2-histology of the eye teamwork - ksumscksumsc.com/download_center/2nd/1) neuropsychiatry...
TRANSCRIPT
Objectives:Bytheendofthislecture,thestudentshouldbeabletodescribe:
üThegeneralstructureoftheeye.üThemicroscopicstructure of:
Cornea.Retina.Limbus.
Threecoats(3Tunics) Components Notes
1- Fibroustunic: A- CorneaB- Sclera
Outermostandtoughcoat
2- Vascular tunic:A- Choroid
B- CiliarybodyC- Iris.
- Themiddlecoat.- Alsocalleduveal
coat.
3- Neuraltunic: A- Retina Innermostandnervouscoat
EYEBULB
Cornea: Itisthetransparent,avascular andhighlyinnervatedanteriorportionofthefibrouscoat.(Represent theanterior1/6oftheouterfibrouscoatofeyeblub)(Ittakesitsnutrientsfromlimbusviadiffusion )
Composedof5distinctlayers:
1.Cornealepithelium.2.Bowman’smembrane.3.Stroma.4.Descemet’smembrane.5.Cornealendothelium.
1- Cornealepithelium:
Non-keratinizedStratifiedsquamousepithelium.(itisanterior)Containsnumerousfreenerveendings.
2- Bowman’smembrane:
Itisahomogenousnon-cellularlayercontainingtypeIcollagenfibrils. (posteriortotheepithelium)
3- Stroma:
Itisthethickestlayer(about90%).ItiscomposedofparallellamellaeofdensecollagenousC.T.EachlamellaiscomposedmainlyofparalleltypeIcollagenfibers withlongfibroblasts.
4- Descemet’smembrane: Itisathickbasementmembrane.(Anteriortotheendothelium)
5- Cornealendothelium:
- Itissimplesquamousepithelium. (posterior)- Functions:1- FormationofDescemet’smembrane.2- Keepingthestromarelativelydehydrated(sod.pump→waterwithdrawalfromthestroma).
Fibroustunic:CORNEAمھم
LIMBUSمھم (CORNEOSCLERALJUNCTION)
- Itisthetransitionregionbetweenthecorneaandsclera.- Itisabout1.5mmwidth.- Itishighlyvascular.Itgivesnutrientstocornea.
- Itcontains:1- Trabecularmeshwork(smallwindows):Endothelium-linedspaces.ItleadstocanalofSchlemm.(AlsocalledspacesofFontana)
2- CanalofSchlemm:Itdrains theaqueoushumorintothevenoussystem.Thecanalmimicsbloodcapillaries.(Ifthereisanyobstructioninthepathwayofaqueoushumoritwillleadtoglaucoma)
Sclera
Cornea
Iris
Ciliarybody
Canal of Schlemm
Fibroustunic:Sclera• Itcovers theposterior 5/6ofthefibrous
tunic.• ScleraProper:consistsofinterlacing
bundlesoftypeIcollagen(densecollagenousC.T.,irregulartype).
• Melanocytes arelocatedinthedeeperregions.
Vasculartunic:Choroid• isthevascular,pigmentedposteriorto
cornea portionofthemiddlevasculartunic.
• Structure:1. ItiscomposedmainlyoflooseC.T. with
melanocytes.LooseCTisalwaysrichinbloodvessels2. Itisseparatedfromtheretinabyits
Bruch’smembrane.
Bruche’s membraine
Vasculartunic:CiliarybodyItistheanteriorcontinuationofthechoroid.Itsurroundsthelens.Structure:• ItisformedofloosevascularandpigmentedC.T.
thatcontains3bundlesofsmoothmusclecells(ciliarymuscle).
• Itsinnersurfaceislinedbyparsciliaris retinae(2rowsofcolumnarcells;outerpigmentedandinnernon- pigmentedlayers).• Itsinnersurfaceishighlyfoldedformingthe
ciliaryprocesses.
Ciliaryprocesses(smoothmuscles)
• Processesprojectfromtheinnersurfaceoftheanterior1/3oftheciliarybodytowardsthelens.
• Arecoveredbyparsciliaris retinae(2rowsofcolumnarcells).
• Theygiveattachmenttothelenssuspensoryligaments(zonule fibers).
• ciliaryprocessiswhatcontrolscurvatureofthelensbutitisnotdirectlyattachedtoit.
Posteriorchamber
Anteriorchamber
1- Anteriorborderlayer Incompletelayeroffibroblastsandmelanocytes.Most ofitareconessells
2- Stroma PoorlyvascularizedC.T.withfibroblastsandmelanocytes.
3- VessellayerMoreprominentlayer
Well-vascularizedlooseC.T.Centrally,itcontainscircularly arrangedsmoothmusclefibers(sphincterpupillaemuscle).
4- DilatorpupillaemusclelayerArranged insunraysshape
Containsradiallyarrangedmyoepithelialcells.Sotheirisconstrictsanddilatesthepupil.
5- Posteriorsurfacelayer(pigmentedepitheliumlayer)
Itiscomposedof2rowsofpigmentedepithelialcells(parsiridisretinae).Theyarethecontinuationofparsciliarisretinae.
IRIS
Layers Features Function
1-Pigmentedepithelium
ü Cuboidaltocolumnarcells (singlelayer). Short columnü Apicalmicrovilli. Increase surfaceareaandactasphagocyteü Abundanceofmelaningranules.
ü Absorblight.ü Phagocytosisofmembranousdiscsfromtipsof
rods.(Whenrodsarestimulated,theyrupture)ü EsterificationofVitaminA(inSER).
2-Rodsandconeslayer.
ü Arephotoreceptorcells.ü Eachhas:1.Dendriteformedof:- Outersegment(OS): containsmembranousdiscscontainingrhodopsin(inrods)andiodopsin (incones).- ConnectingStalk: withmodifiedcilium.- Innersegment(IS).2.Cellbody.3.Axon: synapseswithdendriteofbipolarneuronofinnernuclearlayer.
ü Rodsarereceptorsfordimlight(lowintensitylight).
ü Conesarereceptorsforbrightlightandcolorvision (red,green &blue).
3-Outerlimitingmembrane. Aregionofzonulae adherentsjunctionsbetween Mullercellsandthephotoreceptors.
4-Outernuclearlayer: Containsnucleioftherods&cones.
5-Outerplexiform layer: Containsaxodendritic synapsesbetweenthephotoreceptorcellsanddendritesofbipolarandhorizontalcells.
6-Innernuclearlayer:
Containsthenuclei of:1- Bipolarneurons.2- Horizontalneurons.3- Amacrine neurons(unipolar neurons):4- Neuroglialcells(Mullercells)thatextend betweenthevitreousbodyandtheinnersegmentsofrodsandcones.
7-Innerplexiform layer: Containsaxodendritic synapsesbetweenaxonsofbipolarneuronsanddendritesofganglioncellsandamacrine cells.
8-Ganglioncelllayer: Containscellbodiesoflargemultipolar neuronsoftheganglioncells.
9-Opticnervefiberlayer: Containsunmyelinated axonsoftheganglion cells.N.B.Theseaxonsbecomemyelinated asthenervepiercesthesclera.
10-Theinnerlimitingmembrane: Itisformedbythebasallaminae oftheMullercells.
light
Cones>Color >Large>BrightLight
RETINAمھم
Theaxonsofrodsandconessynapsewithdendritesofinnernuclearlayer.Theinnernuclearlayercellsynapsewitheachotherandwithganglioncelllayer.
1- Pigmentedepithelium.
2- Nervecells:
- Photoreceptorcells(rods&cones).
- Bipolarneurons.
- Ganglioncells.
- Associationneurons:
i.Horizontalcells.
ii.Amacrine cells.
3- Neuroglial cells:
- Muller’scells.
- Astrocytes.scattered
Itliesinthecenterofmaculalutea.
Cones arehighlyconcentratedinthefovea.
Itisresponsibleforvisualacuity.
Foveacentralis: Typesofcellsintheretina: Definition L.M.Picture
Itisthetransparentmucousmembraneliningtheinnersurfacesofthe
eyelids(palpebralconjunctiva)andreflectingontothescleraoftheanteriorsurfaceoftheeye
(bulbarconjunctiva).
1- Epithelium:Stratifiedcolumnarepitheliumwithnumerousgoblet
cells.
2- Laminapropria:LooseC.T.
Lessthicknessdepressioncalledmaculaluteaneartheopticnerve
RETINAمھم CONJUCTIVA
MCQ’s1-C2-B3-D4-B5-B6-D7-C8-A
1-whichoneofthefollowingstructureskeepthestromaofcornearelativelydehydrated?A-CornealepitheliumB-Bowman’smembraneC-CornealendotheliumD-Descemet’smembrane
2-Canalofschlemm isfoundinwhichofthefollowing?A-RetinaB-limbus(Corneoscleraljunction)C-scleraD-Choroid
3- whichofthefollowingasthefunctionofthepigmentedepithelialcellsfoundinretina?A- AbsorblightB- PhagocytosingoftipsoftherodetoregenerateC- EsterificationofVit AD- Allabove
4- whichofthefollowingsitescontainthehighestconcentrationofcones?A- OpticdiskB- FoveacentralisC- ConjunctivaD- Allabove
5-ThescleraconsistoflosecollagenousC.TregulartypeA-trueB-false
6-ThechoroidisseparatedfromtheretinabyA-Bowman’smembraneB-CanalofschelmmC-opticdickD-Bruch’smembrane
7-Whichlayershavethenucleiofrodsandcons?A-RodandConslayerB-innernuclearlayerC-OuternuclearlayerD-Ganglioncelllayer
8-Gobletcellsfoundarein?A-conjunctivaB-RetinaC-ChoroidD-limbus