Lecture: Pathology 4: How the body recovers from injury Flashcards
What are the 2 responses of the body following injury?
Regeneration or repair (or incomplete regeneration)
How are scars formed?
Connective tissue deposition (fibrosis) resulting in a fibrotic scar.
What are macrophages?
Circulating blood monocytes which migrate into tissue.
What are the roles of macrophages?
Macrophages clear offending stimuli, dead tissue and produce growth factors for the proliferation of various cells in the healing response. Also involved in chemotaxis, hypertrophy and phagocytosis.
What is regeneration?
Process by which cells and tissue structures are restored to their normal state, without scarring.
What is regeneration dependent on?
Regeneration is dependent on limited damage and the preserved integrity of the extracellular matrix (scaffolding) or basement membrane. Regeneration usually impossible and results in scarring.
Where does regeneration occur?
Labile (dividing) or stable (quiescent). Permanent tissues can only heal by repair.
What are adult stem cells?
Cells that have prolonged self renewal capacity and asymmetric replication. Cells that have not undergone terminal differentiation, but can usually only differentiate into certain types of cells.
How do cells undergo regeneration?
Complex process that relies on interactions involving macrophages and the stromal scaffolding / extracellular matrix. Dependent on production of growth factors and transcription factors (mainly by macrophages) which induce signalling pathways to unlock cell cycle controls.
What triggers healing by repair (scarring)?
Occurs when tissue damage is too extensive for resolution or regeneration (e.g. loss of reticulin network in the liver).
What is granulation tissue?
Type of new connective tissue formed in response to injury that is composed of new blood vessels, fibroblasts and remaining inflammatory cells (usually neutrophils). New vessels are leaky contributing to oedema/swelling/tumour.
How is granulation tissue formed?
Angiogenesis + proliferation of fibroblasts (via TGF-beta)
How do scars occur?
Fibroblasts migrate into granulation tissue and patch the tissue damage with fibrosis to form fibrotic scar. Migration is controlled by fibroblast growth factors (FGFs) where as the scar formation is controlled by transforming growth factor beta (TGF-beta).
What is the process of scar formation?
- Haemostasis and blood clotting
- Inflammation
- Formation of granulation tissue (angiogenesis + fibroblast prolif.)
- Formation of connective tissue/scar
- Remodeling of the scar
- Final scar
What is angiogenesis?
Formation of new blood vessels.
