Which organs phagocytize aging erythrocytes?

• A. Liver and spleen
• B. Kidneys and spleen
• C. Lungs and liver
• D. Bone marrow and spleen

Answer: (A)

Old red blood cells are cleared by macrophages in the reticuloendothelial system, especially in the spleen and liver. In the spleen’s red pulp, aging RBCs become less deformable and are engulfed by splenic macrophages, with iron recycled and heme processed into bilirubin. The liver contains Kupffer cells that also phagocytose senescent erythrocytes as they pass through the sinusoidal network, contributing to extravascular hemolysis. The kidneys and lungs aren’t the primary sites for removing aging RBCs—the kidneys filter plasma and excrete waste, while alveolar macrophages deal mainly with inhaled particles. The bone marrow is where RBCs are produced, not recycled. So the liver and spleen are the organs responsible for phagocytizing aging erythrocytes.