Final answer:
Compact bone is denser than spongy bone, forming the hard outer layer of bones, and can withstand compressive forces. Spongy bone is less dense, with a porous structure that supports weight distribution and houses bone marrow.
Step-by-step explanation:
Compact bone forms the dense outer layer of bones and is very hard and strong, with its functional unit being the osteon. This dense arrangement allows it to support and protect, able to withstand compressive forces. In contrast, spongy bone, also known as cancellous bone, is found at the center of bones and is lighter and less dense. It is characterized by an open, porous structure with web-like trabeculae, giving it a greater surface area but less total bone mass compared to compact bone. The porous nature of spongy bone supports shifts in weight distribution and contains bone marrow for the production of blood cells.