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Module 7 > Skin and wound healing > Flashcards

Skin and wound healing Flashcards

1
Q

What are the 2 possible outcomes of repair?

A

Regeneration and scarring

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2
Q

What is the defintion for regeneration?

A

Replacement of damaged tissue components and return to a normal state.

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3
Q

What cell types contribute to regeneration and how does this work?

A
  • Proliferation of differentiated cells that have survived the injury and retain the capacity to proliferate
  • Presence of tissue stem cells and their progenitors contribute to the restoration of tissues
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4
Q

TRUE/FALSE?
mammals have limited capacity for regeneration

A

TRUE

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5
Q

What is a scar?

A

Deposition of fibrous connective tissue

(occurs if tissues are incapable of regeneration)

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6
Q

What are 3 things required for repair?

A
  • Cell proliferation
  • Cell-cell interactions
  • Cell- extracellular matrix interactions
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7
Q

What is the name for continuously dividing tissues?

A

Labile tissues

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8
Q

Give examples of labile cells.

A

haematopoietic cells in bone marrow and the majority of surface epithelia

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9
Q

What type of tissues have cells that are quiescent and have only minimal proliferative activity in normal state?

A

Stable tissues

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10
Q

Give examples of stable tissues.

A
  • parenchyma of most solid tissues
    (e.g liver, kidney and pancreas)
  • Endothelial cells
  • Fibroblasts
  • Smooth muscle cells
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11
Q

What type of tissue is made up of cells that are considered to be terminally differentiated and non-regenerative in post-natal life?

A

Permanent tissues

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12
Q

Give examples of permanent cells.

A
  • Neurons
  • Cardiomyocytes
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13
Q

What is the function of the ECM?

A
  • Mechanical support (cell anchorage, polarity and migration).
  • Regulator of cell proliferation (binding and displaying growth factors)
  • Scaffolding for tissue renewal
  • Foundation for establishment of tissue microenvironments
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14
Q

What are the 2 forms of ECM?

A
  • Interstitial matrix
  • Basement membrane
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15
Q

Where is the interstitial matrix loacted?

A

In spaces between stromal cells in CT

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16
Q

What is the interstitial matrix synthesised by?

A

Mesenchymal cells
(such as fibroblasts, oesteoblasts and chondroblasts)

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17
Q

Where is the basement membrane located?

A

Situated around epithelial cells, endothelial cells and smooth muscle cells

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18
Q

What are the main constituents of the basement membrane?

A

Laminin and collagen type IV

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19
Q

What are the 3 basic components of the ECM?

A
  • Fibrous structural proteins (e.g collagen and elastin) for tensile strength and recoil
  • Water-hydrated gels (proteoglycans and hyaluronan) for compressive resistance and lubrication
  • Adhesive glycoproteins to connect ECM elements to one another and to cells
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20
Q

What are the 3 phases of repair?

A
  • Acute inflammatory phase
  • Proliferative phase
  • Remodelling phase
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21
Q

How long does the inflammation phase last?

A

96 hours or longer

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22
Q

How long does the proliferation phase last?

A

4 weeks or longer

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23
Q

What happens during the proliferative phase?

A
  • Formation of granulation tissue
  • Angiogenesis (neovascularisation)
  • Fibroplasia/ Desmoplasia
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24
Q

When does granular tissue formation form by?

A

2-5 days

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25
Q

What is granular tissue?

A

New connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process

26
Q

What are the 5 stages involved in angiogenesis during wound repair?

A
  1. Proteolysis of ECM
  2. Migration and chemotaxis
  3. Proliferation
  4. Lumen formation, maturation and inhibition of growth
  5. Increased permeability through gaps and transcytosis (oedema)
27
Q

When does collagen synthesis begin?

A

day 3-5 and continues for weeks

28
Q

What are the 2 steps involved in deposition of connective tissue?

A
  • Migration and proliferation of fibroblasts into the site of injury
  • Deposition of ECM proteins produced by fibroblasts
29
Q

What is deposition of CT orchestrated by?

A

Locally produced cytokines and growth factors
(including PDGF, FGF-2 and TGF-B)

30
Q

What is involved in the remodelling phase of wound repair?

A
  • Maturation and reorganisation of CT to produce stable scar tissue.
  • Progressive vascular regression
  • Remodelling of ECM by MMPs
  • Increase in collagen which is deposited along tension lines (increase in tensile strength
31
Q

What factors influence tissue repair?

A
  • Infection
  • Nutritional status
  • Age
  • Glucocorticoids
  • Mechanical factors
  • Poor perfusion
  • Foreign bodies
  • Type and extent of tissue injury
  • Underlying neoplasia
  • Location of injury
32
Q

What layer of the skin is the bulk of ECM located?

A

Dermis

33
Q

When would healing by first intention occur?

A

Only focal disruption of the epithelial basement membrane and death of only few epithelial and mesenchymal cells.

34
Q

Give examples of wounds that would heal by first intention.

A

Injury only involves epithelial layer or is a clean, uninfected surgical incision approximated by sutures.

35
Q

Within 24 hours what has happened if a wound is healing by first intention?

A
  • Neutrophils migrate to the clot and release proteolytic enzymes which clear the debris
  • Basal cells exhibit mitotic activity
36
Q

What happens between 24 and 48 hours in a wound healing by first intention?

A

Epithelial cells from both sides migrate and proliferate and deposit basment membrane as they progress

37
Q

What happens at day 3 in a wound healing by first intention?

A
  • Neutrophils replaced by macrophages
  • Granulation tissue formation commences (angiogenesis and ECM formation)
  • Epithelium continues to proliferate
38
Q

What happens at day 5 in a wound healing by first intention?

A
  • Peak of oedematous granulation tissue
  • Increase of collagen
  • Epidermis at normal thickness and starts to mature
39
Q

What happens during week 2 in a wound healing by first intention?

A
  • Continued fibroblast proliferation and collagen formation
  • Decrease of inflammtion, odema and vascularity (“blanching”)
  • Sutures removed at 10 days
40
Q

By the end of the first month what would usually be seen in a wound that has healed by first intention?

A
  • Normal epidermis
  • Collagenous scar
  • No inflammation
41
Q

Give examples of wounds that would heal via second intention.

A
  • Ulcerations
  • Lacerations
  • abscesses
  • ischemic necrosis
42
Q

What are features that are seen in a wound that is healing by second intention?

A
  • More intense inflammation
  • Abundant granulation tissue, acumlation of ECM and formation of a large scar
  • The wound contracts via myofibroblasts
  • Poor tensile strength
  • Wound may remain ulcerated
43
Q

What is a myofibroblast?

A

Modified fibroblast that contains smooth muscle cells

44
Q

Describe the CT in a wound that has healed by second intention.

A

Haphazardly formed and arranged (also lacks adnexa), which can also delay or prevent migration of epithelial cells

45
Q

By the end of the first month what is granulation tissue replaced by in a wound that has healed by second intention?

A

Acellular fibrous tissue devoid of inflammation which is covered by intact epidermis

46
Q

Upon the removal of sutures what % of strength is the wound compared to normal skin?

A

10%

47
Q

What is fibrosis?

A

Excessive deposition of collagen

48
Q

What is the major cytokine involved in fibrosis?

A

TGF-beta

49
Q

What is fibrosis associated with?

A

loss of tissue

50
Q

What is fibrosis a consequence of?

A

Persistent injurious stimuli
e.g chronic inflammation of infectious or immune mediated origin

51
Q

What can fibrosis lead to?

A

Organ dysfunction or even failure

52
Q

What is “proud flesh”?

A

Exuberant granulation tissue

53
Q

What animal is “proud flesh” typically seen and in what body part is it located?

A

Legs of horses

54
Q

What animal is more reliant on wound contraction from the edges of the wound?

A

cat

55
Q

What animal is more reliant on central pull and epithelialisation during wound healing?

A

Dogs

56
Q

Describe the initial inflammatory phase in horses.

A
  • Weaker
  • persists for longer
  • Excessive granulation tissue
  • Lower inital production of inflammatory mediators
57
Q

True/ False?
Differences between horses and ponies are more significant with limb wounds than body wounds.

A

TRUE

58
Q

How long should sutures remain in reptiles for?

A

4-6 weeks

59
Q

What wound heals faster in reptiles?
wounds orientated cranial to caudal or transverse wounds.

A

Transverse wounds

60
Q

True/False?
Ecdysis impairs healing.

A

FALSE
it promotes healing

Module 7 (10 decks)

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