IIT 1

Question 1

How long does it take fibrin to form a scaffold for cell migration?

Answer 1

Minutes

Question 2

How long does it take for necrotic tissue to be removed by phagocytosis and proteases and what molecules do this?

Answer 2

Days. Macrophages and neutrophils

Question 3

How long does it take for macrophages and platelets to secrete chemical mediators that direct tissue repair?

Answer 3

Hours

Question 4

How long does it take for new blood vessels and fibroblasts to invade the wound along the fibrin scaffold?

Answer 4

Begins at 2-3 days

Question 5

How long does it take for fibroblasts to secrete collagen?

Answer 5

Begins at 4-5 days

That is ideal but this may be delayed if things interfere.

Question 6

How long does remodelling and contraction take?

Answer 6

Weeks to months

Question 7

What are the three phases of wound healing?

Answer 7

Inflammatory phase
Proliferative Phase
Remodeling

Question 8

Whats are the steps in the inflammatory phase?

Answer 8

1. Formation of the fibrin scaffold
2. Removal of necrotic tissue
3. Macrophages and platelets secrete chemical mediators that direct tissue repair

Question 9

What happens during formation of the fibrin scaffold?

Answer 9

Fibrin is formed from fibrinogen, which makes a matrix that cells can crawl on.
Fibrinogen leaks from incised blood vessels and inflamed leaky vessels.

Question 10

What does fibrin formation look like histologially?

Answer 10

Eosinophilia as fibrin fills the defect.

Question 11

What happens during the removal of necrotic tissue?

Answer 11

Necrotic tissue must be removed prior to wound repair.

• phagocytosis of debris
• secretion of proteases (macrophages/neutrophils)

Question 12

What is the process by which macrophages and platelets secrete chemical mediators that direct tissue repair?

Answer 12

Macrophages and platelets produce growth factors that allow for new vessel formation (angiogenesis) fibroblast recruitment, synthesis of collagen.

Question 13

What occurs during the proliferative phase?

Answer 13

New blood vessels and fibroblasts invade the wound along the fibrin scaffold. These provide nutrients.
At this point, there still isn’t much strength.

Question 14

What are the steps in the proloferative phase of wound healing?

Answer 14

New blood vessels and fibroblasts invade the wound.

Fibroblasts secrete ECM.

Question 15

What is secreted by fibroblasts in the proloferative phase?

Answer 15

ECM (collagen). This starts at 4-5 days.

Granulation tissue is produced.

Question 16

Is granulation tissue the same as granulomatous inflammation?

Answer 16

No, very different. Granulation tissue involves new blood vessels, fibroblasts produce collagen.
New collagen starts to be produced 4-5 days after injury.
Granulomatous inflammation is chronic inflammation with macrophages surrounded by lymphocytes.

Question 17

What does granulation tissue look like grossly?

Answer 17

Pebbley granular appearance. The new blood vessels give this look.

Question 18

How strong is the wound in the prolifative phase before remodeling?

Answer 18

Not very. There isn’t much collagen, not super strong at 10 days.

Question 19

What are the key occurrences in the remodeling phase?

Answer 19

Maturation of collagen, wound contraction

Question 20

What is involved in the maturation of collagen?

Answer 20

Type 1 gets replaced to type 3, which is stronger.

Collagen bundles also get cross linked.

Question 21

What is the strength of the wound in the remodeling phase at 3 weeks, 6 weeks and 6 months?

Answer 21

20%, 70%, 80%

Question 22

What is formed during wound contraction in the remodling phase?

Answer 22

Myofibroblasts. These cause contraction to shrink the wound.

This takes 4-14 days (but a wound does not regain normal strength by 4 days).

Question 23

What is the difference between fibrin and fibrous tissue?

Answer 23

Fibrin is protein, no cells. It is a sticky matrix for binding/clots.
Fibrous tissue includes fibroblasts, fibrin and blood vessels

Question 24

What are the events in epithelial tissue healing?

Answer 24

-rapid sliding of epithelium
-delayed hyperplasia and migration of epithelium
Connective tissue and basement membrane stay intact, surviving epithelial cells spread on basement membrane to cover defect. They turn from cuboidal flat to squamous in order to cover the defect.

Question 25

What are the 3 requirements for epithelial tissue healing?

Answer 25

• intact connective tissue framework (virus kills epithelial structure)
• adequate vascular supply (for nutrients)
• mitotically active epithelium (eg no drugs that prevent mitosis, need mitosis for reparation - hyperplasia and proloferation)

Question 26

How long does epithelial repair take?

Answer 26

24-48 hours

Question 27

What is the scientific name for a scab?

Answer 27

Eschar

Question 28

How does an incision heal?

Answer 28

Repair CT first, lay down BM, fibrin, necrotic debris. Epithelial cells can’t migrate across fibrin tissue, need bm matrix. Granulation tissue forms.

Question 29

What is healing with first intention?

Answer 29

Wound edges close together, don’t really see wound contraction. Small amount of granulation tissue. Can suture.

Question 30

What is 2nd intention?

Answer 30

Wound edges not opposed, larger amount of granulation tissue. Don’t suture.