Introduction to Pathology

Introduction to Pathology

• Pathology is the scientific study of disease.
• Disease is any disturbance of an organ or tissue's structure and/or function.

Common Terms in Pathology

• Patient: The person affected by the disease.
• Lesions: Characteristic tissue and cell changes caused by disease.
• Pathologic changes (morphology): Visible tissue changes, such as size, shape, color, consistency, weight, and borders.
• Causal factors (etiology): The reasons for the lesions.
• Mechanism (pathogenesis): The process by which the lesions are produced.
• Functional implications (symptoms & signs): The patient's experiences and the clinician's observations.
• Clinical significance: Determining the cause (diagnosis), its progression (prognosis), treatment options, and prevention of further complications.

Aspects of Studying Diseases

• Definition: A clear statement of the condition.
• Etiology: The cause of the disease.
• Predisposing/Risk factors: Factors that increase the likelihood of developing a disease.
• Exciting factors: The immediate trigger for a disease.
• Pathogenesis: The development process of the disease.
• Pathological Picture (Gross and Microscopic): The visual aspects of the disease at the macroscopic & microscopic levels.
• Gross appearance: What the naked eye sees.
• Microscopic appearance: How the disease appears under a microscope.
• Prognosis: The likely course of the disease.
• Complications: Possible secondary or additional problems due to the disease.

Historical Background

• Hippocrates is known as the "Father of Medicine," emphasizing the love of humanity in healthcare.
• Sir William Osler is considered the "Father of Modern Medicine," highlighting the importance of treating the patient with the disease.
• Rudolf Virchow is known as the "Father of Pathology."
• Medical education emphasizes not only enabling students to make a living but also ensuring the health of the community.

Cellular Injury

• Cell injury is defined as metabolic and morphological changes in a tissue when it's exposed to an injurious agent.
• Causes include hypoxia, ischemia, immunological dysfunction, pathogens, physical factors (heat, cold, radiation, trauma), congenital disorders, chemical injury (acids, alkalis, toxins), and nutritional/vitamin imbalances.

Cellular Changes During Injury

• Cells respond to injury ranging from adaption to reversible injury to irreversible injury and cell death.
• Important mechanisms of cell injury include DNA damage, ATP production disruption, cell membrane damage, and protein synthesis disturbance.

Morphological Alterations in Cell Injury

• Alterations can be reversible or irreversible.
• Reversible changes precede irreversible changes.
• Irreversible damage leads to cell death (necrosis or apoptosis).
• Changes can be characterized at the gross and microscopic level

Classification of Morphologic Forms of Cell Injury

• The different forms of cell injury, encompassing reversible and irreversible injuries, programmed cell death (apoptosis), and disrupted metabolic processes.

Clinical Application

• The loss (leaking) of intracellular enzymes from dead cells in the blood can be used as a clinical marker for cell injury.
• Clinically important examples include myocardial injury (using markers like Troponin), hepatitis (using transaminases), pancreatitis (using amylase and lipase), and biliary tract obstruction (using alkaline phosphatase).

Intracellular Accumulations

• Accumulations of substances (water, fat, carbohydrates, proteins, pigments) result from excess or abnormal synthesis or metabolism or from an interruption in normal removal, leading to abnormal tissue structures and function.
• Types include hydrophic change, hyalins, mucoid change, fatty change (steatosis), cholesterol deposits, and stromal fatty infiltration.

Intracellular Accumulations (Pigments and Iron-related changes)

• Exogenous pigments: from outside the body (e.g., tattoos, dust, metals)
• Endogenous pigments: produced within the body (e.g., melanin, lipofuscin, bilirubin, hemosiderin)

Disturbance of Pigment Metabolism

• Pigments are substances with intrinsic color, found either exogenously or endogenously in tissues.
• Endogenous pigments include melanin, lipofuscin. Hemosiderin.
• Exogenous pigments can be inert or harmful to cells.

Pathological Melanin Pigmentation

• Overproduction or lack of melanin can lead to various conditions (e.g., Addison's disease, chloasma, melanomas, melanosis coli).
• Conditions related to decreased melanin production include albinism, leukoderma, and vitiligo.

Pathological Calcification

• Abnormal calcium salt deposition in tissues other than bone or teeth ("dystrophic calcification") may happen due to normal blood calcium levels but with necrotic or degenerative tissues.
• The deposition of calcium salts in normal tissues ("metastatic calcification") happens due to excessive calcium in the blood (hypercalcemia). Common causes include hyperparathyroidism.

Calcinosis & Pathologic Ossification

• Calcinosis is a condition characterized by abnormal calcium salt deposition in skin and subcutaneous tissues.
• Pathologic ossification involves the formation of bone-like structures in non-osseous tissues, often following injury or inflammation.

Brown Atrophy of the Heart

• It's a condition where the heart shrinks and becomes discolored, often secondary to malnutrition or severe illness. Microscopic appearance shows thin myocardium fibers with yellowish lipofuscin granules.

Hyperbilirubinemia

• Increased bilirubin in the blood leads to jaundice (yellowing of tissues).
• Causes include hemolysis of red blood cells, bile duct obstruction, or impaired liver function.