Histology of Epithelial cells Flashcards by Clodagh cultra

What are the functions of epithelial cells?

-Barrier and protection
-Absorption
-Lubrication
-Movement: Cilia

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How are epithelial cells kept in place?

Adhesion to an underlay of proteins called the basement membrane

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What is the polarity of epithelial cells?

Polar

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What are the different surfaces of epithelial cells?

-Apical surface: top
-Lateral surface: sides
-Basolateral surface: bottom

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What are the pathways where passage can occur in epithelial cells?

-Paracellular route
-Transcellular route

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What are the proteins that stick epithelial cells together?

Tight junctions

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What is the role of epithelial cell junctions?

Controls the passage of substances between cells

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How does the trafficking of substances between cells occur?

Gap junctions

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How are gap junctions adapted for their function?

-Composed of connexin proteins
-1.5-2nm diameter to allow the passage of ions and small molecules

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What is a stratified cell arrangement?

Layered

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What is a single cell arrangement?

One cell thick

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What is a squamous cell shape?

Flat, ‘scale like’

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What is a pseudostratified arrangement?

False layered: only 1 cell thick but appears layered due to the misalignment of nuclei in columnar cells

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What is a cuboidal cell shape?

Square

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What is a columnar cell shape?

Tall, rectangular

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What is a simple squamour epithelium?

-Thinnest layer
-Cells are flat and spread out, large surface area

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Where is simple squamous epithelium present?

-Where transmembrane movement is advantageous
-E.g. alveoli in lungs for gas exchange
-E.g. Bowmans capsule to aid filtration

What are the advantages of simple squamous epithelium?

Supports efficient movement of substances in and out of the blood, due to large surface area

What are the disadvantages of simple squamous epithelium?

Does not provide much protection from mechanical abrasion due to being 1 cell thick

What is a simple cuboidal epithelium?

-An intermediate between squamous and columnar cells
-Cells have a greater cytoplasmic volume than squamous cells and therefore have more molecular components for more complex roles

Where is simple cuboidal epithelium found?

-Glands which specialise in secretion, e.g. kidney tubules
-Also line small ducts, e.g. pancreatic

What is a simple columnar epithelium?

-Cells are taller than they’re wide
-Nucleus is polarised towards the basement membrane (bottom of cell)

What is the role of simple columnar epithelium?

-Line harsh internal environments as can withstand wear and tear
-Can secrete large amounts of substances
-Can absorb large quantities of material

Where is simple columnar epithelium found?

-Harsh environments: Stomach and intestines
-Areas requiring lubrication: Intestines and stomach
-Lower GI tract

What is a stratified squamous epithelium?

-Multi-layered epithelium, cells on the outer layer are flat and scale like -Name chosen by cells on the apical (outer) layer as basal cells can vary in shape

Where is stratified squamous epithelium found?

Surfaces that are subject to high levels of mechanical abrasion

What happens to cells at the base of the layer in stratified squamous epithelium?

-Basal cells are regularly dividing and migrate up the strata replacing the cells on the top layer

What are the 2 varieties of stratified squamous?

-Wet (non-keratinising) -Dry (keratinising

What is keratinising stratified squamous epithelium?

-Produces keratin by keratinocyte cells -Top layer of cells are dead -Produces dry surface, protecting underlying surfaces

What is non-keratinising stratified squamous epithelium?

-Occurs in wet environments where abrasion is likely -Top layer of cells are alive -Producing a moist surface, protecting underlying surface

How to tell the difference between wet non-keratinising stratified squamous epithelium and dry keratinising stratified squamous epithelium under the microscope?

-In wet non-keratinising stratified squamous epithelium, the top cells are alive and therefore a nucleus will be present. -In keratinising stratified squamous epithelium the top cells are dead and no nucleus will be present

What is pseudostratified epithelial columnar cells?

-Cells are different heights producing misaligned nuceli -The presence of misaligned nuclei gives the impression it is stratified, but it is not -All cells in contact with BM

Where are pseudostratified epithelial columnar cells found?

Upper respiratory system due to flexibility so can move in and out when breathing

What is transitional epithelium?

-Stratified epithelium -Shape of cells at the luminal layer are difficult to discern

What are ciliated epithelial cells?

-Contain hair like projections -Helps move substances migrate across the epithelial layer

What causes cells to change shape in transitional epithelium?

-The epithelium changes shape to allow organs or tubes to increase in size and shrink

Where is transitional epithelium found?

Urinary tract

Where are ciliated epithelial cells found?

-Columnar epithelial cells -Common in respiratory tract: removes dust or microbes from lungs

What are epithelial cells with microvilli?

-Finger like protrusions on surface -Don't move, have a role in absorption

What is the role of microvilli?

Increase surface area for absorption of nutrients

What are goblet cells?

-Modified epithelial cells -Synthesise and secrete mucus

Where are goblet cells found?

Respiratory and gastrointestinal tracts