Repair 2: Scar Formation

Question 1

Enumerate steps of Granulation tissue

Answer 1

1. Removal of dead tissue by Macrophages
2. Angiogenesis
3. Fibrogenesis (activation of fibroblast & ECM
4. Scar remodeling

Question 2

factors influencing Angiogenesis in scar formation

Answer 2

• VEGF (vascular endothelium growth factor)
• FGF (fibroblast growth factor)

Question 3

Describe angiogenesis in scar formation

Answer 3

1. New capillaries Pud from old vessels by vascular endothelial growth factor & Fibroblast growth factor (VEGF & FGF)
2. proteolysis of parent vessel by metaloproteinase
3. remodelling into capillary tubes
4. proliferation of periendothelial cell(pericytes & vascular smooth muscles) to form mature vessels

Question 4

Factors influencing Fibrogenesis in scar formation

Answer 4

• Platelet Derived growth Factor (PDGF)
• Fibroblast growth Factor 2 (FGF2)
• Tissue growth Factor Beta (TGFbeta)

Question 5

cells releasing fibrogenic factors

Answer 5

Macrophages

Question 6

role of Fibroblasts in scar fibrogenesis

Answer 6

• It deposits ECM proteins (fibronectin & proteoglycans, laminins)
• Synthesis of Type III collagen

Question 7

Mechanism of scar remodelling

Answer 7

1. Decrease fibroblast & capillaries
2. Deposition of Collagen type I for tensile strength
3. Scar decreases in size by myofibroblast contraction + collagenase activity by Macrophages

Question 8

Description of Scar after remodeling

Answer 8

Pale avascular strong fibrous

Question 9

Charactaristics of mature scar

Answer 9

• collagen type I
• Inactive fibroblasts
• few to no capillaries

Question 10

describe repair by Primary intention within 24 hours

Answer 10

• there is an immediate clot
• after 24 hour, neutrophils migrate to digest the clot

Question 11

repair by Primary intention within 24-48 hours

Answer 11

• Basal cells of epithelium proliferate/regenrate to bridge towards gap & meet in the midline of the incision

Question 12

repair by Primary intention by day 3

Answer 12

• Macrophages digest fibrin & cellular debris
• some granulation tissue invades edges to heal the dermis

Question 13

repair by Primary intention by day 7

Answer 13

• Fibroblasts lay down collagen fibers to bridge the incision
• formation of mature epidermal architecture with surface keratinization

Question 14

scar reaches 10 % tensile strength of skin at ____

Answer 14

7th day

Question 15

scar reaches 70-80 % of tensile strength of skin at ____

Answer 15

3rd month

Question 16

Which special sensory neurones do not regenerate

Answer 16

Pacinian Corpusle