HTH 245 Lecture 12: Key Concepts- Chapter 12
Document Summary
The immune system functions to recognize and destroy that which is foreign, including invading microbes and their secretions, toxins, and enzymes. Functionally, the immune system consists of two components: nonspeci c or innate (inherent) immunity and speci c or adapted (acquired after birth) immunity (figure 12. 1). The major structures of the immune system are shown in figure 12. 2. The body possesses a variety of innate mechanical and chemical barriers to infection. Skin is the rst line of defense against microbial infection; it is a physical barrier that blocks the entry of microbes. The barrier formed by skin may be broken by cuts and abrasions, insect bites, and injections with hypodermic needles, etc. Mucous membranes line the internal body cavities and act as a mechanical barrier to microbes. Cilia in airways propel microbes into the pharynx where they are swallowed and expelled (mucosal-ciliary escalator system).
