6. Name the primary and secondary lymphoid organs.
Lymphoid organs are the organs in which origin, maturation and proliferation of lymphocytes occur. Lymphoid organs are of two types i.e. primary lymphoid organs and secondary lymphoid organs. In primary lymphoid organs, the origin of lymphocytes occurs. These include bone marrow and thymus.
After maturation, lymphocytes migrate to a secondary lymphoid organ like spleen, lymph nodes, tonsils, peyer’s patches of small intestine and appendix. They provide the sites for interaction lymphocyte with antigens.