which has large and small vessels passing under the skin and lymph nodes. A lymph-transparent-whitish liquid moves along them, consisting of large protein molecules and lymphocytes - immune cells.

The first to describe the lymphatic system was the Italian physician Gaspar Azelius in 1622. He observed white stripes in the mesentery of the intestine during the operation of a fed dog. At first he mistook them for nerves, but then accidentally damaged one of the stripes, and a white liquid similar to milk flowed out of it. Azelius realized that he had opened channels unknown to anatomists. He described his discovery in a famous work published after his death by his students. His recognition was also posthumous - already in our time, the International Society of Lymphology established a gold medal in his name for his work on the study of the lymphatic system. Azelius described the appearance and vessels of the lymphatic system, but he mistakenly believed that they go to the liver, where their contents are poured into the blood vessels. He illustrated his work with beautifully made color engravings, the first in the scientific literature.

Later, in 1653, professor at Uppsala University in Sweden, Olaus Rudbeck, expanded the concept of the lymphatic vessels as important elements of the body. At the same time, he wrote how difficult it is to find whitish vessels in yellowish adipose tissue - with light punctures, they generally disappear from the field of view. This observation remains true to this day.

Later, anatomists tried to study the lymphatic system using various dyes - mercury, ink, wax were injected with a needle into the tissue. The dyes were absorbed into the small subcutaneous lymphatic vessels and followed the path of the lymph to the nodes outside the studied organs. In this case, the lymphatic vessels became visible against the background of subcutaneous fat. The first thing that was seen with this method was the chaotic interlacing of many vessels, the connections between them, the disordered flow of lymph from any organs and tissues. For a long time, the dogma of the disorder in the structure of the lymphatic system prevailed in medicine. The method of study has not changed for almost three centuries.

In the early seventies of the XX century, an attempt was made to consider individual links of the transport routes of the lymphatic system. Academician of the Russian Academy of Medical Sciences V. V. Kupriyanov proposed staining with silver nitrate. With her help, it was possible to see valves in the capillary lymphatic network. Scientists have suggested that valves can change the direction of movement of lymph. Unfortunately, the method made it possible to see only the initial part of the vessels - directly under the skin - and did not make it possible to trace their structure in deeper layers of tissues.

New methods, such as a scanning microscope, casts from a structure using solidified plastics, and histochemistry, did not clarify the solution to the problem. All of them made it possible to see only the beginning of the lymphatic pathways, and large vessels in the depths of organs and tissues remained behind the scenes. However, we managed to find out some details.

The German physiologist Wenzel-Hora, using radiography and a scanning microscope, found that a system of tubules with valves from the skin gathers into a network that flows into one large outlet vessel, which penetrates the tissue 1-6 centimeters deep and flows into one of the collecting vessels in the subcutaneous - fatty tissue. The collecting vessels rise from the fingers and toes to the lymph nodes in the groin and axillary regions. Imagine the plumbing system of a multi-storey building - the water pipes from each apartment are collected in a larger pipe that goes from the house to the main city water supply - something similar happens when the lymph flows. However, further this scheme did not succeed in broadening the understanding of the structure of the lymphatic system. A fundamentally new research method was needed.

Gradually, interest in the study of the lymphatic system waned - in the world literature for every 500 scientific papers devoted to the study of the circulatory system, there was one work on the study of the lymphatic system. Researchers rushed to other areas of lymphology - immunology, histology. The essential role of the lymphatic system in immune processes has been proven. For a number of works in this area, Nobel Prizes were awarded. However, the structure of the lymphatic system was still a mystery to anatomists.

Mysterious edema

Having been engaged in clinical observations for many years, we drew attention to an interesting fact. When the lymphatic vessels are damaged, edema often develops at a great distance from the injury site, and completely healthy tissue is located between the injury site and the edema. For example, if the lymphatic bundle below the shoulder is damaged, the swelling can seize the hand, and the forearm and shoulder to the site of injury look completely healthy. A completely different picture with damage to blood vessels. When blood is taken from a vein and the veins of the forearm are bandaged, the veins below the bandage are overflowing with blood. When a vein is damaged, edema develops, which always reaches the level of injury.

If the lymphatic vessels are damaged, the edema does not reach the level of injury by 15-20 centimeters, asymmetric edema occurs when one edge or surface of the limb increases, and the rest of the tissues look completely healthy. To understand what happens in this case, a contrast agent was injected into different groups of lymphatic vessels of one limb and found that one group of them contains intact vessels - they pass lymph and the tissues look healthy. At the same time, the other group is damaged, and the flow of lymph is hampered or stopped, a kind of damming up of the lymphatic channel occurs - in this place edema develops. Extensive material has been accumulated on the study of such limited edema, articles have been published in domestic and foreign journals. The result of this work was the hypothesis that the lymphatic system has an ordered organization.

We assumed that the skin is divided into areas not visible to the eye - subsegments. From each subsegment, the smallest lymphatic vessels collect lymph into the outflow vessel, which then flows into a larger guide vessel, which goes in a group of such vessels to a strictly defined lymph node. In the course of movement, a redistribution of lymph constantly occurs.

In other words, all elements of the lymphatic bed can be divided into three types - orienting the free outflow of lymph in the skin (small capillaries and vessels with valves), then the diverting vessels that collect lymph from large areas of the skin and carry it into the subcutaneous tissue, and finally distributing large vessels to the lymph nodes. In this case, the skin is divided into limited areas - subsegments from which small capillaries collect lymph. Each subsegment is connected by lymph flow with a strictly defined discharge vessel. Adjacent subsegments can be "subordinate" to completely different large vessels.

The skin is thus a mosaic of different zones. The outdated technique used by anatomists could not clarify the picture. A special methodological technique could confirm this hypothesis. It was decided to conduct studies of the lymphatic vessels in trauma: dyes were injected not into the skin, but into large major vessels. The dye was transported with the lymph flow to the site of injury, where the lymph flow was interrupted. Then, with the reverse flow of lymph, the dye entered the smaller vessels and stained the subsegments, which were really mosaic on the skin.

This method has been called retrograde reconstruction of the lymphatic system. It made it possible to investigate all the links in the movement of lymph from the smallest vessels in the skin to large great vessels. So it was possible to determine the boundaries of the territories on the skin, subordinate to one or another lymphatic vessel passing through the subcutaneous fat. The points of origin of the vessels, the size of the zones subordinate to them, the number of such zones flowing into the groups of large lymphatic vessels were also identified.

From chaos to order

Reconstruction of the lymphatic areas of the skin made it possible to recreate the spatial picture of the groups of the abducting vessels of several neighboring areas. It turned out that the smallest vessels - capillaries - collect lymph from large areas, then, like rivulets, flow into larger ducts. In these larger vessels there are valves that orient the lymph flow in a strictly defined direction - to certain distributing vessels, which already carry the lymph to the lymph nodes. Multiple capillaries are combined into a group and have a drain into one outlet vessel, which flows into a large vessel between two points of its branching. Depending on the length of this vessel, the lymphatic zone (segment) subordinate to this vessel is determined - if its length to the bifurcation point is large, then the subordinate zone is large, if the bifurcation points are close to one another, the lymphatic zone is small.

Each outlet vessel is the center of the drainage area of the skin measuring from 1.5 to 3.5 centimeters. This site was named a sub-segment. The wider area that supplies lymph to a large lymphatic vessel has been called a segment. The number of lymph segments, for example on the lower leg, may vary from person to person.(However, the general principle of the structure of the lymphatic system is the same for everyone.) For example, in the lower part of the leg there are usually 1-4 lymphatic segments, in the upper half - from 2-4 to 10-12. On the thigh, the number of lymphatic segments is 12-19, on the forearm - 10-15.

The lymphatic segment is usually elongated along a large collecting vessel that extends beneath it. Its width is no more than 2–3 sub-segments, and its length is 8–10 groups of sub-segments. At the same time, several special subsegments are "inserted" inside it, from which lymph flows immediately into deeper vessels. Nature has foreseen the possibility of lymph accumulation in case of injury, and then these subsegments play the role of a discharge channel - they do not allow the overflow of the lymphatic pathways.

The German anatomist Kubik also described single discharge vessels that collect lymph from a certain area of the skin and have an outflow into the deep layers of the skin. This phenomenon can be demonstrated using a simple practical example - if a person sleeps with a bent arm under his head, the lymphatic vessels of the arm overflow, but swelling does not occur - precisely because the lymph is discharged through the "inserted" subsegments.

So, the skin (like other tissues and internal organs) is divided into certain territories, from which the lymph flow is directed first to the capillaries, then to the discharge vessel, and the latter, combining from several subsegments, flow into large lymphatic vessels that direct lymph to the lymph nodes … The skin is like a mosaic of such territories of various sizes. Lymph does not cross the borders of the territories normally - only in the case of injuries, when the vessels overflow and part of the fluid seeps through their walls. The lymph along the entire length to the large vessels does not mix, although the diverting vessels intersect in the subcutaneous fat. But the cross of vessels is imaginary - it occurs in different planes. Lymph mixes only in large vessels.

Large vessels in the subcutaneous fat are a junction of channels 40-50 centimeters long. They lie at different depths from the skin surface. According to the apt expression of the Czech radiologist K. Bend, together with the lymphatic capillaries in the skin, they form an interconnected network, reminiscent of a triple "stocking". However, each layer in the "stocking" is strictly ordered, connected to the others through ordered rather than chaotic connections and directs the flow of lymph upward.

In these flows, the lymph from the various segments is already mixed, since they have many ramifications and intersections. This phenomenon can be compared with the mixing of the waters of the tributaries of a large river - before that they flowed separately, collecting water from smaller streams, and in its bed the waters were mixed so that later they could disperse along different branches heading to their destinations - the lymph nodes.

Practical results

The segmental theory of the structure of the lymphatic system allows you to take a fresh look at the treatment of some surgical diseases and propose new methods of surgical intervention. For example, in plastic surgeries, markings are usually made for the passage of blood vessels in the skin. It makes sense to mark the lymphatic vessels and then make skin incisions along the boundaries of the segmental territories - in this case, healing is easier, the fine structure of the lymphatic ducts is preserved. Identification of skin segments is done using fluorescence microscopy, injecting special contrast agents. Now such operations are already being carried out abroad and in our country and are giving good results. This was shown by the International Symposium on New Directions in Lymphology and Vascular Surgery at the Institute of Surgery. A. V. Vishnevsky.

In addition, for diseases of the lymphatic system, for example, with chronic edema, it is recommended to do a special massage, taking into account the location of the injured segments. Massage allows you to "push" stagnant lymph through the ducts. At the same time, the same insertion subsegments that have a direct outflow of lymph into deep vessels are activated - they allow you to "dump" excess fluid. Such massage is widely used in Germany and is successfully replacing surgical methods in the treatment of chronic edema. The patient is also taught self-massage.

The possibilities of microsurgical methods in the treatment of disorders of the lymphatic system have also expanded. In case of injuries, there may be vascular disorders not only in the visible part, but also along the course of other lymphatic vessels of different levels. Segmental theory

the structure of the lymphatic system allows predicting the movement of edema from the site of injury to other areas. Knowing the structure of the lymphatic bed of the injured limb, one can predict the appearance of edema in a particular area and take measures in advance - prescribe anti-inflammatory treatment or "preventive" surgery. For example, in some clinics in Germany, while removing mammary glands from women, they simultaneously perform preventive surgery on the forearm or shoulder to avoid swelling in this area.

Knowledge of the segmental structure of the lymphatic system is also necessary in operations to lengthen the limbs. In the case of defects in the development of bone tissue, a person's leg or arm can be shortened by 10-20 centimeters. At the same time, persistent edema of the lymphatic tract in the area of violation often develops. When the bone is lengthened with the help of an operation, it is necessary to take into account the location of the lymph segments in the operation area - the operation must take place outside the affected segment, otherwise it will aggravate the disease. In some cases, it is possible to advise and preliminary elimination of lymphatic edema, and then surgery on the bone tissue. Developments in this direction are intensively carried out at the Department of Surgical Diseases of the Second Moscow Medical Dental Institute named after N. A. Semashko.

Currently, the basis for the treatment and prevention of diseases of the lymphatic system, not only in our country, but also abroad is the theory of the segmental structure. It provides a key to deciphering many clinical symptoms in diseases of the lymphatic system - the most important structure in the immunity of the human body.