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What is pathology

  • A scientific study of causes and effects of disease, ie, the scientific basis of medical practice
    • Egs:
      • how diseases develop through genes, molecules, cells, tissues, organs
      • the disease process including what happens to the body
      • effects of disease - symptoms and complications
  • Academic and Service pathology
    • Academic: teaching/research
    • Service: anatomical, chemical, microbiological, haematological, immunological, genetic
      • “broad specialty”
  • Teaching of pathology:
    • General: disease processes and mechanisms
    • Systemic: organ based study of disease
    • Clinical pathological correlation: relation of clinical to diseases and their causes
  • Tree of medical knowledge:
    • Roots are anatomy, biochemistry, physiology
    • Trunk is pathology
    • Branches are medicine/surgery
    • Leaves are subspecialties

Concepts of disease

  • Historical: Hippocrates
    • Disease was an imbalance of the humours in the body
      • Humours: blood (confidence), phlegm (relaxation), black bile (melancholy), yellow bile (anger)
      • Beliefs maintained until the 19th C with the invention of the microscope
    • Pasteur, Lister found illness was caused by the proliferation of microbes
    • Virchow – the father of modern pathology
      • Described disease as caused by microbes etc
  • Current: molecular view of disease

Definitions

  • Lesions – an abnormality in the structure or function of part of the body caused by injury or disease
    • Caused by a pathological process such as:
      • Inflammation (healing and repair)
      • Thrombosis, embolism, infarction
      • Neoplasm (tumours) – disordered growth
  • Disease is investigated in various ways:
    • Epidemiology: patterns of disease in the population
      • Includes prevalence in gender, race, socio-economic groups
    • Aetiology: cause
      • Congenital (born with)
      • Acquired: caused by:
        • Chemicals (acid, alkali, drugs, toxins)
        • Hypoxia (lack of oxygen)
        • Infection (virus, bacteria, fungi)
        • Nutritional deficiency (hormonal, metabolic disorders)
        • Physical (trauma, heat, cold, radiation)
        • Immunological (autoimmunity)
        • Genetic
      • --> CHINPIG
      • Note: idiopathic, cryptogenic, essential are saying “we have no idea”
    • Pathogenesis: how the cause manifests and proceeds=
    • Morphology: changes
      • Macroscopic or microscopic (histopathology)
        • Focal (often large and single) – single point of infection
        • Multifocal (often small and multiple) – several points of infection
        • Diffuse – whole tissue infected
    • Clinical manifestations
      • Signs – objective detectable and observable evidence of disease
      • Symptoms – subjective experience of illness/disease
      • Investigations
        • Imaging – Xray, CT, Ultrasound
        • Haematology – full blood count
        • Biochemistry – electrolytes, renal function
        • Microbiology – blood culture, septum culture
        • Immunology - ELISA
    • Disease outcomes
      • Complications: lesions caused by lesions
      • Prognosis: likely outcome of individual
      • Natural history: course of untreated disease

The pathology glossary