i ntroduction to p athology dr. temur ahsan khan path 303general pathology4(3-2)
DESCRIPTION
D ISEASE 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.TRANSCRIPT
INTRODUCTION TO PATHOLOGY
Dr. Temur Ahsan Khan
PATH 303 General Pathology 4(3-2)
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.
PATHOGNOMONIC 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).
LesionLesion
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.
Pathological changes
Functional
Structural
Moderate
Time
DIAGNOSIS 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.
PrognosisPrognosis • It is the estimation of the clinician or pathologist
regarding the expected outcome of disease like favorable, guarded or grave ete
EtiologyEtiology 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. Exogenous (Environmental or extrinsic factors) 2. 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
(a) Adhere to host cells(b) Invade the cells and tissues(c) To deliver toxins that damage the cells and
toxins Bacterial adherence to host cellsMechanisms- Adhesins, fibrils and fimbrae
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 ANATOMYAntanio 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)- Englishman-
airtree Marcello Malpighi (1628-1694)- Italian-
capillaries 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 PATHOLOGYJean Fernet (1497-1558)-Frenchman
Giovanni Battista Morgagni (1682-1771)-modern Pathology- Seats and causes of disease in 5 volumes- correlation 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)- Englishman-
discovered 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 (1712-1779) – lawyer – book on equine medicineJanuary 1, 1762 in Lyon, France
FIRST EXPERIMENTAL PATHOLOGISTJohn Hunter (1728-1793) – Scotch- Blood, inflammation, gunshot wounds, monograph “Venereal Disease”- SyphilisTreponema pallidum
Julius Cohnheim (1839-1884) – German - Inflammation
CELLULAR PATHOLOGYJohannes 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 PRIONSProteinaceous infective particle (Prion)
Lack nucleic acid(RNA, DNA)No inflammatory or immune reponse
Resistant to UV light & disinfectants
Cause tranmissible spongiform encephalopathies (TSE’s)