INTRODUCTION. DEFINITIONS AND BASIC ASPECTS OF DISEASE.
INTRODUCTION
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
-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.
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
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 wether 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
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
The study of pathology is divided into:
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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 (tumors)
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)..

as a science- focuses on the mechanisms by which cells and tissues are
injured, on the structural and functional consequences of injurious stimuli on
the cells, tissues, and organs, finally on the entire organism

as a morphologic discipline- describes pathological morphologic findings in
tissues and cells
-in broader terms, pathology means also study of the diseases, their of
causes, prevention and classification
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 nervosamental anorhexia
All diseases have certain aspects which can form the basis for classificationthese 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
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-clinical significance and consequencies
1.epidemiology-provides a wider context for the study, classification, and
diagnosis of diseases
-epidemiological data are important
-for providing informations about causes of d.
-for identifying risk factors
prevention,
-for
providing
adequate
health
care,
and
planning
disease
epidemiology records data about
incidence-number of new cases occurring in a defined population over a
defined time period
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
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 - 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.)
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
4.morphological changes
-structural alterations induced in cells and tissues
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-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
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 informations with respect to
clinical outcome, prognosis, etc.
-symptoms- features of illness that are noticed by patients
-signs- clinical manifestation of the disease which are recognized by
clinicians
Etiological classification of diseases
Type
Basis
Examples
Congenital
Genetic
Hemophilia A
(absence of
factor VIII)
Acquired
clotting
Non-genetic
Intrauterine
rubeolla
infection
(measles)
leads
to
deafness/blindness in
the fetus
Inflammatory
Dermatitis
inflammation
skin)
Vascular
Atherosclerosis
(eczema,
of the
Growth
and Tumors
proliferation disorders
Metobolic
Gout (deposition of uric
acid crystals in joints
and soft tissues
Degenerative
Alzheimer
demencia
disease-
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Drug induced
Renal failure
Infective
tbc
 pathology studies aspects of somatic death
-definitions of terms:
-cardiorespiratory – morphologic criteria are quite difficult to
establish, since the cells and tissues differ one from another in susceptibility
to anoxia following cessation of cardiorespiratory function
-neurologic- refers to cessation of brain electric activity
-ethical consideration- relate to ability to prolong life by artificial means and
availability of organs for transplantation
-organ variability- resistance to cessation of cardiorespiratory functions
show wide differences, brain and heart can survive 5 minute without
respiration and circulation, kidney can survive 30 minutes, liver is viable up to
2 hours, etc.
-changes associated with somatic death-general cellular- same as those related to cell death
-algor- loss of body heat, speed is dependent on environmental conditions
-livor- pooling of blood in dependent parts, causing reddening of skin
-rigor mortis- muscle rigidity due to loss of adenosine triphosphate (ATP),
rate is dependent on amount of residual stored glycogen
-putrefaction- invasion of dead and dying tissue by bacteria
Methods of measuring time after death- crude but variable estimate can be
made from algor, livor and rigor
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 involves skills and laboratory tests
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
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
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-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.

new special techniques- in recent years, traditional histopatholgic techniques
can be supplemented by more sophisticated methods that facilitate the
specific demonstration and location of individual cells and subcellular
components, such as
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