A client exhibits all of the following during a physical assessment. Which of these is considered a primary defense against infection?
A. Fever
B. Intact skin
C. Inflammation
D. Lethargy
Correct Answer: B. Intact skin
Intact skin is considered a primary defense against infection. Usually, the skin prevents invasion by microorganisms unless it is damaged (for example, by an injury, insect bite, or burn). Mucous membranes, such as the lining of the mouth, nose, and eyelids, are also effective barriers. Typically, mucous membranes are coated with secretions that fight microorganisms. For example, the mucous membranes of the eyes are bathed in tears, which contain an enzyme called lysozyme that attacks bacteria and helps protect the eyes from infection. Fever, the inflammatory response, and phagocytosis (a process of killing pathogens) are considered secondary defenses against infection.
Option A: Body temperature increases as a protective response to infection and injury. An elevated body temperature (fever) enhances the body’s defense mechanisms, although it can cause discomfort. A part of the brain called the hypothalamus controls body temperature. Fever results from an actual resetting of the hypothalamus’s thermostat. The body raises its temperature to a higher level by moving (shunting) blood from the skin surface to the interior of the body, thus reducing heat loss.
Option C: Any injury, including an invasion by microorganisms, causes inflammation in the affected area. Inflammation, a complex reaction, results from many different conditions. During inflammation, the blood supply increases, helping carry immune cells to the affected area. Because of the increased blood flow, an infected area near the surface of the body becomes red and warm. The walls of blood vessels become more porous, allowing fluid and white blood cells to pass into the affected tissue. The increase in fluid causes the inflamed tissue to swell. The white blood cells attack the invading microorganisms and release substances that continue the process of inflammation.
Option D: Lethargy refers to a state of lacking energy. People who are experiencing fatigue or tiredness can also be said to be lethargic because of low energy. The same medical conditions that can lead to tiredness or fatigue can also lead to lethargy.