Pathology

Key Terminology in Pathology

Aetiology

  • Definition: The study of causes of disease.
  • Example: The aetiology of a condition could be due to bacteria, viruses, genetic defects, etc.

Clinical Manifestations

  • Definition: How morphological changes of the disease produce clinical effects and investigative abnormalities.
  • Symptoms:
    • Patient's subjective experience of illness.
    • Examples: nausea, light-headedness.
  • Signs:
    • Objective and observable evidence of disease.
    • Examples: tachycardia, fever.

Disease Outcomes

  • Complications:
    • Lesions which develop as a direct consequence of another lesion.
  • Prognosis:
    • The likely outcome of a disease in an individual.
  • Natural History:
    • The course of the untreated disease.

Epidemiology

  • Definition: Patterns of disease within a population including frequency, gender, race, geographic location, and socioeconomic status.

Injury

  • Definition: Any adverse influence that prevents a cell from maintaining homeostasis.

Morphology

  • Definition: Lesions that may be microscopic or macroscopic changes in structure observed in cells or tissue.

Pathogenesis

  • Definition: The mechanism by which a disease induces changes in bodily structure or function.

Cellular Responses to Injury

Factors Influencing Effects of Injury

  1. Nature of the injurious agent.
  2. Severity and duration of injury.
  3. Nature of target cells.

Cellular Level Responses

  • Injured target cells may either:
    • Be damaged.
    • Adapt through changes in growth and/or differentiation.
  • Evidence of injury might include:
    • Biochemical lesion
    • Morphological change
    • Functional abnormality

Underlying Biochemical Lesions

  • Inhibition of aerobic respiration
  • Loss of membrane integrity
  • Alterations in structural or enzymatic proteins
  • Interference with DNA synthesis or repair

Tissue Level Responses

  • Often characterized by the inflammatory response initiated by the injurious agent, which may influence resolution or progression of inflammation.
  • Hyperplasia:
    • Increase in organ size due to an increase in the number of cells.
    • Example: Smooth muscle growth during pregnancy.
  • Metaplasia:
    • Conversion of one differentiated cell type into another.
    • Example: Squamous metaplasia in a smoker's trachea.
  • Atrophy:
    • Decrease in size of an organ or tissue that was previously normal.
    • Can be reversible or irreversible.
    • Example: Ischemic atrophy of kidney due to renal artery stenosis.

Definitions of Cell Death

Apoptosis

  • Definition: A form of individual cell death observed in physiological turnover characterized by:
    • Nuclear condensation and fragmentation.
    • Cells shrink and fragment into apoptotic bodies that are phagocytosed.

Necrosis

  • Definition: Death of cells in a localized area, recognized by autolytic changes post cell death:
    • Cells lose functional control and burst, releasing cytotoxic materials.

Dysplasia

  • Definition: Atypical cell differentiation often found in neoplasms or pre-neoplastic lesions.
  • Characterized by enlargement of an organ or tissue due to proliferation of abnormal cells.

Neoplasia

  • Definition: Abnormal tissue growth that is uncoordinated and persists despite cessation of stimuli.
  • Described as new, uncontrolled growth of cells that is not physiologically regulated.

Additional Notes

Pathophysiology of Hypoxia

  • Hypoxia leads to depletion of ATP production, critical for cell function.
  • Results in impaired function of the ATP-dependent sodium pump, causing a sodium influx and water movement into the cell, leading to hydropic change, a form of swelling.
  • This change is reversible if hypoxia is alleviated before irreparable damage occurs.

Fatty Change in the Liver

  • Can occur due to excessive calorie intake or starvation.
  • Starvation increases circulating free fatty acids, similarly to excessive intake, leading to:
    • Conversion of fatty acids to triglycerides for storage in hepatocytes.