Inflammation Overview and Causes

Inflammation

• Inflammation is the local vascular, lymphatic, and cellular reactions of living tissues to an irritant (injurious agent).
• It's a protective mechanism aiming to localize and remove the irritant.
• Inflammation is identified by adding the suffix "-itis" to the affected organ name (e.g., pulpitis, osteomyelitis).

Causes of Inflammation

• Living irritants: bacteria, their toxins, viruses, parasites, and fungi.
• Non-living irritants:
  • Physical: excessive heat, cold, irradiation.
  • Chemical: acids, alkalis, poisons.
  • Mechanical: trauma, friction.
• Antigens: cause allergic inflammation through antigen-antibody reactions, like bronchial asthma.

Types of Inflammation

• Acute inflammation:
  • Rapid response (sudden onset) to a short-acting irritant.
  • Lasts minutes to days.
  • Characterized by marked tissue edema (excess inflammatory exudate).
  • Key cells: neutrophils (PMNLs) and macrophages.
  • Prominent cardinal signs and vascular changes.
• Chronic inflammation:
  • Slow response (gradual onset) to a long-acting irritant.
  • Lasts months to years.
  • Characterized by mild tissue edema (scanty inflammatory exudate).
  • Progressive and productive inflammation with granulation tissue formation.
  • Key cells: lymphocytes, plasma cells, eosinophils, basophils, and macrophages.
  • Less prominent cardinal signs and vascular changes.

Acute Inflammatory Cells (PMNLs)

• PMNLs are polymorph nuclear leukocytes.

Chronic Inflammatory Cells

• Key cells: Macrophages, Lymphocytes, Plasma cells

Events of Acute Inflammation

• 1. Local tissue damage (necrosis of tissue).
• 2. Local vascular reaction (vasodilation of blood vessels, increased capillary permeability), leading to redness and heat.
• 3. Local reaction of tissue histocytes (macrophages) to clear tissue debris.

Fluid Inflammatory Exudate Composition

• High protein content (4-8 g/%).
• Primarily fibrinogen, which transforms into fibrin.
• Formed by plasma protein release from dilated blood vessels due to increased capillary permeability.

Function of Inflammatory Exudate

• Dilutes toxins, poisons, and chemicals.
• Brings antibodies to infection sites.
• Supplies nutrients to cells and eliminates waste products.
• Forms a fibrin network for PMNLs and macrophages to move towards irritants.
• Provides a platform for fibroblasts to proliferate, initiating repair.
• Localizes infection by surrounding the inflamed area.

Cellular Exudate

• Composed of neutrophils and macrophages (phagocytic cells).
• Phagocytosis: Ingestion and destruction of bacteria, necrotic debris, and foreign bodies by phagocytic cells.

Signs of Acute Inflammation

• Local:

  • Redness
  • Heat
  • Pain
  • Swelling
  • Loss of function

• Systemic:

  • Fever
  • Leukocytosis

Types of Acute Inflammation

• Suppurative (pyogenic or septic):

  • Characterized by pus formation.

  • Caused by pyogenic microorganisms (e.g., staphylococci, streptococci)

  • Examples: abscess, furuncle, carbuncle, and cellulitis.

  • Abscess: a localized collection of pus

  • Furuncle (boil): a localized abscess related to a hair follicle or sebaceous gland.

  • Carbuncle: multiple furuncles connected by strands of tissue.

  • Cellulitis: diffuse suppurative inflammation of subcutaneous and connective tissue.

• Non-suppurative. No pus formation.

  • Catarrhal
  • Pseudomembranous
  • Sero-fibrinous
  • Serous
  • Hemorrhagic
  • Necrotizing
  • Allergic

This quiz covers the basics of inflammation, its protective mechanisms, and types. Explore the various living and non-living irritants that can trigger inflammation, and understand the concept of acute inflammation. Test your knowledge on key terms and processes related to this essential biological response.