6 Chronic Inflammation Flashcards
List the different outcomes of acute inflammation
- Resolution
- Abscess
- Organisation and repair (granulation of tissue = scarring)
- Chronic inflammation (organisation with continued inflammation and tissue-based immune response)
Describe resolution
- Acute inflammation exudate eliminates damaging agents
- Macrophages remove dead cells and exudate
- Local cells regrow
- Tissue structure and function returns to normal
- Not a common outcome following tissue damage and acute inflammation
e. g. where resolution occurred after acute inflammatino following:
- Pneumonia
- Tubular necrosis kidney
- Sunburn
What must happen for resolution to occur?
- There must be minimal damage to the architecture
- Allows normal sturcture and function to be restores
best e.g. is lobar pneumonia
- no damage to alveolar wall architecture
- exudate forms in alveolar air dacs
- Liquefied exudate is reabsorbed
- Alveolar lining cells regrow
What is an abscess?
- An abscess is a large accumulation of liquid purulent exudate (pus) in an area where the tissue damage has led to extensive necrosis
- It becomes ‘walled-off in an attempt to limit the spread of inflammation
- It is especially caused by bacteria e.g. staphylococcus
e.g. abscess in the lung
Describe organistation and repair
- Remove debris
- Grow new vessels and support cells
- Lay down collagen
- Collagen matures
- Granulation tissue matures to scar:
>Vascular, fibrovascular, and collagenous
Describe the organisation of exudate stage of organisation and reapir
- Capillaries grow into damaged area
- Fibroblasts migrate into area and mutliply
- Fibroblasts synthesise collagen
- New capillaries regress
- Fibroblasts regress
Describe the macrophage clearing debris stage
Macrophage phagocytose solid debris, and enzymes liquefy the rest of it
Describe the vascular granulation stage
- Capillaries grow into damageed area by budding from nearby vessels
- Capillary netwrok is fromed
- Some fibroblasts move in
> Angiogenesis is driven by specific growth factors and receptors. The myofibroblast cells have ability to secrete collagen as well as contractile smooth-muscle like ability
Describe the histology of vascular granulation tissue
- New capillaries dominate hisotlohy
- Residual inflammatory cells remain
Describe the fromation of fibrovascular granulation tissue
- Fibroblasts proliferate and excrete collagen fibers
- Capillary network still present but less prominent
> Many of the cells are myofibroblasts - also can contract
Describe the histology of fibro-vascular granulation tissue
- Mixture of capillaries and fibroblasts
Describe the formation of fibrous granulation tissue and scar (fibrous repair)
- Most new capillaries regress
- Fibroblasts align and secrete large amounts of collagen fibre
> Myofibroblast contraction reduces the volume of tissue and causes contraction of the damaged area
Describe the histology of fibrous granulation tissue and scar
- Few capillaries remain
- Histology dominated by newly formed collagen and fibroblasts
Describe the process of healing by repair
- The formation of scar following tissue damage is an example of healing by repair
- In contrast to resolution, restoration of normal structure and function of damaged tissue does not occur
Describe chronic inflammation
When a damaging stimulus persists, complete healing cannot occur, and chronic inflammation ensues
- Damage, organisation, and repair occur concurrently
- Tissue is infiltrated by specific immune effector cells
- Always heals by scarring