Question 19 Each complex of central canal and matrix rings in compact bone is known as \( \begin{array}{l}\text { O perforating (Volkmann's) canal } \\ \text { O a canaliculus } \\ \text { an osteon (Haversian system) }\end{array} \)

The correct answer to the question is: **an osteon (Haversian system)** ### Explanation: - **O perforating (Volkmann's) canal**: These are channels in the bone that transmit blood vessels from the periosteum into the bone. They are not the central canal and matrix rings themselves. - **O a canaliculus**: These are small channels that connect lacunae (spaces containing osteocytes) to each other and to the central canal, but they do not represent the entire structure of the central canal and matrix rings. - **an osteon (Haversian system)**: This is the structural unit of compact bone, consisting of a central canal surrounded by concentric rings of matrix (lamellae). It is the correct term for the complex of the central canal and matrix rings in compact bone. Thus, the answer is **an osteon (Haversian system)**.