Pathology Lecture Notes PDF - Introduction & Cellular Bases of Diseases

Pathology an Introduction By Dr. Hemn Hassan Othman, MSc, PhD, PD, Pathology Department of Basic Sciences College of Pharmacy, UOS 2023-2024  Pathology The term “pathology” is derived from the Greek words pathos which means disease and logy which mea...

Pathology an Introduction By Dr. Hemn Hassan Othman, MSc, PhD, PD, Pathology Department of Basic Sciences College of Pharmacy, UOS 2023-2024  Pathology The term “pathology” is derived from the Greek words pathos which means disease and logy which means study, thus pathology is a branch of biological sciences that deals with the study of all structural and functional abnormalities (at the level of cells, tissues, organs and body fluids) that take place as a result of a disease. 2023-11-06 2 Pathology is considered a vital link between basic sciences (anatomy, physiology, biochemistry, pharmacology…….etc) and clinical sciences (internal medicine, surgery, neurology, dermatology, theriogenology……….etc). 2023-11-06 3 2023-11-06 4 Professional divisions of pathology In academic studies, pathology divide into (medical or comparative pathology), while professionally pathology is divided into two major divisions: 1. Anatomic pathology which deals with the study of the disease effects in cells, tissues and organs. 2. Clinical pathology which deals with the study of the disease effects in body fluids and secretions (blood, urine, milk…… etc.) using certain laboratory methods. 2023-11-06 5 Major branches of Anatomic Pathology 1. General pathology which deals with the study of the common basic changes in all tissues as a result of a disease, e.g., cell injury, necrosis, inflammation and neoplasm. 2. Systemic pathology which deals with the study of morphological changes in tissues and organs of a particular system as a result of a disease e. g., pathology of respiratory system, pathology of digestive system, pathology of nervous system…etc. 3. Special pathology which deals with the application of the basic changes learned in general pathology to the various specific 2023-11-06 diseases e.g Diabetes, atherosclerosis etc. 6 4. Diagnostic Pathology (Histopathology) which deals with the study of tissue abnormalities using gross and microscopic examination of biopsy samples. Biopsy: The biopsy is a tissue sample obtained surgically from a living body in order to be examined grossly and microscopically (by a pathologist) to help in establishing the diagnosis of the pathological conditions. 5. Cytopathology which deals with the study of cellular changes, using cytological samples (e.g Vaginal swab, Laryngeal swab). 6. Post-mortem pathology which deals with pathological examination of human cadaver after death. It is also known as autopsy or necropsy. 2023-11-06 7 7. Forensic pathology: It is the subspecialty of pathology that focuses on the medico-legal investigation of the cause of a sudden or unexpected death by examination of a dead body. 9. Physiological pathology (Pathophysiology) which deals with the study of alterations in the functions of organs and systems of the body as a result to a disease. It is also known as pathophysiology; e.g., pathophysiology of ulcer, diarrhea, atherosclerosis…..etc. 10. Experimental pathology: It is the study of diseases that have been created or induced experimentally to analyze the structural & functional abnormalities in tissue to better understand the mechanism of underline diseases. Usually laboratory animals used in experimental pathology (Rabbits, Rats, Mice….ect 2023-11-06 8  Disease and Disease Circumstances Disease The disease is a condition in which an individual shows a morphological, biochemical and/or physiological deviation from the normal status. Etiology The term etiology refers to the science that deals with the causes or origin of the disease or the factors that produce or predispose toward a certain disease or disorder. Lesions The term “lesions” refers to abnormal (pathological) structural and functional changes that occur in body during a particular disease. This word is perhaps the most commonly used word in pathology. 2023-11-06 9 Macroscopical (gross) lesions: Abnormality in the tissue can be described grossly or by the naked eye including location, color, size, shape, consistency & appearance of the cut surface. Microscopical lesions: Abnormal morphological changes described under the microscope, lesions need quantification by using some general terms like mild, moderate, severe or critical. 2023-11-06 10 Pathogenesis It is defined as the step by step developmental process from the beginning of the disease to its termination, or the mechanism by which the disease is developed. Pathogenicity The term pathogenicity refers to the ability of a pathogen (usually microbial pathogens) to cause disease, e.g.: 1. The highly pathogenic influenza A virus subtype H5N1 which has caused serious disease outbreaks in poultry and human. 2. The nonpathogenic strains of Escherichia coli (E. coli) which live naturally in the large intestine of human and do not2023-11-06 cause disease. 11 Symptom The term symptom refers to any evidence of a disease as told by the patient (in case of human being). Sign The term sign refers to any evidence of a disease detectable to a clinician (can be observed by the clinician). Diagnosis The term diagnosis refers to the art or act of identifying a particular disease from its signs and symptoms. Prognosis It is the prediction of the probable outcome of a disease. 2023-11-06 12 Summary: 1/ Pathology is the study of what happened & how, the lesion is what & the sequence of events from the point of which the lesion began through its entire development (pathogenesis) is how. 2/ It is necessary to know the pathogenesis of lesions in order to make a rational judgment for treatment, control & prevention of diseases. 2023-11-06 13  Cellular Basis of Diseases Cellular response to stress: Every cell in the living body is in balance with it’s environment it is considered to be in a homeostatic balance or “ steady state”. There are a variety of systems protect cell integrity, i.e. cell membrane, phagocytosis, excretion of exogenous chemicals (bile, urine), host defense mechanisms (inflammation, immune system), system of repair like (antioxidants, DNA-repair enzymes). If more excessive external stimuli occur, the cell may be able to adapt to the changes, i.e. hypertrophy (increased workload), atrophy (decrease workload). If the limits of adaptative capability are exceeded, or when the protective systems are overwhelmed, the cell is "injured". The injury of the cell may range from mild and fully reversible to severe and lethal (non reversible).  Types of cell injury Cell injury is divided into: 1. Reversible cell injury 2. Irreversible cell injury Reversible cell injury It is a type of cell injury in which the pathological changes will regress and disappear when the injurious agent is removed and the cells will return to normal morphological and functional status. Irreversible cell injury It is a type of cell injury which occurs when the injurious agent persists or when it is severe from the beginning. At first the injury is reversible, but later it reaches the point of no return, where it becomes irreversible. 2023-11-06 16 2023-11-06 17 Point of no return  It is the precise moment of transition from reversible to irreversible cell injury.  At this point, no adaptation can save the cell and the progression to cell death is inevitable (unavoidable). 2023-11-06 18 2023-11-06 19 For example, If the blood supply to a portion of the heart musculature is cut off for few minutes and then restored; the affected myocardial cells will sustain reversible injury, i.e., after restoration of the blood it will recover and function normally (as in mild cases of angina pectoris). But if the cessation of blood supply continues from 30 to 60 minutes and then restored, the affected myocardial cells will suffer from irreversible injury (Cell Death). 2023-11-06 20 2023-11-06 21 2023-11-06 22  Cell death Two phenomena characterize irreversibility 1. Inability to reverse mitochondrial dysfunction. 2. Development of profound disturbances in membrane function. 2023-11-06 23 Classification of cell death 1) Necrosis Result of catastrophic injury to the mechanisms that maintain cell integrity 2) Apoptosis Result of genetically determined cell-death (programmed cell death). 2023-11-06 24 2023-11-06 25 2023-11-06 26