Classification of injuries

The essence of the inflammatory process

Inflammation is a complex dialectical reaction of the body, combining destructive (pathogenic) and protective (adaptive) mechanisms. Initiated as a local reaction to a damaging agent (phlogistic factor), inflammation can involve all body systems, becoming a key link in pathogenesis.

The biological direction of inflammation is aimed at limiting the focus of damage, removing the pathogenic agent, and subsequent restoration of tissue structures. Whether this reaction turns out to be lifesaving or fatal depends on the body's reactivity, including hereditary factors (e.g., the HLA system).

Interestingly, inflammation is based on normal physiological mechanisms: physiological alteration, phagocytosis, hemocoagulation, and cell maturation. According to I.V. Davydovsky, the physiological analogue of inflammatory reactions is the menstrual cycle, which also involves alteration, exudation, and proliferation.

Three mandatory components of inflammation

The classification of the inflammatory process (destructive, exudative, productive) depends on which phase predominates. However, all three phases are necessary for inflammation to occur:

1. Alteration — direct tissue damage, the initiating stage.
2. Exudation — a vascular reaction with the release of fluid and blood cells.
3. Proliferation — cell multiplication for repair.

The expanded scheme of pathogenesis includes five links: alteration, vascular reactions, exudation, phagocytosis, and proliferation.

Stage 1: Alteration

Alteration (alter — changed) is the initial link of inflammation, the result of a phlogistic agent's impact. It is accompanied by the release of inflammatory mediators and changes in the structure, metabolism, physicochemical properties, and functions of the tissue.

There are biochemical and morphological phases, as well as primary and secondary zones of alteration in the focus. The biological significance of alteration is twofold:

• Protective role: localization and destruction of the pathogen.
• Pathogenetic basis: triggering subsequent reactions (vascular changes, exudation, phagocytosis).

At the molecular level, alteration triggers the release of histamine, serotonin, prostaglandins, kinins, and cytokines. They cause vasodilation, increased vascular permeability, and recruit leukocytes.

Stages 2 and 3: Exudation and Proliferation

Stage of vascular changes and exudation Inflammatory hyperemia develops. The liquid part of the blood, rich in proteins, and formed elements (including leukocytes) pass from capillaries and venules into the tissues. Leukocyte emigration occurs (margination, adhesion, diapedesis) into the damage focus to perform phagocytosis.

Stage of proliferation This is the final phase (proliferatio — to produce offspring), the purpose of which is to restore tissue integrity. At this stage, damaged elements are eliminated by obligate phagocytes (neutrophils and macrophages), whose number in the focus increases sharply. After cleansing the focus, cell multiplication and connective tissue formation begin.

Class and exam questions

What else to study on this topic

• Inflammatory mediators: classification and mechanisms of action
• Mechanisms of leukocyte emigration and stages of phagocytosis
• Types of exudative inflammation
• Productive (proliferative) inflammation and its forms
• Clinical (cardinal) signs of inflammation

Other topics in the "Additional Topics" section

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