Lymphoid Organs & Blood Cell Production — NEET Biology
✅ Asked in NEET 2024The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. The thymus is a lobed organ located near the heart and beneath the breastbone. The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size. Both bone-marrow and thymus provide micro-environments for the development and maturation of T- lymphocytes. The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne micro-organisms. Spleen also has a large reservoir of erythrocytes. The lymph nodes are small solid structures located at different points along the lymphatic system. Lymph nodes 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.
NTA tests students' understanding that bone marrow is the primary site of ALL blood cell production (including lymphocytes), while thymus and bone marrow together provide the microenvironment for T-lymphocyte maturation. Students often confuse which organs produce vs. mature lymphocytes, or think thymus produces blood cells (it doesn't—it only matures T cells). The key mistake is forgetting that thymus shrinks after puberty, making its role limited in adults. Remember: bone marrow = production site for all blood cells; thymus = maturation site for T cells (large in infants, shrinks with age); spleen and lymph nodes = filtration and immune activation sites. This concept directly links immunity to organ function.
Given below are two statements : Statement I : Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. Statement II : Both bone marrow and thymus provide micro environments for the development and maturation of T-lymphocytes. In the light of above statements, choose the most appropriate answer from the options given below (NEET 2024)
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