Repair and Regeneration Flashcards
What are the two types of healing and define them
- Regeneration: Damaged cells replaced, tissue returns to normal
- repair: damaged cells cannot be replaced, loss of specialised function by fibrosis & scarring
Name the 3 types of cell populations
- Labile
- Stable (quiescent)
- Permanent
Describe labile cell populations
- High turnover
- Active stem cell population
- Excellent regenerative capacity
- Epithelia
Describe the stable cell population
- Low physiological turnover
- Turnover can massively increase if needed
- Good regenerative capacity
- Renal tubules
Describe permanent cell populations
- No physiological turnover
- Long life cells
- No regenerative capacity
- Neurons, muscle cells
Why are stem cells important?
- Crucial to regeneration
- Destruction can be through radiation & full thickness burns
How is regeneration controlled?
- Proliferation of stem cells
- Covering of defect
- Contact inhibition
- Complex contol by frowth factors (cell-cell & cell-matrix interactions)
What is organisation?
- Basic pathological process
- Repair of specialised tissue by formation of fibrous scar & granulation tissue
What is granulation tissue?
- New capillary loops
- Phagocytic cells- neutrophils & macrophages
- (Myo)fibroblasts
How are new blood vessels formed?
- Endothelial cell proliferation
- Buds
- Canalisation
- New vessels
How are new muscle fibres formed and how does wound contraction occur?
- Proliferation & migration of myofibroblasts
- Synthesise collagen & ECM
- Acquire myofibrils & contractile ability
- Wound contraction
What local factors can inhibit healing?
- Infection
- Haematoma
- Blood supply
- Foreign bodies
- Mechanical stress
What systemic factors can inhibit healing?
- Age
- Drugs (steroids)
- Anaemia
- Diabetes
- Malnutrition
- Catabolic states
- Vit C deficiency
- Trace metal deficiency
What is healing by first intention?
- clean, uninfected surgical wound
- Good haemostasis
- Edges apposed with sutures/staples
What is healing by second intention? When is this type of healing used? What does this lead to?
-Wound edges not apposed- healing naturally
-Extensive loss of tissue
-Large haematoma
-Infection
-Foreign body
Leads to: More extensive scarring, more florid granulation tissue reaction
Describe fracture healing
- Haematoma is organised
- Removal of necrotic fragments
- Osteoblasts lay down woven bone
- Remodelling according to mechanical stress
- Replacement by lamellar bone
How can non-union of fractures occur?
- Movement
- Misalignment
- Infection
- Interposed soft tissue
- Pre-existing bone pathology
How does healing in the brain occur?
-Neurons are terminally differentiated
-Supporting tissue is glial cells rather than collagen
-Hence damaged tissue is removed leaving a cyst
-Gliosis rather than scarring
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What are Koch’s postulates?
- Causative organism must be isolated from every individual suffering from the disease
- Causative organism must be cultivated artificially in pure culture
- Causative organism is inoculated from pure culture, the typical symptoms of the infection must result
- Causative organism must be recoverable from individuals who are infected experimentally
What is Koch’s postulates for genes?
- Genes encode virulence factors
- Gene encoding the trait should be present & transcribed in a virulent strain
- Gene encoding the trait should not be present or should be silent in a strain that does not cause disease
- Disruption of the gene in a virulent strain should result in the formation of a strain that is incapable of causing disease
- Intro of the gene that did not previously cause the disease shuld transform the strain into one that does cause disease
- The gene must be expressed during infection
- Antibodies raised against the gene product or appropriate cell-mediated immunity should protect experimental subjects against disease
What are problems with Koch’s postulates?
- Difficulty of isolation the causative agent
- Impossible to grow some pathogens in artificial culture (leprosy)
- Ethical objections
- Animal models not sufficient
Describe the structure of viruses
- Nucleic acid core wrapped in a protein coat made up of capsomeres
- DNA or RNA
- Some have an envelope
Give examples of disease causing viruses
- Herpes simplex virus
- Respiratory syncytial virus (infects only cells of the resp tract)
- Adenovirus
What are bacteriophage
-Class of viruses that attack bacteria
