bone histology - weebly
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SkeletalSystem2MicroscopicAnatomy
Bio230Dr.CarlaSweet
Fig.6.5Copyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.
(b)Endosteum
Osteoprogenitorcell
Osteoblasts
Osteoclast
Bonematrix
Canaliculi
Endosteum
Osteocyteinlacuna
Osteoid
Perforatingfibers
Circumferentiallamellae
Periosteum
(a)Periosteum
Endosteum
PeriosteumCompactbone
Osteocyteinlacuna
Canaliculi
Cellularlayer
Fibrouslayer
(akaVolkmann’scanal)
MicroscopicAnatomyofbone.Osteon (akaHaversian system)=thestructuralunitofcompactbone.
Thisfigureshowsasingleosteondrawnasifpulledoutlikeatelescopetoillustratetheindividuallamallae.
Thispatternofalternatingthedirectionofcollagenfibersineachlamellaegivesboneaddedstrengthtoresisttorsionstresses.
MicroscopicAnatomy-anotherview
P
NerveConcentriclamellae Vein Artery
Canaliculi
Centralcanal
Osteon
Lacuna
CollagenfiberorientationCentralcanal
Osteon
Externalcircumferential
lamellae
Perforatingfibers
Periosteum
Fibrouslayer
Cellularlayer
Osteocyte
CanaliculiInterstitiallamellae
Trabeculaeofspongybone
Endosteum
Osteoclast
Parallellamellae
Osteocyteinlacuna
Osteoblastsalignedalongtrabeculaofnewbone
Canaliculiopeningatsurface
Perforatingcanals
Centralcanal
Trabeculae
Spaceforbonemarrow
Interstitiallamellae
Puttingitalltogether!
Histology:Groundbonepreparation:hard(compact)bonesampleisgrounddown.Thistypeofpreparationdestroyslivingcells,howeverdetailsoftheboneymatrixarepreserved.
OsteonsFoundonlyinCompactbone
Bone:Ossification/OsteogenesisBeforeweek8theskeletonofthehumanembryoconsistsonlyofhyalinecartilageandsomemembranesofmesenchyme (embryonictissue-stemcells).After8weeksbonetissuestartsappearingandreplacesmostcartilageandmesenchymal membraneintheskeleton.
2typesofBoneFormation:1. Intramembranous ossification:
Herebonedevelopsfrommesenchymal membrane.Thesearetheflatbonesoftheskullandtheclavicles(collarbone).Inthisprocessmesenchymal cellsclusteranddifferentiateintoosteoblastswhichstartmakingbonematrix.
2.Endochondral Ossification:“endo”=within”“chondra”=cartilage.Inthisprocessbonesdevelopashyalinecartilageisreplacedwithbone.Mostofourbonesareformedinthismanner.Endochondral ossificationstartsat8weeksinfetaldevelopmentandisnotcompletedtillearlyadulthood.
embryovs.fetus:Fetus:Theunbornoffspringfromtheendofthe8th weekafterconception(whenthemajorstructures
haveformed)untilbirth.Upuntiltheeighthweek,thedevelopingoffspringiscalledanembryo.
Copyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.
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EndochondralOssification
Deterioratingcartilagematrix Epiphyseal
capillaries
Epiphysealbloodvessel
Epiphysealplate
Articularcartilage
Spongybone
Medullarycavity
Compactbone
Periosteum
Epiphysealplatesossifyandformepiphyseallines.
Spongybone
Epiphysealline
Articularcartilage
Bonereplacescartilage,exceptthearticularcartilageandepiphysealplates.
Epiphysealplate
Perichondrium
Developingperiosteum
Fetalhyalinecartilagemodeldevelops. Cartilagecalcifies,
andaperiostealbonecollarformsarounddiaphysis.
Secondaryossificationcentersforminepiphyses.
Primaryossificationcenterformsinthediaphysis.
Calcifiedcartilage
Developingcompactbone
Medullarycavity
Secondaryossificationcenters
PrimaryossificationcenterBlood
vesselofperiostealbud
Periostealbonecollar
Hyalinecartilage
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Epiphysealline(remnantofepiphysealplate)
Endochondral Ossificationprocessbelow
Hyalinecartilagereplacedwithbone=Endochondral Ossification
Endochondral (insideCartilagemodel)BoneDevelopment
BesureyoucanIDeachofthesezonesonaslide
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restingproliferatinghypertrophycartilagecalcificationosification
The5zonesofEndochondral ossification:Hyalinecartilagereplacedbybone
noticethesizeofosteoblasts comparedtoosteoclasts.Whatdoosteoblasts do?Whatdoosteoclasts do?
intramembranous ossification : boneformswithinamesenchymal membrane
(Bone)