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An osteoclast is a large multinucleated cell and human osteoclasts on bone typically have four nuclei [5] and are 150–200 μm in diameter. When osteoclast-inducing cytokines are used to convert macrophages to osteoclasts, very large cells that may reach 100 μm in diameter occur. These may have dozens of nuclei, and typically express major ...
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.
Calcitonin lowers blood levels of calcium by inhibiting the resorption of bone by osteoclasts, and its secretion is increased proportionally with the concentration of calcium. [7] Parafollicular cells are also known to secrete in smaller quantities several neuroendocrine peptides such as serotonin, somatostatin or CGRP.
Osteoclasts are critical for the bone remodeling cycle which is achieved by the building of bone by osteoblasts, reabsorption by osteoclasts, and remodeling by osteoblasts. [10] Osteoclasts precursor cells and mature osteoclast require stimulation of CSF1R for survival.
The earliest reference to the brain occurs in the Edwin Smith Surgical Papyrus, written in the 17th century BC. The hieroglyph for brain, occurring eight times in this papyrus, describes the symptoms, diagnosis, and prognosis of two patients, wounded in the head, who had compound fractures of the skull. The assessments of the author (a ...
[16] [7] Sclerostin, the product of the SOST gene, is the first mediator of communication between osteocytes, bone forming osteoblasts and bone resorbing osteoclasts, critical for bone remodeling. [20] Only osteocytes express sclerostin, which acts in a paracrine fashion to inhibit bone formation. [20]
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 ...
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]