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Osteoblasts are generally present on the outer layer of bone, just beneath the periosteum. Attachment of the osteoclast to the osteon begins the process. The osteoclast then induces an infolding of its cell membrane and secretes collagenase and other enzymes important in the resorption process.
Components that are essential for osteoblast bone formation include mesenchymal stem cells (osteoblast precursor) and blood vessels that supply oxygen and nutrients for bone formation. Bone is a highly vascular tissue, and active formation of blood vessel cells, also from mesenchymal stem cells, is essential to support the metabolic activity of ...
Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts. Both processes utilize cytokine (TGF-β, IGF) signalling.In osteology, bone remodeling or bone metabolism is a lifelong process where mature bone tissue is removed from the skeleton (a process called bone resorption) and new bone tissue is formed (a process called ossification or new bone formation).
The osteoblast then deposits calcium phosphate which is hardened by hydroxide and bicarbonate ions. The brand-new bone created by the osteoblast is called osteoid. [24] Once the osteoblast is finished working it is actually trapped inside the bone once it hardens. When the osteoblast becomes trapped, it becomes known as an osteocyte.
During bone formation, an osteoblast is left behind and buried in the bone matrix as an "osteoid osteocyte", which maintains contact with other osteoblasts through extended cellular processes. [9] Although recently it was shown that vascular smooth muscle cells drive osteocyte differentiation [ 10 ] , most aspects of osteocytogenesis remain ...
Eventually, all of the cells within the nidus develop into, and display the morphologic characteristics of, an osteoblast. Then the osteoblasts create an extracellular matrix containing Type-I collagen fibrils, which is osteoid. The osteoblasts, while lining the periphery of the nidus, continue to form osteoid in the center of the nidus.
The initiation of endochondral ossification starts by proliferation and condensation of mesenchymal cells in the area where the bone will eventually be formed. Subsequently, these mesenchymal progenitor cells differentiate into chondroblasts, which actively synthesize cartilage matrix components.
Via different signalling molecules and combinations the osteochondroprogenitor will differentiate into either osteoblasts or chondrocytes. Simplified diagram of MSCs, and their differentiation pathways into osteoblast and chodrocytic cell lineages. Data based on a 10.5-day-old mouse embryo. Included are the multiple factors for differentiation. [2]