8 Repair and regeneration Flashcards
Differentiate between regeneration and repair of damaged tissue.
Regeneration: cells replaced by like, tissue returns to normal, specialised function resumes.
Repair: cells cannot be replaced by like, granulation tissue, results in fibrosis and scarring, loss of specialised function.
What is a labile cell population?
Regenerative capacity?
Example?
High normal turnover with active cell population.
Excellent.
Epithelia.
What is a stable (quiescent) cell population?
Regenerative capacity?
Examples?
Low turnover that can massively increase if needed.
Good.
Liver, renal tubules.
What is a permanent cell population?
Regenerative capacity?
Examples?
No physiological turnover, log lived cells.
None.
Neurons, muscle cells.
What are the architectural considerations involved in tissue regeneration?
Rebuilding of complex architecture is limited (glomeruli, lung).
The extent of the survival of connective tissue framework.
What are the controlling factors in regeneration? (3)
Covering of defect.
Contact inhibition between cells.
Growth factors, cell-cell and cell–matrix interactions.
Granulation tissue results in wound contraction during repair. What three functions allow this?
Endothelial cell proliferation forms new vessels.
Phagocytes remove dead/damaged tissue.
Myofibroblasts proliferate and migrate, synthesise collagen and ECM, yielding contractile ability.
How do the properties of granulation tissue change as it matures?
And over what time scale?
Decreasing vascularity and cellularity.
Increasing collagen, extracellular matrix, and wound strength.
3 months.
Factors that inhibit healing.
Infection, haematoma, blood supply, foreign bodies, mechanical stress.
Age, drugs, anaemia, diabetes, malnutrition, catabolic states, Vit C/trace metal deficiency,
When does healing by first intention occur?
Clean uninfected surgical wound with good haemostats, and edges apposed by sutures/staples.
When does healing by second intention occur and how is it different to first intention?
Wound edges not apposed (tissue loss, haematoma, infection, foreign body).
More florid granulation tissue reaction and more extensive scarring.
At which day are sutures typically taken out?
Day 7.
How do bone fractures heal?
Organised haematoma with removal of necrotic fragments. Osteoblasts lay down woven bone (callus), which remodels according to mechanical stress. replaced by lamellar bone.
How does brain tissue heal?
Gliosis.
Neural tissue is terminally differentiated and the only supporting tissue is glial cells. Damaged tissue is removed, leaving a cyst.
Which growth factors are involved in wound healing? (7)
EGF (epidermal) TGF-α (transforming). TGF-β (transforming) PDGF (platelet derived) KGF (keratinocyte) TNF (tumour) VEGF (vascular endothelial)
