Physical barriers that prevent entry of microorganisms into the body include the skin and mucous membranes. Various antimicrobial substances, including lysozyme, peroxidase enzymes, lactoferrin, and defensins are found on the body surfaces. The normal flora plays a protective role by excluding certain other microbes.
■ What is peristalsis?
■ What is the role of lactoferrin?
■ How would damage to the ciliated cells of the respiratory tract predispose a person to infection?
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