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Key Terms

• Nonspecific defense: General mechanisms defending the body.
• Cell-mediated immunity: Immune response involving T-cells.
• Inflammation: Protective response to injury or infection.
• Bradykinin: A peptide that causes blood vessels to dilate and increases permeability.
• Exudate: Fluid that leaks out of blood vessels into surrounding tissues during inflammation.
• Resolution: Return to normal tissue after inflammation.
• Regeneration: Replacement of damaged tissue with functional cells.
• Replacement: Replacement of functional tissue with non-functional scar tissue.
• Healing by first intention: Minimal tissue damage leading to small scars.
• Healing by second intention: More severe damage and larger scars.
• Deep partial-thickness burn: Affects deeper skin layers.
• Full-thickness burn: Extensively damages all skin layers and underlying tissues.

Review of Body Defenses

• First Line of Defense:

  • Nonspecific mechanisms, including:
  • Mechanical/Chemical Barriers: Unbroken skin and mucous membranes.
  • Secretions: Tears and gastric juices.

• Second Line of Defense:

  • Also nonspecific and includes:
  • Phagocytosis: Engulfing of pathogens.
  • Inflammation: Localized response to injury.
  • Interferons: Proteins that interfere with viral replication.

• Third Line of Defense:

  • Specific mechanisms:
  • Antibodies: Produced against specific antigens.
  • Cell-Mediated Immunity: Involves T-cells and other immune cells.

Physiology of Inflammation

• Definition: Inflammation is a protective response, is not synonymous with infection but can be caused by it.
• Etiology: Causes include physical injury, chemical damage, infections, allergies, temperature extremes, ischemia, and foreign bodies.
• Signs and Symptoms: Serve as indicators of underlying issues.

Steps of Inflammation

1. Injury: Triggers bradykinin release from damaged cells.
2. Pain: Bradykinin stimulates pain receptors, leading to histamine release.
3. Vasodilation: Caused by bradykinin and histamine, increasing blood flow.
4. Phagocytosis: Neutrophils and macrophages engulf pathogens.

Acute Inflammation

• Local Effects:
  • Redness, warmth, swelling (edema), pain, potential loss of function.
• Systemic Effects:
  • Mild fever (pyrexia), headache, malaise, fatigue, anorexia.
• Complications:
  1. Infection: Inflammatory exudate fosters microbial growth.
  2. Skeletal Muscle Spasm: Pain-induced contractions.

Exudate

• Types of Exudate:
  A. Serous: Watery fluid with proteins and white blood cells.
  B. Fibrinous: Thick, sticky with high fibrin content.
  C. Purulent: Thick, yellow-green with leukocytes and debris.

Chronic Inflammation

• Occurs following acute inflammation; fewer exudate but more immune cells (lymphocytes, macrophages, fibroblasts).
• Complications:
  1. Deep Ulceration: Tissue necrosis due to persistent inflammation.
  2. Granulomas: Form around foreign materials.
  3. Fibrosis: Excess scar tissue formation.

Healing Types

1. Resolution: Minimal damage (e.g., mild sunburn).
2. Regeneration: Damaged tissue replaced with similar cells (e.g., epithelial cells).
3. Replacement: Functional tissue replaced with non-functional scar tissue (e.g., in nervous system).

Healing Processes

• Healing by First Intention: Clean wounds, minimal scarring.
• Healing by Second Intention: Severe injury, larger scars.

Scar Formation Complications

1. Loss of Function: Due to loss of normal cells.
2. Contractures and Obstructions: Restricted movement due to joint deformity.
3. Adhesions: Scar tissue connecting separated body parts.
4. Hypertrophic Scars: Overgrowth of scar tissue.
5. Ulceration: Impaired blood supply leading to further breakdown.

Burns

• Causes: Heat, chemicals, electricity, radiation, friction.
• Classification:
  A. Superficial Partial-Thickness (First-Degree): Affects epidermis, heals without scarring.
  B. Deep Partial-Thickness (Second-Degree): Involves epidermis and dermis, painful and blistered.
  C. Full-Thickness (Third & Fourth-Degree): Destroys all skin layers, requires grafting.

Healing of Burns

• Long process requiring clean wound management to prevent infections.
• Physiotherapy and surgery may be necessary to manage scar tissue.