Introduction to pathology & causes of diseases H.A. MWAKYOMA, MD

WHAT IS PATHOLOGY Pathology is a study of diseases. The study provides understanding of the processes (their causes, clinical effects etc).

Pathology -as a science- focuses on mechanisms by which cells and tissues are injured, on structural and functional consequences of injurious stimuli on cells, tissues, and organs, finally on the entire organism - it is a morphologic discipline- describes pathological morphologic findings in tissues and cells

Pathology -as a medical discipline- deals with a performance and an interpretation of laboratory procedures, leading to diagnosis -these include many diagnostic and investigative techniques and concern with interpretation of laboratory procedures- examples: histologic examination of surgical biopsies, cytological examination of smears and FNA (fine needle aspirates), bone marrow smears, etc.

Pathology Two main fields of pathology as medical discipline: (1) surgical pathology -deals with interpretation of histological examination of tissues and organs removed in surgery from living patients (2) autopsy pathology -is concerned with examination of gross, macroscopic and histological changes in diseases studied in dead persons

Pathology Forensic pathology - is performed and practised separately from pathology- in faculty hospitals, both disciplines are closely related in small and district hospitals - main task is to determine whether death was due to natural or unnatural causes, such as caused by accident, other person, murders etc. -in large medical centers and faculty hospitals- pathologists usually subspecialize in a distinctive discipline, i.e. cytology, hematopathology, surgical pathology, gynecological pathology

Pathology surgical pathology report-diagnosis based on microscopic and gross examination of surgicals autopsy report-diagnosis of disease and cause of death, describes morphologic changes, studies pathogenetic consequencies

Pathology The study of pathology is divided into: general pathology- concerns with basic reactions of cells and tissues to abnormal stimuli that are common for a group of diseases or that underlie all diseases or groups of diseases special pathology- examines specific responses of specialized tissues and organs to pathologic stimuli oncologic pathology- deals with neoplastic processes (tumours)

DEFINITIONS OF BASIC ASPECTS OF DISEASE PROCESS Pathology medical discipline which provides the link between basic biological sciences and the practice of medicine. Pathology is a logical, scientific basis of medicine is the study of changes which occur in cells and tissues as a result of either genetic inborn or environmental damage, is a study of diseases the study provides understanding of the processes (their causes, clinical effects etc)..

Pathology -in broader terms, pathology means also study of the diseases, their causes, prevention and classification

Disease Disease- is defined as a physiological or psychological dysfunction. -it can be caused by obvious structural abnormalities, or may be less well defined-without obvious morphological damage, such as in anorhexia nervosa- mental anorhexia

Diseases All diseases have certain aspects which can form the basis for classification- these include -pathology focuses on the following different aspects of disease -epidemiology (occurrence and incidence of d.) -etiology (causes of disease) -pathogenesis (mechanisms of disease) -morphology of the tissue changes - clinical significance and consequencies

Disease 1.epidemiology-provides a wider context for the study, classification, and diagnosis of diseases -epidemiological data are important -for providing informations about causes of diseases. -for identifying risk factors -for providing adequate health care, and planning disease prevention, epidemiology records data about .incidence-number of new cases occurring in a defined population over a defined time period

Disease prevalence-number of cases found in a defined population at a stated time morbidity-number of diseased persons in a given locality, nation etc. and mortality-number of deaths to the population

Disease 2.etiology studies causes of disease diseases result from the interaction between individuals and their environment -the other diseases result from an environmental factors acting in conjunction with a genetic predisposition -in some instances the underlying cause of a disease is obscure-idiopathic, spontaneous, essential

classification of diseases classification of diseases - based on the etiologic factors, diseases can be classified to two categories -congenital- present at birth, even though they are sometimes recognized later -acquired- occur only later after births (infectious, nutritional, chemical, physical, radiation injury etc.)

Disease 3.pathogenesis- etiopathogenesis -refers to the sequence of events in the response of the cells, tissues, organs to the injurious stimuli that may lead to a disease -describes mechanisms of development of disease -study of pathogenesis remains a main domain of the scientific pathology

Disease 4.morphological changes -structural alterations induced in cells and tissues -refers to the structural alterations of cells or tissues that are either characteristic or diagnostic of a disease -there are gross/ macroscopic findings and histological microscopic findings

Disease 5.clinical significance -functional consequencies of morphologic changes, as observed clinically -morphologic structural changes of cells, tissues and organs are related to functional disorders, morphologically altered tissues do not provide normal functions, and these consequent pathologic functions are studied in details in many clinical disciplines- pathology provides basic information with respect to clinical outcome, prognosis, etc.

Disease -symptoms- features of illness that are noticed by patients -signs- clinical manifestation of the disease which are recognized by clinicians

Type Basis Examples Congenital Genetic Hemophilia A (absence of clotting factor VIII) Non-genetic Intrauterine rubeolla infection (measles) leads to deafness/blindness in the fetus Acquired Inflammatory Dermatitis (eczema, inflammation of the skin) Vascular Atherosclerosis Growth and proliferation disorders Tumors Metobolic Gout (deposition of uric acid crystals in joints and soft tissues Degenerative Alzheimer disease-demensia Infective / Drug induced tbc / Renal failure

THE ROLE OF PATHOLOGY IN DIAGNOSTIC PROCESS: FROM CLINICAL REASONING TO MOLECULAR BIOLOGY. patients present with symptoms and clinical examination reveals signs which suggest a diagnosis -examination of various specimens in pathology laboratories helps to establish and confirm diagnosis, and monitor the treatment Diagnosis is the act of identifying a disease in an individual patient and is based on clinical history, physical examination and pathology investigation

Diagnosis Diagnosis involves skills and laboratory tests Special pathology techniques are used Special stains, immunohistochemistry and molecular biology techniques are routinely used

The role of pathologist: Looking at samples of tissues (biopsies) Using the range of special laboratory techniques Histology Autopsy Special stains Immunohistochemistry Electron microscopy Molecular biology techniques

METHODS IN PATHOLOGY Diagnostic and investigative techniques used in pathology routine histological techniques –fundamental for histopathologic diagnosis – these techniques use different coloration of cells and tissues and cell components using different staining methods

most commonly used staining methods- hematoxylin and eosin stain- combination of haematoxylin and eosin remains the gold standard, method used for majority of histopathologic diagnoses- method is now over 100 years old haematoxylin- is natural product of blue colour, is used mostly for staining the nuclei- shows general morphology of a tissue -eosin- the most frequently used partner stain because it is easy to stain, and its red colour contrasts well with blue colour of haematoxylin- eosin stains cytoplasm

special stains- HE is important as a general staining procedure but it is sometimes necessary to use other staining procedures in order to demonstrate more selectively the particular tissue components -connective tissue components, such as collagens, muscle fibers can be demonstrated by Van Gieson stain or trichrome stains reticulin (type III collagen) can be shown by silver impregnation technique

-basement membrane components (such as type IV collagen, laminin) are well demonstrated with the periodic acid-Schiff (PAS) method, silver impregnation according to Gomory, etc.

Recommended Reading Material 1. Cotran RS, Kumar V and Collins T. Robbin: Pathologic basis of Diseases, WB Saunders, Philadelphia. 2. Klatt EC and KumarV: Robbins Review of Pathology. W. B. Saunders, Missouri. 3. Harsh Mohan: Textbook of Pathology