INTRODUCTION TO PATHOLOGY What is pathology?

Greek words: Pathos= disease. Logos= study. It is the scientific study of disease into its: Nature Causes Mechanisms Effects.

It is essential for all would be doctors as well as general practitioners and specialists. Treatment of diseases and prevention all depend on knowing the underlying pathology in the patient. For the medical student, pathology a vital bridge between initial learning phase of pre-clinical sciences and final phase of clinical subjects.

What is disease ? It is the opposite of health. It is a state of discomfort to the body ( dis-ease). An abnormal variation in the structure and/or function of the body.

What is health ? Perceptions of health and disease vary between individuals and professional view points. Some define health as merely absence of signs or symptoms of disease. Sometimes people believe to be ill but have no measurable signs or symptoms of disease.

Conversely there are people who believe themselves to be well and have no symptoms. Yet on examination they are found with disease.

WHO definition of Health: A State of complete physical, mental and social well being and not merely absence of disease or infirmity”

A common term confused with disease is “illness”. While disease suggests an entity with a cause, illness is the subjective reaction of an individual to disease. Usually in the form of ; Symptoms ( complaints of patient) Physical signs ( elicited by the Physician).

The study of disease is done in pathology. The learning of illness will be done in the wards.

Terminology in Pathology The patient- the person affected by disease. The lesions- the characteristic changes in tissues and cells produced by disease. Pathological changes ( morphology): examination of diseased tissues: Naked eye appearance ( gross) Microscopic examination of tissues

Aetiology: What causes the variation from normal ? ie “Causal factors responsible for the lesions” Pathogenesis- the mechanism by which lesions are produced Functional implications of the lesion felt by patient:

Symptoms. Physical signs. The clinical significance of morphologic and functional changes + other investigations: What is wrong ?( DIAGNOSIS). What is going to happen ? (PROGNOSIS)

What can be done about it ? (TREATMENT). What can be done to avoid disease, complications and spread ? (PREVENTION)

Evolution of pathology. Concept of disease is old as life itself. A. From religious beliefs to rational approach. disease an outcome of curse or evil eye of spirits. To ward them off, priests through prayers and sacrifices used to invoke supernatural powers to please the gods.

The link between medicine and religion became so firmly established worldwide. The Greeks had Aesculapius as the god of healing. Later on came the concept of religious beliefs was replaced by philosophical and rational approach to disease by methods of observation.

Important people in medical history: Hippocrates ( 460-377 BC)- the father of medicine stressed study of patient’s symptoms Described methods of diagnosis Hippocratic oath- ethical conduct for doctors

Cornelius Celsus ( 53 BC-7 AD) Described the four cardinal signs of inflammation. Cladius Galen (130-200 AD). Illness resulted from imbalance between 4 body fluids: blood, lymph, black bile and biliary secretion.

Setbacks: Widespread and devastating epidemics reversed the process of rational thinking again. Supernatural concepts and divine punishment for sins dominated again. The belief was that life was due to influence of vital substance under the control of soul ( theory of vitalism).

Dissection of human body was strictly forbidden as that would mean hurting the “soul”.

Emergence of Anatomy and Morbid Anatomy This was then revival time of learning ( Renaissance period) Began in Italy and spread to rest of Europe in 15th century. Since there was freedom of thought, emphasis on philosophical and rationalistic attitudes strengthened.

Developments: Human Anatomy ; Dissection of the human body started by Vesalius Gabriel Fallopius described the human oviduct Fabricius discovered lymphoid tissue in intestine of birds.

Beginning of the study of Morbid anatomy: Giovanni Morgagni. Laid down the foundation of clinico-pathologic methodology in the study of disease. Performed 700 postmortems

Subdivisions of Pathology Human Pathology is divided into: 1. General Pathology: Studies processes without reference to specific organ systems. Designed to show fundamental reactions to disturbances in the body.

2. Systemic Pathology. Study of diseases pertaining to specific organs and body systems 3. Clinical Pathology- includes 1 & 2 above. It deals with problems of patient at the bed side. includes the study of laboratory tests useful for the diagnosis and management of patient.

With advancement of diagnostic tools, the speciality of pathology has come to include following sub-specialities: A. Histopathology & Morbid Anatomy (Anatomical Pathology). Subdivisions: i. Surgical Pathology ii. Forensic Pathology and autopsy iii. Cytopathology

B. Haematology & Blood Transfusion- diseases of the blood. C. Chemical Pathology( Clinical Chemistry)- metabolic disturbances of disease. D.Microbiology & medical immunology E. Parasitology & medical entomology

Why learn pathology? Most medical students are not going to be Pathologists!! Why should the medical curriculum include a course in pathology for the undergraduate ?

Pathology provides a clear account of the causes and the pathological changes which provide a logical explanation for the symptoms and signs and the biochemical changes.

How to learn pathology ? “ Pathology is no exception to the general rule that learning is dependant on the student’s own effort”. Lectures. Small group discussions Demonstrations and practicals Clinico-pathological conferences Autopsy.

mwisho