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An osteoclast (from Ancient Greek ὀστέον (osteon) 'bone' and κλαστός (clastos) 'broken') is a type of bone cell that breaks down bone tissue.This function is critical in the maintenance, repair, and remodeling of bones of the vertebral skeleton.
The osteoclast then induces an infolding of its cell membrane and secretes collagenase and other enzymes important in the resorption process. High levels of calcium , magnesium , phosphate and products of collagen will be released into the extracellular fluid as the osteoclasts tunnel into the mineralized bone.
Osteoclasts break down bone tissue, and along with osteoblasts and osteocytes form the structural components of bone. In the hollow within bones are many other cell types of the bone marrow . Components that are essential for osteoblast bone formation include mesenchymal stem cells (osteoblast precursor) and blood vessels that supply oxygen and ...
Osteoclasts were discovered in 1873. [3] However, it was not until the development of the organ culture in the 1970s that their origin and function could be deduced. Although there was a consensus early on about the physiological function of osteoclasts, theories on their origins were heavily debated.
Osteoclasts mature and/or migrate to discrete bone surfaces. Upon arrival, active enzymes, such as tartrate-resistant acid phosphatase , are secreted against the mineral substrate. [ citation needed ] The reabsorption of bone by osteoclasts also plays a role in calcium homeostasis .
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).
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This protein, which is a member of the peptidase C1 protein family, is expressed predominantly in osteoclasts. Cathepsin K is a protease, which is defined by its high specificity for kinins, that is involved in bone resorption. The enzyme's ability to catabolize elastin, collagen, and gelatin allows it to break down bone and cartilage.