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

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

3. 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

4. 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.

5. 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

6. 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

7. 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

8. 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)

9. 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)..

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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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.)

17. 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

18. 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

19. 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.

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

21. 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

22. 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

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

24. 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

25. 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

26. 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

27. 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

28. -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.

29. 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