Dictionary > Lymphoid organ

Lymphoid organ

noun, plural: lymphoid organs
The organ of the lymphatic system, and carries out various immune functions
The lymphatic system is comprised of lymphatic vessels, lymph nodes, associated organs made up of lymphoid tissues (e.g. spleen, thymus, etc.), and lymph. It is primarily involved in the collection and returning of the fluid and proteins into the blood. Thus, it works closely to the cardiovascular system. Another main function of the lymphatic system is to provide immune defense.
The lymphoid organs of the lymphatic system are commonly divided into primary lymphoid organs and secondary lymphoid organs.
The primary lymphoid organs, also called central lymphoid organs, are the organs wherein immature lymphocytes develop. They are where proliferation and maturation of stem cells into immunocompetent cells occur. Examples of primary lymphoid organs include the thymus, the bone marrow, the fetal liver, and the avian bursa of Fabricius.
The secondary lymphoid organs, also called peripheral lymphoid organs, are those wherein cells of reticuloendothelial system carry out their functions. They are associated with the initiation of adaptive immune response. Examples of secondary lymphoid organs are spleen, lymph nodes, tonsils, appendix, and Peyer’s patches.
See also:

  • Reticular connective tissue
  • lymphatic system
  • thymus
  • bone marrow
  • bursa of Fabricius
  • spleen
  • lymph node
  • tonsil
  • appendix

Related term(s):

  • Primary lymphoid organ
  • Secondary lymphoid organ

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