Pathology is the scientific study of disease, encompassing both the structural and functional changes in cells, tissues, and organs. It includes various sub-disciplines such as clinical pathology, experimental pathology, and forensic pathology, each focusing on different aspects of disease investigation and diagnosis. The core components of pathology include etiology, pathogenesis, morphology, and clinical significance, emphasizing that diseases often arise from multifactorial causes.

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Introduction
By: Eyerusalem Fekade(MD)

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 Literally:
 Pathos-disease, abnormality, suffering,
maladies.
 Logy –study
The scientific study of disease.
Disease is an abnormal variation in structure
and function of part of the body.
What is pathology?

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 Pathology is abridging discipline involving both
basic science and clinical practice and is devoted
to the study of the structural and functional
changes in cells, tissues, and organs that underlie
disease.

Scope of Pathology
Pathology is the foundation of medical science
and practice. it attempts to explain the whys and
wherefores of the signs and symptoms
manifested by patients while providing a sound
foundation for rational clinical care and therapy.
Without pathology, the practice of medicine
would be reduced to myths and folklore.
Introduction to pathology…
Scope of Pathology

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Clinical and experimental pathology
Scientific knowledge about human diseases
is derived from observations on patients or, by
analogy, from experimental studies on animals
and cell cultures. The greatest contribution
comes from the study of tissue and body fluids
detailed from patients. Pathology has a key
role in translational research by facilitating the
transfer of knowledge derived from laboratory
investigations into clinical practice.
Scope of Pathology……

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Clinical pathology:-
is more concerned with a cross-sectional
analysis at the level of the disease itself, studies in
depth-the cause and mechanisms of the disease,
and the effects of the disease upon the various
organs and systems of the body.
N.B clinical medicine cannot be practiced without an
understanding of pathology; pathology is
meaningless if it doesn’t have clinical implications.
 Experimental pathology:-
Experimental pathology is the observation of
the effects of manipulations on experimental
systems such as animal models of disease or cell
cultures.
Scope of Pathology…..

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Pathology is a vast subject with many
ramifications. In practice, however, it has
major subdivisions:
 Histopathology: the investigation and
diagnosis of disease from the examination of
tissues
( tissue samples called Biopsy).
- technique of biopsy taking is surgical excision
 Cytopathology: the investigation &
diagnosis of disease from the examination of
isolated cells - technique of cell sample taking
is Fine needle aspiration(FNA), Paps.
Subdivisions of clinical pathology

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 Hematology: the study of disorders of the
cellular and coagulable components of blood
 microbiology: the study of infectious
diseases and the organisms responsible for
them.
 immunology: the study of the specific
defense mechanisms of the body.
 chemical pathology: the study and diagnosis
of disease from the chemical changes in
tissues and fluids.
 toxicology: the study of the effects of known
or suspected poisons.
Subdivisions of…….

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 forensic pathology: the application of
pathology to legal purposes (e.g. investigation
of death in suspicious circumstances).
- it uses autopsies (necropsy ,or postmortem
examination )both means to 'see for oneself‘.
-Autopsies are useful for:
 determining the cause of death
 audit of the accuracy of clinical diagnosis
 education of undergraduates and postgraduates
 research into the causes and mechanisms of
disease
 gathering accurate statistics about disease
incidence.
Subdivisions of…….

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 Pathologists use a variety of molecular, microbiologic, &
immunologic techniques to understand the biochemical,
structural, & functional changes that occur in cells,
tissues, and organs.
Investigation modalities to aid study of
pathology
1. Light microscopy :-
- used to examine cells ,or tissues from cysts, body cavities,
sucked from solid lesions or scraped from body
surfaces.
- used for cytopathologic & Histopathologic studies which
are used widely in cancer diagnosis and screening.
TECHNIQUES OF PATHOLOGY

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2. Electron microscopy
- used to study disorders at an organelle level,
and to the demonstration of viruses in
tissue samples from some diseases.
3. Histochemistry
is the study of the chemistry of tissues,
usually by microscopy of tissue sections
after they have been treated with specific
reagents so that the features of individual
cells can be visualized.
Techniques……

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4.Immunohistochemistry&immunofluorescen
ce
-These techniques employ antibodies
(immunoglobulin's with antigen specificity) to
visualize substances in tissue sections or cell
preparations.
A. Immunohistochemistry:- uses antibodies
linked chemically to enzymes.
- in this technique, the end product is a deposit of
opaque or colored material that can be seen
with a conventional light microscope
Techniques……

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 Pathology is best learnt in two stages
I. General pathology: Common changes in all
tissues.
the mechanisms and characteristics of the principal
types of disease process or, fundamental cellular and
tissue responses to pathologic stimuli. These are:-
- Inflammation,
- Neoplasia
- Aging
- Degenerations and so..on
N.B: General pathology is the foundation of knowledge
that has to be acquired before studying the systematic
pathology of specific diseases.
LEARNING PATHOLOGY

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II. Systemic Pathology:- Specific changes in organs.
The descriptions of specific diseases as they
affect individual organs or organ systems
(e.g. appendicitis, lung cancer, Heart
failure).
Learning Pathology……

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 Pathology-the study of disease:
 The characteristics of any disease are
- Etiology (or cause)
- epidemiology (or incidence).
- Pathogenesis (or mechanism)
- morphological, functional and clinical
changes (or manifestations)
- complications and sequelae (or
secondary effects)
- prognosis (or outcome)
Introduction to general pathology…

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 The four aspects of a disease process that
form the core of pathology are:
1. Etiology - Causes
2. Pathogenesis - Evolution
3. Morphology - Structural Changes
4. Clinical Significance & Functional Changes
Introduction to general pathology…

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Etiology
 Primary- etiology: if the cause of the
disease is known.
 Idiopathic –if the cause is unknown.
 Generally etiology of the disease can be:
1.Genetic /intrinsic
2.Acquired /environmental
Introduction to general…

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 Environmental agents:
◦ Physical
◦ Chemical
◦ Nutritional
◦ Infections
◦ Immunological
◦ Psychological
◦ ….
 Genetic Factors:
◦ Age
◦ Genes
◦ Immunological
◦ Psychological
◦ ……
Etiology:
Multifactorial

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 Diseases are “caused” due to internal or
external factors.
 Multifactorial:
No more
“one cause to one disease”
 Genetic factors affect acquired diseases
and environment has profound effect on
genetic diseases.
Multifactorial Etiology:

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 Pathogenesis refers to the sequence of
events in the response of cells or tissues to
the etiologic agent, from the initial
stimulus to the ultimate expression of the
disease.
 The study of pathogenesis remains one of
the main domains of pathology.
Pathogenesis:

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 Structural and associated functional
changes in cells, tissues and organs that
are characteristic of the disease or
condition.
Morphology:

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Functional Derangements & Clinical
Manifestations:
 The nature of the morphologic changes and their
distribution in different organs or tissues influence
normal function and determine the clinical features
(symptoms and signs), course, and prognosis of the
disease.
Introduction to general…

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Pathology is the scientific study of disease
Pathology is abridging discipline involving both basic science
and clinical practice
The four aspects of a disease process that form the core of
pathology are : Etiology, Pathogenesis, Morphology, Clinical
Significance & Functional Changes
The cause of any disease is Multifactorial : No more “one
cause to one disease”
Summary

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Thank you!!!