Classification of Phlogogenic Factors
Causes of inflammation are typically classified according to several basic criteria. By origin, they are divided into exogenous (originating from the external environment) and endogenous (originating within the organism itself). Regardless of the source, any of these agents can be of infectious or non-infectious nature.
From a physicochemical perspective, there are three main groups: physical, chemical, and biological stimuli. Their nature and the intensity of exposure determine how acutely the signs of the inflammatory process will manifest.
Chemical and Biological Agents
Chemical causes of inflammation include both external substances and internal compounds. These encompass organic and inorganic acids and alkalis. Endogenous chemical triggers often include biological fluid components in excess: bile, urine, urea, calcium salts, as well as lactic and pyruvic acids. Inflammation can also be caused by medications administered directly into tissues—such as camphor, certain vitamins, carbonates, and hypertonic solutions (sodium, potassium, or calcium chloride).
Biological factors include:
- Infectious agents: viruses, bacteria, fungi, rickettsiae, and mycoplasmas.
- Toxins: plant, insect, and animal venoms.
- Immunoallergic factors: antigen-antibody complexes.
Exogenous and Endogenous Triggers
Among exogenous factors, besides microbes and toxins, inflammation is frequently provoked by foreign blood plasma and serum (e.g., administered during vaccination), cell suspensions, and transplants.
Endogenous causes deserve special attention because the process is triggered by the body's own resources. A powerful stimulus is provided by the breakdown products of autologous tissues resulting from necrosis due to ischemia, severe contusions, burns, or frostbite. Inflammation can also be provoked by a suddenly activated resident microflora, the accumulation of altered metabolic products, or the formation of immune complexes involving the complement system. Additionally, genetically foreign structures act as triggers, such as virus-infected or tumor cells, as well as denatured proteins.
The Role of Body Reactivity
The conditions under which a phlogogenic factor acts determine whether inflammation occurs, the features of its clinical course, and its final outcomes. A critical condition is the type of reactivity:
- Normergic inflammation — the scale and severity of the reaction are entirely adequate to the causative factor.
- Hyperergic inflammation — a rapid, qualitatively altered, and excessive response. Observed in sensitized individuals during allergic reactions.
- Hypoergic inflammation — a sluggish reaction with poorly defined signs. Typical for newborns, pregnant women, the elderly, and patients exhausted by severe chronic diseases.
Local circulatory disorders, dystrophic processes, impaired local immune factors, and chronic local tissue trauma significantly facilitate the realization of pathogen effects.
Main Stages of the Process
Regardless of etiology, the pathogenesis of inflammation follows a strict sequence of stages. It begins with alteration (Latin alter — other, changed) — primary tissue damage. This is followed by vascular reactions altering blood and lymph flow. This leads to plasma exudation and leukocyte emigration (along with other formed blood elements) into the damaged tissue. The process culminates in phagocytosis and proliferation stages aimed at cleansing and repairing the lesion.