Which term is the cylindrical structural unit of bone?

• A. Canaliculi
• B. Haversian canal
• C. Osteon
• D. Viscerocranium

Answer: (C)

The cylindrical structural unit of bone is the osteon, also called the Haversian system. Each osteon is a roughly cylindrical column of concentric lamellae surrounding a central Haversian canal that contains blood vessels and nerves. Osteocytes sit in lacunae between the lamellae and communicate through tiny channels called canaliculi, which connect the lacunae and allow nutrients and signals to flow. This organized, repeating cylinder along the length of compact bone gives it strength and the ability to resist bending. The central Haversian canal is part of the osteon, not the whole unit by itself; canaliculi are the small connecting channels, and viscerocranium refers to facial bones—unrelated to the cylindrical unit. Hence, the correct term for the cylindrical structural unit is osteon.