Untitled Quiz

Pathology: Study of Disease

• Pathology is the scientific study of disease, focusing on how healthy tissues and organs change in a sick individual.
• It is a foundational subject within the medical field, providing understanding of disease processes.

Scope of Pathology

• Clinical Pathology: The study of disease in living individuals.
• Experimental Pathology: The study of disease in laboratory settings.
• Molecular Pathology: Study of disease at the level of molecules.
• Forensic Pathology: The study of disease in relation to legal matters.
• Subdivisions: Histopathology, cytopathology, hematology, microbiology, immunology, chemical pathology, genetic pathology, toxicology, and forensic pathology.

General Pathology vs. Systemic Pathology

• General Pathology: Focuses on common cellular changes that occur across all tissue types. This includes inflammation, cancer and aging.
• Systemic Pathology: Focuses on disease-specific changes within individual organ systems. Examples include goiter, pneumonia, and breast cancer.
• Lesion: An abnormal structural change in the body caused by an irritant.

Pathologist Role

• A pathologist can be a medical doctor (MD) specializing in pathology or a doctor with a doctorate degree (PhD) trained for lab procedures.
• They identify, name and interpret lesions found in tissue samples, ultimately aiming to reach a diagnosis.

Why Clinicians Need Pathology

• The foundation for diagnosing, treating, preventing and controlling disease lies in understanding its characteristics.
• The ability to identify lesions and their causes within the body (either living or deceased), as well as understanding their pathogenesis, is crucial for proper medical decision-making.

Understanding the Disease

• Etiology - The cause of a disease.
  • Predisposing Factors: Contributing factors that influence the development of a disease.
  • Exciting Factor: The immediate trigger for the disease.
• Etiology Causes
  • Environmental Agents: Physical, chemical, nutritional, infectious, immunological, psychological
  • Genetic Factors: Age, genes
  • Multifactorial: Diseases caused by multiple factors (e.g., Diabetes, Hypertension, Cancer)
• Pathogenesis - The mechanism by which the causative agent produces changes in the tissues.
• Pathological Picture - The observed characteristics of a disease.
  • Gross Picture (Macroscopic): Changes evident through naked-eye examination.
  • Microscopical Picture (Histopathology): Changes observed under a microscope.
  • Advanced Techniques: Electron microscopy, immunohistochemistry, cytogenetics, molecular studies.
• Prognosis - The anticipated outcome of a disease, influenced by pathogenesis and the ability to visualize the disease process.
• Fate - The ultimate outcome of the disease, either cure or death.
• Complications - Additional pathological changes that occur during or after the usual course of the disease.

Cell Injury and Cell Death

• Cell Injury: Any biochemical or structural alteration that impairs normal cell function.
• Reversible Cell Injury (Cell Swelling): Early stage of injury, often marked by swelling of cells.
• Irreversible Cell Injury (Cell Death): The point at which cell damage becomes permanent and leads to cell destruction.
  • Apoptosis (Programmed Cell Death): Regulated process of cell death, serves to eliminate damaged or unwanted cells with minimal host response.
  • Necrosis (Accidental Cell Death): Uncontrolled cell death caused by factors like injury.

Causes of Cell Injury and Death

• Oxygen Deprivation (Hypoxia): Lack of oxygen, interferes with cellular energy production.
• Deprivation of Essential Nutrients: Lack of water, food molecules, negatively impacts cell function.
• Chemical Agents: Chemicals can damage cell membranes or interfere with metabolic processes.
• Infectious Agents: Pathogens can invade and disrupt cellular functions.
• Immunologic Reactions: Immune responses, while protective, can sometimes damage cells.
• Genetic Disorders (Congenital Malformations): Inherited genetic defects can lead to cell dysfunction.
• Physical Agents: Trauma, extreme temperatures, and radiation can cause cell injury.
• Free Radicals: Unstable molecules with a single unpaired electron that can damage cell components.
• Aging: Over time, cells accumulate damage that can contribute to cell death.

Hypoxic Cell Injury

• Acute Cellular Swelling: An initial response to hypoxia, characterized by cells taking in water and swelling.
• Mechanism: Hypoxia damages mitochondria, disrupting ion balance. The cell loses potassium and accumulates sodium, leading to water influx and swelling.

Cell Injury Induced By Chemicals

• Mechanism:
  • Chemicals can bind directly to critical cellular components, damaging cell membranes or disrupting energy production.
  • Chemicals can be transformed into more reactive metabolites that generate free radicals.

Free Radicals and Cell Damage

• Free Radicals: Highly reactive molecules with an unpaired electron, making them unstable and prone to reacting with other molecules.
• Types: Superoxide (O2-), Hydrogen peroxide (H2O2), Hydroxyl ions (OH-)
• Damage Mechanisms:
  • Lipid Peroxidation of Membranes: Free radicals can damage cell membranes.
  • DNA Fragmentation: Leads to apoptosis and cancer.
  • Protein Cross-linking: Can damage cell membranes.

Irreversible Cell Injury (Cell Death)

• Apoptosis (Programmed Cell Death):
  • Significance: Crucial for normal tissue turnover, elimination of damaged cells, and response to pathological stimuli.
• Necrosis (Accidental Cell Death):
  • Mechanism: Characterized by enzymatic degradation of the nucleus and cytoplasm, resulting in cell death.