Final answer:
The marrow in the medullary cavity of a long bone contains yellow marrow, while the spaces of spongy bone contain red marrow.
Step-by-step explanation:
The marrow in the medullary cavity of a long bone differs from the marrow in the spaces of spongy bone in terms of their location and composition. The medullary cavity, which lies in the diaphysis of a long bone, contains yellow marrow. Yellow marrow is primarily composed of fat cells and is responsible for storing fat. On the other hand, the spaces of spongy bone, which are found in the epiphyses of a long bone, contain red marrow. Red marrow is the site of blood cell production, including red blood cells, white blood cells, and platelets.