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Osteocytes are simply osteoblasts trapped in the matrix that they secrete. They are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi, which are used for exchange of nutrients and waste through gap junctions .
The osteoblasts are also connected by gap junctions, small pores that connect osteoblasts, allowing the cells in one cohort to function as a unit. [16] The gap junctions also connect deeper layers of cells to the surface layer ( osteocytes when surrounded by 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 process.
The spaces the cell body of osteocytes occupy within the mineralized collagen type I matrix are known as lacunae, while the osteocyte cell processes occupy channels called canaliculi. The many processes of osteocytes reach out to meet osteoblasts, osteoclasts, bone lining cells, and other osteocytes probably for the purposes of communication. [26]
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 ...
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).
Osteocytes do not entirely fill up the canaliculi. The remaining space is known as the periosteocytic space, which is filled with periosteocytic fluid. This fluid contains substances too large to be transported through the gap junctions that connect the osteocytes. In cartilage, the lacunae and hence, the chondrocytes, are isolated from each ...
Osteoblasts, the bone-forming cells, secrete the organic components of bone matrix [osteoid] and then initiates its mineralization. As osteoblasts become surrounded by the bone matrix, they differentiate into osteocytes , which reside in the lacunae and maintain bone tissue.