A. Magnified graphical representation of growth plate structure and morphology.
B. Enhanced cartoon of pre-hypertrophic and hypertrophic zones and primary spongiosa. Volumetric swelling due to increased synthesis of intracellular organelles and cytoplasmic water intake facilitates progressive hypertrophic chondrocyte enlargement. GH, IGF-1, Sox9, BMP2, HIF1α and FGFRs regulate chondrocyte hypertrophy, swelling, metabolism and apoptosis. Col10 is a marker for hypertrophic chondrocytes. Runx2 and Sox9 are required for transdifferentiation of hypertrophic chondrocytes into osteoblasts.