Inflammation Overview and Types

Inflammation

• Inflammation is a dynamic response of vascularised living tissue to injury. It's a protective response. It brings defense and healing mechanisms to the site of injury.

Aims of Inflammation

• Isolate injury
• Destroy invading microorganisms
• Inactivate toxins
• Prepare damaged tissue for repair and healing

Causes of Inflammation

• Infections
• Trauma
• Physical injury (e.g., heat, radiation)
• Chemical injury
• Immune-mediated reactions
• Adjacent to necrotic tissue

Cardinal Signs of Inflammation

• Calor: Warmth - Hyperaemia
• Rubor: Redness - Hyperaemia
• Dolor: Pain - Nerve, Chemical mediators
• Tumor: Swelling - Exudation
• Functio laesa: Loss of function

Types of Inflammation

Acute Inflammation

• Suppurative
  • Localized: abscess, furuncle, carbuncle
  • Diffuse: cellulitis
• Non-suppurative

Characteristics of Acute Inflammation

• Strong irritant
• Rapid response
• Short duration
• Vascular dilation
• Excess fluid exudate
• Polymorphonuclear leukocytes, eosinophils, macrophages

Characteristics of Chronic Inflammation

• Mild irritant
• Gradual onset
• Prolonged duration
• Mild vascular congestion and dilation
• Scanty fluid exudate
• Healing by fibrosis
• Lymphocytes, plasma cells, macrophages, giant cells

Acute Inflammation

• Definition: A rapid host response delivering leukocytes and plasma proteins (e.g., antibodies) to sites of infection or tissue injury.

Tissue Response

• Two main components:
  • Vascular response
  • Cellular response

Vascular Responses

• Vasodilation with increased blood flow
• Increased vascular permeability (proteins and cells)
• Leukocyte transmigration and chemotaxis

Vascular Responses - Mechanisms

• Histamine
• Bradykinin
• Prostaglandins and Leukotrienes
• Platelet Activating Factor
• Direct Endothelial Injury

Vascular Responses

• Immediate vasoconstriction
• Vasodilation
• Increased vascular permeability
• Contraction of endothelial cells with increased inter-endothelial space mediated by histamine and bradykinin
• Endothelial cell injury: Endothelial cells undergo necrosis and detachment by either direct effect of injurious agent or effect of neutrophils adherent to the wall.
• Transcytosis: Caused by interconnected uncoated vesicles and vacuoles called "vesiculo-organelles",that increase in size in inflammation.
• Formation of inflammatory exudate

Inflammatory Fluid Exudate

• Mechanism:
  • Vascular permeability
  • Capillary hydrostatic pressure
  • Osmotic pressure
• Amount depends on:
  • Tissue
  • Irritant
  • Lymphatic obstruction

Transudate vs Exudate

Extravasation of Cells

• Steps:
  • Intravascular (inside blood vessels):
    • Margination
    • Rolling and adhesion of leukocytes to endothelium
    • Transmigration across endothelium
  • Extravascular (outside blood vessels):
    • Chemotaxis
    • Phagocytosis

Cellular Responses - Neutrophil Recruitment

• Margination
• Pavementing
• Transmigration
• Chemotaxis

Chemotaxis

• Definition: Directed movement of neutrophils and macrophages in the inflamed area towards the irritant, depending on exogenous bacteria products and endogenous mediators (e.g., complement, arachidonic acid metabolites, chemokines).

Phagocytosis

• Definition: Ingestion and destruction of bacteria, necrotic debris, and foreign particles by phagocytic inflammatory cells. Similar to amoeba feeding.

Cellular Responses

• Opsonization and phagocytosis (Recognition)
  • C3b receptor
  • Fc receptor
  • Complement
  • Immunoglobulins
• Engulfment
• Killing and degradation
• Oxidative burst, bacterial killing, and tissue injury
  • Reactive Oxygen Metabolites
  • Lysosomal Enzymes

Suppurative Inflammation

• Localized inflammation:
  • Abscess: Cavity containing pus, commonly caused by staphylococcal infection, in subcutaneous tissues
• Diffuse forms:
  • Cellulitis (common in diabetics)
  • Suppurative appendicitis
  • Septic peritonitis

Non-Suppurative Inflammation

• Catarrhal (rhinitis, appendicitis)
• Membranous (diphtheria)
• Sero-fibrinous (serous membranes)
• Fibrinous (lobar pneumonia)
• Serous (burns, herpes)
• Haemorrhagic (hemolytic strep infection)
• Necrotizing (cancer of the oral cavity)
• Allergic (anaphylactic shock, asthma)

Chronic Inflammation

• Mild irritant, long duration
• Follows acute inflammation
• Mild vascular congestion, dilation
• Scanty fluid exudate
• Healing by fibrosis
• Chronic inflammatory cells (lymphocytes, plasma cells, macrophages, giant cells)

Chronic Inflammation - Types

• Non-specific
  • Chronic abscess
• Specific inflammation (granuloma)
  • Tuberculosis
  • Bilharziasis
• Granuloma- a collection of inflammatory cells (macrophages, lymphocytes, plasma, giant cells, fibroblasts) that fuse into a tiny micro granules, forming a tumor-like mass;
• Infectious (Bacterial: TB, leprosy, syphilis, Parasitic: Bilharziasis, Fungal: Madura foot, histoplasmosis)
• Non-infectious (Silicosis, asbestosis, sarcoidosis)

Explore the complex processes of inflammation, including its aims, causes, and cardinal signs. Discover the differences between acute and chronic inflammation, along with the types and characteristics of acute inflammation. This quiz provides a comprehensive understanding of how the body responds to injury and infection.