Statement I: The spleen is a large bean-shaped organ and acts as a filter of the blood by trapping blood-borne micro-organisms.
Statement II: 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.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both Statement I and Statement II are correct.
The thymus and the spleen are lymphoid organs. The thymus is a primary lymphoid organ where T-lymphocytes mature, and the spleen is a secondary lymphoid organ that works on the blood.
Statement I: The spleen is a large bean-shaped organ and acts as a filter of the blood by trapping blood-borne micro-organisms. — True. The spleen is a large bean-shaped organ that mainly contains lymphocytes and phagocytes. It filters the blood by holding back blood-borne micro-organisms, and it also keeps a large reservoir of erythrocytes.
Statement II: 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. — True. The thymus is a lobed organ near the heart, beneath the breastbone. It is largest at birth and becomes very small by puberty.
NCERT Extract:
Immune System in the Body – “… 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 microorganisms. Spleen also has a large reservoir of erythrocytes.”