8-5 Healing/Repair Flashcards
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A: When Cells are injured they can undergo 3 different things:
1) Adaption
2) Regeneration/Repair
3) DEATH
B: Healing of injured cells starts with inflammation and then ends with Repair. Repair is when damaged/dead tissue is replaced with normal. It may consist of only parenchymal cells or combination of cells and connective tissue
C: Mechanisms of Repair involve cell migration, proliferation and differentiation of cells
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D: REGENERATION= repair process by which damaged/dead cells are replaced by proliferating cells of same type. This can only occur when connective tissue framework is STILL INTACT and serves as scaffolding for parenchymal cell replacement
E: Fibrosis = Repair/Replacement of damaged/dead tissue with [connective fibrous tissue] —> Scar. Fibrosis occurs when there is either:
1) Destruction of [connective tissue framework] ALONG with parenchymal cells (ex. lung abscess)
OR
2) when there are Parenchymal cells that can NOT Regenerate (ex. myocardial necrosis)
F: REGENERATION and Fibrosis often occur simultaneously in repairing a diseased organ because parenchymal cells and connective tissue have both been destroyed (ex. skin laceration)
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A: NORMAL cells can be grouped into 3 categories based on ability to regenerate and respond to growth stimulation:
- Labile Cells = DIVIDE CONTINUOUSLY (ex. skin epithelium / hematopoietic cells)
- Stable Cells= Rapidly divide when stimulated BUT at baseline replicate at low levels and stays in [G0 Cell cycle] for a while (ex. Parenchymal cells of liver and kidney / smooth m. / endothelium
- Permanent Cells = don’t replicate (cardiac / neurons / sk. muscle)
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Repair Process : Replacement by [Connective Fibrous Tissue]
A: Angiogenesis = New blood vessel formation {uses VEGF}
B: Migration & proliferation of fibroblast {uses TGF-b [platelet derived growth factor] / [fibroblast growth factor] }
C: Formation & deposition of extracell matrix by fibroblast
D: Maturation & organization of fibrous tissue elements
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A: [Granulation tissue]= [IMMATURE collagen tissue] tht fills in defects when organs have cells that WON’T generate and/or the organ’s [connective tissue framework] is destroyed during dz.
B:[Granulation tissue] consist of proliferating fibroblast that lies down [IMMATURE connective tissue] elements and new proliferating blood vessels. It appears red and is an attempt to heal destroyed tissue
C: Organization = process of transforming [IMMATURE granulation tissue]—> Dense Scar. During organization, granulation tissue like collagen and blood vessels become less prominent
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A: Steps to Healing Skin Laceration: Wound Repair
- Injury produces skin defect and incites inflammation
- blood clot with fibrin and fibronectin
- Epithelium regenerates & migrates to cover defect
- Cells (fibroblast/MyoFibroblast/macrophages) proliferate & migrate into the defect. Macrophages remove debris (such as dead cells) and secrete cytokines.
- Fibroblast produces [immature xtracell connective tissue] (Granulation tissue) and MyoFibroblast contact the wound
6 Simultaneously, the capillaries in the endothelium are proliferating to extend into the defect under chemical mediation
- Over time (weeks - months) the defect filled with [Granulation tissue] becomes remodeled into a [mature collagen scar] and parenchymal cells.
B: Through this process a wound requires Vitamin C for strength!
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Healing by 1st Intent (1º Union)
Criteria:
- Skin wound is clean and seen by Doctor within a few hours of injury
- Defect is limited in the amount of destroyed tissue
- Doctor decreases defects size by cleansing–>debridement—> suturing gap.
B: Healing by 1st intent allows for healing process to proceed RAPIDLY and w/out complications. Sutures are removed after 5-10 days even though complete healing process could take months.
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Healing by 2nd intent (2º Union)
Criteria:
ºSkin wound is LARGE with Extensive destruction and/or contamination (pt came days after initial injury)
ºWound is cleansed—>debrided—> allowed to “granulate in” WITHOUT closing the gap with sutures.
B: Healing by 2nd intent is the same healing process as 1st but IT WILL TAKE LONGER BECAUSE OF THE SIZE.
C: This is the same healing process that occurs in internal organ healing when there is extensive destruction of tissue
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A: Both Local and Systemic Factors affect the intensity of Inflammation and Repair (healing)
Locally:
-Nature of wound (size vs. configuration)
- Vascular supply (poorly perfused tissue does not heal well)
- Infection (bacteria continue to incite inflammation and prevent healing)
- Foreign bodies (splinter and sutures intensify inflammation and prevent healing when bacteria are present)
- Ionizing Radiation (Radiation DEC perfusion and therefore retards healing)
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A: Both Local and Systemic Factors affect the intensity of Inflammation and Repair (healing)
Systemically:
-Circulation: Poor circulation (like in CHF or severe atherosclerosis) impairs transportation of O2/inflammatory cells/chemical mediators
- Infection: systemic infection may overwhelm the immune system
- Nutrition: vital substances needed for healing - may not be available for healing: {Vitamin C} is needed for [collagen cross-linking] and {copper} is a cofactor for lysol oxidase which cross-links lysine & hydroxylysine to form Stable Collagen! {Zinc} is a cofactor for collagenase
- Hormones: Steroids INHIBIT inflammatory process and impairs healing
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A: [Wound Dehiscence] = Wound rupture
B: Hypertrophic Scar= Excess production of Scar tissue localized to the wound and may regress
C: Keloid = Accumulation of Collagen that grows BEYOND wound boundaries, may be hereditary and more common in Blacks
