WOUND HEALING & WOUND INFECTION DR. WALID AL - MEKHLAFI 2025 2 Wound is a break in the integrity of the skin or tissues often associated with disruption of structure and function 3 ANATOMY OF SKIN Epidermis : composed of several thin layers: Stratum B asale, Stratum S pinosum, Stratum G ranulosum, Stratum Lucidum and S tratum C orneum the several thin layers of the epidermis contain the following: a) melanocytes , which produce melanin, a pigment that gives skin its color and protects it from the damaging effects of ultraviolet radiation. b) keratinocytes , which produce keratin, a water Repellent protein that gives the epidermis its tough and p rotective quality. 4 5 Dermis : composed of a thick layer of skin that contains collagen and elastic fibers, nerve fibers, blood vessels, sweat and sebaceous glands, and hair follicles. Subcutaneous Tissue: composed of a fatty layer of skin that contains blood vessels, nerves, lymph, and loose connective tissue filled with fat cells 6 7 FUNCTIONS OF SKIN 1. Protection : intact skin prevents invasion of the body by bacteria 2. Thermoregulation : intact skin facilitates heat loss and cools the body when necessary, through the following processes : - • production of perspiration which assists in cooling the body through evaporation • production of vasodilatation and vasoconstriction which assists in heat loss or prevent heat loss from the body 3. Fluid and Electrolyte balance : intact skin prevents the escape of water and electrolytes from the body 4. Vitamin D Synthesis 5. Sensation 8 The major barriers of the skin: 1. Continuous desquamation of the stratum corneum 2. Epithelium as mechanical barrier 3. Lysozyme (in sweat, sebum and tears) 4. Bacteriocins produced by commensals. 9 TYPES OF WOUNDS Open wounds Abrasions Incised wounds Lacerated wounds Penetrating wounds Bites Closed wounds Hematoma Contusions 10 Management of open wounds: ▪ Primary survey ▪ Brief history ▪ Anti - tetanus prophylaxis ▪ Antibiotics prophylaxis ▪ Control active bleeding by ........................ ▪ Good irrigation and debridement ▪ Repair of structures 11 Components of wound healing 1. Wound contraction 2. Granulation tissue formation 3. Epithelialization 12 Wound healing is the body ’ s natural process of restoring normal function and structure after an injury Healing is a complex series of events that begins at the moment of injury and can continue for months to years 13 STAGES of WOUND HEALING Inflammatory phase : • Occurs when the damaged endothelial cells → platelet aggregation → release cytokines that increase expression of integrands in circulating lymphocytes and macrophages • Histamine, serotonin, and kinins cause vessel contraction (thromboxane), decrease in blood loss, and act as chemotactic factors for neutrophils , the most abundant cells in the initial 24 hour period • This phase last for about 5 days • Characterized by (redness ), (swelling), (heat) and (pain) 14 Proliferation phase : • Occurs next, after the neutrophils have removed cellular debris and release further cytokines acting as attracting agents for macrophages • Fibroblasts now migrate into the wound and secrete collagen type III • Angiogenesis occurs by 48 hours due to endothelial cells proliferation • The secretion of collagen, macrophage remodeling and secretion, and angiogenesis continues for up to 3 weeks • The greatest increase in wound strength occurs during this phase 15 Maturation phase : • The final phase and starts from the 3 rd week and continues for up to 9 - 12 months • This is where collagen III is converted to collagen I ( 4 : 1 ) • The tensile strength continues to increase up to 80 % of normal tissue 16 17 18 CLASSIFICATION OF WOUNDS CLOSURE Healing by Primary Intention : All Layers are closed The incision that heals by first intention does so in a minimum amount of time, with no separation of the wound edges, and with minimal scar formation → nice scar Healing by Secondary Intention : Deep layers are closed but superficial layers are left to heal from the inside out Healing by second is appropriate in cases of infection, excessive trauma, tissue loss, or imprecise approximation of tissue → ugly scar Healing by Tertiary Intention : Also referred to as delayed primary closure 19 20