Red blood cells (erythrocytes) live for approximately how long in the circulation under normal conditions?

• A. 365 days
• B. 30 days
• C. 120 days
• D. 24 hours

Answer: (C)

Verified step by step guidance

1. Understand that the lifespan of red blood cells (erythrocytes) refers to the average time they circulate in the bloodstream before being removed or broken down.
2. Recall that red blood cells do not have nuclei or organelles, which limits their ability to repair themselves, contributing to their finite lifespan.
3. Recognize that under normal physiological conditions, red blood cells typically survive for about 120 days in the circulation.
4. Note that this lifespan allows the body to maintain a balance between production in the bone marrow and removal by the spleen and liver.
5. Therefore, the correct answer is 120 days, as it reflects the average survival time of erythrocytes in healthy individuals.