Introduction to Pathology

Pathos

Greek — “feeling or suffering”

Pathologization

The process of defining a condition or behavior as pathological

-path

Used to indicate a disease

Pathologies

aka diseases

• Etiology - cause

• Pathogenesis - mechanism of development

• Morphologic changes - structural alterations of cells

• Clinical manifestations - consequences of changes

4 components of pathology

• System being studied

• Focus of examination

Divisions of pathology

General pathology

• A broad and complex scientific field which seeks to understand the mechanisms of injury to cells and tissues, as well as the body's means of responding to and repairing injury

• Forms the foundation of pathology, the application of this knowledge to diagnose diseases in humans and animals

• Describe the practice of both anatomical and clinical pathology

19th century

Pathological anatomy/morbid anatomy as a subject

Late 19th-20th century

Pathology as a field of medicine

Late 1920s-Early 1930s

Pathology deemed as medical specialty

Juristic

Classification of disease by speed of advent of death

Epidemiological

Classification of disease by incidence, distribution, and control of disorders in a population

Statistical

Classification of disease by the incidence and prevalence of disease

• Diagnose and characterize disease in living patients by examining biopsies or bodily fluids

• Cancer diagnosis

• Analyzes blood samples

• Set guidelines and standards for medical laboratory testing

• May conduct autopsies to investigate causes of death

Works done by pathologists

Naked eye examination

Method of Pathology

• Gross examination (ex. colon cancer)

Light microscopy

Method of Pathology

• Determination of morphology (ex. adenocarcinoma)

Immunocytochemistry

Method of Pathology

• Demonstration of specific proteins (ex. renaut bodies in nerve fascicles)

Electron microscopy

Method of Pathology

• Examination of organelles (ex. junctional complexes)

Molecular biology

Method of Pathology

• Chromosomal analysis and chip technology

• Sequencing

Fixing

Laboratory Procedure

• Formaldehyde, cryostat

• Preserves tissue cells from degradation

Processing

Laboratory Procedure

• Dehydration

• Clearing and infiltration embedding

• Sectioning

• Staining

Haematoxylin

General staining when paired with eosin

Eosin

General staining when paired with haematoxylin

Connective tissue

Masson’s trichrome stain is used for?

Connective tissue

Mallory’s trichome stain is used for?

Reticular fibers, nerve fibers, fungi

Silver stain is used for?

Elastic fibers

Orcein stain is used for?

Blood cells

Wright’s stain is used for?

Basement membrane, localizing carbohydrates

Periodic acid-Schiff stain (PAS) is used for?

Elastic fibers

Weigert’s elastic stain is used for?

Distinguishing cells from extracellular components

Heidenhain’s AZAN trichome stain is used for?

Functional derangement

The disruption or malfunction of an organ's normal function, often as a direct consequence of morphological (structural) changes, and is the basis for a disease's clinical signs, symptoms, course, and prognosis

Clinical manifestation

A symptom or sign of a disease that can be observed or detected by a healthcare provider or patient, representing the physical or functional outcome of a disease process at the macroscopic level

• Atrophy

• Hypertrophy

• Hyperplasia

• Metaplasia

Cellular adaptations

Hypertrophy

Increase in the size of organ because of the increase in the size of component cells

Hyperplasia

• Increase in the size of the organ because of the increase in the number of component cells in the organ

• Hypergenesis — confused with benign hyperplasia

Metaplasia

• The conversion, during postnatal life, of one differentiated cell type to that of another

• Pathological condition that commonly occurs in the context of chronic inflammation and carries an increased risk of cancer

Cell death

• Ultimate result of cell injury

• Major consequence of ischemia, toxins and immune reactions

• Critical during normal

  • Embryogenesis

  • Lymphoid tissue development

  • Hormonally induced involution

  • Aim of cancer radiotheraphy and chemotherapy

Ischemia

Lack of blood flow to tissues

Coagulation necrosis

• More common type of necrosis

• By exogenous stimuli

• Manifested by

  • Severe cell swelling or cell rupture

  • Denaturation

  • Coagulation of cytoplasmic proteins

  • Breakdown of cell organelles

Myocardial infarct

Residual oagulative necrosis

Apoptosis

• More regulated event

• Designed for normal elimination of unwanted cell populations (embryonic and physiologic process)

• No inflammation

• Chief morphologic features

  • Chromatin condensation

  • Fragmentation

• Reversible injury

• Cell death

• Subcellular alterations and cell inclusions

• Intracellular accumulations

• Pathologic calcifications

Acute cell injury

Subcellular alterations

Acute cell injury as a response to more chronic or persistent injurious stimuli

Intracellular accumulations

• Lipids, carbohydrates, proteins

• Occur as a result of derangements in cell metabolism or excessive storage

Pathologic calcifications

A common consequence of cell and tissue injury

• Hypoxia

• Physical agents

• Chemical agents and drugs

• Infectious agents

• Immunologic reactions

• Genetic derangements

• Nutritional imbalances

Causes of cell injury

Hypoxia

• Ischemia

  • Arteriosclerosis

  • Thrombi

• Inadequate oxygenation of blood due to cardiorespiratory failure

• Loss of oxygen-carrying capacity of blood due to anemia and carbon monoxide poisoning

Physical agents

• Mechanical trauma

• Extremes of temperature

• Radiation

• Electric shock

Chemical agents and drugs

• Glucose or salt

• Oxygen

• Poisons

• Environmental and air pollutants

• Poisons (arsenic, cyanide, mercuric salts

• Insecticides and herbicides

• Industrial and occupational hazards

• Social stimuli

• Therapeutic drugs

Infectious agents

• Submicroscopic viruses

• Rickettsiae

• Bacteria

• Fungi

• Tapeworms

• Ascaris

Immunologic reactions

• Anaphylactic reaction to a foreign protein or drugs

• Endogenous self-antigens (autoimmune diseases)

Genetic derangements

• Congenital malformations associated with Down’s Syndrome

• Subtle alteration of the coding of hemoglobin S in Sickle Cell Anemia

• Enzyme lack

• DNA alterations

Nutritional imbalances

• Protein-calorie deficiencies

• Vitamin deficiencies

• Nutritional excesses

  • Atherosclerosis

  • Obesity