lecture 6 notess.odt - Functions of bone Support = structural framework attaches to muscles ligaments Protection = internal organs soft tissues Movement

lecture 6 notess.odt - Functions of bone Support =...

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Functions of boneSupport= structural framework; attaches to muscles & ligamentsProtection= internal organs & soft tissues• Movement = act as levers during skeletal muscle contraction• Mineral homeostasis = stores minerals & releases them (into blood)• Blood cell formation = “hematopoiesis”; done by red marrowTriglyceride storage= in yellow marrowBone structureDiaphysis= shaft of a long boneEpiphysis= proximal and distal ends of bone– Each end is covered by articular cartilageMetaphysis= between diaphysis & epiphysisEpiphyseal growth plateexists in growing bones – allows bones to lengthenEpiphyseal linereplaces plate when lengthening stopsPeriosteum= covers outer bone surface. Except when the articular cartialge is– Protects & nourishes bones, helps growthMedullary cavity= contains yellow marrowEndosteum= lines medullary cavityBone: extracellular matrix• Surrounds the cells in bone Strong. Yet flexible• Contains WATER, COLLAGEN, SALTSHydroxyapatite= abundant mineral in bone– Crystallizes & hardens (“calcification”)– Calcification requires collagen= crystals form around the fibersBone: cell types• Arise from mesoderm:Osteogenic cellsOsteoblastsOsteocytesOsteoclastsOsteogenic cells• Bone’s STEM CELLS• Located along periosteum & endosteum• Only bone cells that divide• They eventually → osteoblastsOsteoblasts• “bone-building cells”• Secrete collagen & build matrix• They eventually → osteocytesOsteocytes • Mature bone cells• Provide nutrient & waste exchange (with the blood)• Maintain bone metabolism
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Osteoclasts• Derived from fusion of many WBCs called monocytes• Located in the endosteum• Break down the bone matrixComapct bone• Strongest part of bone• Mainly located in diaphysis• Resists axial stress• Contains repeating units = osteonsCompact bone: osteonsLamellae= rings of bone matrixCentral canals= run longitudinally through bone:Bone vessels(supply nutrients, drain wastes)Lymphatic vessels(fluid drainage)Nerves(sensation)– These structure are also in theperforating canalsOsteons (cont.)Lacunae= spaces containing osteocytesCanaliculi
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