Lymph nodes are secondary lymphoid organ | Class 12 Biology Chapter Human Health and Disease, Human Health and Disease NCERT Solutions

Lymphoid organs: immune system of human beings consists of lymphoid organs. The organs where the maturation and proliferation of lymphocytes occurs are called lymphoid organs. Lymphoid organs are of two types. These are:

Primary lymphoid organs: It includes bone marrow and thymus whereas B- and T- cell lymphocytes mature and acquire their antigen specific receptor or we can say antigen sensitive lymphocytes. After the maturation, the lymphocytes migrates to secondary lymphoid organs.

Secondary lymphoid organs: The organs are site of interaction where lymphocytes interact with the antigen and proliferate to become the effector cells. E.g. spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix.

Lymph nodes are small, solid structures located at the specific sites along the lymphatic system. They trap the microorganisms or other antigens that enter the lymph and tissue fluid. Antigens enters into the lymph nodes and tissue fluid, activate the lymphocytes and produces an immune response.