Healing of Skin Wounds

HEALING OF SKIN WOUNDS:-1. Healing by first intention (Primary union):-Characteristic of clean, uninfected surgical incision woundapproximated by surgical sutures.This incision causes only focal disruption of epithelialbasement membrane continuity and death of relativelyfew epithelial and connective tissue cells.As a result, epithelial regeneration is the principle mechanismof repair.A small scar is formed and there is minimal woundcontractionThe narrow incisional space first fills. with fibrin-clottedblood, which then is rapidly invaded by granulation tissueand covered by new epithelium.2. Healing by Second intention (Secondary union) -When cell or tissue loss is more extensive, such as inlarge wounds, at sites of abscess formation, ulceration,and ischemic necrosis (infarction). in parenchymal organs,the repair process is more complex and involves acombination of regeneration and scarring.The inflammatory reaction is more intense, and thereis development of abundant granulation tissue, withaccumulation of ECM and formation of a largescar, followed by wound contraction mediated by theaction of myofibroblasts. 3. Healing by Tertiary Intention(Delayed primary closure):Approximation of wound edges is delayed by a fewdays after injury or surgery.There is greater granulation, greater risk for infection,greater inflammatory reaction and more scars.1° Intention: - Clean wound with limited tissue loss.- Wounds edges easily approximated.- Classic surgical wound closure.- Small Hairline scar is formed.2 Intention :- Large wound with irregular margines and moretissue loss.- Large granulation tissue is formed which fill thegap.- Formation of large scar with prominent woundcontraction.3 Intention :- Large dirty and heavy contaminated wound- Wound is cleaned, debrided, left open for 4-5 daysand then surgical closure.- -Also called as Delayed Primary closure.Factors that affect tissue repair :-Local FactorsSystemic Factors1. Local infection1. Diabetes (Metabolic status)2. Mechanical stress/Local pressure.2. Malnutrition ( Vit. Protein C deficiency deficiency y)3. Foreign bodies3. Immunodeficiency4. Poor perfusion/Inadequate4. Immunosuppressive medicationsblood supply.5. Type and extent of tissue injury.5. Age6. Edema6. Obesity7. Smoking8. Glucocorticoids (steroids) HYPERTROPHIC SCARKELOID SCAR1.Remains confined to the original1. Extends beyond the originalsite of trauma.site of trauma.2. Predilection for shoulders,2. Predilection for sternum,Knees, ankles, neck.earlobes cheeks, arms.3.Develops rapidly following3. May develop months toinjury.years following injury.4.Rapid growth phase followed4. Persistence for years withby a regression.no spontaneous regression.5. Low rate of recurrence5. High rate of recurrencefollowing excision.following excision.6. No association with skin6. Higher association withpigmentation.skin pigmentation.