09.08.08: Epithelium

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CellsandTissuesSequenceMedicalHistology

Epithelium

Fall,2008

[Fr.Tissu,woven;L.texo,toweave]

Atissueisanorganizedaggregationofcellsorgroupsofcellsthatfunctioninacoordinatedmannertoperformoneormorespecificfunctions.Tissuescombinetoformlargerfunctionalunits,calledORGANS.Thus,thetissuesarethebasicfunctionalunitsresponsibleformaintainingbodyfunctions.

Tissues

BASICTISSUES

EpitheliumConnectivetissue

MuscleNervoustissue

Blood

Epitheliumisacohesivesheetofcellsthat:1.Coverstheexternalsurfaceandlinestheinternalsurfaceofthebody.–  Protection(bywithstandingwearandtear,fromhydrationanddehydration)

–  Transport(i.e.O2andC02)–  SelectiveAbsorption:(Controlthemovementofsubstancesbetweentheoutsideenvironmentandtheinternalcompartmentsinthebody.)

–  Secretion(secretorycells)

2.Formsendocrineandexocrinesecretoryglands.

duct

Secretoryportion

Junquueira&Carneiro10thEd.P.82

Junqueira and Carnein 10th Ed. P. 82

EpithelialliningcellsofSkinIntestine

Multiplelayersofflat(squamous)cells Singlelayeroftall(columnar)cellsMichigan Medical School Histology Slide Collection Michigan Medical School Histology Slide Collection

Epithelialcells:1. Formavascularsheetsthatdifferinnumberofcelllayers,shapeofthecells

andstructuralspecializationsofthefree(apical)cellsurface,dependingonthetissuefunction(s).

2. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains.3. Areheldtogetherbyseveralspecializations,knownastheintercellular

junctions,andbindtotheunderlyingconnectivetissueviathebasementmembrane(LM)orbasallamina(EM).

4. Arecapableofrenewalandregeneration. non-specializedepithelium-allcells specializedepithelium-stemcells

Ross/Romrell p. 52



2. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains.3. Areheldtogetherbyseveralspecializations,knownastheintercellular



Ross/Romrell p. 52

ClassificationofEpithelium

(Pseudostratified)

columnar(Respiratory)

Ross/Romrell p. 53

PseudostratifiedEpithelium

Kierszenbaum p.6

Simplesquamousepithelium:endotheliumandmesothelium

Michigan Medical School Histology Slide School Kierszenbaum p.4

Endothelium/Mesothelium(SimpleSquamousEpithelium)

Source Undetermined

SimpleCuboidalEpithelium

Michigan Medical School Histology Slide School Kierszenbaum p.4

SimpleColumnarEpithelium

Michigan Medical School Histology Slide School Kierszenbaum p.4 Source Undetermined

Simplecolumnarepitheliumliningthegutlumen

lumen

Twolayersofsmoothmuscleon

thewallGray’s Anatomy, wikimedia commons

Michigan Medical School Histology Slide School

ApicalCellSurfaceSpecializations-1StriatedBorder(Microvilli)

G

G:gobletcell

G

Sources Undetermined

Microvilli(Coreofactinfilaments)

Darnell et al., Molecular Cell Biology p. 608

Source Undetermined

ApicalCellSurfaceSpecializations–2CiliaontheRespiratoryEpithelialCells

Kierszenbaum p.6

Verhey. Molecular Biology of the Cell, 4th Edition.

Ciliacoreofmicrotubulesin9+2arrangement(axoneme)

cilia

BasalbodiesGobletcells

RespiratoryepitheliumMichigan Medical School Histology Slide Collection Source Undetermined

9+2(Axoneme)

Ross

Dyneinisresponsibleforthesliding.

Alberts et. Al; p 648

Rossetal.,4thed.P.94

DyneinDefectsinImmotileCilia

Source Undetermined

MicrovilliandciliaMicrovilli

Cilia


StratifiedSquamousEpitheliumnon-keratinizedkeratinized

Kierszenbaum pg 5 Kierszenbaum pg 5

StratifiedSquamousEpithelium

Non-keratinized Keratinized

Linesesophagus,oralcavity,vagina… Linesthickandthinskin

Michigan Medical School Histology Slide Collection Michigan Medical School Histology Slide Collection

TransitionalEpithelium(urothelium)

Kierszenbaum pg 6

TransitionalEpithelium(urothelium)

Linestheurinarytract,ureter,bladderandurethra

Source Undetermined



2. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains3. Areheldtogetherbyseveralspecializations,knownastheintercellular



Ross/Romrell p. 52

Whatstructuresholdthecellstogetherandattachesthe

epitheliumtotheconnectivetissue?

Ans.Intercellularjunctions

Basementmembrane(basallamina)

Source Undetermined

Maculaadherens(desmosomes)andIntermediateFilaments

Source Undetermined

MaculaAdherens(desmosome)

Source Undetermined

Boumphreyfr,WikimediaCommons(adapted)

Desmocollins

CellMembranes

Tonofilaments(Keratin

IntermediateFilaments)

IntercellularSpace

Adhesionplaque

(plakoglobin,desmoplakins)

Cell1 Cell2

DesmosomesandIntermediateFilamentsDesmosomesserveas:

1.Spotattachmentsitesforadjacentcellmembranes.

2.Anchoringsitesforintermediatefilaments.

Alberts et al., p. 802

Verhey. Molecular Biology of the Cell, Garland Science 2008

Basementmembrane(basallamina)

Hemidesmosomesfunctiontoanchorepithelialcellstotheconnectivetissueviabasementmembrane(basallamina).

Source Undetermined Michigan Medical School Histology Slide Collection

LossofdesmosomefunctionscauseBlisteringSkinDisorders

Pemphigus:Separationofepidermalcellsfromeachother(acantholysis)causedbylossofdesmosomefunctions.

Bullouspemphigoid:Separationofepidermisfromthedermisduetoblisteringinthebasementmembranecausedbylossofanchoringfilamentsandhemidesmosomes.

Source Undetermined

IntercellularJunctionsJunctionalComplex


Zonulaadherens(intermediatejunction)

Darnell, et. al., p.608 Lady of Hats, Wikipedia

ZonulaadherensMaculaadherens•  Intermediatejunction•  Adheringjunction•  Cadherins•  Linkedtoactinfilaments•  Adhesionbelt

•  Desmosome•  Adheringjunction•  Cadherins•  Linkedtointermediatefilaments•  Spotadheringjunction

ZonulaOccludens(TightJunction)

servesasaSelectivePermeabilityBarrier

Lady of Hats, Wikipedia

Junquueira & Carneiro 10th Ed. P. 82

Source Undetermined

Zonulaoccludens(tightjunction)

Alberts et. Al, p. 794-5

Freeze-fracturepreparation

Alberts et al., p. 795

BloomandFawcettp.67

Nexus(gapJunction)-communicatingjunction

SixConnexinsubunitsassembletoformaConnexon.

Alberts et al., p. 802 Lady of Hats, Wikipedia

GapJunction


Epithelialcells:1. Arestructurallyandfunctionallypolarized:Haveapical,lateralandbasaldomains2. Formavascularsheetsthatdifferinnumberofcelllayers,shapeofthecells


3. Areheldtogetherbyseveralspecializations,knownastheintercellularjunctions,andbindtotheunderlyingconnectivetissueviathebasementmembrane(LM)orbasallamina(EM).


Ross/Romrell p.52

EpitheliumTypes-simple&stratified(pseudostratified)ApicalcellsurfacespecializationsMicrovilli-actinfilamentsCilia-microtubules(dyneins)

IntercellularjunctionsZonulaoccludens(tightjunction)-ridgesandgrooves, sealintercellularspaces-SelectivepermeabilitybarrierZonulaadherens-actinfilaments-celltocelladhesionMaculaadherens(desmosome)-intermediatefilaments -attachmentplaque(spot)Hemidesmosome-attachesepitheliumtobasallaminaNexus(gapjunction)-connexons-celltocell communication

EpithelialcellsformSecretoryGlands

Glands:GroupingsofcellsspecializedforsecretionSecretionistheprocessbywhichsmallmoleculesaretakenupandtransformed,byintracellularbiosynthesis,intoamorecomplexproductthatisthenactivelyreleasedfromthecell.Exocrine(ducts)andendocrine(ductless)glands

SecretoryEpithelialcells

Source Undetermined

DevelopmentofEndocrineandExocrineGlands

Junquiera and Carnein, 10th Ed. P. 82

SecretoryUnitsandGlandularCells

Kim, S.K.

Image of secretory units and glandular

cells removed

TwoSecretoryPathways

Exocytosis

RegulatedSecretion:Secretorygranulesaccumulateincellsandthegranulecontentisreleasedbyexocytosisuponstimulation.

ConstitutiveSecretion:Thesecretoryproductisnotconcentratedintogranulesbutisreleasedcontinuouslyinsmallvesicles.

Kim, S.K.

LearningObjectivesAftertoday’ssession,thestudentsareexpectedto:

1. Beabletoclassifyepitheliaandidentifyeachtype.2.  Recognizefourtypesofintercellularjunctionsandhemidesmosomesattheelectronmicroscopelevelandknowtheirfunctions.

3.  Identifytheapicalspecializationsandknowtheirfunctions.

4. Beabletocorrelatedifferenttypesofepitheliatotheirfunctionsandknowwhereinthebodyeachtypeoccurs.

5. Knowhowspecializedandnon-specializedepithelialcellsarerenewed.

6. Knowhowexocrineandendocrineglandsformandbeabletorecognizesecretorycells.

AdditionalSourceInformationformoreinformationsee:http://open.umich.edu/wiki/CitationPolicy

Slide 6: Junqueira and Carnein 10th Ed., pg 82

Slide 7: Michigan Medical School Histology Slide Collection

Slide 8: Ross/Romrell p.52



Slide 11: Kierszenbaum p.6

Slide 12: Michigan Medical School Histology Slide Collection; Kierszenbaum p.4

Slide 13: Source Undetermined

Slide 14: Michigan Medical School Histology Slide Collection; Kierszenbaum p.4

Slide 15: Source Undetermined; Michigan Medical School Histology Slide Collection;

Kierszenbaum p.4

Slide 16: Michigan Medical School Histology Slide Collection; Gray’s Anatomy,

Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Gray1056.png

Slide 17: Source Undetermined; Source Undetermined

Slide 18: Darnell et al., Molecular Cell Biology p. 608; Source Undetermined

Slide 19: Kierszenbaum p.6; K. Verhey

Slide 20: Michigan Medical School Histology Slide Collection; Source Undetermined

Slide 21: Ross

Slide 22: Rossetal.,4thed.P.94;Ross; Alberts et al., pg 648



Slide 25: Kierszenbaum; Kierszenbaum

Slide 26: Michigan Medical School Histology Slide Collection

Slide 27: Kierszenbaum, pg 6





Slide 32: Source Undetermined; CC BY Boumphreyfr,

http://commons.wikimedia.org/wiki/File:Cell_junctions.png, CC:BY-SA 3.0, http://creativecommons.org/licenses/by-sa/3.0/

Slide 33: Verhey. Molecular Biology of the Cell, Garland Science 2008; Alberts et al., p. 802

Slide 34: Michigan Medical School Histology Slide Collection; Source Undetermined



Slide 37: Lady of Hats, Wikipedia, http://commons.wikimedia.org/wiki/File:Adherens_Junctions_structural_proteins.svg; Darnell, et. al.,

p.608

Slide 39: Lady of Hats, Wikipedia, http://commons.wikimedia.org/wiki/File:Cellular_tight_junction_en.svg; Source Undetermined;

Junquueira & Carneiro 10th Ed. P. 82

Slide 40:Alberts et. Al, p. 794-5;

Slide 41: Alberts et al., p. 795; Bloom and Fawcett p. 67

Slide 42: Alberts et al., p. 802;

Lady of Hats, Wikipedia, http://commons.wikimedia.org/wiki/File:Gap_cell_junction_en.svg




Slide 48: Junquiera and Carnein, 10th Ed. P. 82

Slide 49: Sun-Kee Kim

Slide 50: Sun-Kee Kim

Education

09.08.08: Epithelium