Inflammation is a response to a noxious stimuli which can be either be acute or chronic.
In acute inflammation there are vascular and exudative phases.
- vascular: dilatation and increased permeability
- exudative: fluid and cells escape from permeable venules
The outcome of acute inflammation can be:
- resolution (restoration of normal function)
- non resolution
- organisation (scarring)
- progression to chronic inflammation
Chronic inflammation occurs when there is a persistent damaging stimulus. This eventually heals by either scarring or granuloma formation.
Chronic inflammation is characterised by infiltration with mononuclear cells (macrophages, lymphocytes).
Granulomatous inflammation is specific subtype of chronic inflammation charcterised by aggregation of epitheliod histiocytes. Examples of Type IV hypersensitivity reaction include:
- infections (tuberculosis)
- foreign bodies
- idiopathic (eg. sarcoid)