Chapter 5 :The Skeleton Part A Lecture Notes. The Skeletal System ***Quiz 1 Info Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments.

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Chapter 5 :The Skeleton Part A Lecture Notes

Chapter 5 :The SkeletonPart A Lecture Notes

The Skeletal System ***Quiz 1 InfoParts of the skeletal systemBones (skeleton)JointsCartilagesLigamentsTwo subdivisions of the skeletonAxial skeletonAppendicular skeletonFunctions of BonesSupport the bodyProtect soft organsAllow movement due to attached skeletal musclesStore minerals and fatsBlood cell formationBones of the Human BodyThe adult skeleton has 206 bonesTwo basic types of bone tissueCompact boneHomogeneousSpongy boneSmall needle-like pieces of boneMany open spacesFigure 5.2b

Classification of Bones on the Basis of ShapeFigure 5.1

Classification of BonesLong bonesTypically longer than they are wideHave a shaft with heads at both endsContain mostly compact boneExample:FemurHumerusClassification of BonesFigure 5.1a

Classification of BonesShort bonesGenerally cube-shapeContain mostly spongy boneExample:CarpalsTarsalsClassification of BonesFigure 5.1b

Classification of BonesFlat bonesThin, flattened, and usually curvedTwo thin layers of compact bone surround a layer of spongy boneExample: SkullRibsSternumClassification of BonesFigure 5.1c

Classification of BonesIrregular bonesIrregular shapeDo not fit into other bone classification categoriesExample: Vertebrae Hip bonesClassification of BonesFigure 5.1d

Anatomy of a Long Bone **Quiz 2 infoDiaphysisShaftComposed of compact boneEpiphysis Ends of the boneComposed mostly of spongy boneAnatomy of a Long BoneFigure 5.2a

Anatomy of a Long BonePeriosteumOutside covering of the diaphysisFibrous connective tissue membraneSharpeys fibersSecure periosteum to underlying boneArteriesSupply bone cells with nutrientsAnatomy of a Long BoneFigure 5.2c

Anatomy of a Long BoneArticular cartilageCovers the external surface of the epiphysesMade of hyaline cartilageDecreases friction at joint surfacesAnatomy of a Long BoneEpiphyseal plateFlat plate of hyaline cartilage seen in young, growing boneEpiphyseal lineRemnant of the epiphyseal plateSeen in adult bonesAnatomy of a Long BoneFigure 5.2a

Anatomy of a Long BoneMedullary cavity Cavity inside of the shaftContains yellow marrow (mostly fat) in adultsContains red marrow (for blood cell formation) in infantsAnatomy of a Long Bone

Bone MarkingsSurface features of bonesSites of attachments for muscles, tendons, and ligamentsPassages for nerves and blood vesselsCategories of bone markingsProjections or processesgrow out from the bone surfaceDepressions or cavitiesindentationsBone MarkingsTable 5.1 (1 of 2)

Bone MarkingsTable 5.1 (2 of 2)

Microscopic Anatomy of BoneOsteon (Haversian system)A unit of bone containing central canal and matrix ringsCentral (Haversian) canalOpening in the center of an osteonCarries blood vessels and nervesPerforating (Volkmans) canalCanal perpendicular to the central canalCarries blood vessels and nervesMicroscopic Anatomy of BoneFigure 5.3a

Microscopic Anatomy of BoneLacunaeCavities containing bone cells (osteocytes)Arranged in concentric ringsLamellaeRings around the central canalSites of lacunaeMicroscopic Anatomy of BoneFigure 5.3bc

Microscopic Anatomy of BoneCanaliculi Tiny canalsRadiate from the central canal to lacunaeForm a transport system connecting all bone cells to a nutrient supplyMicroscopic Anatomy of BoneFigure 5.3b

Formation of the Human SkeletonIn embryos, the skeleton is primarily hyaline cartilageDuring development, much of this cartilage is replaced by boneCartilage remains in isolated areasBridge of the noseParts of ribsJointsBone Growth (Ossification)Epiphyseal plates allow for lengthwise growth of long bones during childhoodNew cartilage is continuously formedOlder cartilage becomes ossifiedCartilage is broken downEnclosed cartilage is digested away, opening up a medullary cavityBone replaces cartilage through the action of osteoblastsBone Growth (Ossification)Bones are remodeled and lengthened until growth stops

Growing bones must widen as they lengthen= appositional growthLong Bone Formation and Growth

Bone startingto replacecartilageEpiphysealplatecartilageArticularcartilageSpongyboneIn a childIn a fetusIn an embryoNew boneformingGrowthin bonewidthGrowthin bonelengthEpiphysealplate cartilageNew boneformingBloodvesselsHyalinecartilageNew center ofbone growthMedullarycavityBone collarHyalinecartilagemodel(a)Long Bone Formation and GrowthFigure 5.4a, step 1

Bone startingto replacecartilageIn an embryoBone collarHyalinecartilagemodel(a)Long Bone Formation and GrowthFigure 5.4a, step 2

Bone startingto replacecartilageIn a fetusIn an embryoGrowthin bonelengthBloodvesselsHyalinecartilageNew center ofbone growthMedullarycavityBone collarHyalinecartilagemodel(a)Long Bone Formation and GrowthFigure 5.4a, step 3

Bone startingto replacecartilageEpiphysealplatecartilageArticularcartilageSpongyboneIn a childIn a fetusIn an embryoNew boneformingGrowthin bonewidthGrowthin bonelengthEpiphysealplate cartilageNew boneformingBloodvesselsHyalinecartilageNew center ofbone growthMedullarycavityBone collarHyalinecartilagemodel(a)Long Bone Formation and GrowthFigure 5.4b

Bone Remodeling: Bones are remodeled in response to two factorsBlood calcium levelsPull of gravity and muscles on the skeleton

Types of Bone CellsOsteocytesmature bone cellsOsteoblastsbone-forming cellsOsteoclastsbone-destroying cellsBreak down bone matrix for remodeling and release of calcium in response to parathyroid hormoneBone remodeling is performed by both osteoblasts and osteoclasts

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