Translated literally, pathology is the study (logos) of suffering (pathos). As a science, pathology focuses on the structural and functional consequences of injurious stimuli on cells, tissues, and organs and ultimately the consequences on the entire organism.

 

Traditionally the study of pathology is divided into general pathology, and special or systemic pathology. The former is concerned with the basic reactions of cells and tissues to abnormal stimuli that underlie all diseases. The latter examines the specific responses of specialized organs and tissues to more or less well-defined stimuli.

 

The four aspects of a disease process that form the core of pathology are (1) its cause (etiology), (2) the mechanisms of its development (pathogenesis), (3) the structural alterations induced in the cells and organs of the body (morphologic changes), and (4) the functional consequences of the morphologic changes (clinical significance).

 

1.Etiology or Cause. There are two major classes of etiologic factors: genetic and acquired (infectious, nutritional, chemical, physical, etc.). Knowledge or discovery of the primary cause remains the backbone on which a diagnosis can be made, a disease understood, or a treatment developed. But the concept of one cause leading to one disease- developed largely from the discovery of specific infectious agents as the causes of specific diseases- is no longer sufficient. Although it is true that there would be no malaria without malarial parasites, no tuberculosis without tubercle bacilli, and no gout without a derangement in urate metabolism, not all individuals infected with these organisms or born with the metabolic abnormality develop the disease, or develop it at the same rate and with the same severity. Genetic factors clearly affect environmentally induced maladies, and the environment may have profound influences on genetic diseases.

 

 

2.Pathogenesis. Pathogenesis refers to the sequence of events in the response of the cells or tissues, or the whole organism, to the cause ? from the initial stimulus to the ultimate expression of the manifestations of the disease. The study of pathogenesis remains one of the main domains of the science of the pathology. Even when the initial infectious or molecular cause is known, it is many steps removed from the expression of the disease. For example, to understand gout is to know not only the molecular pathways of uric acid metabolism, but also the biochemical and morphologic events leading to a painful toe or a kidney stone. Although from the late nineteenth century up to the 1950s, pathology was largely limited to the study of the morphologic consequences of disease, chemical, immunologic, and molecular mechanisms clearly underlie the morphologic changes and these, fortunately, have become the domain of modern pathology.

 

 

3.Morphologic changes. The morphologic changes refer to the structural and associated functional alterations in cells or tissues that are either characteristic of the disease or diagnostic of the etiologic process.

 

 

4.Functional Derangements and Clinical Significance. The nature of the morphologic changes and their distribution in different organs or tissues influence normal function and determine the clinical features (symptoms and signs), or course, and prognosis of the disease.