Which type of bone marrow is found in the medullary cavity of most adult long bones?

Which type of bone marrow is found in the medullary cavity of most adult long bones?

• A. Yellow bone marrow
• B. Red bone marrow
• C. Compact bone
• D. Spongy bone

Answer: (A)

In adults, the medullary cavity of the long bone shafts is filled mainly with yellow bone marrow, which is adipose tissue that stores fat. As the skeleton ages, the red marrow that actively produces blood cells is gradually replaced in the diaphyses by this fatty yellow marrow. Red marrow remains in areas where hematopoiesis is still needed, such as the ends of long bones (epiphyses) and in certain flat bones, but the cavity of most adult long bones houses yellow marrow.

In adults, the medullary cavity of the long bone shafts is filled mainly with yellow bone marrow, which is adipose tissue that stores fat. As the skeleton ages, the red marrow that actively produces blood cells is gradually replaced in the diaphyses by this fatty yellow marrow. Red marrow remains in areas where hematopoiesis is still needed, such as the ends of long bones (epiphyses) and in certain flat bones, but the cavity of most adult long bones houses yellow marrow.