Exam 3 (Lecture 16) - Wound Healing and Angiogenesis Flashcards
What are the outcomes of tissue injury?
1) Injury > Cellular and vascular response > Stimulus removed = Regeneration of normal structure (with intact tissue framework ie basement membrane) OR Repair/Scar formation (with damage to framework)
2) Injury > Cellular and vascular response > Persistent tissue damage = Fibrosis/Scar tissue
What processes happen within 2 days of sustaining a wound?
1) Inflammation
2) Clot formation
3) Chemotaxis
What processes happen about 10 days later?
1) Proliferation
2) Re-epithelialization
3) Angiogenesis and granulation tissue
4) Provisional matrix
What processes happen 14-16 days later?
1) Maturation
2) Collagen deposition/collagen matrix
3) Wound contraction
- more stable/less movement
What are the goals of wound repair?
1) Reconstitute injured tissue to optimal morphology and function.
If that option is not achievable…
2) Replace injured tissue with viable tissue.
- Granulation tissue
- Fibrous tissue
What is first intension healing?
Healing by primary union (like healing that is seen with a surgical incision)
- Clean, incised
- Minimal infection
- Minimal foreign material
- Minimal scar tissue
- Within 3 months: 80% of normal strength
What does parenchymal repair depend on?
1) Capacity of residual cells to proliferate
2) Stromal preservation
- Two things must be intact:
- basement membrane
- blood supply
- If both of these are not present, the epithelial cells cannot return to the site and there will be no blood supply.
What are labile cells?
Renewing cells.
1) Epithelium
- skin
- gut
- cornea
2) Bone Marrow
What are stable cell?
1) Connective Tissue Cells
- fibroblasts
- endothelial cells
- bone
- cartilage
2) Epithelial Cells
- liver
- kidney
- exocrine pancreatic acini
What are permanent cells?
1) Myocardiocytes
2) Neurons
*We’re born with these and that’s it; we don’t get any more. Once they’re gone, they’re gone.
What is second intension healing?
Healing by secondary union.
- Wide defect; tissue loss; increased wound tension
- Edges are not brought back together easily b/c sutures won’t stay due to the skin tension
Delayed healing due to:
- increased necrotic debris
- foreign material
- infection
- present of exuberant granulation tissue (proud flesh)
What is wound repair by fibrous connective tissue?
Wound heals itself.
Most common type; functional though not pretty (the Dr. isn’t in control of the final outcome like with a surgical incision).
Damaged tissue replaced by granulation tissue > matures to fibrous CT (scar tissue).
What happens during wound repair by fibrous connective tissue?
Granulation tissue forms.
Connective tissue and fibroblasts form parallel to the skin surface.
Angioblasts and endothelial cells form perpendicular to the CT and fibroblasts.
+/- Macrophages, pmns
What are the 3 pathways of fibrosis in chronic inflammation?
1) PERSISTENT stimulus (chronic inflammation) > ACTIVATION of macrophages and lymphocytes > GROWTH factors (PDGF, FGF, TGF-beta) > PROLIFERATION of fibroblasts, endothelial cells, and specialized fibrogenic agents > INCREASED collagen synthesis > DECREASED collagen degradation = FIBROSIS
2) PERSISTENT stimulus (chronic inflammation) > ACTIVATION of macrophages and lymphocytes > CYTOKINES (TNF, IL-1, IL-4, IL-13) > INCREASED collagen synthesis = FIBROSIS
3) PERSISTENT stimulus (chronic inflammation) > ACTIVATION of macrophages and lymphocytes > DECREASED metalloproteinase activity > DECREASED collagen synthesis = FIBROSIS
What are factors that affect wound repair?
- Blood supply
- if no blood supply; no healing - Infection
- delays wound repair - Foreign body
- Wound stability
- Age
- young animal can heal quicker than an older one - Hormonal influences
- diabetes can prolong wound healing - Nutritional status
- vitamin C
- protein intake - Chemotherapeutic agents
