1.3 WOUND HEALING

Question 1

Name the 3 phases of wound healing

Answer 1

1. Hemostasis
2. Inflammatory
3. Proliferative
4. Remodelling

Question 2

Inflammatory phase starts within …, and can last …

Answer 2

first 6–8 hours

3–4 days

Question 3

Initial step of inflammatory phase?

Answer 3

Clot formation & coagulation

PLTs come first to the site of wound

Question 4

Name some of the factors released by PLTs

Answer 4

• ADP
• clotting factors
• PDGF
• EGF
• fibrinogen
• fibronectin
• TGFα & TGFβ)

some of which are chemotactic for platelets, fibroblasts, and immune cells

interact with fibrin

Question 5

… & … are essential to the process of clotting and coagulation

Answer 5

• Fibrin (first ECM component deposited)
• fibronectin (helps provide a matrix for fibroblasts to rebuild)

Question 6

What step is necessary for appropriate wound healing?

Answer 6

clot removal

(by plasminogen/plasmin and metalloproteinases)

Question 7

Vasodilation in the inflammatory phase is mediated by?

Answer 7

• histamine
• prostaglandins
• complement
• kinins

Question 8

Influx of neutrophils occurs in the first …?

NPs are involved in …?

Answer 8

48 hours

(fibrinogen/fibrin products, C5a, and other cytokines chemoattract neutrophils)

clearance of bacteria and debridement

Question 9

Which type of cells arrive next after NPs & are absolutely necessary for wound healing?

Answer 9

Macrophages

Question 10

What is the function of macrophages?

Answer 10

• Phagocytose/debride tissue/organisms
• set the stage for the proliferative stage

(via secretion of growth factors ➔ ↑fibroblasts and ECM development)

Question 11

Proliferative phase starts around … and may last up to …

Answer 11

day 5–7

1 month

Question 12

Proliferative phase is initiated by …?

Answer 12

growth factors (PDGF, TGF-α/β, FGF, and others) released by macrophages

Question 13

Features of proliferative phase?

Answer 13

1. Reepithelialization
2. Formation of granulation tissue
3. Fibroplasia
4. Neovascularization/angiogenesis

Question 14

Reepithelialization begins within … , is mediated by … which are released by fibroblasts, PLTs, and …

Answer 14

24 hours

EGF, KGF, IGF-1

keratinocytes

Question 15

What is the role of keratinocytes in reepithelialization?

Answer 15

Keratinocytes from sites adjacent to the wound leapfrog over each other (lateral mobilization 2° to breakdown of desmosomes) ➔ reepithelialization

Collagenase produced by monocytes also helps with keratinocyte migration

Question 16

Which molecule is needed for granulation tissue formation?

Answer 16

Fibronectin needed for granulation tissue formation

➔ replaced by collagen III and ultimately collagen I

Question 17

Fibroplasia at 3 to 14 days is characterized by ?

Answer 17

deposition of collagen and other ECM components by fibroblasts

Question 18

Wound contraction is mediated by ?

Answer 18

myofibroblasts

(maximal at 1–2 weeks; these cells contain actin microfilaments)

Question 19

Neovascularization/angiogenesis is mediated by …

Starts in first week of wound healing

Answer 19

VEGF, TGF-β, angiogenin, and other molecules

Question 20

Remodeling starts at … and can take …):

Answer 20

3–4 weeks

1 year

Question 21

Remodeling is characterized by?

Answer 21

• Scar matrix formation (via fibroblast production of collagen/fibronectin/hyaluronic acid)
• regression of granulation tissue (endothelial cells are first to undergo apoptosis and macrophages are last)
• collagen remodeling

Question 22

Scar strength / time

Answer 22

■1 week: up to 5%

■3 weeks: 20%

■3 months: 50%

■1 year: 80%