the axial skeleton (contd.) & the appendicular skeleton human anatomy sonya schuh-huerta, ph.d

The Axial Skeleton (contd.) &The Appendicular Skeleton

Human AnatomySonya Schuh-Huerta, Ph.D.

The Vertebral Column Formed from 26 bones in the adultTransmits weight of trunk to lower limbsSurrounds & protects spinal cord

The Vertebral Column Serves as attachment sites for muscles of the neck and backHeld in place by ligamentsAnterior & posterior longitudinal ligaments Ligamentum flavum

The Vertebral ColumnCervical curvature(concave)7 vertebrae, C1 C7Thoracic curvature(convex)12 vertebrae,T1 T12Lumbarcurvature(concave)5 vertebrae, L1 L5Sacralcurvature(convex) 5 fusedvertebrae sacrumCoccyx4 fused vertebraeAnterior viewRight lateral viewC1T123456789101112L12345234567SpinousprocessTransverseprocessesIntervertebraldiscsIntervertebralforamen

Regions & Normal CurvaturesThe Vertebral column has 5 major regions7 cervical vertebrae of the neck region12 thoracic vertebrae5 lumbar vertebraeSacrum five fused bonesInferior to lumbar vertebraeCoccyx inferior to sacrum

Regions & Normal CurvaturesCurvatures of the spineCervical & lumbar curvaturesConcave posteriorlyThoracic & sacral curvaturesConvex posteriorly

Regions & Normal CurvaturesCurvatures increase resilience of spineThoracic & sacral curvaturesPrimary curvaturesPresent at birthLumbar curvatureDevelops when baby begins to walk (~1 year)

Ligaments of the SpineMajor supporting ligamentsAnterior longitudinal ligamentAttaches to bony vertebrae & intervertebral discsPrevents hyperextensionPosterior longitudinal ligamentNarrow & relatively weakAttaches to intervertebral discs

Posterior longitudinalligamentAnterior longitudinalligamentBody of a vertebraIntervertebral disc(b) Anterior view of part of the spinal columnLigaments of the SpineSupraspinous ligamentIntervertebraldiscAnteriorlongitudinalligamentIntervertebral foramenPosterior longitudinalligamentAnulus fibrosusNucleus pulposusSectioned bodyof vertebraTransverse processSectionedspinous processLigamentum flavumInterspinousligamentInferior articular process(a)Median section of three vertebrae, illustrating the compositionof the discs and the ligaments

Intervertebral DiscsAre cushion-like pads between vertebraeComposed of:Nucleus pulposusAnulus fibrosus

Intervertebral DiscsNucleus pulposus derived from notocordGelatinous inner sphereAbsorbs compressive stressesAnnulus fibrosusOuter rings formed of ligamentInner rings formed of fibrocartilageSurround the nucleus pulposus

Intervertebral DiscVertebral spinous process(posterior aspect of vertebra)Spinal nerve rootAnulus fibrosusof discHerniated portionof discNucleuspulposusof discSpinal cord(c) Superior view of a herniated intervertebral discTransverseprocessMRI of lumbar region of vertebral column in sagittal section showing normal & herniated discsNucleus pulposus of intact discHerniated nucleuspulposus

General Structure of VertebraePosteriorAnteriorLaminaSuperior articularprocessandfacetTransverseprocessPedicleSpinousprocessVertebralarchVertebralforamenBody(centrum)

General Structure of VertebraeCommon structures to all regionsBodyVertebral archVertebral foramenSpinous processTransverse processSuperior & inferior articular processesIntervertebral foramina

Movement of the Vertebrae Specific regions of the spine perform specific functionsTypes of movement that occur between vertebraeFlexion & extensionLateral flexionRotation in the long axis

Cervical Vertebrae 7 cervical vertebrae (C1C7) smallest & lightest vertebraeC3C7 are typical cervical vertebrae Body is wider laterallySpinous processes are short & bifid (except C7)Vertebral foramen are large & triangularTransverse processes contain transverse foraminaSuperior articular facets face superoposteriorly

Cervical Vertebrae

Dens of axisTransverse ligamentof atlasC1 (atlas)C2 (axis)C3Bifid spinousprocessTransverse processesC7 (vertebraprominens)(a) Cervical vertebraeInferior articularprocessCervical Vertebrae

The Atlas C1 is termed atlasLacks a body & spinous processSupports the skull Superior articular facets receive the occipital condylesAllows flexion & extension of neck Nodding the head yes

The AtlasAnterior archSuperior articularfacetTransverse foramenPosterior archPosterior tubercleAnterior tuberclePosteriorLateralmasses(a) Superior view of atlas (C1)C1

The AtlasFacet for densTransverseprocessLateralmassesTransverse foramenPosterior archPosterior tuberclePosteriorAnterior tubercleAnterior arch(b) Inferior view of atlas (C1)InferiorarticularfacetC1

The Axis Has a body & spinous processDens (odontoid process) projects superiorlyFormed from fusion of the body of the atlas with the axisActs as a pivot for rotation of the atlas & skullParticipates in rotating the head from side to side (nodding no)

The AxisC2PosteriorDens(c) Superior view of axis (C2)InferiorarticularprocessBodySuperior articularfacetTransverseprocessPedicleLaminaSpinous process

Thoracic Vertebrae (T1T12)All articulate with ribsHave heart-shaped bodies from the superior viewEach side of the body of T1T10 bears demifacts for articulation with ribsT1 has a full facet for the first ribT10T12 only have a single facet

Thoracic Vertebrae

Thoracic VertebraeSpinous processes are long & point inferiorlyVertebral foramen are circularTransverse processes articulate with tubercles of ribsSuperior articular facets point posteriorlyInferior articular processes point anteriorlyAllows rotation & prevents flexion and extension

Lumbar Vertebrae (L1L5)Bodies are thick & robustTransverse processes are thin & taperedSpinous processes are thick, blunt, & point posteriorlyVertebral foramina are triangularSuperior & inferior articular facets directly mediallyAllows flexion & extension rotation prevented

Lumbar Vertebrae

SuperiorarticularprocessTransverseprocessSpinousprocessIntervertebraldiscBodyInferiorarticularprocess(c) Lumbar vertebraeLumbar Vertebrae

Sacrum (S1S5)Shapes the posterior wall of pelvisFormed from 5 fused vertebraeSuperior surface articulates with L5Inferiorly articulates with coccyxSacral promontoryWhere the first sacral vertebrae bulges into pelvic cavityCenter of gravity is 1 cm posterior to sacral promontoryAla develops from fused rib elements

SacrumSacral foraminaVentral foraminaPassage for ventral rami of sacral spinal nervesDorsal foraminaPassage for dorsal rami of sacral spinal nerves

SacrumBody offirstsacralvertebraTransverse ridges (sites of vertebralfusion)CoccyxCoccyxAnteriorsacralforaminaApexPosteriorsacralforaminaMediansacralcrestSacral promontorySacralcanalSacralhiatusBodyFacet of superiorarticular processLateralsacralcrestAuricularsurfaceAla(a) Anterior view(b) Posterior view

CoccyxIs the tailbone Formed from 35 fused vertebraeOffers only slight support to pelvic organsEasily injured

The Thoracic CageForms the framework of the chestComponentsThoracic vertebrae posteriorlyRibs laterallySternum and costal cartilage anteriorlyProtects thoracic organsSupports shoulder girdle and upper limbsProvides attachment sites for muscles

IntercostalspacesTrue ribs(17Falseribs(812)Jugular notchClavicular notchManubriumSternal angleBodyXiphisternaljointXiphoidprocessL1VertebraFloating ribs (11, 12)(a) Skeleton of the thoracic cage, anterior viewSternumCostal cartilageCostal marginThe Thoracic Cage

The Thoracic CageXiphisternalXiphisternaljointHeartSternal angleJugular notch(b)Midsagittal section through the thorax, showingthe relationship of surface anatomical landmarksof the thorax to the vertebral columnT2T4T3T9

SternumFormed from three sectionsManubriumsuperior sectionArticulates with medial end of claviclesBodybulk of sternumSides are notched at articulations for costal cartilage of ribs 27Xiphoid processinferior end of sternumOssifies around age 40

SternumAnatomical landmarksJugular notchCentral indentation at superior border of the manubriumSternal angleA horizontal ridge where the manubrium joins the bodyXiphisternal jointWhere sternal body and xiphoid process fuseLies at the level of the 9th thoracic vertebra

RibsAll ribs attach to vertebral column posteriorlyTrue ribs - superior seven pairs of ribsAttach to sternum by costal cartilageFalse ribsinferior five pairs of ribsRibs 1112 are known as floating ribs

RibsJunction withcostal cartilageShaftHeadNeckArticular faceton tubercleCostal angleCostal grooveFacets for articulationwith vertebrae(a) A typical rib (rib 6, right), posterior viewTransverse 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 groove(b) Vertebral and sternal articulations of a typical true ribCostal cartilage

Spinous processArticular faceton tubercle of ribShaftLigamentsNeck of ribHead of ribBody ofthoracicvertebraTransversecostal facet(for tubercleof rib)Superior costal facet(for head of rib)(c)Superior view of the articulation between a rib and athoracic vertebraRibs

Disorders of the Axial SkeletonCleft palateA common congenital disorderRight & left halves of palate fail to fuse mediallyCan involve entire palate & lip minor to severe

Stenosis of the lumbar spineNarrowing of the vertebral canalCan compress roots of spinal nerves

Disorders of