Healing and repair

Question 1

What is fibrosis

Answer 1

Accumulation of excessive amounts of fibrous tissue as a COMPLICATION of healing

Question 2

Principles of healing and repair

Answer 2

1. Regeneration and fibrosis occur simultaneously
2. Only labile (dividing) and stable cells can regenerate
3. The more specialised cells usually cannot regenerate (ie. Brain, heart, kidney)
4. The more injurious damage there is, the more fibrosis there is, especially if the underlying tissue framework is also damaged.
5. More tissue injury equates to more decreased tissue functionality

Question 3

Describe the process of healing and repair

Answer 3

1. Macrophages clear debris at the inflammatory site, including removal of neutrophils. They also secrete cytokines/growth factors for ECM synthesis (basically to boost collagen)
2. Cell proliferation/regeneration: Fibroblasts, endothelial cells and stromal stem cells form a fibrous scar tissue to replace the epithelial layer
3. Cell migration: Surface re-epithelization (cells on below undamaged layers of skin are pushed upwards to be the new upper layer and plug the gap)
4. Angiogenesis: blood vessel formation to support growth of the new cells
5. ECM synthesis & remodelling: Deposition of collagen and linking of collagen fibres to rebuild the tissue

Question 4

What is the effect of macrophage depletion or malfunction?

Answer 4

Delayed wound healing

Question 5

List at least 2 growth factors that stimulate ECM collagen synthesis

Answer 5

Fibroblast GF
Transforming GF

Macrophage-derived growth factor
Platelet-derived grown factor
Epidermal GF

Question 6

What is granulation tissue and what does it consist of?

Answer 6

Vascular connective tissue: angiogenesis and fibroblast proliferation (fibroblasts, myofibroblasts)

Question 7

Stages of healing

Answer 7

1. Granulation tissue
2. Wound contraction
3. Collagen synthesis and maturation
4. Scar maturation

Question 8

What are 2 nutrients vital for collagen synthesis

Answer 8

Vitamin C and zinc

Question 9

Factors affecting wound healing (systemic)

Answer 9

1. Age
2. Circulation of blood (diabetes slows down circulation)
3. Nutrition (zinc and vitamin c)
4. Hormones

Question 10

Factors affecting wound healing (local)

Answer 10

1. Movement (excessive movement before maturation of scar = tearing of collagen fibres)
2. Radiation

Question 11

Complication of wound healing

Answer 11

1. Defective scar - wound dehiscence (Partial or total separation of wound edges)
2. Incisional hernias (protrusion of tissue or organs that form at the site of a healing surgical scar)
3. Keloid scar - irregular fibrous tissue
4. Hypertrophic scar - excessive fibrous tissue

Question 12

List the stages of fracture healing

Answer 12

1. Haematoma
2. Granulation tissue and collagenous fibrous tissue
3. Proliferation of osteoblasts (young bone)
4. Formation of lamellar bone with good tensile strength (mature bone)