What is the primary function of red bone marrow?

• A. Calcium storage
• B. Hematopoiesis
• C. Lipid synthesis
• D. Energy production

Answer: (B)

Hematopoiesis is the primary function of red bone marrow. It contains hematopoietic stem cells that differentiate into red blood cells, white blood cells, and platelets, providing the cells needed for oxygen transport, immunity, and clotting. This activity defines red marrow as the active site of blood cell formation. Calcium storage happens in the mineralized bone matrix, not in the marrow. Lipid synthesis occurs in adipose tissue and other tissues, not as the marrow’s main role. Energy production is carried out by cellular respiration in the mitochondria of many cells, not a specialized function of red marrow. Yellow marrow stores fat and can revert to red marrow if blood cell production is needed, but under normal conditions the hematopoietic activity of red marrow is the defining function.