What are osteoclasts derived from?
Osteoclasts are multinucleated cells that derive from hematopoietic progenitors in the bone marrow which also give rise to monocytes in peripheral blood, and to the various types of tissue macrophages. Osteoclasts are formed by the fusion of precursor cells.
Is osteocyte a protein?
Some osteocyte proteins (e.g., interleukin-6 and RANKL) also have roles within the immune system. In the context of mechanical loading/unloading, the regulatory role of osteocytes is well understood.
Do osteoclasts secrete collagen?
Osteoclasts dissolve bone mineral by massive acid secretion and secrete specialized proteinases that degrade the organic matrix, mainly type I collagen, in this acidic milieu.
What stimulates osteoclast activity?
Osteoclastic activity is stimulated by cytokines such as IL-6 and RANK and inhibited by calcitonin.
What is the difference between an osteoblast and an osteoclast?
OSTEOCLASTS are large cells that dissolve the bone. They are found on the surface of the bone mineral next to the dissolving bone. OSTEOBLASTS are the cells that form new bone. They also come from the bone marrow and are related to structural cells.
Does osteoclast activity increase or decrease blood calcium?
When blood calcium levels increase due to parathyroid hormone, osteoclasts in bones break down the bone matrix and release the calcium into the blood. This means the activity of the unknown hormone must inhibit the activity of osteoclasts to decrease blood calcium levels.
What is the function of the osteoclasts?
Osteoclasts form a seal around a resorption area by binding their integrins with a bone protein, vitronectin. The ruffled border incorporates a vacuolar-type H + pump that acidifies the extracellular area beneath the osteoclast. Lysosomal proteases and acid phosphatases are released by the osteoclast to break down the organic matrix.
How many nuclei are in a osteoclast?
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.
Are osteoclasts acidic or alkaline positive?
Osteoclasts are strongly acid-phosphatase-positive. 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.
What is the mechanism of osteoclastic resorption of bone?
Mechanism of osteoclastic resorption of bone. Osteoclasts form a seal around a resorption area by binding their integrins with a bone protein, vitronectin. The ruffled border incorporates a vacuolar-type H + pump that acidifies the extracellular area beneath the osteoclast.