Which term describes growth in width or thickness of bones?

• A. Appositional growth
• B. Interstitial growth
• C. Endochondral ossification
• D. Synarthrosis

Answer: (A)

Appositional growth is the process by which bone increases in width or thickness. It occurs at the outer surface of the bone, where osteoblasts in the periosteum lay down new bone tissue. As bone thickens, remodeling on the inner surface by osteoclasts helps keep the medullary cavity appropriately sized, maintaining strength without making the bone unnecessarily bulky. Interstitial growth, by contrast, lengthens bone by adding tissue at the growth plates inside cartilage that later ossifies. Endochondral ossification refers to bone formation from cartilage and underlies much of long-bone development, including length, but isn’t the term for widening. Synarthrosis is a still-movable joint type, not a growth process.