Introduction to Pathology

Introduction to Pathology

• Pathology is the study of disease.
• "Pathos" means suffering, disease.
• Disease is an abnormal variation of the structure and function of any organ or tissue in the body.

Important Concepts

• The core of pathology encompasses four key aspects:
  • Etiology: the causes of the disease.
  • Pathogenesis: the mechanisms involved in disease development.
  • Morphologic changes: the structural alterations within cells and organs.
  • Clinical significance: the functional consequences of morphologic changes.

Classification

• Human pathology (Autopsy, Biopsy, Cytology)
• Experimental pathology

Position

• A bridging discipline that blends basic science and clinical practice.

Divisions of Pathology

• General pathology: focuses on basic reactions of cells and tissues to abnormal stimuli, covering overall disease response.
• Systemic pathology: describes disease-specific responses on specialized organs and tissues to stimuli.

Cell Injury and Cellular Adaptations

• The foundation of all diseases involves injury to cells.
• Normal cells typically maintain a steady-state, adapting to physiological demands according to their capacity.

Causes of Cell Injury

• Hypoxia: lack of oxygen supply.
• Biological agents: bacteria, viruses, fungi, and parasites.
• Chemical agents: strong alkalis, acids, insecticides, alcohol, narcotics, and air pollutants.
• Physical agents: extreme heat/cold, radiation, mechanical trauma, and electric shock.
• Endogenous toxins: substances produced within the body (uremia, jaundice, diabetic ketosis).
• Immunological reactions: autoimmune diseases.
• Nutritional imbalances: protein-calorie malnutrition, starvation, obesity, diabetes, vitamin deficiencies.
• Genetic abnormalities.

Types of Cell Injury

• Irreversible injury: leads to cell death, consisting of:
  • Necrosis: a form of cell death.
  • Apoptosis: programmed cell death.
• Reversible injury: non-lethal events leading to:
  • Hydropic swelling: excess water accumulation.
  • Fatty change: accumulation of fat in cells.
  • Reduced oxidative phosphorylation: decreased cellular energy (ATP).

Cellular Response to Stress or Noxious Stimuli

• A flowchart showing cell response to stress & injury.
• Initially, a cellular response could be an adaptive process to the stimulus.
• Eventually, injury can result leading to cell death.

Cellular Adaptation

• Cellular adaptations are changes in cells' structure and function, adapting to excessive physiological or pathological stimuli, whilst preserving cell viability.
• Etiologies of cellular adaptation involve:
  • Increased physiological demand.
  • Minor stresses.
  • Reduced demand.
  • Nutritional deficiencies.

Types of Cellular Adaptations

• Hypertrophy: increase in the size of cells, leading to increased tissue/organ size, non-dividing cells.
• Hyperplasia: increase in the number of cells, including physiological (hormonal, compensatory, functional demand) and pathological instances (hormonal stimulation, viral infection, chronic injury).
• Atrophy: shrinkage in the size of cells, leading to decreased tissue/organ size, cells are viable, includes physiological (aging, menopause, post-delivery) and pathological types (disuse, denervation, ischemia, inadequate nutrition, pressure).
• Metaplasia: conversion of one adult cell type to another in response to adverse environmental conditions, with both protective (cytoprotective) and problematic (malignancy) aspects, specific etiologies include irritants, stones, and vitamin A deficiency.

Epithelial Metaplasia

• Columnar to squamous (lungs, cervix, ducts).
• Squamous to columnar (Barrett esophagus).

Explore the fundamentals of pathology, which focuses on the study of disease. Learn about the core concepts such as etiology, pathogenesis, and morphologic changes, as well as the classification and divisions of pathology. This quiz is essential for understanding how diseases affect body structure and function.