What term denotes the structural unit of compact bone?

• A. Haversian canal
• B. Periosteum
• C. Osteon
• D. Trabecula

Answer: (C)

The structural unit of compact bone is the osteon. An osteon is a cylindrical formation consisting of concentric lamellae that surround a central Haversian canal containing blood vessels and nerves. Osteocytes sit in tiny pockets called lacunae between the lamellae and connect through canaliculi, allowing nutrient and waste exchange. This organized, layered arrangement—with the central canal and nearby Volkmann’s canals that link neighboring osteons—gives compact bone its dense, strong, load-bearing character. Remember, the Haversian canal is part of an osteon, while the periosteum is the outer membrane covering the bone and trabeculae refer to the lattice in spongy bone, not the compact bone’s unit.