Introduction to pathology & causes of diseases

1. INTRODUCTION TO PATHOLOGY
& CAUSES OF DISEASES

2. PATHOLOGY CLASSIFICATION
1. General pathology:
• The study of general reactions of cells and tissues to insults and injuries that
are basic to all disease processes.
2. Systemic pathology:
• The study of specific disease processes or reactions as they affect particular
organs or organ systems e.g. CVS, CNS, GIT…..etc.

3. APPLIED PATHOLOGY
1. Anatomic pathology:
a. Necropsy pathology
b. Surgical pathology
c. Cytopathology
2. Clinical pathology.
3. Forensic pathology.

4. 1. Anatomic Pathology:
• Making diagnosis by examining tissues.
1. Necropsy pathology:
• Examination of tissues excised from cadavers in an
effort to establish the cause of death.
• This is called “autopsy”.
2. Surgical pathology:
• Examination of tissues excised from living patients in
an effort to establish a specific diagnosis.
• This is called “biopsy”.
3. Cytopathology:
• The microscpocic study of exfoliated cells within body
fluids.

5. 2. Clinical pathology:
• Analysis of various specimens (whole blood, serum, plasma, urine, stool, CSF, sputum,
etc.) from patients to facilitate diagnosis, direct therapeutic approach and monitor
therapy.
3. Forensic pathology:
• Subspecialty dealing with medicolegal investigation of death.

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

7. 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

8. 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.

9. 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

10. 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

11. 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

12. 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)

13. 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)..

14. PATHOLOGY
• -in broader terms, pathology means also study of the
diseases, their causes, prevention and classification

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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.)

21. 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

22. 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

23. 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.

24. DISEASE
• -symptoms- features of illness that are noticed by
patients
• -signs- clinical manifestation of the disease which
are recognized by clinicians

25. 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

26. 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

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

28. 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

29. 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

30. 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-

31. • 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

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

33. 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