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Pathology > Wound Healing > Flashcards

Wound Healing Flashcards

1
Q

What are the stages of wound healing?

A

Epidermis epithelialisation
1. Cell migration stimulated by fibronectin
2. Prolferation - (normally inhibited by chalones)
3. Differentiation

Dermal
Invasion of fibrin clot by solid buds of epithelial cells

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2
Q

What occurs after epidermal and dermal events

A

Macrophages aid clot removal
Fibroblasts produce collagen and glycosaminoglycans

Myofibroblasts aid wound contraction at wound edge

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3
Q

What are the phases of corneal healing

A

Immediate phase
Leucocytic phase
Epithelial phase
Fibroblastic phase
Endothelial phase

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4
Q

What is immediate phase of corneal wound healing

A

Retraction of Descemet’s membrane and stromal collagen causing anterior and posterior gaping

Fibrin plug formation from aqueous fibrinogen

Stromal oedema

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5
Q

What is leukocytic phase of corneal wound healing

A

Polymorphonuclear leukocytes from conj vessels and from aqueous invade wound

In limbal wounds, mononuclear cells from limbar vessels

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6
Q

What is epithelial phase of corneal wound healing

A

Epithelial ingrowth after 1 hour
Full thickness ingrowth is inhibited by healthy endothelium

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7
Q

What is fibroblastic phase of corneal wound healing

A

Fibroblasts from keratocytes produce collagen and mucopolysaccharides which form matrix - avascular
Epithelium slowly retreats anteriorly

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8
Q

What is enodthelial phase of corneal wound healing

A

After 24h endothelial sliding, and mitotic multiplication of endothelial cells to cover posterior aspect of wound

Regeneration of Descemet’s

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9
Q

What is late phase of corneal wound healing

A

Aftetr 1 week cellular infiltrate begins to diminish and collagen fibres arranged more uniformly
stroma and Bowman’s membrane are incapable of regeneration and replaced by scar tissue

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10
Q

How does 5-fluorouracil work?

A

Antiproliferative effect

Competitive inhibition of thymidylate synthetase in S phase cells - impeding DNA synthesis

Incorporation of 5FU derivatives into DNA will also interfere with RNA processing and function

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11
Q

What is the main side effect of 5FU

A

Corneal epithelial toxicity

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12
Q

What does 5FU do in glaucoma surgery

A

Inhibit fibroblasts for 4-6 weeks to prevent healing of bleb

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13
Q

What is mitomycin C

A

Naturally occurring alkylating agent with antbiotic and antineoplastic properatives

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14
Q

What is the effect of MMC

A

Antiproliferative effect

100x more potent than 5FU

Does not inhibit fibroblast migration or attachment but does inhibit proliferation

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15
Q

Why are alkaline injuries worse than acidic injuries

A

Corneal epithelium is not an effective barrier against penetration of alkali - swells and desquamates on contact

Acid causes coagulation necrosis and precipitation of protein which neutralises acid limiting penetration

Alkali coagulates conj blood vessels - widespread limbal ischaemia and destruction of limbal stem cells

RElease of collegenases derived from corneal epithelium and keratocytes - corneal and conj necrosis

Alkali passes easily through cornea into aqueous killin lens epithelium and causing severe non-granulomatous iridocyclitis

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16
Q

What are the phases or corneal angiogenesis?

A

Latent period
Endothelial cell activation
Degradation of endothelial cell basal lamina
Vascular sprouting
Vascular maturation

17
Q

What is the latent period of corneal angiogenesis?

A

Vasodilation
Increase in permeability of neighbouring vessels
Inflammatory cells migrate into the cornea
Stromal oedema separates closely packed collagen lamellae

18
Q

What is the endothelial cell activation period of corneal angiogenesis?

A

Retraction and decreased cell junctions, enlargement of endothelial cell nucleoli

Occurs within 24h

19
Q

What is the degradation of endothelial cell basal lamina period of corneal angiogenesis?

A

Migrating and dividing endothelial cells must penetrate their basal lamina
Aided by proteases derived from endothelium, PMNs, macrophages and mast cells

20
Q

What is the vascular sprouting period of corneal angiogenesis?

A

Endothelial cell migration and replication resulting in sprouts from post capillary venules and pre-exisitng capillaries
Lumen formation and anastamosis of blind channels to form new capillary networks

21
Q

What is the vascular maturation period of corneal angiogenesis?

A

Endothelium formed lacks basal lamina
Deposition of extracellular matrix and laminin followed by basal lamin formation and pericyte layer

22
Q

What layer of the cornea cannot regnerate?

A

Bowman’s

Pathology (15 decks)

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