Tissue Introduction Tissue Introduction & &

Epithelial TissueEpithelial Tissue

PhysiologyPhysiology

Cells to TissuesCells to Tissues

As human body develops from As human body develops from single to multicellular, cells single to multicellular, cells specialize.specialize.

Body is interdependent system, Body is interdependent system, malfunction of one group of malfunction of one group of cells is catastrophic.cells is catastrophic.

Cells specialize into types of Cells specialize into types of tissues, then interspersed tissues, then interspersed into organs. into organs.

Tissues = groups of cells Tissues = groups of cells that are similar in structure that are similar in structure

and function.and function. EpitheliumEpithelium

CoveringsCoverings Linings of Linings of surfacessurfaces

ConnectiveConnective SupportSupport Bone, Bone, ligaments, fatligaments, fat

MuscleMuscle MovementMovement

NervousNervous ControlControl Brain, nerves, Brain, nerves, spinal cordspinal cord

Function of Epithelial Function of Epithelial TissueTissue

Protection Protection Skin protects from sunlight & bacteria Skin protects from sunlight & bacteria & physical damage.& physical damage.

AbsorptionAbsorption Lining of small intestine, absorbing Lining of small intestine, absorbing nutrients into bloodnutrients into blood

FiltrationFiltration Lining of Kidney tubules filtering Lining of Kidney tubules filtering wastes from blood plasmawastes from blood plasma

SecretionSecretion Different glands produce perspiration, Different glands produce perspiration, oil, digestive enzymes and mucusoil, digestive enzymes and mucus

Characteristics of Characteristics of Epithelial TissueEpithelial Tissue

Form continuous sheets (fit like Form continuous sheets (fit like tiles)tiles)

Apical SurfaceApical Surface All epithelial cells have a top surface All epithelial cells have a top surface that borders an open space – known as a that borders an open space – known as a lumenlumen

Basement Membrane Basement Membrane Underside of Underside of allall epithelial cells which epithelial cells which anchors them to connective tissueanchors them to connective tissue

Avascularity (a = without)Avascularity (a = without) Lacks blood vesselsLacks blood vessels Nourished by connective tissueNourished by connective tissue

Regenerate & repair quicklyRegenerate & repair quickly

Classification Classification of Epithelial of Epithelial

TissueTissue Cell ShapeCell Shape

Squamous – flattened Squamous – flattened like fish scaleslike fish scales

Cuboidal - cubesCuboidal - cubes Columnar - columnsColumnar - columns

Cell LayersCell Layers Simple (one layer)Simple (one layer) Stratified (many Stratified (many layers)layers)

Named for the type of Named for the type of cell at the apical cell at the apical surface.surface.

Simple Squamous Simple Squamous EpitheliumEpithelium

StructureStructure Single Layer of flattened cellsSingle Layer of flattened cells

FunctionFunction Absorption, and filtrationAbsorption, and filtration Not effective protection – single Not effective protection – single layer of cells.layer of cells.

LocationLocation Walls of capillaries, air sacs in Walls of capillaries, air sacs in lungslungs

Form serous membranes in body cavityForm serous membranes in body cavity

Simple Cuboidal Simple Cuboidal EpitheliumEpithelium

StructureStructure Single layer of cube shaped cellsSingle layer of cube shaped cells

FunctionFunction Secretion and transportation in Secretion and transportation in glands, filtration in kidneysglands, filtration in kidneys

LocationLocation Glands and ducts (pancreas & Glands and ducts (pancreas & salivary), kidney tubules, covers salivary), kidney tubules, covers ovariesovaries

Simple Columnar Simple Columnar EpitheliumEpithelium

StructureStructure Elongated layer of cells with nuclei at Elongated layer of cells with nuclei at same levelsame level

FunctionFunction Absorption, Protection & SecretionAbsorption, Protection & Secretion When open to body cavities – called When open to body cavities – called mucous membranesmucous membranes

Special FeaturesSpecial Features MicrovillMicrovilli, bumpy extension of apical i, bumpy extension of apical surface, increase surface area and surface, increase surface area and absorption rate.absorption rate.

Goblet cellsGoblet cells, single cell glands, , single cell glands, produce protective mucus.produce protective mucus.

LocationLocation Linings of entire digestive tractLinings of entire digestive tract

Pseudostratified Pseudostratified EpitheliumEpithelium

StructureStructure Irregularly shaped cells with nuclei at Irregularly shaped cells with nuclei at different levels – appear stratified, different levels – appear stratified, but aren’t.but aren’t.

All cells reach basement membraneAll cells reach basement membrane FunctionFunction

Absorption and SecretionAbsorption and Secretion Goblet cells produce mucusGoblet cells produce mucus Cilia (larger than microvilli) sweep Cilia (larger than microvilli) sweep mucus mucus

LocationLocation Respiratory Linings & Reproductive Respiratory Linings & Reproductive tracttract

Cilia

Basement Membrane

Stratified Squamous Stratified Squamous EpitheliumEpithelium

StructureStructure Many layers (usually Many layers (usually cubodial/columnar at bottom and cubodial/columnar at bottom and squamous at top)squamous at top)

FunctionFunction ProtectionProtection Keratin (protein) is accumulated in Keratin (protein) is accumulated in older cells near the surface – older cells near the surface – waterproofs and toughens skin.waterproofs and toughens skin.

LocationLocation Skin (keratinized), mouth & throatSkin (keratinized), mouth & throat

Keratin

Stratified Cubodial (layers of cubodial only)

Transitional Epithelium Transitional Epithelium StructureStructure

Many layersMany layers Very specialized – cells at base Very specialized – cells at base are cuboidal or columnar, at are cuboidal or columnar, at surface will vary.surface will vary.

Change between stratified & simple Change between stratified & simple as tissue is stretched out.as tissue is stretched out.

FunctionFunction Allows stretching (change size)Allows stretching (change size)

LocationLocation Urinary bladder, ureters & urethraUrinary bladder, ureters & urethra

GlandsGlands

One or more cells that make and secrete One or more cells that make and secrete a product.a product.

Secretion = protein in aqueous Secretion = protein in aqueous solution: hormones, acids, oils.solution: hormones, acids, oils.

Endocrine glandsEndocrine glands No duct, release secretion into blood No duct, release secretion into blood vessels vessels

Often hormonesOften hormones Thyroid, adrenal and pituitary glandsThyroid, adrenal and pituitary glands

Exocrine glandsExocrine glands Contain ducts, empty onto epithelial surfaceContain ducts, empty onto epithelial surface Sweat, Oil glands, Salivary glands, Mammary Sweat, Oil glands, Salivary glands, Mammary glands.glands.

Shapes of Exocrine Shapes of Exocrine glandsglands

Branching

Simple – single, unbranched duct

Compound – branched.

Shape: tubular or alveolar

Tubular – shaped like a tube

Alveolar – shaped like flasks or sacs

Tubuloalveolar – has both tubes and sacs in gland

Modes of SecretionModes of Secretion

(How the gland’s product is (How the gland’s product is released)released)

MerocrineMerocrine Just released by exocytosis without Just released by exocytosis without altering the gland at all.altering the gland at all.

Ex: Sweat glands and salivary glandsEx: Sweat glands and salivary glands HolocrineHolocrine

The gland ruptures and releases The gland ruptures and releases secretion and dead cells as well.secretion and dead cells as well.

Sebaceous (oil glands on the face) Sebaceous (oil glands on the face) only exampleonly example