When paramedics rush to the aid of an injured person, they

Transcription

1 Section The Respiratory System 1 FOCUS Objectives Describe respiration Identify the function of the respiratory system Describe gas exchange and breathing Explain how smoking affects the respiratory system. Vocabulary Preview Call students attention to the Vocabulary terms. Ask: Which term refers to a respiratory disease? (Emphysema) Which term refers to a toxic chemical in tobacco smoke? (Nicotine) Point out that all the rest of the words are structures of the respiratory system. Reading Strategy Before students read the section, have them predict how respiration, gas exchange, and breathing are related. As they read, they should check to see if their predictions were correct. 2 INSTRUCT What Is Respiration? Address Misconceptions Students may have the misconception that breathing is the same as respiration. Remind students that respiration is the exchange of gases that takes place in the alveoli of the lungs. Breathing is the movement of air into and out of the lungs. Ask: How is breathing related to respiration? (Inhaling provides a fresh supply of oxygen to the lungs; exhaling removes excess carbon dioxide from the lungs.) Key Concepts What is the function of the respiratory system? How does smoking affect the respiratory system? Vocabulary pharynx trachea larynx bronchus alveolus diaphragm nicotine emphysema Reading Strategy: Monitoring Your Understanding Make a table with three columns labeled K, W, and L. Before you read, write what you know about respiration in column K and what you want to learn in column W. After you read, write what you have learned in column L. (magnification: 5600 ) SECTION RESOURCES When paramedics rush to the aid of an injured person, they check to see if the person is breathing. If the person s chest is not rising and falling and they cannot feel or hear air being exhaled from the mouth or nose, it is likely that the person is not breathing. Paramedics will ignore broken bones or burns to focus on breathing because there is no time to lose! If breathing stops for more than a few minutes, a life may be lost. Paramedics can do mouth-to-mouth rescue breathing to force air into the lungs. They can do chest compressions to keep the blood circulating. Cardiopulmonary resuscitation, or CPR, is rescue breathing combined with chest compressions. What Is Respiration? In biology, the word respiration is used in two slightly different ways. Cellular respiration, which takes place in mitochondria, is the release of energy from the breakdown of food molecules in the presence of oxygen. Without oxygen, cells lose much of their ability to produce ATP. Without ATP, cells cannot synthesize new molecules, pump ions, or carry nerve impulses. The blood carries oxygen from the lungs to the body s tissues, and carries carbon dioxide a waste product of cellular respiration in the opposite direction. At the level of the organism, respiration means the process of gas exchange the release of carbon dioxide and the uptake of oxygen between the lungs and the environment. The Human Respiratory System The basic function performed by the human respiratory system is remarkably simple to bring about the exchange of oxygen and carbon dioxide between the blood, the air, and tissues. With each breath, air enters the body through the air passageways and fills the lungs, where gas exchange takes place. The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs. Figure shows the structures of the respiratory system. Air moves through the nose to a tube at the back of the mouth called the pharynx, or throat. The pharynx serves as a passageway for both air and food. Air moves from the pharynx into the trachea, or windpipe. A flap of tissue called the epiglottis covers the entrance to the trachea when you swallow. Figure In this cross section of the trachea, the cilia have been colored green. Inferring What is the role of cilia in the respiratory system? Print: Laboratory Manual A, Chapter 37 Lab Teaching Resources, Lesson Plan 37 3, Adapted Section Summary 37 3, Adapted Worksheets 37 3, Section Summary 37 3, Worksheets 37 3, Section Review 37 3 Reading and Study Workbook A, Section 37 3 Adapted Reading and Study Workbook B, Section 37 3 Issues and Decision Making, Issues and Decisions 41 Lab Worksheets, Chapter 37 Design an Experiment Technology: itext, Section 37 3 Animated Biological Concepts DVD, 42 Human Respiration Transparencies Plus, Section Chapter 37

2 FIGURE THE RESPIRATORY SYSTEM The respiratory system is responsible for the exchange of oxygen and carbon dioxide. Air moves through the nose, pharynx, larynx, trachea, and lungs. After reaching the lungs, the trachea branches into smaller and smaller tubes called bronchioles, which end in alveoli, or air sacs. Nose Mouth Epiglottis Diaphragm Edge of pleural membrane Pharynx Larynx Trachea Lung Bronchus Bronchioles Pulmonary artery Pulmonary vein Capillaries Bronchiole Alveoli The Human Respiratory System Use Visuals Figure Make sure students understand how the drawing on the right relates to the drawing on the left. Have students use the drawings to trace the pathway of air through the respiratory system as they read about it in the text. They should identify each of the structures through which the air passes, starting with the nose and ending with the alveoli. Use Community Resources Invite a paramedic to demonstrate to the class rescue breathing (mouth-tomouth) and chest compressions. Before the paramedic arrives, tell students that people sometimes stop breathing in cases of drowning, electric shock, or smoke inhalation and that rescue breathing helps keep them alive until they begin breathing again on their own. Also explain how choking occurs because of the role of the pharynx in both the digestive and respiratory systems. Suggest that students prepare questions in advance for the paramedic to address. Cilia and Mucus The respiratory passageways allow air to pass directly into some of the most delicate tissues in the body. To keep the lung tissue healthy, air entering the respiratory system must be warmed, moistened, and filtered. Large dust particles get trapped by the hairs lining the entrance to the nasal cavity. Some of the cells that line the respiratory system produce a thin layer of mucus. The mucus moistens the air and traps inhaled particles of dust or smoke. Cilia sweep the trapped particles and mucus away from the lungs toward the pharynx. The mucus and trapped particles are either swallowed or spit out. These protective measures help keep the lungs clean and open for the important work of gas exchange. What is the pharynx? SUPPORT FOR ENGLISH LANGUAGE LEARNERS Vocabulary: Link to Visual Beginning Use Figure to help students visualize the meaning of the terms pharynx, trachea, larynx, bronchus, and diaphragm. Point out each of the structures as you model the proper pronunciation of each term. Then, distribute an unlabeled diagram similar to Figure 37 13, and have students label the pharynx, trachea, larynx, bronchus, and diaphragm. Post these terms on a word wall with other Vocabulary terms from the chapter. Intermediate Students should start by doing the beginning-level activity. Then, pair the ESL students with English-proficient students to write five sentences describing the functions of the pharynx, trachea, larynx, bronchus, and diaphragm in their own words. Ask for volunteers to read their sentences. Answers to... The pharynx is a tube at the back of the mouth that serves as a passageway for both air and food. Figure Cilia sweep mucus and trapped particles away from the lungs toward the pharynx. Circulatory and Respiratory Systems 957

3 37 3 (continued) Gas Exchange Build Science Skills Inferring Explain how exhaled air is used in rescue breathing. Point out that exhaled air has already gone through the gas exchange process in the lungs. Ask: How can rescue breathing provide the person receiving the second-hand air with enough oxygen to survive? (Exhaled air contains about 75 percent of the oxygen of inhaled air more than enough to keep a person alive.) Demonstration Make limewater in a clear glass container by adding calcium hydroxide to water until the solution is saturated. Tell students that when carbon dioxide reacts with limewater, it causes the limewater to turn cloudy. Have a student volunteer exhale through a straw into the limewater. (Caution the student not to suck any of the limewater through the straw.) While the student exhales, have other students observe what happens. (The limewater turns cloudy.) Ask: Why did the limewater turn cloudy? (The exhaled breath contained carbon dioxide.) Breathing Build Science Skills Measuring Students can measure their lung capacity. (Advise any with respiratory illnesses, such as asthma or bronchitis, to avoid participating.) Give each student a large round balloon and, with students working in pairs, tell one student to inhale as large a breath as possible and then to exhale it as completely as possible into the balloon. Students should hold the balloons shut until their partner measures the circumference with a tape measure. Then, repeat the steps for the other partner. Students can calculate their lung capacity by finding the volume of the inflated balloon, using the formula V 4/3 r 3, where r is the radius of the inflated balloon. The radius can be found from the circumference, using the formula c 2 r. Figure Gas exchange occurs by diffusion across the membrane of an alveolus and a capillary. Drawing Conclusions Where is oxygen more concentrated, in an alveolus or in a capillary? Bronchiole O 2 CO 2 Capillary The Larynx At the top of the trachea is the larynx. The larynx contains two highly elastic folds of tissue known as the vocal cords. When muscles pull the vocal cords together, the air moving between them causes the cords to vibrate and produce sounds. Your ability to speak, shout, and sing comes from these tissues. The Bronchi From the larynx, air passes through the trachea into two large passageways in the chest cavity called bronchi (singular: bronchus). Each bronchus leads into one of the lungs. Within each lung, the large bronchus subdivides into smaller bronchi, which lead to even smaller passageways called bronchioles. Air moving along this path can be compared to a motorist who takes an exit off an eight-lane highway onto a four-lane highway, makes a turn onto a two-lane road, and ends up on a narrow country lane. The bronchi and bronchioles are surrounded by smooth muscle that helps to support them and enables the autonomic nervous system to regulate the size of the air passageways. The bronchioles continue to subdivide until they reach a series of dead ends millions of tiny air sacs called alveoli (singular: alveolus). Alveoli are grouped in little clusters, like bunches of grapes. A delicate network of thin-walled capillaries surrounds each alveolus. Alveoli Gas Exchange There are about 150 million alveoli in each healthy lung, providing an enormous surface area for gas exchange. Oxygen dissolves in the moisture on the inner surface of the alveoli and then diffuses across the thin-walled capillaries into the blood. Carbon dioxide in the bloodstream diffuses in the opposite direction, across the membrane of an alveolus and into the air within it. This process is illustrated in Figure The process of gas exchange in the lungs is very efficient. The air that you inhale usually contains 21 percent oxygen and 0.04 percent carbon dioxide. Exhaled air usually contains less than 15 percent oxygen and 4 percent carbon dioxide. The lungs remove about one fourth of the oxygen in the air that you inhale and increase the carbon dioxide content of that air by a factor of 100. Because oxygen dissolves easily, you may wonder why hemoglobin, the oxygen-carrying protein in blood, is needed at all. The reason is efficiency. Hemoglobin binds with so much oxygen that it increases the oxygen-carrying capacity of the blood more than 60 times. Without hemoglobin to carry the oxygen that it uses, your body might need as much as 300 liters of blood to get the same result! 958 Chapter 37

4 Breathing Careers in Biology Respiratory Care Practitioner Job Description: provide care for patients with respiratory problems in hospitals, clinics, nursing homes, schools, and at home Education: a two-year or four-year training program; certification exams; individual states have additional licensing requirements Skills: good communication skills; enjoy working with people; capable of working independently; good decision-making skills; knowledge of anatomy, physiology, microbiology Highlights: You provide quick responses in emergency situations. You work as a member of a team. Breathing is the movement of air into and out of the lungs. Surprisingly, there are no muscles connected to the lungs. The force that drives air into the lungs comes from ordinary air pressure. How does the body use this force to inflate the lungs? The lungs are sealed in two sacs, called the pleural membranes, inside the chest cavity. At the bottom of the cavity is a large, flat muscle known as the diaphragm. As Figure shows, when you breathe in, or inhale, the diaphragm contracts and the rib cage rises up. This expands the volume of the chest cavity. Because the chest cavity is tightly sealed, this creates a partial vacuum inside the cavity. Atmospheric pressure does the rest, filling the lungs as air rushes into the breathing passages. Most of the time, exhaling is a passive event. When the rib cage lowers and the diaphragm muscle relaxes, the pressure in the chest cavity becomes greater than atmospheric pressure. Air rushes back out of the lungs. To blow out a candle, you need a greater force. Muscles surrounding the chest cavity provide that extra force, contracting vigorously just as the diaphragm relaxes. For: The Process of Breathing activity Visit: PHSchool.com Web Code: cbp-0373 For: Career links Visit: PHSchool.com Web Code: cbb-0373 Air inhaled Rib cage rises Diaphragm Air exhaled Rib cage lowers Diaphragm Inhalation Exhalation Figure During inhalation the rib cage rises and the diaphragm contracts, increasing the size of the chest cavity. Interpreting Graphics What happens as the diaphragm relaxes? Careers in Biology Explain that most respiratory care practitioners work in hospitals and that many hospitals have separate respiratory care departments. Describe some of the specific job duties of respiratory care practitioners, including maintaining and operating various kinds of breathing equipment, leading aerobic exercise classes, and conducting smoking cessation programs. Resources For additional information on this career, students can contact the National Board for Respiratory Care or the American Association for Respiratory Care, or they can contact the respiratory care department of a local hospital. You can have students write a more extensive job description as well as list the educational requirements for a career in this field. For: The Process of Breathing activity Visit: PHSchool.com Web Code: cbe-0373 Students explore the events involved during the breathing process. 959 TEACHER TO TEACHER To impress on the students the surface area of the human lungs, I give them this Gee Whiz fact. The surface area of the 300 million alveoli in the human lungs would cover 70 square meters. That s about the size of an average classroom (measuring 25 feet by 25 feet). I also describe to the class the role of the surfactant cells in the alveoli that help keep the alveoli from collapsing. I tell them that the absence of surfactant in premature babies can cause breathing problems. To illustrate collapsed alveoli, I use plastic bags like the ones you get in the produce section of the grocery store that are so hard to open! Betsy Halpern Biology Teacher South Eugene High School Eugene, Oregon Answers to... Figure In an alveolus Figure As the diaphragm relaxes, the pressure in the chest cavity becomes greater than atmospheric pressure, so air rushes out of the lungs. Circulatory and Respiratory Systems 959

5 37 3 (continued) How Breathing Is Controlled Objective Students will be able to formulate a hypothesis about how breathing is affected by carbon dioxide. Skills Focus Drawing Conclusions, Inferring, Observing Materials seltzer tablet, plastic cup or 250-mL beaker, water Time 10 minutes Safety Get parental permission before doing this lab. Students who have breathing problems should not perform this lab. Students should remain seated while doing this lab. Strategies For best results use straight-sided plastic cups or beakers. Room-temperature water will produce more carbon dioxide. Expected Outcome Students should observe that inhaling carbon dioxide makes them feel short of breath and in need of more air. Analyze and Conclude 1. Students may say they felt short of breath or as if they needed more air. 2. If students hypothesized that they would feel out of breath, their hypothesis was supported. 3. The stimulus of increased carbon dioxide indicates that gases are not being exchanged in the lungs and, therefore, that the body is not receiving enough oxygen. The increase in carbon dioxide stimulated breathing, which both removes carbon dioxide and brings in oxygen. How does your body respond to increases in carbon dioxide? Materials seltzer tablet, plastic cup Procedure 1. Formulating Hypotheses Carbon dioxide is a waste material synthesized during the cellular process of respiration. Write a hypothesis about how your breathing will be affected if the level of carbon dioxide increases. 2. Place approximately 100 ml of water in the cup and add a seltzer tablet. The bubbles in the water are carbon dioxide. Bring the cup up to your face and inhale deeply. The system works only because the chest cavity is sealed. A puncture wound to the chest even if it does not affect the lungs directly may allow air to leak into the chest cavity and make breathing impossible. This is one of the reasons chest wounds are always serious. How Breathing Is Controlled You can control your breathing almost anytime you want, whether it s to blow up a balloon or to play a musical instrument. But this doesn t mean that breathing is purely voluntary. If you hold your breath for a minute or so, you ll see what happens. Your chest begins to feel tight, your throat begins to burn, and the muscles in your mouth and throat struggle to keep from breathing. Eventually your body takes over. It forces you to breathe! Breathing is such an important function that your nervous system will not let you have complete control over it. The part of the brain that controls breathing is the medulla oblongata. Autonomic nerves from the medulla oblongata to the diaphragm and chest muscles produce the cycles of contraction that bring air into the lungs. How does the medulla oblongata know when it s time to breathe? Cells in its breathing center monitor the amount of carbon dioxide in the blood. As the carbon dioxide level rises, nerve impulses from the breathing center cause the diaphragm to contract, bringing air into the lungs. The higher the carbon dioxide level, the stronger the impulses. If the carbon dioxide level reaches a critical point, the impulses become so powerful that you cannot keep from breathing. Analyze and Conclude 1. Observing Describe what happened when you inhaled the carbon dioxide. 2. Drawing Conclusions Did your results support your hypothesis or not? Explain your answer. 3. Inferring Why is it important for your body to respond to the stimulus of increased carbon dioxide? Build Science Skills Inferring Explain that extremely rapid or deep breathing, which is called hyperventilation, is caused by lower-than-normal levels of carbon dioxide in the blood. Point out that breathing into a paper bag for a few minutes can stop hyperventilation. Ask: Why does breathing into a paper bag stop hyperventilation? (It leads to a normal level of carbon dioxide in the blood, and this slows down the rate of breathing.) 960 Chapter 37 BIOLOGY UPDATE Asthma on the rise Asthma is a potentially fatal respiratory illness characterized by repeated asthmatic attacks, during which muscles surrounding the air passages that lead to the lungs contract. Constriction of the air passages makes it difficult to get enough air. It can also cause death in severe attacks. An estimated 5 to 10 percent of highschool students suffer from asthma. That number is higher than ever before and is still on the rise. Some scientists think that the increase in asthma may be partly due to air pollution. Laws regulating smokestack emissions and the use of coal have led to a reduction in industrial air pollution. However, air pollution from motorvehicle exhaust contains many substances that are harmful to the respiratory system, including carbon monoxide, carbon dioxide, nitrogen oxides, sulfur oxides, lead, and hydrocarbons.

6 Tobacco and the Respiratory System Demonstration Demonstrate to students how toxic tobacco is. Before class, make a tobacco solution by boiling tobacco in water for 15 minutes and then straining the solution through a paper towel. Allow the solution to cool. During class, spray the solution on a plant that is infested with aphids, and have students observe what happens. (The aphids die.) Ask: What do you think killed the aphids? (Something in the tobacco) Conclude by telling students that the nicotine in tobacco is so toxic that it is actually used as a pesticide. That the breathing center responds primarily to carbon dioxide can have dangerous consequences. Consider a plane flying at high altitude. Although the amount of oxygen in the air decreases as the altitude increases, the passengers do not need oxygen masks because the cabin is pressurized. Oxygen is available for use in an emergency, but the passengers often have to be told to begin breathing the oxygen. Although their bodies may be starving for oxygen, they have no more carbon dioxide in their blood than usual, so the breathing center does not sense a problem. The pilot in Figure is not in a pressurized cabin and must use an oxygen mask at high altitudes. What does the breathing center in the brain do? Tobacco and the Respiratory System The upper part of the respiratory system is generally able to filter out dust and foreign particles that could damage the lungs. Millions of people engage in an activity smoking tobacco that damages and eventually destroys this protective system. Substances in Tobacco Tobacco smoke contains many substances that affect the body. Three of the most dangerous substances are nicotine, carbon monoxide, and tar. Nicotine is a stimulant drug that increases the heart rate and blood pressure. Carbon monoxide is a poisonous gas that blocks the transport of oxygen by hemoglobin in the blood. It decreases the blood s ability to supply oxygen to its tissues, depriving the heart and other organs of the oxygen they need to function. Tar contains a number of compounds that have been shown to cause cancer. Figure This pilot must use an oxygen mask because there is not enough oxygen available in the air at high altitudes. Applying Concepts How would a mountain climber decide when to carry a supply of oxygen? Make Connections Chemistry Elaborate on how carbon monoxide in tobacco smoke blocks the transport of oxygen by the blood. Remind students that oxygen normally binds with the iron in hemoglobin molecules. Explain that when carbon monoxide is present in the blood, it binds with hemoglobin at the same site, but much more strongly, so the oxygen is not released to the cells where it is needed. Ask: Besides tobacco smoke, what are some other sources of carbon monoxide? (Possible answers include car exhausts and faulty fireplaces, gas furnaces, and other gas appliances.) FACTS AND FIGURES Smoking, cancer, and death A person who smokes cigarettes is 10 to 15 times more likely to develop lung cancer than a nonsmoker. The more cigarettes one smokes, the greater the chances of developing lung cancer and the more likely one is to die from lung cancer. If a person smokes two or more packs of cigarettes a day, he or she is 20 to 25 times more likely to die from lung cancer than a nonsmoker. Three of every four deaths from lung cancer in women are caused by smoking. Cancer is not the only risk that smokers face. Smokers are also three times more likely to die from a heart attack than nonsmokers. Men in their thirties who smoke can expect to lose about eight years of life if they do not quit smoking. Answers to... The breathing center monitors the amount of carbon dioxide in the blood. As the level rises, nerve impulses from the breathing center cause the diaphragm to contract. Figure The mountain climber would base the decision on the altitude of the mountain. Circulatory and Respiratory Systems 961

7 37 3 (continued) Use Community Resources Invite a respiratory care practitioner or other knowledgeable health professional to address the class on diseases of the respiratory system caused by smoking. Ask the speaker to describe symptoms of such diseases as chronic bronchitis and emphysema and how the diseases limit the activity and quality of life of people who have them. Also ask the speaker to describe how respiratory therapy is used to help treat the symptoms of the diseases. Make Connections Health Science Explain that lung cancer is often fatal because there is no easy way to detect it at an early stage before it has spread. New X-ray techniques now allow doctors to detect very small lung tumors, but determining whether they are cancerous requires a lung biopsy. This is a major surgical procedure with potentially serious risks, and it is not undertaken lightly. Ask: If a simple, nonsurgical technique were discovered to detect lung cancer at an early stage, how would this affect treatment of the disease? (Being able to detect lung cancer early would allow doctors to treat the cancer or remove the tumor surgically before cancer cells spread to other parts of the body.) Build Science Skills Designing Experiments Challenge small groups of students to design an experiment to determine the effects of a smoking-education class on teen smoking attitudes and habits. Students should describe the subject content of the class and how teen smoking attitudes and habits would be measured, both before and after the subjects attended the class. Ask groups to share their experimental designs with the class. Figure Smoking can cause respiratory diseases such as chronic bronchitis, emphysema, and lung cancer. The lung on the left is from a smoker. The lung on the right is from a nonsmoker. HISTORY OF SCIENCE Effects on Respiratory System Smoking tobacco brings nicotine and carbon monoxide into the upper respiratory system. These compounds paralyze the cilia. With the cilia out of action, the inhaled particles stick to the walls of the respiratory tract or enter the lungs. Without cilia to sweep it along, smoke-laden mucus becomes trapped along the airways. This explains why smokers often cough. Irritation from the accumulated mucus triggers a cough that helps to clear the airways. Smoking also causes the lining of the respiratory tract to swell, which reduces the air flow to the alveoli. Diseases Caused by Smoking Only 30 percent of male smokers live to age 80, but 55 percent of male nonsmokers live to that age. Clearly, smoking reduces life expectancy. Smoking can cause such respiratory diseases as chronic bronchitis, emphysema, and lung cancer. In chronic bronchitis, the bronchi become swollen and clogged with mucus. Even smoking a moderate number of cigarettes on a regular basis can produce chronic bronchitis. Affected people often find simple activities, such as climbing stairs, difficult. Long-term smoking can also cause a respiratory disease called emphysema (em-fuh-see-muh). Emphysema is the loss of elasticity in the tissues of the lungs. This condition makes breathing very difficult. People who have emphysema cannot get enough oxygen to the body tissues or rid the body of excess carbon dioxide. Smoking is an important, but preventable, cause of lung cancer. Figure shows the effects of smoking on the lungs. Lung cancer is particularly deadly because its cells can spread to other locations. By the time lung cancer is detected, it usually has spread to dozens of other places. About 160,000 people in the United States are diagnosed with lung cancer each year. Few will survive for five years after the diagnosis. 962 Chapter 37 Doll s doctors It is common knowledge today that cigarette smoking is the major cause of lung cancer and a contributing factor to a number of other serious health problems. However, as recently as 1950, doctors were unaware of the health risks of tobacco use. All that changed in the 1950s with the innovative research of Sir Richard Doll. Doll used epidemiological methods to establish a link between cigarette smoking and many serious illnesses, including lung cancer and heart disease. His approach was to follow a large sample of people over many years to establish correlations between suspected risk factors and the development of disease. Ironically, the sample Doll followed to establish the link between smoking and lung cancer was a group of British doctors. Doll later used the same method to study the effects of other risk factors on cancer development, including the effects of asbestos on the development of a certain type of lung cancer.

8 Smoking is also a major cause of heart disease. Smoking constricts, or narrows, the blood vessels. This causes blood pressure to rise and makes the heart work harder. The effects of smoking on the circulatory system can be seen in Figure There is a drastic change in body temperature and in circulation immediately after smoking a cigarette. Smoking doubles the risk of death from heart disease for men between 45 and 65. Moreover, for men and women of all ages, the risk of death from heart disease is greater among smokers than among nonsmokers. Smoking and the Nonsmoker In recent years, evidence has shown that tobacco smoke is damaging to anyone who inhales it, not just the smoker. For this reason, many states have restricted smoking in restaurants and other public places. Passive smoking, or inhaling the smoke of others, is particularly damaging to young children because their lungs are still developing. Studies now indicate that the children of smokers are twice as likely as children of nonsmokers to develop respiratory problems, such as asthma. Dealing With Tobacco Whatever the age of a smoker, and no matter how long that person has smoked, his or her health can be improved by quitting. Nicotine is a powerful drug with strong addictive qualities that make it very difficult to quit smoking. Thus, considering the cost, the medical dangers, and the powerful addiction, the best solution is not to begin smoking. Figure These thermograms provide a colorcoded map of temperature distribution over the body surface (blue = cold; pink = hot). The top thermogram shows the forearm and hand area prior to smoking a cigarette. The bottom thermogram shows the same area after smoking. Interpreting Graphics Do you think circulation is increased or decreased after smoking? Use Community Resources Have interested students contact their local chapter of the American Lung Association to find out about programs available to people who want to quit smoking, such as the Great American Smokeout. Students should request copies of pamphlets, brochures, and other written materials that are available free of charge from the association. Ask students to share these materials with the class. 3 ASSESS Evaluate Understanding Write the following words on the chalkboard: nose, larynx, pharynx, trachea, lung, bronchus, alveolus. Call on students at random to describe the function of each structure. Reteach Work with students to create a simple schematic diagram showing what occurs during the process of gas exchange in the alveoli Section Assessment 1. Key Concept Interpret the function of the respiratory system by stating what it does. 2. Key Concept Describe some of the health problems caused by smoking tobacco. 3. Explain the process of gas exchange in the lungs Section Assessment 4. Describe how breathing is controlled. 5. Critical Thinking Inferring As you have read, the breathing center in the brain responds to the level of carbon dioxide in the blood not the level of oxygen. What consequences does this have for people at high altitudes? Structure and Function Compare what you learned in Units 8 and 9 about respiration in terrestrial arthropods, fish, and flatworms with human respiration. Relate the method of respiration to the type of environment the organism inhabits. What do these methods have in common? How do they differ? Students might note that flatworms, which do not have respiratory organs, use diffusion to transport and excrete materials. Students can compare tracheal tubes and book lungs of terrestrial arthropods with human respiratory structures, or the removal of oxygen from water in gills with the removal of oxygen from air in alveoli. If your class subscribes to the itext, use it to review the Key Concepts in Section It brings about the exchange of oxygen and carbon dioxide between the blood, the air, and tissues. 2. Chronic bronchitis: bronchi become swollen and clogged with mucus; emphysema: loss of elasticity in lungs; lung cancer: deadly disease that spreads to other parts of body 3. Oxygen diffuses from alveoli into the blood across capillary walls, and carbon dioxide diffuses from blood into air in the alveoli. 4. When the level of carbon dioxide rises in the blood, the breathing center sends out nerve impulses that cause the diaphragm to contract and bring air into the lungs. 5. The level of carbon dioxide in their blood is normal, so their breathing center does not increase the rate of breathing. As a result, they do not get enough oxygen. Answer to... Figure Circulation is decreased after smoking. This explains why the hand in the bottom photograph is colder after smoking. Circulatory and Respiratory Systems 963