SP 128: Pathology of Illness

• What is Pathology

  • The study of the structural, biochemical, and functional changes in cells, tissues, and organs that underlie disease
  • Explains the whys of the signs and symptoms of a patients
  • Provides rational basis for clinical care and therapy
• 4 Aspects of Disease

  1. Etiology
  2. Pathogenesis
  3. Morphologic Changes
  4. Clinical Manifestations
• Etiology

  • Initiating cause of a disease
  • Genetic (mutation)
  • Environmental (infections, nutrition, chemical, and physical)
  • Multifactorial (Genetic and Environmental)
• Pathogenesis

  • Sequence of molecular, biochemical, and cellular events that lead to development of disease
• Pathogenesis is how underlying etiology produce morphologic and clinical manifestations of the disease
• Morphologic Changes

  • Structural alterations in cells or tissues that are characteristic of a disease and hence diagnosis of an etiological process
• Clinical Manifestations are the signs and symptoms of disease
• Causes of Cell Injury

  • Oxygen Deprivation
  • Physical Agents
  • Chemical Agents and Drugs
  • Infectious Agents
  • Immunologic Reactions
  • Genetic Abnormalities
  • Nutritional Imbalances
• Many times the cause of cell injury is not singular but it's a combination of various causes
• Oxygen Deprivation

  • Hypoxia
  • Ischemia
• Physical Agents

  • Traumatic Injury
  • Extreme temperatures (frostbite, burns, electric injuries)
• Infectious Agents

  • COVID-19
  • Mutation
• Further progressive injury to (no return) cell death
• Cell death can occur as an essential process in embryogenesis (development of organs) and maintenance of homeostasis to adulthood
• Cell death is normal as it removes damaged and unneeded & aged cells
• Cellular Aging

  • Individual age because their cells age
  • Progressive decline in cellular function and viability
  • Reduced capacity to divide cells, repair DNA damage, defective protein homeostasis
  • Combination of accumulating cellular damage
• Pattern of Tissue Necrosis

  • Coagulative
  • Liquefactive
  • Gangrenous
  • Fibrinoid
  • Caseous
  • Fat
• Necrosis (Accidental Damage)

  • Cell Size: Enlarged (swelling)
  • Nucleus: Pyknosis
• Necrosis (Accidental cell death)

  • Enlarged (Swelling)
  • Nucleus
  • Pyknosis
  • Karyorrhexis
  • karyolysis
• Necrosis (Accidental cell death)

  • Disrupted Plasma membrane
  • Enzymatic digestion (may leak out of cell)
  • Frequent adjacent inflammation
• • Necrosis is usually pathologic (culmination of irreversible cell injury)
  • Necrosis is caused by injuries causing a collateral damage
• Apoptosis (regulated cell death)

  • Reduced (shrinking)
  • Nucleus
  • Fragmentation into nucleosome-size fragments
• Apoptosis (regulated cell death)

  • Intact plasma membrane
  • Intact Cellular contents
  • None adjacent inflammation
• • Apoptosis is often physiologic, but may be pathologic
  • Apoptosis kills cells with surgical precision
• Tissue Necrosis: lots of tissue are dead
• Coagulative Necrosis

  • dead tissue is preserved for few days
  • caused by Ischemia which leads to infarct
  • seen in all body organs except the brain
• infarct: localized coagulative area
• Liquefactive

  • dead tissue is not preserved
  • digestions of cells transforms in viscous liquid (pus)
  • seen in brain and focal bacterial infections
  • often yellow because of leukocyte
• Gangrenous Necrosis

  • coagulative necrosis of the limb or lower extremities that loss blood supply
  • considered coagulative necrosis involving multiple tissue planes
• Wet Gangrene (Diabetic Foot)

  • if superimposed bacterial infection leading to liquefactive necrosis
• Fibrinoid Necrosis

  • vascular damage from immune system reactions
  • antigen-antibody complexes deposit in the walls of arteries
  • leakage of plasma protein out of vessels
  • bright pink and amorphous
• Caseous Necrosis

  • Associated with tuberculous infection
  • cheese-like, friable
  • white appearance on gross appearance
• Fat Necrosis

  • focal areas of fat destruction
  • results from release of activated pancreatic lipases into the substance of the pancreas and peritoneal cavity
  • visible chalky white areas (fatty acids and calcium)
• Coagulative Necrosis

  
• Coagulative Necrosis in Microscope

  
• Liquefactive Necrosis

  
• Wet Gangrene (Diabetic Foot)

  
• Fibrinoid Necrosis

  
• Caseous Necrosis

  
• Fat Necrosis