Which option lists the layers of bone?

• A. Endosteum, compact bone, spongy bone, bone marrow
• B. Periosteum, compact bone, spongy bone, bone marrow
• C. Periosteum, cortical bone, spongy bone, marrow cavity
• D. Periosteum, cortex, trabeculae, bone marrow

Answer: (B)

From outside to inside, bone is organized in a protective outer layer, a dense outer shell, a light internal lattice, and a central marrow space. The outermost covering is the periosteum, a fibrous membrane that supplies nerves and blood vessels and helps with attachment of ligaments. Beneath that lies the compact bone, the dense shell that gives most of the bone’s strength. Inside the compact bone is the spongy bone, a porous network of trabeculae that reduces weight while still supporting stress. Within the interior space, the marrow cavity houses bone marrow, the site of blood cell production (red marrow) or fat storage (yellow marrow) depending on the area and age. This sequence—periosteum, compact bone, spongy bone, bone marrow—best matches the actual layering of bone. Other options mix in inner linings like endosteum or swap terms (marrow cavity vs bone marrow) that don’t represent the primary outer-to-inner layers.