What is the average lifespan of a human red blood cell?

The average lifespan of a human red blood cell is approximately 120 days. This is due to the unique structure and function of red blood cells, which are designed to efficiently transport oxygen from the lungs to various tissues in the body and then return carbon dioxide to the lungs for exhalation.

Red blood cells are produced in the bone marrow and enter circulation as fully mature cells. Over time, as they circulate throughout the body, they undergo wear and tear due to the mechanical stress of passing through the narrow capillaries and other vessels. When they become old or damaged, they are typically removed from circulation by the spleen and liver. The lifespan of around 120 days reflects a balance between sufficient time in the bloodstream to fulfill their oxygen-carrying role and the need for regular turnover to maintain healthy blood function.

Understanding this lifespan is crucial in contexts such as blood donation, anemia, and various medical conditions that affect red blood cell production and destruction.