Pathophysiological Concepts - Cell Adaptation & Cell Injury

Challenges through Cells Life Span

• Cells are affected by stressors, health changes, and intrinsic/extrinsic factors, altering normal functioning.
• Cells continue functioning despite challenging conditions; however, severe or prolonged stress can injure or destroy them.
• When threatened, cells utilize reserves to adapt or may enter a state of dysfunction, leading to cell death if reserves are inadequate.

Adaptive Cell Changes

• Adaptive changes include atrophy, hypertrophy, hyperplasia, dysplasia, and metaplasia.

Atrophy

• A reversible reduction in cell size caused by:
  • Disuse
  • Insufficient blood flow
  • Malnutrition
  • Denervation
  • Reduced endocrine stimulation

Hypertrophy

• Enlargement of cells due to increased workload.
• Can occur under normal physiological conditions or abnormal pathological conditions.
• An example includes an enlarged heart.

Hyperplasia

• Involves an increase in the number of cells.
• Triggered by:
  • Increased workload
  • Hormonal stimulation
  • Decreased tissue

Dysplasia

• Deranged cell growth leading to abnormal size, shape, and appearance.
• These changes can be adaptive and potentially reversible but may precede cancerous changes.

Metaplasia

• The replacement of one adult cell type with another that can better endure stress or change.
• Typically a response to chronic inflammation or irritation.

Cellular Injury Overview

• Cellular injury disrupts the normal function and structure of cells, leading to disease due to loss of adaptability.
• Injury can be intrinsic (within the body) or extrinsic (from the environment).

Types of Cellular Injury

Toxic Injury

• Caused by both endogenous (internal) and exogenous (external) factors.
• Endogenous Factors:
  • Genetic metabolic errors
  • Gross malformations
  • Hypersensitivity reactions
• Exogenous Factors:
  • Substances such as alcohol, lead, carbon monoxide, cigarette smoke, pesticides, carcinogens, and immunosuppressive drugs.

Deficit Injury

• Occurs due to lack of essential elements like water, oxygen, or nutrients.
• Insufficient maintenance of temperature and waste disposal can lead to cellular dysfunction.
• A single deficiency can precipitate cell disruption or death.

Physical Injury

• Arises from disturbances in cell structure or relationships among organelles.
• Two primary forms:
  • Thermal Injury: Caused by heat, electricity, or radiation.
  • Mechanical Injury: Resulting from trauma or surgical interventions.

Infectious Injury

• Caused by various organisms, including viruses, fungi, protozoa, and bacteria.
• These pathogens compromise cellular integrity by disrupting synthesis and generating mutant cells.
• Example: HIV specifically targets T-cells, integrating its RNA into T-cell DNA, which prevents immune function and leads to proliferation of the virus.