Healing & Repair PDF

HEALING & REPAIR DR ZAKARIA ELTAHIR OUT LINES ¢ What is wound healing? ¢ Types of healing ¢ Regeneration ¢ Factors contorting regenerations ¢ Mechanisms of regeneration ¢ Repair (fibrosis) ¢ Extracellular matrix ¢ Skin wounds ¢ Factors influencing wound healing ¢ Complications...

HEALING & REPAIR DR ZAKARIA ELTAHIR OUT LINES ¢ What is wound healing? ¢ Types of healing ¢ Regeneration ¢ Factors contorting regenerations ¢ Mechanisms of regeneration ¢ Repair (fibrosis) ¢ Extracellular matrix ¢ Skin wounds ¢ Factors influencing wound healing ¢ Complications of repair ¢ Specialized tissues healing ¢ Bone healing WHAT IS WOUND ¢ Is cut or break of the continuity of any tissue, caused by injury or operation, often is associated by disruption of structure and function ¢ Wounds classified into Ø Tidy wound Ø Untidy wound POLLING QUESTION 1 Why healing is an important mechanism? A. Stop bleeding B. Protect from scaring C. Protect from infection HEALING ¢ The body’s response to injury in an attempt to restore normal integrity and function ¢ Healing has two distinct processes a) Regeneration: healing take place by the regeneration of parenchymal cells b) Repair: is healing outcome in tissues do not return to their normal structure and function and result in formation of scar POLLING QUESTION 2 Healing by repair is better than regeneration! A. Yes B. No REGENERATION ¢ Labile cells: - normal state is active cell division - usually rapid regeneration ¢ Stable cells: - not normally dividing at a significant rate - speed of regeneration variable ¢ Permanent cells: - unable to divide - unable to regenerate FACTORS CONTROLLING REGENERATION Complex and poorly understood?! ¢ ‘Growth factors’ — EGF, FGF, IGF & PDGF*,... etc — Hormones e.g. ACTH, œstrogen, growth hormone... ¢ Contact with basement membranes & adjacent cells — Signalling through “integrins” (specific cell membrane protein) ¢ NOTE: importance of growth control in CANCER *Platelet-derived growth factor (PDGF) MECHANISM CONTROLLING REGENERATION THE EXTRACELLULAR MATRIX ¢ Collagen — Type I - Bone, tendon, scars. Type III - ‘tissue scaffold’. Type IV - non-fibrous, basement membranes... ¢ Elastin ¢ Glycoproteins — Fibronectin, Osteonectin, Tenascin,... ¢ Proteoglycans — Heparan sulphate proteoglycan,... ACUTE DAMAGE TO KIDNEY - REGENERATION Mitotic figures HEALING SKIN WOUND MYOCARDIAL INFRACTION FACTORS INFLUENCING WOUND HEALING ¢ Local factors: — Type, size, location of wound — Apposition, lack of movement — Infection: Suppuration, Gangrene, Tetanus ¢ (Secondary hæmorrhage) — Blood supply: Arterial, Venous — Foreign material: dirt, glass, sutures, necrotic tissue — Radiation damage FACTORS INFLUENCING WOUND HEALING ¢ General Factors: — Age — General state of health — Chronic diseases: e.g. DM, rheumatoid arthritis etc — Drugs (steroids) and hormones — General cardiovascular status — General dietary deficiencies e.g. protein — Specific dietary deficiencies ¢ Vitamin C ¢ sulphur-containing amino acids POLLING QUESTION 3 In healing stable cells usually: A. Don’t divide B. Divide rapidly C. Variable division rate COMPLICATIONS OF REPAIR ¢ Insufficient fibrosis: — Wound dehiscence; hernia; ulceration ¢ Excessive fibrosis: — Cosmetic scarring; hypertrophic scars/keloid ¢ Excessive contraction: — Limitation of joint movement (Contractures); obstruction of tubes & channels (Strictures) EXCESSIVE CONTRACTION: COMPLICATIONS OF REPAIR POLLING QUESTION 4 Does high mitotic figure in a tissue specimen could indicate cancer growth? A. Yes B. No HEALING IN SPECIAL TISSUES ¢ Muscles: All striated muscles cannot regenerate, so healing only by fibrosis ¢ Nerves: 1. Axon only damage repairs by regrowth. 2. Nerve cells are healed by gliosis, as nerve cells cannot regenerate BONE HEALING (FRACTURE HEALING) ¢ Immediate - Blood clot ¢ Hours - inflammation, neutrophils & macrophages ¢ Removal of dead bone by osteoclasts ¢ Days - Granulation tissue with osteoblasts and matrix (soft callus) ¢ Weeks - Deposition of Calcium (calcification) to form hard callus ¢ Months - Remodeling - removal of excess irregular bone (osteoclasts) BONE HEALING (FRACTURE HEALING) POLLING QUESTION 5 How nerve cells healed? A. By gliosis B. By regeneration C. They don’t heal.. God has given us the knowledge and we have seek and implement it!