Inflammation. Definition, etiology, pathogenesis, types
Inflammation is the body's response to harmful stimuli, such stimuli include:
- Mechanical damage
- Physical damage (e.g. Radiation, UV, Temperature)
- Chemical damage
- Biological damage (e.g. Viruses, bacteria)
Inflammation can be classified acute or chronic. Acute being the initial response, achieved through plasma and leukocyte movement (especially neutrophil), while prolonged inflammation is chronic, and tends towards a predominance of mononuclear cells, where we observe simultaneous destruction and healing of the tissue.
There are three main stages of inflammation which can vary in intensity and duration, these stages are:
- Vasodilation and increased vessel permeability
- First, very brief vasoconstriction followed by prolonged vasodilation
- This is a result of an increase histamine, kinins, prostaglandins and other cytokines
- Phagocyte migration and phagocytosis
- Increase in permeability of vessels for plasma proteins
- Margination, Rolling, Adhesion and Diapedesis (transmigration into extra cellular space) of neutrophils (emigration)
- Chemotaxis (due to cytokines)
- Pus formation (more on these three stages in pathology document)
- Tissue repair and regeneration
The clinical signs of inflammation are:
- Colour
- Heat
- Swelling
- Pain
- Impaired function
- Vascular changes
- And Phagocytosis
Remember: the five cardinal signs in Latin are rubor (redness), calor (heat), tumor (swelling) and dolor (pain), described by Celsus, plus functio laesa (loss of function), added by Virchow.
(note only the first five refer to the gross signs of inflammation, the others are physiological or microscopic).