tissues and tissue types

8/14/2019 Tissues and Tissue Types

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Tissues are:• Collections of specialized cells and cellproducts organized to perform a limitednumber of functions Histology = study of tissues

The four tissue types are:

• Epithelial

• Connective• Muscular

• Nervous

Tissues and tissue typesTissues and tissue types



Epithelial tissue Layer of cells covering exposed body surfaces inside or

outside

• Skin

• Linings of body cavities

• Linings of any body opening• Linings of internal passageways

Form barriers Form glands

• Secretory structures from epithelium



Characteristics of epitheliumCharacteristics of epithelium

CellularityCellulari

ty: composed of tightly bound, arranged cells: composed of tightly bound, arranged cells

Polarity:Polar

ity:

uneven distribution of materials in cells;uneven distribution of materials in cells;

one side always faces an opening;one side always faces an opening;

one side always attached to a basement membrane toone side always attached to a basement membrane toadjacent tissueadjacent tissue

Attachment:Attachment:

one side always attached to membrane made byone side always attached to membrane made byepithelium (basal membrane) & connective tissueepithelium (basal membrane) & connective tissueunderneathunderneath

Avascularity:Avascular

ity:

No blood vessels in epitheliumNo blood vessels in epithelium

Nourished by diffusion or absorptionNourished by diffusion or absorption

RegenerationR

egeneration

Surface cells replaced continually by mitotic cells belowSurface cells replaced continually by mitotic cells below



Epithelial functionEpithelial function

1. Provide physical protection1. Provide physical protection

Protect from abrasion, dehydration,…Protect from abrasion, dehydration,…

2. From a barrier for permeability2. From a barrier for permeability

Can give selective absorption or secretionCan give selective absorption or secretion

Can be regulated & modified by stimuli, I.e.,Can be regulated & modified by stimuli, I.e.,changed with needchanged with need

3. Provide sensations:3. Provide sensations:

Epithelial cells deeply innervated w. sensory nervesEpithelial cells deeply innervated w. sensory nerves

Detect changes in environment & relay to bodyDetect changes in environment & relay to body

4. Produce specialized secretions4. Produce specialized secretions

Glandular epithelium may be scattered in otherGlandular epithelium may be scattered in otherepitheliumepithelium



Classification of EpitheliumClassification of Epithelium

Classified by arrangement of cells into layersClassified by arrangement of cells into layers• simple = one cell layer thicksimple = one cell layer thick

• stratified = many cell layers thickstratified = many cell layers thick

• pseudostratified = single layer of cells where all cellpseudostratified = single layer of cells where all celldon’t reach apical surfacedon’t reach apical surface nuclei at found at different levels so it looks multilayerednuclei at found at different levels so it looks multilayered

Classified by shape of surface cellsClassified by shape of surface cells• squamous =flatsquamous =flat

• cuboidal = cube-shapedcuboidal = cube-shaped

• columnar = tall columncolumnar = tall column

• transitional = shape varies with tissue stretchingtransitional = shape varies with tissue stretching



SquamousSquamousSimple squamousSimple squamous

In protected regions for absorptionIn protected regions for absorption• Respiratory alveoli for gas exchangeRespiratory alveoli for gas exchange

In regions to reduce frictionIn regions to reduce friction• Linings of blood vessels & heart = endotheliumLinings of blood vessels & heart = endothelium• Serous membranes lining body cavitiesSerous membranes lining body cavities• MesotheliumMesothelium = any simple squamous epithelium lining= any simple squamous epithelium lining

ventral body cavitiesventral body cavities



Single row of cube-shaped cells, often with microvilli.

• Absorption & secretion; produces mucus.

Mammary and salivary glands.



Single row of tall, narrow cells

• vertically oriented, oval nuclei in basal half of cell Absorption & secretion; secretion of mucus Inner lining of GI tract



Keratinized Stratified SquamousKeratinized Stratified Squamous

Multilayered epithelium covered with layer of compact, dead squamous cells packed with proteinkeratin

Retards water loss & prevents penetration of organisms

N k i i d S ifi d



Nonkeratinized StratifiedNonkeratinized Stratified

SquamousSquamous

Multilayered epithelium that lacks surfacelayer of dead cells forming abrasion-resistant,moist, slippery layer

Found on ton ue & va ina

Epithelial

layer



Stratified Cuboidal EpitheliumStratified Cuboidal Epithelium

Two or more layers of cells; surface cells square

Secretes sweat; ovarian hormones & produces sperm

Found ovarian follicles & seminiferous tubules



Cuboidal EpitheliaCuboidal Epithelia



Transitional EpitheliumTransitional Epithelium



Transitional EpitheliumTransitional Epithelium

Multilayered epithelium with rounded

surface cells that flatten when the tissueis stretched

Stretches to allow filling of urinary tract

Found in urinary tract -- urinary bladder



Specialized for contractionSpecialized for contraction

Three typesThree types

• SkeletalSkeletal• CardiacCardiac

• SmoothSmooth

Muscle tissueMuscle tissue



Muscle TissueMuscle Tissue



Establishing a structural frameworkEstablishing a structural framework

Transporting fluids and dissolvedTransporting fluids and dissolvedmaterialsmaterials

Protecting delicate organsProtecting delicate organs

Supporting, surrounding andSupporting, surrounding and

interconnecting tissuesinterconnecting tissues

Storing energy reservesStoring energy reserves

Defending the body from microorganismsDefending the body from microorganisms

Connective tissue functionsConnective tissue functions



A Classification of ConnectiveA Classification of Connective

TissuesTissues



Specialized cellsSpecialized cells

MatrixMatrix• Composed of extracellular protein fibersComposed of extracellular protein fibers

and a ground substanceand a ground substance

Connective tissues containConnective tissues contain



Contains varied cell populationsContains varied cell populations

Contains various fiber typesContains various fiber types A syrupy ground substanceA syrupy ground substance

Connective tissue proper Connective tissue proper



Fluid connective tissueFluid connective tissue

Contains a distinctive cell populationContains a distinctive cell population

Watery ground substance withWatery ground substance with

dissolved proteinsdissolved proteins

Two typesTwo types

• BloodBlood

• LymphLymph



Less diverse cell populationLess diverse cell population

Dense ground substanceDense ground substance

Closely packed fibersClosely packed fibers

Two typesTwo types

• CartilageCartilage

• BoneBone

Supporting connective tissuesSupporting connective tissues



Contains fibers, a viscous groundContains fibers, a viscous ground

substance, and a varied cell populationsubstance, and a varied cell population• FibroblastsFibroblasts

• MacrophageMacrophage

• AdipocytesAdipocytes• Mesenchymal cellsMesenchymal cells

• MelanocytesMelanocytes

• Mast cellsMast cells• LymphocytesLymphocytes

• MicrophagesMicrophages




Classified as loose or denseClassified as loose or dense LooseLoose

• Embryonic mesenchyme, mucous connectiveEmbryonic mesenchyme, mucous connective

tissuestissues

• Areolar tissueAreolar tissue

• Adipose tissueAdipose tissue

• Reticular tissueReticular tissue

DenseDense• Dense regular CTDense regular CT

• Dense irregular CTDense irregular CT




The Cells and Fibers of The Cells and Fibers of

Connective Tissue Proper Connective Tissue Proper



Connective Tissue in EmbryosConnective Tissue in Embryos



Adipose and Reticular TissuesAdipose and Reticular Tissues



Dense Connective TissuesDense Connective Tissues



Distinctive collections of cells in a fluidDistinctive collections of cells in a fluid

matrixmatrix

BloodBlood

• Formed elements and plasmaFormed elements and plasma Red blood cells, white blood cells and plateletsRed blood cells, white blood cells and platelets

• Arteries carry blood away, veins carry toArteries carry blood away, veins carry to

the heartthe heart• Capillaries allow diffusion into theCapillaries allow diffusion into the

interstitial fluidinterstitial fluid

LymphLymph

Fluid connective tissuesFluid connective tissues



Formed Elements of the BloodFormed Elements of the Blood



Cartilage and bone support the rest of the bodyCartilage and bone support the rest of the body

CartilageCartilage

• Grows via interstitial and appositional growthGrows via interstitial and appositional growth

• Matrix is a firm gel containing chondroitin sulfateMatrix is a firm gel containing chondroitin sulfate

• Cells called chondrocytesCells called chondrocytes

• Cells found in lacunaeCells found in lacunae

• Perichondrium separates cartilage fromPerichondrium separates cartilage fromsurrounding tissuessurrounding tissues

• Three types: hyaline, elastic and fibrocartilageThree types: hyaline, elastic and fibrocartilage

Supporting connective tissuesSupporting connective tissues

The Perichondrium and Types ofThe Perichondrium and Types of



The Perichondrium and Types of The Perichondrium and Types of

CartilageCartilage




CartilageCartilage



Has osteocytesHas osteocytes

• Depend on diffusion throughDepend on diffusion throughcanaliculi for nutrientscanaliculi for nutrients

Little ground substanceLittle ground substance

Dense mineralized matrixDense mineralized matrix Surrounded by periosteumSurrounded by periosteum

Bone, or osseus tissueBone, or osseus tissue



BoneBone

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