Pathopedia-India.com: Introduction to Pathology

Pathology is the study (logos) of structural and functional abnormalities (pathos). The knowledge of the pathologic changes is important to explain the different clinical features (signs and symptoms), course, and prognosis of the disease and also for the proper clinical care and therapy of the patient.

[More specifically, pathology may be defined as the - scientific study of the molecular, cellular, tissue, or organ system response to injurious agents or adverse influences].

Pathology has its roots deeply implanted in medical history.

The earlier observers, from Celsus (about 30 BC - AD 38) to Morgagni in the eighteenth century, based their work upon the naked-eye appearances of the diseased individuals and organs.

Only as the technique of microscopy improved was the Germanic School of Pathology, headed by Virchow (1821-1905), able to investigate changes at a cellular level.

He proposed that the basis of all disease is injury to the smallest living unit of the body, namely the cell.

More than a century later, clinical and experimental pathology was added to the Virchow's cellular pathology.

At the start of the nineteenth century, doctors and scientists had no idea that bacteria caused illness. It was Louis Pasteur, who first made this link. In France, Pasteur, using the microscope, laid the foundation of the science of bacteriology.

Later on the German dye industry enabled Robert Koch, Paul Ehrlich, and Gerhard Domagk to extend this knowledge and open the era of chemotherapy.

German chemical industry was manufacturing many synthetic coal tar dyes. Robert Koch was able to use these dyes to stain and to see invisible microbes. He identified the germs that caused anthrax, tuberculosis and cholera.

Advances in pathology thus have been closely related to advances in technology. This in no way belittles the effort of inspired experimenters like Edward Jenner, who in England pioneered the way to active immunization.

Nowadays technological advances are occurring so rapidly that it has become difficult to have a working knowledge of all the methods that are available. Utilizing all these complex techniques and along with investigators of different disciplines, the knowledge of pathology advances rapidly.

In 21^st century, pathology has undergone changes from a visual, descriptive morphology to one defined in terms and interpreted in molecular basis.

Pathology is considered in four headings:

Etiology or cause of the disease:

In 2500 BC, illness was thought to be due to patient’s own fault (for having sinned) or the making of outside agents, such as bad smell, cold, evil spirits or gods

In modern terms two major etiologic factors are intrinsic (genetic) or acquired (infective, nutritional, chemical and physical).

Pathogenesis:

Pathogenesis is the sequence of changes from the initial change after injury to the ultimate expression of the disease.

Morphological changes:

It refers to gross and microscopic changes of the tissues or organs in thedisease. It often signifies the etiology of the disease.

Pathophysiology:

This refers to functional changes due to morphological alteration in the disease and is dependent on the nature and distribution of lesions in different organs.