The process of bone formation from a cartilage template is called

• A. Intramembranous ossification
• B. Calcification
• C. Hematopoiesis
• D. Endochondral ossification

Answer: (D)

Endochondral ossification is the process by which bones form from a cartilage template. A hyaline cartilage model develops first, then chondrocytes within this cartilage die as the matrix calcifies and blood vessels invade. Osteoblasts arrive and lay down bone matrix, gradually replacing the cartilage with bone tissue. This pathway explains how most bones, especially long bones, grow in length. In contrast, intramembranous ossification forms bone directly from mesenchymal tissue without a cartilage stage, which is why it’s seen in flat bones like the skull and the clavicle. Calcification refers to mineral deposition, not the full bone-forming process, and hematopoiesis is the formation of blood cells in bone marrow.