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Lymphatic System



The lymphatic system is a network of specialized organs, lymphatic vessels, and lymph nodes. It is responsible for the body's immune response and returning excess interstitial fluid to the bloodstream. It circulates lymph—a colorless fluid that contains nutrients and lymphocytes. Lymphocytes are white blood cells that find and attack pathogens. B cells, lymphocytes produced in the red bone marrow, neutralize pathogens by coating them in antibodies. T cells, lymphocytes that mature in the thymus, destroy infected body cells. Other major organs in the lymphatic system are the spleen, which filters lymph; the tonsils, which trap pathogens early in the digestive and respiratory tracts; the lacteals, which absorb fats in the small intestine; and the lymph nodes, which contain large concentrations of lymphocytes.

At A Glance

  • The lymphatic system is involved in immune response by circulating lymph, a fluid containing cells that fight infection.
  • The primary lymphoid organs are the thymus and red bone marrow, which produce lymphocytes, while the secondary lymphoid organs are the lymph nodes, spleen, tonsils.
  • Lymph is the colorless fluid that contains lymphocytes and nutrients.—circulates through the body via lymphatic vessels.
  • Lymphatic vessels circulate lymph throughout the body.