Question

Read the following statements related to lymphoid organs and select the incorrect statement?

• A. Primary lymphoid organs provides micro-environment for the development of lymphocytes
• B. The spleen is the smallest lymphoid organ, where water-borne microorganisms are trapped
• C. Antigen trapped in lymph nodes helps in the activation of lymphocytes
• D. Lymphoid tissue located within lining of respiratory, digestive, and urogenital tracts are called MALT

Answer 1

The correct option is B The spleen is the smallest lymphoid organ, where water-borne microorganisms are trapped

The organs where origin and/or maturation and proliferation of lymphocytes occur are called lymphoid organs.

The spleen is a bean-shaped organ consisting mainly of lymphocytes and phagocytic cells. It is the largest lymphoid organ which is compartmentalised into red and white pulp.

The red pulp is the site where old and defective erythrocytes are destroyed and removed from the blood while white pulp is the region where blood-borne antigens are trapped and proper immune response is mounted against them. Hence option b is incorrect.

Figure : Structure of spleen

Primary lymphoid organs like bone marrow and thymus provide micro-environment for the development of lymphocytes. T-lymphocytes originated in the bone marrow require the thymus for maturation. B-lymphocytes mature in bone marrow. Hence option a is correct.


The lymph nodes are small solid structures located at different points along the lymphatic system. They serve to trap the micro-organisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response. Hence option c is correct.

Figure : Structure of lymph node

Lymphoid tissue located within the lining of respiratory, digestive, and urogenital tracts is called MALT (Mucosa-associated lymphoid tissue). Hence option d is correct.

Figure : MALT