Causes of cellular injury reduced oxygen supply. 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.