Introduction to Pathology

Introduction to Pathology

• Pathology is the scientific study of disease.
• It examines how healthy organs and tissues change when someone is ill.
• Pathology gives insights into disease processes.

What is Pathology?

• Pathology studies disease through scientific methods.
• It studies how healthy organs and tissues transform in sick people.
• The study of pathology provides understanding of diseases.

Pathology as a Foundational and Bridging Subject

• Clinical studies build upon pathology as a foundation.
• Pathology links clinical practice with fundamental knowledge.

Medical Knowledge about Disease

• Key elements include definition, epidemiology (where and when), etiology (cause), pathogenesis (disease evolution), morphology (structural changes), clinical significance (relation to symptoms), prognosis (expected outcome), management (treatment), and prevention (avoidance).

Scope of Pathology

• Includes clinical, experimental, molecular, forensic, chemical/microbiology, immunopathology, and genetics.

Subdivisions of Pathology

• Includes histopathology, cytopathology, hematology, microbiology, immunology, chemical pathology, genetic pathology, toxicology, and forensic pathology.

Learning Pathology: General and Systemic

• General pathology covers common tissue changes (inflammation, cancer, aging).
• Systemic pathology focuses on specific organ changes (goiter, pneumonia, breast cancer).

What is General Pathology?

• Groups disease lesions with common features for study and easier comprehension.
• Includes lesions related to cell degeneration or death, circulatory disorders, inflammation, repair, and growth/development disturbances like cancer.

Objective of General Pathology

• Understand the basic lesions and pathogenic mechanisms of disease.

What is a Lesion?

• Abnormalities in a living body caused by irritant.

What is a Pathologist?

• A pathologist is a person with a PhD in pathology.
• They interpret tissues and laboratory procedures to assist in diagnosis.

Why Clinicians Need Pathology

• The core function of a doctor involves diagnosis, treatment, prevention, and disease control.
• Diagnosis relies heavily on the ability to recognize, understand, and interpret lesions to guide treatment and prevention.

Etiology: Causes of Disease

• Etiology means the causes of a disease.
• Divided into predisposing factors (contributing to disease development) and exciting factors (actual cause of disease).

Etiology: Types of Causes

• Environmental agents include physical, chemical, nutritional, infections, immunological, and psychological factors.
• Genetic factors include age and genes.

One Agent, One Disease, or Several?

• Diseases can arise from one or several factors.
• Examples illustrating the complexity:
  • Malaria (one cause)
  • Diabetes (several possible causes)
  • Smoking (one agent, but increasing risk for several diseases)

Pathogenesis: Mechanisms of Disease

• The mechanism by which the causative agent causes changes in tissues.

Pathological Picture: Examining Changes

• Gross picture—visual abnormalities visible with the naked eye.
• Microscopic picture—examining tissues with a microscope. Other advanced techniques: (electron microscopy, immunohistochemistry, cytogenetics, and molecular studies of diseased tissue and organs.)

Prognosis: Predicting Outcome

• Prognosis is the expected outcome of a disease.
• Requires understanding of pathogenesis, lesions, and ability to visualize the disease process.

Fate: The End Result

• The end result is either cure or death.

Complications of Disease

• Unforeseen pathological changes that can occur during/after the end of the usual course of a disease.

Cell Injury and Cell Death

• Refers to any biochemical or structural alteration that impairs normal cellular function or becomes irreversible.
  • Types of cell death:
  • Irreversible cell injury (cell death)
    • Programmed cell death (apoptosis)
    • Accidental cell death (necrosis)
  • Causes of cell injury:
    • Oxygen deprivation
    • Nutrient deprivation
    • Chemical agents
    • Infectious agents
    • Immunological reactions
    • Genetic disorders
    • Physical factors (trauma, temperature extremes, radiation)
    • Free radicals
    • Aging

Hypoxic Cell Injury

• Acute cellular swelling is an early sign of cell injury.
• Severe swelling may be visible by light microscopy as hydropic or vacuolar degeneration.

Cell Injury Caused by Chemicals

• Chemical damage via two methods
  • Direct binding to critical cellular components.
  • Chemical transformation to reactive metabolites producing free radicals damaging membranes and causing cell death.

Cell Injury Caused by Free Radicals

• Free radicals are chemical species with an unpaired electron.
• They react with other molecules.
• Important free radicals include superoxide, hydrogen peroxide, and hydroxyl ions.

Mechanisms of Free Radical Damage

• Lipid peroxidation of membranes
• DNA fragmentation leading to apoptosis and carcinogenesis
• Protein cross-linking

Irreversible Cell Injury (Cell Death)

• Marks the point where cell injury becomes irreversible or reaches the "point of no return". Classified into apoptosis and necrosis (accidental cell death). Necrosis is characterized by microscopic changes from enzymatic breakdown.

Apoptosis: Programmed Cell Death

• A regulated mechanism to eliminate unwanted/damaged cells.
• Relatively minimal host response.
• Examples in development, tissue remodeling, and eliminating unwanted cells (viral infections)
• Typically affects single cells or small clusters.
• Characterized by specific morphologic changes

Significance of Apoptosis

• Essential for normal tissue turnover.
• Significant in response to hormone-induced atrophy (e.g., endometrium in menstrual cycle), development (embryogenesis), and pathological processes (viral infections or chemotherapy).

Apoptosis vs. Accidental Cell Death (Necrosis)

• Contrasting Features:
• Apoptosis (programmed cell death): Cell shrinkage; Intact cellular membranes; Fragmented DNA; Characteristic apoptotic bodies.
• Necrosis (accidental cell death): Cell swelling; Damaged cellular membranes; DNA fragmentation; Inflammation typically present.

This quiz covers the essential principles of pathology, including the study of disease processes and the changes in healthy organs and tissues. Understanding pathology is crucial as it links clinical practices with fundamental medical knowledge. Explore the scope, key elements, and foundational aspects of pathology in this quiz.