Module 1

• Traditional Divisions of Pathology:

  • General Pathology: concerned with common reactions of cells and tissue to injurious stimuli, not tissue-specific
  • Systemic Pathology: examines alterations and underlying mechanisms in organ-specific diseases
• 4 Aspects of the disease process in pathology:

  1. Etiology: cause of the disease (genetic or acquired)

  2. Pathogenesis: sequence of biochemical and molecular events following exposure to injurious agents

  3. Morphologic changes: structural alterations induced in cells and organs, used for diagnostic purposes

  4. Clinical Manifestations: functional consequences of the disease, including symptoms and signs
• Basic Terms in Pathology:

  • Disease: a pathophysiological response to internal and external factors, leading to abnormalities in systemic functions
  • Disorder: a disruption of normal body functions
  • Syndrome: a disease or disorder with multiple identifying features or symptoms
• Infectious spread involves affecting or contaminating someone with pathogenic microorganisms
• Contagious spread occurs through direct bodily contact with an infected person, their discharges, or contaminated objects or surfaces
• All communicable diseases are infectious, but not all are contagious; infectious diseases are contagious when they spread through direct bodily contact with an infected person or their discharges
• Malaria is infectious but not contagious because a vector is needed to transmit the infection
• Tetanus is infectious but not contagious because it is not spread through direct bodily contact
• COVID-19 is both infectious and contagious as it can spread directly from person to person and from contaminated objects
• Adaptations in response to environmental changes include hypertrophy, hyperplasia, atrophy, and metaplasia
• Hypertrophy refers to an increase in cell size, often due to increased synthesis of structural components
• Physiologic hypertrophy can result from increased functional demand or hormonal stimulation, like uterine enlargement during pregnancy
• Pathologic hypertrophy can occur due to chronic hemodynamic overload, leading to maladaptive changes in cells
• Hyperplasia is an increase in the number of cells in response to a stimulus, often occurring with hypertrophy and only in cells capable of division
• Physiologic hyperplasia can be due to hormonal or growth factor actions, like glandular proliferation in the breast during puberty
• Pathologic hyperplasia can result from excessive hormone or growth factor actions, potentially leading to cancerous proliferations
• Atrophy is a decrease in cell size due to factors like disuse, lack of stimulation, aging, or diminished blood supply
• Physiologic atrophy can occur during normal development, like the decrease in the uterus after childbirth
• Pathologic atrophy can be local or generalized, caused by factors like disuse, loss of innervation, diminished blood supply, inadequate nutrition, or loss of endocrine stimulation
• Metaplasia is the replacement of one differentiated tissue by another, like squamous metaplasia in the cervix or respiratory epithelium
• Cell injury occurs when cells are exposed to injurious agents or stress, deprived of essential nutrients, or compromised by mutations affecting essential cellular constituents
• Cell injury is reversible up to a point, but if the injurious stimulus is persistent or severe, the cell suffers irreversible injury and cell death may ensue
• The removal of damaged, unneeded, and aged cells through cell death is a normal and essential process in embryogenesis, organ development, and homeostasis maintenance into adulthood
• There are two pathways of cell death: necrosis and apoptosis; nutrient deprivation triggers an adaptive cellular response called autophagy that may also culminate in cell death
• Causes of cell injury include hypoxia, free radical injury, chemical cell injury, infectious agents, immune system reactions, and genetic abnormalities
• Hypoxic cell injury is caused by oxygen deprivation, leading to reduced aerobic oxidative respiration; depending on the severity, cells may adapt, undergo injury, or die
• Free radicals, molecules with unpaired electrons, can cause cell injury; mechanisms that generate free radicals include normal metabolism, oxygen toxicity, ionizing radiation, and more
• Chemical agents and drugs may produce cell injury; liver cell membrane damage can be induced by carbon tetrachloride (CCl4), leading to lipid peroxidation and cellular damage
• Infectious agents like viruses, bacteria, fungi, and parasites can cause cell injury through diverse mechanisms; immune reactions to self-antigens or external agents are also significant causes of cell and tissue injury
• Genetic abnormalities may cause cell injury due to genetic aberrations leading to clinical phenotypes like congenital malformations, deficient protein function, or accumulation of damaged DNA, triggering cell death when beyond repair
• DNA sequence variants can influence cell susceptibility to injury by chemicals and environmental insults
• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver

  
• Schaffer and Emerson's 1964 study on attachment:

  • Aim: identify stages of attachment / find a pattern in the development of an attachment between infants and parents
  • Participants: 60 babies from Glasgow
  • Procedure: analysed interactions between infants and carers
  • Findings: babies of parents/carers with 'sensitive responsiveness' were more likely to have formed an attachment
• Freud's superego is the moral component of the psyche, representing internalized societal values and standards
• Reversible cell injury:

  • Basic alterations occur at the molecular and biochemical level
  • Time lag between stress and morphologic changes of cell injury
  • Morphology under light microscope: cellular swelling, appearance of small clear vacuoles in the cytoplasm, increased eosinophilic staining
  • Fatty change occurs in hypoxic injury and various forms of toxic or metabolic injury

  
• Reversible cell injury is due to decreased ATP generation, loss of cell membrane integrity, defects in protein synthesis, cytoskeletal damage, and DNA damage
• Morphology of reversible cell injury under the light microscope:

  • Cellular swelling due to failure of energy-dependent ion pumps in the plasma membrane
  • Appearance of small clear vacuoles in the cytoplasm (hydropic change or vacuolar degeneration)
  • Increased eosinophilic staining
• Cell death has two contrasting morphologic patterns: necrosis and apoptosis
• Necrosis:

  • Morphology results from denaturation of intracellular proteins and enzymatic digestion of the lethally injured cell
  • Enzymes digesting the cell cause inflammation of surrounding tissue
  • Patterns of necrosis include coagulative, liquefactive, caseous, gangrenous, fibrinoid, and fat necrosis
• Apoptosis is a programmed cell death mechanism that eliminates cells that are no longer needed or are a threat to the organism