Which statement best defines endochondral ossification?

• A. Formation of bone directly from connective tissue without cartilage.
• B. Bone development within a cartilage model.
• C. Bone resorption by osteoclasts.
• D. Hardening of bone due to calcium deposition.

Answer: (B)

Endochondral ossification is the process of bone development inside a cartilage template. A cartilage model forms first, and over time its cartilage is broken down and replaced by bone as blood vessels invade and osteoblasts lay down bone on the remnants of the cartilage. This pathway is what shapes and elongates most long bones in the body, enabling growth in length as the cartilage model is progressively ossified.

This differs from bone forming directly from connective tissue without a cartilage stage, which is intramembranous ossification. It also isn’t about bone resorption by osteoclasts—that’s part of remodeling after bone is formed—and it isn’t simply calcium deposition leading to hardening, which describes mineralization rather than the organized replacement of cartilage with bone.