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Pathology is the study and diagnosis of Disease through examination of Organs , Tissues , Cells and Bodily Fluid s. The term encompasses both the Medical Specialty which uses tissues and body fluids to obtain clinically useful information, as well as the related Scientific study of disease processes. HISTORY The histories of both experimental and medical pathology can be traced to the earliest application of the s or Surgeon s. Like other medical fields, pathology has become more specialized with time, and most pathologists today do not practice in other areas of medicine. Origins of gross pathology The concept of studying disease through the methodical dissection and examination of diseased bodies, organs, and tissues may seem obvious today, but there are few if any recorded examples of true (1804-1878), who is said to have performed 20,000 autopsies, and supervised an additional 60,000, in his lifetime. {Link without Title} Karl von Rokitansky at Whonamedit.com Origins of microscopic pathology The German physician (1839-1884) combined Histology techniques with experimental manipulations to study Inflammation , making him one of the earliest Experimental Pathologists . Cohnheim also pioneered the use of the frozen section; a version of this technique is widely employed by modern pathologists to render diagnoses and provide other clinical information intraoperatively. {Link without Title} Jewish Encyclopedia entry on Julius Cohnheim Modern experimental pathology As new research techniques, such as Electron Microscopy , Immunohistochemistry , and Molecular Biology have expanded the means by which biomedical scientists can study disease, the definition and boundaries of investigative pathology have become less distinct. In the broadest sense, nearly all research which links manifestations of disease to identifiable processes in cells, tissues, or organs can be considered Experimental Pathology . {Link without Title} Mission of the American Society for Investigative Pathology PATHOLOGY AS A SCIENCE Pathology is a broad and complex Scientific Field which seeks to understand the mechanisms of injury to Cells and Tissues , as well as the body's means of responding to and repairing injury. Disease processes may be incited or exacerbated by a variety of external and internal influences, including Trauma , Infection , Poison ing, Loss Of Blood Flow , Autoimmunity , inherited or acquired Genetic Damage , or errors of Development . One common theme in pathology is the way in which the body's responses to injury, while evolved to protect health, can also contribute in some ways to disease processes.1 Elucidation of general principles underlying pathologic processes, such as cellular adaptation to injury, cell death, inflammation, tissue repair, and neoplasia, creates a conceptual framework with which to analyze and understand specific human diseases. Adaptation to injury Cells and tissues may respond to injury and stress by specific mechanisms, which may vary according to the cell types and nature of the injury. In the short term, cells may activate specific genetic programs to protect their vital Protein s and Organelle s from Heat Shock or Hypoxia , and may activate DNA Repair pathways to repair damage to Chromosomes from Radiation or chemicals. Hyperplasia is a long-term adaptive response of Cell Division And Multiplication , which can increase the ability of a tissue to compensate for an injury. For example, repeated irritation to the skin can cause a Protective Thickening due to hyperplasia of the Epidermis . Hypertrophy is an increase in the ''size'' of cells in a tissue in response to stress, an example being hypertrophy of Muscle Cells in the Heart in response to increased resistance to blood flow as a result of Narrowing Of The Heart's Outflow Valve . Metaplasia occurs when repeated damage to the cellular lining of an organ triggers its replacement by a different cell type. Cell death Necrosis is the irreversible destruction of cells as a result of severe injury in a setting where the cell is unable to activate the needed metabolic pathways for survival or orderly degeneration. This is often due to external pathologic factors, such as toxins or loss of oxygen supply. Milder stresses may lead to a process called ''reversible cell injury'', which mimics the cell swelling and vacuolization seen early in the necrotic process, but in which the cell is able to adapt and survive. In necrosis, the componants of degenerating cells leak out, potentially contributing to inflammation and further damage. Apoptosis , in contrast, is a regulated, orderly degeneration of the cell which occurs in the settings of both injury and normal physiological processes. Inflammation Inflammation is a particularly important and complex reaction to tissue injury, and is particularly important in fighting Infection . Acute Inflammation is generally a non-specific response triggered by the injured tissue cells themselves, as well as specialized cells of the Innate Immune System and previously developed Adaptive Immune mechanisms. A localized acute inflammatory response triggers vascular changes in the injured area, recruits Pathogen -fighting Neutrophil s, and begins the process of developing a new adaptive immune response. Chronic Inflammation occurs when the acute response fails to entirely clear the inciting factor. While chronic inflammation can lay a positive role in containing a continuing infectious hazard, it can also lead to progessive tissue damage, as well as predisposing (in some cases) to the development of Cancer . Tissue repair Tissue repair, as seen in Wound Healing , is triggered by inflammation. The process may proceed even before the resolution of a precipitating insult, through the formation of Granulation Tissue . Healing involves the proliferation of Connective Tissue cells and Blood Vessel -forming cells as a result of hormonal growth signals. While healing is a critical adaptive response, an aberrent healing response can lead to progressive Fibrosis , contractures, or other changes which can compromise function. Neoplasia Neoplasia , or "new growth," is a proliferation of cells which is independent of any physiological process. The most familiar examples of neoplasia are Benign Tumors and Cancer s. Neoplasia results from genetic changes which cause cells to activate genetic programs inappropriately. Dysplasia is an early sign of a neoplastic process in a tissue, and is marked by persistance of immature, poorly differentiated cell forms. Interestingly, there are many similarities in the gene pathways activated in cancer cells, and those activated in cells involved in wound healing and inflammation. PATHOLOGY AS A MEDICAL SPECIALTY Physicians who practice pathology diagnose and characterize disease in living patients by examining biopsies and other specimens. For example, the vast majority of cancer diagnoses are made or confirmed by a pathologist. Pathologists may also conduct autopsies to investigate causes of death. The medical practice of pathology grew out the tradition of investigative pathology, and many of the Academic leaders in pathology today are accomplished in both basic science research and diagnostic practice. However, as with other specialties in Medicine , most modern physician-pathologists are employed in full-time practice, and do not perform original research. Pathology is a unique medical specialty in that pathologists typically do not see Patient s directly, but rather serve as consultants to other physicians (often referred to as "clinicians" within the pathology community). However, in the United States and in many other countries, pathologists receive the same doctorate training, and undergo the same medical licensure process as other physicians. Pathology is a diverse field, and the organization of subspecialties within pathology vary between nations. Anatomical Pathology See Also: Anatomical pathology Anatomical Pathologists diagnose disease and gain other clinically significant information through the examination of tissues and cells. This generally involves Gross and Microscopic visual examination of tissues, with special stains and immunohistochemistry employed to visualize specific proteins and other substances in and around cells. More recently, anatomical pathologists have begun to employ molecular biology techniques to gain additional clinical information from these same specimens. Anatomic pathologists serve as the definitive diagnosticians for most cancers, as well as numerous other diseases.
Clinical pathology See Also: Clinical pathology Clinical Pathology , also known as Laboratory Medicine , is the medical specialty concerned with diagnosing diseases based on the analysis of body fluids, such as plasma, urine, stool, respiratory or mucosal secretions, inflammatory exudates, and Pleural , pericardial, Peritoneal , Synovial , or cerebrospinal fluid. The practice of clinical pathology is centered around the clinical laboratory. In modern clinical laboratories, many routine studies are largely automated. The clinical pathologist is responsible for overseeing the work of laboratory Technician s, performing quality assurance to assure the validity of test results, performing interpretations of more complex studies, and serving as a consultant to clinicians so that the most appropriate studies can be performed for the diagnosis or assessment of an individual patient's condition. In some areas, non-pathologists, such as other physicians or Ph.D.'s may run clinical labs and perform functions within those specific labs which are similar to the role of a board-certified clinical pathologist. Sub-specialties within clinical pathology include the following:
Dental pathology In the United States, subspecialty-trained doctors of Dental surgery (D.D.S), rather than medical doctors, can be certified by a professional board to practice Dental Pathology . TRAINING OF MEDICAL PATHOLOGISTS Pathology in the United States In the United States, pathologists are , and Clinical Pathology , each of which requires separate board certification. Many pathologists seek a broad-based training and become certified in both fields. These skills are complementary in many hospital-based private practice settings, since the day-to-day work of many clinical laboratories only requires the intermittent attention of a physician. Thus, pathologists are able to spend much of their time evaluating anatomic pathology cases, while remaining available to cover any special issues which might arise in the clinical laboratories. Pathologists may pursue specialised fellowship training within one or more sub-specialties of either anatomic or clinical pathology. Some of these sub-specialities permit additional board certification, while others do not. {Link without Title} Homepage of the American Board of Pathology Pathology in the United Kingdom In the UK pathologists are Medical Doctor s registered with the UK General Medical Council . They will have completed an undergraduate medical education which in most countries lasts 4-6 years. The training to become a pathologist is under the oversight of the Royal College Of Pathologists . Typically a one year training attachment is followed by an aptitude test. This is followed by further specialist training in surgical pathology, cytopathology, and post mortem pathology. There are two examinations run by the Royal College Of Pathologists termed Part 1 and Part 2. The Part 2 examination is designed to test competence to work as an independent practitioner in pathology and is typically taken after 5 years specialist training. All post-graduate medical training and education in the UK is overseen by the Postgraduate Medical Education and Training Board. It is possible to take a specialist part 2 examination in paediatric pathology or neuropathology. It is possible to take a special diploma in dermatopathology or cytopathology, recognising additional specialist training and expertise. NON-HUMAN PATHOLOGY Veterinary Pathologists are veterinary practitioners who specialise in the diagnosis and characterization of veterinary diseases through the examination of animal tissue and body fluids. Veterinary pathologists are veterinarians with advanced training (board certification or Ph.D.) in either diagnostic pathology or research into the biological processes underlying disease (pathobiology). Diagnostic veterinary pathologists are further subcategorized as either anatomical pathologists or clinical pathologists. Clinical pathologists examine specimens such as blood, excretions or biopsy material to diagnose disease in living animals. Anatomical pathologists utilize post mortem examinations of dead animals to arrive at a diagnosis. Post mortem examinations entail a necropsy (an animal autopsy), histopathologic (microscopic) study of tissue specimens collected at the necropsy and sometimes specialized studies (radiographic, toxicologic, etc.) Plant Pathologists are specialized scientists who investigate the causes of diseases in plants. NOTES SEE ALSO EXTERNAL LINKS
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