1 Introduction to Histopathology

• Pathology is devoted to the study of structural, biochemical, and functional changes in cells, tissues, and organs that underlie disease
• Pathology literally translates to the study of suffering.
• Etiology or cause is the origin of the disease
• Pathogenesis is the exposure of the tissue or cells to an injurious agents (mechanism)
• Morphologic changes refers to the structural alteration in cells/tissues (induce in the cells and organs of the body)
• Signs are the "objective” evidence of the disease [e.g, physical observation, measurable indicator]
• Symptoms are the “subjective” evidence of the disease [e.g., pain, itchiness, dizziness, fatigue, and tinnitus]
• Tinnitus is the abnormal ringing of the ears
• Rudolf Carl Virchow is the father of Modern Pathology.
• Aulus Cornelius Celsus is the one who described the first 4 cardinal signs.
• FIVE CARDINAL SIGNS OF INFLAMMATION:

  • Rubor (redness)
  • Calor (heat)
  • Tumor (swelling)
  • Dolor (pain)
  • Functio laesa (loss of function)
• Rubor is the arteriolar vesicular dilation because of blood flow due to injury

  • ↑ concentration RBC
  • slow blood flow
• Stack RBC causes redness in rubor
• Calor is due to the transfer of internal heat to the surface or site of injury, brought about by increased blood content

  • blood → heat (end product)
  • redness automatic w/ Heat
• Tumor is the increased capillary permeability, allowing the extravasation of blood fluid causing localized edema accompanied by escape of blood cells into the injured area.
• Increased capillary permeability allows excrete of fluid/gases thru cell membrane, which causes edema
• Edema is the excess fluid on tissue
• Increased extravasation causes hydrostatic pressure within the dilated blood vessels
• Dolor is the direct damage to the nerve ending; there is pressure to the sensory nerves
• An example of dolor is Arthritis
• Functio laesa is the pain interference with nerve supply and destruction of the functioning units; there is a limitation of movement due to swelling.
• Functio laesa can be an adaptive mechanism by the body to protect the injured area from further damage.
• In Acute inflammation:

  • onset is fast which can last minutes to hours,
  • cellular infiltrate is mainly neutrophils,
  • tissue injury is usually mild and self limited, and
  • local/systematic signs are prominent
• In Chronic inflammation:

  • onset is slow which can take days,
  • cellular infiltrate are mononuclear cells,
  • tissue injury is often severe and progressive, and
  • local/systematic signs are less
• An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation.
• Serous Inflammation is a type of exudate that is an extensive outpouring of watery, low-protein fluid from either the blood serum or secretions of serosal mesothelial cells [e.g., Pulmonary TB]
• Fibrinous Inflammation is a type of exudate that is an exudation of large amount of fibrinogen and precipitation of fibrin masses [e.g., Diphtheria, rheumatoid pericarditis, Early stage of pneumonia]
• Catarrhal Inflammation is a type of exudate that is an hypersection of mucosa with degenerative changes in epithelium [e.g., rhinitis, gastritis, colitis]
• Hemorrhagic is a type of exudate that is an admixture of blood = blood + exudates [e.g., Bacterial infections & other infections]
• Purulent/Suppurative is a type of exudate that produces large amount of pus or purulent exudates.
• Pus is a creamy fluid component of PMNs & necrotic tissue debris
• Retrogressive changes are when organs or tissues are smaller than normal
• Progressive changes are when organs or tissues are larger than normal
• Degenerative changes are when there is an aberrations of cellular growth patterns
• Developmental defects in retrogressive changes (AAHA):

  • Aplasia
  • Agenesia
  • Hypoplasia
  • Atresia
• Atrophy is the acquired decrease in size of a normally developed/mature tissues or organs resulting from reduction in cell size or decrease in total number of cells or both
• Physiological atrophy is natural, associated with thymus and sex organs
• Pathologic atrophy is the consequence of a disease
• Hypertrophy is the increase in size of tissues/organs due to increase in size of individual cells
• Hyperplasia is the increase in size of tissues/organs due to the increase in the number of individual cells