Which statement about red marrow is correct?

• A. Red marrow produces blood cells
• B. Red marrow stores fat
• C. Red marrow is more abundant in adult long bones than yellow marrow
• D. Red marrow is never found in the fetal period

Answer: (A)

Red marrow is the site where blood cells are formed. It contains hematopoietic tissue with stem cells that become red blood cells, white blood cells, and platelets, supporting all major blood cell lineages. In early life, red marrow is found in most bones to support rapid growth and high blood cell production. As you age, much of that red marrow is gradually replaced by yellow marrow, which stores fat, so red marrow becomes concentrated mainly in the axial skeleton and the ends of certain long bones rather than throughout the body. That’s why the statement red marrow produces blood cells is the best choice. The idea that red marrow stores fat describes yellow marrow, not red marrow. The claim that red marrow is more abundant in adult long bones than yellow marrow isn’t accurate given the aging pattern and distribution. And red marrow is present during fetal development, so saying it’s never found then isn’t correct.