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Causes of tissue damage and wound repair
The document discusses wound healing, outlining the three main stages of the process - inflammatory, proliferative, and remodeling - and describing factors that can impair healing such as infection, foreign materials, tension, and poor blood supply. It also covers causes of tissue damage, the role of different cell types in healing, and methods of wound closure including primary intention, secondary intention, and healing by third intention.
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Causes of tissue damage and wound repair
- 2. WOUND A break inthe continuity of the tissues
- 3. Physical Compromisaedblood flow Crushing Desiccation Incision Irraiation Overcooling Overheating CAUSES OF TISSUE DAMAGE Chemical Agents wd inphysiologic pH Agents wd unphysiologic tonicity Proteases Vasoconstrictors Thrombogenic agents
- 4. WOUND REPAIR EPITHELIALIZATION Injuredepithelium 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)
- 5. e.g detrimental effectof 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
- 6. STAGES OF WOUND HEALING TREEBASIC STAGES: INFLAMMATORY STAGE (reactive phase) PROLIFREATIVE STAGE (regenarative or reparative) fibroplastic phase REMODELLING STAGE (maturational phase)
- 7. INFLAMMATOY STAGE o Tissueinjury…lasts for 3-5 days o TWO PHASES: i. Vascular phase ii. Cellular phase
- 8. VASCULAR PHASE initial vasoconstrictionof disrupted vessels…..blood coagulation Histamine , prostaglandins elaborate by WBCs …vasodilation…which allows plasma to leak and leukocytes to migrate into interstitial tissues
- 9. Fibrin fromplasma causes lymphatic obstruction ..accumulate in the area of injury ….EDEMA
- 10. Signs of inflammationare Redness Swelling Warmth and pain Functio laesa (fig)
- 11. CELLULAR PHASE Triggeredby 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
- 12. Wd timelymphocytes 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
- 13. LAG phase During ds phase no significant gain in wound strength occurs ..little collegen deposition Fibrin … material holding wound…..little tensile strength
- 14. PROLIFATIVE STAGE The combinedprocess of epithelialization , firoplasia and angiogenesis accur in ordr to replace dead and missing tissue Lasts for 2 days to 3 weeks
- 15. FIBROPLASTIC PHASE Strandsof 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
- 16. Fibroblasts deposit tropocollagen…. Collagenproduced 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.
- 17. If Wound isplaced 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
- 18. REMODELLING STAGE Finalstage….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…
- 19. 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
- 20. WOUND CONTRACTION o Finalprocess…. 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
- 22. FACTORS THAT IMPAIR WOUNDHEALING Foreign mateial 3 basic problems i. Bacteria….. ii. Nonbacterial foreign material… iii. Foeign material is often antigenic… That decreases fibroplasia Infection
- 23. Necrotic tissue causes2 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)
- 24. Ischemia Dec bloodsupply >>> 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
- 25. Tension If suturesare 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
- 26. Edges ofwound 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
- 27. Wound repairlessen 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
- 28. 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
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- 31. OK NOW UR QUIZ R U READY FOR THIS? ?????
- 32. Causes oftissue damage Enumerate Stages of healing wd time Factors that impair wound healing