osteoblast

Examples of osteoblast in the following topics:

• Cell Types in Bones

  • As the secreted matrix surrounding the osteoblast calcifies, the osteoblast becomes trapped within it.
  • As is the case with osteoblasts, osteocytes lack mitotic activity.
  • When they differentiate, they develop into osteoblasts.
  • Osteoclasts continually break down old bone while osteoblasts continually form new bone.
  • Osteogenic cells are undifferentiated and develop into osteoblasts.

• Postnatal Bone Growth

  • Osteoblasts are mononucleate cells that are responsible for bone formation.
  • Osteoblasts produce a matrix of osteoid that is composed mainly of Type I collagen.
  • Osteoblasts are also responsible for the mineralization of this matrix.
  • Bone is a dynamic tissue that is constantly being reshaped by osteoblasts and osteoclasts.
  • Osteoblasts produce bone matrix and mineral, and osteoclasts break down the tissue.

• Embryonic and Fetal Bone Formation

  • When osteoblasts become trapped in the matrix that they secrete, they differentiate into osteocytes.
  • Osteoblasts continue to line up on the surface, which increases their size.
  • During the formation of bone spicules, cytoplasmic processes from osteoblasts interconnect.
  • The periosteum contains a layer of undifferentiated cells (osteoprogenitor cells) that later become osteoblasts.
  • The osteoblasts secrete osteoid against the shaft of the cartilage model (appositional growth).

• Bone Repair

  • Bone fractures are repaired through physiological processes in the periosteum via chrondroblasts and osteoblasts.
  • The periosteum is one source of precursor cells that develop into the chondroblasts and osteoblasts that are essential to heal bone.
  • The periosteal cells distal to (further from) the fracture gap develop into osteoblasts that form woven bone.
  • At this point, the mineralized matrix is penetrated by channels, each containing a microvessel and numerous osteoblasts.
  • The osteoblasts form new lamellar bone upon the recently exposed surface of the mineralized matrix.

• Development of the Skeleton

  • Ossification (or osteogenesis) is the process of laying down new bone material by cells called osteoblasts.
  • The peripheral portion is more fibrous, while, in the interior the cells or osteoblasts predominate.
  • Therefore, a network of bone is formed, the meshes of which contain the blood vessels and a delicate connective tissue crowded with osteoblasts.
  • The perichondrium becomes the periosteum that contains a layer of undifferentiated cells (osteoprogenitor cells) which later become osteoblasts.
  • These osteoblasts secrete osteoid against the shaft of the cartilage model (Appositional Growth).

• Bone Remodeling

  • Osteoblasts and osteoclasts, coupled together via paracrine cell signaling, are referred to as bone remodeling units.
  • Recent research has suggested that certain growth factors may work to locally alter bone formation by increasing osteoblast activity.
  • Fibroblast growth factor activates various cells of the bone marrow including osteoclasts and osteoblasts.
  • The release of these growth factors from the bone matrix could cause the proliferation of osteoblast precursors.
  • Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts.

• Bone Development

  • Ossification, or osteogenesis, is the process of bone formation by osteoblasts.
  • They then differentiate into osteoblasts at the ossification center.
  • Osteoblasts secrete the extracellular matrix and deposit calcium, which hardens the matrix.
  • Blood vessels invade the cavities, while osteoblasts and osteoclasts modify the calcified cartilage matrix into spongy bone.
  • Secondary ossification centers form in the epiphyses as blood vessels and osteoblasts enter these areas and convert hyaline cartilage into spongy bone.

• Bone Remodeling and Repair

  • It involves the processes of bone deposition or bone production done by osteoblasts and bone resorption done by osteoclasts, which break down old bone.
  • Though fragments of the blood clot may remain, fibroblasts and osteoblasts enter the area and begin to reform bone.
  • Fibroblasts produce collagen fibers that connect the broken bone ends, while osteoblasts start to form spongy bone.
  • This is similar to the endochondral formation of bone when cartilage becomes ossified; osteoblasts, osteoclasts, and bone matrix are present.
  • Bone remodeling: The bony callus is then remodelled by osteoclasts and osteoblasts, with excess material on the exterior of the bone and within the medullary cavity being removed.

• Stages of Bone Development

  • This occurs with the synchronized action of osteoclasts and osteoblasts, cells that resorb and deposit bone, respectively.
  • Osteoblasts and osteoclasts, coupled together via paracrine cell signalling, are referred to as bone remodeling unit.
  • Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts.

• Bone Scans

  • A bone scan picks up excessive osteoblastic activity, so it is useful for finding metastasized cancer tumors in the bone.
  • Nuclear bone scans are not to be confused with the completely different test often termed a "bone density scan," DEXA or DXA, which is a low exposure X-ray test measuring bone density to look for osteoporosis and other diseases where bones lose mass, without any bone re-building (osteoblastic) activity.
  • The nuclear medicine scan technique is sensitive to areas of unusual bone re-building activity because the radiopharmaceutical is taken up by osteoblast cells that build bone.
  • The technique, therefore, is sensitive to fractures and bone reaction to infections and bone tumors, including tumor metastases to bones, because all these pathologies trigger bone osteoblast activity.