6. Healing and Repair Flashcards
What is healing?
Replacement of a destroyed tissue with a viable tissue
What is resolution?
Tissue returns to its pre-injury state
What situation does resolution happen in?
No tissue destruction
Damaging agent and cell debris are removed
What is regeneration?
Replacement of the lost tissue by a tissue of the same type
What is repair?
Replacement of the destroyed tissue by a fibrous scar
What factors affect the healing process?
Remove causative agent, inflammatory debris
Amount of damage
Ability of cell to proliferate
Extent of ECM damage
Where are labile cells found?
Epidermis
GIT
Mucosal epithelium
How do labile cells heal?
Regeneration (if stroma is intact)
What stage of the cell cycle are stable cells in?
G0
Where are stable cells found?
Liver
Kidney
Pancreas
How do stable cells heal?
Regeneration if stroma and stem cells are intact
Where are permanent cells found?
Neurons, heart, skeletal muscle
How do permanent cells heal?
Fibrosis
What is the most important mediator affecting cell growth?
Polypeptide growth factors
What is the stroma made up of?
ECM
Mesenchymal cells (multipotent stem cells)
Vessels
What does the ECM consist of?
Fibrous structural proteins
Glycoproteins for adhesion
Proteoglycans
When does fibrosis happen?
Destruction to cells and stroma
Death of permanent cells
Inflammation
What is produced when tissue is repaired by fibrosis?
Granulation tissue
What is granulation tissue?
Fibroblasts and blood vessels
What are the 3 phases of wound healing?
Inflammatory phase
Proliferative phase
Remodelling phase
What happens in the inflammatory phase?
Haematoma formation
Infiltration by neutrophils
Neutrophils replaced by macrophages
What happens in the proliferative phase?
Epithelial cell proliferation
Granulation tissue formation
What is the remodelling phase?
Granulation tissue converted to fibrous tissue to provide strength
What enzyme breaks down excessive scarring?
Metalloproteinase
What case does healing by primary intention happen in?
Minimum loss of tissue
What happens in the first day of healing by primary intention?
Haematoma formation
Acute inflammation
Proliferation of epithelial cells
What happens in the second day of healing by primary intention?
Neutrophils are replaced by macrophages
Epithelial cells cover surface
What happens in the third day of healing by primary intention?
Granulation tissue formation
What happens in the fifth day of healing by primary intention?
Collagen deposition
Why would a wound heal by secondary intention?
Large, messy wound
What special type of cell exists in healing by secondary intention?
Myofibroblast
Pulls wound together
What local factors influence healing?
Poor vascular supply Infection Foreign material Excessive movement Gaping wound Size, site and type of injury
What systemic factors influence healing?
Age Nutrition Diabetes Steroids Malignancy
Why is healing poor in diabetics?
Poor blood supply
Impaired macrophage function
Bacteria like high blood sugar
What is Walker’s law?
Day 7 the wound is at 10% strength
After 3-4 months wound is at 80%
