Give the introduction to pathology

1. Pathology
INTRODUCTION TO
PATHOLOGY
Stanley chinyanta
PBS- Chainama college
Lecture 1

2. Introduction
Pathology
• is literally the study (logos) of suffering (pathos).
• is a bridging discipline involving both basic
science and clinical practice
• Is the study of the structural and functional
changes in cells, tissues, and organs that
underlie disease.
• Traditionally, the study of pathology is divided
into general and systemic, pathology.
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3. • Pathology is the foundation of medical
science and practice.
• Without pathology the practice of medicine
would be reduced to myths and folklore.
• The four aspects of a disease process that
form the core of pathology are
- Aetiology,
- Pathogenesis,
- Morphologic changes, and
- Clinical significance.
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4. Aetiology
• Aetiology of a disease means
the cause of the disease.
• There are two major classes
of etiologic factors:
- intrinsic or genetic, and
- extrinsic or acquired.
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5. Pathogenesis
• mechanism through which the cause
operates to produce the pathological and
clinical manifestations or
• the sequence of events in the response of
cells or tissues to the aetiologic agent,
from the initial stimulus to the ultimate
expression of the disease.
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6. Morphologic changes
• are the structural alterations in cells or tissues
that are either characteristic of the disease or
diagnostic of the aetiologic process.
• The structural changes maybe gross or
microscopic changes.
• In addition, the morphologic changes will lead to
functional alteration & to the clinical signs &
symptoms of the disease.
• the structural or functional abnormality
responsible for ill health is known as a lesion
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7. Pathognomonic Abnormalities
• Pathognomonic features are restricted to
a single disease, or disease category, and
without them the diagnosis is impossible
or uncertain. eg
• Reed-Sternberg cells are said to be
pathognomonic of Hodgkin`s lymphoma.
• The presence of Mycobacterium
tuberculosis, in the appropriate context, is
pathognomonic of tuberculosis.
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8. Complications and Sequelae
• Diseases may have prolonged, secondary or
distant effects.
• Examples include the spread of an infective
organism from the original site of infection, where
it had provoked an inflammatory reaction, to
another part of the body, where a similar reaction
to it will occur.
• The course of the disease may be prolonged and
complicated if the body`s immunity is impaired.
• An aftereffect (secondary effect) of a disease is
called a Sequelae.
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9. Prognosis, Remission & Relapse
• The prognosis forecasts the known or
likely course of the disease and, therefore
the fate of the patient.
• Remission is the process of conversion
from active disease to quiescence.
• Later the signs and symptoms may
reappear; this is the process of relapse.
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10. DIAGNOSTIC TECHNIQUES AND
SUBDIVISIONS OF CLINICAL PATHOLOGY
Histopathology
• the investigation and diagnosis of disease
from the examination of body tissues
under the microscope.
• the pathologist looks for abnormal
structures in the tissue.
• Histopathology is usually the gold
standard for pathologic diagnosis.
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11. Cytopathology
• the investigation and diagnosis of disease from
the examination of isolated cells
• Compared to histopathological technique it is
cheap, takes less time and needs no
anesthesia to take specimens.
• There are different Cytopathologic methods
including:
- Fine-needle aspiration cytology (FNAC)
- Exfoliative cytology
- Abrasive cytology
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12. Haematology
• the study of disorders of the cellular and
coagulable components of blood.
• Hematological examination is a method by
which abnormalities of the cells of the
blood and their precursors in the bone
marrow are investigated to diagnose the
different kinds of anemia & leukemia.
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13. Chemical pathology
• the study and diagnosis of disease from the
chemical changes in tissues and fluids
• Biochemical examination is a method by
which the metabolic disturbances of disease
are investigated by assay of various normal
and abnormal compounds in the blood, urine,
etc.
• Toxicology is the study of known or
suspected poisons
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14. Microbiology
• the study of infectious diseases and the
organisms responsible for them
• Microbiological examination is a method
by which body fluids, excised tissue, etc.
are examined by microscopical, cultural
and serological techniques to identify
micro-organisms responsible for many
diseases.
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15. Immunology
• is the branch of pathology which study the
specific defense mechanisms of the
body.
• Immunohistochemistry is a method used
to detect a specific antigen in the tissue in
order to identify the type of disease.
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16. Genetics
• the study of abnormal chromosomes and
genes
• Clinical genetics (Cytogenetics) is a method
in which inherited chromosomal abnormalities
are investigated using the techniques of
molecular biology.
• Different molecular techniques such as
fluorescent in situ hybridization, Southern
blot, etc... can be used to detect genetic
diseases.
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17. Forensic pathology
• is the application of pathology to legal
purposes.
• i.e the investigation of death in
suspicious circumstances.
Autopsy
• Autopsy is examination of the dead body
to identify the cause of death. This can
be for forensic or clinical purposes.
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18. NOMENCLATURE OF DISEASE
• Uniform nomenclature facilitates communication and
enables accurate epidermiological studies.
• Many standard conventions are used to derive
names of diseases. eg
- Primary and secondary
- Acute and chronic
- Benign and malignant
- Prefixes and suffixes
- Eponymous
- Syndromes
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19. Primary And Secondary
• These words may be used to describe the
causation of disease.
• Primary/essential/idiopathic/cryptogenic in
this context means that the disease is
without evident antecedent cause.
• Thus, primary hypertension is defined as
abnormally high blood pressure without
apparent cause.
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20. • Secondary means that the disease represents a
complication or manifestation of some underlying
lesion.
• Thus, secondary hypertension is defined as
abnormally high blood pressure as a consequence
of some other lesion.
• The words primary and secondary may be used to
distinguish between the initial and subsequent
stages of a disease, most commonly in cancer.
• The primary tumor is the initial tumor from which
cancer cells disseminate to cause secondary
tumors elsewhere in the body.
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21. Acute And Chronic
• These are used to describe the dynamics of a
disease.
• Acute conditions have a rapid onset, often but not
always followed by a rapid resolution.
• Chronic conditions may follow an acute initial
episode, but often are of insidious onset, and have
a prolonged course lasting months or years.
• The terms are mostly used to qualify the nature of
an inflammatory processes.
• The words may be used by patients to describe
some symptoms, eg. An acute pain being sharp
or severe.
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22. Benign And Malignant
• these are emotive terms used to classify certain
diseases according to their likely outcome.
• Thus benign tumors remain localized to the tissue
of origin and are very rarely lethal, whereas
malignant tumors invade and spread from their
origin and are commonly lethal.
• Benign hypertension is relatively mild elevation of
blood pressure that develops gradually and
causes insidious injury to the organs of the body.
• Malignant hypertension is when the blood
pressure rises rapidly and causes severe
symptoms and tissue injury.
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23. Prefixes
• Commonly used prefixes and their meanings are:
• Ana – absence eg anaphylaxis
• Dys – disordered eg dysplasia
• Hyper – an excess over normal eg hyperthyroidism
• Hypo – a deficiency below normal eg
hypothyroidism
• Meta – a change from one state to another eg
metaplasia
• Neo – new growth eg Neoplasia
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24. Suffixes
• Commonly used suffixes and their meanings
are:
• -itis - meaning an inflammatory process eg
appendicitis
• -oma – meaning a tumors eg carcinoma
• -osis – meaning state or condition, not
necessarily pathological eg osteoarthrosis
• -oid – meaning bearing a resemblance to eg
rheumatoid arthritis
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25. • -penia – meaning lack of eg
thrombocytopenia
• -cytosis – meaning increased number of
cells, usually in blood eg leukocytosis
• -ectasis – meaning dilation eg bronchiectasis
• -plasia – meaning a disorder of growth eg
hyperplasia
• -opathy – meaning an abnormal state lacking
specific characteristics eg lymphadenopathy
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26. Eponymous Names
• An eponymous disease or lesion is named after a
person or place associated with it.
• Eponymous names are used commonly either
when the nature or cause of the disease or lesion
is unknown, or
• long term usage has resulted in the name
becoming part of the language of medicine or
• to commemorate the person who first described
the condition.
• Eg Graves` disease, Paget disease of the nipple,
Crohn`s disease, Hodgkin`s disease, Reed-
Sternbeg Cells etc
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27. Syndromes
• A syndrome is an aggregate of signs and
symptoms or a combination of lesions without
which the disease cannot be recognized or
diagnosed.
• Syndromes often have eponymous titles.
Examples include:
• Cushing`s syndrome: hyperactivity of the adrenal
cortex resulting in obesity, Hirsutism,
hypertension.
• Renfield`s syndrome: a mental disorder where a
patient is obsessed with drinking human blood.
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28. Course, outcome and clinical
consequences Of Disease
• The course of a disease in the absence of
any intervention is called the natural history
of the disease.
• Following clinical onset, disease may follow
any of the following trends:
• a) Resolution can occur leaving no sequelae,
• b) The disease can settle down, but sequelae
are left, or
• c) It may result in death.
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29. References and Credits
• Robbins SL and Kumar V (2007). Basic
Pathology (8th Edition).WB Saunders Co.
London.
• Underwood, J.C.E and Cross, S. S (2009).
General and Systematic Pathology (5th
Edition). Churchill-Livingstone, Edinburgh. ISBN:
978 0443068881
• Bezabeh M, et al (2004) A. general Pathology:
Lecture notes of health science students.
Published by Jimma Haramaya, Dedub and
Gondar Universities, Ethiopia.
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