Immune System in the Body



Lymphoid organs

  • Lymphoid organs are those organs where the maturation and proliferation of lymphocytes takes place.


Types of lymphoid organs

There are two types of lymphoid organs: primary lymphoid organs and secondary lymphoid organs.

Primary lymphoid organ
1. It includes bone marrow and thymus.

Secondary lymphoid organ
1. It includes lymph nodes, spleen, tonsils, Peyer's patch and mucosal associated lymphoid tissues.


Functions of spleen

  • Macrophages present in the spleen engulf or phagocytize and destroy worn out blood cells, live or dead pathogens, cell debris etc.
  • In the embryonal stage, it produces RBCs.
  • In adult stage, spleen work as a blood bank.
  • It stores iron.
  • The size of spleen increases at the time of malaria because lymphocytes and lead RBC number increased in it at that time.


Peyer's patch

They are small, white lymph nodes which are found in the mucosa membrane of the small intestine.
They are also called intestinal tonsils.
They fight infection.