Acute Inflammation Overview

Acute Inflammation

• Acute inflammation is a protective response
• It is non-specific, meaning the sequence of changes doesn't depend on the stimulus causing it
• Local changes include tissue necrosis, vascular changes, and exudative phenomena
• Systemic reactions include fever and leukocytosis
• The four cardinal signs of inflammation are redness, heat, swelling, and pain
• Vascular changes involve transient vasoconstriction followed by vasodilation, increased vascular permeability, fluid exudate formation, and emigration of leukocytes. (neutrophils first, then macrophages)
• Cellular exudate is the escape of inflammatory cells outside the blood vessels to the irritant, guided by chemotactic factors
• Chemotaxis occurs after transmigration; it is the directed movement of inflammatory cells on a fibrin network toward the irritant; this movement is guided by chemical substances (e.g., C3a and C5a, bacterial products)
• Leukocyte activation involves the production of eicosanoids (arachidonic acid derivatives), degranulation, and cytokine secretion
• Phagocytosis involves recognition, engulfment, and destruction of foreign material by phagocytic cells (neutrophils and macrophages). The steps include recognition and attachment, engulfment, and destruction
• Fate of acute inflammation includes resolution, healing by fibrosis, progression to chronic inflammation, and suppuration with abscess formation and infection spread
• Systemic effects of acute inflammation include fever, caused by exogenous and endogenous pyrogens (e.g., cytokines) and resulting in leukocytosis which is common with bacterial infections
• Termination of acute inflammation involves the short half-lives of chemical mediators, neutrophils (which eventually die by apoptosis), production of anti-inflammatory cytokines, and neural inhibition of TNF production
• Molecules involved include O2 free radicals, adhesion molecules, intra-cellular contractile fibers, and increased intra-cellular Ca+

Objectives of Module

• Understand the chain, progression, and sequence of vascular and cellular events in the evolution of acute inflammation
• Describe the roles of various chemical mediators of acute inflammation
• Define the possible outcomes of acute inflammation
• Visualize the morphologic patterns of acute inflammation

Case Scenario

• A clinical study of patients with pharyngeal infections shows an average clinical course of 3 days from onset until the physician's visit
• Most commonly, the patients have fever, chills, swelling, erythema, and pharyngeal purulent exudate
• The case scenario asks to identify the most likely type of inflammation from among the various types of inflammation present

This quiz delves into the essentials of acute inflammation, covering its protective response, local and systemic changes, and the four cardinal signs. You'll explore the processes of vascular changes, leukocyte activation, and the role of chemotaxis in the inflammatory response.