What is contained within the medullary cavity?

The medullary cavity, located within the diaphysis of long bones, primarily contains yellow bone marrow in adults. Yellow bone marrow primarily stores fats and serves as an energy reserve. As a person ages, the red bone marrow that is present in the medullary cavity during childhood gradually turns into yellow bone marrow, which is why typically, in adults, the medullary cavity is predominantly composed of yellow marrow.

While red bone marrow does exist in some bones, particularly in areas like the pelvis, sternum, and in the proximal ends of long bones, the medullary cavity specifically refers to the region that is primarily yellow in adults. The other substances mentioned, such as articular cartilage, osteoblasts, and osteoclasts, are not components found within the medullary cavity itself. Articular cartilage covers the ends of bones at joints and is not found in the cavity, while osteoblasts and osteoclasts are bone cells involved in the formation and resorption of bone but do not reside in the medullary cavity; they are typically found in the bone tissue and surrounding areas.