Question

What is the role of lymphoid organs in our body?

Answer 1

Lymphoid organs are the organs where the maturation and proliferation of lymphocytes take place. The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies. Their roles are:

Primary lymphoid organs

(i) Bone marrow: The main lymphoid organ where all blood cells including lymphocytes are produced. B cells mature here. 

(ii) Thymus: The immature lymphocytes (thymocytes) migrate here and mature into T cells. Both bone marrow and thymus provide the microenvironment for the development and maturation of B and T cells.

Secondary lymphoid organs

(i) Lymph nodes: Trap the microorganisms or antigens which get into the lymph and tissue fluid; antigens trapped here activate the lymphocytes and cause the immune response. 

(ii) Spleen: A bean-shaped organ that acts as a filter of the blood by trapping blood-borne microorganisms; it contains lymphocytes and phagocytes and is a large reservoir of erythrocytes. 

(iii) MALT (mucosal-associated lymphoid tissue): Lymphoid tissue in the lining of the respiratory, digestive and urogenital tracts; it constitutes about 50% of the lymphoid tissue in the human body.

Thus lymphoid organs are the sites for the origin, maturation, proliferation and action of lymphocytes and hence play a central role in the immune responses of the body.