specialised tissues Flashcards

epithelial specialisation: recognise how epithelial function (including absorption, secretion, fluid transport and protection) is determined by the type and organisation of epithelial cells and summarise patterns of cell division found in different epithelia

1
Q

what do epithelial cells require to function to ensure they are directional

A

polarity

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2
Q

what is key to having polarity

A

plasma membrane

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3
Q

what domains do junctions separate the epithelial membrane into

A

apical (open) and basolateral (matrix)

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4
Q

what allow directional flow and where are they located

A

polarised transporters restricted to specific parts of membrane

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5
Q

what do tight junctions do

A

seal paracellular pathway so any passage must be via cell, controlling passage

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6
Q

what is the fence function

A

maintains apical-basolateral polarity

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7
Q

epithelial specialisation: absorption - examples

A

nephron, small intestine, enterocytes

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8
Q

epithelial specialisation: absorption - requirements

A

absorptive, fluid transporting, selectively permeable, enterocytes possess striated brush border to increase SA

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9
Q

epithelial specialisation: absorption - direction of transport

A

apical membrane to basal lamina → capillary

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10
Q

epithelial specialisation: absorption - apical plasma membrane

A

many ion and water channels for passive transport

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11
Q

epithelial specialisation: absorption - basal lamina

A

mitochondria and membrane transporters for active transport (e.g. Na+/glucose coupling) at basal membrane infoldings (increase SA)

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12
Q

epithelial specialisation: secretion - examples

A

pancreas, goblet cells

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13
Q

epithelial specialisation: secretion - exocrine direction of transport

A

capillary → basal lamina to apical membrane

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14
Q

epithelial specialisation: secretion - exocrine

A

apical membrane leads to duct; secretory granules near apical membrane and RER and nucleus in basal cytoplasm

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15
Q

epithelial specialisation: secretion - endocrine direction of transport

A

apical membrane to basal lamina → capillary

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16
Q

epithelial specialisation: secretion - endocrine

A

secretory granules in basal cytoplasm; RER and nucleus near apical membrane; organised into glands (tubular and alveolar with varying complexities)

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17
Q

epithelial specialisation: protective - examples

A

skin epidermis (dry), lining of oesophagus (wet)

18
Q

epithelial specialisation: protective - function

A

barrier to environment and mechanical damage

19
Q

epithelial specialisation: protective - epidermal damage

A

defects cytokerains or cell-to-cell junctions leading to blistering diseases

20
Q

cell turnover: how tissue architecture is maintained

A

balance between proliferation and apoptosis

21
Q

why do turnover times vary

A

due to function

22
Q

how are intestinal absorptive villi replaced

A

cell renewal by stem cells in mid-region of intestinal crypts → cells lost from villus top → new cells move up from crypt to replace

23
Q

how is proliferation reduced

A

chemotherapy prevents stem cell production

24
Q

how is proliferation increased

A

benign tumour formation with malignancy risk

25
Q

what affects turnover

A

infectious agents and mechanical pressure

26
Q

tight junction: type of junction

A

Zonulae (belt)

27
Q

tight junction: location

A

many points where adjacent membranes form very close contacts

28
Q

tight junction: function

A

seal paracellular pathways and segregate membranes (establishing polarity)

29
Q

define kiss points

A

linear array that hook up with membrane proteins on adjacent cells

30
Q

adhesion belt: type of junction

A

Zonulae (belt)

31
Q

adhesion belt: location

A

basal to apical tight junction

32
Q

adhesion belt: component

A

cadherin (transmembrane adhesion molecule which associated with actin)

33
Q

adhesion belt: function

A

first to form and controls assembly of other junctions (“master junction”)

34
Q

desmosome junction: type of junction

A

Maculae (spot)

35
Q

desmosome junction: location

A

dotted between lateral membrane; abundant in epidermis

36
Q

desmosome junction: component

A

cadherin-like molecules for adhesion which link to intermediate filaments (cytokeratin in epithelium)

37
Q

gap junction: type of junction

A

Maculae (spot)

38
Q

gap junction: structure

A

cluster of pores continuous with adjacent pores

39
Q

gap junction: function

A

passage of ions and small molecules between cells

40
Q

diagram of epithelial tissue

A

diagram from tissues 1