Introduction to Pathology

Definition of Pathology

• Pathology is the study of disease using scientific methods, investigating changes in cells and tissues due to injury.
• Disease is an abnormality in the structure or function of any part of the body.

Parts of Pathology

• Epidemiology: Studies the occurrence and distribution of diseases in a population, considering factors like sex, age, race, occupation, geographic location, and socioeconomic strata.
• Aetiology: Investigates the cause of the disease, acknowledging that some causes may be unknown (idiopathic/cryptogenic).
• Pathogenesis: Explains the steps that occur in the body leading to tissue injury, focusing on four basic mechanisms: inflammatory, degenerative, carcinogenic, and immunological processes.
• Morphologic Changes: Refers to the structural changes observed in cells and tissues due to the disease. These changes are either macroscopic (visible with the naked eye) or microscopic (requiring a microscope).
• Clinical Features: Encompasses the functional alterations in an organ due to disease, leading to signs (observed by a doctor) and symptoms (reported by the patient).

Epidemiology

• Prevalence: The total number of cases of a disease within a population, at a specific time.
• Incidence: The number of new cases of a disease within a population, during a specific time period.
• Sequelae: Complications or consequences arising from a disease.
• Prognosis: The expected outcome of a disease based on its severity.
• Morbidity: The presence of illness.
• Mortality rate: The measure of deaths within a specific population, within a time period.

Purposes of Epidemiology

• Investigates the extent of a disease in a community.
• Studies the natural history and prognosis of a disease.
• Identifies causes and risk factors.
• Provides information for health care programs to prevent or treat diseases.
• Evaluates health care facilities and programs.
• Provides information for public health development and policy.

Aetiology and Classification of Disease

• Diseases are categorized based on their etiology and pathogenic mechanism.
• Diseases can be congenital (present at birth) or acquired (developed after birth).

Congenital Disease

• Conditions existing at birth or before birth, or developing during the first month of life.
• Genetic/Chromosomal: Examples include hemophilia (X-linked disorder), Down syndrome (extra chromosome 21), and inborn errors of metabolism.
• Non-Genetic: Structural defects or deformities present at birth, such as cleft lip or spina bifida.

Acquired Disease

• Inflammatory: Examples include rheumatoid arthritis and dermatitis (eczema).
• Infective: Caused by bacteria, viruses, or fungi.
• Vascular: Includes atherosclerosis (heart attack) and immune-mediated vasculitis.
• Degenerative: Examples include Alzheimer's disease (brain degeneration) and Parkinson's disease.
• Neoplastic/Growth Disorder: Cancer.
• Therapeutic or Recreational Drug Associated: Can lead to liver or kidney failure, bone marrow suppression, and skin rash.
• Alcohol: Can cause liver disease.
• Poisoning: Can result in lung damage.
• Excessive Smoking: Leads to lung and cardiac problems.
• Metabolic: Examples include gout, diabetes mellitus, and kidney stones.
• Nutritional: Includes deficiency diseases (e.g., anemia) and protein-energy malnutrition.
• Radiation: Can cause thyroid and skin cancers.
• Mechanical: Caused by injuries like road traffic accidents or burns.

Pathogenesis

• The steps that take place in the body, leading to tissue injury (pathological manifestations).
• Four basic pathogenic mechanisms: inflammatory, degenerative, carcinogenic, and immunological processes.

Morphologic Changes

• Structural changes occurring in cells or tissues due to disease.
• Can be macroscopic (grossly visible) or microscopic (requiring a microscope).

Clinical Features

• Functional alterations in an organ due to disease, resulting in signs and symptoms.
• Symptoms: Experienced and reported by the patient.
• Signs: Findings discovered by a doctor during examination.

Timeline of Disease Progression

• Exposure: Initial contact with causative agents or risk factors.
• Latent Period: Time between exposure and the onset of disease.
• Incubation Period: Time between exposure and the development of signs or symptoms.
• Onset of Disease: Beginning of signs or symptoms.
• Outcome & Consequences of Disease: Following onset, disease might lead to:
  • Recovery: Return to normal health.
  • Disability: Residual impairment or dysfunction.
  • Death: Fatal outcome.

Course of Disease

• The course of a disease describes its progression in the absence of any intervention.
• Stages of disease (especially infectious):
  • Exposure: Initial contact with causative agents or risk factors.
  • Incubation Period: Time between exposure and development of signs or symptoms.
  • Onset of Disease: The beginning of noticeable symptoms or signs.
  • Outcome & Consequences of Disease: Various possible outcomes:
    • Recovery: Complete return to health.
    • Disability: Some lingering impairments or dysfunction.
    • Death: Fatal conclusion to the disease process.

Explore the fundamentals of pathology, the study of disease through scientific methods. This quiz covers key components such as epidemiology, aetiology, pathogenesis, and morphologic changes that occur due to diseases. Test your knowledge on how these aspects contribute to understanding health and disease.