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# 24.1: Nonspecific Defenses

Difficulty Level: At Grade Created by: CK-12

## Lesson 24.1: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is 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 histakines and cytomines.

_____ 12. Biological barriers include millions of harmless bacteria live on the human skin.

## Lesson 24.1: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

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? (From top to bottom, images courtesy of Rocky Mountain Laboratories/NIAID/NIH and under the public domain, courtesy of CDC/Dr. Erskine Palmer and under the public domain, courtesy of Archenzo and under GNU-FDL 1.2, and courtesy of CDC/Janice Carr and under the public domain. Composite created by CK-12 Foundation.)

Mechanical Barriers

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

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

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.

Questions

1. What is a pathogen? Which type of pathogen causes the common cold? Which type causes athlete’s foot?

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2. What is meant by The First Line of Defense?

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3. What is a mechanical barrier? Give an example.

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4. What is a chemical barrier? Give an example.

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5. What is a biological barrier? Give an example.

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## Lesson 24.1: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

1. Which statement best describes the immune system?
1. The immune system produces gametes.
2. The immune system exchanges gases between the blood and lungs.
3. The immune system protects the body from pathogens.
4. The immune system digests food into usable nutrients.
2. The immune system is comprised of ___________ lines of defense.
1. two
2. three
3. four
4. five
3. Which statement best describes the first line of defense?
1. The first line of defense consists of different types of barriers that keep most pathogens out of the body.
2. The first line of defense includes the inflammatory response.
3. Leukocytes are the cells responsible for the first line of defense.
4. The first line of defense includes the skin, mucous membranes and biological barriers such as white blood cells.
4. Which statements are true about mechanical barriers? (1) Mechanical barriers physically block pathogens from entering the body. (2) The skin is the most important mechanical barrier. (3) Mechanical barriers are living organisms that help protect the body. (4) Mechanical barriers destroy pathogens on the outer body surface.
1. 1 and 2
2. 3 and 4
3. 1, 2, and 3
4. 1, 2, 3, and 4
5. Which statement describes the second line of defense?
1. The second line of defense includes biological and chemical barriers.
2. The skin is the major organ of the second line of defense.
3. The second line of defense keeps most pathogens out of the body.
4. The second line of defense is encountered by pathogens that enter the body.
6. What is the inflammatory response?
1. The inflammatory response begins when cytokines or histamines infect a tissue.
2. The inflammatory response is the first reaction of the body to tissue damage or infection.
3. The inflammatory response is a chemical barrier that destroys pathogens on the body surface.
4. none of the above
7. Leukocytes
1. are red blood cells that bring extra oxygen to the site of infection.
2. are biological barriers that help protect the body.
3. are white blood cells that fight infections and get rid of debris.
4. are released by mucous membranes at body openings.
8. Phagocytosis
1. is the process in which leukocytes engulf and break down pathogens and debris.
2. are chemical barriers destroy pathogens.
3. are part of the first line of defense.
4. all of the above

## Lesson 24.1: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.

Definitions

_____ 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. destroy pathogens on the outer body surface, at body openings, and on inner body linings

_____ 9. the first reaction of the body to tissue damage or infection

_____ 10. physically block pathogens from entering the body

_____ 11. protects the body from worms, germs, and other agents of harm

_____ 12. sweep mucus and pathogens toward body openings

Terms

a. biological barriers

b. chemical barriers

c. cilia

d. immune system

e. inflammatory response

f. leukocyte

g. mechanical barriers

h. mucous membrane

i. mucus

j. pathogens

k. phagocytosis

l. skin

## Lesson 24.1: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. ____________ are disease-causing agents, such as bacteria and viruses.

2. ____________ is the process in which cells engulf and break down pathogens and debris.

3. The skin____________ is the single most important defense the body has.

4. The ____________ response is the first reaction of the body to tissue damage or infection.

5. ____________ membranes secrete mucus, a slimy substance that traps pathogens.

6. ____________ barriers destroy pathogens on the outer body surface.

7. Leukocytes are ____________ blood cells that fight infections and get rid of debris.

8. A ____________ defense is tailored to a particular pathogen.

9. A ____________ defense is the same no matter what type of pathogen is involved.

10. Millions of harmless ____________ live on the human skin.

11. Mucous membranes provide a ____________ barrier at body openings.

12. Sweat, mucus, tears, and saliva all contain ____________ that kill pathogens.

13. The ____________ line of defense attacks pathogens that manage to enter the body.

14. Barriers that keep out pathogens are the body’s ____________ line of defense.

## Lesson 24.1: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Describe the barriers that keep most pathogens out of the human body.

Feb 23, 2012

## Last Modified:

Oct 07, 2015
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