What is the average physiological lifespan of a mature circulating human red blood cell (erythrocyte) in healthy adults?
Answer and explanation
Correct answer: A. 120 days
- Step 1: Mature erythrocytes lack nuclei and organelles, preventing self-repair of membrane proteins. Step 2. After approximately 120 days of circulation, aging red blood cells are engulfed and recycled by splenic macrophages. Answer: 120 days. Why not the others: Platelets circulate for 8-10 days; neutrophils circulate for hours to days; memory lymphocytes may survive for years.
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