Identify the type of junction with its purpose: forms an impermeable junction; prevents molecules...

Identify the type of junction with its purpose:

forms an impermeable junction; prevents molecules from passing between cells

Let small molecules move directly between neighboring cells

reduces tearing, twisting, stretching

helps form the tight junction around apical lateral borders

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Location:Covers body SurfacesLines body cavitiesForms glands

Functions:SecretionSelective absorptionProtectionTranscellular supportDetection of sensation

Epithelial Function

SecretionWhen a cell produces substances and releases

those substances into the environment.Ie. Digestive tract has high secretion

Selective AbsorptionEpithelial tissue is in direct contact with the

outer environment so it selects what materials come into and out of the cell

ProtectionTissue in contact with the external

environment has to have a protective function to protect internal tissue Ie. Skin

Function

Transcellular TransportAble to help substances travel through a

certain distance

Detection of SensationAssociated with nerve cells because epithelium

can be found on the external part of the body; nerve cells receive stimuli

Function

Cells are usually joined by specialized cell-to-cell junctions

Little or no intercellular materialDon’t have a lot of extracellular material

around them

Epithelial Festures

First the name of tissue indicates # of layers (3 types)1. Simple – one layer of cells (extends from

basement membrane to the apical surface)

2. Stratified – more than one layer of cells

Classifications of Epithelia

Classification of Epithelia3. Pseudostratified- tissue appears to be

stratified, but all cells contact basement membrane so it is in fact simple

Classifications of EpitheliaLast name of tissue describes shape of cells

(3 types)1. Squamous – cells wider than

tall (plate or “scale” like)

2. Cuboidal – cells are as wide as tall, as in cubes

3. Columnar – cells are taller than they are wide, like columns

Naming EpitheliaNaming the epithelia includes the layers

(first) and the shape of the cells (second)i.e. stratified cuboidal epithelium

The name may also include any accessory structuresGoblet cells, cilia, keratin, etc.

Special epithelial tissues (don’t follow naming convention)PsuedostratifiedTransitional

How do you go about naming epithelial tissue?

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Simple Squamous EpitheliumDescription

single layer of flat cells with disc-shaped nuclei

Special types Endothelium (inner covering)

slick lining of hollow organsMesothelium (middle covering)

Lines peritoneal (abdomen), pleural (lungs), and pericardial (heart) cavities

Covers visceral (internal) organs of those cavities (ie. pancreas, stomach, lung, etc.)

Simple Squamous EpitheliumFunction:

Passage of materials by passive diffusion and filtration

Secretes lubricating substances reducing friction from muscle in serous membranes

Location:Renal corpuscles (blood filtering component in kidneys)

Alveoli of lungs

Lining of heart, blood and lymphatic vessels

Lining of ventral body cavity Pericardium- membrane covering the heart

Pleura- membrane covering the lung

Peritoneum- membrane covering the abdominopelvic cavity

Simple Squamous Epithelium

Simple squamous lining the

walls of the capillary

Simple Cuboidal EpitheliumDescription

single layer of cube-like cells with large, spherical central nuclei

Function secretion and absorption

Location kidney tubules, secretory portions of

small glands, ovary surface

Simple Cuboidal Epithelium

Simple Columnar EpitheliumDescription

single layer of column-shaped (rectangular) cells with oval nucleiSome have cilia at their apical surfaceMay contain goblet cells (secrete

mucus)Function

Absorption; secretion of mucus, enzymes, and other substances

Ciliated type propels mucus or reproductive cells by ciliary action

Simple Columnar EpitheliumLocation

Non-ciliated form Lines digestive

tract, gallbladder, ducts of some glands

Ciliated form Lines small

bronchi, uterine tubes, and uterus

Identify a location where simple squamous, cuboidal

or columnar tissue is found?

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Stratified EpitheliaLayers: contain two or more layers of cellsRegeneration: from Basal membraneFunction: protectionNaming: according to the shape of cells at

apical layer

Stratified Squamous EpitheliumDescription

Many layers of cells – squamous in shape

Deeper layers of cells appear cuboidal or columnar

Thickest epithelial tissue – adapted for protection

Stratified Squamous Epithelium

Specific types Keratinized – contain the protective protein

keratinSurface cells are dead and full of keratin

Non-keratinized – forms moist lining of body openings

FunctionProtects underlying tissues in areas subject to

abrasionLocation

Keratinized – forms epidermisNon-keratinized – forms lining of esophagus,

mouth, and vagina

Stratified Squamous Epithelium

Non-keratinized vs. Keratinized

Stratified Cuboidal EpitheliumDescription

generally two layers of cube-shaped cells

Functionprotection

LocationForms largest

ducts of sweat glands

Forms ducts of mammary glands and salivary glands

Stratified Columnar Epithelium

Descriptionseveral layers;

basal cells usually cuboidal; superficial cells elongated

Functionprotection and

secretionLocation

Rare tissue typeFound in male

urethra and vas deferens, largest ducts of salivary glands, nasopharynx

Pseudostratified Columnar EpitheliumDescription

All cells originate at basement membraneOnly tall cells reach the apical surfaceMay contain goblet cells and bear ciliaNuclei lie at varying heights within cells

Gives false impression of stratification

Function secretion of mucus; propulsion of mucus by

cilia

Pseudostratified Columnar EpitheliumLocations

Non-ciliated type Ducts of male

reproductive tubes

Ducts of large glands

Ciliated variety Lines trachea and

most of upper respiratory tract

Transitional EpitheliumDescription

Basal cells usually cuboidal or columnarSuperficial cells dome-shaped or

squamousFunction

stretches and permits distension of urinary bladder

Location Lines ureters, urinary bladder and part

of urethra

Transitional EpitheliumRelaxed state

Stretched state

Name three types of tissue, what they look at and a place where they can be

found.

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Glandular EpitheliumDucts carry products of exocrine

glands to epithelial surfaceInclude the following diverse glands

Mucus-secreting glands Sweat and oil glandsSalivary glandsLiver and pancreas

May be: unicellular or multicellular

Unicellular Exocrine Glands (The Goblet Cell)

Goblet cells produce mucin

Mucin + water mucus

Protects and lubricates many internal body surfaces

Types of Multicellular Exocrine Glands

What are the two types of stratified squamous

epithelial? Where can they be found?

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Where can simple cuboidal and stratified cuboidal be

found? What is the difference in the function

of each?

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