Several scientific terms are relatively easy to define, others tend to be more difficult; “health” and “disease” fall under the latter category. Many suggest that “disease” is merely a disorder of a system’s normal functions while “health” is the absence of disease. On the other hand, could a person whose bodily systems are functioning properly but who is unhappy or depressed be considered healthy? Can an alcoholic or drug-addict whose habit has not as yet caused any physical harm be likewise described? Without a doubt, health is more than just a well-being physically; it involves social and mental well-being as well.
Health clearly being difficult to define and understand, “disease” is thought to be even more complex. Doctors, scientists, and researchers try enduring the problem in classifying diseases. Although a number of diseases fit neatly and entirely into one category, some seem to belong to more than one group and nevertheless some even combine elements of all types. Having all this in mind, six categories are frequently recognized: infections, inherited, degenerative, mental, human inflicted, and deficiency. From these six categories, “any disease may be acute…or chronic” (Susan 627). When a disease is acute, it means that it may appear suddenly and have a short time period while a disease that is chronic is the total opposite; it may develop slowly and be persistent. A disease may be the result of environmental influences such as radiation or pollution or it may not even have an apparent cause. Other diseases have a serious of risk factors, each factor increasing the chance of developing that illness. Finally, the life-style often impacts greatly on a particular disease.
Communicable diseases that can be passed on from one individual to another are known as infections. An infection is a “pathological state resulting from the invasion of the body by pathogenic microorganisms” (Miller 1), where a pathogen is a microorganism that causes a disease. For a microorganism to be considered a pathogen, it must “gain entry to the most, colonize the tissues of the host, resist the defenses of the host, and cause damage to the host tissues” (Susan 628).
For a pathogen to enter can be broadly done in two ways: via the skin or through natural openings. The skin being thick and continuously regenerating creates an effective barrier to pathogens. It is when there are cuts and abrasions where an entry can occur. Another way an entry of a pathogen through the skin can be no thanks to the biting of insects such as mosquitoes, lice and fleas, or bites and scratches from animals may also allow entry. As for the entry of pathogen through natural openings, it occurs by many means. Many infectious diseases are respiratory, thus infect via the air inhaled along the respiratory system. Consumption of food and water may carry the agents into the stomach and intestines via the mouth. The last method would be through the genital and urinary openings, the most common where pathogens are easily transmitted is during sexual intercourse (Susan 628).
The following step for a microorganism to be considered a pathogen is for it to colonize the tissue of the host. Pathogens need to “fix” themselves at the site of their infection. This is done through a combination of physical modifications or chemical means. As soon as the pathogen has been modified, the multiplication of that pathogen occurs rapidly. Some of these pathogens produce toxins causing irritation, leading to responses such as scratching, coughing, and sneezing. These responses aid the infection to spread to unaffected areas. Enzymes that are produced by pathogens after being “fixed” are able to penetrate into cells and slowly invading a tissue. After the pathogen is colonized in the tissue of the host, it will resist the host’s defenses. This is done by resisting ingestion by phagocytes, avoiding digestion if ingested by a phagocyte, or destroying the phagocyte. A...
Cited: Toole, Susan. Biology For Advanced Level. Fourth Edition. London: Stanely Thornes, 1999. Print.
Urry, Lisa. Biology Volume 1. Custom Edition for Lone Star College – CyFair. San Franciso, California: Pearson Education, Inc. 2008.
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