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105 Cards in this Set
- Front
- Back
Define clean wound:
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surgical wounds under aseptic conditions
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Define clean-contaminated wound:
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surgical wounds entering respiratory, gi, urogenital tract entered under controlled conditions without unusual contamination
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Define contaminated wound:
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open, acute, accidental or surgical wounds with major break in sterile technique
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Define infected wound:
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wounds with old, devitalized, or have gross contamination with foreign debris
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What are wound classifications based on time?
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I- less than 6 hrs with minimal contamination II- 6-12 hrs with significant contaminiation III- longer than 12 hrs with gross contaminiation
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What are the phases of wound healing?
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Inflammatory (lag) , proliferative, remodeling (maturation)
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What is initiated immediately in the inflammatory phase?
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Hemostasis (via vasoconstriction, platelet aggregation, fibrin deposition)
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What mediated the reflex vasoconstriction during the inflammatory phase?
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Release of endothelin and thromboxane A2 from injured vessels and serotonin released from platelets results in smooth muscle contraction
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How long does reflex vasoconstriction of vessels last in the inflammatory phase?
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5-10 min
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What occurs after reflex vasoconstriction early in the inflammatory phase?
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Vasodilation; diapedesis of cells, fluid and protein into the wound
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What is the provisional wound matrix?
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Early wound clot consisting of polymerized fibrin fibers
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What occurs at the wound if it is left unbandaged?
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Clot dessicates, provisional wound matrix is replaced by granulation tissue beneath scab
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What amplifies the early inflammatory phase?
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Activated platelets within the fibrin plug
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What mediators are released by activated platelets to amplify the early inflammatory phase?
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Platelet derived growth factor, transforming growth factor B
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What are the 1st cell types to enter the wound in large numbers?
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PMN
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What is the role of neutrophils in early inflammatory phase?
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Remove damaged tissue & bacteria; release chemoattractants to augment inflammatory response
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What are the principal degradative proteins released by PMN in inflammatory phase?
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Cathepsin G, neutrophil specific interstitial collagenase, neutrophil elastase
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When do monocytes enter the wound?
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24 hours after wounding
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What cells are the major inflammatory cells regulating wound repair?
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Macrophages
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How do macrophages regulate wound repair in the inflammatory phase?
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Release ROS, cytokines, growth factors; remove necrotic tissue & bacteria; tissue debridement via release of proteinases
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What proteinases are released by macrophages in the inflammatory phase?
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Elastase, collagenase, plasminogen activator
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What initiates the proliferation phase?
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Release of tissue growth factors by macrophages
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When does the proliferation phase begin?
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Approximately 3rd day after wounding
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What processes occur during the proliferation phase?
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Angiogenesis, fibrous & granulation tissue formation, collagen deposition, epithelialization, wound contraction
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What initiates angiogenesis?
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Decreased oxygen tension, increased lactate, low pH within wound
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What does vascular outgrowth during angiogenesis require?
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Endothelial cell proliferation
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What mediators regulate neovascularization during angiogenesis?
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Vascular endothelial growth factor, basic fibroblast growth factor
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When does production of angiogenic factors stop?
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When macrophages/ GF producing cells are no longer in hypoxic, lactic acid environment
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What cells mediate fibrous and granulation tissue formation in the proliferation phase?
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Fibroblasts
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When do fibroblasts arrive at the wound during the proliferation phase?
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2nd day after wounding
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When do fibroblast populations peak within the wound during the proliferation phase?
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7-14 days after wounding
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What mediates fibroblast migration to the wound in the proliferation phase?
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Platelet derived growth factor, transforming growth factor B, basic fibroblast growth factor
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What are the roles of fibroblasts in early proliferation phase?
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Proliferate and migrate within wound
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What are the roles of fibroblasts in later proliferation phase?
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Synthesize and reconstruct components to replace provisional wound matrix
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What products do fibroblasts synthesize and secrete in the proliferation phase?
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Collagen, GAGs (HA), glycoproteins, proteoglycans, proteases (MMPs)
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When does collagen production begin in the proliferation phase?
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2-3 days after wounding
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When does collagen production peak in the proliferation phase?
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1-3 weeks after wounding
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What type of collagen is initially most abundant in the proliferation phase?
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III
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When does epithelialization begin in the proliferation phase?
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Immediately after wounding
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How does epithelialization begin in the proliferation phase?
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Resident keratinocytes begin migration and phagocytosis
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What enables keratinocyte migration in the proliferation phase?
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Phenotypic change resulting from loss of contact inhibition, exposure to cellular products (NO)
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What effect do keratinocytes have on fibroblasts in the proliferation phase?
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Stimulate fibroblasts to release GF, cytokines
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How do keratinocytes migrate in the proliferation phase?
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Detach from neighbor cells, develop pseudopods with actin filaments, attach via integrins on pseudopods to ECM, actin filaments pull cell
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What interferes with keratinocyte migration in the proliferation phase?
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Fibrin, inflammatory products, exuberant granulation tissue
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What stops keratinocyte migration?
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Contact with other keratinocytes
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How does new epidermis differ from uninjured skin during the proliferation phase?
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Lacks rete pegs, lacks dermal layer in full thickness wounds
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What is a rete peg?
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Anchor epidermis to underlying connective tissue matrix
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When does contraction begin in the proliferation phase?
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2nd week after wounding (full thickness)
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What is necessary for contraction in the proliferation phase?
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Differentiation of fibroblasts to myofibroblasts
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Contraction rate (loose skin):
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0.75mm/day
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What are the primary mediators of fibroblast differentiation to myofibroblasts in the proliferation phase?
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TGFB released by macros & keratino; fibroblast density, mechanical tension on fibroblasts
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What signifies fibro → myofibroblast differentiation in the proliferation phase?
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Acquisition of alpha smooth muscle actin microfilament system
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When does contraction stop in the proliferation phase?
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Wound edges meet; tension of surrounding skin is equal to or greater than contraction; # of myofibroblasts becomes low
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What begins the maturation phase?
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Wound defect filled; homeostasis between collagen production & degradation; reduction of macrophases & fibroblasts by apoptosis
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How does collagen content change in the maturation phase?
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No net gain in content but haphazard arrangement changes to formation of bundles, cross-linking, and alignment along lines of tension
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How does tensile strength of the wound change during the maturation phase?
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Gradual gain, 20% of normal tissue at 3 weeks, 50% of normal within 3 months, 70-80% of normal at conclusion
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Why do ponies heal faster than horses?
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Quicker & more intense inflammatory response
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What are some reasons for delayed wound healing?
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Wound expansion, motion, exposed bone, infection
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What are the negative effects of soil?
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Reduce WBC effectiveness, decrease humoral defences, neutralize antibodies
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Why do distal limb wounds heal more slowly that trunk wounds?
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Slower epithelialization & contraction because of motion, infection, exuberant granulation tissue
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What are reasons for development of exuberant granulation tissue on distal limb wounds?
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Inefficient inflammatory response, imbalance in collagen homeostasis, profibrotic environment, microvascular occlusion, inappropriate cell apoptosis
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What mediated the profibrotic environment resulting in exuberant granulation tissue?
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Imbalance of TNFa, IL1, IL6, PDGF, TGFB, basic fibroblast GF
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What effect does TGFB have on creating a profibrotic environment?
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Enhances migration and proliferation of fibroblasts, delays fibroblast apoptosis
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What is microvascular occlusion?
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Occlusion of small capillaries within granulation tissue
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What is the effect of microvascular occlusion on the formation of exuberant granulation tissue?
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Results in local hypoxia which stimulates angiogenic and fibroblastic signals
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What general factors affect wound healing?
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Age, nutritional status, type of injury,tissue perfusion, hemostasis & hematoma formation, debridement, wound closure, topical therapy, pharmaceuticals
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What are the negative effects of seroma or hematoma formation?
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Impede healing by mechanical distraction of wound edges, reduce capillary perfusion (pressure on vessels), increases risk of infection
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what are the effects of TAO/ SSD on wound healing?
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Increase epithelialization but decrease wound contraction
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What are the effects of nitrofurazone on wound healing?
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Decreases epithelialization, delays wound contraction, carcinogen
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What is the benefit of ketanserin?
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Blocks serotonin-induced macrophage suppression and vasoconstriction during inflammatory phase (strengthens inflammatory response)
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What is the benefit of aloe vera?
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Stimulates macrophages to release fibrogenic and angiogenic cytokines during inflammatory phase and early proliferation phase (will increase granulation tissue formation over bone)
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What is the active agent in aloe vera?
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Acemannan
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What are the effects of NSAIDs on wound healing?
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Inhibit inflammatory response (decreased fibroblasts proliferation, protein synthesis, wound contraction, inhibition of keratinocyte GF, reduced angiogenesis)
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Function of PMN (neutrophils) in wound healing:
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phagocytosis of microbes, macrophage activation, amplify inflammatory response, stimulate repair processes
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Function of macrophages in wound healing:
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phagocytosis of PMN, damaged tissue and microbes, amplify repair process, stimulate angiogenesis & fibroplasia, fibrolysis
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Function of mast cells in wound repair:
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control vascular permeability, control influx of PMN, regulate tissue remodeling
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PMN mediators:
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ROS, eicosinoids, TNFa, IL1B, IL6, VEGF, IL8
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Macrophage mediators:
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TNFa, IL1B, IL6, PDGF, VEGF, bFGF, TGFa, TGFB, tPA, uPA
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Mast cell mediators:
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histamine, chymase, tryptase
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Source of colony stimulating factor (CSF):
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macrophage, lymphocyte, fibroblast, endothelial cell
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Function of CSF:
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differentiation & maturation of hematopoietic stem cells
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Source of interferon:
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monocytes, macrophage, lymphocyte, mesenchymal cell
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Function of interferon(INF):
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proinflammatory, release other cytokines to inhibit fibrosis
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Source of interleukin (IL):
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all nucleated cells (mostly macrophage & lymphocyte)
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Function of interleukin:
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proinflammatory, enhances epithelialization, angiogenesis, remodeling
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Source of tumor necrosis factor (TNF):
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macrophage, lymphocyte, mast cell
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Function of TNF:
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proinflammatory, enhance angiogenesis, epithelialization, and remodeling
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Source of connective tissue growth factor:
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fibroblast
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Function of connective tissue growth factor:
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mediate TGFb activity (cell proliferation, ECM accumulation)
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Source of epidermal growth factor (EGF):
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platelet, saliva
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Function of epidermal growth factor:
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epithelialization, chemotactic & mitogenic to fibroblast, protein & MMP synthesis
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Source of transforming growth factor a (TGFa):
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macrophage, epithelial cell
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Function of TGFa:
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epithelialization, chemotactic & mitogenic to fibroblast, protein & MMP synthesis, angiogenesis
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Source of fibroblast GF:
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inflammatory cell, fibroblast, endothelial cell
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Function of FGF:
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chemotactic and mitogenic to fibroblast and epithelial cell, protein synthesis, angiogenesis
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Source of insulin-like growth factor (IGF):
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liver, platelet
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Function of IGF:
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chemotactic & mitogenic to epithelial cell, migration of epithelial cell, fibroblast proliferation, protein & GAG synthesis
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Source of keratinocyte GF (KGF):
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fibroblast
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Function of KGF:
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chemotactic & mitogenic to epithelial cell
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Source of PDGF:
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platelet
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Function of PDGF:
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chemotactic to inflammatory cell & fibroblast, mitogenic to mesenchymal cell, protein synthesis
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Source of TGFB:
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platelet, lymphocyte, mast cell, monocyte, macrophage, endothelial cell, epithelial cell, fibroblast
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Function of TGFB:
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chemotactic to inflammatory & mesenchymal cell, fibroblast proliferation, protein synthesis, ECM deposition, inhibition of MMP, induction of TIMP, wound contraction
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Source of VEGF:
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macrophage, fibroblast, endothelial cell, epithelial cell
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Function of VEGF:
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angiogenesis
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