Describe at least three physical mechanisms that are part of the first line of defense
What will be an ideal response?
Physical mechanisms include the skin, the mucous membranes, and the variety of fluids that are produced by the body. The skin acts as a key element in the first line of defense for several reasons. First, the skin has many layers of protection that few microbes can penetrate. Second, these layers are shed, removing potential pathogens. Third, the epidermis has epidermal dendritic cells that are phagocytic. The mucous membranes also play a role for a variety of reasons. They contain tightly packed cells that are continually shed and replaced. In addition, the production of mucus acts to trap pathogens, and the cilia, which are often present, beat synchronously to remove microbes. Bodily fluids serve to dilute and wash away microbes. These fluids include tears, saliva, urine, vaginal secretions, blood, and menstrual flow. Other physical processes include defecation and vomiting.
Bloom's Taxonomy: Comprehension
Section: The Body's First Line of Defense
Learning Outcome: 15.3, 15.5, 15.6
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