Pathology Historical Concepts Lecture

KAAF University College, School of Nursing, Pathology

• The college is located in Kenya.
• This is a pathology lecture.

Pathology Historical Concepts

• Early pathology involved unsystematic descriptions of diseases, accompanied by theories about their causes and development.
• Physicians and thinkers relied on empiricism and dissections to understand disease.
• Humoral theory, proposed by Empedocles and adapted by Hippocrates, suggested imbalances in body fluids (humors) caused disease.
• Early records of diseases date back to the 16th and 17th centuries BC, like the Edwin Smith Papyrus documenting skin ulcerations without causal explanations.
• Detailed descriptions of diseases emerged during the heyday of Greek civilization in the 4th century BC.
• Hippocrates provided clear descriptions of inflammation and tumors.
• Cornelius Celsius, centuries later, published "De Re Medicina" outlining the four cardinal signs of inflammation (heat, swelling, redness, pain).
• Galen furthered this understanding, adding "loss of function" as a fifth sign a century later.
• Galen also described tumor growth as "crab-shaped," forming the basis of the term "malignant neoplasm" (cancer).
• The humoral theory and early descriptions laid the foundation for pathology until the Middle Ages.

Pathology: Definition and Aspects

• Pathology is the scientific study of changes in structure and function of the body due to disease.
• Disease is defined as an abnormal structure or function in any part of the body.
• Pathology helps understand disease in four key aspects:
  • Etiology (cause of the disease)
  • Pathogenesis (mechanism of the disease)
  • Morphologic changes (structural alterations)
  • Functional derangements and clinical manifestations

Etiology

• Etiology is the cause of a disease.
• Primary etiology: cause is known.
• Idiopathic etiology: cause is unknown
• Etiological factors include genetic, acquired (infectious, nutritional, chemical, physical), environmental, biological and psychological factors.

Pathogenesis

• Pathogenesis is the mechanism by which a disease develops. It describes the sequence of events
• Pathogenesis can occur during the latent/incubation period.
• Pathogenesis leads to morphologic changes.

Morphologic Changes

• Morphologic changes refer to structural alterations in cells or tissues.
• These changes can be gross (visible to the naked eye) or microscopic (seen under a microscope).
• Pathologists use morphologic changes to diagnose diseases.
• They result in changes in organ function.
• They lead to clinical symptoms and signs.

Functional Derangements and Clinical Manifestations

• Morphologic changes influence organ function.
• These changes result in clinical symptoms and signs, course, and prognosis of diseases

Pathology in Summary

• Pathology studies etiology, pathogenesis, morphologic changes, then their clinical features and prognosis.

Disease

• Disease can be characterized in two ways :
  • Abnormal variation in structure or function of any part of the body.
  • A disturbance in the normal function of an organ, part or the whole body.

Causes of Disease

• Environmental factors (physical agents, chemicals, nutritional deficiencies & excesses, biological and psychological)
• Genetic factors or a combination of the two

Course of Disease

• Course of disease refers to the progression and development of a medical condition over time, including the influence of etiological and risk factors, social responses, and adaptations.
• Natural history of the disease is the disease course without interventions.
• Diseases progress through stages, including exposure, latency, biological onset, incubation, clinical onset, permanent damage, and death.
• Latent period is the time between infection and becoming infectious.
• Incubation period is between exposure and the start of symptoms.

Outcome and Consequences of Disease

• Following clinical onset, diseases may resolve, have sequelae (after effects), or result in death

Diagnostic Techniques in Pathology

• Histopathology: tissue studies under a microscope using biopsy.
• Cytopathology: study of cells from various body sites to determine the cause of disease.
• Hematopathology: study of blood disorders.
• Immunohistochemistry: detecting specific antigens in tissues to identify disease type.
• Microbiological, biochemical, cytogenetic, molecular techniques, and autopsy are additional diagnostic tools.

Cell Injury, Adaptation, and Death

• Cell injury underlies all diseases.
• Cells may adapt to injurious agents, or experience reversible or irreversible injury and death.
• Cell death can occur through necrosis or apoptosis.
• Outcomes depend on the type, severity, and duration of injury, and the type of cell.

Cellular Adaptations

• Cellular adaptations are changes cells make in response to stimuli or environment changes.
• Adaptations can be physiological (normal tissues) or pathological (disease states).
• Examples include hypertrophy (increased cell size), hyperplasia (increased cell number), atrophy (decreased cell size), and metaplasia (replacement of one differentiated tissue by another).

Necrosis and Apoptosis

• Necrosis: cell death involving swelling and rupture of cell membranes with spillage of intracellular contents, leading to inflammation.
• Apoptosis (programmed cell death): orderly, controlled cell death without inflammation. Apoptosis is typically associated with single cells being consumed by phagocytes and not causing an inflammatory response while necrosis is often associated with cell death of large regions of tissue.
• Factors like hypoxia, free radicals, cell membrane damage and elevated intracellular calcium levels cause necrosis.

Other topics for presentation/Assignment are Necrosis mechanisms and Types of Necrosis.