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Introduction to Pathology And
its rule in the diagnostic
process
Dr: Wael H.Mansy, MD
Assistant Professor
College of Pharmacy
King Saud University
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.
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 the disease


according to body organ
according to etiology
Etiological classification of the disease
Name
Etiology
Inherited or familial disease Caused by defects inherent in the chromosome or gene
of one or both parents that is transmitted to the
offspring e.g. Down’s syndrome.
Congenital disease
Present at birth; some are inherited while others may be
caused by a developmental defect of known or unknown origin.
e.g. Cleft lip.
Toxic disease
Infectious disease
Caused by ingestion of a poison e.g. inhalation of carbon monoxide
Resulting from an invasion of living pathogenic organism e.g Influenza
Traumatic disease
Caused by physical injury e.g. accidents.
Degenerative disease
The primary abnormality is degeneration of various parts
of the body. E.g. osteoarthritis.
Etiological classification of the disease
Name
Etiology
Immunologic disease
Neoplastic disease
Hypersensitivity, autoimmunity, immunodeficiency are three
types of immune reactions with harmful effects to the host. E.g.
AIDS
Abnormal cell growth that leads to various types of benign and
malignant tumors. E.g. fetal alcohol syndrome. e.g. breast cancer.
Nutritional disease
Deficiency of protein, calories, or vitamins e.g. malnutrition.
Metabolic disease
Resulting from a disturbance in some important metabolic
process of the body. e.g. DM.
Etiological classification of the disease
Name
Etiology
Psychogenic disease
Originating in mind, having emotional or psychogenic
origin in relation to symptom. E.g. depression.
Iatrogenic disease
A disease or disorder produced inadvertently as a
result of treatment by a health care professional for
some other disorder. E.g. fetal alcohol syndrome.
Idiopathic disease
Disease of unknown cause. E.g. HTN.
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.
Branches of Pathology
General Pathology
 Systemic Pathology
 Gross Pathology
 Cellular Pathology
 Surgical Pathology
 Clinical Pathology
 Immunopathology

Learning Pathology:

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.
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
Pathology focuses on 4 aspects of disease:

ETIOLOGY: Cause of disease.

PATHOGENESIS:
Mechanisms of development of disease.

MORPHOLOGY:
The structural alterations induced in cell and tissues.

FUNCTIONAL CONSEQUENCES:
Functional results of the morphologic changes, as
observed clinically.
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…. etc.).
Etiology
Disease Disease
Disease
Disease
One
etiologic agent
one disease, as
Malaria.
• Several etiologic
agents
one
disease, as diabetes .
Disease
• One etiologic
agent
several diseases,
as smoking.
Etiology:
What is the cause?

Environmental agents:
Physical
• Chemical
• Nutritional
• Infections
• Immunological
• Psychological
•

Genetic Factors:
•
•
Age
Genes
Multifactorial:
As Diabetes,
Hypertension
Cancer
pathogenesis
The sequence events in the response of the cells or
tissues to the etiologic agent, from the initial
stimulus
to
the
ultimate
expression
of
the
disease,”from the time it is initiated to its final
conclusion in recovery or death”
The core of the science of pathology —
the study the
pathogenesis of the disease.
Morphology: Structural Changes
*Structural changes in disease.
 Tumor
in a cancer.
 Ulcer in an infection.
 Atrophy in dementia.
*Lesion:
Demonstratable
structural
change produced in the course of the
disease (gross level, microscopic level)
Manifestations
*Subclinical Stage: Early in the development of
the disease, the etiological agent may provoke a
number of changes in biologic process that lab
analysis can detect, even though the patient has
no subjective symptoms.
*Symptoms:Clinical symptoms are the patient’s
complain usually by its own words.
*Signs: when the observer can objectively identify
manifestations of the disease. They are seen only in
the living individual e.g. fever, tenderness,
increased respiratory rate, etc.)”
*Sequelae: the outcome of the disease.
*Complication: of the disease is a new or separate
process that may arise secondarily because of
some change that the original entity produce.
*Resolution:when the host return to a completely
normal state, without sequelae or complications
(spontaneously from body defenses or from
successful therapy).
*Prognosis: Expected outcome of the disease, It is
the clinician's estimate of the severity and
possible result of a disease.
I hear, I forget
I see, I remember
I do, I understand
Chinese Proverb ..