The central (Haversian) canal is a feature of which bone unit?

• A. Calcaneus
• B. Cancellous bone
• C. Osteon
• D. Endosteum

Answer: (C)

The central canal is a feature of the osteon, the basic functional unit of compact bone. An osteon is a cylindrical structure with a central Haversian canal that houses blood vessels and nerves. Concentric lamellae wrap around this canal, and osteocytes sit in lacunae between the lamellae, connected by tiny canaliculi that radiate toward the canal. This arrangement lets nutrients and signals travel efficiently to and from the cells embedded in the bone matrix. Cancellous bone, by contrast, is made of trabeculae and does not form the organized cylinders that contain a central canal, and the endosteum lines internal surfaces rather than defining a bone unit.