Epithelial Epithelial TissueTissue

Histology:Histology:

– the study of tissues.the study of tissues.

Tissues:Tissues:

– Simply groups of similar cells that work Simply groups of similar cells that work together performing the same tasktogether performing the same task

– Greatest form of teamwork in the bodyGreatest form of teamwork in the body

Where are epithelial tissues found?Where are epithelial tissues found?

With few exceptions, organs are With few exceptions, organs are composed of four basic tissue types:composed of four basic tissue types:

– – Epithelial TissueEpithelial Tissue

– – Connective TissueConnective Tissue

– – Muscular TissueMuscular Tissue

– – Nervous TissueNervous Tissue

Why Study Histology?Why Study Histology?

Knowing the difference between normal and abnormal tissue is the first step in diagnosis and

treatment of patients.

Skin, our largest and heaviest organSkin, our largest and heaviest organ

made of all four tissue types

Epithelial Tissue

Muscular Tissue

Nervous Tissue

Connective Tissue

Epithelial TissueEpithelial TissueMakes up 3% of your body weightMakes up 3% of your body weight

Cells don’t moveCells don’t move

They don’t send messagesThey don’t send messages

Their cells are all touching one anotherTheir cells are all touching one another

Of all tissues, they are the most widely varied in Of all tissues, they are the most widely varied in structure and functionstructure and function

Locations of Epithelial TissuesLocations of Epithelial TissuesCovers the body Covers the body

Found on the inside of Found on the inside of hollow organs and the hollow organs and the outside of outside of all all organsorgans

Found above a Found above a connective tissue layer connective tissue layer

Lines the cavities, Lines the cavities, tubes, ducts, and blood tubes, ducts, and blood vessels inside the bodyvessels inside the body

Epithelial AnatomyEpithelial AnatomyApical surfaceApical surface – upper surface that is free or – upper surface that is free or exposed to the “exterior”exposed to the “exterior”

Basal surfaceBasal surface – attached surface (below) – attached surface (below)

MicrovilliMicrovilli – small fingerlike extensions that – small fingerlike extensions that increase the surface area allowing for more work increase the surface area allowing for more work to be doneto be done

Functions of Epithelial TissueFunctions of Epithelial Tissue– Protects from physical & chemical injuryProtects from physical & chemical injury– Protects against microbial infectionProtects against microbial infection– Contains nerve endings which respond to Contains nerve endings which respond to

stimulistimuli– Filters, secretes & reabsorbs materialsFilters, secretes & reabsorbs materials– Secretes fluids to lubricate jointsSecretes fluids to lubricate joints

Three Basic ShapesThree Basic ShapesSquamousSquamous – like – like scales, or pancakes scales, or pancakes (“being (“being squashedsquashed like like a a pancakepancake”)”)

CuboidalCuboidal – looks like – looks like cubescubes

ColumnarColumnar – longer – longer and look like columnsand look like columns

Cell OrganizationCell OrganizationSimpleSimple – single layer of cells; typically found where – single layer of cells; typically found where absorption and filtration occur absorption and filtration occur

simple squamoussimple squamous

simple cuboidalsimple cuboidal

simple columnarsimple columnar

StratifiedStratified – layers of cells; common in areas where – layers of cells; common in areas where protection is needed like the skinprotection is needed like the skin

stratified squamousstratified squamous

Two Types of Stratified ColumnarTwo Types of Stratified Columnar

CiliatedCiliated

UnciliatedUnciliated

cilia

No cilia

Squamous EpitheliumSquamous EpitheliumSimple SquamousSimple Squamous

Forms solid, single layer of Forms solid, single layer of cells cells

lines blood vessels, body lines blood vessels, body cavities and covers organscavities and covers organs

Stratified SquamousStratified Squamous Forms epidermis and is Forms epidermis and is

mostly for protection mostly for protection

Found in areas of high Found in areas of high friction friction

Cuboidal EpitheliumCuboidal Epithelium

Simple CuboidalSimple Cuboidal

Roughly cube shapedRoughly cube shaped

Line ducts in kidneys where Line ducts in kidneys where absorption and secretion absorption and secretion activities take place.activities take place.

Very, very rare to have Very, very rare to have stratified cuboidalstratified cuboidal

Columnar EpitheliumColumnar EpitheliumSimple columnar– one cell Simple columnar– one cell thickthick

rectangular shaped rectangular shaped (long and narrow)(long and narrow)

Lines digestive tract where Lines digestive tract where absorption & secretion absorption & secretion occurs.occurs.

White spots are White spots are goblet cells goblet cells which secrete mucous which secrete mucous

No stratified columnarNo stratified columnar

Confusing Epithelial TissueConfusing Epithelial Tissue

Transitional Epithelium – Numerous layers of Transitional Epithelium – Numerous layers of cells of varying and often irregular shape cells of varying and often irregular shape

Shape of cells depends upon the amount of Shape of cells depends upon the amount of stretching (ex: bladder)stretching (ex: bladder)

Confusing Epithelial Tissue Continued…Confusing Epithelial Tissue Continued…““Pseudostratified Columnar Epithelium”Pseudostratified Columnar Epithelium”

Tall rectangular cells, with Tall rectangular cells, with multiple irregular rows multiple irregular rows of nucleiof nuclei. Nuclei are positioned at differing levels. Nuclei are positioned at differing levels

Cells narrow in the area without the nucleusCells narrow in the area without the nucleus

Located in the trachea; secrete & move mucousLocated in the trachea; secrete & move mucous

Goblet cells secret mucous to aid cilia

in moving substances across the cells’ surface

Epithelial Tissue in Review…Epithelial Tissue in Review…

Epithelial tissues can be found in three types of membranes: Cutaneous, Serous, and mucous membranes.

Mucosa Mucosa MembranesMembranes

Mucus-secreting membranes line tubes; moistens and Mucus-secreting membranes line tubes; moistens and protects from enzymes and acid (i.e., stomach, trachea, protects from enzymes and acid (i.e., stomach, trachea, mouth, and vagina)mouth, and vagina)

Membranes are involved in absorption and secretion.Membranes are involved in absorption and secretion.

Serous MembranesSerous Membranes

SerousSerous membranes line membranes line body cavities that do not body cavities that do not open directly to the outsideopen directly to the outside

They cover the organs They cover the organs located in those cavities. located in those cavities.

Fluid lubricates the Fluid lubricates the membrane and reduces membrane and reduces friction and abrasion when friction and abrasion when organs move against each organs move against each other.other.

Cutaneous MembranesCutaneous Membranes

Cutaneous Cutaneous membranesmembranes cover the cover the surface of the body. surface of the body.

Consists of stratified Consists of stratified squamous epithelium squamous epithelium

Cutaneous Cutaneous membranes are thick, membranes are thick, relatively waterproof, relatively waterproof, and dry. and dry.

Function = protectionFunction = protection