In addition to the cardiovascular (circulatory) system for blood circulation, the human body has another fluid flow system: the lymphatic system.
The lymphatic system comprises the set formed by the lymph, by lymphatic vessels and organs like lymph nodes, O spleen, O thymus and the palatine tonsils. Lymph is a clear, slightly yellowish liquid that slowly flows into our body through the lymphatic vessels. Part of the blood plasma continually leaks out of the capillaries, forming a liquid material between the cells of the body's various tissues - the intercellular or interstitial fluid.
Some of this intercellular fluid returns to the blood capillaries, carrying carbon dioxide and various debris. Another part - lymph - is collected by lymphatic capillaries. The lymphatic capillaries carry the lymph to larger vessels called lymphatic vessels. These vein-like vessels, in turn, flow into large veins where lymph is released, mixing with the blood.
Along its path, the lymphatic vessels pass through small globular organs called lymph nodes. The lymphatic vessels also pass through certain organs, such as the palatine tonsils (tonsils) and the spleen.
The lymphatic system does not have an organ equivalent to the heart. Lymph is therefore not pumped as in the case of blood. It still moves because muscle contractions compress the lymphatic vessels, causing lymph flow.
The lymphatic vessels have valves that prevent the backflow of lymph into it: thus it circulates through the lymphatic vessel in one direction only. The lymphatic system assists the cardiovascular system in removing waste, collecting and distributing fatty acids and glycerols absorbed in the small intestine and contributes to the body's defense by producing certain leukocytes, such as lymphocytes.