HISTOLOGY

HumanAnatomyUnit1

InAnatomyToday

Histology• Studyoftissues• Tissues=agroupofcellsperformingacommonfunction

• Microscopicanatomy• Includeshowdifferenttissuesarearrangedtoformorgansandotherstructures

Ductusepididymis

TissueSections

LongitudinalsectionsTransverseorcrosssection

TissueSections

4TissueTypes

• 4Typesoftissue– Epithelialtissue– Connectivetissue– Nervoustissue–Muscletissue

• CharacteristicDifferences– Proportionofcellstomatrix–Matrixcomposition– Cellfunction

EpithelialTissue• Composition– Oneormorelayersofcloselyadheringcells– Apicalsurfaceandbasalsurface– Restonabasementmembrane– Supportedbyconnectivetissues

• Function– Coverorgansurfaces– Formsecretorytissue– Formductsofglands

Classification

• Criteria– Numberofcelllayers– Morphologyofthesurfacecells

• Twomajorcategories– Simple(onelayer)– Stratified(twoormorelayers)

CellShape

• Squamous

• Cuboidal

• Columnar

• Acinar

SimpleEpithelia

• General– Allcellstouchbasementmembrane• Exception:Pseudostratifiedcolumnar

• Categories– Simplesquamous– Simplecuboidal– Simplecolumnar– Pseudostratifiedcolumnar

SimpleEpithelia

SimpleSquamousEpithelium

SimpleCuboidalEpithelium

SimpleColumnarEpithelium

• Foundin– Stomach– Smallintestines– Colon– Appendix

• Singlelayerofcells• Nucleiuniformlyarranged

GobletCellEpithelium

• Simplecolumnarepitheliumwithnumerousgobletcellspresent

• Gobletcellsproducemucus

• Foundin:– Smallintestine– Colon

PCCE

• Pseudostratifiedciliatedcolumnarepithelium

• Singlelayerofcells• Ciliapresentontheapicalsurface

Cilia

Ciliaarecomposedofmicrotubulesandprojectfromtheapicalsurface.Function:tomovethingsacrossthecellsurface

StratifiedEpithelia

• Generalcharacteristics– Upto20ormorecelllayers– Namedforshapeofsurfacecells

• Exception:transitionalepithelium• Stratifiedsquamous– Mostcommon– Exfoliation– Keratinizedtissue(cornified)– Nonkeratinized

StratifiedSquamousEpithelium

• Multiplelayersofcells

• Surfacelayercellsaresquamous

• Foundinareasthatexperiencefriction– Epidermis– Vagina

StratifiedCuboidalEpithelium

• Multiplelayersofcuboidcells

• Surfacelayerofcellsarecuboidal

• Foundin– Largeductsofglands

• Sweatglands• Pancreas

TransitionalEpithelium• Foundinsecretory

portionsoftheurinarysystem– Calyces– Ureters– Urinarybladder

• Distensibletissue(stretches)

• Epithelium“transitions”fromcuboidaltoalmostsquamousinappearanceastissuedistends

ConnectiveTissue

• Lesscells,moreECF(groundsubstance)• Variable,widelydistributed,mostabundant• Threecategoriesofmaturetissue– FibrousCT– SupportiveCT(bone,cartilage)– FluidCT(blood)

ConnectiveTissueFunctions

• Bindsorgans• Support• Protection– Physical– Immune

• Movement• Storage• Heatproduction• Transportation

FibrousConnectiveTissue:Components

• Cells– Fibroblasts–Macrophage– Leukocytes– PlasmaCells–MastCells– Adipocytes

• Fibers– Collagenous– Reticular– Elastic– Groundsubstance

TypesofFibrousConnectiveTissue

• LooseCT– Lotsofgroundsubstance

– Types• Areolar• Reticular• Adipose

• DenseCT– Fiberispredominantcomponent

– Types• Denseregular• Denseregularelastic• Denseirregular

AreolarConnectiveTissue• Cells

– Allsixtypes• Matrix

– Predominatelycollagenous– Someelastic/reticular

• General– Veryvascular– Looselyorganized– Varied– Underliesalmostallepithelial

tissue• Theseimagesareof

mesentery

ReticularConnectiveTissue

• Reticularfibersandfibroblasts

• Providessupportingframework(stroma),networkorlattice

• Found– Spleen– Lymphnodes– Thymus– Bonemarrow

AdiposeTissue

• Adipocytesmostabundantcelltype

• SupportedbyareolarCT,reticularCT,bloodvessels

• Function:– Energystorage– Insulates– Supports– Cushionsshock

• Whitefatvs.Brownfat

DenseRegularConnectiveTissue

• “regular” arrangementoffibroblastandcollagenfibers– Closelypackedparallelcollagenfibers+fibroblasts

– Formbundlesofcollagenfibers

• Foundintendons

DenseRegularElasticConnectiveTissue

• Largeamountofelasticfibersinparallelarrangement

• Elasticfiberscanstretch1½timestheirlengthandthenrecoil

• Provideselasticity• Found

– Ligaments– Largearteries– Bronchialtubes

DenseIrregularConnectiveTissue

• Collagenfibersinrandomarrangement+fibroblasts

• Found– Reticularlayerofdermis– Protectivecapsulearoundorgans

– Fibroussheetaroundbones,etc.

• Similartoareolar,butless“open” space

Cartilage

• Flexiblematrix• Avascularexceptwhentransformingtobone

• Externalear,tipofnose,larynx

• Cells– Chondroblasts

• secretematrix

– Chondrocytes• trappedinlacunae

• Threetypes– Hyaline– Elastic– Fibrocartilage

HyalineCartilage• Matrix

– smooth,frictionless– mixofcollagen,elastin,

chondroitin(aglucosaminoglycan)• Cells

– Cellnests• Usuallycoveredby

perichondrium– DenseirregularCTcovering– innerlayerproducesnew

chondrocytes• Examples:

– Costalcartilage– Nasalseptum– C-ringcartilageof

trachea– Fetalskeleton

ElasticCartilage

• Matrix– Web-likemeshofelastic

fibers– Appearanceoffur

• Perichondriumalwayspresent

• Examples:– Pinnaofear– Epiglottis

Fibrocartilage

• Characteristics– Parallelcollagenfibers– Rowsofchondrocytesinlacunae

– Noperichondrium• Examples– Pubicsymphysis– Intervertebraldiscs– Menisciofthesynovialjoints

SupportiveConnectiveTissue:Bone

CompactBone• Novisiblespaces• Densecalcifiedtissue• Found

– Externalsurfaceofallbone– Shaftsoflongbones

• Tissuearrangedintoosteons– Concentriclayersofmatrix

andosteocytessurroundingacentralcanal

• Periosteum

SpongyBone

• Found– Headsoflongbones– Middlelayerofroofingbonesofskull

• Namedforappearance• Tissuearrangedintotrabeculae(fusionofspicules)

• Bathedinredmarrow

FluidConnectiveTissue:Blood

• Plasma+formedelements

• Erythrocytes• Leukocytes– Neutrophils– Basophils– Eosinophils– Monocytes– Lymphocytes

• Thrombocytes

NervousTissue

• Excitabletissue• Function– Rapidcommunication

• Celltypes– Neurons– Neuroglia

MuscularTissue

• Contractswhenstimulated• Threetypes– Skeletal– Cardiac– Smooth