Pathology Lecture: Causes of Cell Injury

Introduction

• Pathology: Study of diseases, their nature, causes, risk factors, and precipitating factors.
• Biopsy: Gold standard for studying tissues.
  • Gross examination: Inspecting organs with the naked eye.
  • Microscopic examination: Inspecting tissues under a microscope.

Cell Injury vs. Cell Death

• Cell Injury: Reversible process
• Cell Death: Irreversible, no recovery

Causes of Cell Injury (Irreversible)

1. Hypoxia (low oxygen) / Anoxia (no oxygen)
   • Lung disease (e.g., Chronic Obstructive Pulmonary Disease)
   • Heart disease (e.g., Myocardial Infarction)
2. Chemical Agents
   • Polycyclic hydrocarbons (e.g., cigarette smoking)
   • Alcohols (e.g., methanol, ethanol)
   • Medications (e.g., acetaminophen)
   • Heavy metals (e.g., mercury, lead, arsenic)
3. Physical Agents
   • Radiation, frostbite, burns
4. Free Radicals
   • Reactive Oxygen Species (e.g., iron overload conditions like hemochromatosis)
5. Inflammatory Causes
   • Examples: abscess, cellulitis, folliculitis, sepsis
6. Immunological Causes
   • Autoimmune diseases (e.g., lupus, rheumatoid arthritis, scleroderma)
7. Microbiological Causes
   • Bacteria, viruses, fungi, parasites
8. Genetic or Metabolic Causes
   • Examples: phenylketonuria, diabetes mellitus
9. Nutritional Deficiencies
   • Protein energy malnutrition (e.g., kwashiorkor)
   • Total energy malnutrition (e.g., marasmus)
10. Intracellular Accumulation of Gunk
    • Exogenous (e.g., lead)
    • Endogenous (e.g., triglycerides, bilirubin)
11. Aging (Senescence)
    • Decreased cell replication

Hypoxia and Anoxia Examples

• Cyanosis: Blue baby syndrome
  • Lung issue: Treat with oxygen
  • Heart issue: Oxygen treatment ineffective
  • Cyanotic congenital heart diseases (all start with 'T')

Chemical Factors Breakdown

• Methanol: Leads to formic acid, toxic to the eye
• Ethanol: Converts to acetic acid, normal doses not toxic, high doses cause toxicity
• Acetaminophen: Metabolized to NAPQI, depletes glutathione, treat with N-acetylcysteine
• Heavy Metals: Damage to kidneys (e.g., iodine contrast agents, many antibiotics, ethylene glycol)

Free Radicals and Heavy Metals

• Iron and Copper: Cause free radical damage via Fenton reaction
  • Bound to transferrin (blood) and ferritin (tissue) to prevent free radical formation

Microbiological Causes of Cell Injury

• Microbes: Bacteria, fungi, viruses, parasites
• Gram Stain: Differentiates bacteria
  • Gram-positive: Thick peptidoglycan wall (stain purple)
  • Gram-negative: Thin peptidoglycan wall (stain pink)
  • Catalase and coagulase tests for further differentiation (e.g., Staphylococcus vs. Streptococcus)

Genetic Causes: Phenylketonuria (PKU)

• Deficiency in phenylalanine hydroxylase
• Symptoms: Strange behavior, rat-like smell, lighter skin tone, low birth weight, low head circumference
• Treatment: Diet rich in tyrosine, poor in phenylalanine
• Example: Patient catches up with peers after proper diet

Nutritional Deficiencies

• Kwashiorkor: Protein deficiency
  • Low protein causes low oncotic pressure leading to edema
  • Examples of other causes: liver disease, burns, gut absorption issues, kidney issues
• Marasmus: Total energy malnutrition leading to severe wasting

Conclusion

• Causes of cell injury are numerous and varied
• Cell injury is reversible but must be addressed promptly
• Further learning opportunities and resources available on the Medicosis website

Note: For in-depth understanding, review specific conditions and treatments for cell injury causes.