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Anatomical pathology > TISSUE REPAIR > Flashcards

TISSUE REPAIR Flashcards

1
Q

healing and repair

A

•Healing
-minimal/no residual defect

•Repair

  • Occurs with tissue loss
  • Restoration of tissue architecture & function after injury
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2
Q

Repair is by two reactions

A
  1. Regeneration by proliferation of residual cells

2. Maturation of tissue stem cells and deposition of connective tissue

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3
Q

Regeneration

A
  • Components returning to normal state

* Occurs by proliferation of residual cells

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4
Q

Connective tissue deposition (Scar formation)

A

• Laying down of fibrous tissue that may result in a scar
• When tissue are incapable of complete restitution
• If supporting structures are severely damaged
• Fibrosis: extensive deposition of collagen as a consequence of chronic
inflammation: lungs, liver, kidney
• Organization: fibrosis in a tissue space occupied by an inflammatory
exudate.

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5
Q

Cell & Tissue Regeneration

A 
• Cell proliferation
• Growth factors 
• Critically dependent on:
- Integrity of the extracellular matrix
- Development of mature cells from stem cells
• Intrinsic proliferative capacity
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6
Q

Repair: Tissue types

A

3 Groups
• Labile (continuously dividing)
• Stable (G0)
• Permanent

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7
Q

Labile tissues

A

(continuously dividing)
• E.g. Haemopoietic cells, surface epithelia
• Readily regenerative after injury

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8
Q

Stable tissues

A
  • E.g. cells of solid organs like liver

* Proliferate only in response to injury or loss

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9
Q

Permanent tissues

A

(terminally differentiated)
• E.g.. Neurons/myocardium
• Injury is irreversible and results in scar

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10
Q

Signals of Cell Proliferation: Growth factors

A

• Multiple cell types/ cell-selective
• Produced by cells near the site of damage.
- Mainly Macrophages
- Epithelial & stromal cells
• Signaling pathways: proteins : cell cycle & release blocks on
checkpoints

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11
Q

Tissue stem cells

A 
• Supplement proliferation of residual cells
• Live in specialized niches
• Triggered by injury
• Differentiate into mature cells that 
repopulate the injured tissue
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12
Q

Repair by Connective Tissue Deposition (Scar formation)

A

• A response that “patches” rather than restores the tissue
• If repair cannot be accomplished by regeneration alone
• In combination with regeneration
• If the tissue injury is:
- Severe/chronic
- To parenchymal cells/epithelia + connective tissue framework
- In non-dividing cell

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13
Q

Steps in scar formation

A

• Angiogenesis

  • Formation of new blood vessels,
  • Supplying nutrients and oxygen: supporting repair

• Formation of granulation tissue:

  • Pink, soft, granular gross appearance
  • Migration + proliferation of fibroblasts
  • Deposition of loose connective tissue, together with the vessels & leukocytes
  • Remodeling of connective tissues
  • Production of a stable fibrous scar
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14
Q

Deposition of connective tissue

A

• Two steps:
1. Migration & proliferation of fibroblasts : site of injury
2. Deposition of ECM proteins produced by these cells
• Orchestrated by: Cytokines & Growth factors
- TGF-β (Transforming growth factor-β): most important cytokine
- PDGF, FGF-2

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15
Q

Remodeling of Connective Tissue

A

• Outcome of repair: Synthesis Vs degradation of ECM proteins
• After its deposition, the connective tissue in the scar continues to be modified
and remodeled.
• The degradation of collagens & other ECM components
- Family of matrix metalloproteinases (MMPs),(metal ions (e.g. zinc)
- Produced: fibroblasts, macrophages, neutrophils, synovial cells, &
some epithelial cells)
- Synthesis & secretion: growth factors, cytokines & other agents.

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16
Q

Factors influencing tissue repair

A
  • Infection
  • Diabetes
  • Nutritional status
  • Glucocorticoids(steroids)
  • Renal failure
  • Haematological disorders
  • Poor perfusion
  • Foreign bodies
  • Type and extent of tissue injury
  • Location of injury
  • Mechanical Factors/Movement
17
Q

Two clinically significant types of repair:

A
  • The healing of skin wounds (cutaneous wound healing)

* Fibrosis in injured parenchymal organs

18
Q

Healing of Skin wounds

A
  • First intention/primary union

* Second intention/secondary union

19
Q

healing by first intension

A

The mechanism of repair when injury involves only the epithelial layer

  1. Clot formation
  2. 24 hrs- neutrophils clear debris/basal proliferation
  3. 3 days- macrophages infiltrate and granulation tissue invasion
  4. 5 days-peak neovascularisation
  5. 2 weeks- Collagen deposition & fibroblast proliferation
    - Diminished inflammation and oedema
  6. 1 month- cellular Connective Tissue scar
20
Q

Healing by second intention

A

Extensive cell/tissue loss: large wounds, abscesses, ulceration and ischaemic
necrosis
1. Larger fibrin clot/more inflammation
2. More granulation tissue
3. Provisional matrix of fibrin, plasma, fibronectin and type III collagen
2 weeks-type 1 collagen: scaffold of pale, avascular scar-fibroblasts, dense collagen,
elastic tissue
4. 1 month-acellular CT covered by intact epidermis
5. Wound contraction

21
Q

fibrosisi in Parenchymal Organs

A

• Excessive deposition of collagen & ECM components
• Internal organs in chronic diseases
• Same as scar formation
• Chronic infections & immunologic reactions
• Associated with loss of tissue
• It may be responsible for substantial organ dysfunction and even
organ failure.
• TGF-β: necrosis/apoptosis& reactive oxygen species
• Myofibroblasts

22
Q

Abnormalities in Tissue Repair

A
  1. Inadequate formation of granulation tissue or formation of scar
    • Wound dehiscence
    • Ulceration
  2. Excessive formation of components of repair
    • Hypertrophic scars
    • Keloids
  3. Exuberant granulation
  4. Contractures

Anatomical pathology (13 decks)

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