Life span of red blood cells is approximately how many days?

• A. 60 days
• B. 90 days
• C. 120 days
• D. 180 days

Answer: (C)

Red blood cells have a limited lifespan because they lack a nucleus and mitochondria, so they can’t repair membrane damage or synthesize new proteins. As they travel through the circulation, they experience wear and oxidative stress, becoming less flexible and more prone to rupture. The spleen acts as a quality control by filtering out these aged or damaged cells, clearing them from the bloodstream. Bone marrow continuously produces new erythrocytes to replace what is destroyed, maintaining a steady supply for oxygen transport. Taken together, this turnover results in an approximate lifespan of 120 days for a red blood cell.