The lifespan of a red blood cell is_______________?
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Answer: C. 120 days
Explanation
Mature red blood cells circulate in the bloodstream for an average lifespan of approximately 120 days. Throughout this period, erythrocytes endure continuous mechanical stress as they squeeze through narrow capillary networks. Aging red blood cells lose membrane flexibility and are ultimately phagocytosed by macrophages in the spleen and liver. Erythrocytes lack a nucleus and cellular organelles, which limits their ability to repair damaged structural proteins. The bone marrow must continuously produce millions of new red blood cells every second to replace senescent cells. Hemoglobin breakdown products are recycled by the body, with iron and amino acids reused for new erythropoiesis.
A lifespan of 12 days is far too short and does not reflect the normal physiological survival time of human erythrocytes. A lifespan of 90 days underestimates the standard 120-day circulation duration of healthy mature red blood cells. A duration of one month is incorrect because erythrocytes circulate for approximately four months before splenic removal.
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