Interstitial growth requires presence of what to maintain constant thickness of the epiphyseal plate?

• A. Epiphyseal cartilage
• B. Osteoclasts
• C. Endosteum
• D. Periosteum

Answer: (A)

Interstitial growth happens in the growth plate, which is made of cartilage. To lengthen the bone while keeping that plate in place, new cartilage must continually form in the epiphyseal plate and then be gradually replaced by bone on the diaphyseal side. This cartilage layer is the tissue that enables the plate to persist and maintain its thickness during growth. If cartilage weren’t present in the growth plate, there wouldn’t be the cartilage reservoir needed for ongoing lengthening, and the plate would thin and eventually close. The other options—bone-resorbing cells and the inner and outer bone coverings—don’t provide the cartilage needed for this process, so they aren’t responsible for maintaining the plate’s thickness during interstitial growth.