Tissue injury & repair

Question 1

What is tissue regeneration?

Answer 1

Growth of cells and tissue to replace lost structures
- complete reconstruction of superficial wounds, intact tissue framework
- tissues with high proliferative capacity eg. liver regeneration
true regeneration = bone following fracture, epithelium following injury

Question 2

What 2 things make up tissue repair?

Answer 2

Combination of regeneration and scar formation

- deep wounds eg. myocardial infarction

Question 3

Healing by scar formation

- what happens after severe tissue injury?

Answer 3

damage to parenchyma and stroma
Fibro-proliferative response:
- deposition of collagen and ECM components
Persistent damage = chronic inflammation = fibrosis

Question 4

What is the sequence of healing?

Answer 4

Inflammation
Angiogenesis (growth of new blood vessels)
Migration & proliferation of parenchymal cells and fibroblasts
Scar formation
Connective tissue formation

Question 5

Healing by first and secondary intention

Answer 5

First: edges of wounds near to each other eg. surgical wound sutured together
Secondary: edges of wound not close to each other eg. more granulation tissue

Question 6

What are the local factors affecting wound healing?

Answer 6

Size, location type, infectious (foreign bodies delaying healing

Question 7

What are the systemic factors affecting wound healing?

Answer 7

Nutritional status, metabolic status, circulatory/vascular status, hormones (glucocorticoids)

Question 8

What are the 3 complications of tissue repair?

Answer 8

Deficient scar formation
Excessive repair 
- excessive granulation tissue
- excessive collagen accumulation = hypertrophic scar
- KELOID
Formation of contractures