Pathology of Inflammation: Acute Inflammation

Pathology of Inflammation (Cont.)

• Topic: Morphology of Acute Inflammation
• Cardinal signs of inflammation:
  • Heat
  • Redness
  • Swelling
  • Pain
  • Loss of function
  • Redness due to vasodilation (VD).
  • Hotness due to VD and increased blood flow.
  • Swelling due to inflammatory exudate.
  • Pain due to exudate pressure on sensory nerves and release of bradykinin.
  • Loss of function due to pain and tissue damage.

Microscopic Picture of Acute Inflammation

• Necrotic damaged tissues and degenerated cells.
• Arterioles, venules, and capillaries are dilated and filled with blood.
• Fluid exudate observed by separation of tissues and pale staining of its fibers plus fibrin.
• Cellular exudate mainly neutrophils (24-48 hours) and macrophages (after 48 hours).

General (Systemic) Reactions of Acute Inflammation

• Fever (pyrexia): caused by the release of IL-1 and TNF from bacteria or leukocytes. It affects the heat-regulating center in the brain, disrupting optimal temperature for bacteria but harming body tissues.
• Leukocytosis: increased leukocyte count due to bone marrow stimulation by IL-1 and TNF.
• Loss of appetite and weight: due to increased catabolism and toxins.

Types of Acute Inflammation

• Acute suppurative inflammation:

  • Associated with pus formation.
  • Most severe form of acute inflammation.
  • Caused by strong pyogenic bacteria (e.g., Staphylococcus aureus, Streptococcus haemolyticus).

• Mechanism of pus formation:

  1. Strong pyogenic bacteria cause marked necrosis with excess chemical mediators.
  2. Large numbers of neutrophils are attracted but die due to high bacterial virulence.
  3. Dead neutrophils (pus cells) release enzymes, liquifying necrotic tissue and fibrin.
  4. Liquified material mixed with pus cells and fluid exudate forms pus.

• Types of Localized Acute Suppurative Inflammation:

  • Abscess: irregular cavity containing pus, common in subcutaneous tissues.
  • Furuncle (boil): small abscess related to hair follicles.
  • Carbuncle: multiple communicating suppurative foci in skin and subcutaneous fat that discharge pus through multiple openings, common in diabetics.

• Types of Diffuse Acute Suppurative Inflammation:

  • Cellulitis: An example.
  • Suppurative appendicitis: Another example

Types of Acute Non-Suppurative Inflammation

• Haemorrhagic inflammation: excess red blood cells (RBCs) in exudate due to vascular damage (e.g., meningococcal infection).
• Serous inflammation: watery exudate, poor in fibrin (e.g., blisters after burns, herpes simplex).
• Serofibrinous inflammation: characterized by excess fluid exudate rich in fibrin, affecting serous membranes (e.g., pleura, peritoneum, pericardium).
• Catarrhal inflammation: excess mucus secretion affects mucous membranes (e.g., common cold).
• Allergic inflammation: characterized by fluid exudate rich in eosinophils (e.g., bronchial asthma).
• Pseudomembranous inflammation: acute non-suppurative inflammation of the mucous membranes characterized by formation of a false membrane (e.g., diphtheria, bacillary dysentery).
• Necrotizing inflammation: characterized by extensive necrosis (e.g., oral mucosa in malnourished children).

Explore the morphology and cardinal signs of acute inflammation in this quiz. Learn about the microscopic features and systemic reactions, including fever and various cellular responses. You'll gain a deeper understanding of the processes underlying acute inflammatory reactions.