Little known, but very important, the lymphatic system allows the lymph to flow into the body tissues, draining every corner of the body before it spills into the thoracic veins. Parallel to the cardiovascular system, the lymphatic system is opposed to excessive accumulations of fluids in the tissues and is considered the defense bulwark of our body. In fact, along the lymphatic pathways there are organs, called lymph nodes, capable of producing so-called lymphocytes, a special series of white blood cells responsible for eliminating hostile microorganisms. When the body is fighting an infection the lymph nodes accelerate the synthesis and transformation of these lymphocytes, thus increasing in volume and becoming appreciable and painful to the touch (hence the expression "having enlarged lymph nodes").
The lymphatic system consists of an articulated system of vessels, very similar to the venous and arterial circulatory system. Unlike blood, the lymph is not pushed by cardiac activity, but flows in the vessels moved by the action of the muscles. By contracting and relaxing, these fabrics function like a real pump. When this action fails, for example due to excessive immobility, the lymph tends to stagnate, accumulating in the tissues. This explains how feet and ankles never swell when you stand for a long time in a static position. For the same reason, when the leg is immobilized by a cast, it is necessary to keep it raised above the level of the heart (just to ensure that the force of gravity facilitates lymphatic drainage).
Similar to those of the cardio-circulatory system, the smaller lymphatic vessels, called capillaries, are found in the peripheral regions of the body and, coming together, give rise to larger and larger vessels, until they flow into the thoracic duct. Unlike blood vessels, lymphatic capillaries are blind-bottomed and have an even thinner wall, formed by cells separated by large openings. The lymph carried by the thoracic duct, joining to that present in the vessels coming from the upper part of the body, is poured at the level of the conjunction between the succlavia veins and the jugular vein.
In correspondence of some junctions between the various lymphatic ducts, located in strategic points of the organism, we find real filtering stations called, precisely, lymph nodes. Along the lymphatic system we also encounter the so-called lymphatic organs, deputed to the production and purification of the lymph (thymus, spleen and bone marrow).
Transparent in color, straw yellow or milky, depending on the case, the sap contains sugars, proteins, salts, lipids, amino acids, hormones, vitamins, white blood cells etc. Compared to blood, the lymph is particularly rich in lipids; in the article dedicated to the absorption of fats we have in fact recalled how, after intestinal absorption, the lipid molecules are poured into the lymphatic system in the form of particular lipoproteins called chylomicrons.
The larger lymphatic vessels are characterized by a succession of narrowings and dilations to which are associated true valvular insertions which, similar to those of the venous system, prevent the reflux of the lymph, forcing it to flow in one direction only; the wall of some of these vessels also has contractile capacity. All these anatomical peculiarities are fundamental to allow the unidirectional passage of the lymph: from the interstitial fluid of the tissues towards the systemic circulation, even against gravity.
 | |
The sap derives directly from the blood and has a composition very similar to it, although it is richer in white blood cells and very poor in red ones. Circulating in the interstitial spaces (including, that is, between a cell and the other) it has the purpose of reabsorbing the plasma (liquid part of the blood) present in these areas. The very thin walls of the blood capillaries are in fact permeable to water and various substances; thanks to this permeability, the passage of oxygen and nutrients from the blood to the tissues that, for their part, pour carbon dioxide and waste products into the blood stream can occur. The sap represents an effective system through which the body collects liquids and waste material from the periphery to then convey it to the purification organs (liver, kidneys, lungs, lymph nodes). From this point of view, the function of the lymphatic system is therefore very similar to that of the venous circle.
When the precious lymphatic drainage system goes haywire it is possible to accumulate large quantities of liquids in the interstitial spaces due to the unfavorable osmotic gradient (passage of water from the solution with a lower concentration to that of higher concentration, ie from the blood to the interstitial spaces). This condition is called edema and, as mentioned, is the typical consequence of prolonged immobilization. In addition to inadequate lymphatic drainage, edema can be caused by an increase in capillary filtration with respect to resorption; this condition is typical of certain diseases such as heart failure and protein calorie malnutrition (kwashiorkor).
| LYMPHATIC SYSTEM FUNCTIONS |
| - return the liquid and the proteins filtered by the blood capillaries into circulation |
| - transfer the absorbed fats to the small intestine in the systemic circulation |
- capture and destroy pathogens foreign to the organism, producing and transforming the cells assigned to their neutralization |
To keep your lymphatic system healthy, it is very important to carry out regular physical activity, so as to favor the action of the "muscle pump". When this healthy habit is associated with a balanced diet, the immune defenses maximize their effectiveness, thus preventing the lymphatic system from going haywire for too much work. There are also special massage techniques that help the lymphatic system to more effectively drain the liquid that stagnates in the peripheral areas (manual lymph drainage).
