Lec4 Would Healing and Repair Flashcards Preview

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Flashcards in Lec4 Would Healing and Repair Deck (30):

Regeneration vs Healing

Regeneration: restore lost tissues
- occurs with superficial wounds, some inflammatory process, intact tissue framework
- ex. liver regeneration, superficial skin wound, resorption exudate in pneumonia

Healing: restore original structure but collagen formation and scar formation
- occurs with damaged tissue framework, deep wounds
- ex. deep excisional wound, MI



Tissue scar formation when persistent tissue damage
- ex. chronic inflammatory disease - cirrhosis, chronic pancreatitis, pulmonary fibrosis


Early state of healing

- 0-3 days
- thrombosis
- inflammation [neutrophils + macrophages]
- re-epithelialization [this new epidermis above scar]

in order:
0-4 hrs: fibrin clot forms
1-3 days: phagocytosis
1-4 days: chemoattraction and migration of inflammatory cells to wound



in early wound healing:
- helps fibroblasts bind fibrin to form fibrin clot
- promotes phagocytosis


Migration in wound healing

- occurs days 1-4
- monocytes [macrophages, neutrophils] are recruited and adhere to site of injury
- produce cytokines including: PDGF [platelet derived growth factor] and TGF-B
---- stimulate proliferation + migration + matrix production


What is PDGF?

- Platelet derived growth factor
- mitogenic cytokine
- released by platelets and endothelial cells
- mitogen for formation of fibroblasts, smooth muscle, connective tissue
- part of early wound repair?


What is FGF?

- Fibroblast growth factor
- mitogenic cytokine
- has many types and isoforms
- produced by macrophages and fibroblasts
- stimulates fibroblast proliferation and new vessel growth


4 Markers of Organizing wound??

Organizing = wound undergoing repair
- secondary change in thrombus
- dissolution of clot
- formation new vessels
- deposition of stroma


Mid State of Wound Healing

1-10 days
- early formation new collagen III matrix, dissolution of clot and phagocytosis [2-4 days]
- More collagen III and matrix molec [2-5 days]
- Granulation tissue


Granulation tissue

- part of mid stage of wound healing
- components
--- macrophages, myofibroblasts, fibroblasts, capillaries
- angiongenesis via canalization and connection of capillaries


2 mitogenic cytokines

PDGF - platelet derived growth factor
FGF - fibroblast growth factor


2 Fibrogenic cytokines

TGF-B [transforming growth factor -B]
IL-4 [interleukin-4]


What is TGF-B?

- fibrogenic cytokine
- secreted by lymphocytes, macrophages, platelets
- chemoattractant for inflammatory cells
- inhibits inflammatory response


What is IL-4?

- fibrogenic cytokine
- effects many cell types [B and T]
- modulates inflammatory response [TH2]
- essential in fibrosis along with TGF-B


What is VEGF?

- angiogenic cytokine
- vascular endothelial growth factor
- promotes growth of blood vessels
- binds receptors on endothelial cells


What is EGF?

- epithelial proliferation cytokine
- produced by keratinocytes and macrophages
- promotes epidermal migration and proliferation



- aid in remodeling extracellular matrix activation and inhibition


Late stage of wound healing

3-30 days and more
- formation of definitive collagen I matrix


Content of extracellular matrix

- collagens I, III, IV
- glycosaminoglycans
- elastin
- microfibrils
- fibronectin
- integrins



- expresses antigens of smooth muscle
- responds to agents that contract smooth muscle
- responsible for wound contraction


Wound strength

Elastic fibers are not replaced in scar tissue
- after 1 wk: 10% strength
- after 2 months: 50% strength
- after 3 months: 70-80% strength



- source is stem cells from hair follicle
- must reform protective barrier
- close wounds by migration or purse string
- differentiate again
- role of basement membrane


Mechanisms of re-epithelialization

1. leap-frog method
- keratinocyte B leap frogs over keratinocyte A
2. train method
- keratinocyte A puls keratinocyte B and C


3 Types of proliferative cells

Labile: rapidly dividing
ex. epidermis, GI tract epithelium

Stable/quiescent: slowly dividing unless stimulus
- ex. liver

permanent: incapable of dividing
- ex. neurons, cardiac myocytes


stem cells

- cell capable of self-renewal and production of another cell for differentiated phenotype-assymetric replication
- embryonic + adult


Local factors influence wound healing

- type, size, location of wound
- adequacy blood supply
- presence infection
- exposure to ionizing radiation
- exposure to ultraviolet light


Systemic factors influence wound healing

- circulatory status [age]
- metabolic status
- presence infection, diabetes, neaplasia
- adequate levels Vic C, AA [met]
- hormones: corticoids, ACTH, estrogens, growth hormone


Complications of wound healing

- deficient scar formation: ulceration, dehiscence
- excessive scar formation: keloids, hypertrophic scar
- excessive contraction: contracture or cicatrisation
- excessive regeneration
- painful scar
- pigmentary change


Healing by primary vs secondary intention

primary intention: wounds with apposed edges
-- approximation surgical wounds, minimal wound contraction, good esthetic result

secondary intention: wounds with separated edges
--non-approximation wound edges, massive contraction, poor esthetic resutl


would dehiscence

would ruptures along surgical suture