Which tissue within bones produces blood cells?

• A. Red bone marrow
• B. Yellow bone marrow
• C. Trabeculae
• D. Epiphysis

Answer: (A)

Blood cell production, or hematopoiesis, occurs in red bone marrow, a hematopoietic tissue found in the cavities of cancellous (spongy) bone. It houses the progenitors for red cells, white cells, and platelets and is richly supplied with blood vessels and supportive stromal cells, which together drive the formation and maturation of blood cells. Yellow marrow, in contrast, is largely fat and stores energy rather than producing blood cells under normal conditions. Trabeculae are the lattice framework of spongy bone that creates spaces for marrow, and epiphysis is the end region of a long bone—neither is the tissue that generates blood cells. Therefore, red bone marrow is the tissue responsible for producing blood cells.