Host Defense Mechanisms in Microbial Infection: A Critique
Certain aspects of the chapter, Host Defense Mechanisms in Microbial Infection, are outstanding. Other features, however, might bear improvement. For instance, one or two of the chapter's illustrations could possibly cause confusion.
Chapter 6 begins with a very broad delineation of the human body's defense mechanisms. It states that there are both nonspecific and specific defenses. The nonspecific defenses are directed against foreign agents; whereas, the specific defenses are designed to fend off parasitic microorganisms. The chapter then embarks on an analysis of the body's nonspecific defense mechanisms. The content of this first section is very good. The following different types of defense mechanisms are mentioned: (1) entrance barriers; (2) blood barriers; (3) the lymphatic system; (4) the mononuclear phagocyte system (MNPS); (4) phagocytosis; and (5) the inflammatory response (1:112-121). Entrance barriers include both the skin and mucus membranes. The chapter includes a thorough review of skin anatomy and physiology. It also describes how the epithelia of certain internal organs such as the stomach and genitourinary tract provides protection. The subsection ends by describing how even minor wounds can compromise entrance barriers.
The second type of nonspecific resistance mechanism discussed is the blood. The chapter notes that by merely circulating the blood provides tissues with oxygen and nutrients, and thus renders them less susceptible to infection. Moreover, the subsection separates blood into its plasma and cellular constituents. Antimicrobial agents in the plasma include the immunoglobulins, the gamma globulins, antibodies, and complement. In contrast, the primary cellular blood elements involved in nonspecific resistance are the white blood cells. The chapter discusses different types of white cells. For instance, it mention...