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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 ...
A giant cell (also known as a multinucleated giant cell, or multinucleate giant cell) is a mass formed by the union of several distinct cells (usually histiocytes), often forming a granuloma. [ 1 ] Although there is typically a focus on the pathological aspects of multinucleate giant cells (MGCs), they also play many important physiological roles.
The osteoclasts are multi-nucleated cells that contain numerous mitochondria and lysosomes. These are the cells responsible for the resorption of 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.
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 ...
RANK is the receptor for RANK-Ligand and part of the RANK/RANKL/OPG signaling pathway that regulates osteoclast differentiation and activation. It is associated with bone remodeling and repair, immune cell function, lymph node development, thermal regulation, and mammary gland development.
Osteoblasts and osteocytes are derived from osteoprogenitor cells, but osteoclasts are derived from the same cells that differentiate to form macrophages and monocytes. [21] Within the marrow of the bone there are also hematopoietic stem cells. These cells give rise to other cells, including white blood cells, red blood cells, and platelets. [22]
RANKL may also bind to osteoprotegerin, a protein secreted mainly by cells of the osteoblast lineage which is a potent inhibitor of osteoclast formation by preventing binding of RANKL to RANK. RANKL also has a function in the immune system, where it is expressed by T helper cells and is thought to be involved in dendritic cell maturation.
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).