Is the Medullary Cavity Present in Flat Bones?

The medullary cavity is not present in flat bones. Flat bones, such as those in the skull, ribs, and sternum, are primarily composed of two layers of compact bone with a layer of spongy bone in between. This structure is known as diploë. The medullary cavity, which is typically found in long bones, is a hollow region filled with bone marrow. In flat bones, the spongy bone layer serves a similar purpose by containing red bone marrow, but it does not form a distinct cavity like the medullary cavity in long bones.