Chapter 43 - The body’s defenses. After reading this chapter and attending lecture, the student should be able to: Explain what is meant by nonspecific defense, and list the nonspecific lines of defense in the vertebrate body, explain how the physical barrier of skin is reinforced by chemical defenses, explain how the function of natural killer cells differs from the function of phagocytes,. | CHAPTER 43 THE BODY’S DEFENSES Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: Nonspecific Defenses Against Infection 1. The skin and mucus membranes provide first-line barriers to infection 2. Phagocytic cells, inflammation, and antimicrobial proteins function early in infection An animal must defend itself against unwelcome intruders -- the many potentially dangerous viruses, bacteria, and other pathogens it encounters in the air, in food, and in water. It must also deal with abnormal body cells, which, in some cases, may develop into cancer. Introduction Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Three cooperative lines of defense have evolved to counter these threats. Two of these are nonspecific -- that is, they do not distinguish one infectious agent from another. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. The first line of nonspecific defense is external, consisting of epithelial cells that cover and line our bodies and the secretions they produce. The second line of nonspecific defense is internal, involving phagocytic cells and antimicrobial proteins that indiscriminately attack invaders that penetrate the body’s outer barriers. The third line of defense, the immune system, responds in a specific way to particular toxins, microorganisms, aberrant body cells, and other substances marked by foreign molecules. Specific defensive proteins called antibodies are produced by lymphocytes. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings An invading microbe must penetrate the external barrier formed by the skin and mucous membranes, which cover the surface and line the openings of an animal’s body. If it succeeds, the pathogen encounters the second line of nonspecific defense, interacting mechanisms that include phagocytosis, the inflammatory response, and antimicrobial proteins. Copyright © 2002 Pearson Education, Inc., publishing | CHAPTER 43 THE BODY’S DEFENSES Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: Nonspecific Defenses Against Infection 1. The skin and mucus membranes provide first-line barriers to infection 2. Phagocytic cells, inflammation, and antimicrobial proteins function early in infection An animal must defend itself against unwelcome intruders -- the many potentially dangerous viruses, bacteria, and other pathogens it encounters in the air, in food, and in water. It must also deal with abnormal body cells, which, in some cases, may develop into cancer. Introduction Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Three cooperative lines of defense have evolved to counter these threats. Two of these are nonspecific -- that is, they do not distinguish one infectious agent from another. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. The first line of nonspecific defense is external, consisting of
