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osteoclast

[os-tee-uh-klast] /ˈɒs ti əˌklæst/
noun
1.
Cell Biology. one of the large multinuclear cells in growing bone concerned with the absorption of osseous tissue, as in the formation of canals.
2.
Surgery. an instrument for effecting osteoclasis.
Origin
1870-1875
1870-75; osteo- + -clast < Greek klastós broken
Related forms
osteoclastic, adjective
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for osteoclasts

osteoclast

/ˈɒstɪəʊˌklæst/
noun
1.
a surgical instrument for fracturing bone
2.
a large multinuclear cell formed in bone marrow that is associated with the normal absorption of bone
Derived Forms
osteoclastic, adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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osteoclasts in Medicine

osteoclast os·te·o·clast (ŏs'tē-ə-klāst')
n.

  1. A large multinucleate cell found in growing bone that resorbs bony tissue, as in the formation of canals and cavities. Also called osteophage.

  2. An instrument used in surgical osteoclasis.


os'te·o·clas'tic adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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osteoclasts in Science
osteoclast
  (ŏs'tē-ə-klāst')   
A specialized bone cell that absorbs bone, allowing for the deposition of new bone and maintenance of bone strength. Osteoclasts secrete enyzmes that dissolve the matrix of old bone tissue and acids that dissolve bone salts, which contain calcium and phosphorus. Except in growing bone, the rate of bone deposition and bone absorption equal each other so that bone mass remains constant. A mass of osteoclasts absorbs bone from the outer surfaces inward for about three weeks. The osteoclasts are then converted into osteoblasts that form new bone to fill in the cavities. See also osteoblast.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for osteoclasts

osteoclast

large multinucleated cell responsible for the dissolution and absorption of bone. Bone is a dynamic tissue that is continuously being broken down and restructured in response to such influences as structural stress and the body's requirement for calcium. The osteoclasts are the mediators of the continuous destruction of bone. Osteoclasts occupy small depressions on the bone's surface, called Howship lacunae; the lacunae are thought to be caused by erosion of the bone by the osteoclasts' enzymes. Osteoclasts are formed by the fusion of many cells derived from circulating monocytes in the blood. These in turn are derived from the bone marrow. Osteoclasts may have as many as 200 nuclei, although most have only 5 to 20. The side of the cell closest to the bone contains many small projections (microvilli) that extend into the bone's surface, forming a ruffled, or brush, border that is the cell's active region. Osteoclasts produce a number of enzymes, chief among them acid phosphatase, that dissolve both the organic collagen and the inorganic calcium and phosphorus of the bone. Mineralized bone is first broken into fragments; the osteoclast then engulfs the fragments and digests them within cytoplasmic vacuoles. Calcium and phosphorus liberated by the breakdown of the mineralized bone are released into the bloodstream. Unmineralized bone (osteoid) is protected against osteoclastic resorption.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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