Which zone features chondrocytes that enlarge and begin to calcify the surrounding matrix?

Which zone features chondrocytes that enlarge and begin to calcify the surrounding matrix?

• A. Resting (reserve) zone
• B. Proliferation zone
• C. Hypertrophy zone
• D. Calcification zone

Answer: (C)

Chondrocyte enlargement with initiation of matrix calcification happens in the hypertrophy zone. In this region, cartilage cells grow much larger than in the resting or proliferative zones, and their hypertrophy drives changes in the surrounding matrix, promoting its calcification. This prepares the tissue for later invasion by blood vessels and osteogenic cells that replace the calcified cartilage with bone. The other zones don’t combine both cell enlargement and the start of matrix calcification: the resting zone has quiet, inactive cells, the proliferation zone is about rapid cell division, and the calcification zone mainly shows further mineralization and chondrocyte death after the matrix is already calcified.

Chondrocyte enlargement with initiation of matrix calcification happens in the hypertrophy zone. In this region, cartilage cells grow much larger than in the resting or proliferative zones, and their hypertrophy drives changes in the surrounding matrix, promoting its calcification. This prepares the tissue for later invasion by blood vessels and osteogenic cells that replace the calcified cartilage with bone. The other zones don’t combine both cell enlargement and the start of matrix calcification: the resting zone has quiet, inactive cells, the proliferation zone is about rapid cell division, and the calcification zone mainly shows further mineralization and chondrocyte death after the matrix is already calcified.