Blood Cell Lifespan: Why They Depend on the Bloodstream

Blood cells cannot survive independently; they require constant oxygen and nutrients from the bloodstream.

Lifespans

• Red blood cells (erythrocytes): ~120 days. Then removed by spleen/liver; components recycled (iron → transferrin, heme → bilirubin).
• Platelets (thrombocytes): ~7–10 days.
• White blood cells: Variable: neutrophils (hours–days in circulation), lymphocytes (years), monocytes (days→macrophages).

Dependence on Plasma

Plasma provides glucose, amino acids, lipids, hormones, electrolytes, and clotting factors. Without circulation, cells quickly deplete ATP, lose membrane integrity, and die.