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The three main mechanisms by which osteoporosis develops are an inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive bone resorption, and inadequate formation of new bone during remodeling, likely due to mesenchymal stem cells biasing away from the osteoblast and toward the marrow adipocyte ...
Osteoporosis occurs when there is an imbalance between the bone resorption activities of osteoclasts and the bone formation activities of osteoblasts. [23] Osteoclast activity is also mediated by the interaction of two molecules produced by osteoblasts, namely osteoprotegerin and RANK ligand. These molecules also regulate differentiation of the ...
The cell body varies in size from 5–20 micrometers in diameter and contain 40–60 cell processes per cell, [4] with a cell to cell distance between 20–30 micrometers. [3] A mature osteocyte contains a single nucleus that is located toward the vascular side and has one or two nucleoli and a membrane. [ 5 ]
These are the cells responsible for the resorption of bone. 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 ...
Bone marrow adipocytes (BMAds) [9] originate from mesenchymal stem cell (MSC) progenitors that also give rise to osteoblasts, among other cell types. [10] Thus, it is thought that BMAT results from preferential MSC differentiation into the adipocyte, rather than osteoblast, lineage in the setting of osteoporosis. [11]
The calcitonin receptor is a G protein-coupled receptor localized to osteoclasts [20] as well kidney and brain cells. It is coupled to a G s α subunit, thus stimulating cAMP production by adenylate cyclase in target cells. It may also affect the ovaries in women and the testes in men. [citation needed]
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).
A bone growth factor is a growth factor that stimulates the growth of bone tissue. [1] [2]Known bone growth factors include insulin-like growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), transforming growth factor beta (TGF-β), fibroblast growth factors (FGFs), platelet-derived growth factor (PDGF), parathyroid hormone-related peptide (PTHrP), bone morphogenetic proteins (BMPs ...