What is the lineage of osteoclasts?
Osteoclasts are members of the monocyte/macrophage lineage and are formed by cellular fusions from their mononuclear precursors. Their differentiation is regulated by a number of other cells and their products, especially by RANKL and M-CSF.
What are osteoclasts descended from?
Osteoclasts are derived from monocyte fusion and have from about 2 to 12 nuclei per cell. They are intimately associated with the surface of bone and use a structure called a ruffled border to bind matrix adhesion proteins and produce resorption pits called Howship’s lacunae.
What are the parts of an osteoclast?
Osteoclasts lie in small cavities called Howship’s lacunae, formed from the digestion of the underlying bone. The sealing zone is the attachment of the osteoclast’s plasma membrane to the underlying bone. Sealing zones are bounded by belts of specialized adhesion structures called podosomes.
What is osteoblast lineage?
Osteoblast lineage cells are a group of cells that includes mesenchymal progenitors, preosteoblasts, osteoblasts (often called mature osteoblasts), bone-lining cells and osteocytes.
How does the osteoclast attach to the bone?
Osteoclasts are giant cells containing between 10 and 20 nuclei. They closely attach to the bone matrix by binding its surface integrins to a bone protein called vitronectin. This close apposition seals off an area of the bone beneath the osteoclast and allows the osteoclast to form a microenvironment that resorbs bone.
What kind of differentiation factor does an osteoclast need?
Diffferentiation to terminally differentiated osteoclasts requires RANKL or osteoclast differentiation factor. Osteoclasts are giant multinucleate cells with abundant pale-staining cytoplasm containing many fine azurophilic granules (Fig. 2.18B).
How does the osteoclast destroy the organic matrix?
The area of the osteoclast next to bone forms a “ruffled border” consisting of multiple infoldings of the osteoclast cell membrane. It secretes acid and proteases across the ruffled border, and these dissolve the mineral of bone and destroy the organic matrix (see Figure 9.8.4 ).
Which is a characteristic of an osteoclast cell?
Osteoclasts are giant multinucleate cells with abundant pale-staining cytoplasm containing many fine azurophilic granules (Fig. 2.18B). The individual nuclei within a single cell are small, round or oval, are uniform in size, and have a single prominent nucleolus. There is usually no overlap between adjacent nuclei within the same cell.