Y khoa, y dược - The skeleton: Part B

7 The Skeleton: Part BVertebral ColumnTransmits weight of trunk to lower limbsSurrounds and protects spinal cordFlexible curved structure containing 26 irregular bones (vertebrae)Cervical vertebrae (7)—vertebrae of the neckThoracic vertebrae (12)—vertebrae of the thoracic cageLumbar vertebrae (5)—vertebra of the lower backSacrum—bone inferior to the lumbar vertebrae Coccyx—terminus of vertebral columnVertebral Column: CurvaturesIncrease the resilience and flexibility of the spineTwo posteriorly concave curvaturesCervical and lumbarTwo posteriorly convex curvaturesThoracic and sacralAbnormal spine curvaturesScoliosis (abnormal lateral curve)Kyphosis (hunchback)Lordosis (swayback)Figure 7.16Cervical curvature (concave)7 vertebrae, C1–C7Thoracic curvature(convex)12 vertebrae,T1–T12Lumbar curvature(concave)5 vertebrae, L1–L5Sacral curvature(convex)5 fused vertebrae sacrumCoccyx4 fused vertebraeAnterior viewRight lateral viewSpinousprocessTransverseprocessesIntervertebraldiscsIntervertebralforamenC1LigamentsAnterior and posterior longitudinal ligamentsFrom neck to sacrumLigamentum flavumConnects adjacent vertebraeShort ligamentsConnect each vertebra to those above and belowIntervertebral DiscsCushionlike pad composed of two partsNucleus pulposusInner gelatinous nucleus that gives the disc its elasticity and compressibilityAnulus fibrosusOuter collar composed of collagen and fibrocartilageFigure 7.17aSupraspinous ligamentIntervertebraldiscAnteriorlongitudinalligamentIntervertebral foramenPosterior longitudinalligamentAnulus fibrosusNucleus pulposusSectioned bodyof vertebraTransverse processSectionedspinous processLigamentum flavumInterspinousligamentInferior articular process Median section of three vertebrae, illustrating the composition of the discs and the ligamentsFigure 7.17cVertebral spinous process(posterior aspect of vertebra)Spinal nerve rootAnulus fibrosusof discHerniated portionof discNucleuspulposusof discSpinal cord(c) Superior view of a herniated intervertebral discTransverseprocessGeneral Structure of VertebraeBody or centrumAnterior weight-bearing regionVertebral archComposed of pedicles and laminae that, along with centrum, enclose vertebral foramenVertebral foraminaTogether make up vertebral canal for spinal cord Intervertebral foraminaLateral openings between adjacent vertebrae for spinal nerves General Structure of VertebraeSeven processes per vertebra:Spinous process—projects posteriorlyTransverse processes (2)—project laterallySuperior articular processes (2)—protrude superiorly inferiorly Inferior articular processes (2)—protrude inferiorlyPLAYAnimation: Rotatable Spine (horizontal)PLAYAnimation: Rotatable Spine (vertical)Figure 7.18PosteriorAnteriorLaminaSuperiorarticularprocessandfacetTransverseprocessPedicleSpinousprocessVertebralarchVertebralforamenBody(centrum)Cervical VertebraeC1 to C7: smallest, lightest vertebraeC3 to C7 share the following features Oval bodySpinous processes are bifid (except C7)Large, triangular vertebral foramenTransverse foramen in each transverse processTable 7.2Figure 7.20aDens of axisTransverse ligamentof atlasC1 (atlas)C2 (axis)Bifid spinousprocessTransverse processesC7 (vertebraprominens)(a) Cervical vertebraeC3Inferior articularprocessCervical VertebraeC1 (atlas) and C2 (axis) have unique features Atlas (C1)No body or spinous processConsists of anterior and posterior arches, and two lateral massesSuperior surfaces of lateral masses articulate with the occipital condylesFigure 7.19a-bAnterior archSuperiorarticularfacetTransverseforamen Posterior archPosteriortubercleAnteriortubercle PosteriorLateralmasses(a) Superior view of atlas (C1)C1Facet for densTransverseprocessLateralmassesTransverseforamen Posterior archPosteriortubercle PosteriorAnterior tubercleAnteriorarch (b) Inferior view of atlas (C1)InferiorarticularfacetCervical VertebraeAxis (C2)Dens projects superiorly into the anterior arch of the atlasDens is a pivot for the rotation of the atlas C2PosteriorDens(c) Superior view of axis (C2)InferiorarticularprocessBodySuperiorarticularfacetTransverseprocessPedicleLaminaSpinous processFigure 7.19cThoracic VertebraeT1 to T12All articulate with ribs at facets and demifacetsLong spinous processLocation of articular facets allows rotation of this area of spineTable 7.2Figure 7.20bTransverseprocessSpinousprocessSuperior articularprocessTransversecostal facet (fortubercle of rib)BodyIntervertebraldiscInferior costalfacet (for headof rib)Inferior articularprocess(b) Thoracic vertebraeLumbar VertebraeL1 to L5 Short, thick pedicles and laminaeFlat hatchet-shaped spinous processes Orientation of articular facets locks lumbar vertebrae together so as to prevent rotation Table 7.2Figure 7.20cSuperiorarticularprocessTransverseprocessSpinousprocessIntervertebraldiscBodyInferiorarticularprocess(c) Lumbar vertebraeSacrum and CoccyxSacrum5 fused vertebrae (S1–S5)Forms posterior wall of pelvisArticulates with L5 superiorly, and with auricular surfaces of the hip bones laterally CoccyxTailbone3–5 fused vertebraeArticulates superiorly with sacrumFigure 7.21aCoccyxAnteriorsacralforaminaApexSacral promontoryAlaBody offirstsacralvertebraTransverseridges (sites of vertebral fusion)(a) Anterior viewFigure 7.21bCoccyxPosteriorsacralforaminaMediansacralcrestSacralcanalSacralhiatusBodyFacet ofsuperiorarticular processLateralsacralcrestAuricularsurfaceAla(b) Posterior viewThoracic CageComposed of Thoracic vertebrae Sternum Ribs and their costal cartilagesFunctionsProtects vital organs of thoracic cavitySupports shoulder girdle and upper limbsProvides attachment sites for many muscles, including intercostal muscles used during breathing Sternum (Breastbone)Three fused bonesManubriumArticulates with clavicles and ribs 1 and 2BodyArticulates with costal cartilages of ribs 2 through 7Xiphoid processSite of muscle attachmentNot ossified until ~ age 40Ribs and Their Attachments12 pairsAll attach posteriorly to thoracic vertebraePairs 1 through 7True (vertebrosternal) ribsAttach directly to the sternum by individual costal cartilagesRibs and Their AttachmentsPairs 8 through12False ribsPairs 8–10 also called vertebrochondral ribsAttach indirectly to sternum by joining costal cartilage of rib above Pairs 11–12 also called vertebral (floating) ribsNo attachment to sternumFigure 7.22aIntercostal spacesTrueribs(1–7)Falseribs(8–12)Jugular notchClavicular notchManubriumSternal angleBodyXiphisternaljointXiphoidprocessL1VertebraFloating ribs (11, 12)(a) Skeleton of the thoracic cage, anterior viewSternumCostal cartilageCostal marginStructure of a Typical RibMain parts:HeadArticulates posteriorly with facets (demifacets) on bodies of two adjacent vertebraeNeckTubercleArticulates posteriorly with transverse costal facet of same-numbered thoracic vertebraShaftFigure 7.23aTransverse costal facet(for tubercle of rib)Superior costal facet(for head of rib) Body of vertebraHead of ribIntervertebral discTubercle of ribNeck of ribShaftSternumAngleof ribCross-sectionof ribCostal grooveCostal cartilage(a) Vertebral and sternal articulations of atypical true ribFigure 7.23bSpinous processArticular faceton tubercle of ribShaftLigamentsNeck of ribHead of ribBody ofthoracicvertebraTransversecostal facet(for tubercleof rib)Superior costal facet(for head of rib)(b) Superior view of the articulation between arib and a thoracic vertebra