NERVOUSSYSTEM:SPINALCORDANDSPINALNERVES

HumanAnatomyUnit4

InAnatomyToday

GrossAnatomy• Size:42-45cmlong• Regions

– Cervical• Continuouswithmedullaoblongata• Motorneuronsformcervicalspinalnerves

– Thoracic• Motorneuronsformthoracicspinalnerves

– Lumbar• Motorneuronsforlumbarspinalnerves

– Sacral• Motorneuronsforsacralspinalnerves

– Coccygeal

Note:doesn’tmatchupexactlytovertebrae

Regions• Cervicalenlargement– Innervatesupperlimbs

• Lumbarenlargement– Innervateslowerlimbs

• Conusmedullaris=endofthespinalcord– Caudaequina=axons– Filumterminale(alsocalledthecoccygealligament)=piamaterthatanchorsconusmedularistococcyx

Meninges• Piamater– Denticulateligaments– Coccygealligament– Formalateralshelfseparatingthedorsalandventralrootlets

• Arachnoidmater– Subarachnoidspace– CSF

• Duramater• Onlyonelayerinthe

spinalcord• Epiduralspace

SectionalAnatomyoftheSpinalCord

RegionalDifferences

Region Diameter Shape Ratio

Cervical Largest(10-15mm)

Ovalwithflattening

h whitevsgray

Thoracic Smaller Ovalwithflattening

h whitevsgray

Lumbar >thoracic Almostcircular

i white

Sacral Smallest Almostcircular

white=gray

OrganizationofWhiteMatter

SpinalCordWhiteMatter

• Columns– segmentsofmyelinatedaxonsthatleadup/downthespinalcord

• Ascendingtracts– leadupthespinalcordtothebrain– Example:spinothalmictract

• Descendingtracts– leadfromthebraindowntothespinalcord– Example:corticospinaltract

SpinothalamicTract

• SpinothalamicTract– Infotothalamus• Pain• Temperature• Itch• Crudetouch

–Decussatesinspinalcord–Receivessensoryinformationfromskin,viscera

CorticospinalTract

• OneofthePyrimidalTractsofthemedullaoblongata• Fromcerebralcortextomotorneuronsinthespinalcord• Controlsmovementsoflimbsandtrunk• Decussationinthemedulla–Decussationofthepyramids–About80%

SpinalNerves

• ConnectCNStomuscles,receptors,glands

• 31pairs• 8pairsCervical• 12pairsThoracic• 5pairsLumbar• 5pairsSacral• 1pairsCoccygeal

Dermatomes

• Eachpairofspinalnervesmonitorsaspecificregionofthebody’ssurface

AnatomyofaPeripheralNerve• Eachperipheralnervehas3layersofconnectivetissue• Epineurium– Surroundstheoutersurfaceofthenerve– DenseirregularCT– Blood-nervebarrier

• Perineurium– Enclosesbundlesofaxons– Fascicles

• Endoneurium– Areolar CT– CapillarieswithinsupplyoxygenandnutrientstotheaxonsandSchwanncells

AnatomyofaPeripheralNerve

PeripheralDistributionofSpinalNerves

• Eachspinalnerveisformedfromthefusionofdorsalandventralrootsastheypassthroughtheintervertebralforamen

• Nervesthendivideintoseveralbranches

DistributionofMotorNeuronsintheSpinalCord

DistributionofSensoryNeuronsintheSpinalCord

NervePlexuses• Segmentscontrollingskeletal

musculature– Neck– Upperlimbs– Lowerlimbs

• Ventralrami ofadjacentspinalnervesblendtheirfiberstoformaseriesofcompoundnervetrunks

• Nervesplexuses– Cervical– Brachial– Lumbar– Sacral

• Occursduringskeletalmuscledevelopment

CranialNerves

• 12pairs– Arisefromtheinferioraspectofthebrain

– 2fromtheforebrain– 10fromthebrainstem

• Functions– Sensory– Motor– ….orboth

CranialNervesCNI OlfactoryNerve Oh Some

CNII OpticNerve Oh Say

CNIII OculomotorNerve Oh Marry

CNIV TrochlearNerve To Money

CNV TrigeminalNerve Touch But

CNVI AbducensNerve And My

CNVII FacialNerve Feel Brother

CNVIII VestibulocochlearNerve Very Says

CNIX GlossopharyngealNerve Good Big

CNX VagusNerve Velvet Brains

CNXI AccessoryNerve A Matter

CNXII HypoglossalNerve H Most