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
What shapes can viruses take?
- rod-shaped
- round
- brick-shaped
- bullet-shaped
- icosahedral
Describe microfungi
- Fungi are eukaryotic
- Most possess a cell wall of chitin
- Moulds = fungi that grow in mats of tiny filaments= hyphae
- Form mats= Mycelia
- May or may not subdivide into separate compartments=Septa
Describe Protists
- Unicellular eukaryocytes
- 4 classes= Apicomplxa, Flagellate Protista, Ciliate Protista, Amoebae
What infections are caused by protists
- Malaria
- Amoebic meningitits
- Amoebic dysentry
- Diarrhoea
What can Trichomonas Vaginalis cause?
- Vaginal infections
- Causes foul-smelling vaginal discharge
- Men asymptomatic carriers protists can cause balantitis in men
What are the most common shaped bacteria?
- Cocci= round
- Bacilli= rod-shaped
Describe the outer membrane of Gram negative bacteria
- outer leaflet containing lipopolysaccharide
- Sugars form surface antigen
- Lipid A acts as endotoxin responsible for symptoms
What can help a bacteria stick to surfaces?
Produce slime (strep mutans) such as surface of teeth forming plaque and leading to dental caries or strains of staphylococci living on skin help them to stick to plastics- infections associated with implanted medical devices
What highly resistant structures can be produced by some bacteria?
- Endospores
- Resist a range of hazardous environments
- Protect against hear, radiation, desiccation
Which infections can be spread through drinking water?
Water contaminated with human faeces -Typhoid Cholera -Hep A -Dysentry -Poliomyelitits
What are fomites?
Inanimate objects which act as vectors of infection
What are intoxication illnesses? (NOT DRINKING)
- Tetanus & botulism/ergotism
- Victim only needs to be exposed to toxin not live microorganism
- Tetanus= lock jaw as muscles go into rigid spasm (risus sardonicus)
What are virulence factors?
Traits used to complete the cycle of infection
What are the mechanisms by which bacteria cause disease?
-Production of toxins (endo/exotoxins)
-Exploiting production of structures that enable microorganisms to attach to surfaces
-Production of aggressins
Initiating undesirable consequences of host defences
