Which organ filters old red blood cells from circulation?

Which organ filters old red blood cells from circulation?

• A. Liver
• B. Spleen
• C. Kidney
• D. Heart

Answer: (B)

Old red blood cells are filtered from circulation by the spleen. In the spleen’s red pulp, specialized macrophages recognize aging or damaged RBCs, engulfing and breaking them down. This process recycles iron from hemoglobin for reuse in new blood cells and converts the heme into bilirubin for disposal. The liver also helps with breakdown via its macrophages, but its primary roles are broader and not focused on removing aged RBCs. The kidneys filter plasma to form urine, and red blood cells are generally too large to pass into the filtrate, so they’re not filtered in the same way. The heart merely pumps blood and does not filter out old blood cells.

Old red blood cells are filtered from circulation by the spleen. In the spleen’s red pulp, specialized macrophages recognize aging or damaged RBCs, engulfing and breaking them down. This process recycles iron from hemoglobin for reuse in new blood cells and converts the heme into bilirubin for disposal. The liver also helps with breakdown via its macrophages, but its primary roles are broader and not focused on removing aged RBCs. The kidneys filter plasma to form urine, and red blood cells are generally too large to pass into the filtrate, so they’re not filtered in the same way. The heart merely pumps blood and does not filter out old blood cells.