Osteoblast

An osteoblast is a bone-forming cell that produces and mineralizes the organic matrix of bone. Some osteoblasts become embedded in the matrix and mature into osteocytes.

Osteoid: The unmineralized organic matrix secreted by bone-forming cells before mineral deposition. Osteoblasts secrete this collagen-rich scaffold before it hardens.
Mesenchymal stem cell: A multipotent stromal cell that can give rise to several connective-tissue cell types. Osteoblasts arise from mesenchymal progenitors through a bone-forming differentiation pathway.
Osteoclast: A multinucleated cell that resorbs bone by dissolving mineral and degrading matrix. Osteoclasts remove bone, opposing the matrix-building work of osteoblasts.
Bone remodeling: The lifelong process in which old bone is resorbed and replaced with new bone. Osteoblasts refill sites cleared during this coordinated cycle.
Bone mineralization: The deposition of mineral crystals in organic bone matrix, chiefly as hydroxyapatite. Osteoblasts initiate mineral deposition in the osteoid they produce.
Osteoprogenitor cell: A precursor cell that can differentiate into an osteoblast. This committed precursor is the immediate source of many osteoblasts.
Bone resorption: The breakdown of bone matrix and mineral, chiefly by osteoclasts. Resorption is the bone-removing counterpart to osteoblast-driven formation.
Fracture healing: The biological process that repairs a broken bone through inflammation, tissue formation, and remodeling. Osteoblasts produce new bone during the repair of a fracture.
Type I collagen: The main structural collagen in bone, forming fibers that provide tensile strength. Osteoblasts make the collagen fibers that give osteoid its framework.
RUNX2: A transcription factor required for the differentiation of osteoblast-lineage cells. RUNX2 activates the gene program that gives progenitors osteoblast identity.

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