stratified epithelium

classification of stratified lining / covering epithelia

stratified epithelium is formed of many what?

formed of many layers of cells (3 or more layers)

how is the stratified epithelium named?

it is named according to the most superficial cell

What are the five types of stratified epithelium?

1. stratified squamous epithelium (superficial cells are squamous)

2. stratified columnar epithelium

3. stratified columnar ciliated epithelium (superficial cells are columnar ciliated)

4. stratified cuboidal epithelium

5. transitional epithelium (the superficial cells are broad cuboidal)

What is the stratified squamous epithelium?

• it is a thick type of stratified epithelium, formed of many layers of cells, one above the other.

• the number of layers ranges from 5 to 30 layers of cells

where do the cells of the stratified squamous epithelium lie?

the cells rest on the basement membrane

what are the basal cells formed of in the bottom layer of stratified squamous tissue?

• they are formed of columnar cells, with an oval basal nuclei

• from these basal cells, the other layers germinate

What is the intermediate layer of stratified squamous epithelium formed of?

polygonal cells

What is the superficial layer of stratified squamous epithelium cells formed of?

flat, squamous cells, which may or may not be nucleated.

what are stratified squamous epithelium cells exposed to?

they are exposed to the air

what is under the basement membrane?

connective tissue that contains blood and lymph vessels

nonkeratinized stratified squamous epithelium

• several layers of cells; the surface-most layer possess nuclei

• lines wet cavities

  • mouth

  • esophagus

  • vagina

• in areas where water loss is not a problem, the flattened cells of the epithelial surface layer living cells that contain much less keratin, and retain their water

keratinized stratified squamous epithelium

• layer of cells composing the free surface are dead, non-nucleated, and filled with keratin

• forms the epidermis of the skin

• composed of keratinocytes (synthesizes keratin intermediate filament proteins, which gives the epidermis its toughness)

what is the stratified columnar epithelium?

• similar in structure to stratified squamous but:

  • its layers are less in number

  • the superficial cells are non-keratinized columnar cells

where is the stratified columnar epithelium present in?

1. conjunctiva of the eye

2. large ducts of the glands

3. recto-anal junction

what is the stratified columnar epithelium ciliated?

• similar in structure to the stratified squamous, but:

  • formed of fewer layers of cells

  • the superficial cells are non-keratinizing columnar ciliated cells

where is the stratified columnar epithelium ciliated present in?

1. fetal esophagus

2. nasal surface of soft palate

3. laryngeal surface of epiglottis

what is the stratified cuboidal epithelium?

when the free surface of the stratified of the epithelium is covered with cuboidal cells, it is called stratified cubical

where is the stratified cuboidal epithelium present in?

1. ducts of sweat glands

2. tubules of the testes

What is the transitional epithelium?

• a stratified type of epithelium, which is present in the urinary tract

• its superficial cells are cuboidal in shape, with convex outer surfaces and concave inner surfaces

• the superficial cells are covered with a mucous like substance and a protective membrane

what does the membrane around the superficial cells of transitional epithelial cells do?

• this membrane acts as an osmotic barrier between urine and tissue fluids.

• it also protects the epithelium from the high acidity or high alkalinity of urine

What is the basal cell layer of the transitional epithelium formed of?

the basal layer is formed of high cuboidal cells

What are the intermediate cells of the transitional epithelium formed of?

• the intermediate cells, which are present between the basal and superficial layers, are polyhedral cells

• they are separated from each other by a mucus-like substance in their intercellular spaces

what does the presence of the mucous substance between the cells in the transitional epithelium do?

• it facilitates the gliding of cells on each other, so the transitional epithelium may be formed of 3 to 4 layers only in full distended urinary bladder

• OR it may be formed of 6 to 8 layers in an empty bladder

what can the superficial cells of the transitional epithelium change into?

when the bladder is filled with urine, they can change into squamous cells temporarily

where is the transitional epithelium present in?

1. minor and major calyces of the kidney

2. pelvis of the ureter, the ureter and the urinary bladder

3. the prostatic part of the male urethra and the inner part of the female urethra