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Cell biology - BB10005 > lecture 14 - epithelia > Flashcards

lecture 14 - epithelia Flashcards

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1
Q

What are Epithelia?

A
  • avascular tissues compose of cells, usually organised into sheets or tubules , attached to an underlying EC, basement membrane
  • Cover both the internal and external surfaces of the body
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2
Q

How are some epithelia modified?

A

modified to form glandular structures

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3
Q

What are the 5 types of epithelia?

A
  • simple
  • stratified
  • Columnar
  • Cuboidal
  • squamous
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4
Q

What type of epithelial cellar kidney tubules made of

A

cuboidal

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5
Q

What type of epithelial cells are the small intestine made of?

A

columnar

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6
Q

What type of epithelial cells are the lung alveoli made of?

A

squamous

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7
Q

What type of epithelial cells is the oesophagus made of?

A

stratified

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8
Q

What are the 7 functions of the epithelia?

A
  • Mechanical protection
  • permeability barrier
  • absorption
  • filtration
  • secretion
  • Diffusion
  • Sensory
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9
Q

How are epithelia polarised?

A
  • apical

- basal

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10
Q

How are the epithelia polarised?

A
  • biochemically polarised
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11
Q

How is the physical integrity of the epithelium maintained?

A

Epithelia are held together by cell junctions

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12
Q

What are cell junctions?

A

A specialised site on a cell at which it is attached to another cell or the extracellular matrix

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13
Q

What is an anchoring junction?

A

linking cells together or to the extracellular matrix, maintain physical integrity

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14
Q

What is an occluding junction?

A

seal the gaps between cells, prevent the leakage of water

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15
Q

What is an channel - forming junction?

A

create passageways linking the cytoplasm of adjacent cells,

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16
Q

What is an signal - relaying junction?

A

allows signals to be communicated from cell to cell of the nervous system

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17
Q

Where are adherens junctions situated?

A

At the apical part of the cell

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18
Q

What are the main components that adheren junctions are made up of?

A
  • actin filaments
  • cadherin
  • a-catenin b-catenin
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19
Q

Where are desmosome junctions situated?

A

below the adherens junction

20
Q

What are desmosome junctions made up of?

A
  • intermediate filaments
  • cadherin
  • plakoglobin desmoplakin
21
Q

Purpose of the adherens junction

A

Adherens contain plaque which attaches to both membrane proteins and microfilaments of the cytoskeleton. Adherens help epithelial surfaces resist separation during various contractile activities

22
Q

purpose of desmosome junctions?

A

Link cadherins to intermediate filaments of the cytoskeleton

23
Q

purpose of focal adhesion junctions

A

Link cadherins to the actin filaments of the cytoskeleton

24
Q

What is the purpose of a hemidesmosome

A

Hemidesmosomes are multiprotein complexes that facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane.

25
Q

What are focal adhesions made up of?

A
  • actin filaments
  • integrin
  • Focal adhesion kinase
26
Q

What are hemidesmosomes made up of?

A
  • intermediate filaments
  • integrin/collagen
    dystonin
27
Q

What are the role of cadherins and where are they situated?

A
  • mediate cell to cell attachment and hold them together

- They are found between cells in the plasma membrane

28
Q

What is a use of the adhesion belt associated with actin filaments?

A
  • Causes invagination of the epithelial sheet caused by the tightening of the adhesion belt .
  • forms layers of cells and eventually an epithelial tube which can form many things such a neural tubes and even the brain
29
Q

What are the role of integrin molecules within hemidesmosomes

A

Play a role in mediating cell - matrix contacts , anchor the epithelial cells to the basal lamina

30
Q

What is keratin?

A

type of intermediate filament

31
Q

What is Pemphigus vulgaris an example of?

A
  • autoimmune destruction of the desmosomal protein
32
Q

What does Pemphigus vulgarisms cause?

A
  • severe blistering
  • dehydration and infection
  • potentially death
33
Q

What can occluding junctions be called?

A

Can be called an tight junction

34
Q

What do tight junctions/ occluding junctions do?

A

seal gaps between epithelial cells

35
Q

What are tight junctions/ occluding junctions made up of?

A
  • Claudin and occludin

- Zona occluding scaffold protein

36
Q

What are the two functions of tight proteins?

A
  • Barrier function (regulate passage of ions, water and macromolecules)
  • Fence function (Maintains cell polarity)
37
Q

How was it determined that occluding/ tight junctions help maintain cell polarity?

A

Take a fragment of epitheliem and placed in a aqeueos solution and then there is a tracer such as a salt
Process the sample and look for the tracer

Black area is the tracer , can only get so far to the tight junction

38
Q

What happens when there is a loss of barrier function In tight junctions?

A

Crohns disease - inflammation of the bowels , permeability disorder

39
Q

What happens when there is a loss of fence function in tight junctions?

A

Cancer - Loss of cell polarity and cell contacts (epithelial-mesenchymal transition - EMT), increase in motility and eventual metastasis

40
Q

What do gap junctions do?

A
  • allow ions and small molecules to pass directly from cell to cell
41
Q

What are gap junctions made up of?

A
  • 6 connexins form a connexon
  • 1 connexon pairs up with a connexon in another cell
  • They are organized as patches where you gave lots of connexons
  • The connexons can open and close
42
Q

What happens when there are abnormal gap junctions and what are the human inherited disorders?

A
  • cataracts

- Vohwinkel syndrome

43
Q

What are the names of channel forming junctions in plants called?

A
  • plasmodesmata
44
Q

What are the roles of neuralgia and neurexin in the synapse?

A

Neurexins and neuroligins are synaptic cell-adhesion molecules that connect pre- and postsynaptic neurons at synapses

45
Q

What is the role of cadherin in the synapse?

A

Also helps to hold the cells together

46
Q

What is Myasthenia Gravis?

A
  • autoimmune destruction of the neuromuscular junction

- first indication is a droopy eye

47
Q

What are epithelia?

A

Epithelia are avascular tissues composed of cells, usually organised into sheets or tubules, attached to an underlying ECM basement membrane

Cell biology - BB10005 (17 decks)

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