Epithelial TissueEpithelial Tissue

Key TermsKey Terms

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 tissues found?Where are tissues found?

With few exceptions, organs are composed With few exceptions, organs are composed of four basic tissue types: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 organSkin, our largest organ

* made of all four tissue types

Epithelial TissueEpithelial Tissue

Makes up 3% of your body weightMakes up 3% of your body weight

They don’t moveThey 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 Of all tissues, they are the most widely varied in structure and functionvaried in structure and function

Locations of Epithelial TissuesLocations of Epithelial Tissues

Covers the body (epidermis)Covers the body (epidermis)

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

Found above a connective tissue layer Found above a connective tissue layer (epi = above)(epi = above)

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

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

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

Microvilli – small fingerlike extensions that Microvilli – 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 scales, or – like scales, or pancakes (“being pancakes (“being squashedsquashed like a like a pancakepancake”)”)

CuboidalCuboidal – looks like cubes – looks like cubes

ColumnarColumnar – longer and look – longer and look like columnslike columns

Cell OrganizationCell Organization

SimpleSimple – single layer of cells; typically found – single layer of cells; typically found where absorption and filtration occur or a single where absorption and filtration occur or a single layer of epithelial is neededlayer of epithelial is needed

simple squamoussimple squamoussimple cuboidalsimple cuboidal

simple columnarsimple columnarStratifiedStratified – layers of cells; common in areas – layers of cells; common in areas where protection is needed like the skinwhere protection is needed like the skin

stratified squamousstratified squamousstratified cuboidalstratified cuboidalstratified columnarstratified columnar

Two Types of Stratified ColumnarTwo Types of Stratified Columnar

CiliatedCiliated

UnciliatedUnciliated

cilia

No cilia

Squamous EpitheliumSquamous Epithelium

Simple – one cell thickSimple – one cell thick

Forms solid layer of cells Forms solid layer of cells which line blood vessels, which line blood vessels, body cavities and covers body cavities and covers organs in body cavitiesorgans in body cavities

Stratified – multiple layersStratified – multiple layersForms epidermisForms epidermis

Cuboidal EpitheliumCuboidal Epithelium

Simple – one cell thickSimple – one cell thick

Roughly cube shapedRoughly cube shaped

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

Duct

Cuboid Cells

Duct

Cuboid Cells

Columnar EpitheliumColumnar Epithelium

Simple – one cell thickSimple – one cell thick

Column shaped Column shaped (long and narrow)(long and narrow)

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

Confusing Epithelial TissueConfusing Epithelial TissueTransitional Epithelium – stratified tissue Transitional Epithelium – stratified tissue that can’t make up its mind as to whether it that can’t make up its mind as to whether it is squamous or cuboidalis squamous or cuboidal

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

Confusing Epithelial Tissue Continued…Confusing Epithelial Tissue Continued…

““Pseudostratified Columnar Epithelium”Pseudostratified Columnar Epithelium”

Looks like it has more than one layer Looks like it has more than one layer because of the position of the nucleusbecause of the position of the nucleus

Nuclei are positioned at differing levelsNuclei are positioned at differing levels

Cells narrow in the area without the Cells narrow in the area without the nucleusnucleus

Epithelial Tissue in Review…Epithelial Tissue in Review…

Types of Epithelial MembranesTypes of Epithelial Membranes

Mucous or mucosaMucous or mucosa– lining of tubes; – lining of tubes; moistens and protects from enzymes moistens and protects from enzymes (stomach, trachea, and vagina)(stomach, trachea, and vagina)Serous or serosaSerous or serosa – outside of organs; – outside of organs; lubricates (all thoracic, abdominal and pelvic lubricates (all thoracic, abdominal and pelvic organs)organs)Cutaneous or skinCutaneous or skin – body surface; protection – body surface; protection SynovialSynovial – synovial joints; lines and protects – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)synovial cavities (elbow, knee, hip, etc.)

Synovial MembranesSynovial Membranes

Some joints are Some joints are surrounded by a surrounded by a membrane membrane ((synoviumsynovium) that ) that produces a thick, produces a thick, synovial fluidsynovial fluid. This . This fluid nourish the fluid nourish the cartilage and keeps cartilage and keeps it slippery.it slippery.

Knee Joint

Mucosa MembranesMucosa MembranesMucus-secreting membrane that lines all body Mucus-secreting membrane that lines all body cavities or passages that come in contact with cavities or passages that come in contact with the outside of the body. Membranes are the outside of the body. Membranes are involved in absorption and secretion.involved in absorption and secretion.

Fungus

Serous MembranesSerous Membranes

SerousSerous membranes line membranes line body cavities that do not body cavities that do not open directly to the open directly to the outside, and they cover outside, and they cover the organs located in the organs located in those cavities. Fluid those cavities. Fluid lubricates the lubricates the membrane and reduces membrane and reduces friction and abrasion friction and abrasion when organs move when organs move against each other.against each other.

Canine Reproductive Organs

Cutaneous MembranesCutaneous Membranes

Cutaneous membranesCutaneous membranes of the skin cover the of the skin cover the surface of the body. surface of the body. They consist of stratified They consist of stratified squamous epithelium squamous epithelium and the underlying and the underlying connective tissues. connective tissues. Cutaneous membranes Cutaneous membranes are thick, relatively are thick, relatively waterproof, and dry. waterproof, and dry.

Skin Cancer