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Encyclopedia > Osteoblast
Osteoblast
Osteoblasts and osteoclasts on trabecula of lower jaw of calf embryo.
Part of the growing edge of the developing parietal bone of a fetal cat.
Gray's subject #18 87
MeSH Osteoblasts
Dorlands/Elsevier o_08/12600120

An osteoblast (from the Greek words for "bone" and "germ" or embryonic) is a mononucleate cell that is responsible for bone formation. Osteoblasts produce osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix. Bone is a dynamic tissue that is constantly being reshaped by osteoblasts, which build bone, and osteoclasts, which resorb bone. Image File history File links Gray81. ... Image File history File links No higher resolution available. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo. ... This article is about the skeletal organs. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Osteoid is a protein mixture which is secreted by osteoblasts. ... Tropocollagen triple helix. ... Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissue In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ...

Contents

Osteogenesis

Osteoblasts arise from osteoprogenitor cells located in the periosteum and the bone marrow. Osteoprogenitors are immature progenitor cells that express the master regulatory transcription factor Cbfa1/Runx2. The periosteum is an envelope of fibrous connective tissue that is wrapped around the bone in all places except at joints (which are protected by cartilage). ... This article does not cite any references or sources. ... The term progenitor cell is used in cell biology and developmental biology to refer to immature or undifferentiated cells, typically found in post-natal animals. ... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ... Cbfa1/Runx2 is key transcription factor associated with osteoblast differentiation. ...


Osteoprogenitors are induced to differentiate under the influence of growth factors, in particular the bone morphogenetic proteins (BMPs). Aside from BMPs, other growth factors including fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-β) may promote the division of osteoprogenitors and potentially increase osteogenesis. Growth factor is a protein that acts as a signaling molecule between cells (like cytokines and hormones) that attaches to specific receptors on the surface of a target cell and promotes differentiation and maturation of these cells. ... Bone morphogenetic proteins (BMPs) are growth factors belonging to the TGF-β (Transforming Growth Factor-beta) super family with a strong ability to induce new bone and/or cartilage formation. ... This article or section is in need of attention from an expert on the subject. ... Transforming growth factor (TGF) is one of many characterized growth factors that exist in nature. ...


Once osteoprogenitors start to differentiate into osteoblasts, they begin to express a range of genetic markers including Osterix, Col1, ALP, osteocalcin, osteopontin, and osteonectin. Although the term osteoblast implies an immature cell type, osteoblasts are in fact the mature bone cells entirely responsible for generating bone tissue in animals and humans. Tropocollagen triple helix. ... Ball and stick model of alkaline phosphatase Alkaline phosphatase (ALP) (EC 3. ... Osteocalcin is a protein found in bone and dentin; that plays a role in mineralization and calcium ion homeostasis ... Osteopontin is a glycoprotein first identified in 1986 in osteoblasts. ... Osteonectin is a glycoprotein in the bone that binds calcium. ...


Morphology and histological staining

The cytoplasm of osteoblasts appears to be basophilic via normal H&E stain due to presence of large amount of rough endoplasmic reticulum. A large Golgi apparatus is also present in the centre. The nucleus is spherical and large. Osteoblasts can be stained for type 1 collagen or for the production of alkaline phosphatase. The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Ball and stick model of alkaline phosphatase Alkaline phosphatase (ALP) (EC 3. ...


Osteoblasts and osteocytes

Main article: osteocyte
Osteoblasts in developing bone

Osteoblasts that become trapped in the bone matrix become osteocytes. They cease to generate osteoid and mineralized matrix, and instead act in a paracrine manner on active osteoblasts. They are believed to act in a mechanosensory manner. An osteocyte, a star-shaped cell, is the most abundant cell found in bone. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2816 × 2112 pixels, file size: 2. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2816 × 2112 pixels, file size: 2. ... An osteocyte, a star-shaped cell, is the most abundant cell found in bone. ...


External links


  Results from FactBites:
 
Osteoblast definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms (110 words)
It does so by producing a matrix that then becomes mineralized.
Bone mass is maintained by a balance between the activity of osteoblasts that form bone and other cells called osteoclasts that break it down.
MedicineNet does not provide medical advice, diagnosis or treatment.
  More results at FactBites »

 
 

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