Pathology Introduction PDF

DR. Suad Mohamed Pathology L1 Definition: Pathology is the scientific study of disease. Pathos means - suffering Logos means – study Pathology is the bridging discipline involving both basic science and clinical practice and...

DR. Suad Mohamed Pathology L1 Definition: Pathology is the scientific study of disease. Pathos means - suffering Logos means – study Pathology is the bridging discipline involving both basic science and clinical practice and is devoted to the study of the structural and functional changes in cells, tissues, and organs that underlie disease SUBDIVISIONS OF PATHOLOGY Pathology It is divided in to : A. General Pathology is concerned with the basic reactions of cells and tissues to abnormal stimuli that underlie all diseases. B. systemic pathology= is the description of specific diseases as they effect individual organs or organ systems (e.g. appendicitis, lung cancer etc)  Cellular Pathology “All organ injuries start with structural or molecular alterations in cells” concept began by Rudolf Virchow in 1800's. Subcellular compartments: 1. Nucleus being the founder of modern-day 2. Mitochondria pathology 3. ER 4. Golgi apparatus 5. Lysosomes 6. Cytosol  The four aspects of a diseases process are: 1. Etiology (CAUSE): the cause of disease; genetic or acquired (e.g infectious, nutritional, chemical, physical, etc.) 2. Pathogenesis : the mechanisms or sequence of events leading from initiation of cell or tissue injury to disease development. 3. Pathological Changes: A- Morphological changes the structural alterations gross (detected by eye), biopsy (the removal and examination of tissue from the living body or autopsy or necropsy (post-mortem examination) and microscopy in cells or tissues B- Functional changes: pathophysiology 4. Clinical significance :_ the nature of the morphologic changes and their distribution in organs / tissues influence normal function and determine the clinical symptoms and signs, course and in addition to study of fate of disease (cure or complication or death of patient(  Causes of diseases Diseases can be causes by either genetic factors or environmental factors, or both factors Environmental Factors 1. Physical agents : Trauma, radiation, extremes temperature and electric power. 2. Chemicals : drugs, chemical products of home cleaners. Ex: cyanide, strong acids and alcohol cause damage in liver 3. Nutritional deficiencies and excesses: Iron deficiency anima, vitamins and elements essential proteins. Obesity, heart dis. , High blood pressure 4. Infections : - Virus: poliomyelitis - Bacteria: Diphtheria and tetanus - Fungal : candida - Protozoa : malaria and metazoa 5. Immunological factors : A. Hypersensitivity reaction :bronchial asthma B. Immunodeficiency : AIDS C. Autoimmunity: hypersensitivity reaction against self antigen  CELL ADAPTATION, CELL INJURY AND CELL DEATH Homeostasis : cells are able to maintain normal structure and function (e.g ion balance, pH, energy metabolism) in response to normal physiologic demands. When a cell is exposed to an injurious agent: the possible outcomes are: 1. The cell may adapt to the situation when adaptation is not possible, 2. They cell may acquire a reversible injury: removal of stress will result in complete structural and functional integrity to be restored 3. or The cell may obtain an irreversible injury & may die. The cell may die via one of two ways: either by necrosis or by apoptosis. Adpation processes: 1 - Hypertrophy, 2 - Atrophy, 3 - Hyperplasia 4 -Metaplasia 5 - Dysplasia  -1 Cellular Adaptation of g r o w t h 1- Hypertrophy Definition :Increase in cell size with subsequent increase in organ size it may be physiological or pathological physiological Causes of Hypertrophy: Increased functional demand or Hormonal stimulation e.g pregnant uterus, and muscle of athletes  pathological: cardiac muscle hypertrophy in hypertension/aortic valve Disease Hypertrophy of Uterus During Pregnancy: athletes  2- ATROPHY Definition :Decrease in the size of a cell or organ by loss of cell substances (both size and number) Causes: 1- Decreased workload due to immobilization 2- Denervation (loss of nerve supply) e.g. paralysis of a limb due to nerve injury or poliomyelitis. 3- Ischemia e.g. brain atrophy as an ageing phenomenon 4- Inadequate nutrition 5-Pressure 6- Loss of endocrine stimulation. Atrophic Brain Normal Brain Lead to- Decreased protein synthesis Increased protein degradation Bilateral Atrophy  3- HYPERPLASIA Definition: An increase in the number of cells in an organ or tissue, which may then have increased volume.(occur only in cells capable of division) physiology: 1-HORMONAL e. g. hyperplasia of the female breast epithelium at puberty or in pregnancy. 2-COMPENSATORY: hyperplasia occurring following removal of part of an organ As e.g. Regeneration of the liver following hepatectomy or partial or a contralateral organ in paired organ as kidneys. Liver Left Normal breast Right Hyperplasia  Pathological Hyperplasia Seen in: - Endometrial Hyperplasia, Increased Hormone Stimulation(Estrogen), - Hyperplasia of the Prostate Gland: It is common in older age and is due to hyperplasia of both glandular and the stromal element -Thyroid Hyperplasia (Graves’ Disease): (auto antibodies) Goiter – thyroid hyperplasia  4 - Metaplasia (1) Definition: Metaplasia is a reversible change in which one mature adult cell type is replaced by another mature adult cell type. (2) Causes: - Changes in environment: e.g. Irritation by stones in excretory ducts of salivary gland, pancreas, or bile ducts lead to change from columnar epithelium to stratified squamous epithelium. - inflammation: e.g. In the habitual cigarettes smoker, the normal columnar ciliated epithelial cells of the trachea and bronchi are often replaced focally or widely by stratified squamous epithelial cells. - In chronic gastric reflux, the normal stratified squamous epithelium of lower esophagus may undergo transformation to columnar epithelium. Called Barrett’s Esophagus - Nutritional: vitamin A deficiency causing squamous metaplasia.  5-DYSPLASIA Atypical proliferative changes associated with atypical cytological changes that involve cell size, shape, and organization. The increased proliferative activity produces greater amounts of DNA and thus the nuclei appear more hyperchromatic. ; Mild dysplasia Moderate dysplasia Marked dysplasia Premalignant change e.g: DYSPLASIA IN THE CERVIX Hyperplasia and Metaplasia are not premalignant changes, however they are “fertile fields” for Dysplasia which is a premalignant change