TRUE OR FALSE?
_____ 1. The skin is the single most important defense the body has. _____ 2. Sneezing removes pathogens from your nose.
_____ 3. Sweat, mucus, tears, and saliva are all types of mechanical barriers used to protect you. _____ 4. The inflammatory response is part of the body’s first line of defense. _____ 5. Leukocytes are white blood cells that fight infections and get rid of debris. _____ 6. Barriers that keep out pathogens are the body’s first line of defense. _____ 7. The second line of defense attacks pathogens that manage to enter the body. _____ 8. The second line of defense includes mechanical, chemical, and biological barriers. _____ 9. The first line of defense includes the inflammatory response and phagocytosis. _____ 10. A nonspecific defense can be tailored to a particular pathogen. _____ 11. The inflammatory response is triggered by chemicals called histamines and cytokines. _____ 12. Biological barriers include millions of harmless bacteria live on the human skin.
The First Line of Defense
The body’s first line of defense consists of different types of barriers that keep most pathogens out of the body. Pathogens are disease-causing agents, such as bacteria and viruses. These and other types of pathogens are described in the figure below. Regardless of the type of pathogen, however, the first line of defense is always the same.
Types of pathogens that commonly cause human diseases include bacteria, viruses, fungi, and protozoa. Which type of pathogen causes the common cold? Which type causes athlete’s foot? (
Mechanical barriers physically block pathogens from entering the body. The skin is the most important mechanical barrier. In fact, it is the single most important defense the body has. The outer layer of the skin is tough and very difficult for pathogens to penetrate. Mucous membranes provide a mechanical barrier at body openings. They also line the respiratory, GI, urinary, and reproductive tracts. Mucous membranes secrete mucus, a slimy substance that traps pathogens. The membranes also have hair-like cilia. The cilia sweep mucus and pathogens toward body openings where they can be removed from the body. When you sneeze or cough, pathogens are removed from the nose and throat. Tears wash pathogens from the eyes, and urine flushes pathogens out of the urinary tract.
Chemical barriers destroy pathogens on the outer body surface, at body openings, and on inner body linings. Sweat, mucus, tears, and saliva all contain enzymes that kill pathogens. Urine is too acidic for many pathogens, and semen contains zinc, which most pathogens cannot tolerate. In addition, stomach acid kills pathogens that enter the GI tract in food or water.
Biological barriers are living organisms that help protect the body. Millions of harmless bacteria live on the human skin. Many more live in the GI tract. The harmless bacteria use up food and space so harmful bacteria cannot grow.
1. What is a pathogen? Which type of pathogen causes the common cold? Which type causes athlete’s foot? List at least 5 bacterial pathogens and 5 viral pathogens that are not listed in the figure above.
2. What is meant by The First Line of Defense?
3. What is a mechanical barrier? Give an example.
4. What is a chemical barrier? Give an example.
5. What is a biological barrier? Give an example.
Match the vocabulary word with the proper definition.
_____ 1. provide a mechanical barrier at body openings
_____ 2. disease-causing agents
_____ 3. a type of white blood cell
_____ 4. living organisms that help protect the body
_____ 5. the most important mechanical barrier
_____ 6. a slimy substance that traps pathogens
_____ 7. the process in which leukocytes engulf pathogens
_____ 8. destroys pathogens on the outer body surface, at body openings, and on inner body...