What does the osteoblast do?

• A. Build bone
• B. Maintain bone
• C. Dissolve bone
• D. Store fat

Answer: (A)

Osteoblasts are responsible for building bone. They synthesize and secrete the osteoid, the organic matrix rich in collagen and other proteins, which then mineralizes with calcium phosphate to form mature bone. They originate from mesenchymal stem cells and line bone-forming surfaces; as the matrix mineralizes, some osteoblasts become embedded and turn into osteocytes, while others remain on the surface as active builders or become lining cells. This is different from osteoclasts, which dissolve bone during resorption, and from marrow adipocytes, which store fat. Osteocytes primarily maintain and regulate bone tissue, while osteoblasts are the cells that construct it.