Which organ acts as a blood reservoir and participates in defense and destruction of aged red blood cells?

• A. Lymph Node
• B. Tonsil
• C. Spleen
• D. Thymus

Answer: (C)

Blood storage and removal of aged red blood cells are functions of the spleen. In the red pulp, macrophages phagocytose old or damaged erythrocytes, which is a form of extravascular hemolysis, helping to recycle iron and hemoglobin. The white pulp provides immune defense against blood-borne pathogens, while the organ as a whole acts as a reservoir by holding a substantial volume of blood and platelets in its venous sinusoids. Lymph nodes, tonsils, and the thymus contribute to immune defense in other ways or contexts, but they do not serve as major sites for storing blood or destroying aging red cells.