23 Phases of Wound Healing 1. Inflammation- day 1-102. Proliferation-5 days-3 weeks3. Remodeling-3 weeks-1 year
3Inflammation Phase: Injury Bleeding and vasoconstriction(5-10min), followed by vasodilationPlt plug formation and clottingFibrin binds the plt plug and forms the provisional matrix (platelets+fibrin+fibronectin)Platelet degranulation (alpha and dense granules)-> PDGF and TGF-BChemotaxis for inflammation
4Inflammation PMNs-almost immediately, clear debris Macrophages-Day 2-3 (essential)Fibroblast proliferation, endothelial cell proliferation (angiogenesis), and extracellular matrix production, and they recruit and activate additional macrophages.Lymphocytes
5Proliferation Phase (5-21 days) Fibroblasts-enter provisional matrix and initiate collagen synthesisProminent cell type during this phaseMacrophages->angiogenesis and neovascularizationCollagen and proteoglycans or ground substance replaces the provisional fibronectin–fibrin matrix
6Remodeling Phase (3wks-1 year) Max collagen accumulation at 2-3 weeks. Only remodeling/crosslinking after 3 weeks.Type III collagen predominates early (days 1-3), but is replaced by type I6 weeks-80% of final strength and 60% of original strength8 weeks-max tensile strength (70-80%)
7CollagenNeed alpha-ketoglutarate, vit C, O2, and iron for hydroxylation of proline, and crosslinking of proline residuesProline is every 3rd amino acid. Lysine is abundant from hydroxylysine crosslinkingType I, most common and most abundant in healed woundD-penicillamine inhibits collagen crosslinking
8Surgical Wound Healing Primary Intention-Tensile strength is important in healing closed incisionsDepends on collagen deposition and cross-linkingSecondary Intention-Epithelial integrity is important in healing open woundsDependent on granulation tissue (capillaries, fibroblasts and collagen)Migration from wound edges, sweat glands and hair follicles
9Essential for wound healing Moist environment- optimizes epithelial migrationOxygen delivery- EssentialAvoid edema- edema causes decreased O2 in woundsRemove necrotic tissue- leads to infection
12Scars Contain proteoglycans, hyaluronic acid, and water. Keloids- AD, dark skinned. Collagen goes beyond original scarHypertrophic scar- Collagen stays within scarTreatment: Steroids, silicone, pressure garments, XRT.Infants heal with little/no scarring-multifactorial, decreased inflammatory response, increase hyaluronic acid?
13Chronic WoundsPressure Sores- pressure over bony area, occurs when tissue pressure exceeds the capillary filling pressure of 25 mm HgTx: Pressure off loading, debridement, myocutaneous flapLeg ulcers- 90% due to venous insuff.Tx: Unna boot, elastic wrapDiabetic foot ulcers- 2nd MTP joint (Charcot’s joint). Neuropathy leads to increased pressure-> IschemiaTx: Depends on extent of ulcer
14QuestionThe most prominent cell type in the 1st 24 hours of a wound is :PMN’sMacrophagesLymphocytesFibroblasts
15AnswerPMN’sMost abundant in 1st 24 hrs, help clear debri
16Question The most prominent cell type day 2-4? PMN’s Macrophages LymphocytesPlatelets
17AnswerMacrophagesFibroblast proliferation, endothelial cell proliferation (angiogenesis), and extracellular matrix production, and they recruit and activate additional macrophages.
18Question What is the most prominent cell type at 1 week? PMN’s MacrophagesLymphocytesFibroblasts
19AnswerFibroblasts-Enter provisional matrix and initiate collagen synthesis. Days 5-21.
20Question The most predominant type of collagen in the body? I II III IV
21AnswerType I most common, seen in skin, bone, tendons, and healed woundsIII CartilageIIIIV Basement membrane
22Question Most abundant collagen in healing wound during 1st 24hrs? I IIIIIIV
23AnswerType III- Most abundant the first 48hrs, and is then replaced by type I.
24Question What is the most important cell involved in wound healing? PMN’sMacrophagesLymphocytesFibroblasts
25AnswerMacrophagesEssential, synthesizes cytokines and growth factors necessary for wound healing.
26Question Maximal tensile strength of a wound occurs at: 3 weeks 3 months
32QuestionThe most important factor in the healing wounds by secondary intention is:Tensile strengthEpithelial integrityPlatelet activating factorcocaine
33AnswerEpithelial integrity- epithelial cells migrate from hair follicles, wound edges and sweat glands.
34QuestionThe most important factor in the healing wound by primary intention is:Double cheeseburger from McDonaldsTensile strengthEpithelial integrityPlatelet activating factor
35Answer Tensile strength, not double cheeseburger This is created by collagen cross linking
36QuestionThe dressing change regimen that will produce maximal debridement is:Wet-to-dry dressing changes with saline.Dressing changes with Xeroflo.Dressing changes with silver sulfadiazine.Dressing changes with an occlusive dressing.
37AnswerMaximal debridement is accomplished when the dressing is changed utilizing wet-to-dry dressings. Enzymatic agents, such as collagenase, may augment the debriding effect of wet to dry dressing changes.
38Question Hypoxia in a wound stimulates: collagen synthesis contraction ovulationangiogenesisepithelialization