DRMATS HISTOLOGY CAPSULE: REVISION GUIDE FOR MEDICOS.pdf

Histology is the biological study of the microscopic structure of tissues and cells. It involves preparing thin tissue samples, staining them, and examining them with light or electron microscopes to understand how cells are organized and how this organization relates to their function. This scientific discipline is crucial for understanding normal biological processes and diagnosing diseases by identifying characteristic structural changes in tissues, a subfield known as histopathology.

1. 1
DRMATS’
EssentialHistology
Last-MinuteExamBooster”
"Aconcise,exam-orientedstudyaidspeciallycuratedbyDr.Matstosupport
slowlearnersandallMBBSstudentsduringfinalrevision.Simplifiedfor
clarity.Structuredforsuccess."
DrMathewJoseph,
MBBS,MD(AIIMS),BCC(PalliativeMedicine)
AssistantProfessor
DepartmentofAnatomy
AmalaInstituteofMedicalSciences,Thrissur

2. 2
1.Microscope
Amicroscopeisanopticalinstrumentusedtomagnifysmallobjects.Insimplemicroscopeasingle
convexlensisusedandincompoundmicroscopemorelensesareused.Inlightmicroscopenaturalor
artificiallightisusedwhileanelectronmicroscopeusesanelectronbeam.Dependinguponnumberof
eyepiecesmicroscopesarecalledasmonocular,binocular/trinocularetc.
Fluorescence,polarizing,phasecontrastordarkgroundilluminationfacilitiesmaybeaddedto
compoundmicroscopes.
a)Partsofmonocularcompoundmicroscope:Amonocularcompoundmicroscopehasabase,which
is'U'or'V'shapedandalimboranarmattachedtobase.Abodytubeisfittedtoupperendofarm
andstageisfittedtolowerendofarm.Bodytubeholdseyepieceinupperpartandanosepiecein
lowerpart.Fourdifferenttypesofobjectives(scanning,lowpower,highpower&oilimmersionlenses)
arefixedtonosepiecewhiledrawtubeholdseyepiece.Belowstagediaphragm,filterandcondenser
lensesarefixed.Therearefineandcourseadjustmentandcondenseradjustmentknobs.
b)Magnification:Extenttowhichsizeofobjectappearsincreasedinimageismagnificationbylight
microscopeisproductofmagnificationofeyepieceandmagnificationofobjective.
Lowpower Highpower Oilimmersion
Eyepiece(xtimes) 10 10 10
Objective(xtimes) 10 40 100
Magnification(xtimes) 100 400 1000
Diameterofareasunder
view 1500µ 375µ 150µ
c)Resolution:Itisabilityofanopticalinstrumenttodistinguishbetweentwoadjacentpointsclearly.
Smallerclearlyseendistancebetweentwopoints,betterisresolutionandbetterareimagedetails.
Resolutionbyanunaidedeyeis0.2mmormoreandwiththatoflightmicroscopeis0.25µormore.
Resolutiondependsuponwavelengthofenergy(light)employedforillumination:Inelectron
microscoperesolutionisincreasedbecauseenergyofshorterwavelength(electrons)isused.
d)Numericalaperture:Aperturesizeofobjectivelensisproductofrefractiveindex&anglebetween
opticalaxisoflensandmost.Inclinedraysoflightitcanaccept.Ifangleismoreproportionoflight
raysputtogooduseinformingimagearemorethusgreaterisproportionofpotentialdetails
reproducedinimage.Resolutionisinverselyproportionaltonumericalaperture.Brightnessoffieldis
directlyproportionaltosquareofnumericalaperture.

3. 3
2.Epithelium
Epitheliumisagroupofcells,withcomparativelylittleintercellularmaterial.Itcoversexternaland
internalsurfacesofbodyandcavities.Itmaybesimpleorstratified.
Simpleepithelium:Madeupofsinglelayerofcells.Itmaybeofseveraltypesaccordingtocell’sshape
andsize.
1.Simplesquamous:Cellsofepitheliumareflat,havinglengthandbreadthbutnegligible
thickness,withasmallroundandcentrallyplacednucleus.
2.SimpleCuboidal:Cellsarecubicallength,width&heightarealmostequal,withacentrally
placedsphericalnucleus.
3.SimpleColumnar:Cellsaretallinappearancelengthisgreaterthanwidth,cytoplasmlooks
vacuolatedduetomucinogenandnucleusisovalinshape.
4.PseudostratifiedColumnarCiliated:Allcellsofepitheliumtouchbaselinebutallofthemdonot
reachsurface.Sonucleiareplacedatdifferentlevels,givingastratifiedorlayeredappearance.
Stratifiedepithelium:Madeupofseverallayersofcellsandnameofepitheliumisgivenaccordingto
shapeofcellspresentinthemostsuperficiallayer.
1.Stratifiedsquamous:Basalcelllayerconsistsofcuboidalorlowcolumnarcellswithmitotic
activity.Intermediatelayersarepolygonalinshapeandsuperficialcellsareflattened.
2.Stratifiedcuboidal:Superficialcelllayeriscuboidalandrestarepolyhedralinshape.
3.Stratifiedcolumnar:Superficiallayersofcellsarecolumnaranddeepercellsarepolyhedralor
cuboidalinshape.
4.Transitional:Allcellsaresimilar,beingabletoadjustthemselvesaccordingtosurfacearea.The
outermostlayer,withdome-shapedorumbrellacells.Thesesurfacecellscanflattenandstretch,
whichisimportantforaccommodatingchangesinvolumeBasementmembraneisnotindented
byconnectivetissue.

4. 4
3.ConnectiveTissue
Tissuethatfillsinter-cellularspacebetweenmorespecializedelements,supportsandholdsthem
togetheriscalledconnectivetissue.Cellsarerelativelyfewandwidelyseparatedbyinter-cellular
substance.Connectivetissuecanassumevariousformsdependinguponnatureofgroundsubstance,
typeoffibersandcellspresentinthetissue.Differenttypesofcellsarepresentinconnectivetissue
likemesenchymalcells,fibroblast,fibrocytes,adiposecells,reticularcells,pigmentcells,macrophages,
mastcellandplasmacells.
Fibersinconnectivetissue:Therearethreemaintypesoffibres.
1.Collagenfibres:Mostnumerous,runinbundles,bundlesbrancandanastomose.Individualfibers
donotbranch.Theyareacidophilicinstaining.
2.Reticularfibres:Areofsmalllength,branchingandanastomosing.Theyarespeciallystainedby
silverstain.
3.Elasticfibres:Lessfrequentthancollagen,fine,runsingly,branchandanastomosefreely.

5. 5
4.Cartilage
Cartilageisconsideredtobeamodifiedconnectivetissuehavingcellsandmatrix(extracellular
component),wherematrixissolid.Ithascellslikechondrocytesandchondroblaststhatsynthesize
connectivetissuefibresandgroundsubstance.Cartilageisclassifiedaccordingtoamountandtypeof
fibres.Therearethreetypesofcartilage:
Hyalinecartilage:
1.Hasencapsulatedcartilagecells,formingcellnestsandgroundsubstanceappearshomogenous.
2.Refractiveindexofcollagenissameasthatofmatrix,sotheyarenotseenseparately.
3.Perichondriumcovershyalinecartilageexceptatarticularsurfaces.
4.Itisavascular.examplesaretrachea,bronchialtree,larynx.
Elasticcartilage:
1.Encapsulatedcartilagecellsarepresentsingly.
2.Groundsubstancecontainelasticfibres,andmatrixnon-homogeneous.
3.Elasticfibresarebetterseenwithorceinstain.
4.ExampleEpiglottis,Cartilageofexternalear,corniculateandapicesofarytenoid.
Fibrocartilage:
1Encapsulatedchondrocytesareovoid,surroundedbyconcentricallystriatedmatrix.
2Chondrocyteslieinrowsorlayers,betweenrowstherearebundlesofcollagenfibres.
3Perichondriumisabsent.
4Exampleintervertebraldisc,symphysispubis,intraarticulardisc.

6. 6
5.Bone
Boneishardspecializedconnectivetissue.
Compactbone:
1.ItconsistsofHaversiancanalsystemwhichconsistsofconcentrictubularlayersknownas
lamellae.
2.Haversiancanalcommunicateswitheachor,medullarycavityandoutersurfaceofbonethrough
obliquechannelcalledVolkmann’scanal.
3.HaversianandVolkmann’scanalsinlivingcontainbloodvessels,nervesandlymphatics.
4.Boneiscoveredbyperiosteumexceptarticular(cartilage)surfaces.
Spongybone:
1.LamellaeareirregularlyarrangedandHaversiansystemisabsent.
2.Bonemarrowispresentinlargemarrowspacesdefinedbyshelvesandspiculesof
bones.
3.Osteocytescanbeseeninlayersinadultspongybone.
DevelopingboneL.S.-processofboneformationisossification.Inendochondralossificationa
cartilagemodelisreplacedbybone.Theepiphysealplateoflongboneisbestexampleofgrowing
bone.Slideofdevelopingboneshowsfollowingzones.
1.Zoneofrestingcartilage-Chondrocytesaresmallandflat.Thisisareservezoneofnormalhyaline
cartilageinwhichchondrocytesaredistributedinlacunaesinglyoringroups.
2.Zoneofproliferation-Thisisazoneofcartilagegrowth.Cellsarelargerandshowmitoticactivity.y
multiplyandarrangeinparallelcolumnsseparatedbybarsofmatrix.
3.Zoneofmaturation-Cellsincreaseinthesizeandsecretealkalinephosphatase.Chondrocytes
hypertrophybyswellingofnucleusandcytoplasmandlacunaeenlarge.
4.Zoneofcalcification-Calciumsaltsaredepositedinmatrixofcartilage.Chondrocytesdieleaving
lacunaeoremptyspaces,withdeadanddyingcells.Thisischondrolysis.

7. 7
5.Zoneofossification-Bloodvesselsfromperiosteumgrowinsideandcalcifiedmatrixisreplacedby
bonematrix.Chondrogeniclayerofperiosteumisstimulatedtodifferentiateintoosteogeniclayer
fromwhichosteoblastareformed.

8. 8
7.MuscleTissue
Muscletissueismadeupofcellscalledmyocytes.Myocytesareelongatedandoftenreferredtoas
musclefibres.Muscletissueiscontractileinnatureduetopresenceofcontractileproteinelement.
Therearethreetypesofmuscletissueaccordingtofunctionandanatomicalclassification:
1.Skeletalmuscle:musclefibresarepresentinbundles.Theyareelongated,cylindrical,
multinucleatedcellswherenucleiareperipheralinpositionlyingjustbeneaththesarcolemma
(Cellmembraneofmusclecell).Musclefibreshavelongitudinalandtransversestriations.
T.S.-entiremuscleiscoveredbyatoughsheathofrelativelydenseconnectivetissuecalledas
epimysium.Thefibrouspartitionwhichextendsintomuscletosurroundfascicles(bundlesof
musclefibres)iscalledasperimysium.Delicatesheetsofconnectivetissuethatarisefromit
provideanetworkextendingbetweeneachandeverymusclefibreandconstitutesendomysium.
2.Smoothmuscle:Spindleshapedcellshavingsingle,centrallyplacedovalnucleus.Faintlongitudinal
striationsarepresent.
3.Cardiacmuscle:Eachmusclefibreshowsbranching,hasasinglecentrallyplacedovalnucleus.
Transversestriationsarepresent.Thejunctionsbetweenadjacentmusclecellsareseenasdark
stainingtransverselinesrunningacrossthefibrescalledintercalateddiscs.Gapjunctionsallow
electricalcontinuitythuscardiacmuscleisaphysiologicalsyncytiumbutnotananatomicalone.

9. 9
8.NerveTissue
Nervoustissueconsistsofneuronsandnervefibres.
Neuron:Isstructuralandfunctionalunitofnervoussystem.Ithasacellbodycalledperikaryonand
processesnamelyaxonanddendrites.Neuronsreceiveandconductimpulses.Theymaybeofunipolar,
bipolar,pseudounipolarandmultipolartype.
Nervefibres:maybemyelinatedorunmyelinated.
Neuroglialcells:Astrocytes(Fibrous,protoplasmic),oligodendroglialcells&microglialcells.
Peripheralnerve:Peripheralnervoussystemconsistsofgangliaandnerves.Ganglionisacollectionof
neuronsinPNSwhilenervesaremostlybundlesofaxons(motor)or/andperipheralprocessesof
sensoryganglia.
T.S.-Atubelikearrangementoffairlydenseextensiveconnectivetissuethatencasesthewholenerve
isepineurium.Perineuriumisinnerthickandstrongconnectivetissueenclosingafascicleofnerve
fibres.Eachnervefibre(axon)isenclosedinatubeofconnectivetissuecalledasendoneurium.
L.S.-Myelindissolvedawaybydehydrationandclearingagents,slipstoonesideofthespace.Myelin
canbeseenbyOsmicacidstainingmethod.Longitudinalsectionofperipheralnerveshowsstreaky
appearanceandstreaksruninawavysnakelikemanner.Manynucleiareseeninbundleoffibres.

10. 10
9.BloodVessels
Cardiovascularsystemconsistsofheartandbloodvessels.
Heart:Ithasthreelayersfrominsideout:1.Endocardium,2.Myocardium&3.Epicardium.
Arteries:histologicalstructureofanarteryvariesconsiderablywithitsdiameter.However,allarteries
havesomefeaturesincommon.Thewallofanarteryismadeupofthreelayers:
1.Tunicaintima:innermostlayer
2.Tunicamedia:middlelayer
3.Tunicaadventitia:outermostlayer.
Inartery,mediaisthickerthanortwocoats,whileinveinadventitiaisthickerthanortwocoats.
Dependinguponamountofelasticfibresorsmoothmuscles,arteriesaretheirelasticormusculartype.
A).Elasticartery-Comparedwithintimainorvesselselasticarteryshowsverythickintima,onefifth
oftotalthicknessofthewall.Internalelasticlaminaisnoteasytodistinguishasmediaconsistsof
mostlyelasticfibreswithfewsmoothmusclefibres.E.g.ascendingaorta,archofaorta,thoracicaorta,
pulmonaryarteryetc.
B).Muscularartery-Thesizeoflumenofthistypeofarteryisregulatedbythemuscles,soitisalso
calledasadistributingartery.Internalelasticlaminaisseenatjunctionofintimaandmedia.Itis
usuallyinacontractedconditiongivingawavyappearancetointimaandiseasilyseenasbrightpink
line.Mediaconsistsofmainlysmoothmusclefibreswithfewelasticfibres.

11. 11
10.LymphoidTissue
Thefluidpassingthroughlymphaticvesselsiscalledlymph.Asarule,lymphfromanypartofbody
passesthroughoneormorelymphnodesbeforeenteringinthebloodstream.Lymphnodesactas
filtersremovingbacteriaandorparticulatematterfromlymph.Eachgroupoflymphnodehasa
specificareaofdrainage.
A)Lymphnode:coveredbyconnectivetissuecapsulecontainingadiposetissue.Afferentspenetrate
capsulearoundtheconvexsurfacewhileefferentscomeoutfromconcavehilum.Internal
structureshowscortexandmedulla.Cortexispackedwithlymphocytes.Cortexconsistsof
lymphaticfollicles(nodules)withgerminalcentre.Medullaconsistsofmedullarycords.
B)Spleen:doesnotshowcortexandmedulla.Consistsofwhitepulpandredpulp.Whitepulp
consistsoflymphaticnodules,whichmayshowthegerminalcentre.Intheredpulpthereare
sinusoidslinedbylongnarrowendothelialcellsshowingslits.Redpulpbetweentwosinusoidsis
likeacordsocalledBillrothcords.
C)Thymus:Thisisalymphoidorganshowingcortexandmedullabutnogerminalcentre.Eachlobe
hasacapsule,whichdividesthelobeintolobules,butdivisionisincomplete.PresenceofHassaI's
corpusclesisthemainfeatureofslide.
D)Palatinetonsil:Thislymphoidtissueiscoveredbyamucousmembrane.tonsiliscoveredfrom
oralsidebystratifiedsquamousnonkeratinisedepithelium,whichdipsintotheunderlying
lymphatictissuetoform10to20littlepitsorprimarycrypts.

12. 12
11.IntegumentarySystem
Skinistheoutermostcoveringofbody.Itiscomposedoftwomainlayers:epidermisanddermis.
Epidermis:composedofstratifiedsquamouskeratinizedepitheliumanddividedintotwozones.
1.Keratinizedzone:herecellsaredeadordying.
2.Germinatingzone:Proliferationsofcellsaretakingplacetoreplacedeadcellinthiszone.
Dermis:itiscomposedofpapillaryandreticularlayers.
Skin-basallayerofcolumnarcellsrestonabasementmembraneandiscalledthestratumbasale.
Nucleiaredistinctandshowmitosis.Nextlayerisstratumspinosumofpolyhedralcells.Cellsshow
manyspinelikeprocesses.Thirdlayerisstratumgranulosum,whichis2to4cellthick.yshowkerato
hyalinegranulesinthecytoplasm,whichisbasophilicinnature.Fourthlayerisstratumlucidum.
Outermostlayerisstratumcorneumorlayerofkeratin.Herenucleiandcytoplasmicorganelles
disappear.

13. 13
12.GastrointestinalTract
InordinaryEnglishword‘alimentary’means‘pertainingtonourishment’.Theabdominalpartof
alimentarycanalreferredtoasgastrointestinaltract.IngeneralarrangementofGIThasfour
histologicallayers:
1.Mucosa:threelayerscollectivelycalledmucosa(fromintooutside):epithelium,laminapropria,
muscularismucosae.
2.Submucosa:helpinindependentmovementofmucosallayers.
3.Muscularisexterna:mainlyitconsistsofinnercircularandouterlongitudinalmusclefibres.
4.Adventitia/serosa:dependingonlocationoforgan.
Tongue-
Slideofthetongueshowsstratifiedsquamousepitheliumonboththesurfaceswithacoreofstriated
muscleinthecentrecutinalldirections.Epitheliumofonesurfaceiscontinuouswiththatofotherat
tipandsidesofthetongue.Dorsalsurfaceshowsvarioustypesofpapillae.Theepitheliumonventral
surfaceisnonkeratinised.Eachpapillaconsistsofliningstratifiedsquamousepitheliumandacoreof
connectivetissueoflaminapropria.Dependingupontheshape,papillaeareofvarioustypes,filiform,
fungiformandcircumvallate.Tastebudsareseenonthefungiformandcircumvallatepapillae.
Salivaryglands(Exocrine)-Thereare3pairsoflargesalivaryglandsandmanysmallscatteredsalivary
glands.Salivaisamixedsecretionofsalivaryglands.Dependinguponthetypeofsecretoryunit,
salivaryglandsareeitherserous,mucousormixedtype.
1.Seroussalivarygland-
Largetriangularcolumnarcellsrestonabasementmembrane.Smalllumenispresentinthecentreof
eachacinusbutlumenisdifficulttoseeunderlightmicroscope.Thecytoplasmofthebasalaspectof
cellisbasophilicasitisrichinRER.apicalcytoplasmcontainseosinophiliczymogengranuleswhichare
membraneboundvesiclescontainingsecretion.Nucleusofmyoepilialcellisseenaroundthealveolus.

14. 14
2.Mucoussalivarygland-
Mucoussecretoryunitsarepackedwithinalobule.Theyarelargerascomparedtoserousalveoliand
arelinedbysimplecolumnarcellsrestingonabasementmembrane.Mucouscellsarepalestaining
becausemucousiswashedduringstaining.Lumenislargerandeasilyseenwhilethenucleiareflat
nearbasementmembrane.
Demiluneishalf-moonshapedclusterofseroussecretingcellsaroundamucoussecretoryunit.
Esophagus-
ItshowsfourbasiclayersofGITbutthespecificfeaturesarestratifiedsquamousepitheliumand
presenceofsubmucosalglands.
Stomach-wallofthestomachalsoshowsfourbasiclayersofGIT.Histologicalstructureandfeatures
ofthefirstlayeri.e.mucousmembranediffersatfundic/bodypartandatpyloricpartofstomach.
StomachFundusorBodyT.S.-Liningofthestomachissimplecolumnar(nonciliated)epitheliumand
mucoussecretingcolumnarcells.Liningepitheliumdipsatplacesintolaminapropriatoformgastric
pits.Atbottomofthepits,gastricglandsopen.Eachpitreceivesopeningofmanyglands.Villiare
absent.
(i)Mucouscells-thesearecolumnarcellswithbasalnucleusandapicaleosinophilicvacuolated
cytoplasm,theysecretemucous.
(ii)Chiefcells:cytoplasmisbasophilicinthebasalpartbecauseofwhichthesecellscanbeidentified,
apicalpartiseosinophilicandcontainssecretoryzymogengranules.Theysecreteenzymes.
(iii)OxynticorParietalcells:-Theyhavedarklystainedpinkcytoplasmandarescatteredinthegland
betweenothercells.Shapeofcellsvary,mayberoundedortriangularwithsphericalnuclei.These
cellssecreteacid.

15. 15
StomachpylorusT.S.-PylorushassamefourbasiclayerofGITasthoseinfundic/bodypartof
stomach.Onlydifferenceisinthemucousmembraneoringlandsproper.Depthofgastricpitandthat
oftheglandsisapproximatelysame.Thisisthefirstfeaturebywhichpyloruscanbedistinguished
fromfundic/bodypart.Secondimportantfeatureisabsenceofprominentparietalcellswhichappear
darkpinktoredwithingastricglands.
Intestine(Duodenum,Smallintestine,LargeintestineandAppendix)-Therearethreepartsofsmall
intestineoutofwhichileumandjejunumarehistologicallysimilarexceptforthenumberandsizeof
villiwhileduodenumischaracterizedbysubmucousglands.
Duodenum:
Duodenumslideshouldbeidentifiedasslideshowingfeaturesofsmallintestineonthebasisof
presenceofvilli.Forconfirmationofduodenumseeforpresenceofglands(Brunner’sglands),in
submucosa.Mucousmembraneshowsmanycircularfoldscoreofwhichisformedbysubmucosa.
Therearenumerousfingerlikeprocessescalledvillithatprojectfromsurfaceintothelumen.Coreof
villusisformedbythelaminapropria.Liningepitheliumissimplecolumnarcontainingcolumnarwith
gobletcells.
Ileum,Jejunum:
Histologicallyileumandjejunumcannotbedifferentiatedexceptfortherelativelygreaternumberof
mucosalfolds,thickerandlargervilli,greatervascularityandfewersolitarysubmucosallymphatic
folliclesinjejunumcomparedtoileum.
LargeintestineT.S.-slideoflargeintestineshowsfourbasiclayersofGlT.Absenceofvilli,absenceof
submucosalglandsandpresenceofmoregobletcellsarethefeaturesbywhichitcanbe
differentiatedfromorpartsofGIT.Itislinedbysimplecolumnarepitheliumcontainingmany
scatteredgobletcells.
Muscularisexternashowsinnercircularmusclesalongwholewalloflargeintestinewhichis
approximatelyuniforminthickness.Howeverouterlongitudinalmusclecoatiscondensedatthree
placestoformtaeniacoli.Betweenthetwotaeniacolithinlayeroflongitudinalmusclemaybeseen.

16. 16
Appendix:
ItshowsallfourbasiclayersofGIT.Mucousmembraneandallorlayersarelikethoseinslideoflarge
intestine.Duetolargesizedlymphaticnodulesmuscularismucosaisnotseenproperlyoris
interruptedsothatnodulesarcseeninlaminapropriaorinsubmucosaorinboth.Germinalcenters
areoftenseeninsenodules.
Liver:
Itshowshepaticlobules,polyhedralorhexagonalinshape.Hepatocytesshowradialarrangementina
lobule.Atthecentreofhepaticlobuleisathinwalledcentralvein.Atperipheryoflobulereisportal
triadconsistingofbranchesofhepaticartery,portalveinandhepaticduct.
Hepaticartery(branch)showsthickwallandregularlumenwhileportalvein(branch)showsthinwall
andlargelumen.Bileduct(tributary)canbeidentifiedveryeasilyasitislinedbysimplecuboidal
epitheliumwithprominentnucleiandeosinophiliccytoplasm.
GallBladder:
ShowsfourlayersbutdifferentfromGITlayers.
1.Mucosaconsistsofsimpletallcolumnarepitheliumwithmicrovilli(brushborder).Laminapropriais
presentbutmuscularismucosaisabsent.
2.Secondlayerconsistsofmuscularisexternacoatofsmoothmuscle.
3.Thirdlayeroforganissubmuscularcoat.
4.Fourthlayerisserosaononesideandadventitiaonhepaticside.
Pancreas:Itisbothexocrineandendocrineinfunction.Exocrinepartismostlylikeparotidorserous
salivaryglands.Endocrinepartisinformofsmallislandsbetweentheexocrineacini.
capsulesendsseptainsideglandanddividesglandintolobules.Secretorycellsarepyramidalandcell
boundariesarenotalwaysdistinctwhilelumenishardlyseen.Endocrinepartofpancreasisseenas
paleareaslargerthananacinuscalledisletsofLangerhans.yarenon-capsulatedcordsandirregular
clumpsofcellsandcapillaries.
Intercalatedductsarelinedbysimplesquamoustosimplecuboidalepithelium,intralobularductsare
linedbysimplecuboidaltolowcolumnarepithelium,whileinterlobularductsarelinebysimple
columnarepithelium.

17. 17
13.RespiratorySystem
Respiratorysystemconsistsoflungandpassagethroughwhichairreachesthem.Thepassagehas
somefeaturesincommon.Theirwallshaveaskeletalbasismadeupofvariablyofbone,cartilageand
connectivetissue.Skeletalbasiskeepspassagealwayspatent.Smoothmusclepresentinthewallof
tracheaandbronchimakealterationinsizeoflumen.Interiorofpassageislinedinmostofitsextent
bypseudostratifiedciliatedcolumnarepithelium.Thisepitheliumiskeptmoistenedbysecretionof
glands.Numerousgobletcellsandmucousglandscovertheepitheliumwithaprotectivemucoid
secretionthatservestotrapdustparticlespresentininhaledair.Deeptomucosa,presenceof
numerousbloodvesselsservetowarminspiredair.
A)Epiglottis-Aslideshowingelasticcartilagelinedoneithersidebyamucousmembraneisslideof
epiglotis.Lip,tongue,eyelidareotherslideslinedbymucousmembraneoneithersidebutnone
ofthemshowselasticcartilageinside.Perichondriumoftheelasticcartilageiscontinuouswith
laminapropriaonbothsides.Anteriorsurfaceshowsstratifiedsquamousnonkeratinised
epithelium.
B)Trachea-islinedbypseudostratifiedciliatedcolumnarepitheliumwithgobletcells.Hyaline
cartilageisdeeptosubmucosacoveredbyperichondrium.Trachealisisasmoothmusclebundle
transverselyarrangedextendingbetweenendsof'U'shapedcartilageonposteriorside.Tracheal
glandsarealsopresentdeeptoTrachealismuscle.Outsidecartilagethereisadventitiacontaining
collagenfibres,adiposetissueandbloodvessels.
C)Lung-Lungisdividedintolobuleswhichareseparatedbyfibroussepta.Lungiscoveredbypleura
whichshowsurfacesimplesquamousepitheliumwithsmallamountofsubepithelialconnective
tissue.slideshowsmanyemptyspacessomecommunicatingwitheachorandwallofsespacesis
thinandpinkinstaining.Bronchiolesareseencutinvariousplanesinsection.Respiratory
bronchiolesopenintoalveolarductwhichfurthercontinuesintoalveolarsacsandalveoli.seare
spacesofvariousordersandshapesthatexistinahugeelasticspongelikearrangementof
capillarybeds.alveolarductsarelongbranchinghallwaysalongwhichrearemanyopendoors.

18. 18
14.UrinarySystem
Urinaryorgansarekidneys,ureter,urinarybladderandurethra.Theseorgansareresponsiblefor
production,storageandpassingofurine.Urineproductionandcontrolofitscomposition,isfunction
ofkidneys.Urinarybladderisresponsibleforstorageofurineuntilitisvoided.Theureterandurethra
aresimplepassagefortransportofurine.
Soallorganshavedifferentmodificationaccordingtotheirfunction.Buturinaryepitheliumis
transitionalepithelium.Uriniferoustubuleisstructuralandfunctionalunitofkidney,whichconsistof
nephronandacollectingductsystem.
A).Kidney-Nephronisastructuralandfunctionalunitofakidney.Kidneyiscoveredbyfibrous
capsulefromallsidesandcoronalsectionshowsoutercortexandinnermedulla.
NephronshowsBowman'scapsule,proximalanddistalconvolutedtubulesandloopofHenle.Apart
fromnephronthereareglomeruliandcollectingducts.Aglomerulusisatuftofcapillaries.Cortexis
pink,granular,darklystained,whilemedullaislightlystainedandstriatedinappearance.Aconical
pyramidofmedul1arysubstancetogetherwithcapofcorticalsubstancethatcoversitsbase
constitutesalobeofkidney.
Cortexcontainsallglomeruliandallproximalanddistalconvolutedtubules(PCT&DCT).Medulla
showsloopofHenleandcollectingtubules,allrunfairlystraightcourses.
PCTislinedbysimplecolumnartosimplecuboidalcellswithcentralprominenteuchromaticnucleus
anddark(pink)eosinophiliccytoplasm.thesecellsshowprominentbrushborderonluminalsideand
verticalstriationsonthebasalside.Cellsarelargeinsizesothatnucleiareseenawayfromeachor
andarefewinnumberliningthelumen.DCThasaprominentlumenlinedbysimplecuboidal
epithelium.
B).UreterT.S.-Thisisatubularstructurewithmusclewallandcanbeeasilydistinguishedfrom
appendix,vasdeferens,fallopiantubeetcbythepresenceofurothelium.Uretericwallshowsthree
layers.Innermostlayerismucousmembrane,whichshowsepitheliumandlaminapropria.Mucous
membraneisthrownintofoldssothatlumenisstarshapedinT.S.
C).UrinaryBladder-Itshowssamethreelayerslikethatoftheureter.lumenislinedbytransitional
epithelium,whichcanbestretchedwithoutbeingdamaged.stretchedepitheliumisthinnerandcells
areflattened,whilerelaxedepitheliumshowsumbrellalikecells.Secondlayerofbladderissmooth
muscle(Detrusor)layershowinginnerlongitudinal,outercircularandoutermostlongitudinallayer.
Thirdandlastlayerisadventitiaofconnectivetissueorserosa.

19. 19
15.MaleGenitalSystem
Malereproductiveorgansaretestis,epididymis,ductusdeferens&seminalvesiclesallpaired,while
prostate,maleurethraandpenisareunpaired.Testesproducemalegametesorspermatozoa.Other
accessorysexorganshelpintheirmaturation,storage,nourishmentandejaculation.
Testis:Enclosedinathickconnectivetissuecapsule-TunicaAlbuginea.Fibrousseptadividethetissue
intolobulescontainingseminiferoustubules.Thesearelong,convolutedandlinedbygerminal
epithelium.
Thisepitheliumcontainstwotypesofcells:Germinalcells-spermatogeniccellsinvariousstagesof
maturationandproducespermsandsupportingcells-Sertolicellsnourishthedevelopingsperms.
LocatedinconnectivetissueareinterstitialcellsofLeydigwhichsecretetestosterone.
Ductusdeferens:Exhibitsnarrowandirregularlumenwithlongitudinalfolds.Thelumenislinedby
pseudostratifiedcolumnarepitheliumwithstereocilia.Ductusdeferensismusculartubeandit
consistsof3layers:innerlongitudinal,middlecircular,outerlongitudinal.Theoutermostlayerisof
adventitia.
Epididymis:islongconvolutedtubulelinedbypseudostratifiedcolumnarepithelium(tallcolumnar
cellswithstereocilia,smallbasalcells).Incutsection,tubulesofepididymisaresurroundedbyathin
layerofsmoothmusclefibres.
Prostate:isafibro-musculo-glandulartissuewithglandssurroundedbyfibromuscularstroma.
Cutsectionofprostateglandshowsglandularacini(simplecolumnar,lightstained),lumenbeingwide
&generallyirregular.Excretoryductsresembleaciniwithsimplecolumnarepitheliumbutcellsstain
darker.Thelumenofacinicontainssphericalconcretionscalledcorporaamylaceaoramyloidbodies.
Seminalvesicle:showshighlyconvolutedandirregularlumen.Cutsectionshowsprimaryand
secondarymucosalfolds.Theepitheliumislowpseudostratifiedtolowcolumnarorcuboidal.Muscular
layerconsistsofinnercircular,outerlongitudinalmusclelayer.

20. 20
Penis:Cutsectionshowstwodorsalcorporacavernosaandsingleventralcorpusspongiosumshowing
cutsectionofpenileurethra(pseudostratifiedorstratifiedcolumnarepithelium).All3aresurrounded
bydeeppenile(buck’s)fasciawhichinturnissurroundedbyconnectivetissueandepidermis.

21. 21
16.FemaleGenitalSystem
Femalereproductiveorgansarerightandleftovaries,uterinetubes,uterus,vaginaandmammary
gland.
1.Ovary:Surfaceiscoveredbysinglelayeroflowcuboidalgerminalepithelium(misnomer).Ovary
isdividedintoperipheralcortexandcentralmedulla.Numerousovarianfolliclesatvariousstages
ofdevelopmentnamelyprimordial(mostnumerous),primary,secondary&maturefolliclesare
locatedinthestromaofcortex.Thelargestfollicleismaturefolliclewhichconsistsofthecainterna,
thecaexterna,granulosacells,alargeantrumwithfollicularfluid,andcumulusoophorus
containingprimaryoocyte.
2.Uterinetube:Extensivemucousfoldsformanirregularlumeninuterinetube.Thelining
epitheliumissimplecolumnar(ciliatedandnon-ciliated).Muscularisexternaconsistsofinner
circularandouterlongitudinallayers.Outermostlayerisserosa.
3.Uterus:Consistsofthreelayers,innerendometrium,middlelayerofsmoothmusclemyometrium
andouterserouslayerperimetrium.Endometriumislinedbysimplecolumnarepithelium.Lamina
propriaisthickwithsimpletubularglandsandstroma.Endometriumisdividedinto2layers-
stratumfunctionalisandstratumbasalis.Inproliferativephase,glandsarestraightandarteriesless
coiled.Insecretoryphase,glandsbecomeconvolutedandarterieshighlycoiled.Myometrium
consistsofthicklayerofsmoothmuscle.Perimetriumisouterserouscoat.
4.Vagina:wallofvaginaconsistsofmucosawithstratifiedsquamousnonkeratinizedepithelium,
smoothmusclelayerandadventitia.
5.Placenta:showscrosssectionofvilli.Villusconsistsofthinsynctiotrophoblasticcells,basement
membraneandendothelialcellsoffetalcapillaries.
6.Mammarygland:compoundtubulo-alveolarglandconsistingmanylobes.Cutsectionshows
manyalveoli-simplecuboidalepithelium,intraandinterlobularducts.Stromaconsistsofadipose
tissue.
7.Umbilicalcord:consistsofmyxomatousconnectivetissuesurroundingtwoumbilicalarteries,
oneumbilicalvein.

22. 22
17.EndocrineGlands
Endocrinetissueismadeupofcellsthatproducesecretionwhichisdistributeddirectlyintoblood.
Secretionsofendocrineglandiscalledhormone.Endocrinetissues/glandsarehighlyvascular.
Secretorypoleofanendocrinecell/tissueorglandistowardsthewallofcapillary(orsinusoid).
Endocrinecellsaredistributedinthreedifferentways:
1.Someorgansareentirelyendocrineinfunctioncalledasendocrinegland.
2.Groupsofendocrinecellsmaybepresentinorgansthathaveotherfunctioneg:isletsof
pancreas,interstitialcellsoftestis.
3.Isolatedendocrinecellsmaybedistributedintheliningepitheliumoforgan.Suchcellsare
seenmostlyingastrointestinaltract.Thesewidelydistributedcellsaregroupedtogetheras
neuroendocrinesystem/APUDcellsystem.
ThyroidGland:iscoveredwithcapsule.Slidewillshowcutsectionsoffollicleswithsquamousto
lowcuboidaltocolumnarepitheliumdependingonfunctionalstatusofgland.Inconnectivetissue
thereareparafollicularcells.
Parathyroidgland:slideconsistofchiefcells(small&darkstaining)andoxyphilcells(lightstaining)
Pituitarygland:consistsofcapsuleandparenchyma
Adenohypophysis—parsdistalisconsistsofchromophils(acidophils,basophils),andchromophobes.
Parsintermediaconsistsoffolliclesfilledwithcolloidsubstance.
Neurohypophysis—consistsofunmyelinatednervefibresandpituicytes.
Adrenalgland:consistsofcortexandmedulla
Cortexconsistsofthreezones
Zonaglomerulosa—showssmallcells(pyramidalorcolumnar)arrangedinovoidclusters.
nucleiaresphericalandstainintensely.
Zonafasciculata—largepolyhedralcellslinedinlongstraightcords1-2cellthickwithsinusoidal
capillariesinbetween.Lightlystainednucleiareseen.
Zonareticularis-showssmallercellswithdeeplystainednucleiarrangedinanastomoticcords.
Medulla—largepalestainingepitheloidcells(chromaffincells)whicharemodifiedneuronswithalotof
sinusoidalcapillaries.

23. 23
18.Specialsenses
A)Cornea:thicktransparent,non-vascularstructureofeye.
Hasfivelayers-
1.Epitheliumisstratifiedsquamousnonkeratinized
2.Anteriorlimitingmembraneorbowman’smembrane(collagenfibres)
3.Cornealstromaconsistsofsubstantiapropria,collagenfibresandfibroblasts
4.PosteriorlimitingmembraneorDesmet’smembrane(collagenfibres)
5.Posteriorepitheliumissimplesquamousorcuboidal
B)Retina:innermostcoatofeyeball
Tenlayers—
1.Pigmentcellepithelium—cuboidal,melanin
2.Layerofrodsandcones
3.Outerlimitingmembrane
4.Outernuclearlayer—nucleiofrodsandcones
5.Outerplexiformlayer
6.Innernuclearlayer
7.Innerplexiformlayer
8.Layerofganglioncells
9.Layerofopticnervefibres
10.Innerlimitingmembrane

24. 24
19.NervousSystem
A)CerebellarCortex-Cerebellumconsistsofinnergrey,outerwhiteandoutermostgrey.
Outermostgreymatteriscalledcortex.Itisveryeasytoidentifybecauseofaseriesofdeeply
convolutedfoldsorfoliasupportedbyabranchingcentralmedullaofwhitematter.Cortexhasthree
layers.Theyareuniformindistributionsocalledashomotypical.
Molecularlayer:Itcontainsrelativelyfewneuronsandlargenumberofunmyelinatednervefibres.It
isoutermostlayercoveredbypiamater.Stellateandbasketcellsareseen.
Purkinjecelllayer:Itisasinglehugeneuronallayerlocatedatthejunctionbetweenothertwolayers.
Thisisacharacteristicneuronpresentonlyincerebellum.
Granularcelllayer:Itisextremelycellularmorenucleilayer.ItcontainsgranularandGolgineurons.
B)Cerebralcortex(LP)-Therearesixlayersofisocortex.Thereisnoclearcutdemarcationbetween
endofonelayerandstartingofthenextlayer.
Molecularlayer-Outermostlayerlinedbypiamater.Itshowsfewnucleiofhorizontalcells.
Outergranularlayer-containsmanygranule(stellate)cellsandfewsmallsizedpyramidalcells.
Outerpyramidallayer-containsmanypyramidalcellsandfewgranulecells.
Innergranularlayer-containsmanygranulecells.Itisdenselypopulatedbyneurons.
Innerpyramidallayer-Largesizedpyramidalcellsareseeninthislayer.
Polymorphlayer-ItisthelastlayeratgreywhitejunctionandshowsnucleioffusiformandMartinotti
neurons.
C)Dorsalrootganglion:aggregationsofneuralcellbodieslocatedoutsideCNS.Consistsofpseudo
unipolarneurons.cellbodyislargeandrounded,nucleusiscentralwithprominentnucleolus.
neuronslieingroups.Satellitecellsarecuboidalinshapearoundcellbodies.
D)SympatheticGanglion:Neuronsofsympathetictrunkaremultipolar,smallerinsize,nucleusis
eccentricallyplacedwithprominentnucleolus.Satellitecellsarefew.

25. 25
Appendix
20.Chartsforidentificationofslides
Firstofall,wecategorizeslidesintothreegroups
Group1
Solid/Basic:forexample-connectivetissue,bones,cartilagesandmuscles.
Group2
Hollow/Tubular:itincludesorgans,whichhavelumenandwall.Forexample-bloodvessels,trachea,
bronchus,oesophagus,stomach,intestine,gallbladder,ureter,urinarybladder,epididymis,vas
deferens,seminalvesicles,uterusanduterinetubes.
Group3
Nonspecific:(Nontubularandnonsolidtissue)examples-Lymphoidtissue,endocrineglands,exocrine
glands,prostate,mammarygland,cerebellum,cerebrum,epiglottis,lungtongue,liver,kidney,testes,
ovary,penis,cornea,retina,skin,placentaumbilicalcord.
Wenowhavetodeterminewhereagivenslidebelongstogroup1,2or3.Forthisseetheslideunder
lowpowerobjectivelens.
Ifthegivenslideshowshomogenicityofstructurewithpredominanceoftheircelltype,fibretypeor
both,thenslideisofgroup1i.e.Basictissue.Forexample-ifchondrocytesarepresent,nslideisof
cartilageandifmusclefibrenmuscle.
Ifgivenslideshowslumenandawall,thenitistubularstructure.Butiforganislargeandlumenisnot
seenonslideinsuchacaseseebothsurfacesofgiventissue.Ifgiventissueshowsaliningepithelium
(whatevermaybetype)ononeside,andoppositesideshowsfibrousorserouscoatthenalsoslideis
ofatubularstructure.Forexample-uterus-ononesidehascolumnarepitheliumandopposite
surfaceshowsfibrousadventitia.
Ifgivenslidedoesnotshowfeaturesmentionedabovethenslidebelongstogroup3.Nontubularand

26. 26
non-solidtissue.Forexampleepiglottisononesurfacehasstratifiedsquamousepitheliumand
oppositesurfacealsoshowssameepithelium.

27. 27

28. 28

29. 29

30. 30

31. 31

32. 32
C)Ifslideshowsacentralcoreandtwosurfacesorconicalstructurethensee
Centralcore Onesurface Orsurface Name
Elasticcartilage Stratifiedsquamous
epithelium
Stratifiedsquamous
epitheliumor
pseudostratifiedcolumnar
epithelium
Epiglottis
Skeletalmuscleand
condensed
connectivetissue.
Skin Simplecuboidalorsimple
columnarepithelium
Eyelid
Irregularlyarranged
skeletalmuscle
Stratifiedsquamous
epitheliumwithpapillae
Stratifiedsquamous
epitheliumwithoutpapillae
Tongue
Hyalinecartilage Pseudostratified
columnarepithelium
Pseudostratifiedcolumnar
epithelium
Nasalseptum
D)Ifslidedoesnotshowanyofabovefeaturesnseeforfollowing
Lungs:Emptyspacesshowinghoneycombedappearancelinedbysquamousepithelium.Bronchiand
Bronchiolearepresent.
Liver-Hexagonallobularpatternfilledwithradiatingcordsofcells.Portaltriadsarepresentatanglesof
lobules.
Kidney-CortexandMedullapresent.CortexcontainsMalphigianorrenalcorpusclesandtubuleswith
ill-definedlumen.Medullacontainstubuleswithwell-definedlumen:
Testes-Tubulescutindifferentplanesi.e.ofirregularshapeandlinedbyseverallayersofcells.Lumen
containsspermatozoa.
Ovary-Ovarianfolliclesatdifferentstagesofdevelopmentincortexi.e.towardsperipheryandblood
vesselswithconnectivetissueincentralmedulla.
Skin:Showsdermisandepidermis.Epidermis-Keratinisedstratifiedsquamousepithelium.Dermis-
Connectivetissue,sweatglandandsebaceousgland.Ifhairfolliclesareabsent-Thickskin.
CerebralCortex-Laminarpatternofneuronsandfibres.Pyramidalcellsofdifferentsizesseen.
Cerebellarcortex:-Laminatedpatternofneuronsandfibres.Showsthreelayers.Purkinje(Flask
shaped)cellsseeninasinglerowatequaldistance.
Cornea:-Fivelayeredstructurewiththickcentralcoreformedbycollagenfibresi.e.Substantiapropria
(Homogenousappearance).Ontheirsurfacesreisepithelialcovering.Ononesideitisstratified
squamousepitheliumandorsurfaceislinedbysimplecuboidalorsquamousepithelium.
Retina:Tenlayeredstructure,outofwhichthreelayersareofnucleiinwhichnumberofnucleigoeson
decreasingsuccessivelyfromoutsidetoinside.

33. 33
Placenta:Irregularlycutsmallmassesoftissueseparatedfromeachorbyemptyspaces.Eachmasshas
centralcoreofconnectivetissuecontainingbloodvesselsandcellsliningsurface.
Penis-Threecylindricalmassesoferectiletissuecoveredbyskin.