Identify the structure at the arrow.

Identify the structure at the arrow.

• A. Lamellae of a Spongy Bone
• B. Central Canal of a Spongy Bone
• C. Lamellae of a Compact Bone
• D. Lamellae of a Trabeculae Bone

Answer: (C)

This item tests recognizing the osteon architecture in compact bone. The arrow points to the circular layers of mineralized matrix surrounding a central canal, which are the lamellae of a compact bone. In compact bone, the basic unit is the osteon, with concentric lamellae forming rings around a central (Haversian) canal that contains blood vessels and nerves. Osteocytes lie in lacunae between lamellae and communicate through canaliculi, maintaining bone tissue. In contrast, spongy bone is organized into trabeculae with irregularly arranged lamellae and no central canal, so the concentric-ring pattern around a single canal isn’t present there. Trabeculae lamellae are the lamellae within those thin plates, not the circular osteon lamellae surrounding a central canal. Therefore, the structure shown is lamellae of compact bone.

This item tests recognizing the osteon architecture in compact bone. The arrow points to the circular layers of mineralized matrix surrounding a central canal, which are the lamellae of a compact bone. In compact bone, the basic unit is the osteon, with concentric lamellae forming rings around a central (Haversian) canal that contains blood vessels and nerves. Osteocytes lie in lacunae between lamellae and communicate through canaliculi, maintaining bone tissue.

In contrast, spongy bone is organized into trabeculae with irregularly arranged lamellae and no central canal, so the concentric-ring pattern around a single canal isn’t present there. Trabeculae lamellae are the lamellae within those thin plates, not the circular osteon lamellae surrounding a central canal. Therefore, the structure shown is lamellae of compact bone.