Epithelium

EpitheliumEpitheliumEpitheliumEpithelium

Michael Hall PhDMichael Hall PhDMichael Hall PhDMichael Hall PhD

University of CaliforniaUniversity of CaliforniaLos AngelesLos Angeles

University of CaliforniaUniversity of CaliforniaLos AngelesLos Angeles

Features common to all epitheliaFeatures common to all epithelia

1.1.The cells are closely packed togetherThe cells are closely packed together2.2.The cells are polarizedThe cells are polarized3.3.The apex always faces an open spaceThe apex always faces an open space4.4.The base always sits on a basement membraneThe base always sits on a basement membrane

Epithelial cells are closely packedEpithelial cells are closely packed

Free Surface

Lamina propria

Epithelial cells always have a free surfaceEpithelial cells always have a free surfaceand sit on a basement membraneand sit on a basement membrane

EpitheliumEpithelium

BasementBasementmembranemembrane

EpitheliumEpithelium

BasementBasementmembranemembrane

Note that both of theNote that both of theepithelia face a free surface epithelia face a free surface

Types of Types of EpitheliumEpithelium

SimpleSimpleOne cell layerOne cell layer

StratifiedStratifiedMore thanMore than

one cell layerone cell layer

Types of Types of EpitheliumEpithelium

1.1. Simple Simple squamoussquamous

2.2. Simple cuboidalSimple cuboidal3.3. Simple columnarSimple columnar

4.4. Stratified squamousStratified squamous5.5. Stratified cuboidalStratified cuboidal6.6. Stratified columnarStratified columnar

7.7. PseudostratifiedPseudostratified8.8. TransitionalTransitional

Simple squamous epitheliumSimple squamous epithelium

Basement membraneBasement membrane

Connective tissueConnective tissue

Free spaceFree space

Simple squamous epithelium Simple squamous epithelium (endothelium)(endothelium)

lining an arteriolelining an arteriole

endothelium

Simple cuboidal epithelium (kidney)Simple cuboidal epithelium (kidney)

Free surface

Basement membranes

ssq

ssq

ssq

scu

scu

scu

scu*

Simple epithelia in kidney medullaSimple epithelia in kidney medulla

Simple columnar epithelium (duodenum)Simple columnar epithelium (duodenum)

Stratified Squamous Epithelium (cornea) Stratified Squamous Epithelium (cornea)

bm

ct

free surface

Stratified Squamous Epithelium Stratified Squamous Epithelium

free surface

basement membrane

squamous cells

Stratified Cuboidal Epithelium Stratified Cuboidal Epithelium

Duct of sweat glandDuct of sweat glandBasement membraneBasement membrane

Connective tissueConnective tissue

Stratified Columnar Epithelium (urethra) Stratified Columnar Epithelium (urethra)

lplp

bmbmColumnar cellsColumnar cellsColumnar cellsColumnar cells

PseudostratifiedPseudostratifiedEpitheliumEpithelium

Basement Membrane

Pseudostratified Columnar EpitheliumPseudostratified Columnar Epithelium(duodenum)(duodenum)

Basal cells

Transitional EpitheliumTransitional Epithelium(Urinary system)(Urinary system)

Transitional Transitional Epithelium Epithelium ((relaxedrelaxed -top layer -top layer of cells is cuboidal)of cells is cuboidal)

Transitional Transitional EpitheliumEpithelium((stretchedstretched-top layer -top layer of cells is squamous)of cells is squamous)basement membrane

basement membrane

MesotheliumMesothelium

endothelium EndotheliumEndothelium

Mesothelium is the name given to the simple squamous epithelium that lines the closed cavities of the body

Basement membranesBasement membranes

Simple squamous epitheliumSimple squamous epithelium

Basement membraneBasement membrane

Connective tissueConnective tissue

Basement Membrane of epitheliumBasement Membrane of epithelium

Molecular structure of extracellular matrixMolecular structure of extracellular matrix forming the basement membraneforming the basement membrane

Inside of cellInside of cell

Junctional ComplexesJunctional Complexes

‘‘Terminal Bars’ between epithelial Terminal Bars’ between epithelial cellscells

Epithelial Epithelial Junctional Junctional ComplexComplex

Z. occludens

Z. adherens

Desmosome

Cell 1Cell 1 Cell 2Cell 2

Components of the Components of the Epithelial Junctional Epithelial Junctional

ComplexComplex

1.1. Z. occludensZ. occludens2.2. Z. adherensZ. adherens3.3. Macula Macula

adherensadherens(desmosome)(desmosome)

4. Gap junction4. Gap junction5. Hemidesmosome5. Hemidesmosome

1

2

3

45

GeneralizedGeneralizedStructure ofStructure ofa Junctionala JunctionalComplexComplex

Cell 1Cell 1 Cell 2Cell 2

< 1,500 Da

> 1,500 Da

Connexon 2Connexon 1

Gap Junction

Surface Specializations ofSurface Specializations ofEpithelial CellsEpithelial Cells

Myosin

Actin

Spectrin

Structure of a Structure of a microvillusmicrovillus

Fimbrin

Villin

Stereocilia in the EpididymisStereocilia in the Epididymis

StereociliaStereocilia

Cilia in the Respiratory MucosaCilia in the Respiratory Mucosa

CiliaCilia

ciliacilia

microvillimicrovilli

Basement membrane

Mucosa

Components of a MucosaComponents of a Mucosa

The EndThe End

Whoopee Whoopee !!!!