Chapter 9: Wound Healing

Question 1

Name the phases of wound healing? When do they occur?

Answer 1

1)Inflammatory (early 24-48hr, late 48-72hr)

2)Proliferative (day 4-12)
- Angiogenesis (4-6 days)
- Fibroplasia -> collagen (3-5 days)
- Contraction (soon after the granulation bed is established (dog day 4.5, cat day 6.3)
- Epithelization (on the edge of wounds it begins within hours)

3)Maturation (months)

Question 2

Wound hypoxia impairs resistance to infection – oxygen partial pressure below ___mmHg is associated with an inability of neutrophils to kill bacteria?

Answer 2

40mmHg

Question 3

By 48-96 hours what is the primary leukocyte?

Answer 3

Macrophage - they microdebride the wound, phagocytose degenerate neutrophils and induce neutrophil apoptosis

Question 4

Lymphocytes are attracted to the wound by which cytokine? when?

Answer 4

IL-1 at day 3-5

Question 5

Capillary endothelial response to VEGF is dependent on what?

Answer 5

oxygen dependent
arterial partial pressure of oxygen (PaO2)

Question 6

Fibroblasts transform into myofibroblasts in response to what cytokine?

Answer 6

TGF-B1

Question 7

Initial collagen formation in a wound is mostly what type?
By the maturation phase it is mostly what type?

Answer 7

Type 3
Type 1

Question 8

final strength of the scar is what % of unwounded tissue?

Answer 8

70-80%

Question 9

the submucosa of the GIT is predominately what type of collagen?

Answer 9

Type 1 (68%)

Question 10

Fibroblasts in the GIT differ from that of the skin in that they?

Answer 10

Also produce elastin (skin fibroblasts only produce collagen)

Question 11

Anastomosis strength in the first few days of healing decreases by what percent in each tissue?
Esophagus
Gastroduodenal
SI
Colon

Answer 11

esophagus 37%
gastroduodenal 64%
small intestine 70%
colon 72%

Question 12

Sepsis causes an upsurge in what activity causing an increased risk of dehiscence?

Answer 12

Collagenase activity

Question 13

Name 4 factors which differ between healing of skin and GIT?

Answer 13

collagenase activity (skin not significant, GIT increased days 0-3, causes decreased anastomotic strength)
production of collagen (fibroblasts in skin, GIT smooth muscle cells and fibroblasts)
wound shear stress (skin variable, GIT increased due to peristalsis and intestinal motility)
vascular perfusion (relatively constant in skin / GIT can be significantly downregulated by shock)
collagen types (skin 1,3 / git 1,3,5)
bacterial flora (skin aerobia, not widely polymicrobial / GIT aerobic and anaerobic and polymicrobial)

Question 14

Mature collagen formation fails when PaO2 is below what mmHg?

Answer 14

40mmHg

Question 15

Bladder re-epithelization occurs in how many days?

Answer 15

2-4 days

Question 16

Bladder regains 100% of its unwounded strength within how many days?

Answer 16

21 days

collagen synthesis not normal until day 70 postinjury

Question 17

Breaking strength of cutaneous wounds at 7 days significantly less in cats or dogs?

Answer 17

in Cats

Question 18

Granulation tissue is seen earlier in which species?

Answer 18

Granulation tissue is seen earlier in dogs

Dogs: 4.5 days
Cats: 6.3 days

Question 19

Contraction and epithelization is faster in which species? What % at 14 days?

Answer 19

Dogs are faster than cats
Dogs:
44% at 14 days

Cats :
13% at 14 days

Question 20

At 14 days what % of canine wounds are epithelialized compared to just 13% of cats?

Answer 20

44%

Question 21

Which breed is prone to fibroproliferative scarring?

Answer 21

Mexican hairless dog

Question 22

Animals with an endocrinopathy are how many times more likely to develop a postop infection?

Answer 22

8.2 x

Question 23

How do glucocorticoids affect wound healing?

Answer 23

Impair
- macrophage activity
- fibroblast proliferation
- collagen synthesis
Inhibit synthesis of MMP

Question 24

The trunk and neck heal mostly by what way?

Answer 24

contraction

Question 25

What types of collagen are in the skin? In the GIT?

Answer 25

1,3 in the Skin 1,3,5 collagen in GIT

Question 26

Everything in the GIT except esophagus and distal 1/3 of rectum has how many layers? What are they?

Answer 26

4 layers: mucosa, submucosa, muscularis propria, serosa

Question 27

What percent of each type (1,3,5) of collagen are present in the submucosa of the GIT?

Answer 27

Type 1: 68% Type 3: 20% Type 5: 12%

Question 28

Unwounded skin contains what % of type 1 and Type 3 collagen?

Answer 28

Type 1: 80% Type 3: 20%

Question 29

What cells secrete MMPs to break down extracellular matrix and allow cell migration during the epithelialization phase of healing?

Answer 29

Keratinocytes

Question 30

How does wound contraction occur?

Answer 30

In the granulation bed, anchored fibroblasts become myofibroblasts due to TGF-B1 These cells have increased alpha smooth muscle actin and stress fibers They orient linearly along the line of tension and start pulling

Question 31

How does angiogenesis occur?

Answer 31

Growth factors released in inflammatory phase act on capillaries to increase endothelial cell proliferation -> the cells make tubules -> these are new capillaries

Question 32

Collagen production in wounds is rapid for the first how many weeks?

Answer 32

6 weeks - goes down without orientation, then next 12-18 months it aligns/matures

Question 33

Most bone fractures heal through what two types of ossification?

Answer 33

Combo of intramembranous and endochondral

Question 34

The strength of an anastomosis decreases significantly within what timeframe?

Answer 34

First 48hr due to collagenases

Question 35

Platelets bind to vWF on collagen exposed in wounded tissue. They then release what?

Answer 35

Thromboxane A2

Question 36

When does complete granulation tissue formation occur in dogs and cats? Which species is faster?

Answer 36

Complete granulation tissue is faster in dogs than cats: Dogs - 7.5 days Cats- 19 days