Aetiology, Pathogenesis And Pathophysiologucal Basis Of Diseases Flashcards
Disease aetiology is broadly classified into
inherited or acquired
•Acquired causes can be classified into:
• physical
• dietary
• Chemical
•microbiologic agents
•Majority of diseases have complex aetiology
(multifactorial)
Define Pathophysiology
refers to the functional changes associated with or resulting from disease or injury and the scientific study of such changes.
Diseases are better understood from the perspective of ‘disordered physiology’ (Pathophysiology)
It can also be referred to as physiopathology. i.e concerned with either the bodily functional changes that cause a disease or the bodily functional changes that result from disease
Pathophysiology emphasizes the dynamic aspects of disease
•It is concerned with the disruption of normal physiology: i.e
the alterations, derangements
mechanisms involved in disruption and
how they manifest as symptoms and signs as well as laboratory findings
While pathology studies the structural, biochemical and functional changes in cells, tissue and organs in disease states,
PP does all with the exclusion of
structural changes
Pathogenesis is
is defined as the mechanisms that underlie disease from the effect of the aetiological agents to the reactions of the body against them, resulting in manifestation of the disease
It is a major pillar of pathology involving the biochemical and morphological changes that occur before a disease is manifested.
The process takes multiple steps from the injurious agents to the manifestation of symptoms and signs of the disease
What is the concept of normalcy
Concept of normalcy or disease is arbitrary to an extent and are influenced by cultural values and biological realities
What is normal value
for any measurable parameter in an individual or group of individuals is defined as an average value for that parameter
This is because average value for such parameters (e.g-weight, height, Blood Pressure) are derived from observations on many individuals
Reasons for variations:
• Differences in genetic constitution
• Differences lifestyles and environmental exposures
• Intrinsic variation in physiological processes in an individual
•Thus, a single measurement, observation or laboratory result which appears abnormal should be interpreted with caution
__________ is an essential feature of normalcy
• Maintenance of internal constancy (stability)
• Requirements for cells to maintain normalcy include:
Oxygen and nutrients to function and survive; An environment with narrow ranges of
temperature, PH, water and salt concentration
Homeostasis is maintenance of a steady state of internal chemical and physicale.g maintenance of body temp, BP, PH etc
Disease can thus be considered as
life beyond the limits of normal
It is not a new form of life but an extension or distortion of the normal life processes
4 basic disease processes
Aetiology-cause (inherited, acquired or multifactorial)
Pathogenesis-mechanism of its development
Morphological changes-structural alterations in cells or tissue characteristic or diagnostic of an aetiological process
Functional consequences and clinical manifestations(subclinical & clinical stages)-
Disease manifestations is in 3 stages
Subclinical (latent incubation)
Clinical manifestation
Recovery or complications
Explanation of disease manifestations
Most diseases at the early stage have subclinical stage during which the patient functions normally (no symptom/sign) even though the disease is already well established.
Abnormality can only be detected by laboratory tests-incubation period e.g. in hepatitis
Many organs in the body have large reserve(safety margin) in terms of both structure and function that functional impairment only becomes evident after the disease has advanced anatomically.
E.g. Chronic renal disease, chronic liver disease such as liver cirrhosis
Difference between signs and symptoms
• When there is encroachment on normal biological processes, the earliest manifestations are most often subjective(symptoms) which may be non- specific
• E.g. dyspepsia in gastric cancer,
• Identifiable aberrations(objective) in the patient-
signs
What is a lesion
• A Lesion refers to demonstrable structural change produced in the course of a disease which may be macroscopic or microscopic
Are diseases static
False
Diseases are dynamic, not static
Manifestation differs from day to day in the patient and thus every disease has a range of manifestations or natural history (natural course). This is determined by:
compensatory(adaptive) mechanisms come in Environmental influences on the patient
Most causes of diseases are acquired from the environment through
• infections,
• mechanical trauma,
• toxic chemical,
• radiation,
• nutritional aberrations
Genetic constitution is almost always important in most diseases because it determines
Anatomic characteristics
Physiological mechanisms
Modes of response to injury
E.g in infectious disease which is exogenous, genetic factors can influence the susceptibility to the infectious agent as well as the pattern of disease produced e.g H.pylori infection
The Spectrum between heredity and environment in the causation of disease are 3:
Diseases largely determined by
environmental factors-infections
Those determined largely by genetic errors(hereditary) and are expressed regardless of extrinsic influences-sickle cell disease
In between are those in which there is interplay between genetic and extrinsic factors -cancer
Pathophysiology of H pylori
• H.pylori is a spiral, microaerophilic, gram negative bacterium.
• Transmitted via oral- oral and faeco-oral route
• It can cause multiple diseases in the Upper GIT
