6. Healing and Repair

Question 1

What is healing?

Answer 1

Replacement of a destroyed tissue with a viable tissue

Question 2

What is resolution?

Answer 2

Tissue returns to its pre-injury state

Question 3

What situation does resolution happen in?

Answer 3

No tissue destruction

Damaging agent and cell debris are removed

Question 4

What is regeneration?

Answer 4

Replacement of the lost tissue by a tissue of the same type

Question 5

What is repair?

Answer 5

Replacement of the destroyed tissue by a fibrous scar

Question 6

What factors affect the healing process?

Answer 6

Remove causative agent, inflammatory debris
Amount of damage
Ability of cell to proliferate
Extent of ECM damage

Question 7

Where are labile cells found?

Answer 7

Epidermis
GIT
Mucosal epithelium

Question 8

How do labile cells heal?

Answer 8

Regeneration (if stroma is intact)

Question 9

What stage of the cell cycle are stable cells in?

Answer 9

G0

Question 10

Where are stable cells found?

Answer 10

Liver
Kidney
Pancreas

Question 11

How do stable cells heal?

Answer 11

Regeneration if stroma and stem cells are intact

Question 12

Where are permanent cells found?

Answer 12

Neurons, heart, skeletal muscle

Question 13

How do permanent cells heal?

Answer 13

Fibrosis

Question 14

What is the most important mediator affecting cell growth?

Answer 14

Polypeptide growth factors

Question 15

What is the stroma made up of?

Answer 15

ECM
Mesenchymal cells (multipotent stem cells)
Vessels

Question 16

What does the ECM consist of?

Answer 16

Fibrous structural proteins
Glycoproteins for adhesion
Proteoglycans

Question 17

When does fibrosis happen?

Answer 17

Destruction to cells and stroma
Death of permanent cells
Inflammation

Question 18

What is produced when tissue is repaired by fibrosis?

Answer 18

Granulation tissue

Question 19

What is granulation tissue?

Answer 19

Fibroblasts and blood vessels

Question 20

What are the 3 phases of wound healing?

Answer 20

Inflammatory phase
Proliferative phase
Remodelling phase

Question 21

What happens in the inflammatory phase?

Answer 21

Haematoma formation
Infiltration by neutrophils
Neutrophils replaced by macrophages

Question 22

What happens in the proliferative phase?

Answer 22

Epithelial cell proliferation

Granulation tissue formation

Question 23

What is the remodelling phase?

Answer 23

Granulation tissue converted to fibrous tissue to provide strength

Question 24

What enzyme breaks down excessive scarring?

Answer 24

Metalloproteinase

Question 25

What case does healing by primary intention happen in?

Answer 25

Minimum loss of tissue

Question 26

What happens in the first day of healing by primary intention?

Answer 26

Haematoma formation
Acute inflammation
Proliferation of epithelial cells

Question 27

What happens in the second day of healing by primary intention?

Answer 27

Neutrophils are replaced by macrophages

Epithelial cells cover surface

Question 28

What happens in the third day of healing by primary intention?

Answer 28

Granulation tissue formation

Question 29

What happens in the fifth day of healing by primary intention?

Answer 29

Collagen deposition

Question 30

Why would a wound heal by secondary intention?

Answer 30

Large, messy wound

Question 31

What special type of cell exists in healing by secondary intention?

Answer 31

Myofibroblast

Pulls wound together

Question 32

What local factors influence healing?

Answer 32

Poor vascular supply
Infection
Foreign material
Excessive movement
Gaping wound
Size, site and type of injury

Question 33

What systemic factors influence healing?

Answer 33

Age
Nutrition
Diabetes
Steroids
Malignancy

Question 34

Why is healing poor in diabetics?

Answer 34

Poor blood supply
Impaired macrophage function
Bacteria like high blood sugar

Question 35

What is Walker’s law?

Answer 35

Day 7 the wound is at 10% strength

After 3-4 months wound is at 80%