Pathology Historical Concepts and Development

Course Information

• Course: Pathology
• Credit: 2
• Lecturer: Richmond Kwakye
• Institution: KAAF University College, School of Nursing

Pathology - Historical Concepts

• Early pathology involved unsystematic descriptions of diseases and theories about their causes and development.
• Physicians and thinkers relied on empiricism and observation to understand diseases.
• There were no advanced tools.
• Early theories included the humoral theory.

Pathology - Historical Development

• Earliest records of diseases date back to the 16th and 17th centuries BC.
• The Edwin Smith Papyrus depicted skin ulcerations, but lacked a causal or developmental mechanism.
• Greek civilization (4th century BC) led to more detailed descriptions and theories.
• The humoral theory proposed by Empedocles and developed by Hippocrates connected disease to imbalances of bodily fluids.
• Hippocrates described inflammatory processes and tumors.
• Cornelius Celsius, centuries later, outlined the four cardinal signs of inflammation (heat, swelling, redness, pain).
• Galen later added the concept of loss of function.
• Galen also described the "crab-shaped" aspect of tumor growth, which became the basis for the term "malignant neoplasms (cancers)".
• Humoral theory remained a cornerstone of medical understanding until the Middle Ages.

Pathology - Modern Pathology

• The first age of modern pathology involved autopsies and macroscopic examinations of diseases (Antonio Benivieni).
• The second age advanced to microscopy, tissues, and cellular diseases.
• The third age saw the use of immunology and molecular biology in understanding diseases' causes and effects.
• The department of pathology at USP University, Sao Paulo, is part of contemporary studies.

Definition of Pathology and Disease

• Pathology is the study of diseases.
• Diseases are defined as abnormalities in bodily structure or function.
• Pathology helps understand diseases by examining etiology, pathogenesis, morphologic changes and clinical manifestations.

Etiology (Causes of Disease)

• Etiology is the cause of a disease.
• Primary etiology: known cause of disease.
• Idiopathic etiology: unknown cause of disease.
• Causes can have genetic or acquired origins (infectious, nutritional, chemical, physical etc.).

Pathogenesis (Mechanism of Disease)

• Pathogenesis explains how a cause produces disease.
• Pathogenesis may occur during latent or incubation periods.
• Pathogenesis leads to morphologic changes in tissue or organs.

Morphologic Changes

• Morphological changes are structural alterations of cells and tissues in disease.
• These changes can be gross (visible to the naked eye) or microscopic (only seen through a microscope).
• Morphologic changes are specific to diseases and help pathologists identify them.
• These changes lead to functional alterations which, in turn, manifest as symptoms and signs.

Functional Derangements and Clinical Significance

• Morphological changes affect organ function, leading to clinical symptoms and signs.
• Course and prognosis of a disease is determined by these functional changes and alterations.

Disease Outcomes

• Following disease onset, outcomes can involve resolution, sequelae (residual effects), or death.

Diagnostic Techniques

• Histopathology: examines tissues with biopsies under a microscope.
• Cytopathology: analyzes bodily cells from various sources to identify the cause of a disease.
• Hematopathology: examines blood and blood-forming tissues.
• Immunohistochemistry detects specific tissue antigens to identify diseases.
• Microbiological examination.
• Biochemical examination.
• Cytogenetics.
• Molecular techniques.
• Autopsy.

Cell Injury, Adaptation, and Cell Death

• Cell injury underlies all diseases.
• Cells react to injurious agents by adapting, acquiring reversible injury, or undergoing irreversible injury (and death).
• Two types of cell death are necrosis and apoptosis.

Necrosis

• Necrosis is cell death involving cellular swelling, membrane rupture, and the release of intracellular contents, causing inflammation.
• Necrosis does not happen in a dead organism. Autolysis and heterolysis occur instead.
• Necrosis mechanisms include hypoxia, free radical injury, and cell membrane damage.

Apoptosis

• Apoptosis is programmed cell death. It's the death of single cells within clusters, in contrast with necrosis which applies to clusters of cells.
• Apoptosis involves cell shrinkage and fragmentation (apoptotic bodies) without inflammation.
• Apoptosis is a natural process for cell removal during development, menstruation etc.
• Apoptosis may occur in pathological conditions caused by mild injurious agents.

Assignment

• Students must briefly explain the mechanisms of necrosis, necrosis types, and answer other relevant questions (from the handout).