2.5 Wound healing

Question 1

List tissue types, based on regenerative capacity. Give examples.

Answer 1

1. Labile–contain stem cells, constantly regenerating
   - skin, GI mucosa
2. Stable–Cells are in G0 stage and can regenerate
   - liver
3. Permanent–no regeneration
   - neurons, myocytes, skeletal muscle

Question 2

Tissue repair:
first phase,
its components

Answer 2

Granulation tissue formation

1. fibroblasts–deposit type III collagen
2. capillaries–blood, nutrients
3. myofibroblasts–contract wound

Question 3

Scar formation, mechanism

Answer 3

• type III collagen is replaced with type I collagen.

- removal of type III requires collagenase, requires zinc as cofactor

Question 4

type III collagen

Answer 4

• deposited by fibroblasts in granulation tissue formation

- pliable

Question 5

type I collagen

Answer 5

• “bONE”

- high tensile strength

Question 6

type II collagen

Answer 6

-“car-TWO-lage”

Question 7

Does granulation tissue formation form a scar?

Answer 7

Yes, always

Question 8

Chemical mediators of tissue regeneration/repair (5)

Answer 8

All are growth factors that increase gene expression:

• TGF-A: epithelial and fibroblast growth factor
• TGF-B: fibroblast growth factor, inhibits inflammation
• PDGF: growth factor for endothelium, smooth m, fibroblasts
• FGF (fibroblast GF): important for angiogenesis
• VEGF (vascular endothelial GF): angiogenesis

Question 9

Primary vs Secondary intention

Answer 9

• forms of cutaneous healing
  1. primary: wound edges brought together, no scar
  2. secondary: edges not brought together, granulation tissue fills defect, myofibroblasts contract wound, scar forms

Question 10

myofibroblasts

Answer 10

• important during granulation tissue formation in tissue repair
• contract wound

Question 11

Vitamin/mineral deficiencies in tissue repair

Answer 11

1. Vit C deficiency
   - collagen cross linking
2. Copper deficiency
   - cofactor to cross link lysine and hydroxylysine to form collagen
3. Zinc deficiency
   - cofactor for collagenase (replace type III with type I collagen)

Question 12

collagenase

Answer 12

• replaces type III with type I collagen

- granulation tissue formation during tissue repair

Question 13

Dehiscence

Answer 13

• rupture of a wound

- most commonly seen after abdominal surgery

Question 14

Hypertrophic scar

Answer 14

-raised scar tissue from overproduction of scar tissue

Question 15

Keloid

Answer 15

• excess production of scar tissue, forms large masses

- made of collagen type III

Question 16

TGF-B

Answer 16

1. fibroblast growth factor

2. also reduces inflammation with IL10

Question 17

why do diabetics have poorer wound healing/

Answer 17

• impaired collagen formation, leads to ulcers
• impaired immune function: high sugar level affects neutrophil and macrophage function
• impaired vessel formation