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Week 1
Introduction to Pathology
Dr.İ.Taci Cangül
Bursa-2008
What is Pathology?
• “Scientific study of disease" or the
alterations that occur when abnormal
influences (bacteria, viruses, etc.) affect
cells, tissues, or body systems. More
specifically, pathology may be defined as
the "scientific study of the molecular,
cellular, tissue, or organ system
response to injurious agents or
adverse influences."
Pathology Deals with…
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The causes of disease (etiology)
Mechanisms of disease (pathogenesis)
Structural alterations of cells and tissues
Functional alteration and consequences of
disease
Function of Pathology
Pathology serves as a "bridge" or "link"
between the preclinical subjects
(anatomy, physiology, etc.) and the
courses in clinical medicine. Actually,
pathology provides a logical means of
relating the knowledge of normal structure
and function (anatomy and physiology)
to abnormal structure and function as
encountered in a diseased animal.
Basic Language of Pathology
In order for a subject or course to be
meaningful, one should become familiar
with the basic terminology applicable to
that subject.
Health
• “State in which an individual is living in
complete harmony with his
environment"
• A relative state
• All body functions are performed normally
even though lesions may be present in
organs and/or tissues. It should be
remembered that the transitional zone
between health and disease is difficult to
define
Disease
• “State in which an individual exhibits
an anatomical, physiological, or
biochemical deviation from the normal.“
The term "disease" is employed to
describe a state in which there is sufficient
departure from the normal for clinical signs
or symptoms to be produced.
Lesion
• “Structural or morphological alterations
associated with a diseased state in an
individual”
• Gross lesion: Naked-eye
• Microscopic lesion: Light microscope
• Ultrastructural lesion: Electron microscope
• Pathognomonic Lesion: A change which is
specifically characteristic of a disease. When
one sees a pathognomonic lesion, he knows
that a particular disease is present.
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 (bacteria,
viruses, hypoxia, chemical agents, etc.).
Clinical Signs
• “Functional evidence of disease which
can be determined objectively or by the
observer" (lameness, salivation,
increased respiratory efforts, etc.)”
• Clinical signs are seen only in the living
individual.
Diagnosis
• “Determination of the nature of a disease"
• A morphologic or anatomic diagnosis is based
on the location and nature of the lesion
(hemorrhagic enteritis, etc.). Etiologic
diagnosis is made on the basis of the cause
(dirofilariasis, etc.). Definitive diagnosis is
made on the basis of the specific disease entity
involved (canine distemper, etc.). A clinical
diagnosis is made on the basis of clinical signs
observed in the living animal.
Prognosis
• Probable outcome of a disease in a living
individual. It is the clinician's estimate of
the severity and possible result of a
disease.
Pathogenesis
• “Progressive development (sequence
of events) of a disease from the time it
is initiated to its final conclusion in
recovery or death”
• Necropsy: Gross examination of the
carcass 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
• Euthanasia: Intentional putting to death
of an individual with an incurable or painful
disease by employing humane means
• Somatic death: Death of the entire body
• Necrobiosis: Death of cells at the end of
their normal life-span within the living body
(epithelial cells of the skin, leukocytes,
etc.)
• Necrosis: Morphological changes caused
by the progressive degradative action of
enzymes on the lethally injured cell within
the living body
Postmortem Changes
• Cell death which accompanies or occurs after
death of the entire body (somatic death)
• Postmortem autolysis: Self-digestion by
enzymes
• Postmortem putrefaction: Decomposition of
tissues by bacterial enzymes after death of the
entire body
• Rigor mortis: Stiffening of all muscles after
death
Branches of Pathology
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General Pathology
Systemic Pathology
Gross Pathology
Cellular Pathology
Surgical Pathology
Clinical Pathology
Immunopathology