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Bone is broken down by osteoclasts, and rebuilt by osteoblasts, both of which communicate through cytokine (TGF-β, IGF) signalling. Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. [1]
The functional part of bone, the bone matrix, is entirely extracellular. The bone matrix consists of protein and mineral. The protein forms the organic matrix. It is synthesized and then the mineral is added. The vast majority of the organic matrix is collagen, which provides tensile strength. The matrix is mineralized by deposition of ...
In histology, osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue. [1] Osteoblasts begin the process of forming bone tissue by secreting the osteoid as several specific proteins. The osteoid and its adjacent bone cells have developed into new bone tissue when it becomes mineralized.
Bone matrix is 90 to 95% composed of elastic collagen fibers, also known as ossein, [5] and the remainder is ground substance. [6] The elasticity of collagen improves fracture resistance. [7] The matrix is hardened by the binding of inorganic mineral salt, calcium phosphate, in a chemical arrangement known as bone mineral, a form of calcium ...
Mineralization subsequently follows leading to formation of bone trabeculae (Endochondral bone formation). [ 11 ] Light micrograph of undecalcified epiphyseal plate showing endochondral ossification: healthy chondrocytes (top) become degenerating ones (bottom), characteristically displaying a calcified extracellular matrix .
The osteoclast releases hydrogen ions through the action of carbonic anhydrase (H 2 O + CO 2 → HCO 3 − + H +) through the ruffled border into the resorptive cavity, acidifying and aiding dissolution of the mineralized bone matrix into Ca 2+, H 3 PO 4, H 2 CO 3, water and other substances. Dysfunction of the carbonic anhydrase has been ...
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 ...
In bone, mineralization starts from a heterogeneous solution having calcium and phosphate ions. The mineral nucleates, inside the hole area of the collagen fibrils, as thin layers of calcium phosphate, which then grow to occupy the maximum space available there. The mechanisms of mineral deposition within the organic portion of the bone are ...