Pathology Wound Repair
Terms
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Healing by first intention
events within within 24 hrs. 4 events -
neutrophils appear at margins of incision, moving toward fibrin clot
- epidermis at cut edges thickens as a result of mitotic activity of basal cells
- spurs of epithelial cells from edges migrate and grow along cut margins of dermis depositing basement membrane
- fusion of epithelial cells at midline beneath the scab surface -
Healing by first intention
events by day 3. 4 events -
- neutrophils largely replace by macrophages
- granulation tissue progressively invades incision space
- collagen fibers are present in the margin of the incision
- epithelial cell proliferation continues, thickening epidermal covering layer -
healing by first intention events by day 5
5 events. -
- incisional space is filled with granulation tissue
- neovasculization is maximal
- collagen fibrils become more abundant and begin to bridge the incision
- epidermis recovers to normal thickness
- differentiation of surface cells yields a mature epidermal architecture with surface keratinization - healing by first intention events in second week. 2 events
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- continued accumulation of collagen and proliferation of fibroblasts
- leukocytic infiltrate, edema, and increased vascularity largely disappear - heaing by first intention events by end of first month. 4 events
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- scar comprises a cellular connective tissue devoid of inflammatory infiltrate
- covering of intact epidermis
- line of incision is lost
- tensile strength of would increases thereafter, but it may take months for the
wounded area to obtain its maximal strength - healing by secondary intention differences from healing by primary intention
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1) large tissue defects initially have more fibrin and more necrotic debris and exudates that must be removed; hence, the inflammatory reaction is more intense
2) much larger amounts of granulation tissue are formed.
3) wound contraction - myofibroblasts contribute to contraction - growth factors and cytokines which stimulate collagen synthesis in wound healing (3, 2)
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- growth factors: PDGF, FGF, TGF-beta
- cytokines: IL-1 and IL-4 - cell division growth factors (4)
- EGF, PDGF, IGF, FGF
- angiogenesis growth factors
- VEGF, FGF
- matrix modification growth factors
- TGF beta, CTGF
- types of fibrosis in wound healing
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 excessive accumulation of extracellular matrix
 keloid: benign overgrowth beyond the wound margin
 hypertrophic scar: disfiguring, but within the wound margin - four chronic wound types
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 decubitus ulcer (pressure sore)
- infarction of the skin over bony processes
 arterial ulcer
- insufficiency of blood supply
 venous (stasis) ulcer
- failure of valves to prevent lymphadema
 diabetic ulcer
- complication of hyperglycemia, atherosclerosis, impaired microcirculation, and hypoproliferation