UMD BSCI 201 - The Skeletal System - D3499649

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UMD BSCI 201 - The Skeletal System

School name University of Maryland, College Park

Course Bsci 201- Human Anatomy And Physiology I

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TheSkeletalSystemWednesday,October10,201212:21PMComposedof2organs:bones&cartilage(206namedbones)Classes of Bones (shape):-Long bone Diaphysis-longaxis/shaft,composedofdensebonetissuesurroundingthemedullarycavity(containsbonemarrow-redoryellow).a. Redmarrow-sourceofthebloodcells,inchildrenb. Yellowmarrow-doesnotproducebloodcells,inadultsDiaphysissurroundedbythePeriosteum:a. Fibrous(Outer)layer:Composedofdenseirregularconnectivetissue,bloodvesselsenterthecompactboneofdiaphysisthroughtheNutrientForamina b. Osteogenic(Inner)layer:Osteoblasts(formedincells)&Osteoclasts(boneresorbingcells/breakdown)NutrientForaminaintotheperforating(Volkmann's)canaltojointhecavityintheosteoncalledtheHaversioncanal.Periosteumussecuredtotheexternalsurfaceofthediaphysisbytoughcord-likestructurescalledHarpey'sFibers.Epiphysis-slightlyexpandedendsofthelongbones,composedofspongybonetissuewithathinplateofperiosteum-coveredcompactboneontheoutside.Spongyboneiscomposedoftrabeculae-->thesurfacesarecoveredbyconnectivetissuemembranecalledtheEndosteum.Bloodvesselsfromtheperforatinganal,extendintospacesbetweenthetrabeculaeofspongybone-->containredbonemarrowtoproducebloodcells.Child'slongbone1. Redbonemarrowinepiphysisanddiaphysis2. Epiphysealplates(composedofhyalinecartilageatthediaphyseal-epiphysialjunctions=metaphyses).Adult'slongbone1. Redbonemarrowonlypresentinspongyboneofepiphysis2. Epiphyseallines(remnantsofplates)-Short bone-Flat bone-Irregular boneTypes of Bone Tissue (texture):-Spongy-composedofTrabeculae(needle-likestructures)-Compact-composedofOsteons(concentricrings)*Bonetissuesurroundedbyconnectivetissue&infiltratedbybloodvesselsandnervefibersOssification(developmentofthebonyskeletonfromtheembryonicskeleton):-Prenatalossification-occursbeforebirtha. Intramembranousossification-Mesenchyme(secretesmembranecalledfibrousconnectivetissue,locatedintheskull&clavicles,thesecranialbonesandclaviclesderivedfromfibrousCTmembraneviaintramembranousossification)8cranialbones,2clavicles(Flatbones,membranebones)*Allmembranebonesareflatbonesb. Endochondralossification-Mesenchyme(chondroblastssecretehyalinecartilage-->bonetissue)Bonesformedviaendochondralossification-->allbonesexcept8cranial&2claviclesLong,short,irregular,andsomeflatbonesareformedLonghyalinecartilage-->longbones(hyalinecartilagestillpersistsinthearticularcartilageandepiphysealplates)*Afterendochondralossification:short,irregular,andsomeflatbones-->thehyalinecartilageiscompletelychangedintobonetissue-->Endosteum-coveredspongybonesurroundedbythinplatesofperiosteum-coveredcompactbone-Postnatalossification-ossificationafterbirtha. Longitudinalbonegrowth-possibleduetopresenceofepiphysealplates*Activezonesinepiphysealplates(Epiphysealplates-->Diaphysealplates):1. Growth zone -->Chondroblastsproliferate(increaseinnumberviamitosis),increaseinchondroblastswillresultinanincreaseofnewhyalinecartilagesecretedontotheepiphysealfaceoftheepiphysealplates2. Hypertrophic zone -->Chondroblastshavematuredintochondrocytesandthechondrocytesincreaseinsize(growthofthechondrocytesviahypertrophy),increaseddemandofnutrientsbytheenlargedchondrocytes3. Calcification zone -->Calciumphosphatesalt(crystal)movesintothesemisolidmatrixofthehyalinecartilage,solidmatrixwhichcutsoffnutrientstothechondrocytes,chondrocytesdie4. Ossification (osteogenic) zone --> Osteoblastsmigrateintothedeterioratinghyalinecartilagematrixtosecretenewbonetissueonthediaphysealfaceoftheepiphysealplates,epiphysealplatehasbeenshifted-->linearbonegrowth5. Resorption zone --> Osteoclastswillcauseslightresorptionofthenearlyformedbonetissuetolengthenthemedullarycavityinthediaphysis.b. Apparitionalbonegrowth-Osteoblasts(secrete)&Osteoclasts(resorb)HormonalControlofPostnatalbonegrowth:-GrowthHormone-->growth-promotingeffectofgrowthhormoneonlongitudinalbonegrowthisindirect,stimulatesthehepatocytestoproduceIGF's.IGF's-->bindtoIGFreceptorsonthechondroblaststostimulatetheirproliferation.Increaseinthenumberofchondroblasts-->increaseinnewhyalinecartilageaddedontheepiphysealfaceoftheepiphysealplate,stimulateossificationChildhood-->GigantismSexSteroidHormones:a. Males(Androgens)-Testosteroneb.

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