Epithelial tissue

1. Tissue Introduction Tissue Introduction
& &
Epithelial TissueEpithelial Tissue
PhysiologyPhysiology

2. Cells to TissuesCells to Tissues
As human body develops from single As human body develops from single
to multicellular, cells specialize.to multicellular, cells specialize.
Body is interdependent system, Body is interdependent system,
malfunction of one group of cells is malfunction of one group of cells is
catastrophic.catastrophic.
Cells specialize into types of tissues, Cells specialize into types of tissues,
then interspersed into organs. then interspersed into organs.

3. Tissues = groups of cells that are Tissues = groups of cells that are
similar in structure and function.similar in structure and function.
EpitheliumEpithelium
CoveringsCoverings
Linings of surfacesLinings of surfaces
ConnectiveConnective
SupportSupport
Bone, ligaments, Bone, ligaments,
fatfat
MuscleMuscle
MovementMovement
NervousNervous
ControlControl
Brain, nerves, Brain, nerves,
spinal cordspinal cord

4. Function of Epithelial TissueFunction of Epithelial Tissue
Protection Protection
Skin protects from sunlight & bacteria & physical Skin protects from sunlight & bacteria & physical
damage.damage.
AbsorptionAbsorption
Lining of small intestine, absorbing nutrients into Lining of small intestine, absorbing nutrients into
bloodblood
FiltrationFiltration
Lining of Kidney tubules filtering wastes from blood Lining of Kidney tubules filtering wastes from blood
plasmaplasma
SecretionSecretion
Different glands produce perspiration, oil, digestive Different glands produce perspiration, oil, digestive
enzymes and mucusenzymes and mucus

5. Characteristics of Epithelial TissueCharacteristics of Epithelial Tissue
Form continuous sheets (fit like tiles)Form continuous sheets (fit like tiles)
Apical SurfaceApical Surface
All epithelial cells have a top surface that All epithelial cells have a top surface that
borders an open space – known as a borders an open space – known as a lumenlumen
Basement Membrane Basement Membrane
Underside of Underside of allall epithelial cells which anchors epithelial cells which anchors
them to connective tissuethem 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

6. Classification of Classification of
Epithelial TissueEpithelial Tissue
Cell ShapeCell Shape
Squamous – flattened like Squamous – flattened like
fish scalesfish scales
Cuboidal - cubesCuboidal - cubes
Columnar - columnsColumnar - columns
Cell LayersCell Layers
Simple (one layer)Simple (one layer)
Stratified (many layers)Stratified (many layers)
Named for the type of cell at Named for the type of cell at
the apical surface.the apical surface.

7. Simple Squamous EpitheliumSimple Squamous Epithelium
StructureStructure
Single Layer of flattened cellsSingle Layer of flattened cells
FunctionFunction
Absorption, and filtrationAbsorption, and filtration
Not effective protection – single layer of cells.Not effective protection – single layer of cells.
LocationLocation
Walls of capillaries, air sacs in lungsWalls of capillaries, air sacs in lungs
Form serous membranes in body cavityForm serous membranes in body cavity

9. Simple Cuboidal EpitheliumSimple Cuboidal Epithelium
StructureStructure
Single layer of cube shaped cellsSingle layer of cube shaped cells
FunctionFunction
Secretion and transportation in glands, Secretion and transportation in glands,
filtration in kidneysfiltration in kidneys
LocationLocation
Glands and ducts (pancreas & salivary), Glands and ducts (pancreas & salivary),
kidney tubules, covers ovarieskidney tubules, covers ovaries

11. Simple Columnar EpitheliumSimple Columnar Epithelium
StructureStructure
Elongated layer of cells with nuclei at same levelElongated layer of cells with nuclei at same level
FunctionFunction
Absorption, Protection & SecretionAbsorption, Protection & Secretion
When open to body cavities – called mucous When open to body cavities – called mucous
membranesmembranes
Special FeaturesSpecial Features
MicrovillMicrovilli, bumpy extension of apical surface, increase i, bumpy extension of apical surface, increase
surface area and absorption rate.surface area and absorption rate.
Goblet cellsGoblet cells, single cell glands, produce protective , single cell glands, produce protective
mucus.mucus.
LocationLocation
Linings of entire digestive tractLinings of entire digestive tract

13. Pseudostratified EpitheliumPseudostratified Epithelium
StructureStructure
Irregularly shaped cells with nuclei at different Irregularly shaped cells with nuclei at different
levels – appear stratified, but aren’t.levels – appear stratified, 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 mucus Cilia (larger than microvilli) sweep mucus
LocationLocation
Respiratory Linings & Reproductive tractRespiratory Linings & Reproductive tract

14. Cilia
Basement
Membrane

15. Stratified Squamous EpitheliumStratified Squamous Epithelium
StructureStructure
Many layers (usually cubodial/columnar at Many layers (usually cubodial/columnar at
bottom and squamous at top)bottom and squamous at top)
FunctionFunction
ProtectionProtection
Keratin (protein) is accumulated in older cells Keratin (protein) is accumulated in older cells
near the surface – waterproofs and toughens near the surface – waterproofs and toughens
skin.skin.
LocationLocation
Skin (keratinized), mouth & throatSkin (keratinized), mouth & throat

16. Keratin
Stratified
Cubodial (layers
of cubodial only)

17. Transitional Epithelium Transitional Epithelium
StructureStructure
Many layersMany layers
Very specialized – cells at base are cuboidal or Very specialized – cells at base are cuboidal or
columnar, at surface will vary.columnar, at surface will vary.
Change between stratified & simple as tissue Change between stratified & simple as tissue
is stretched out.is stretched out.
FunctionFunction
Allows stretching (change size)Allows stretching (change size)
LocationLocation
Urinary bladder, ureters & urethraUrinary bladder, ureters & urethra

19. GlandsGlands
One or more cells that make and secrete a One or more cells that make and secrete a
product.product.
Secretion = protein in aqueous solution: Secretion = protein in aqueous solution:
hormones, acids, oils.hormones, acids, oils.
Endocrine glandsEndocrine glands
No duct, release secretion into blood vessels No duct, release secretion into blood 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 glands.Sweat, Oil glands, Salivary glands, Mammary glands.

20. Shapes of Exocrine glandsShapes of Exocrine glands
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

22. Modes of SecretionModes of Secretion
(How the gland’s product is released)(How the gland’s product is released)
MerocrineMerocrine
Just released by exocytosis without altering Just released by exocytosis without altering
the gland at all.the gland at all.
Ex: Sweat glands and salivary glandsEx: Sweat glands and salivary glands
HolocrineHolocrine
The gland ruptures and releases secretion and The gland ruptures and releases secretion and
dead cells as well.dead cells as well.
Sebaceous (oil glands on the face) only Sebaceous (oil glands on the face) only
exampleexample