Tissue Repair and Healing Lecture Notes PDF

Lecture : Tissue repair and healing  Repair : Replacement of dead tissue by healthy tissue. It includes two processes Regeneration: replacement of dead tissue by normal tissue of the same cell type. (fibrosis or gliosis): Replacement by connective tissue characterized by the...

Lecture : Tissue repair and healing  Repair : Replacement of dead tissue by healthy tissue. It includes two processes Regeneration: replacement of dead tissue by normal tissue of the same cell type. (fibrosis or gliosis): Replacement by connective tissue characterized by the formation of granulation tissue and its subsequent maturation.  Factors Known to affect healing General Factors Local Factors Age Infections Nutrition  protein lack Ischemia (poor blood supply)  vitamin C, vitamin D deficiency Injury type , duration or  Zinc deficiency severity. Diseases  D.M.  Cushing disease Drugs  Corticosteroid treatment  Cytotoxic drugs  Factors controlling repair Contact inhibition: (inhibition of proliferation and migration) Loss of contact stimulate proliferation and migration Cell matrix: laminin, fibronectin and collagen (binding, proliferation and migration) Intact dermis contains collagen Type I :Type III (80%:20%) 75% of the skin's total dry weight is composed of collagen Growth factors: EGF, FGF, VEGF, PDGF, TGF-alpha, TGF-beta ( TGF-B) could has inhibitory effect Growth Factors:  These are chemical mediators that affect cell growth by binding to specific receptors on the surface or intra-cellular causing 1- stimulate cellular proliferation. 2- stimulate cell migration & differentiation. 3- stimulate tissue remolding. ( TGF-B) could has inhibitory effect Repair capacity depends on cell type Labile cells: : high capacity of regeneration: squamous, columnar, transitional epithelia; hematopoitic and lymphoid tissues Stable cells: limited capacity of regeneration: parenchymal cells of all glandular organs ( e.g. liver, kidneys, ovaries) & mesenchymal cells (bone, cartilages and fibrous tissues) Permanent cells: absent capacity of regeneration : neurons, cardiac muscle cells 4 phases of tissue repair according to Bailey’s 1. Coagulation 2. Inflammatory 3. Fibroplasia 4. Remodelling Wound Healing 3 Phases of Wound Healing 1. Inflammation- day 1-5:10 2. Proliferation-5 days-3 weeks 3. Remodeling-3 weeks-1 year  Chronic Wounds Pressure Sores- pressure over bony area, occurs when tissue pressure exceeds the capillary filling pressure of 25 mm Hg Leg ulcers- 90% due to venous insufficiency. Diabetic foot. Neuropathy leads to increased pressure-> Ischemia Scar tissue  Keloid Scar Keloids are composed of thick scar tissue and are the result of an over-production of collagen in the scar during healing.