Tissues

Tissues

Body TissuesTissuesGroups of cells with similar structure and functionFour primary typesEpithelial tissue (epithelium)Connective tissueMuscle tissueNervous tissue

Epithelial TissuesLocationsBody coveringsBody liningsGlandular tissueFunctionsProtectionAbsorptionFiltrationSecretionEpithelium CharacteristicsCells fit closely together and often form sheetsThe apical surface is the free surface of the tissueThe lower surface of the epithelium rests on a basement membraneAvascular (no blood supply)Regenerate easily if well nourishedEpithelium CharacteristicsFigure 3.17a

Classification of EpitheliaNumber of cell layersSimpleone layerStratifiedmore than one layerFigure 3.17a

Classification of EpitheliaShape of cellsSquamousflattenedCuboidalcube-shapedColumnarcolumn-likeFigure 3.17b

Simple EpitheliaSimple squamousSingle layer of flat cellsUsually forms membranesLines body cavitiesLines lungs and capillariesSimple EpitheliaFigure 3.18a

Simple EpitheliaSimple cuboidalSingle layer of cube-like cellsCommon in glands and their ductsForms walls of kidney tubulesCovers the ovariesSimple EpitheliaFigure 3.18b

Simple EpitheliaSimple columnarSingle layer of tall cellsOften includes mucus-producing goblet cellsLines digestive tractSimple EpitheliaFigure 3.18c

Simple EpitheliaPseudostratified columnarSingle layer, but some cells are shorter than othersOften looks like a double layer of cellsSometimes ciliated, such as in the respiratory tractMay function in absorption or secretionSimple EpitheliaFigure 3.18d

Stratified EpitheliaStratified squamousCells at the apical surface are flattenedFound as a protective covering where friction is commonLocationsSkinMouthEsophagusStratified EpitheliaFigure 3.18e

Stratified EpitheliaStratified cuboidaltwo layers of cuboidal cellsStratified columnarsurface cells are columnar, cells underneath vary in size and shapeStratified cuboidal and columnarRare in human bodyFound mainly in ducts of large glandsStratified EpitheliaTransitional epitheliumShape of cells depends upon the amount of stretchingLines organs of the urinary systemStratified EpitheliaFigure 3.18f

Glandular EpitheliumGlandOne or more cells responsible for secreting a particular productGlandular EpitheliumTwo major gland typesEndocrine glandDuctless since secretions diffuse into blood vesselsAll secretions are hormonesExocrine glandSecretions empty through ducts to the epithelial surfaceInclude sweat and oil glandsConnective TissueFound everywhere in the bodyIncludes the most abundant and widely distributed tissuesFunctionsBinds body tissues togetherSupports the bodyProvides protectionConnective Tissue CharacteristicsVariations in blood supplySome tissue types are well vascularizedSome have a poor blood supply or are avascularExtracellular matrixNon-living material that surrounds living cellsExtracellular MatrixTwo main elementsGround substancemostly water along with adhesion proteins and polysaccharide moleculesFibersProduced by the cellsThree typesCollagen (white) fibersElastic (yellow) fibersReticular fibersConnective Tissue TypesBone (osseous tissue)Composed ofBone cells in lacunae (cavities)Hard matrix of calcium saltsLarge numbers of collagen fibersUsed to protect and support the bodyConnective Tissue TypesFigure 3.19a

Connective Tissue TypesHyaline cartilageMost common type of cartilageComposed ofAbundant collagen fibersRubbery matrixLocationsLarynxEntire fetal skeleton prior to birthConnective Tissue TypesFigure 3.19b

Connective Tissue TypesElastic cartilageProvides elasticityLocationSupports the external earFibrocartilageHighly compressibleLocationForms cushion-like discs between vertebrae

Connective Tissue TypesFigure 3.19c

Connective Tissue TypesDense connective tissue (dense fibrous tissue)Main matrix element is collagen fiberFibroblasts are cells that make fibersLocationsTendonsattach skeletal muscle to boneLigamentsattach bone to bone at jointsDermislower layers of the skinConnective Tissue TypesFigure 3.19d

Connective Tissue TypesLoose connective tissue typesAreolar tissueMost widely distributed connective tissueSoft, pliable tissue like cobwebsFunctions as a packing tissueContains all fiber typesCan soak up excess fluid (causes edema)Connective Tissue TypesFigure 3.19e

Connective Tissue TypesLoose connective tissue typesAdipose tissueMatrix is an areolar tissue in which fat globules predominateMany cells contain large lipid depositsFunctionsInsulates the bodyProtects some organsServes as a site of fuel storageConnective Tissue TypesFigure 3.19f

Connective Tissue TypesLoose connective tissue typesReticular connective tissueDelicate network of interwoven fibersForms stroma (internal supporting network) of lymphoid organsLymph nodesSpleenBone marrowConnective Tissue TypesFigure 3.19g

Connective Tissue TypesBlood (vascular tissue)Blood cells surrounded by fluid matrix called blood plasmaFibers are visible during clottingFunctions as the transport vehicle for materialsConnective Tissue TypesFigure 3.19h

Muscle TissueFunction is to produce movementThree typesSkeletal muscleCardiac muscleSmooth muscleMuscle Tissue TypesSkeletal muscleUnder voluntary controlContracts to pull on bones or skinProduces gross body movements or facial expressionsCharacteristics of skeletal muscle cellsStriatedMultinucleate (more than one nucleus)Long, cylindricalMuscle Tissue TypesFigure 3.20a

Muscle Tissue TypesCardiac muscleUnder involuntary controlFound only in the heartFunction is to pump bloodCharacteristics of cardiac muscle cellsCells are attached to other cardiac muscle cells at intercalated disksStriatedOne nucleus per cellMuscle Tissue TypesFigure 3.20b

Muscle Tissue TypesSmooth muscleUnder involuntary muscleFound in walls of hollow organs such as stomach, uterus, and blood vesselsCharacteristics of smooth muscle cellsNo visible striationsOne nucleus per cellSpindle-shaped cellsMuscle Tissue TypesFigure 3.20c

Nervous TissueComposed of neurons and nerve support cellsFunction is to send impulses to other areas of the bodyIrritabilityConductivityNervous TissueFigure 3.21

Tissue Repair (Wound Healing)RegenerationReplacement of destroyed tissue by the same kind of cellsFibrosisRepair by dense (fibrous) connective tissue (scar tissue)Determination of methodType of tissue damagedSeverity of the injuryEvents in Tissue RepairCapillaries become very permeableIntroduce clotting proteinsA clot walls off the injured areaFormation of granulation tissueGrowth of new capillariesRebuild collagen fibersRegeneration of surface epitheliumScab detachesRegeneration of TissuesTissues that regenerate easilyEpithelial tissue (skin and mucous membranes)Fibrous connective tissues and boneTissues that regenerate poorlySkeletal muscleTissues that are replaced largely with scar tissueCardiac muscleNervous tissue within the brain and spinal cord