Introduction to Pathology
DR:Gehan mohamed
Definition of pathology
It is the “Scientific
study of disease"
.
"scientific study of the molecular, cellular,
tissue,
or
organ
system
response
to
injurious agents."
Pathology serves as a "bridge" or "link" between the
preclinical sciences (anatomy, physiology, ……etc.) and
the courses in clinical medicine.
2. Classification:
Autopsy
(1) Human pathology Biopsy
Cytology
(2) Experimental pathology
Seven Branches of Pathology
General Pathology
 Systemic Pathology
 Surgical Pathology
 Gross Pathology
 Cellular Pathology
 Clinical Pathology
 Immunopathology


General Pathology

Common changes in all tissues. e.g.. Inflammation,
cancer, ageing, edema, hemorrhage ….etc.

Systemic Pathology

Discussing the pathologic mechanisms in relation to
various organ systems e.g. CVS, CNS, GIT…..etc.
Techniques of Pathology
1. Human pathology
(1) Autopsy
(2) Biopsy
(3) Cytology: smear, fine needle
aspiration
2. Experimental pathology
(1) Animal experiment: animal model
(2) Tissue and cell culture
Necropsy: Gross examination of the
animal cadaver by systematic dissection in
order to evaluate any abnormal changes
(lesions) that may be present.
 Autopsy: Synonymous to necropsy in
human medicine
 Biopsy: Removal and examination of
tissue obtained from the living body

What is the Disease?

It is the “State in which an individual
exhibits an anatomical, physiological, or
biochemical deviation from the normal”
•Disease may be defined as :
an abnormal alteration of structure or function in any part of the
body.
Classification of Diseases:

(A)Developmental – genetic, congenital.

(B)Acquired:
(1)Inflammatory – Trauma, infections, immune,
etc.
(2)Neoplastic – tumors cancers
(3)Degenerative – ageing.
(4)Metabolic.
(5)Iatrogenic: Drug induced.
What should we Know About A
Disease
• Definition.
• Epidemiology – Where & When.
• Etiology – What is the cause?
• Pathogenesis - Evolution of dis.
• Morphology - Structural Changes
• Functional consequences
• Management
• Prognosis
• Prevention
Etiology
“Study of the cause of a disease"
Knowledge of etiology remains the backbone of:

Disease diagnosis

Understanding the nature of diseases

Treatment of diseases.
Etiology
“Study of the cause of a disease"

An etiologic agent :
is the factor (bacterium, virus, etc.) responsible for lesions or a disease
state.

Predisposing Causes of Disease:
Factors which make an individual more susceptible to a disease (damp
weather, poor ventilation, etc.)

Exciting Causes of Disease:
Factors which are directly responsible for a disease (hypoxia, chemical
agents , virus, bacteria …. etc.).
Etiology
Disease Disease
Disease
Disease
One
etiologic agent
one disease, as
Malaria.
• Several etiologic
agents
one
disease, as cancer .
Disease
• One etiologic
agent
several diseases,
as smoking.
Pathogenesis
The sequence of events in the
response of the cells or tissues to
the etiologic agent, from the
initial stimulus to the ultimate
expression of the disease.
CELLS Response to injurious
agent
Either :
 ADAPTING
 SUSTAINING REVERSIBLE INJURY
 SUFFERING IRREVERSIBLE
INJURY AND DYING
Clinical Symptoms & Signs
Clinical
symptoms
are
the
patient’s
complain usually by its own words as pain.

Clinical signs are seen only in the living individual
as organomegaly.
MORPHOLOGY
Morphology remains at the
heart of diagnostic pathology.

Morphologic change
Characteristic of the disease
Diagnostic of the etiologic process

Functional derangements
Morphology
(1)Gross appearance:
size, shape
weight
color
consistency
surface
edge, section
(2)Microscopic examination for tissue
sections fixed in formalin then stained by
HE (hematoxylin and eosin) to be
examined by light microscope for
Histologic and cytologic changes.
Hemangioma
Histochemistry using PAS stain
PAS→BM
Immunohistochemistry
1. Ag-Ab specific reaction
2. Applications : in diagnosis of
tumor histogenesis
Leiomyosarcoma
Actin (+)
(3)Ultrastructural observation
By using electron microscope)
Filtering membrane
SEM (scanning electron
microscope)
Podocyte
(4)Flow cytometry (FCM)
In neoplastic diseases Can determine :
1- If there is One kind of
cells→quantitative assesment
2. DNA ploidy analysis (amount of DNA)
（5）Image analysis (IA)
it can determine Nuclear diameter;
circumference; area; volume;
morphology
（6）Molecular biology technique
1. Polymerase chain reaction (PCR)
2. DNA sequencing
Polymerase
chain
reaction
(PCR)
prognosis

Expected outcome of the disease, It is the
clinician's estimate of the severity and possible
result of a disease.