General Pathology.PDF

General Pathology DR Sara Hassan MBBS U of K MD of Clinical Pathology U of K Objectives: Define Pathology, aetiology, pathogenesis, morphology, and clinical significance of disease. List techniques for staining pathologic specimens Laboratory Tests. What is Patholog...

General Pathology DR Sara Hassan MBBS U of K MD of Clinical Pathology U of K Objectives: Define Pathology, aetiology, pathogenesis, morphology, and clinical significance of disease. List techniques for staining pathologic specimens Laboratory Tests. What is Pathology? Pathology is literally the study (logos) of suffering (pathos). It is a 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. Basic science Clinical practice Pathology  The study of the essential nature of disease, including symptoms/signs, pathogenesis, complications, and morphologic consequences such as structural and functional alterations in cells, tissues, and organs.  The four aspects of a disease process that form the core of pathology are its cause (etiology), the mechanisms of its development (pathogenesis), the structural alterations induced in the cells and organs of the body (morphologic changes), and the functional consequences of the morphologic changes (clinical significance). Etiology or Cause There are two major classes of etiologic factors: 1. Intrinsic or genetic 2. Acquired- environmental (e.g., infectious, nutritional, chemical, physical). Pathogenesis Pathogenesis refers to the sequence of events in the response of cells or tissues to the etiologic agent, from the initial stimulus to the ultimate expression of the disease. The study of pathogenesis remains one of the main domains of pathology.  For example, to understand cystic fibrosis is to know not only the defective gene and gene product, but also the biochemical, immunologic, and morphologic events leading to the formation of cysts and fibrosis in the lung, pancreas, and other organs. Morphologic Changes Morphologic changes of the disease process include both gross changes and microscopic changes. Refer to the structural alterations in cells or tissues that are either characteristic of the disease or diagnostic of the etiologic process.  The practice of diagnostic pathology is devoted to identifying the nature and progression of disease by studying morphologic changes in tissues and chemical alterations in patients. Functional Derangements and Clinical Manifestations The clinical significance of a disease relates to its signs and symptoms, disease course including complications, and prognosis.  In light microscopic examination of tissue, hematoxylin and eosin (H&E) is considered the gold standard stain and is used routinely in the initial microscopic examination of pathologic specimens. The common denominator of the features is that hematoxylin binds nucleic acids and calcium salts, while eosin stains the majority of proteins (both extracellular and intracellular). Other histochemical stains (chemical reactions): Prussian blue (stains iron), Congo red (stains amyloid), Acid fast (Ziehl-Neelsen, Fite) (stains acid-fast bacilli), Periodic acid-Schiff (PAS, stains high carbohydrate content molecules), Gram stain (stains bacteria), Trichrome (stains cells and connective tissue), and Reticulin (stains collagen type III molecules). Laboratory Tests Chemical pathology Hematology Microbiology