All of the following organs are catagorised as secondary lymphoid organs, EXCEPT:
Major secondary lymphoid organs are spleen and lymph nodes. Other secondary lymphoid organs includes tonsils, appendix, peyers patches in the intestine and lymphoid aggregates spread throughout mucosal tissue. Mucosal lymphoid organs are termed as MALT, those in the gut are GALT, and those in bronchial tree are BALT. Thymus is not a secondary lymphoid organ, it is a primary lymphoid organ. Functions of secondary lymphoid organs are trapping and concentrating foreign substances, production of antibodies and induction of antigen specific lymphocytes. Functions of spleen are storage of red blood cells, production of blood cells before bih, production of antibodies by lymphocytes and plasma cells in the white pulp following contact with antigen and its subsequent transformation into antibody producing cells, filtration of blood by phagocytosis and destruction of worn out red blood cells with release of hemoglobin. Ref: Clinical Hematology: Theory and Procedures, Volume 936 By Mary Louise Turgeon 4th Edition Page 218 ; Immunology: A Sho Course By Richard Coico, Geoffrey Sunshine, 6th Edition, Page 20 ; Fundamentals Of Histology By G. P. Verma, Page 133 ; Immunology By M P Arora Page 33,39
Spleen
Thymus
Lymph nodes
Subepithelial collections of lymphocytes