Why Do Infections Occur?

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Why do infections occur? * Each pathogen is meant for a certain type of body tissue and they have the ability to affect only those tissues. * For example: The polio virus could enter the body in a large amount and could come into contact with the mucous membranes lining the respiratory and digestive tracts, but it only attacks the nervous tissue. The cause of AIDS, the HIV virus, only attacks the T cell. * The portal of entry basically speaks for itself. It’s the entrance in which the pathogen enters body. * For example: A very common entrance for pathogens is the respiratory tract. Other routes such as the digestive system and the tubes that open to the urinary and reproductive system are also important entrances. * A break in the skin or mucous membrane can cause organisms to access deeper tissues and lead to infection. Bacteria such staphylococci may enter the body this way. * The virulence is the organism’s power to overcome its host’s defenses. * The two parts of an organism’s virulence are: Invasive power (aggressiveness) and the ability to produce toxins (poisons) that damage the body. Virulence varies in organisms and some also have the ability to change their virulence. They may also gain virulence as they go from one infected host to another. * The dose is the amount of pathogens that attack the body. Infection may occur even when the virulence is low, but a large number of pathogens attack the body. * Predisposition is a person’s condition to infection. That condition can be influenced by physical and emotional health, their diet, living habits, and age. Nonspecific defenses * Chemical and Mechanical barriers The body’s first line of defenses against attackers includes the skin, mucous membranes, body secretions, and certain reflexes. * Skin- It is an automatic barrier as long as it remains

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