Cell Injury Overview Quiz

Cell Injury Overview

• Cells are constantly exposed to stressors.
• Cells initially adapt to overcome stressful conditions.
• Severe or prolonged stress leads to cell injury.

Intended Learning Objectives

• Identify causes of cell injury.
• Describe cellular adaptation with examples.
• Recall types of cell injury.
• Describe reversible cell injury mechanisms and morphology.
• Define, identify causes, and explain consequences of hypoxic cell injury.
• Describe irreversible cell injury mechanisms.

Causes of Cellular Injury

• Physical agents: Hypoxia, mechanical trauma, burns, radiation, electric shock.
• Chemical agents: Poisons (toxins), insecticides, alcohol, tobacco.
• Infectious agents: Viruses, bacteria, fungi, parasites.
• Immunological reactions: Anaphylaxis, autoimmune diseases.
• Genetic derangements: Abnormal proteins (hemoglobinopathies), abnormal or absent enzymes (storage disorders).

Cellular Adaptation

• Hyperplasia: Increase in cell number, e.g., compensatory hyperplasia of the kidney after nephrectomy.
• Hypertrophy: Increase in cell size, e.g., hypertrophy of the left ventricle due to aortic stenosis or hypertension.
• Atrophy: Decrease in cell number and/or size, e.g., skeletal muscle atrophy after paralysis.
• Metaplasia: Change of one cell type to another cell type of the same category, e.g., change from columnar epithelium to squamous epithelium in the airways due to cigarette smoke.

Types of Cell Injury

• Reversible: Affected cells can recover from the injury.
• Irreversible: Affected cell dies.

Hypoxic Cell Injury

• Definition: Inadequate oxygenation of tissue.
• Causes:
  • Hypoxemia: Decreased oxygen in the plasma.
  • Hemoglobin abnormalities: Anemia.
  • Ischemia: Decreased arterial blood flow to tissues (often due to atherosclerosis).
• Consequences:
  • Decreased ATP synthesis.
  • Impaired Na+/K+-ATPase pump leading to cellular swelling.
  • Shift to anaerobic glycolysis leading to lactic acid accumulation, decreased intracellular pH, protein denaturation, and clumping of nuclear chromatin.
  • Ribosomal detachment leading to decreased protein synthesis and lipid accumulation (fatty change).

Morphology of Reversible Cell Injury

• Cellular swelling: First manifestation of cell injury; ionic and fluid homeostasis fail.
• Fatty change: Lipid vacuoles within the cytoplasm (seen in the kidney, heart, and liver).

Irreversible Cell Injury

• Mechanism: Persistent or severe injury (hypoxia or anoxia) pushes the cell to the "point of no return" making the injury irreversible.
• Hallmark: Severe mitochondrial damage.
• Mechanism of Mitochondrial Damage: Marked reduction in ATP production leads to mitochondrial damage, high conductance channels (MPT channels) formation, releasing cytochrome c into the cytosol, triggering cell death.

Test your knowledge on cell injury, adaptation, and types of cellular damage. This quiz covers various causes of cell injury, mechanisms of reversible and irreversible cell injury, and specific conditions like hypoxia. Challenge yourself to understand how cells respond to stressors and the consequences of cellular injuries.