What is the lymphatic system?
Little known, but very important, the lymphatic system allows lymph to flow through the body’s tissues, draining every corner of the organism before flowing into the thoracic veins. Parallel to the cardiovascular system, the lymphatic system fights against excessive fluid accumulation in the tissues and is considered the body’s main defense. 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 noticeable and painful to the touch (hence the expression “having swollen lymph nodes”).
How it works
How the Lymphatic System Works
Similar to those of the cardiovascular system, the smallest lymphatic vessels, called capillaries, are found in the peripheral regions of the body and, joining together, give rise to increasingly larger vessels, until they flow into the thoracic duct. Unlike blood vessels, lymphatic capillaries are blind-ended and have an even thinner wall, formed by cells separated by large openings. The lymph transported by the thoracic duct, joining with that present in the vessels coming from the upper part of the body, flows at the level of the junction between the subclavian veins and the jugular vein.
At 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, responsible for the production and purification of lymph (thymus, spleen and bone marrow).
What is lymph and what is it made of?
Transparent, straw yellow or milky in color depending on the case, lymph contains sugars, proteins, salts, lipids, amino acids, hormones, vitamins, white blood cells, etc. Compared to blood, lymph is particularly rich in lipids; in the article dedicated to the absorption of fats we in fact recalled how, after intestinal absorption, lipid molecules are released 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 associated with actual valve insertions which, similarly to those of the venous system, prevent the reflux of lymph by forcing it to flow in only one direction; the wall of some of these vessels also has contractile capacity. All these anatomical peculiarities are fundamental to allow the unidirectional passage of lymph: from the interstitial fluid of the tissues towards the systemic circulation, even against gravity.
Functions of the lymphatic system
What is the lymphatic system for?
Lymph comes directly from blood and has a composition very similar to it, although it is richer in white blood cells and very poor in red blood cells. Circulating in the interstitial spaces (that is, between one cell and another) it has the purpose of reabsorbing the plasma (the 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 can occur, which, in turn, pour carbon dioxide and waste products into the bloodstream. Lymph represents an effective system through which the body collects liquids and waste material from the periphery and then conveys 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 circulation.
FUNCTIONS OF THE LYMPHATIC SYSTEM
- Return the liquid and proteins filtered by the blood capillaries to circulation
- Transfer fats absorbed at the level of the small intestine into the systemic circulation
- Capture and destroy pathogens foreign to the organism, producing and transforming the cells responsible for their neutralization
What happens if it doesn’t work well?
When the precious lymphatic drainage system goes haywire, significant quantities of fluids can accumulate in the interstitial spaces due to the unfavorable osmotic gradient (passage of water from the solution with a lower concentration to that with a higher concentration, i.e. 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 compared to reabsorption; this condition is typical of some diseases such as heart failure and protein-calorie malnutrition (kwashiorkor).
How to keep it healthy
To keep your lymphatic system healthy, it is very important to do regular physical activity, in order to promote the action of the “muscle pump”. When this healthy habit is combined with a balanced diet, the immune defenses maximize their effectiveness, thus preventing the lymphatic system from going haywire due to too much work. There are also specific massage techniques that help the lymphatic system to more effectively drain the fluid that stagnates in the peripheral areas (manual lymphatic drainage).