Body Response To Tissue Damage: Chronic And Granulomatous Inlfammation Flashcards
Examples of resolution
Lobar pneumonia:
Bacterial
Cells lining alveoli die but stroma and vascular structure remain intact
With antibiotics causative bacteria is removed
Neutrophils make the exudate highly liquid and it is reabsorbed in to lymph
Remnant epithelial stem cells divide to re line the alveoli
Tubular necrosis
Sunburn
Resolution
Occurs when there has been minimal damage to the tissue architecture-> cells can re grow
Acute inflammatory exudate eliminates agent
Exudate removed by neutrophils, phagocytosis by macrophages and fluid drainage in to lymph
Damaged cells regenerate
Normal function regained
Uncommon
Regeneration limited to cells that can still divide
Abscess formation
Extensive tissue necrosis
Caused by pyogenic (pus forming) bacteria-> secrete necrotoxins
Mass of necrotic tissue
Dead and viable neutrophils suspended in Purulent exudate
Acute abscess-> surrounded by acute inflammatory exudate
Chronic abscess-> scar tissue starts to form
Organisation and repair
Substantial structural damage to tissue stroma
Healing can’t occur by resolution
Remove debris
Grow new vessels and support cells
Stages of organisation and repair 1)
1) Pre existing capillaries from undamaged tissue form new capillaries by budding into the damaged area.
Damaged area infiltrated by macrophages, fibroblasts and myofibroblasts
Macrophages phagocytise exudate and dead tissue
Vascular granulation tissue-> fragile complex of interconnecting capillaries, macrophages and support cells develope
Organisation of exudate
Organisation and repair 2
Progressive growth of fibroblasts and myofibroblasts
More complex capillary network
Few residual macrophages
Organisation and repair 3
Continued proliferation of fibroblasts
Active collagen synthesis begins
Majority of capillaries regress-> some acquire smooth muscle and function as arterioles/venues
Fibrovascular granulation tissue
Organisation and repair 4
Intervening spaces between vessels become progressively filled with fibroblasts synthesising collagen
Fibrous granulation tissue
Fibroblasts aligned so they lay collagen running in a direction that provides maximum strength
Contraction of the area frequently via contractile effects of myofibroblasts to reduce area size.
Organisation and repair 5
Production of dense collagen forms a collagenous scar
Fibroblasts assume a resting status-> fibrocytes
Fibrous repair
Chronic inflammation definition
When a damaging stimulus persists so complete healing can’t occur
Organisation with continued inflammation and necrosis
Tissues infiltrated with immune cells
Necrotic debris, acute inflammatory exudate, vascular and fibrous granulation tissue, lymphoid cells, macrophages and collagenous scar
Persists until damaging stimulus removed
Causes of chronic inflammation
Damaging stimuli can’t be eradicated
Bacteria persist because they are distanced from neutrophils, antibiotics
Bacteria persist because they are resistant to neutrophils phagocytosis
Examples of chronic inflammation
Chronic peptic ulcer:
Exudate organises into granulation tissue but in meantime more damage is caused on stomach by acid
-> acids removed-> heals with scar
-> acid persists-> damage overwhelms repair-> ulcer perforates
Mechanisms of chronic inflammation
Main effector cell is macrophages Activated by gamma interferon Develop voluminous cytoplasm Fusion of macrophages to produce giant cell Phagocytotic and secretory roles Secrete: Mediators of acute inflammation Highly reactive O2 metabolites Proteases and hydrolysis enzymes Cytokines, IL-1 and TNFa-> fibroblast proliferation and collagen synthesis Growth factors-> PDGF, EGF, FGF
Granulomatous inflammation definition
Chronic inflammation where neutrophil phagocytosis is inadequate to neutralise the causative agent
Acute inflammation quickly replaced by immune-based cellular reaction-> aggregation of macrophages and lymphocytes
Macrophages often form discrete clusters-> granulomas
Stimuli of granulomatous inflammation
Microorganisms of low inherent pathogenicity but which excite a type IV immune response. Eg mycobacterium
Non living foreign material in tissues, endogenous and exogenous
Fungi
Unknown factors-> sarcoidosis, collections of granulomas that form nodules in organs such as the lungs