![]() ![]() It consists of dead cells that are constantly shed from the body surface, a process that helps remove bacteria and other infectious agents that have adhered to the skin. #IMMUNE SYSTEM CELLS SKIN#The outer layer of skin - the epidermis - is tough, and very difficult for pathogens to penetrate. ![]() In fact, it is the single most important defense the body has. The skin is the most important mechanical barrier. Mechanical barriers are the first line of defense against pathogens, and they physically block pathogens from entering the body. Mechanical Barriers Figure 17.4.2 Nasal hairs are a mechanical barrier to larger particles in the air. The types of barriers are mechanical, chemical, and biological barriers. The body’s first line of defense consists of three different types of barriers that keep most pathogens out of body tissues. Alternatively, the other innate defenses may be triggered when damaged, injured, or stressed cells send out alarm signals, many of which are recognized by the same receptors as those that recognize pathogens. These receptors recognize molecules that are broadly shared by pathogens, but distinguishable from host molecules. ![]() The triggering event is usually the identification of pathogens by pattern-recognition receptors on cells of the innate immune system. If these barriers fail, then other innate defenses are triggered. Surface barriers of various types generally keep most pathogens out of the body. In humans, the innate immune system includes surface barriers, inflammation, the complement system, and a variety of cellular responses. Other than most vertebrates (including humans), the innate immune system is the only system of host defense. In most organisms, the innate immune system is the dominant system of host defense. Although the innate immune system provides immediate and rapid defenses against pathogens, it does not confer long-lasting immunity to them. The innate system responds in the same general way to every pathogen it encounters. Innate responses are generic, rather than tailored to a particular pathogen. The innate immune system is a subset of the human immune system that produces rapid, but non-specific responses to pathogens. Chapter 1 - Nature and Processes of Scienceġ.1 Case Study: Why Should You Learn About Science?ġ.7 Pseudoscience and Other Misuses of Scienceġ.8 Case Study Conclusion: To Give a Shot or NotĢ.1 Case Study: Why Should You Study Human Biology?Ģ.6 Case Study Conclusion: Our Invisible InhabitantsĤ.14 Case Study Conclusion: More Than Just Tiredĥ.10 Mendel's Experiments and Laws of Inheritanceĥ.12 Sexual Reproduction, Meiosis, and Gametogenesisĥ.18 Case Study Conclusion: Cancer in the FamilyĦ.1 Case Study: Our Similarities and DifferencesĦ.4 Human Responses to Environmental StressĦ.9 Case Study Conclusion: Your Genes May Help You Save a Lifeħ.9 Case Study Conclusion: Under PressureĨ.1 Case Study: The Control Centre of Your Bodyġ0.1 Case Study: Skin, Hair, and Nails - Decorative but Functionalġ0.2 Introduction to the Integumentary Systemġ0.8 Case Study Conclusion: Wearing His Heart on His Sleeveġ1.8 Case Study Conclusion: A Pain in the Footġ2.7 Case Study Conclusion: Needing to Relaxġ3.1 Case Study: Respiratory System and Gas Exchangeġ3.2 Structure and Function of the Respiratory Systemġ3.7 Case Study Conclusion: Cough That Won't Quitġ4.1 Case Study: Your Body's Transportation Systemġ4.2 Introduction to the Cardiovascular Systemġ5.2 Introduction to the Digestive Systemġ5.7 Disorders of the Gastrointestinal Tractġ5.8 Case Study Conclusion: Please Don’t Pass the Breadġ6.5 Ureters, Urinary Bladder, and Urethraġ6.7 Case Study Conclusion: Drink and Flushġ7.7 Case Study Conclusion: Defending Your Defensesġ8.2 Introduction to the Reproductive Systemġ8.3 Structures of the Male Reproductive Systemġ8.4 Functions of the Male Reproductive Systemġ8.5 Disorders of the Male Reproductive Systemġ8.6 Structures of the Female Reproductive Systemġ8.7 Functions of the Female Reproductive Systemġ8.9 Disorders of the Female Reproductive Systemġ8.12 Case Study Conclusion: Trying to ConceiveĬhapter 1 Answers: Nature and Processes of ScienceĬhapter 2 Answers: Biology: The Study of LifeĬhapter 7 Answers: Introduction to the Human BodyĬhapter 14 Answers: Cardiovascular System ![]()
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