What is the soft innermost layer of bone responsible for the production of red blood cells and platelets?

• A. Endosteum
• B. Periosteum
• C. Bone marrow
• D. Spongy bone

Answer: (C)

Blood cell production happens in bone marrow, the soft tissue inside bones. Hematopoietic stem cells in red bone marrow differentiate into red blood cells and platelets (along with white blood cells). In adults, red marrow is mainly in the axial skeleton and the ends of long bones, while yellow marrow stores fat and doesn’t produce blood cells. The endosteum lines the inner bone surface, the periosteum coats the outer surface, and spongy bone is the porous tissue that houses marrow. So, the soft innermost layer responsible for making red blood cells and platelets is bone marrow.