Repair and Regeneration Flashcards
What is repair?
Damaged cells cannot be replaced by like.
Fibrosis and scarring.
Loss of specialised function.
What is a labile cell population?
High normal turnover
Active stem cell population
Excellent regenerative capacity
- eg Epithelia
What are stable (quiescent) cell populations?
Low physiological turnover
Turnover can massively increase if needed
Good regenerative capacity
- eg liver, renal tubules
What are permanent cell populations?
No physiological turnover
Long life cells
No regenerative capacity (nb recent stem cell research)
- eg neurons, muscle cells
What are stem cells?
Prolonged self-renewal
Asymmetric replication
Reservoirs present in many adult tissues (‘Adult’stem cell ‘niches’)
What types of injury may cause the destruction of stem cells?
Full-thickness burns
Radiation
What processes take part in the control of regeneration?
Proliferation of stem cell / amplifying cell compartments
Covering of defect
Contact inhibition
Complex control by growth factors, cell-cell and cell-matrix interactions
What key things does the process of regeneration depend on?
Restoration of normal structure / function
Depends on tissue cell kinetics, architecture
Depends on stem cell survival
What is the name given to the tissue that eventually matures into fibrous scar tissue?
Granulation tissue
Describe the process of granulation.
New capillary loops form.
Phagocytic cells move into dead tissue and start clearing.
Proliferation and migration of myofibroblasts- synthesise collage and ECM.
Acquire myofibrils and contractile ability.
What factors may inhibit healing?
Local:
- Infection
- Haematoma
- Blood supply
- Foreign bodies
Systemic:
- Age
- Drugs (eg steroids - induce a catabolic state)
- Anaemia
- Diabetes
- Malnutrition
- Catabolic states
- Vitamin C deficiency
- Trace metal deficiency
- Mechanical stress
What is healing by first intention?
Clean, uninfected surgical wound
Good haemostasis
Edges apposed eg with sutures or staples
What is healing by second intention?
Wound edges not apposed
Extensive loss of tissue
Apposition not physically possible
- i.e. Large haematoma, infection, foreign body
More florid granulation tissue reaction (“leaving a wound to granulate”)
More extensive scarring
What is the healing process process for fracture?
Haematoma is organised
Removal of necrotic fragments
Osteoblasts lay down woven bone
- (=callus)
Remodelling according to mechanical stress
Replacement by lamellar bone
What happens when the brain tries to heal?
Neurons are terminally differentiated
Supporting tissue is glial cells rather than collagen and fibroblasts etc
Hence damaged tissue is removed, often leaving cyst
Gliosis rather than scarring
