Understanding Pathophysiology

• Pathophysiology explains the functional changes within the body due to a disease or pathological condition.

Key Concepts

• Etiology is the cause of a disease or condition; it can be genetic, infectious, environmental, or multifactorial.
• Pathogenesis is the sequence of events from initial contact with an etiological agent until the disease is expressed, involving cellular and molecular mechanisms.
• Morphological changes are structural alterations in cells or tissues characteristic of a disease or condition.
• Clinical manifestations include signs (objective findings) and symptoms (subjective experiences) of a disease.

Cellular Adaptation

• Cells adapt to changes in their environment to protect themselves from injury.
• Adaptive responses include:
  • Hypertrophy: Cell size increases, leading to organ size increase.
  • Hyperplasia: Cell number increases in an organ or tissue.
  • Atrophy: Cell size and function decrease.
  • Metaplasia: Cell type changes to better withstand a stressful environment.
  • Dysplasia: Cellular growth is deranged and often a precursor to cancer.

Cell Injury and Death

• Cell injury occurs when cells are exposed to stressors exceeding their adaptation abilities.
• Cell injury can be reversible or irreversible.
• Necrosis is cell death due to irreversible injury, marked by cell swelling, membrane rupture, and inflammation.
• Apoptosis is programmed cell death, a controlled process that eliminates damaged or unwanted cells without causing inflammation.
• Causes of cell injury:
  • Hypoxia: Lack of oxygen.
  • Ischemia: Reduced blood flow.
  • Physical agents: Trauma, radiation, extreme temperatures.
  • Chemical agents: Toxins, drugs.
  • Infectious agents: Bacteria, viruses, fungi.
  • Immunologic reactions: Autoimmune diseases, allergic reactions.
  • Genetic defects: Mutations.
  • Nutritional imbalances: Deficiencies or excesses.

Inflammation

• Inflammation is a protective response to tissue injury or infection.
• Inflammation aims to eliminate the cause of cell injury, clear out necrotic cells and tissues damaged from the original insult and the inflammatory process, and initiate tissue repair.
• Types of inflammation:
  • Acute inflammation: Rapid onset, edema, neutrophil infiltration, and vasodilation.
  • Chronic inflammation: Prolonged duration, lymphocyte and macrophage infiltration, tissue destruction, and angiogenesis.
• Key components of inflammation:
  • Vasodilation: Increased blood flow to the injured area.
  • Increased vascular permeability: Allows fluid and proteins to leak into the tissues, causing edema.
  • Emigration of leukocytes: White blood cells move from the bloodstream to the site of injury.
    • Neutrophils are predominant in acute inflammation.
    • Macrophages and lymphocytes are predominant in chronic inflammation.

Tissue Repair

• Tissue repair involves regeneration and scar formation.
• Regeneration is the replacement of damaged cells with new cells of the same type, restoring normal tissue structure and function.
• Scar formation occurs when regeneration isn't possible, resulting in collagen deposition and scar formation.
• Factors influencing tissue repair:
  • Severity of the injury.
  • Blood supply.
  • Nutritional status.
  • Infection.
  • Immune response.

Genetic Disorders

• Genetic disorders result from abnormalities in genes or chromosomes.
• Types of genetic disorders:
  • Single-gene disorders: Mutations in a single gene.
    • Examples: Cystic fibrosis, sickle cell anemia, Huntington's disease.
  • Chromosomal disorders: Abnormalities in chromosome number or structure.
    • Examples: Down syndrome (trisomy 21), Turner syndrome (XO).
  • Multifactorial disorders: Combination of genetic and environmental factors.
    • Examples: Heart disease, diabetes, cancer.

Immunologic Disorders

• Immunologic disorders involve dysfunction of the immune system.
• Types of immunologic disorders:
  • Autoimmune diseases: The immune system attacks the body's own tissues.
    • Examples: Rheumatoid arthritis, lupus, multiple sclerosis.
  • Immunodeficiency disorders: A weakened immune system makes the body susceptible to infections.
    • Examples: HIV/AIDS, severe combined immunodeficiency (SCID).
  • Hypersensitivity reactions: Exaggerated or inappropriate immune responses to antigens.
    • Examples: Allergies, asthma, anaphylaxis.

Neoplasia (Cancer)

• Neoplasia is the uncontrolled growth of abnormal cells, resulting in tumor formation.
• Types of tumors:
  • Benign tumors: Non-cancerous, slow-growing, without invasion of surrounding tissues.
  • Malignant tumors: Cancerous, fast-growing, invade and metastasize.
• Key characteristics of cancer cells:
  • Self-sufficiency in growth signals.
  • Insensitivity to antigrowth signals.
  • Evasion of apoptosis.
  • Limitless replicative potential.
  • Angiogenesis (formation of new blood vessels).
  • Invasion and metastasis.
• Carcinogenesis is the process by which normal cells transform into cancer cells, involving multiple genetic mutations and epigenetic changes.
• Common types of cancer:
  • Carcinoma: Cancer from epithelial cells.
  • Sarcoma: Cancer from connective tissues.
  • Leukemia: Cancer of the blood-forming cells.
  • Lymphoma: Cancer of the lymphatic system.