Which bone tissue forms the dense outer layer of long bones and provides most cortical strength?

• A. Cancellous (trabecular) bone
• B. Cortical (compact) bone
• C. Subchondral bone
• D. Endosteal bone

Answer: (B)

The dense outer layer of long bones is cortical (compact) bone, and that is what provides most of the bone’s strength. This layer forms the hard, thick shell around the shaft, with tightly packed osteons and high mineral density that resist bending and weight-bearing stresses effectively. In contrast, the interior is cancellous (trabecular) bone, a lighter, porous lattice that supports metabolic functions and helps distribute loads, but doesn’t contribute as much to mechanical strength. Subchondral bone sits just beneath articular cartilage and can be either cortical or cancellous depending on the site, while endosteal bone lines the inner surface of the medullary cavity. So the outer dense shell—cortical bone—is the main source of cortical strength in long bones.