Which cells are responsible for forming new bone tissue?

• A. Osteoblast
• B. Osteoclast
• C. Osteocyte
• D. Chondrocyte

Answer: (A)

Forming new bone tissue is the job of osteoblasts. These cells originate from osteoprogenitor cells in the periosteum and endosteum and are the ones that synthesize and secrete the organic bone matrix, called osteoid, which is rich in collagen type I and other proteins. They also orchestrate mineral deposition, kicking off the crystallization of calcium phosphate to harden the matrix into bone. As they lay down matrix, some osteoblasts become embedded in the bone they create and mature into osteocytes, which reside in lacunae and help maintain bone tissue. In contrast, other cells have different roles: osteoclasts break down bone during remodeling, and chondrocytes produce cartilage, not bone.