Altered Cellular and Tissue Biology Flashcards

Cellular Adaptation

• Reversible response to physiologic (normal) and pathologic (adverse) changes.
• Types:
  • Atrophy: Decrease in cell size.
    • Physiologic (e.g., thymus atrophy in early development).
    • Pathologic (e.g., disuse atrophy from decreased workload).
  • Hypertrophy: Increase in cell size.
    • Physiologic (e.g., muscle enlargement from exercise).
    • Pathologic (e.g., cardiac muscle hypertrophy due to valve disease).
  • Hyperplasia: Increase in number of cells.
    • Physiologic:
      • Compensatory (e.g., organ regeneration).
      • Hormonal (e.g., response to endocrine control).
    • Pathologic: Hormonal (e.g., abnormal proliferation of normal cells).
  • Dysplasia: Abnormal changes in size, shape, and organization of mature cells.
    • May be reversible if stimulus is removed.
    • Can progress to invasive neoplasm if changes penetrate basement membrane.
  • Metaplasia: Reversible replacement of one mature cell type by another.
    • Associated with tissue damage, repair, and regeneration.

Cellular Injury

• Occurs when cells cannot maintain homeostasis.
• Reversible: Cells recover.
• Irreversible: Cells die.
• Mechanisms:
  • Hypoxic Injury: Most common cause; results from ischemia (reduced blood supply) or anoxia (total lack of oxygen).
  • Ischemia-Reperfusion Injury: Cell injury and death caused by restoration of blood flow and oxygen.
    • Mechanisms involve oxidative stress, increased intracellular calcium, inflammation, and complement activation.
  • Free Radicals and Reactive Oxygen Species: Cause oxidative stress, damaging lipids, proteins, DNA, and mitochondria.
  • Chemical or Toxic Injury: Caused by xenobiotics (toxic, mutagenic, carcinogenic chemicals).
    • Examples: Carbon tetrachloride, lead, carbon monoxide, ethanol, mercury, drugs.

Unintentional and Intentional Injuries

• Blunt Force Injuries: Tearing, shearing, or crushing of tissues due to mechanical force.
  • Examples: Motor vehicle accidents, falls, contusions, lacerations, fractures.
• Sharp Force Injuries: Incised, stab, puncture, or chopping wounds.
• Gunshot Wounds
• Asphyxial Injuries: Failure of cells to receive or use oxygen.
  • Examples: Suffocation, strangulation, chemical asphyxiants (carbon monoxide, cyanide), drowning.

Other Injuries

• Infectious Injury: Pathogenicity of microorganisms (invasion, destruction, toxin production).
• Immunologic and Inflammatory Injury: Injury from substances generated during inflammatory response (e.g., histamine, antibodies).

Manifestations of Cellular Injury

• Cellular Accumulations (Infiltrations):
  • Accumulation of normal cellular substances (e.g., water, proteins, lipids).
  • Accumulation of abnormal substances (endogenous or exogenous).
• Mechanisms of Accumulation:
  • Insufficient removal of normal substances.
  • Accumulation of abnormal substances due to defects.
  • Inadequate metabolism of endogenous substances.
  • Harmful exogenous materials.

Cellular Death

• Necrosis: Rapid loss of plasma membrane structure, organelle swelling, mitochondrial dysfunction.
  • Types:
    • Coagulative: Protein denaturation; albumin transformed to opaque state; occurs in infarcts.
    • Liquefactive: Cells digested by hydrolases; tissues become soft and liquefied; triggered by bacterial infection.
    • Caseous: Combination of coagulative and liquefactive necrosis; results from pulmonary tuberculosis.
    • Fatty: Action of lipases; fatty acids combine to create soaps; tissue appears opaque and chalky white; occurs in breast, pancreas, and abdominal organs.
    • Gangrenous: Death of tissue from severe hypoxic injury.
      • Dry: Skin becomes dry and shriveled, brown or black.
      • Wet: Area becomes cold, swollen, and black; may involve gas gangrene (Clostridium).
• Apoptosis: Programmed cellular death; active process; can be physiologic or pathologic.
• Autophagy: Self-destructive survival mechanism where cytoplasmic contents are delivered to lysosomes for degradation.

Aging and Altered Cellular/Tissue Biology

• Aging: Time-dependent loss of structure and function.
• Frailty: Weakness, decreased stamina, and functional decline in older adults, increasing vulnerability to falls, disability, disease, and death.
• Cellular changes proceed slowly and in small increments.

Somatic Death

• Death of the entire body.
• Postmortem changes:
  • Pallor mortis (paleness).
  • Algor mortis (cooling).
  • Rigor mortis (stiffening).
  • Livor mortis (discoloration).
  • Putrefaction (decomposition).
  • Skeletonization.