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Causes of tissue damage and wound repair
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  • 1. WOUND A break in the continuity of the tissues
  • 2.  Physical  Compromisaed blood flow  Crushing  Desiccation  Incision  Irraiation  Overcooling  Overheating CAUSES OF TISSUE DAMAGE  Chemical  Agents wd inphysiologic pH  Agents wd unphysiologic tonicity  Proteases  Vasoconstrictors  Thrombogenic agents
  • 3. WOUND REPAIR EPITHELIALIZATION  Injured epithelium has genetically programmed regenerative ability that allows it to establish its integrity  Free edges of epith cont. to migrate until it comes into contact with another free edge of epith  Abrasions (surface epith)
  • 4. e.g  detrimental effect of process of c.inhibition controlling epithelialization occurs when o Opening is accidently made into maxillary sinus during tooth xtraction. o If epith of sinus wall and oral mucosa is injured ..it begins to proliferate in both areas….. creating OROANTRAL FISTULA
  • 5. STAGES OF WOUND HEALING TREE BASIC STAGES:  INFLAMMATORY STAGE (reactive phase)  PROLIFREATIVE STAGE (regenarative or reparative) fibroplastic phase  REMODELLING STAGE (maturational phase)
  • 6. INFLAMMATOY STAGE o Tissue injury…lasts for 3-5 days o TWO PHASES: i. Vascular phase ii. Cellular phase
  • 7. VASCULAR PHASE initial vasoconstriction of disrupted vessels…..blood coagulation Histamine , prostaglandins elaborate by WBCs …vasodilation…which allows plasma to leak and leukocytes to migrate into interstitial tissues
  • 8.  Fibrin from plasma causes lymphatic obstruction ..accumulate in the area of injury ….EDEMA
  • 9. Signs of inflammation are Redness Swelling Warmth and pain Functio laesa (fig)
  • 10. CELLULAR PHASE  Triggered by complement products .... act as chemotactic factors and cause neutrophils… o Margination …. o Diapedesis o Contact wd foreign material …. Degranulation o Lysosomal enzymes …destroy foreign materials ..digest necrotic tissue also aided by monocytes..macrophages
  • 11.  Wd time lymphocytes accumulate at site of tissue injury  B lymphocytes o able to recognise antigenic material produce antibodies that assist in identifying foreign materials and interact wd complements to lyse foreign cells  T lymphocytes o Helper T cells o Suppressor T cells o Cytotoxic T cells
  • 12.  LAG phase  During ds phase no significant gain in wound strength occurs ..little collegen deposition  Fibrin … material holding wound…..little tensile strength
  • 13. PROLIFATIVE STAGE The combined process of epithelialization , firoplasia and angiogenesis accur in ordr to replace dead and missing tissue Lasts for 2 days to 3 weeks
  • 14. FIBROPLASTIC PHASE  Strands of fibrin… form latticework…fibroblast can begin laying down ground substance and tropocollagen  Ground substance (mucopolysaccharides )…. Cement collagen fibers  Fibroblasts secrete fibronectin…helps  Stabilize fibrin  Assist in recognizing foreign material  Act as chemotactic factor for fibroblasts  Helps to guide macrophages along fibrin strands for phagocytosis of fibrin
  • 15. Fibroblasts deposit tropocollagen…. Collagen produced in xcessive amounts nd laid down in haphazard manner …. Effectiveness of collagen to produce wound strength….rapidly inc during fibroplastic stage , which normally lasts for 2-3 weeks.
  • 16. If Wound is placed under tension o at the beginning of fibroplasia o Near the end of fibroplasia o At the end of fibroplastic stage……stiff…..erythematous…able to wdstand 70-80% tension
  • 17. REMODELLING STAGE  Final stage….many of previous randomly laid collagen fibers are destroyed as they are replaced by new collagen fibers, which are oriented to better resist tensile forces of wound  Slowly wound strength ..80-85%  Allows the Scar to soften…  Loss of edema…
  • 18.  Wd time … vascularity …diminishes wound erythema….Elastin is not replaced in injured tissue…. loss of flexibility along scarred area(fig5)  Take 3 weeks to 2 years to complete
  • 19. WOUND CONTRACTION o Final process…. o edges of wound migrate toward eachothr o In which edges are not placed in apposition , wound contracrion diminishes size of wound  Problems  third-degree …develop deforming nd debilitating contractures, if wounds are not replaced wd skin grafts  Can b lessened by placement of a layer of epith between d free edges of wound
  • 20. FACTORS THAT IMPAIR WOUND HEALING  Foreign mateial 3 basic problems i. Bacteria….. ii. Nonbacterial foreign material… iii. Foeign material is often antigenic… That decreases fibroplasia  Infection
  • 21.  Necrotic tissue causes 2 problems i. serve as a barrier to ingrowth of reparative cells…. ii. Serves as a protected niche for bacteria…. Include blood…..haematoma…….  Drugs  Nutritional problems  Low temp Distal aspect of xtremities (reduction of 1-1.5 C 2-3F)
  • 22. Ischemia  Dec blood supply >>> tissue necrosis >>> lessen the delivery to wound of antibodies, WBCs >>> inc the chances of wound infection  dec delivery of O2 ….nutrients….  Caused by  Tight or incorrectly located sutures, improperly designed flaps, excessive external or internal pressure on wound, systemic hypotension, peripheral vascular disease and anaemia
  • 23. Tension  If sutures are used to pull tissues together forcefully, >>> ischemia of tissues  If sutures are removed too early >>> reopen >>> heal with scar…w-contraction  If sutures are left in too long in attempt to overcome wound tension…spread open during remodelling stage…and tract into epith through which sutures ran will epithelialize and leave permanent disfiguring marks
  • 24.  Edges of wound in which no tissue loss are placed  Wound in which edges are closely reapproximated  Healing occur more rapidly wd low risk of infection  wound repair wd minimum scar tissue  Tissue loss has occurred so A gap is left between edges of incision or laceration  Tissue loss prevents approximation of wound edges  Healing is slower  Produces more scar formation HEALING Primary Intention 2ndy Intention
  • 25.  Wound repair lessen amount of re-epithelialization , collagen deposition, contraction and remodelling  Primary closure should b performed in 6-8 hr of trauma but vascular areas may b closed upto 24 hrs  e.g Well repaired lacerations or incisions, well-reduced bone fracture  A large amount of epithelial migration, collagen deposition, contraction and remodelling  Wound is left open and heals by formation of granulation tissue and contraction  e.g Extraction sockets, poorly reduced fractures, deep ulcers, large avulsive injuries of any soft tissue Primay Intention 2ndy Intention
  • 26. HEALING BY THIRD INTENTION  Delayed closure of wound after a vaiable period of time for which it been left open  Healing of wounds through the use of tissue grafts to cover large wounds and bridge the gap between wound edges
  • 27. THANK YOU
  • 28. ANY QUESTION ? 
  • 29. OK NOW UR QUIZ  R U READY FOR THIS? ?????
  • 30.  Causes of tissue damage  Enumerate Stages of healing wd time  Factors that impair wound healing