Osteoclast And Osteoblast

Part I

Despite the characteristic mineralization, bone tissue is far from dead. On the contrary, is the site of intense cellular activity, so that each year about 10% of our bone mass is renewed through physiological mechanisms of neo-formation and resorption. This means that:

Every 10 years the skeleton is completely renewed. All this involves structural changes detectable only by microscopy and do not involve changes in the macroscopic shape (at least in adulthood ) (Kim and Vaccaro, 2006, pp 479-87). The bone cells are didactically divided into four categories: osteocytes, osteoblasts, osteoclasts and their precursors. It 'worth remembering, from the beginning, that:

osteoblasts are responsible for the formation of bone matrix

osteoclasts are responsible for the breakdown of bone matrix

There are three types of bone cells themselves:

Osteoblasts

Osteoblasts are cells that manufacture bone tissue .

They form globular or polyhedral, monostratificata; tend to juxtaposition to each other by covering small areas of bone matrix , forming the so-called front of mineralization. Osteoblasts synthesize the various components of tissue, and fibrous amorphous, participating in the formation of 'osteoid and regulation of the processes of mineralization of the same. The osteoid is given by a holder of collagen fibers aligned to form an organic matrix upon which bind idrossipatite crystals and other mineral components (Kim and Vaccaro, 2006, pp 479-87). The collagen fibrils are arranged on the basis of preferential lines of force, so as to give strength properties of bone to mechanical stress. In addition to type I collagen, which is assembled into fibrils in the extracellular space and acts as a support for the mineralization, osteoblasts produce proteins such as osteocalcin and osteonectina, who are performing in support of the deposition process calcified matrix.

It is believed that osteoblasts also play a role in the early stages of the process of resorption, through the development of protease -specific factors and activation of osteoclasts. Osteoblasts are cells of mesenchymal origin (the embryonic mesenchyme is the connective tissue that gives rise, at later stages of development, the adult connective tissue). (Kim and Vaccaro, 2006, pp 479-87)

Osteoclasts

Osteoclasts are large cells with diameters varying between 20 and 100 microns, with many nuclei, furniture and specialized in bone resorption. Thanks to the numerous microvilli, osteoclasts attach suction cups as a section of bone matrix, are generally given in small-called Howship lacunae. Here secrete acid and proteolytic enzymes , digesting both the collagen support by dissolving the inorganic matrix and minerals in it(Kim and Vaccaro, 2006, pp 479-87). The bone resorption by osteoclasts work plays an important role during the processes of regeneration and remodeling of bone tissue, but not only. These cells are indeed important to adjust the concentration of serum calcium and phosphorus .

Osteocytes

The secretion of osteoblasts occurs in a definite direction: initially biased towards the pre-existing bone surface, but at regular intervals is also addressed in other directions, thus osteoblasts move away from each other and remain trapped in the matrix in the process of mineralization . Once the secretory phase, the osteoblast "walled" substantially slows its ...