AnatomyoftheEyeIntroduction

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AnatomyoftheEye

Bytheendofthismodule,youwillbeableto:

• Describetheanatomicalstructuresoftheeye.

• Identifythelayersoftheeye.

• Describethecontentsoftheeye.

• Describethestructuresassociatedwiththeeye.

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Lid,BrowandLash

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Eyebrow

Shorthairsrootedintheskinjustovertheuppermarginsoftheeye’sorbitalcavity.

Eyelid

The eyelidscover, protect,andlubricatetheeyeball.

Eyelash

Shorthairsborderingthedelicateeyestructure.Likeciliainotherpartsofthebody,theeyelashestrapforeignparticles.

AnatomyoftheEyeSegment2:InteriorViewoftheEye

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InteriorViewoftheEye

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Definitiontextforeachelementintheinteriorviewwillappearwhenrolledover.

Retina(example)here…

FocalPoint(example)here…

HowDoWeSee?

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1. Lightisreflectedfromtheobjectandpassesintheeyethroughthecornea.

2. Theirisregulatesthesizeofthepupil,theopeningthatcontrolstheamountoflightthatenterstheeye.

3. Behindthepupilisthelens,whichfurtherfocuseslight,oranimage,ontotheretina.

4. Theretinaisathin,delicate,photosensitivetissuethatcontainsthespecial“photoreceptor”cellsthatconvertlightintoelectricalsignals.

5. Theseelectricalsignalsareprocessedfurther,andthentravelfromtheretinaoftheeyetothebrainthroughtheopticnerve.

6. We“see”withourbrains;oureyescollectvisualinformationandbeginthiscomplexprocess.

AnatomicalDirections

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MedialandLateralTowardthecenterlineofthebody.Forexample,noseismedialtoeacheye,andfartherawayfromthecenterofthebody.

NasalandTemporalReferstothenoseandcanbesubstitutedformedial,andtemporalreferstothetempleareaoneithersideofthehead.

SuperiorandInferiorRefers toastructureaboveanotherandastructurebelowanother.

PosteriorandAnteriorTowardtherearoftheheadandtowardthefrontofthehead.

AnatomicalDirections

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AnteriorSegmentCornea,Iris,ciliarybody,crystallinelens

ChambersoftheAnteriorSegmentTheanteriorchamber,andposteriorchamber.

PosteriorSegmentEye’slargestcavity,andincludestheretinaandopticdisc.

CheckYourUnderstanding

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SHOWWHATYOUKNOWClickonananatomicalpartoftheeyeanddragittoitsproperlocation.

ClicktheCheckAnswerbuttonwhenyouarefinished.

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Brow

Lashes

Iris

Corneal-Scleral-Limbus

Retina

Sclera

Pupil

Conjunctiva

CheckAnswer

SHOWWHATYOUKNOWChoosethecorrectletterforeachanatomicalpartoftheeye.

ClicktheCheckAnswerbuttonwhenyouarefinished.

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A.Cornea

B.CrystallineLens

C.Retina

D.OpticNerveFibers

CheckAnswer

SHOWWHATYOUKNOWMatcheachpartoftheeyetoitsdescription.

ClicktheCheckAnswerbuttonwhenyouarefinished.

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Eyelid

Eyelash

Cornea

Pupil

CheckAnswer

Iris

A. [Eyelid]Theycover,protect,andlubricatethe eyeball.

B. [Eyelash]Shorthairsborderingthedelicateeyestructure.Likeciliainotherpartsofthebody,theeyelashestrapforeignparticles.

C. [Cornea]Thecornea isanteriortoboththelensandretina.Corneaistheclearfrontwindowoftheeyethattransmitsandfocuseslightintotheeye.

D. [Pupil]Theirisregulateslightthatenterstheeyethroughthepupil,theholeinthecenteroftheeye.

E. [Iris]Theirisisthecoloredorpigmentedtissueoftheeyejustbehindthecorneaandinfrontofthelens.Themusclesoftheiriscontractandexpandtochangethesizeofthepupilindifferentlightingconditions.

AnatomyoftheEyeSegment3:LayersoftheEye

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LayersoftheEye

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Thefibrouslayeristheoutermostlayerthatprotectsandsupportstheshapeoftheglobetoavoidopticaldistortion.

Thevascularlayeristhemiddlelayer;alsoknownastheuvea.Itsuppliesbloodtotheglobe.Itisanimportantsourceofoxygenandnutrientsfortheglobe.

Thenervouslayeristheinnerlayer,alsoknownastheretina.Ittransmitssensoryinformationaboutlighttothebrain.

TheFibrousLayer

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• Sclera

• Limbus

• Cornea

TheVascularLayer

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Choroid

StructureThechoroidliesbetweentheretinaandsclera.Itiscomposedoflayersofbloodvesselsthatnourishtheouterretina.

FunctionsThechoroidsuppliesnutrientstotheouterretinaandhelpsregulatetheoculartemperature.

TheNervousLayer

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Retina

StructureThenervouslayerortheretinaisacomplextissuethatmakesuptheinternaltwo-thirdsofthebackoftheeye.Itcontainsnervefibersthatarelongcellextensionsthroughwhichsensoryinformationtravels.

FunctionsTheretina,whichistheinnermostlayeroftheeye,performsthefunctionthatgivestheeyeitspurpose—itdetectslightandsendssensoryinformationtothebrainforprocessing.

LayersoftheCornea

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Definitionsofthecorneawillappearherewhenlearnerrollsover…

VascularLayer(Uvea)

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• Pupil

• Iris

• CiliaryBody

• Choroid

VascularLayer(Iris)

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StructureTheirisisthecoloredorpigmentedtissueoftheeyejustbehindthecorneaandinfrontofthelens.Themusclesoftheiriscontractandexpandtochangethesizeofthepupilindifferentlightingconditions.

FunctionTheirisregulateslightthatenterstheeyebymodifyingthesizeofthepupil,theholeinthecenter,andthroughconstrictionordilation.

VascularLayer(CiliaryBody)

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CiliaryMusclesTheciliarymusclesaltertheshapeofthelenstoadjustandfocusvisioninaprocesscalledaccommodation.

ZonularFibersThezonularfiberssuspendthelensfromtheciliarymuscles.

CiliaryProcessesTheciliaryprocessesarefinger-likeprojectionsfromtheciliarymusclesthatproduceaqueoushumor.

NervousLayer(Retina)

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Thereare10uniquelayersoftheretina.

Theyreceivelightfromanobjectandconvertitintoelectricalimpulsesthatarethentransmittedtothebrain.

NervousLayer(Fundis)

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Ophthalmoscope

Giveseye-careprofessionalanideaaboutthestateofthetissuesinthebackoftheeye,suchastheretina,choroid,andmajorbloodvessels.

NervousLayer(Fundis,Con’t_)

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TheFundis includes:

• Maculalutea

• Foveacentralis

• Opticdisc

AnatomyoftheEyeSegment4:ContentsoftheEye

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AqueousandVitreousHumor

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Theeye’santeriorandposteriorsegmentsarefilledwithfluids,orhumor.

Thisplaysavitalroleinmaintainingocularfunction.

Thesefluidsarecalledtheaqueoushumorandvitreoushumor.

AqueousandVitreousHumor

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AqueousHumorProduction.Fillstheanteriorsegmentoftheeye.Thin,clear,andwateryfluidproducedbytheepithelialtipsoftheciliarybody,locatedintheposteriorchamber.

Drainage.Flowsfromtheposteriorchamber,throughthepupil,intotheanteriorchamber,andthendrainsoutthroughtheanglethatbalancestheproductionanddrainagetomaintainintraocularpressure.

Function.Aqueoushumorsuppliesnutrientsforthelensandcorneaandcarriesawaywasteandcarbondioxide.

VitreousHumorThevitreous,madeupofthevitreousbodyandthevitreouscortex,fillsthelargecavitybetweenthelensandthefrontoftheretina.

Itismostlywater(roughly98%to99%)andmacromolecules.

Thecortex,orouterportion,iseasilydistinguishablefromthebodybecauseithasahighconcentrationofmatrixproteins.

CrystallineLens

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StructureThecrystallinelensisatransparent,flexiblestructurelocatedintheanteriorportionoftheeye,behindtheiris.

Mostofthelensismadeupoflensfibersthatarepackedintotight,onion-likelayersthatcontainsnobloodvessels.

Getsnutritionfromthefluidsthatsurroundit,primarilytheaqueous.

Externalportion,orcortex,hasahigherrateofmetabolismthanitsinternalportion,ornucleus.

FunctionThelenschangesshapetofocuslightraysontheretina,whichenablestheeyetoseeobjectsatarangeofdistances.

CrystallineLens

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Click on each arrow to see the six muscles and their positions in relation to the globe.

CheckYourUnderstanding

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SHOWWHATYOUKNOWWhenreferringtotheaqueousandvitreouspartsoftheeye,selectAforaqueousorVforvitreoustothefollowingquestions.

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[V]Composedmostlyofwater,itfillsthelargecavitybetweenthelensandthefrontoftheretina.

[A]Thin,clear,andwatery,itfillstheanteriorsegmentoftheeye.

[A]Flowsfromtheposteriorchamber,throughthepupil,intotheanteriorchamber,andthendrainsoutthroughtheangle.

[A]Suppliesnutrientsforthelensandcornea.

SHOWWHATYOUKNOWWhichofthefollowingstatementsiscorrect?

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A. Lightisrefractedasitpassesthroughthecorneaandcrystallinelensbeforeitreachestheretina.

B. Whentheeyeviewsanobjectatalldistances,theciliarymusclerelaxes.

C. Thenervouslayer,orretina,consistsoffiveseparatelayers.

D. Thecorneaactslikeanapertureonacamera,regulatinglightthatenterstheeye.

SHOWWHATYOUKNOW

Extraocularmusclesareacollectionofsixmusclesthatcontrolthemovementsoftheeyeballandarenamedforpositionstotheglobe.

qTrueqFalse

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SHOWWHATYOUKNOWTheeyeisanearlysphericalorganthatcontainsthreeconcentriclayers.Matchthethreeconcentriclayerstotheircorrectdescription.

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Fibrouslayer

Vascularlayer

Nervouslayer

Composedoftwostructures,thescleraandthecornea.

Madeupofthreesegments– theiris,theciliarybody,andthechoroid.

Referredtoastheretina,itconsistsof10uniquelayersthattransmitssensoryinformationaboutlighttothebrain.

SHOWWHATYOUKNOWFillintheblank.

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Theconjunctivaisathin,transparent,mucousmembranethatlinestheeyelidsandsclera,butnotthe_[cornea]__.

CONGRATULATIONS!

YouhavesuccessfullycompletedtheAnatomyoftheEyemodule.

Youshouldbeableto:• Describetheanatomicalstructuresoftheeye.• Identifythelayersoftheeye.• Describethecontentsoftheeye.• Describethestructuresassociatedwiththeeye.

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