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MoD > L6 - Repair and Regeneration > Flashcards

L6 - Repair and Regeneration Flashcards

1
Q

what is repair?

A
  • normal structure cannot be replaced
  • healing by non-specialised fibrous tissue (‘scar’)
  • functional consequences
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2
Q

what is regeneration?

A

Restoration of normal structure and function

cell can grow back

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3
Q

what are the 2 most important factors when determining the outcome of an injury?

A
  • ability of cells to replicate

- ability to rebuild complex architectural structures

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4
Q

features of labile cell populations?

A
  • continuously cycling
  • usually seen in epithelial structures
  • high turn over
  • active stem cell population
  • excellent regenerative capacity
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5
Q

features of stable (quiescent) cell populations?

A
  • leave the cell cycle but can re-join and regenerate at
    anytime
  • low turnover but can increase if needed
  • good regenerative capacity

eg liver, renal tubules

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6
Q

features of permanent cell populations?

A 
- divided and left the cell cycle and therefore cannot divide
anymore
- no turnover 
- long life cells 
- no regenerative capacity

eg, neurones, striated muscle cells

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7
Q

features of stem cell populations?

A
  • prolonged self-renewal
  • asymmetric replication
  • reservoirs present in adult tissues
  • stem cell pools present in labile and stable cell populations
  • specific areas eg basal layers of epidermis or bottom of intestinal crypts
  • crucial to regeneration
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8
Q

What is complete restitution?

A
  • Loss of labile cell population can be completely restored e.g. minor skin abrasion
  • Cells at edge of defect multiply to cover defect.
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9
Q

what is contact inhibition?

A

Once the cells at the edge cover defect, proliferation stops

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10
Q

what are the implications are scar tissue forming to replace myocardium?

A
  • decrease contractility, resulting in heart failure

- electrical conductivity problems, resulting in arrhythmias

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11
Q

what is organisation?

A

The repair of specialised tissue by formation of a fibrous scar

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12
Q

features of organisation?

A
  • Production of granulation tissue (often on scaffold of fibrin)
  • removal of dead tissue by
    phagocytosis
  • Granulation tissue contracts and accumulates collagen, forming a scar
  • Organised area – firm and puckered
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13
Q

features of granulation tissue?

A
  • New capillary loops
  • Phagocytic cells (Neutrophils, Macrophages)
  • (Myo)fibroblasts [which contract]
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14
Q

when is granulation tissue the most vascular?

A

Initially, the granulation tissue is very vascular and cellular.

over time, the vascularity and cellularity are lost and the wound becomes
much stronger because of the formation of collagen and ECM

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15
Q

features of healing by primary intention?

A
  • clean, unaffected surgical wound
  • good haemostats (not lots of bleeding)
  • edges apposed (eg with staples or sutures)
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16
Q

Process of healing by primary intention?

A
  • little or no skin loss
  • coagulated blood forms fibrin join (scab)
  • scab replaced my collagen that is covered by the epidermis growing over
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17
Q

features of healing by secondary intention?

A
  • extensive loss of tissue
  • apposition not possible
  • large haematoma
  • infection
  • foreign body
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18
Q

which healing method (by primary or secondary intention) results in ore florid granulation tissue reaction and more extensive scarring?

A

secondary

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19
Q

how long does it take a wound to become 70-80% of its normal strength?

A

3 months

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20
Q

which healing intention do ulcers heal by? (primary/secondary)

A

secondary

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21
Q

local factors that could inhibit healing?

A 
infection
haematoma 
blood supply 
foreign bodies
mechanical stress
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22
Q

systemic factors that could inhibit healing?

A 
age
drugs
anaemia 
diabetes 
malnutrition
catabolic states 
vitamin C deficiency 
Trace metal deficiency
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23
Q

how do steroids affect the healing process?

A

steroids interfere with formation of granulation tissue and are immunosuppressive

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24
Q

how does a vitamin C deficiency affect the healing process?

A

vitamin C deficiency affects collagen synthesis

25
Q

what is a keloid scar?

A

When there’s damage to underlying dermis of the skin, it can be followed by
an excessive fibroblast proliferation and formation of collagen

NB: genetically determined process

26
Q

features of a keloid scar?

A
  • difficult to treat
  • tough heaped up scar that rises above rest of skin
  • tend to enlarge progressively unlike normal scars
  • do not regress over time

Normally:

  • shiny
  • hairless
  • raised
  • hard and rubbery
  • red or purple at first before becoming brown or pale
  • painless
27
Q

healing process of a fracture?

A
  • haemorrhage around and within bone (haematoma)
  • phagocytosis of necrotic fragments
  • osteoblasts lay down disorganised bone (callus)
  • remodelling and replacement by more orderly bone (lamellar)
28
Q

non-union of fractures slows down healing and prevents functional results, can lead to arthritis and degenerative diseases.

Why does non-union of fractures occur?

A

misalignment

movement

infection

interposed soft tissue

pre-exisitng bone pathology e.g tumour

29
Q

what is gliosis?

A

proliferation or hypertrophy of several different types of glial cells

30
Q

where does gliosis occur and why?

A

occurs in the brain as a response to CNS damage (instead of scarring)

31
Q

why do cysts form in the brain after CNS damage?

A
  • Neurons are terminally
    differentiated
  • Supporting tissue is glial
    cells rather than collagen
    and fibroblasts etc –
    these can proliferate
  • Hence damaged tissue is
    removed, often leaving
    cyst
32
Q

what secretes EGF?

A

platelets
macrophages
saliva
plasma

33
Q

function of EGF?

A

stimulates granulation tissue formation

34
Q

what secretes TGF-β?

A 
platelets 
t-lymphocytes 
macrophages
endothethial cells
keritnocytes 
smooth muscle cells 
fibroblasts
35
Q

what is the function of TGF-β?

A 
- chemotactic 
stimulates; 
TIMP synthesis,
angiogenesis, fibroplasia, 
- inhibits production of MMPs and keratinocyte proliferation
36
Q

what secretes PDGF?

A 
platelets
macrophages
endothelial cells
keratinocytes
SMC
37
Q

what is the function of PDGF?

A
  • stimulates angiogenesis

- stimulates production of MMPs and fibronectin

38
Q

what secretes KGF?

A

fibroblasts

39
Q

what is the function of KGF?

A

stimulates keratinocyte migration, proliferation, and differentiation

40
Q

what secretes TNF?

A

macrophages
mast cells
T lymphocytes

41
Q

what is the function of TNF?

A

activates macrophages

regulates other cytokines

42
Q

what is the function of VEGF?

A

increases vascular permeability

mitogenic for endothelial cells

43
Q

what is mitogenesis?

A

Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen.

44
Q

what is the function of TGF-α?

A

similar to EGF; stimulates replication of hepatocytes and most epithelial cells

45
Q

which growth factor stimulates replication of hepatocytes?

A

TGF-α

46
Q

which growth factor increases vascular permeability?

A

VEGF

47
Q

which growth factor stimulates keratinocyte migration, proliferation and differentiation?

A

KGF

48
Q

which growth factor is mitogenic for fibroblasts, endothelial cells and SMC?

A

PDGF

49
Q

which growth factor is mitogenic for keratinocytes and fibroblasts?

A

TGF-β

50
Q

which growth factors are mitogenic?

A

TGF-β

PDGF

51
Q

which growth factor stimulates granulation tissue formation?

A

TGF-β

52
Q

which growth factors are secreted by macrophages?

A 
EGF
TGF-β
PDGF
TNF 
TGF-α
53
Q

Which growth factors are secreted by fibroblasts?

A

KGF

TGF-β

54
Q

which growth factors are secreted by keratinocytes?

A

TGF-β

TGF-α

55
Q

Which growth factors are secreted by platelets?

A

EGF
TGF-β
PDGF

56
Q

Which growth factors are secreted by T-lymphocytes?

A

TGF-α
TNF
TGF-β

57
Q

how is regeneration controlled?

A
  • proliferation of stem cells
  • covering of defect
  • contact inhibition
  • growth factors
58
Q

what is ulceration?

A

loss of the surface epithelium or the mucosa (full loss of mucosa)

MoD (19 decks)

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