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Transcript
INTRODUCTION TO PATHOLOGY PATH 303 General Pathology 4(3-2) Dr. Temur Ahsan Khan PATHOLOGY Pathos (suffering or disease) logos (science) Pathology is the study of structural and functional changes of body in disease, including changes in cell, tissues, organs and body fluids. Pathology forms a bridge between basic studies of Anatomy, Physiology, biochemistry and clinical subjects of Medicine and Surgery DISEASE French word “Des” (away) “aise” (ease) it is a condition in which the individual suffers from discomfort i.e. not at harmony with its environment. Lesion It is the abnormal structural or functional change in the body as a result of disease and may be detected by gross (necropsy), microscopic (histopathology) or biochemical methods (clinical pathology). PATHOGNOMONIC LESION An alternation that indicates without doubt the cause of a particular disease e.g. finding of Negri bodies in rabies etc PATHOGENESIS It is a progressive development of a disease process from its initiation to conclusion in recovery or death. Disease is a dynamic process which progresses from molecular or bio-chemical alternations to structural (ultrastructural, microscopic and gross lesions) and to functional changes which are seen as signs and symptoms of disease. Functional Structural Pathological changes Moderate Time D IAGNOSIS It is the identification of disease through the clinical examination and application of various laboratory tests. A pathological diagnoses should include lesions, etiology (cause) pathogenesis and clinical consequences. Prognosis • It is the estimation of the clinician or pathologist regarding the expected outcome of disease like favorable, guarded or grave ete Etiology It is a study of the causes of disease. An etiologic agent induces cell and tissue injury leading to clinical manifestations of disease There are numerous causes of disease which are divided into 1. 2. Exogenous (Environmental or extrinsic factors) Intrinsic Internal defects BIOLOGICAL AGENTS (INFECTIOUS AGENTS, PATHOGENS, MICROORGANISMS) These are diverse group of biological agents, ranging from a few nm to a few meters in size. The disease producing biological agents mostly have a parasitic mode of life and include prions, viruses, chlamydia, rickettsia, mycoplasma, bacteria, fungi, protozoa and metazoa. CHARACTERISTICS OF MICROBIOLOGICAL AGENTS Biological associations and relationships. Commensals: coexistence without injury or benefit Symbiotic: Mutually beneficial coexistence. Example: microflora and fauna in the rumen and colon of herbivores and E.coli in the gut of humans producing vit.K. Parasitic/Predators: causing morbidity and mortality in the host (man and animals) PORTAL OF ENTRY IN THE BODY: Lungs and mucociliary mechanisms Mouth and GIT. Gastric acidity Intact membranes Size of inoculum-MID 50 and MLD 50 HOST DEFENSE MECHANISMS. Humoral- innate natural immunity, acquired immunity, antibody formation. Cellular defense- Phagocytosis by neutrophils and monocytes. SURVIVAL OF MICROORGANISMS IN THE BODY: Spreading factor- Hyaluronidase Evasion of phagocytosis- capsule formation Sequestration-coagulase,collagenase, organotropism INTRACELLULAR LOCALIZATION Facultative- Mycobacterium, Brucella, Histoplasma, Nocardia, Toxoplasma, Theileria Obligate- Rickettsia, Viruses, Plasmodium. HOW MICROORGANISMS CAUSE DISEASE Host factors- age, nutrition, immune status, intercurrent disease, opportunistic infection, predisposing factors GENERAL MECHANISM OF DISEASE PRODUCTION: Dysfunction and death of host cells Release of endotoxins and exotoxins Induction of immune and inflammatory responses causing injury and disease. MECHANISMS OF VIRAL INJURY: Host cell receptors Type- specific transcription factors Crossing physical barriers Immune cell-mediated killing Alteration of apoptosis pathway MECHANISMS OF VIRAL INJURY: CONT….. Induction of cell proliferation and transformation Inhibition of host cell DNA,RNA or protein synthesis Damage to plasma membrane Damage to cells involved in antimicrobial defense MECHANISMS OF BACTERIAL INJURY: Depends upon their ability to Adhere to host cells (b) Invade the cells and tissues (c) To deliver toxins that damage the cells and toxins Bacterial adherence to host cells Mechanisms- Adhesins, fibrils and fimbrae (a) VIRULENCE OF INTRACELLULAR BACTERIA: Facultative intracellular bacteria Subversion of host immune response Inhibition of synthesis of host cell proteins ELABORATION OF BACTERIAL ENDOTOXINS: Septic shock Disseminated intravascular coagulation cytokines BACTERIAL ENDOTOXINS Bacterial enzymes Inhibition of protein synthesis Cellular necrosis Neurotoxins- Cl.Botulinum and Cl.Tatani, paralysis, respiratory failure WHAT IS PATHOLOGY? Study of derangement of molecules, cells, tissues, and function in the living organisms in response to injurious agents and deprivations COMMON TERMS USED IN PATHOLOGY Lesions (Gross, microscopic, chemical, molecular, immunologic) Etiology Pathogenesis Symptoms Postmortem examination/autopsy/necropsy Biopsy Morbid changes Postmortem changes HISTORY The first concept of disease The demoniac concept of disease- witch doctor (17 thousand years old-Paintings in the caves of Pyrenees mountains) Theological concept of disease 4000 B.C. (embalming)- disease due to divine displeasure- Priest Humoral concept of disease- Greece-Hippocrates (460-377 B.C.) Blood-warm and moist (air) Phlegm- cold and moist (water) Yellow bile- warm and dry (fire) Black bile- cold and dry (earth) DEVELOPMENT OF ANATOMY, PHYSIOLOGY, AND PATHOLOGY Aristotle (384-322 B.C.) - modern anatomy and physiology Claudius Galen (131-206 A.D.)- Father of anatomy FIRST TEXTBOOK ON VETERINARY MEDICINE Renatus Vegetius (450-500 A.D.) “Book of the Veterinary Art” – father of veterinary medicine CENTURY OF ANATOMY Antanio Benivieni (1440-1502)postmortem examination- father of Pathological anatomy Leonardo da Vinci (1452-1519)Artist- Anatomy of horse Andreas Vesaleus (1514-1564)Belgian- At the age of 24 became Professor of anatomy at Padua, in Italy DISCOVERY OF BLOOD CIRCULATION William Harvey (1578-1657)- Englishmanairtree Marcello Malpighi (1628-1694)- Italiancapillaries and erythrocytes, and microscopic description of kidney, lungs, and spleen INVENTION OF MICROSCOPE Antony van Leeuwenhoek (1632-1723)- Dutch draper- made 200 microscopes FIRST TEXT BOOK OF PATHOLOGY Jean Fernet (1497-1558)Frenchman Giovanni Battista Morgagni (1682-1771)-modern Pathology- Seats and causes of disease in 5 volumescorrelation of lesions with the symptoms FATHER OF HISTOLOGY Marei-Farancois Xavier Bichat (1771-1802)Frenchman – body composed of 21 tissues FATHER OF IMMUNOLOGY Edward Jenner (1749-1823)- Englishmandiscovered vaccination Material from cowpox lesions could be used to protect small pox in humans ESTABLISHMENT OF FIRST VETERINARY SCHOOL Jacques Labessie De Solleysel (1617-1680) – Complete book on veterinary medicine Claude Bourgelat (17121779) – lawyer – book on equine medicine January 1, 1762 in Lyon, FIRST EXPERIMENTAL PATHOLOGIST John Hunter (1728-1793) – Scotch- Blood, inflammation, gunshot wounds, monograph “Venereal Disease”- Syphilis Treponema pallidum Julius Cohnheim (1839-1884) – German - Inflammation CELLULAR PATHOLOGY Johannes Mueller (1801-1858)German- used microscope to study tissues Rudolph Virchow (1821-1902)- Book “Cellular Pathology” . Father of Cellular Pathology or Father of Modern Pathology. Most of the terms used in pathology are coined by him GERM THEORY OF DISEASE Louis Pasteur (1822-1895) – France – germ theory of disease Robert Koch (1843-1910) DISCOVERY OF PHAGOCYTOSIS Elie Metchnikoff (1845-1916) - Russian DISCOVERY OF LYSOSOMES Christian de Duve (1955) in Belgium- fractional centrifugation Novikoff Confirmed presence of lysosomes by EM. DISCOVERY OF PRIONS Proteinaceous infective particle (Prion) Lack nucleic acid(RNA, DNA) No inflammatory or immune reponse Resistant to UV light & disinfectants Cause tranmissible spongiform encephalopathies (TSE’s)