What is lymphatic system?

The lymphatic system is part of the circulatory system, comprising a network of lymphatic vessels that carry a clear fluid called lymph directionally towards the heart. Unlike the cardiovascular system the lymphatic system is not a closed system. The human circulatory system processes an average of 20 litres of blood per day through capillary filtration which removes plasma while leaving the blood cells. Roughly 17 litres of the filtered plasma get reabsorbed directly into the blood vessels, while the remaining 3 litres are left behind in the interstitial fluid. One of the main functions of the lymph system is to provide an accessory return route to the blood for the surplus 3 litres.The other main function is that of defense in the immune system. Lymph is very similar to blood plasma but contains lymphocytes and other white blood cells. It also contains waste products and debris of cells together with bacteria and protein. Associated organs composed of lymphoid tissue are the sites of lymphocyte production. Lymphocytes are concentrated in the lymph nodes. The spleen and the thymus are also lymphoid organs of the immune system. The tonsils are lymphoid organs that are also associated with the digestive system. Lymphoid tissues contain lymphocytes, and also contain other types of cells for support. The system also includes all the structures dedicated to the circulation and production of lymphocytes (the primary cellular component of lymph), which also includes the bone marrow, and the lymphoid tissue associated with the digestive system. read less

Lymphatic comes from the Latin word lymphaticus, meaning "connected to water," as lymph is clear. The lymphatic system, which is a subset of the circulatory system, has a number of functions, including the removal of interstitial fluid, the extracellular fluid that bathes most tissue. It also acts as a highway, transporting white blood cells to and from the lymph nodes into the bones, and antigen-presenting cells to the lymph nodes. read less