| Osteoclasts |
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Information AboutOsteoclasts |
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Osteoclasts lie in a small cavity called Howship's lacuna, formed from the digestion of the underlying bone. The '''sealing zone''' is the attachment of the osteoclast's Plasmalemma to the underlying Bone . The osteoclast releases Hydrogen Ion s ( H2O + CO2 → HCO3 - + H +) into the cavity, acidifying and dissolving the mineralized Bone Matrix into Ca2+ , H3PO4, H2CO3 and water. Hydrogen ions are pumped against a high concentration gradient by Proton Pump s, specifically a unique vacuolar- ATPase . This enzyme has been targeted in the prevention of Osteoporosis . In addition, several Hydrolytic Enzyme s are released to digest the organic components of the Matrix , such as Collagenase and Cathepsin K . These enzymes are released into the compartment by Lysosome s. The osteoclast has a ruffled border which enhances its surface area. Products of digestion of the bone matrix (a mineral called Hydroxyapatite ), include Calcium and Phosphate ions. These ions are absorbed into small Vesicle s (see Endocytosis ) which move across the cell and eventually get released into the Extracellular Fluid , thus increasing levels of the ions in the blood. Osteoclasts are regulated by several Hormones , including Parathyroid Hormone (PTH) from the Parathyroid gland, Calcitonin from the Thyroid gland, and Growth Factor Interleukin 6 (IL-6). This last hormone, IL-6 , is one of the factors in the disease Osteoporosis , which is an imbalance between bone reabsorption and bone formation. Osteoclastic activity is also the basis for straightening of the teeth with Dental Brace s. The pressure exerted on the Periodontal Ligament of the tooth (by the braces) causes osteoclasts to absorb the Alveolar Bone . Osteoblasts then relay the bone to coincide with less pressure on the tooth, thus manipulating of the orientation of the tooth. An osteoclast can also be an instrument used to fracture and reset bones (the origin is Greek ''osteon'':bone and ''klastos'':broken). To avoid confusion, the cell was originally termed osotoclast. When the surgical instrument went out of use, the cell became known by its present name. REFERENCES
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