Which tissue is located at the center of bones and contains blood-forming cells?

• A. Cartilage
• B. Endosteum
• C. Bone Marrow
• D. Periosteum

Answer: (C)

The tissue that sits at the center of bones and contains blood-forming cells is bone marrow. It fills the internal cavities of bones, especially the medullary cavity and the spaces within spongy bone, and houses hematopoietic stem cells that produce red blood cells, white blood cells, and platelets—the process of hematopoiesis. There are two types: red marrow, which is actively involved in blood formation, and yellow marrow, which stores fat and is less active in blood production. In adults, red marrow is primarily found in the flat bones and the ends of long bones. The other tissues have different roles: cartilage provides cushioning at joints, endosteum lines the inner bone surfaces, and periosteum covers the outer bone surface.