OSTEOLOGY: BONE DEVELOPMENTfaculty.mtsac.edu/mpresch/35_lecture_files_unit_1/3 Anat 35 Bone... ·...
Transcript of OSTEOLOGY: BONE DEVELOPMENTfaculty.mtsac.edu/mpresch/35_lecture_files_unit_1/3 Anat 35 Bone... ·...
OSTEOLOGY:BONEDEVELOPMENT
HumanAnatomyUnit1
InAnatomyToday
GeneralAnatomyofLongandFlatBones• Composition– Compact(Dense)outside– Spongyinside
• Flatbones=diploe• Regionsoflongbone– Diaphysis– Epiphysis– Marrow(medullary)cavity– Epiphysealplatevs.epiphysealline(18-25years)– Periosteum
• Fibrouslayer• Osteogeniclayer(cellularlayer)• Sharpey’sfibers
– Nutrientforamina– Endosteum– Articularcartilage
GrossAnatomyofaLongBone
DevelopmentofBones• Ossification=osteogenesis– depositionofbonetissue– beginsatapprox 4weeksgestation– apparentatapprox 10weeks– bonetissuearisesasconnectivetissuefromembryonicmesenchyme
– Twotypes• Endochondral• Intramembranous
16weeksofdevelopment
EndochondralBoneFormation
• Builtfromahyalinecartilagemodel– Perichondriumpresent
• Ossificationresultsinspongybonefirstthentheboneisremodeledandanouterlayerofcompactboneforms
• 1o centerofossificationindiaphysis• 2o centersofossificationinepiphysis
EndochondralBoneFormation
EndochondralBoneFormation
IncreasingtheLengthofaDevelopingBone
• Growthinbothdirectionsatthemetaphysesorgrowthplates– Ontheshaftside:• Osteoblastsarecontinuouslyreplacingcartilagewithbone
– OntheEpiphysisside:• Newcartilageisbeingproducedatthesamerateofcartilagereplacementontheshaftside
• Growthinoppositedirectionscausesthebonetolengthen
IncreasingtheDiameterofaDevelopingBone
• Appositionalgrowthontheoutersurface• Osteoprogenitorcellsoftheinnerlayeroftheendosteumdifferentiateintoosteoblasts
• Matrixisdepositedtotheouter(periosteal)surface– Addslayersofcircumferentiallamellae
• Marrowcavityenlargesasbonediameterenlarges
IntramembranousBoneFormationDermalBoneFormation
• Ossificationoccursinthedeeperlayersofthedermis• Forms– Roofingbonesoftheskull,mandible,clavicle
• Bonetissuedepositedwithinembryonicorfibrousconnectivetissue
• Mesenchymal cellsdifferentiateintoosteoblasts• Spongybonemayberemodeledtoformmedullarycavitiesorcompactbone– Diploe:spongybonebetween2layersofcompactbone
• Processofbonerepairduetofractures
BoneRepair
IntramembranousBoneFormation