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Tissues Handouts

Tissues

Groupsofcellssimilarinstructureandfunction Typesoftissues

Epithelial Connective Muscle Nerve

EpithelialTissue

(Epithelium)

Twomaintypes(bylocation):

Coveringandliningepithelia Onexternalandinternalsurfaces

o Glandularepitheliao Secretorytissueinglands

CharacteristicsofEpithelialTissue

Cellshavepolarityapical(upper,free)andbasal(lower,attached)surfaces

Apicalsurfacesmaybearmicrovilli(e.g.,brushborderofintestinallining)orcilia(e.g.,lining

oftrachea)

Noncellularbasallaminaofglycoproteinandcollagenliesadjacent

tobasalsurface

o Arecomposedofcloselypackedcells

o Continuoussheetsheldtogetherbytightjunctionsand

desmosomes

Supportedbyaconnectivetissuereticularlamina(underthebasal

lamina)

o Avascularbut

innervated

o HighrateofregenerationClassificationofEpithelia

Asktwoquestions: Howmanylayers?

o 1=simpleepitheliumo >1=stratifiedepithelium

Whattypeofcell? Squamous Cuboidal Columnar

(If

stratified,

name

according

to

apical

layer

ofcells)

Simpleepitheliaaremostlyconcernedwith

absorption,secretion,andfiltration

Simplesquamousepitheliumisasinglelayerof

fishscaleshapedcells.

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Twootherlocations Endothelium

o Theliningoflymphaticvessels,bloodvessels,andheart

Mesotheliumo Theepitheliumofserousmembranesin

theventralbodycavity

Simplecuboidalepitheliumisasinglelayerof

cubeshapedcellsformingthesmallestductsof

glandsandmanykidneytubules.

Simplecolumnarepitheliumisasinglelayerof

columnshapedcellsthatlinethedigestive

tract.

Pseudostratifiedcolumnarepitheliumcontains

cellsofvaryingheightsgivingthefalse

impressionofthepresenceofmanylayers.

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Stratifiedepitheliasmainfunctionisprotection.

Stratifiedsquamousepitheliumiscomposedof

severallayerswiththecellsonthefreesurface

beingsquamousshapedandtheunderlyingcells

beingcuboidalorcolumnarinshape.

StratifiedCuboidalEpithelium

Quiterareinbody Foundinsomesweatandmammaryglands Typicallytwocelllayersthick

Transitionalepitheliumformstheliningofthe

holloworgans

of

the

urinary

system

that

stretchesastheyfill.

GlandularEpithelia

Aglandisoneormorecellsthatmakesandsecretesanaqueousfluid

Classifiedby: Siteofproductreleaseendocrineor

exocrine

Relativenumberofcellsformingtheglandunicellular

(e.g.,

goblet

cells)

or

multicellular

EndocrineGlands

Ductlessglands Secretehormonesthattravelthroughlymphor

bloodtotargetorgans

ExocrineGlands

Morenumerousthanendocrineglands Secreteproductsintoducts Secretionsreleasedontobodysurfaces(skin)or

into

body

cavities

Examplesincludemucous,sweat,oil,andsalivaryglands

UnicellularExocrineGlands

Theonlyimportantunicellularglandisthegobletcell

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MulticellularExocrineGlands

Multicellularexocrineglandsarecomposedofaductandasecretoryunit Classifiedaccordingto:

Ducttypeo Simpleo Compound

Structureoftheirsecretoryunitso Tubularo Alveolar

o Tubuloalveolar

ModesofSecretion

Merocrine Productsaresecretedbyexocytosis Pancreas,sweatandsalivaryglands

ApocrineGland

Apicalportionofcellpinchedoff Axillary(arpit)andgenitalregions

Holocrine Productsaresecretedbyruptureofglandcells Sebaceousglands

Connective

Tissue

Mostabundantandwidelydistributedtissuetype Fourclasses

Connectivetissueproper Cartilage Bonetissue Blood

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StructuralElementsofConnectiveTissue

Groundsubstance Mediumthroughwhichsolutesdiffuse

betweenbloodcapillariesandcells

Components:o Interstitialfluido Adhesionproteins(glue)o Proteoglycans

Proteincore

+large

polysaccharides

(chrondroitinsulfateandhyaluronic

acid)

Trapwaterinvaryingamounts,affectingtheviscosityoftheground

substance

Collagen(whitefibers) Strongestandmostabundanttype Provideshightensilestrength

Elastic Networksoflong,thin,elastinfibersthatallowforstretch

Reticular Short,

fine,

highly

branched

collagenous

fibers

Cells Maturecells=cytes Cellsthatcreatenewtissue=blasts

o Fibroblastsinconnectivetissuepropero Chondroblastsandchondrocytesincartilageo Osteoblastsandosteocytesinbone

Cellsthatbreakdowntissue=clastso Osteoclastsinbone

ConnectiveTissueProper

Types:

Looseconnectivetissueo Areolaro Adiposeo Reticular

Denseconnectivetissueo Denseregularo Denseirregularo Elastic

Areolarconnectivetissueservestobindbody

parts

together

while

allowing

them

to

move

freelyoveroneanother,wrapssmallblood

vesselsandnerves,surroundsglands,and

formsthesubcutaneoustissue.

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Adipose(fat)tissueisarichlyvascularized

tissuethatfunctionsinnutrientstorage,

protection,andinsulation.

Reticularconnectivetissueformstheinternal

frameworkofthelymphnodes,thespleen,

andthebonemarrow.

Denseregularconnectivetissuecontains

closelypackedbundlesofcollagenfibers

runninginthesamedirectionandmakesup

tendonsandligaments.

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Denseirregularconnectivetissuecontainsthick

bundlesofcollagenfibersarrangedinanirregular

fashion,andisfoundinthedermis.

ConnectiveTissue:Cartilage

Threetypesofcartilage: Hyalinecartilage Elasticcartilage Fibrocartilage

Hyalinecartilage

is

the

most

abundant

cartilage,

providingfirmsupportwithsomepliability.

Elasticcartilageisfoundwherestrengthand

exceptionalstretchabilityareneeded,suchasthe

externalear.(Notshown)

Fibrocartilageisfoundwherestrongsupportand

theabilitytowithstandheavypressureare

required,suchastheintervertebraldiscs.

OtherTypesofConnectiveTissue

Bone Blood