The Lymphatic System (lat. Systema lymphaticum, also lymphatic system ) ( lymph = body water to Greek lymph: clear water ) is a part of the defense system (immune system) of vertebrates against pathogens, foreign particulate matter and pathologically altered body parts ( eg, tumor cells). It is divided into the lymphoid organs and the lymphatic system. The lymphatic system, in addition to the function in the immune system also has a meaning in the fluid transport and is closely related to the blood circulation.
The lymphoid organs are specialized organs for the differentiation and proliferation of lymphocytes. They are divided into primary and secondary lymphoid organs.
In the primary lymphoid organs, the differentiation of precursor cells into immunocompetent T- or B-lymphocytes is carried out:
- Bone marrow or bursa equivalent organ in mammals, bursa of Fabricius in birds
In the secondary lymphoid organs is caused by coincidence of antigens and immunocompetent lymphocytes a specific immune response:
- Lymphoid follicles
- Peyer's patches
- Tonsils ( " almond " )
- Lymph node
- Appendix (appendix of the cecum, often erroneously referred to in the Wurmfortsatzresektion as the " appendix " )
Spleen and bone marrow or assume additional functions for generation, storage and degradation of blood.
After the tissue composition, a distinction lymphoepithelial and lymphoreticular organs.
The lymphatic system begins as lymphatic capillaries in the periphery, they end "blind ". The lymphatic capillaries unite to form larger lymphatic vessels. In these lymph vessels to the lymph nodes are integrated as a filter stations. This lymphatic vessels serve as the diffusion of the lymphocytes. The lymphatic vessels unite to Lymphsammelstämmen, which open into the venous angle and thus into the superior vena cava and thus into the venous system. In contrast to the bloodstream so there is no " lymph ". In the lymph system about 2 liters of lymph fluid to be transported per day. The lymphatic transport of liquid is either passively by the movement of the limb and the compression of the lymphatic vessels or activated by the contractions of the single unordered lymphangion ( lymph hearts ). Lymphangion are Lymphgefäßabschnitte with thickened wall, limited by valve flaps, the smooth muscles around ten times contracts per minute. The lymph fluid then follows the least resistance in the direction of expanding to proximal lymphatic vessels. By a manual drainage and the intermittent compression may be excited and thus lymphangion contract about sixty times per minute.
Besides the importance in lymphocyte circulation, the lymphatic system plays an important role in the liquid removal from the various parts of the body. Parts of the blood occur in the capillary tissue as intercellular fluid ( tissue fluid ) from. This lymph is derived on the one hand through the veins, on the other part but as lymph through the lymph vessels. The transported via the lymphatic fluid eventually empties into the superior vena cava, which both body fluids ( lymph and blood) are reunited. About the lymphatic system also absorbed through the intestinal fats are transported in the bloodstream.