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Mechanism of Human Disease > Healing & Repair > Flashcards

Healing & Repair Flashcards

1
Q

What are the possible outcomes of cell injury?

A
  • adaptation
  • repair
  • death
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2
Q

List mechanisms of repair.

A
  • regeneration
  • regeneration by connective tissue (scar formation)
  • both
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3
Q

Characterize regeneration repair.

A
  • occurs when connective tissue is still intact => serves as scaffolding
  • replacement by same cell type
  • mild injuries
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4
Q

Characterize scar formation repair.

A
  • occurs when connective tissue has been injured or injured cells do not have regenerative capabilities
  • replaced with collagen
  • severe injuries
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5
Q

Define labile cells.

A
  • continuously dividing
  • easily regenerate
  • ex: epithelium, mucosal linings
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6
Q

Define stable cells.

A
  • fixed in G0 stage
  • can regenerate when stimulated by growth factors to re-enter cell cycle
  • ex: liver, kidney, smooth muscle
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7
Q

Define permanent cells.

A
  • cannot regenerate

- cardiac, muscle, neurons

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8
Q

List components of scar formation (reparation by connective tissue)

A
  • angiogenesis
  • fibroblast proliferation
  • ECM deposition (by fibroblasts)
  • organization of fibrous tissue element
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9
Q

Which growth factor is an important mediator of angiogenesis? minor mediators?

A
  • VEGF

- PDGF, TGF-B, FGF are minor

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10
Q

Which growth factors are important mediators of fibroblast proliferation?

A
  • PDGF, FGF, TGFB
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11
Q

Define granulation tissue. What are the components?

A
  • in between stages of injury and scar; only present during healing
  • fills in defects where cells are non-regenerative or CT framework is destroyed
  • appears red and edematous

Components

  • proliferating fibroblasts
  • immature CT
  • angiogenesis
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12
Q

Define the process of organization.

A
  • transforming granulation tissue into a scar
  • over time, granulation tissue transforms to mature CT (collagen)
  • blood vessels become less prominent
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13
Q

List the steps in healing a skin laceration.

A
  1. injury
  2. inflammation
  3. blood clot (fibrin, fibronectin)
  4. regeneration of epithelium
  5. proliferation of fibroblasts, myofibroblasts, and macrophages in the defect
    ==> fibroblasts lay down collagen
    ==> myofibroblasts pull wound edges together
    ==> macrophages clean up debris, secrete cytokines
  6. angiogenesis
  7. over time, granulation tissue becomes filled with collagen, parenchymal cells, and acquires strength via vitamin C.
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14
Q

Describe healing by first intention (primary union).

A
  • wound is clean and inspected immediately
  • defect is small and limited
  • gap is closed with sutures, cleaned, and debrided
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15
Q

Describe healing by second intention (secondary union).

A
  • wound is large, infected, and patient has not been seen
  • no sutures; allow wound to granulate
  • clean and debride
  • occurs internally on organs as well
  • takes longer
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16
Q

How do the following local factors affect inflammation:

  • vascular supply
  • infection
  • foreign bodies
  • ionizing radiation
A
  • vascular supply: adequate blood supplied required for inflammation and healing; low blood flow = takes longer to heal, more prone to infection
  • infection: bacteria continues to incite inflammation…takes longer to heal
  • foreign bodies: intensifies inflammation and takes longer
  • ionizing radiation: decreases vascular supply..takes longer
17
Q

How do the following systemic factors affect inflammation:

  • circulation
  • infection
  • nutrition
  • hormones
A
  • circulation: poor circulation (CHF) impairs transport of O2, inflammatory cells, growth factors…takes longer
  • infection: overwhelms immune system…takes longer
  • nutrition: poor nutrition => deficiencies in wound healing factors (proteins, vitamin C, copper, zinc)
  • hormones: steroids inhibit inflammatory process…impaired healing (meds or cushing’s)
18
Q

List vitamins and mineral required for adequate wound healing and their roles.

A
  • vitamin C: collagen cross-linking
  • copper: cofactor for enzyme required for collagen cross-linking
  • zinc: cofactor for collagenase to break down collagen and keep building
19
Q

List complications of scar healing.

A
  • defective scar formation: dehiscence, incisional hernia

- excessive scar formation: keloids, hypertrophic scars

20
Q

Define dehiscence.

A

rupture of wound due to:

  • mechanical factors
  • infection
  • ischemic necrosis
21
Q

Define keloids.

A

accumulation of excess collagen beyond wound boundaries

  • hereditary
  • more common in african-americans
22
Q

Define hypertrophic scars.

A

excessive collagen deposition inside wound boundaries

- may regress

23
Q

Define ECM. List protein components.

A

network of interstitial proteins made of matrix and basement membranes

  • fibrous structural proteins: collagen, elastins
  • water hydrated gels; proteoglycan, hyaluranons
  • adhesive glycoproteins
24
Q

List pros and cons of scar formation.

A

pros - allows organ to keep functioning

cons - that particular region where the scar is no longer functions

25
Q

Define VEGF.

A

Vascular Endothelial Growth Factor

  • promotes angiogenesis, endothelial cell migration/proliferation, and increased vascular permeability
  • low levels in adults
  • high levels in glomerulus and retina
  • induced by hypoxia (angiogenesis can reperfuse an area during hypoxia)
  • if mutated, defective angiogenesis
26
Q

Describe the timeline of wound healing.

A
  • after 1 week, 10% strength regained
  • after 3 months, 70-80% strength regained
    never 100%
27
Q

Define fibrosis.

A

excessive collagen deposition in a tissue

28
Q

Define contracture.

A
  • typically in burns

- excessive contraction can lead to skin being fixed in a tight position

Mechanism of Human Disease (18 decks)

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