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ANAT241 > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

What are tissues?

A
  • specialised cells embedded in an extracellular matrix
  • a functional arrangemt of cells
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2
Q

What do tissues form?

A

Organs

Which forms organs systems which form you

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3
Q

4 key types of tissues

A
  • epithelial tissue (lining/ secretion)
  • connective (support) tissue
  • muscle tissue (skeletal,smooth,cardiac)
  • nervous tissue
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4
Q

Cells have an internal cytoskeleton network of filaments for…

A

Shape, support and movement

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5
Q

Why do cells secrete extracellular matrix?

A

For support and structure and regulation of cell communication and behaviour

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6
Q

Cytoskeleton vs ECM staining

A
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7
Q

Two key functions of the ECM with examples

A

To maintain differentiated state of cells:
E.g mouse mammary gland epithelium cultured without ECM are flat and don’t produce milk

To maintain normal overall development:
E.g inactivation genes for ECM proteins results in defective skeletal development

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8
Q

Where is epithelial tissue found?

A
  • lines organs and cavities within the body
  • covers the external body (epidermis) (including from mouth to anus)
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9
Q

What is the function of epithelial tissue?

A
  • protective barrier
  • absorptive and secretory adaptions
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10
Q

Features of epithelial tissue

A
  • has polarity (apical and basal surfaces)
  • has basement membrane as a scaffold and anchor to underlying connective (support) tissue
  • Avascular (nutrients via diffusion)
  • Regenerative (stem cells allow regeneration)
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11
Q

How do u classify epithelium

A

Based on morphological criteria
- cell shape (squamous, cuboidal, columnar)
- number of cell layers (simple, stratified, pseudo stratified, transitional)

Based on surface specialisations
- micro vili
- cilia

Based on whether surface (covering) or glandular (secretory)
- glandular epithelium can be single cells or grouped into glans to allow focused production of a secreted product

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12
Q
A
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13
Q

How are epithelial cells connected?

A

Cellular junctions

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14
Q

3 classifications of cellular junctions that connect epithelial cells

A
  • occluding
  • anchoring
  • communicating
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15
Q

1 example of an occluding cellular junctions in epithelial cells

A
  • tight junctions (zonula occludens)
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16
Q

3 examples of anchoring cellular junctions

A
  • zonula adherens
  • desmosomes
  • hemidesmomes
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17
Q

1 example of communicating cellular junctions

A
  • gao junctions
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18
Q

Epithelial cellular junctions

A
  • tight junctions (zonula occludens)
  • zonula adherens
  • desmosomes
  • hemidesmosomes
  • gap junctions
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19
Q

What are tight junctions

A

Tightly bound junctions at apical region

(Protects paracellular pathway)

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20
Q

What do zonula adherens do?

A

Strengthens attachments to neighbouring cells at apical region

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21
Q

What do gap junctions allow?

A

Communication between neighbouring cells

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22
Q

What do desmosomes do?

A

Firmly anchor neighbouring cells together

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23
Q

What do hemidesmosomes do?

A

Anchors cell to basement membrane

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24
Q
A
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25
Q

Junctional complex

A
  • ## tight, zonula adherens and desmosomes all in close proximity

(On electron micro-graph, the darker a region is the denser and stronger it is hence the appearance of the desmosome)

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26
Q

When do tight junctions control?

A

The paracellular pathway

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27
Q

Another name for tight junctions

A

Zonula occludens

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28
Q

What so tight junctions contain?

A
  • transmembrane proteins
    • occludin
    • Claudins

(Different proteins in different cells to control what gets through and what doesn’t - changes in different areas of tissue)

29
Q

Different Claudine = different _______ in different _______

A

Permeabilities
Tissues

30
Q

Why are claudins so important - KIDNEYS

A

In kidney, only specific regions are permeable to Mg2+ ions due to Claudin-16

Mutation to Claudine-16 gene = abnormal claudin-16 resulting in a junction impermeable to ion

This results in low Mg2+ reabsorbiton back into the blood
- magnesium deficiency
- kidney damage/renal failure

31
Q

What is claudin-1 responsible for?

A
  • waterproof qualities of skin
  • mice lacking gene for claudin-1 died at birth due to dehydration
32
Q

What do zonula adherens do?

A
  • links cytoskeltons to adjacent cells
33
Q

What do zonula adherens contain?

A
  • actin microfilaments (connects to)
  • main transmembrane proteins
    • E-Cadherins
34
Q

What is E-Cadherins linked to?

A

Matastasis of cancer cells

35
Q

Malignant cells have lower levels of ________ expression

A

E-cadherin

36
Q

Why are Cadherins so important?

A

Loss of E-cadherins is linked to metastasis of cancer cells

37
Q

What do desmosomes do? And what do they connect to?

A
  • link cytoskeletoms of adjacent cells
  • connect to cytokeratin (intamediate filaments) (stronger then actin)
38
Q

What do desmosomes contain ?

A

TRANSMEMBRANE PROTEIMNS Cadherins such as desmoglein

39
Q

What is pemphigus vulgaris?

A
  • autoimmune disease
  • antibodies attack desmoglein 3 which keeps cells bound together (part of a desmosome)
  • cells fall apart, skin sloughs off
  • Cadherins are imperative for maintaining structural integrity of epithelium
40
Q

Cadherins are important for mainigning _____ integrity of ______

A

Structural
Epithelium

41
Q

What are hemidesmosomes and where are they found?

A
  • modified (half) desmosomes
  • found on basal surface of cell
42
Q

What is the purpose of hemidesmosomes?

A
  • to anchor to basement membrane

(Stop cells peeling off form underlying tissue)

43
Q

What do hemidesmosomes bind to?

A

Cytokeratin

44
Q

What do hemidesmosomes contain? Main transmembrane protein

A

Integrins

45
Q

What are gap junctions

A

Communicating junctions

46
Q

What do gap junctions contain ? main transmembrane proteins?

A
  • conexins
    • form channels called connexons that can open/close
    • allow passage of ions and small molecules
47
Q

What do connexins do?

A
  • form channels called connexons that can open/close
  • allow passage of ions and small molecules
48
Q

Epithelial tissue is _____

A

Polarised

49
Q

Epithelial cells have an ____ and ____ surface

A

Apical
Basal

50
Q

What are microvili ?

A

Fingerlike projections of plasma membrane

51
Q

How long are microvili?

A

Very short - 0.5 - 1 um

52
Q

What is the purpose of microvili?

A
  • provides increases surface area e.g for absorption (intestine, kidney)
53
Q

What is the core of microvili made of?

A

Parallel actin bundles

54
Q

What part of microvili can you see under light microscopy?

A

Brush boarder

55
Q

What part of microvili can you see through electron microscopy ?

A

Individual microvili with shape maintained by actin filaments

56
Q

Two different forms of cilia and what they are for

A

Non-motile: sensory information
Motile: beat in rhythm to move substances across
- e.g. respiratory tract
- sperm flagellum = modified cilium

57
Q

How long are cilia

A

Up to 10um long (half a cell length)

58
Q

What gives cilia its strength

A
  • has a cytoskeleton composed of a core of microtubules
59
Q

Apical characteristics of epithelial cells

A
  • cilia
  • microvili
60
Q

What does the basement membrane do?

A
  • binds epithelial cells to connective tissue
  • forms barrier but allows nutrients to pass to epithelia, regulated permeability.
  • controls growth and differentiation
61
Q

What is the basement membrane

A

Sheet-like arrangement of ECM proteins

62
Q

What is the basement membrane formed by?

A
  • both epithelia and connective tissue
63
Q

What can you see of the basement membrane under light microscope

A
  • not easily distinguished with H&E staining
  • immunocytochemisty can be used to stain specific components (e.g collagen IV labelled with immunogold)
64
Q

What can you see of the basement membrane under electron microscopy ?

A
  • 3 layers are visible
  • lamina lucida
  • lamina densa (aka basal lamina)
  • lamina fibroreticularis
65
Q

What are the purpose of basal folding?

A

Increases surface area on basal surface of cell

66
Q

What structures allow epithlium to act as a protective barrier?

A
  • junctional complexes - holds epithelium as a sheet
  • basement membrane - anchoring sheet and control in permeability through to the underlying tissues
67
Q

What structures allow epithelial cells to absorb substances from apical surfaces and pass on to underlying tissues?

A
  • microvili
  • basal folding
  • basement membrane
68
Q

Practivce questoiuns

A

ANAT241 (29 decks)

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