What type of marrow is found in the medullary cavity of adults?

• A. Cartilage
• B. Red marrow
• C. Bone marrow
• D. Yellow marrow

Answer: (D)

The medullary cavity in adults is filled with yellow marrow, which is mainly adipose tissue that stores fat and serves as an energy reserve. As a person matures, red marrow (the tissue that makes blood cells) is largely replaced by yellow marrow inside the hollow center of most long bones. Red marrow persists mainly in the axial skeleton (like the skull, sternum, pelvis, vertebrae) and at the ends of some long bones where hematopoiesis continues. That’s why yellow marrow is the correct type for the medullary cavity in adults.