Lymphatic system

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The lymphatic system is a network of vessels carrying lymph, or tissue-cleansing fluid, from the tissues into the veins of the circulatory system.

The lymphatic system helps for absorbing nutrients from the small intestines. A large portion of digested fats are absorbed via the lymphatic capillaries. Like the blood circulatory system, the lymphatic system is composed of fine capillaries that lie adjacent to the blood vessels that merge into larger tributaries known as trunks, and then into larger vessels called ducts.

The thoracic and right lymphatic ducts empty into the venous system near the collarbones. Lymph is continuously passing through the walls of the capillaries. It transports nutrients to the cells and collects waste products. Most of the lymph returns to the venous capillaries; however about 10% enters the terminal lymphatic capillaries and returns to the blood through the lymphatic system. The fluid usually contains substances having large molecules (such as proteins and bacteria) that is too large for the venous capillaries.

Along the lymphatic network in certain areas of the body (neck, armpit, groin, abdomen, chest) are small reservoirs, the lymph nodes, which collect bacteria and other deleterious agents and act as a barrier against these substances getting into the bloodstream. In a diseased state the filled lymph nodes can become palpably swollen. Enlarged lymph nodes can be a warning sign of various kinds of cancer, including breast cancer and Hodgkin's disease.

In cases where a cancerous growth has developed, removal of lymph nodes may help to prevent its further spread. However, such a procedure also slows the flow of lymph and may thus render some of the body vulnerable to infection. Generally speaking when cancer reaches the lymph nodes, it can spread throughout the body rather quickly.