Which one of the following organs is meant for filtration of blood and the reservoir of erythrocytes?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Spleen
The lymphoid organs are of two kinds. Primary lymphoid organs (bone marrow and thymus) are where lymphocytes are made and become mature. Secondary lymphoid organs (spleen, lymph nodes, tonsils and others) are where mature lymphocytes meet antigens and respond to them.
(1) Bone marrow — Incorrect. Bone marrow is the main lymphoid organ where all blood cells, including lymphocytes, are made.
(2) Thymus — Incorrect. The thymus lies near the heart, beneath the breastbone. T-lymphocytes develop and mature there.
(3) Spleen — Correct. The spleen is a large bean-shaped organ with lymphocytes and phagocytes. It acts as a filter of the blood by trapping microorganisms carried in the blood. It also holds a large reservoir of erythrocytes (red blood cells).
(4) Lymph nodes — Incorrect. Lymph nodes trap microorganisms and antigens in the lymph and tissue fluid, not in the blood.
NCERT Extract:
Lymphoid Organs – “… The 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.”