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INTRODUCTION TO PATHOLOGY

Jhia Anjela D. RiveraDepartment of Biological SciencesSchool of Science and TechnologyCentro Escolar University

WHY DO WE NEED TO STUDY PATHOLOGY?

• To foster understanding of the mechanisms of DISEASE(pathogenesis) as a foundation for dealing with a vast amount ofclinical information the student will encounter in later clinical years.

DISEASE

• An abnormal alteration of structure or function in any part of thebody.

CLASSIFICATION OF DISEASE

• Developmental – genetic, congenital

• Inflammatory – Trauma, infections, immune, etc.

• Neoplastic – tumors, cancers

• Degenerative – ageing

PATHOLOGY

Etymology:• Came from two Greek words

• pathos , disease and logia , study

Formal Definition:• Scientific study of disease• Foundation of medical science and practice• Bridging discipline devoted to the study of the structure and functional

changes in cells, tissues and organs that underlie diseases

“Pathology attempts to explore “whys” and “wherefores” of the signs and symptoms of diseases.”

VISUALIZATION OF PATHOLOGY

• Radiographs

• CT-Scans

• MRI (Magnetic Resonance Imaging)

• Ultrasound

• Clear Drawings

• Molecular Abnormalitiesc

HISTORY OF PATHOLOGY

• Era of Medical Antiquity• Early dominance of Animism (From the earliest times, treatments involved

incantations, invoking the gods, and the use of magical herbs, amulets, and charms.)

Plato and Pythagoras

• Era of Morbid Anatomy

• Autopsies performed scientifically from about 1500A.D, 19th century in Germany

Rokitansky and Aschoff

CELLULAR PATHOLOGY

• Its application revolutionized medicine.• Pasteur’s demonstration of Germ Theory of Disease

• The impact of pathology in the realm of molecular changes• Cancer and congenital diseases

MICROSCOPY

SCOPE OF PATHOLOGY

• Scientific knowledge about human diseases that is derived fromobservations on patients or , by analogy, from experimental studieson animals & cell cultures.

• Clinical medicine is based on a longitudinal approach to a patient’sillness

• Clinical pathology is more concerned with a cross-sectional analysis atthe level of the disease itself, studied in depth- the cause andmechanisms of the disease, and the effects of the disease upon thevarious organs and systems

SUBDIVISIONS OF PATHOLOGY

• Cytopathology : the investigation and diagnosis of disease from theexamination of isolates cells

• Histopathology : the investigation and diagnosis of disease from theexamination of tissues

• Haematology : the study of the disorders of the cellular andcoagulable components of blood

SUBDIVISIONS OF PATHOLOGY

• Toxicology : the study of the effects of known or suspected poisons

• Forensic pathology : the application of pathology to legal purposes(e.g. investigation of death in suspicious circumstances)

• Chemical pathology : the study & diagnosis of disease from thechemical changes in tissues & fluids

TECHNIQUES IN PATHOLOGY

• Light Microscopy : the structure of tissues & cells in health & disease

• Histochemistry : is the study of the chemistry of tissues

• Immunohistochemistry : employ antibodies( immunoglobulins with antigen specificity) to visualize substances in tissues sections or cell preparations

TECHNIQUES IN PATHOLOGY

• Electron Microscopy : study of disorders at an organelle level, & to the demonstration of viruses in tissue samples

• Biochemical techniques : fluid & electrolyte homeostasis, serum enzyme assays e.g. raised levels of cardiac enzymes in the blood

• Haematological techniques : in the diagnosis & study of blood disorders

TECHNIQUES IN PATHOLOGY

• Molecular Pathology : many advances come from the relatively new science of molecular pathology• Defects in the chemical structure of molecules arising from errors in the

genome, using IN SITU HYBRIDISATION e.g.Hg molecule,collagen molecule, alterations in the genome governing the controlof cell & tissue growth

GENERAL and SYSTEMATIC PATHOLOGY

• General Pathology is our current understanding of the causationmechanisms ,and characteristics of the major categories of disease(e.g. congenital versus acquired diseases, inflammation, tumors,degenerations) / is the foundation of knowledge that has to be laiddown

• Systematic Pathology is our current knowledge of specific diseases as they affect individual organs or systems( e.g. appendicitis, lung cancer, atheroma).

• “Systematic” should not be confused with “Systemic”

DISEASE MECHANISM

• Disease Mechanisms constitute general pathology

• A logical and orderly way of thinking about diseases and their characteristics must be cultivated

- Epidemiology / incidence

- Etiology (cause)

- Pathogenesis (evolution/ process of the development ofdisease)

- Pathological and clinical features (structural changes)

- Complications and Sequelae

- Prognosis (result prediction)

ETIOLOGY

• Study of the cause of disease

• Environmental etiologic Factors:• Physical• Chemical• Nutritional• Infections• Immunological• Psychological

• Genetic etiologic Factors:• Age• Genes

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PATHOGENESIS (Disease Process)

• Refers to the sequence of events in the response of the cells ortissues to the etiologic agent, from the initial stimulus to theultimate expression of the disease.

• The mechanism through which the etilogy( cause) operates toproduce the pathological and clinical manifestations.

• Examples include: inflammation, degeneration, carcinogenesis,immune reactions

DIAGNOSIS

• Diagnosis is the act of naming a disease in an individual patient

• The process of making diagnoses involves: taking a clinical history todocument symptoms, examining the patient for clinical signs and ifnecessary, performing investigations guided by the provisionaldiagnosis based on signs & symptoms

DIAGNOSTIC PATHOLOGY

• In living patients we investigate & diagnose their illness by applyingpathological methods to the examination of TISSUE BIOPSIES& BODYFLUIDS

• Biopsies are samples of tissue removed from a patient for diagnosticpurposes.

• Resections specimens are the whole or part of an organ removed fora previously diagnosed condition.

DIAGNOSTIC PATHOLOGY

• Biopsies can be obtained by a variety of methods: needle biopsy,endoscopic biopsy and incisional biopsy

• Cytology involves the examination and interpretation of dispersedcells rather than solid tissues,usually for the diagnosis of cancer &pre-cancerous lesions.

• These cells can be obtained by a variety of methods according to theorgan being investigated

DIAGNOSTIC PATHOLOGY

• Exfoliative cytology : cells shed from, or scraped or brushed off ,anepithelial surface

• Fluid cytology : cells withdrawn with the fluid in which they aresuspended

• Washings : cells flushed out of an organ using an irrigating fluid

• Fine –needle aspiration cytology : cells sucked out of a solid tissueusing a thin needle attached to a syringe.

AUTOPSIES

• Autopsy( necropsy and post- mortem examination are synonymous)

• Autopsy means to ‘see for oneself’

• Autopsies are used for:

-determining the cause of death

-audit of the accuracy of clinical diagnosis

-education of undergraduates & postgraduates

AUTOPSIES

• Research into the causes and mechanisms of disease

• Gathering accurate statistics about disease incidence

• There has been a regrettable decline in the autopsy rate during thelatter half of the 20th century