The lymphatic system is not really a separate system of the body. It is considered part of the circulatory system since it consists of ~lymph~, a moving fluid that comes from the ~blood~ and returns to the ~blood~ by way of the lymphatic vessels. ~Lymph~ carries some nutrients around the body, especially fat. It also distributes germ-fighting white cells. ~Lymph~ resembles ~plasma~, but is more diluted and contains only about 5% of |proteins| and 1% of salts and extractives. It is formed from bits of ~blood~ and other body liquids, called interstitial fluid or tissue fluid, that collect in the spaces between cells. Some of the interstitial fluid goes back into the body through the capillary membrane, but most enters the lymphatic |capillaries| to become ~lymph~. Along with this interstitial fluid, the ~lymph~ also picks up any particles that are too big to be absorbed through the capillary membrane. These include cell debris, fat globules, and tiny |protein| particles. The ~lymph~ then moves into the larger lymphatic vessels and through the |lymph nodes| and eventually enters the ~blood~ through the |veins| in the neck region. The lymphatic system is thus a secondary transport system. ~Lymph~ has no pump of its own. Its flow depends on pressure from the ~blood~ system and the massaging effect of the muscles.
