Everything about Osteoblast totally explained
An
osteoblast (from the
Greek words for "
bone" and "germ" or embryonic) is a mononucleate
cell that's 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's constantly being reshaped by osteoblasts, which build bone, and
osteoclasts, which resorb bone.
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.
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.
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.
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.
Osteoblasts and osteocytes
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.
Further Information
Get more info on 'Osteoblast'.
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