PMI03-2024 Flashcards
What is meant by the term regeneration?
Replacement of lost/damaged tissue by that of a similar type, derived from the proliferation of surrounding undamaged cells
What is meant by the term resolution?
Return to original morphological and functional state with little damage
Give an example of a tissue that can undergo regeneration.
Liver
Blood
What is meant by the term repair?
Replacement of lost/damaged tissue by granulation tissue which later matures into either fibrous scar tissue or other tissue
What are the two types of repair processes and which is helpful?
Healing = helpful repair
Fibrosis = unhelpful
What is the term healing generally used for?
Small skin wounds
When does healing by primary intention occur?
When wound edges are in close apposition
When does healing by secondary intention occur?
When wound is more extensive and wound edges are widely separated
What is the key element of healing by primary intention?
Re-epithelialisation
What are the stages in healing and when do they occur after injury?
- Haemostasis ~1 hour
- Inflammation ~48 hours
- Re-epithelialisation ~1-3 days
- Granulation tissue formation ~2-5 days
- Maturation ~5 days
What happens in the haemostasis step of healing?
Platelet plug and fibrin clot formation
How can warfarin, aspirin or factor VIII deficiency affect wound healing?
Inhibits haemostasis so inhibits wound healing
What is involved in the inflammation stage of healing?
Macrophage infiltration and debridement
What is granulation tissue?
Loose cellular connective tissue with many plump synthetic fibroblasts, dilated, irregular blood vessels and inflammatory cells
Describe the granulation tissue formation stage of wound healing.
Connective tissue component
Endothelial cell and fibroblast formation from wound edges give rise to new blood vessels
Blood vessels migrate out into wound area accompanied by fibroblasts and inflammatory cells to lay down collagen ECM
Describe the re-epithelialisation stage of wound healing.
Epithelium component
Proliferation of basal epithelial cells adjacent to wound
Migration of basal epithelial cells across wound bed, under fibrin scab to restore epithelial continuity
Basal cells differentiate to reform stratified squamous epithelium
What are traditional macrophage functions involved in wound healing?
Phagocytosis
Protease synthesis
Regulation of immune cell function
Growth factor production
Give two examples of growth factors produced by macrophages which are involved in wound healing.
FGFs = fibroblast recruitment and activity
VEGF = endothelial cell recruitment and activity
What systemic factors can influence wound healing?
Age
Nutritional status
Iatrogenic/medications
Pre-existing medical conditions
What local factors can influence wound healing?
Blood supply
Infection
Persistent irritation
Poor wound stability
Poor apposition of wound edges
Direction of incision (Langers lines)
Ionising radiation
What does wound dehiscence mean and what can it result in?
Re-opening of wound
Hernias
What does contracture mean?
Normally elastic tissues are replaced by inelastic tissues (fibrosis) leading to rigidity
What can exaggerated, hyperplastic wound healing responses cause?
Keloids
Hypertrophic scar formation
Describe a keloid.
Sharply elevated, progressively enlarging scar
Characterised by formation of excessive amounts of collagen in the dermis during connective tissue repair
May spread beyond margins of original wound
Characteristically found in Afro-Caribbean populations
What wound healing complications can affect the face/skin but not the oral mucosa?
Keloids and hypertrophic scarring
Marjolin ulcers
What is the difference between hypertrophic scarring and keloids?
Hypertrophic scarring does not spread past wound margins and affects varied population groups
Which cells are responsible for contraction/bring edges of wound closer together?
Myofibroblasts
