Download Tissue and Cellular Injury

Causes of cellular injury
1. Hypoxia: reduced oxygen supply.
i. e. respiratory disease, cardiovascular
diseases, loss of blood supply, loss of
the oxygen-carrying capacity of the
blood as in anemia or carbon monoxide
poisoning.
2. Physical agents:
Mechanical trauma, extremes of heat or cold,
sudden changes in atmospheric pressure,
radiant energy and electrical energy all have
wide-ranging effects on cells.
3. Chemical agents:
Virtually any chemical agent or drug maybe
implicated. Even an innocuous substance
such as glucose, if sufficiently concentrated,
may so derange the osmotic environment of
the cell that it causes injury.
4. Microbiologic agents:
A host of living agents, ranging in size
from the submicroscopic viruses to
grossly visible nematodes, may attack
human causing cell injury.
5. Abnormal immunological reactions:
The immune process is normally protective but
in certain circumstances the reaction may
become deranged. Hypersensitivity to various
substances can lead to anaphylaxis or to more
localized lesions such as asthma. In other
circumstances the immune process may act
against the body cells——autoimmunity.
6. Genetic derangements:
Mutations may deprive the cell of a single
enzyme or maybe so severe that they are
incompatible with cell survival. The mutations
may appear during gametogenesis, in the
early zygote or in adult cells (a somatic
mutation). Somatic mutations may underlie
the origins of cancerous transformation of
cells. And some genetic abnormalities are
transmitted as familial traits, such as sickle
cell anemia.
7. Nutritional imbalances:
Protein-calorie deficiencies are the most
examples of nutrition deficiencies. Vitamins
also are rampant in deprived populations and
are not uncommon even in industrialized
nations having relatively high standards of
living. Ironically, excess in nutrition are
important causes of morbidity and mortality.
Excess calories and dies rich in animal fat are
now strongly implicated in the development
of atherosclerosis. Obesity alone leads to an
increased vulnerability to certain disorders,
such as atherosclerosis, coronary heart
disease, diabetes mellitus
8. Aging
Programmed aging whereby after a defined
number of divisions the cell undergoes
terminal differentiation.
Development of an increasing population of
cells irreversibly committed to senescence
and death.
Increased susceptibility to somatic mutation
and a build-up of errors leading to an
eventual’ error catastrophe.
Faulty DNA repair mechanisms.