Pathology Definition & Concepts PDF

Pathology: Definition The word pathology comes from the Greek words • Pathos: meaning suffering or diseases • Logos: meaning study Pathology is the scientific study of disease which involves the study of the structural, biochemical, and functional changes in cells, tissues and organs resulting from...

Pathology: Definition The word pathology comes from the Greek words • Pathos: meaning suffering or diseases • Logos: meaning study Pathology is the scientific study of disease which involves the study of the structural, biochemical, and functional changes in cells, tissues and organs resulting from the disease process Father of Modern Pathology Dr. Rudolf Virchow (1821 – 1902) was a German physician and pathologist All forms of disease start with the molecular or structural alteration in the tissue and the cells Omnis cellula e cellula ("All cells come from cells") Importance of Pathology as a Discipline • Bridge between the basic sciences and clinical medicine • It is the scientific foundation of all the branches of medicine • It explains the mechanism of disease • It outlines, defines and explains the presentation and manifestation of diseases • It identifies the fault lines in health and diseases through investigation • It foretells the progress and outcome of diseases Basic Sciences Pathology Clinical Sciences Components of Pathology •Etiology: Causal factors responsible for the lesions. •Lesions: Are the characteristic changes in tissues and cells produced an etiology in a patient •Morphology: is the study of changes in form and organization of a organ, tissue and cells. Pathologic changes can be recognized with naked eye (gross) or by microscope (microscopic) examination of tissues. •Pathogenesis: describes the mechanisms by which a disease develops and progresses •Clinical manifestation: Functional implications of the lesion felt by the patient are symptoms and those discovered by the clinician are the physical signs. •Diagnosis: Deals with all the investigation and interpretation of findings in a patient •Prognosis: prediction about the course of a disease Etiology (Cause) A. Genetic •Developmental Defects: growth retardation, malformation •Cytogenetic Defects: Polyploidy, Aneuploidy •Simple gene defects: Mutation (muscular dystrophy) B. Acquired •Hypoxia or Ischemia: Myocardial infarction •Physical agents: temperature, pressure, radiation •Chemicals: drugs, poisons, venoms •Microbes: viruses, bacteria, fungi, worms •Immune reactions: Hypersensitivity reaction •Nutrition: Night blindness •Aging: Alzheimer's disease Etiology Disease Disease Disease Disease Disease One agent  One disease - Malaria Several agents  One disease - Cancer One agent  Several diseases - Smoking Pathogenesis Pathogenesis refers to the sequence of events in the response of cells or tissues to the etiologic agent, from the initial stimulus to the ultimate expression of the disease. The study of pathogenesis remains one of the main domains of pathology Pathophysiology is a study at the intersection of pathology and physiology, dealing with the disordered physiological processes that cause, result from, or are otherwise associated with a disease or injury Morphology The morphology refer to the structural alterations in the organ, tissues or cells that are either characteristic of the disease or diagnostic of the etiologic process Macroscopic (Gross) Microscopic Diagnosis The scientific process of determining the nature of a disease or disorder and distinguishing it from other possible conditions. The term comes from the Greek gnosis, meaning knowledge It involves • • • • Identifying the etiology The extend of changes in morphology The degree of deviation from the normal (grade) The extent of the disease (stage) Diagnostic Approaches in Pathology A. Diagnostic Imaging •X Ray - PA/lateral, Double contrast, Barium studies • Ultrasound • Mammography • CT scan • MRI • PET Scan B. • • • • C. • • • Laboratory Investigations Histological Analysis Cytological Analysis Analysis of Biomarkers Examination of blood & bone marrow Molecular Diagnostics Molecular cytogenetic Mutational analysis Microarray analysis Subdivisions of Pathology Morphological Branches A. Histopathology or Anatomic Pathology 1. Surgical Pathology 2. Experimental Pathology 3. Forensic Pathology And Autopsy Work B. Cytopathology C. Haematology Non-morphological Branches A. Clinical Pathology B. Clinical Biochemistry C. Microbiology D. Immunology F. Molecular Pathology Histopathology Examination of tissues to detect the changes in structure STEP1 due to disease process •Tissues are obtained by biopsies and excision of organs •Once the tissue is removed from the patient’s body, it is immediately preserved or fixedSTEP2 by putting it in a container of formalin (10% formaldehyde). •Tissue is processed in a special multistep way and the end result is very thin slices of stained tissue (4-6 microns) glued on a slide. SLIDE IS READY THIN SLICES OF TISSUE Routine Processing of Tissue for Histopathology Sequential Steps • Fixation • Dehydration • Clearing Processing • Impregnation • Embedding and blocking • Section cutting (Microtomy) • Mounting • Staining of Slides (H & E) Grossing--(appearance, measurements, pathological changes noted) and then bits of <ssue from areas of abnormality taken Tissue Processing Ttechnique of fixing the tissue into paraffin is called tissue processing • The main steps 1. Dehydration: Gradual removal of water from the tissue using ascending grades of ethyl alcohol(or other agents) to prevent tissue shrinking. 2.Clearing: Replacement of alcohol in tissue by clearing fluid like xylene, benzene, or acetone in which wax is soluble Embedding: Tissues are impregnated in paraAn-hardens the <ssue Cutting: Paraffin block are cut by microtome using metal knife, into thin sections (4 to 6 microns)This is done with a microtome Mounting: - Sections spread on the hot plate and mounted on glass slides. Staining: Tissue is "deparaffinized" to get the paraffin wax out of the tissue and allow water soluble dyes to penetrate the sections and then Staining done coverslip slide must be covered with a thin piece glass Automa<c <ssue processor Tissue embedding centre Rotary microtome Light Microscopy Immunohistochemistry (IHC) Immunohistochemistry (IHC) is a technique that exploits the specific binding between an antibody and antigen to detect and localize specific antigens in cells and tissue The tissue of interest is fixed and stained with antibodies specific to the antigens. Detection is accomplished by using enzymes such as horseradish peroxidase (HRP) or alkaline phosphatase (AP). Samples are visualized using microscopy. Immunohistochemistry (IHC) Routine Stain Special Stains