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The Nature of Disease Pathology for the Health Professions Thomas H. McConnell. Chapter 2 Cellular Pathology: Injury, Inflammation, and Repair Repair. Chapter 2: Cell Injury, Disease, and Death. Repair (wound healing)
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The Nature of DiseasePathology for the Health Professions Thomas H. McConnell Chapter 2 Cellular Pathology: Injury, Inflammation, and Repair Repair
Chapter 2: Cell Injury, Disease, and Death • Repair (wound healing) • The second step (after inflammation) of restoring tissue homeostasis after injury • Wound: injury resulting from a short-term injury at a discrete site • Repair consists of two processes • Regeneration – normal tissue, with normal function, restored • Healing – mix of regeneration + scarring, or scarring alone (fibrosis, fibrous repair) • Stage 1: Cell migration and proliferation (provide raw materials) • Stage 2: Angiogenesis (growth of new blood vessels) • Stage 3: Scar development • Cell types in involved in repair are many • Healing by first intention – narrow, closely approximated • Healing by second intention – broad, widely separated edges • Factors affecting wound healing • Pathologic wound healing, e.g., keloid, pyogenic granuloma
Tissue Repair - Overview Wound – Acute (short-term) injury at discrete site *Animation What is parenchyma? What is stroma? Figures from: McConnell, The Nature of Disease, 2nd ed., Wolters Kluwer, 2014 (Fibrosis)
Fibrous Repair Generates Scar Tissue • Three step sequence in fibrous repair • Cell migration and proliferation • Myofibroblasts proliferate begin producing collgen • Fills space not occupied by parenchymal cells • Angiogenesis • Growth of new blood vessels • Scar development • Myofibroblasts generate CT matrix • Pull edges of wound closed • Dense, tight, bloodless • Scar is remodeled by mechanical forces Forms granulation tissue Figure from: McConnell, The Nature of Disease, 2nd ed., Wolters Kluwer, 2014
Granulation Tissue and Scarring Figures from: McConnell, The Nature of Disease, 2nd ed., Wolters Kluwer, 2014 Figure from: https://en.wikipedia.org/wiki/Granulation_tissue Granulation tissue
Impaired Wound Healing • Some factors interfering with would healing include infection, poor nutrition, steroids, poor blood supply, foreign bodies and mechanical factors • Dehiscence – rupture of a wound • Two main types of pathological wound healing • Keloid; prominent, hyperplastic scar • Pyogenic granuloma; highly vascular, persistent granulation tissue Figure from: McConnell, The Nature of Disease, 2nd ed., Wolters Kluwer, 2014 Figure from: http://www.medicinenet.com/image-collection/pyogenic_granuloma_chin_picture/picture.htm