Lymph is a component of blood plasma : that is, of the liquid portion of blood . This transparent fluid passes through the walls of the capillaries, advances through the interstitial space of the tissues and is loaded with substances produced by the cells before entering the lymphatic vessels.
Once in the lymphatic vessels, the lymph circulates and finally reaches ducts that end in the veins and is thus incorporated into the blood. Its passage through the lymphatic system is possible due to the movement of the extremities, the pulsation of arteries and muscle contractions. Unlike what happens in the circulatory system, there is no organ in charge of pumping (action carried out by the heart in the case of blood circulation).
It is important to note that lymph circulation is very slow, and this is due to the aforementioned absence of an organ that drives it. The venous system is where all the lymph flows, which passes through two fundamental ducts : the thoracic and the right lymphatic.
With a high amount of lipids and a low level of proteins , lymph contains leukocytes (white blood cells) and certain microorganisms that are filtered by the lymph nodes. It is estimated that a person has about two liters of lymph in their body.
In the body, lymph fulfills three major functions. On the one hand, it is responsible for the absorption of nutrients from the digestive system, which it provides to the subclavian veins. On the other hand, lymph collects and returns interstitial fluid to the bloodstream. Finally, it also focuses on defense against the action of certain pathogens.
When a lymphatic vessel is blocked, lymph accumulates in the obstructed region. This causes edema to occur: a swelling of a part of the body.
Interstitial fluid is also known as tissue fluid and is what is found in the interstitium, that is, in the space between cells . It is estimated that of our total body tissues, the interstitium occupies approximately one sixth. As mentioned above, lymph is responsible for transporting it to the blood.
Said from another perspective, interstitial fluid is continuously produced in the space between cells due to blood circulation. Its excess is directed towards the lymphatic capillaries , after which it returns to the venous system.
Regarding the fats that we consume through food, the lymph is responsible for transporting it. First, the epithelial cells of the intestinal wall called enterocytes absorb them and create complex particles called chylomicrons , loaded with triglycerides.
The chylomicrons then bind to lymph, which carries them into the bloodstream. This indicates the great importance of lymph in the process of assimilation of dietary fats. The one that originates in the intestine after a high-fat meal has a creamy consistency and is called chyle .
The immune response is the third of the lymph functions mentioned in a previous paragraph and takes place through a complex organization. On the one hand we have the lymph nodes (also known as lymph nodes , nodules or lymph nodes ) in which we find several cells of the immune system , particularly lymphocytes. The latter attack microorganisms until they are destroyed and defend the body from any infection caused by an external agent. The lymph nodes are crossed by lymphatic vessels.