Question

Identify and compare two primary and two secondary lymphoid organs

Answer 1

Answer

Primary lymphoid organs

• The organs that serve as a site for development and maturation of lymphocytes are known as primary lymphoid organs.
• The primary lymphoid organs are :
  
  1) Red bone marrow : Red blood marrow contains hematopoietic stem cells.
  Lymphoid progenitor cells differentiate into lymphocytes.
  They further differentiate into T lymphocyte and B lymphocyte.
  
  
  2) Thymus gland : It is located on the posterior aspect of the sternum.
  T cells produced in red bone marrow completes their maturation in thymus gland.

Secondary lymphoid organs

• It provides the site for activation of mature lymphocytes.
• It provides lymphocytes with the medium to interact with the antigens.
• Secondary lymphoid organs are :
  
  1) Spleen : It is the site for production of immunoglobulin G.
  Dead red blood cells are removed from the circulation in the spleen.
  Blood is filtered in spleen as the lymphocytes residing in the spleen attack the pathogens and destroy them.
  
  
  
  2) Lymph node : Lymph nodes filter lymph.
  The pathogens and cellular debris in lymph are destroyed by the lymphocytes present in the lymph nodes.