Pathophysiology of Cell Injury
INTOXICATION or POISONING
Cell injury also occurs as a result of poisoning. Toxins are injurious substances that produce cell intoxication. Toxins could either be exogenous or endogenous.
- Exogenous Toxins
Exogenous toxins are of external origins can be characterized as being of biological or non-biological origin.
- Biological exogenous toxins – these are produced by living organisms which are commonly microorganisms. These microorganisms serve as agents of infection and they gain access to body tissues and release injurious substances inside the body. Most commonly bacteria are sources of biological toxins, however, other microorganisms such as the fungi and protozoa can also produce toxins that may cause an injury to the cells.
- Non-biological exogenous toxins – these are injurious chemicals that originate outside the body. When these substances (chemicals) are inhaled or swallowed they cause a massive cell injury and damage. Many therapeutic drugs are highly effective at prescribed doses. However, the same drugs can be fatal in higher doses.
- Endogenous Toxins
Endogenous toxins are injurious substances that arise inside the cells. These toxins are formed in two ways:
- Genetic defect which causes a toxic substance to be constantly produced. Intoxification in this way could either be direct or indirect. An example of direct intoxification due to a genetic defect is in case of Huntington’s disease, wherein a toxic substance causes a neurological dysfunction.
In indirect genetic intoxification the product of a genetic defect, which by itself not toxic, activates an alternative metabolite pathways wherein the products are toxic. For example in case of PKU toxic phenylketones are formed because of the interference in the normal neurological development.
- Impaired circulation that allows metabolic by-products to accumulate to toxic levels. Normally, cells produce substances at normal levels. For example, carbon dioxide and bilirubin. However, when these substances are not removed from the cells and excreted out of the body their levels rises and can cause extensive damage to the cells. Cell injury from these accumulated substances that are normally tolerated in normal levels is secondary to the impaired circulation that has interfered with their normal removal in the cell.