Practical 2 - Epithelia Flashcards

1
Q

What is the definition of an epithelium?

A

A cohesive sheet of cells with one or more layers, resting on a basement membrane.

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2
Q

What is the purpose of epithelia?

A

Form barriers for:

  • protection
  • absorption
  • secretion
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3
Q

Simple vs stratified epithelia?

A

Simple - single layer of cells resting on a basement membrane.

Stratified - two or more layers of cells on a basement membrane.

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4
Q

What type is gall bladder epithelium?

A

Simple columnar epithelium

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5
Q

What type is oesophageal epithelium?

A

Stratified squamous non-keratinising epithelium.

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6
Q

Where is simple squamous epithelium found?

A
  • blood vessel endothelium
  • mesothelium (outside of lungs)
  • peritoneum (outside of abdominal organs)
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7
Q

Where is simple cuboidal epithelium found?

A

Lines kidney tubules and small ducts.

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8
Q

Where is simple columnar epithelium found?

A

Lines stomach, intestines and uterus.

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9
Q

True or false: simple columnar epithelium can have cilia/microvilli?

A

True

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10
Q

What is the function of goblet cells in the small intestine?

A

Secrete mucin onto surface of epithelium as a lubricant.

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11
Q

How do cilia work? Where are they found?

A

Contain contractile proteins which enable them to beat rhythmically.
Respiratory tract & reproductive tract.

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12
Q

What are some features of stratified epithelium?

A
  • protective
  • many layers
  • continually worn down and replaced by cells from below
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13
Q

Where is stratified epithelium found?

A

Sites subject to abrasive forces: skin, mouth, oesophagus, vagina, cervix.

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14
Q

How are cells replaced in stratified epithelium?

A

Immature cells rest against basement membrane. Cells are pushed up to the surface as they mature by new cells forming beneath them.

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15
Q

What is the function of keratin?

A

Keratin waterproofs the epithelium.

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16
Q

How is stratified squamous epithelium keratinised?

A

As cells mature they accumulate keratin within their cytoplasm. Eventually they die from this accumulation which leaves flat plates of keratin at the surface of the epithelium.

17
Q

Example of stratified squamous keratinising epithelium?

A

Skin

18
Q

What is pseudo-stratified epithelium? Example.

A

Single layer of cells, all in contact with the basement membrane but have varying heights. This creates the appearance of multiple cell layers.

Respiratory epithelium.

19
Q

What is urothelium? Where is it found?

A

Specialised stratified (& pseudostratified) epithelium.

  • surface layer of umbrella cells not in contact with basement membrane.
  • several layers beneath the surface are in contact with the basement membrane but it’s uncertain exactly how many, could be a single pseudo-stratified layer.
  • lines collecting part of urinary tract: collecting ducts, bladder, etc.
20
Q

What is the basement membrane composed of? On which stain is the basement membrane visible?

A
  • extra-cellular proteins such as collagen IV and fibronectin
  • PAS stain needed to see it
21
Q

What are tight junctions? What is their function?

A

Band-like fusions between cells which are impervious to most molecules.
Prevents diffusion between cells.

22
Q

What are desmosomes? What is their function and where are they found?

A

Plaques that connect the cytoskeletons of adjacent cells, spreading forces across several cells.
Found in epithelia exposed to abrasive forces.

23
Q

What are gap junctions? What is their function?

A

Electrical junctions that permit the transfer of small molecules (e.g. ions) between adjacent cells.
Electrically couple adjacent cells.