Final answer:
Old red blood cells are phagocytized by macrophages, and the hemoglobin from these cells is processed, with iron being recycled while bilirubin is excreted. Excessive hemoglobin release can overwhelm the kidneys.
Step-by-step explanation:
When old red blood cells (erythrocytes) rupture, a process known as hemolysis, they are removed from circulation by macrophages located primarily in the bone marrow, liver, and spleen. The components of the degraded erythrocytes' hemoglobin are processed. The breakdown of hemoglobin releases iron and biliverdin, which is converted to bilirubin. The iron is recycled and used in the production of new erythrocytes, while bilirubin is transported to the liver and then excreted as part of bile. The kidneys may be overwhelmed if too much hemoglobin is released into the bloodstream, potentially leading to kidney failure.