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PSC2002 Membrane Transport & Cell Signalling > PSC2002/L04 Structure & Function of Epithelia > Flashcards

PSC2002/L04 Structure & Function of Epithelia Flashcards

1
Q

Describe the structure of epithelia.

A

Sheet-like structure
Line external and internal surfaces
Internal called endothelium

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2
Q

What percentage of human cancers originate from epithelial origin?

A

85%

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3
Q

Give 3 functions of epithelia.

A

Protection
Filtration (kidney tubule lining)
Exchange (alveoli)
Absorption (intestine)
Sensation (taste)
Secretion (gland lining)

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4
Q

What is the function of simple squamous epithelia? (3)

A

Absorption
Filtration
Minimal barrier to diffusion

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5
Q

Where is simple squamous epithelium found? (2)

A

Capillaries
Abdominal and pleural cavities (mesothelium)

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6
Q

What is the function of simple cuboidal epithelia? (2)

A

Secretion
Transportation

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7
Q

Where is simple cuboidal epithelium found? (3)

A

Glands & ducts
Kidney tubules
Ovaries

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8
Q

Which kind of epithelium can be ciliated or non-ciliated?

A

Simple columnar

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9
Q

What is the function of simple columnar epithelia? (3)

A

Absorption
Protection
Secretion

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10
Q

Where is simple columnar epithelium found?

A

Digestive tract

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11
Q

What is the function of stratified squamous epithelia?

A

Protection

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12
Q

Where is stratified epithelium found? (4)

A

Skin
Mouth
Upper throat
Oesophagus

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13
Q

Which kind of epithelia can be keratinised or non-keratinised?

A

Stratified squamous

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14
Q

What is the function of pseudostratified columnar epithelia? (2)

A

Absorption
Protection

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15
Q

Where is pseudostratified columnar epithelium found? (2)

A

Upper respiratory tract
Trachea

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16
Q

Where is transitional epithelia found? What is its function?

A

Bladder
Stretchable layer

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17
Q

How do epithelia form a functional unit?

A

Attached to extracellular matrix of basal lamina

18
Q

Give 3 specialised structures that link epithelial cells to one another.

A

Tight junctions
Anchoring junctions
Channel forming junctions

19
Q

Describe tight or occluding junctions. (3)

A

Membrane proteins seal adjacent cells together
Ensure molecules cannot leak freely between cells
Prevent lateral migration of membrane proteins (creating membrane domains/polarity)

20
Q

What is the difference between claudins and occludins?

A

Claudins have multiple isoforms
Claudins create physical barrier that regulate permeability
Occludins are single type of protein
Role of occludins less clear

21
Q

What does the resistance of epithelia correlate to?

A

Leakiness of epithelia
High resistance = tight junction

22
Q

What defines whether an epithelial junction is tight or leaky?

A

Presence of Cld3 or Cld3 with Cld1
Cld1 + Cld3 = tight
Cld1 + Cld2 = leaky

23
Q

How is Claudin-2 introduced into Madin-Darby Canine Kidney I cells?

A

Using mRNA

24
Q

What is the function of anchoring junctions? (3)

A

Provide mechanical stability
Anchor cells to basal lamina and other cells
Allows functioning as a cohesive unit

25
Q

What are anchoring junctions categorised by?

A

Type of cytoskeletal filament they interact with

26
Q

What are:
a) cell-cell
b) cell-basal lamina
actin junctions called?

A

a) Adherens junction
b) Focal adhesion

27
Q

What are
a) cell-cell
b) cell-basal lamina
intermediate junctions called?

A

a) Desmosomes
b) Hemidesmosomes

28
Q

Describe the basal lamina. (2)

A

40-120nm thick
Strong, flexible foundation underlying all epithelia

29
Q

What 4 materials make up the basal lamina?

A

Laminin
Type IV collagen
Entactin
Perlecan

30
Q

What is the basement membrane?

A

Combination of basal lamina and reticular lamina

31
Q

What is the reticular lamina mainly composed of?

A

Type II collagen

32
Q

What is the function of gap/channel-forming junctions? (2)

A

Allow diffusion between cells
Enable cell-cell communication

33
Q

What is an Ussing chamber used for? (2)

A

Measure resistance of ion transport
Determine what ion channels are present (and concentration/expression)

34
Q

Why is frog skin a good model system?

A

Frogs are able to absorb Na+ from salty water across skin

35
Q

What happens when frog skin is dissected and mounted as a flat sheet containing solution of identical composition?

A

Transepithelial potential difference due to active transepithelial movement

36
Q

What happens when an epithelial cell is polarised?

A

Transepithelial voltage generated

37
Q

What is the equation for transepithelial voltage?

A

V(te) = V(bl) - V(ap)

38
Q

What is the voltage outside and inside of the epithelia?

A

Apical -158mV
Basolateral 0mV

39
Q

What is the voltage inside of the epithelia?

A

-92mV

40
Q

What is amiloride used for?

A

Chemical probe for apical Na+ channel?

41
Q

What is ouabain used for?

A

Na+/K+ ATPase inhibitor

42
Q

What is barium used for?

A

Blocking K+ channels

PSC2002 Membrane Transport & Cell Signalling (12 decks)

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