ANAT241 Lecture 8 - Epithelial Tissue and Cell Membrane Specialisations Flashcards

1
Q

what are tissues?

A

tissues are specialised, similar cells embedded in an extracellular matrix (ECM)

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2
Q

what are the 4 tissue types?

A

epithelial tissue
connective (support) tissue
muscle tissue
nervous tissue

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3
Q

what are cells composed of?

A

an internal cytoskeleton network

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4
Q

what is the function of the internal cytoskeleton network?

A

for shape, support and movement

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5
Q

what do cells secrete?

A

extracellular matrix (ECM)

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6
Q

why do cells secrete extracellular matrix?

A

for support, structure, regulation of cell communication and behaviour

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7
Q

where does epithelial tissue line?

A

lines organs and cavities within the body and covers the external body as the epidermis

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8
Q

what is epithelial tissue?

A

a protective barrier with absorptive and secretory adaptations that has polarity with an apical and basal surface and a basement membrane that acts as a scaffold to underlying connective (support) tissue

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9
Q

how does epithelial tissue acquire nutrients?

A

epithelial tissue is avascular and therefore acquires nutrients via diffusion

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10
Q

what allows the regeneration of epithelial tissue layers?

A

stem cells

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11
Q

what 3 criteria is epithelia classified based on?

A

classified based on cell shape
the number of cell layers
cell surface specialisations

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12
Q

what are the 3 types of epithelial cell shape?

A

squamous
cuboidal
columnar

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13
Q

what are the 4 types of epithelial cell layers?

A

simple
stratified
pseudo-stratified
transitional

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14
Q

what are the 2 epithelial cell surface specialisations?

A

microvilli and cilia

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15
Q

what are microvilli?

A

finger-like projections of the plasma membrane

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16
Q

what is the size of microvilli?

A

they are short between 0.5um and 1um

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17
Q

what is the function of microvilli?

A

increase the surface area for absorption in the intestine and kidney

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18
Q

what are microvilli composed of?

A

composed of a core of parallel actin bundles

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19
Q

what do microvilli appear as under light microscopy?

A

appear as a brush border

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20
Q

what do microvilli appear as electron microscopy?

A

appear as individual microvilli

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21
Q

what is the shape of microvilli maintained by?

A

maintained by actin filaments

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22
Q

what are cilia composed of?

A

a cytoskeleton with a core of microtubules

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23
Q

what is the size of cilia?

A

they are half of the cell length as they are upto 10um long

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24
Q

what is the function of non-motile cilia?

A

to provide sensory information

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25
Q

what is the function of motile cilia?

A

to beat in rhythm to move substances across the surface of epithelium

26
Q

what is an example of motile cilia?

A

cilia in the respiratory tract or sperm flagellum

27
Q

what are modified cillium?

A

sperm flagellum

28
Q

what are epithelial cells connected together by?

A

connected via cellular junctions

29
Q

what are the 3 types of cell junctions?

A

occluding junctions
anchoring junctions
communication junctions

30
Q

what are the 2 types of occluding junctions

A

tight junctions

zonula occludens

31
Q

what are tight junctions?

A

tightly bound junctions at the apical region of a cell

32
Q

what do tight junctions control?

A

control the paracellular pathway through the transmembrane proteins of occludens and claudins

33
Q

what is the function of claudins?

A

different provide different permeabilities in different tissues

34
Q

what is the function of claudin-1?

A

claudin-1 is responsible for the waterproof qualities of the skin

35
Q

what is claudin-16 responsible for?

A

responsible for permeability to Mg2+ ions in specific regions of the kidney

36
Q

what does a mutation in the claudin-16 gene result in?

A

results in an abnormal claudin-16 causing the tight junction to be impermeable to the Mg2+ ion

37
Q

what is the effect of low Mg2+ reabsorption?

A

low Mg2+ reabsorption back into the blood results in a deficiency causing kidney damage/renal failure

38
Q

what are the 3 types of anchoring junctions?

A

zonula adherens
desmosomes
hemidesmosomes

39
Q

what is the function of zonula adherens?

A

to strengthen the attachment to neighbouring cells at the apical region by linking the cytoskeleton of adjacent cells through the main transmembrane protein of E-cadherins attached to actin microfilaments via anchoring proteins

40
Q

why are cadherins important?

A

the loss of E-cadherins has been linked to the metastasis of cancer cells

41
Q

what is the relationship between malignant cancer cells and E-cadherins?

A

cancer cells have lower levels of E-cadherin expression

42
Q

what is another name for desmosomes?

A

macula adherens

43
Q

what is the function of desmosomes?

A

to firmly anchor neighbouring cells together by linking the cytoskeletons of adjacent cells by connecting to the intermediate filaments of cytokeratin

44
Q

what is the main transmembrane protein in desmosomes?

A

cadherins such as desmoglien

45
Q

what are hemidesmosomes?

A

modified desmosomes on the basal surface of cells

46
Q

what is the function of hemidesmosomes?

A

to anchor cells to the basement membrane by binding to cytokeratin

47
Q

what is the main transmembrane protein of hemidesmosomes?

A

integrins

48
Q

what is a type of communication junction?

A

gap junctions

49
Q

what is the function of gap junctions?

A

communication between neighbouring cells

50
Q

what is the main transmembrane protein of gap junctions?

A

connexins

51
Q

what is the function of connexins?

A

connexins form channels called connexons that can open/close to allow the passage of ions and small molecules

52
Q

what are connexons?

A

connexin channels that open/close to allow the passage of ions and small molecules

53
Q

how is epithelial tissue linked?

A

linked as sheets through lateral junctions and linked to the basement membrane via junctions

54
Q

what is the function of the basement membrane?

A

the basement membrane binds epithelial cells to connective tissue and form a barrier that allows nutrients to pass to epithelia to regulate permeability controlling growth and differentiation

55
Q

what is the basement membrane?

A

sheet-like arrangement of ECM proteins that if formed and maintained by both epithelia and connective tissue

56
Q

what is the relationship between the basement membrane and the light microscope?

A

under light microscope the basement membrane is not easily distinguished with H&E staining but immunocytochemistry can be used to stain specific components
e.g collagen

57
Q

what are the 3 layers of the basement membrane?

A

lamina lucida
lamina densa (basal lamina)
lamina fibroreticularis

58
Q

what can be seen under the electron microscope in terms of basement membrane?

A

the 3 layers of lamina lucida, lamina densa (basal lamina) and the lamina fibroreticularis

59
Q

where are basal foldings present?

A

present on the basal surface

60
Q

what is the function of basal foldings?

A

to increase the surface area on the basal surface of a cell

61
Q

what are the structures that act as a protective barrier in epithelium?

A

the basement membrane and junctional complexes that hold epithelium as a sheet

62
Q

what is the dual function of microvilli, basal foldings and the basement membrane?

A

structures that absorb substances from the apical surface and pass it onto to the underlying tissues