osteoblast: Definition from Answers.com

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2008)

Osteoblast

Osteoblasts actively synthesizing osteoid that contains two osteocytes.
Latin	osteoblastus
Code	TH H2.00.03.7.00002

Osteoblasts (from the Greek words for "bone" and "germ" or embryonic) are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.^[1]

Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of this matrix. Zinc, copper and sodium are some of the minerals required in this process. Bone is a dynamic tissue that is constantly being reshaped by osteoblasts, which are in charge of production of matrix and mineral, and osteoclasts, which break down the tissue. The number of osteoblasts tends to decrease with age, affecting the balance of formation and resorption in the bone tissue,^[2] and potentially leading to osteoporosis.

Contents

1 Osteogenesis
2 Morphology and histological staining
3 Osteoblasts and osteocytes
4 See also
5 References
6 Further reading
7 External links

Osteogenesis

Osteoblasts arise from osteoprogenitor cells located in the deeper layer of 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).^[3] Aside from BMPs, other growth factors including fibroblast growth factor (FGF),^[3] platelet-derived growth factor (PDGF) and 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,^[4] BSP, M-CSF, ALP,^[5] osteocalcin,^[4] 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

Osteoblasts (pointer) lining bone and osteocytes within lacunae of bone

Hematoxylin and eosin staining reveals that the cytoplasm of osteoblasts is basophilic due to the presence of a large amount of rough endoplasmic reticulum. A large Golgi apparatus is also present in the centre. The nucleus is spherical and large. Active osteoblasts synthesize, and stain positively for, Type-I collagen and alkaline phosphatase.

Osteoblasts and osteocytes

Main article: osteocyte

Osteoblasts that become trapped in the bone matrix and remain isolated in lacunae become osteocytes. They cease to generate osteoid and mineralized matrix, and instead act in a paracrine manner on active osteoblasts. They are believed to respond to mechanosensory stimuli.^[6]^[7]

References

^ Salentijn, L. Biology of Mineralized Tissues: Cartilage and Bone, Columbia University College of Dental Medicine post-graduate dental lecture series, 2007
^ D’ippolito, Gianluca; Schiller, Paul C.; Ricordi, Camillo; Roos, Bernard A.; Howard, Guy A. (1999). "Age-Related Osteogenic Potential of Mesenchymal Stromal Stem Cells from Human Vertebral Bone Marrow". Journal of Bone and Mineral Research 14 (7): 1115–1122. doi:10.1359/jbmr.1999.14.7.1115. PMID 10404011.
^ ^a ^b Agata, H; Asahina, I; Yamazaki, Y; Uchida, M; Shinohara, Y; Honda, MJ; Kagami, H; Ueda, M (2007). "Effective bone engineering with periosteum-derived cells.". Journal of dental research 86 (1): 79–83. doi:10.1177/154405910708600113. PMID 17189468.
^ ^a ^b Ringe, J; Leinhase, I; Stich, S; Loch, A; Neumann, K; Haisch, A; Häupl, T; Manz, R et al. (2008). "Human mastoid periosteum-derived stem cells: promising candidates for skeletal tissue engineering.". Journal of tissue engineering and regenerative medicine 2 (2-3): 136–46. doi:10.1002/term.75. PMID 18383554.
^ Szulc, P; Garnero, P; Marchand, F; Duboeuf, F; Delmas, PD (2005). "Biochemical markers of bone formation reflect endosteal bone loss in elderly men--MINOS study.". Bone 36 (1): 13–21. doi:10.1016/j.bone.2004.09.004. PMID 15663998.
^ Ehrlich, P. J.; Lanyon, L. E. (2002). "Mechanical Strain and Bone Cell Function: A Review". Osteoporosis International 13 (9): 688–700. doi:10.1007/s001980200095. PMID 12195532.
^ You, J.; Yellowley, C. E.; Donahue, H. J.; Zhang, Y.; Chen, Q.; Jacobs, C. R. (2000). "Substrate Deformation Levels Associated With Routine Physical Activity Are Less Stimulatory to Bone Cells Relative to Loading-Induced Oscillatory Fluid Flow". Journal of Biomechanical Engineering 122 (4): 387–394. doi:10.1115/1.1287161. PMID 11036562.

External links

MedEd at Loyola Histo/practical/cartilage/hp9-49.html

Musculoskeletal system · connective tissue: bone and cartilage (TA A02.0, TH H3.01, GA 2.86–95)

Cartilage

perichondrium · fibrocartilage callus · metaphysis

cells (chondroblast · chondrocyte)

types (hyaline · elastic · fibrous)

Bone

Ossification	intramembranous · endochondral

Cycle	osteoblast · osteoid · osteocyte · osteoclast

Types	cancellous · cortical

Regions	subchondral bone · epiphysis · epiphyseal plate/metaphysis · diaphysis · Condyle · Epicondyle

Structure	osteon / Haversian system · Haversian canals · Volkmann's canals · connective tissue (endosteum · periosteum) · Sharpey's fibres · enthesis · lacunae · canaliculi · trabeculae · medullary cavity · bone marrow

Shapes	long · short · flat · irregular · sesamoid

M: BON/CAR

anat(c/f/k/f, u, t/p, l)/phys/devp/cell

noco/cong/tumr, sysi/epon, injr

proc, drug(M5)

Human cell types / list derived primarily from mesoderm

Paraxial

Cartilage/bone/
muscle
(MSC)

OCP	bone: Osteoblast → Osteocyte cartilage: Chondroblast → Chondrocyte

Myofibroblast	Fibroblast → Fibrocyte muscle: Myoblast → Myocyte · Myosatellite cell · Tendon cell · Cardiac muscle cell adipose: Lipoblast → Adipocyte

Digestive system

Interstitial cell of Cajal

Intermediate


Urinary system (RSC)	Angioblast → Endothelial cell · Mesangial cell (Intraglomerular, Extraglomerular) · Juxtaglomerular cell · Macula densa cell Stromal cell → Interstitial cell → Telocytes Simple epithelial cell → Podocyte · Kidney proximal tubule brush border cell

Reproductive system	Sertoli cell · Leydig cell · Granulosa cell · Peg cell · (spermatozoon and ovum are germ cells)

Lateral plate/
hemangioblast

Blood/immune
(HSC)

Lymphoid (CFU-L)	see lymphocytes

Myeloid (CFU-GEMM)	see myeloid cells

Circulatory system

Endothelial progenitor cell · Endothelial stem cell · Angioblast/Mesoangioblast · Pericyte · Mural cell

M: BON/CAR

anat(c/f/k/f, u, t/p, l)/phys/devp/cell

noco/cong/tumr, sysi/epon, injr

proc, drug(M5)

M: URI

anat/phys/devp/cell

noco/acba/cong/tumr, sysi/epon, urte

proc/itvp, drug (G4B), blte, urte

M: VAS

anat(a:h/u/t/a/l,v:h/u/t/a/l)/phys/devp/cell/prot

noco/syva/cong/lyvd/tumr, sysi/epon, injr

proc, drug(C2s+n/3/4/5/7/8/9)

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Donate to Wikimedia

Previous:	osteo+, ossify, ossein
Next:	osteocalcin, osteochondrodysplasia, osteochondromatosis

		American Heritage Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more
		Oxford Dictionary of Biochemistry. Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved. Read more
		Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more
		Mosby's Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more
		Random House Word Menu. © 2010 Write Brothers Inc. Word Menu is a registered trademark of the Estate of Stephen Glazier. Write Brothers Inc. All rights reserved. Read more
		Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Osteoblast. Read more

osteoblast

os·te·o·blast

osteoblast

osteoblastic

osteoblast

categories related to 'osteoblast'

Osteoblast

Osteogenesis

Morphology and histological staining

Osteoblasts and osteocytes

See also

References

Further reading

External links

	Is an osteoblast a cell? Read answer...
	Where is located the osteoblasts? Read answer...
	What are Osteoblasts and Osteoclasts? Read answer...

	What is he function of osteoblast?
	Where do osteoblasts migrate from?
	What are osteoblasts and osteroclasts?