The central structural unit consisting of a central canal surrounded by concentric lamellae runs parallel to the long axis of the bone. What is this unit called?

The central structural unit consisting of a central canal surrounded by concentric lamellae runs parallel to the long axis of the bone. What is this unit called?

• A. Lamella
• B. Osteon
• C. Lacunae
• D. Canaliculi

Answer: (B)

This question tests understanding of the compact bone’s basic structural unit. The osteon, also known as the Haversian system, is the cylindrical unit that runs parallel to the bone’s long axis. At its center is the Haversian (central) canal that carries blood vessels and nerves. Surrounding this canal are multiple concentric lamellae, layers of mineralized matrix. Within these lamellae lie lacunae, spaces where osteocytes reside, and tiny channels called canaliculi connect the lacunae to each other and to the central canal, allowing nutrient and waste exchange. This organized cylinder arrangement provides strength along the length of the bone, resisting bending and compression. The other terms refer to parts of this structure (lamellae are the rings, lacunae are the cell chambers, canaliculi are the connecting channels), but the unit that fits the description is the osteon.

This question tests understanding of the compact bone’s basic structural unit. The osteon, also known as the Haversian system, is the cylindrical unit that runs parallel to the bone’s long axis. At its center is the Haversian (central) canal that carries blood vessels and nerves. Surrounding this canal are multiple concentric lamellae, layers of mineralized matrix. Within these lamellae lie lacunae, spaces where osteocytes reside, and tiny channels called canaliculi connect the lacunae to each other and to the central canal, allowing nutrient and waste exchange. This organized cylinder arrangement provides strength along the length of the bone, resisting bending and compression. The other terms refer to parts of this structure (lamellae are the rings, lacunae are the cell chambers, canaliculi are the connecting channels), but the unit that fits the description is the osteon.