Human Respiratory System Chapter 10 PDF

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Ten Human respiratory system LY Intro...

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Ten Human respiratory system LY Introduction In Standard Six, you learnt about the concept of air, characteristics of gases that compose air and uses of air in daily life. In this chapter, you N will learn the concept of the respiratory system and the parts of the human respiratory system. You will also learn how breathing takes O place and the disorders of the respiratory system. The competencies developed will help you to maintain body health and avoid behaviour that may affect the respiratory system. SE The concept of the respiratory system U Think E Reason for a human being to die if breathing stops N LI Organisms need air to survive. The air is obtained from their environment. The system which enables the body to take in air to produce energy is N called the respiratory system. This system also allows carbon dioxide gas, which is produced in the process of respiration, to be removed from O the body. R Breathing is the action of taking air in and out of the lungs. The air which enters the human body is a mixture of different gases. See the Table FO below. The air that enters the lungs contains a high amount of oxygen gas while the air that comes out contains a high amount of carbon dioxide gas. 127 SCIENCE AND TECHNOLOGY STD 7.indd 127 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Table: Composition of the air that enters and leaves the body Gas Proportion in the air Proportion in the air entering the lungs leaving the lungs Nitrogen 78% 78% Oxygen 21% 16.46% Carbon dioxide 0.03% 4.47% Other gases 0.97% 0.97% LY Oxygen gas is used to burn food in the body to release energy. The process of burning food produces carbon dioxide gas. This gas must be removed N from the body because, if it remains, it may become toxic and affect the O health of the person. Parts of the respiratory system and their functions SE The respiratory system is comprised of different parts, namely the nose, pharynx, trachea, bronchi and lungs, as shown in Figure 1. U E Nose N Pharynx LI Trachea Lung N Bronchi O Alveolus Ribs R FO Figure 1: Human respiratory system 128 SCIENCE AND TECHNOLOGY STD 7.indd 128 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Nose The nose receives and passes air that enters and leaves the lungs. The nose contains hair and mucus which prevent dusts and microorganisms from entering the lungs. The mucus in the nose adds moisture to the air to prevent dryness of the air passages. In addition, the nose warms air to match with the body temperature. It is advised to breathe using the nose rather than the mouth. This is because the mouth, unlike the nose, does not have hairs to prevent dusts and microorganisms from entering the lungs. LY Pharynx Once air passes through the nose, it enters the pharynx. The pharynx receives air from the nose and passes it to the trachea. The pharynx is N made up of strong muscles which allow air to pass without obstruction. These muscles enable the pharynx to be open to allow air to pass freely. O Trachea The trachea is a long tube which runs from the end of the pharynx to the SE lungs. At its end, it branches into two parts, namely the right bronchus and left bronchus. The right bronchus enters the right lung, while the left bronchus enters the left lung. The trachea receives air from the pharynx and U passes it to the lungs through the bronchi. The bronchi have mucus which traps microorganisms and dust, preventing them from entering the lungs. Lungs E The lungs are located inside the chest cavity. Human beings have two lungs: one on the left side and the other on the right side. The major function of the N lungs is to allow oxygen gas to enter the blood cells. Blood carries this gas LI to the body cells for respiration to release energy. The lungs also receive carbon dioxide gas from the blood and pass it out of the body through N breathing. This gas is produced by the body cells during the production of energy. Both lungs operate at the same time. O Alveoli These are small air sacs in the lungs R where gaseous exchange occurs. Blood capillaries Alveoli are very small but numerous FO in number. These features increase the surface area for the efficiency of gaseous exchange in the lungs. Figure 2: An alveolus 129 SCIENCE AND TECHNOLOGY STD 7.indd 129 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Alveoli have thin membranes, networks of blood capillaries, and a moist surface to allow the diffusion of oxygen gas in and carbon dioxide gas out of the blood stream. See Figure 2. The importance of breathing Human beings require oxygen gas for proper functioning of their body cells. Oxygen gas is used to burn food to release energy for body use. Breathing also helps to remove carbon dioxide gas from the body. This LY gas, if not removed, becomes toxic to the body. All these processes are done through the respiratory system. Breathing in humans also helps in producing sounds. When air passes through the larynx or the voice box, it N creates vibrations which produce sounds as in talking or singing. O Exercise 1 Answer the following questions: 1. Name the parts labelled A-D SE U A E B N C LI D N O R 2. Describe the functions of any four parts of the respiratory system. 3. Explain the importance of alveoli in breathing. FO 4. Why is it advised to breathe using the nose instead of the mouth? 130 SCIENCE AND TECHNOLOGY STD 7.indd 130 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE How breathing occurs The process of breathing occurs in two stages. The first stage is taking air in (inhalation) and out (exhalation) of the lungs. The second stage is gaseous exchange in the lungs. Taking air in and out of the lungs: During breathing, different changes take place in the lungs, chest, and the diaphragm. The diaphragm is a sheet of muscles that separates the chest from the stomach, and it plays LY a major role during breathing. Taking air into the lungs (inhalation): When a person inhales, the diaphragm moves downward. Then, the muscles between the ribs contract, N causing the ribs to go up. These actions increase the space in the chest to allow the lungs to expand. When the lungs expand, the air from outside is O drawn in to fill the empty space in the lungs as shown in Figure 3. SE U Lung E N Ribs LI N O Diaphragm Figure 3: Inhalation R Taking air out of the lungs (exhalation): When a person exhales, the FO diaphragm moves up, the ribs move down and the muscles between the ribs relax. This reduces space in the chest; thus, the air is pushed out through the bronchi, trachea, pharynx and the nose as shown in Figure 131 SCIENCE AND TECHNOLOGY STD 7.indd 131 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE 4. The air removed from the lungs contains a higher amount of carbon dioxide gas than that which enters the lungs. Lung LY Ribs N O Diaphragm SE Figure 4: Exhalation Experiment: To investigate how breathing occurs U Aim: To identify changes that occur in the lungs, diaphragm, and ribs during breathing E Materials: two balloons, three tubes (one should be large and the other should be small), plastic bottle (five litre or more) N with its cap, a wide rubber sheet or plastic bag, pair of scissors, and rope or rubber band LI Procedure 1. Connect three tubes to form a Y-shaped structure. N 2. Tie the two balloons to the small tubes that make the Y-shaped structure. O 3. Cut and remove the base of the plastic bottle and make a hole at the centre of the stopper. R 4. Take the tubes connected with balloons in Stage 2 above and pass it through the open base of the plastic bottle to the hole on the stopper. FO Then, tight the stopper to make sure no air is allowed to pass. 5. Cover the open base of the bottle using a tube or a plastic bag with a wide diameter. Then, tie it using the rope or rubber band as shown in Figure 5. 132 SCIENCE AND TECHNOLOGY STD 7.indd 132 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE 6. Pull the tube or plastic bag with a wide diameter at the base of the bottle downward and observe what happens. 7. Push the tube or plastic bag with a wide diameter at the base of the bottle inward. Then, observe what happens. LY N O SE Figure 5: A model demonstrating how breathing occurs Results U What happened to the balloons when (a) the wide rubber sheet was pulled downward? (b) the wide rubber sheet was pushed inward? E Conclusion N Compare the functions of the parts of the respiratory system of the model LI with the parts of the human respiratory system. N Factors causing changes in the rate of breathing O Various factors change the rate of breathing. Some of these factors are shown below: R Physical exercise or manual activities: When you perform physical exercise or do manual activities, more energy is required by the body. The FO rate of breathing increases to allow more oxygen gas to enter the body to burn food. A high amount of carbon dioxide gas is also produced as a result of physical and manual activities. This gas must be removed from the lungs to prevent it from harming the body. 133 SCIENCE AND TECHNOLOGY STD 7.indd 133 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Fear or anger: The rate of breathing increases when someone is afraid or angry because more energy is required to enable fighting or running. Anaemia: When a person is anaemic, the rate of breathing increases so as to increase the amount of oxygen gas required by the body using the little amount of the blood available. Age: The rate of breathing is proportional to the age of the person. A child breathes faster than an adult. The rate of breathing in an adult is between 12 and 18 times per minute, while that of a child is between 22 and 60 LY times per minute. Altitude: The rate of breathing increases as one moves from low to high N altitudes above sea level. This is because, at higher altitudes, air contains a little amount of oxygen gas. Thus, the rate of breathing increases so O as to get enough oxygen gas. At lower altitudes, air contains a higher amount of oxygen gas, and the rate of breathing is normal. SE Temperature: The rate of breathing depends on environmental temperature. As the temperature increases, the rate of breathing increases. This enables the body to get more oxygen gas used to release U energy for regulating body temperature to normal. Differences between the inhaled and exhaled air Several differences exist between the inhaled and exhaled air. The air E that enters the lungs has similar composition as that of the atmosphere. It contains a high amount of oxygen gas and a low amount of carbon dioxide N gas. The air that leaves the lungs contains a high amount of carbon dioxide gas and a low amount of oxygen gas. In addition, the air that enters the LI lungs is less moist than that which leaves them. N Gaseous exchange in the lungs Gaseous exchange is the action which enables the blood to get oxygen O gas and remove carbon dioxide gas produced by body cells as shown in Figure 6. Gaseous exchange occurs in the alveoli, which are found in the R lungs. Alveoli are surrounded by numerous blood capillaries. They have thin membranes which enable oxygen gas to easily enter the blood by FO diffusion. Diffusion also enables carbon dioxide gas from blood capillaries to enter the lungs so as to be removed from the body. The oxygen gas that enters the blood is carried by arteries to the body cells to produce the energy needed by the body. 134 SCIENCE AND TECHNOLOGY STD 7.indd 134 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Alveoli Capillaries Carbon dioxide leaving blood Oxygen taken in LY blood Red blood cells Figure 6: Gaseous exchange across the alveolus N Disorders of the respiratory system O Disorders of the respiratory system include all conditions that prevent it from working properly. The respiratory system can be affected by lifestyle, disorders or diseases. Asthma and lung cancer are among the disorders of the respiratory system. Asthma SE U Asthma is a condition which causes airways to narrow, swell and produce extra mucus. This makes breathing difficult. It also causes ribs contraction and chest pain. Smoking cigarettes, smoke, perfumes, dust, and pollen are behaviours and substances that can stimulate asthma. These are E allergic substances which initiate asthma. Asthma can also be inherited N from parents. Parents with asthma are likely to pass this condition to their children. LI Symptoms of asthma (a) Difficulty in breathing accompanied by wheezing or hissing sound N when breathing (b) Chest pressure and chest pain O (c) Shortness of breath (d) Excessive coughing especially at night and in the morning R Prevention of asthma Asthma is a chronic disease which has no cure, but there are different FO ways which can be used to help the patient. These ways are as follows: (a) Avoid asthma triggers or allergic substances such as pollen and perfumes, and (b) Take medication as soon as you detect early symptoms. 135 SCIENCE AND TECHNOLOGY STD 7.indd 135 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Lung cancer Lung cancer is caused by abnormal production and growth of lung cells which form swelling in the lung. Lung cancer is caused by inhaling hazardous chemicals or radiations such as air from industries and mines. Smoking or sitting near people who smoke can result in lung cancer. Lung cancer can also be inherited from parents. This happens when one or both parents are affected by lung cancer and receive long-term treatment using radiation or chemicals. These radiations and chemicals affect their genes. Thus, the affected genes can be inherited by their children. LY Symptoms of lung cancer N Lung cancer affects the respiratory system. The following are the symptoms of lung cancer: O (a) persistent coughing, (b) chest pain during breathing or coughing, (c) cough accompanied by blood, (d) breathing difficulty, and (e) heavy and scratching voice. SE U Prevention of lung cancer The best way to avoid lung cancer is to avoid substances causing it. These include to stop smoking and to build residential houses away from industrial E or uranium mining areas. Lung cancer treatment depends on the extent to which the lungs have been affected. A lung cancer victim can be treated N using surgery or radiations. If lung cancer spreads to large areas of the lung, both treatments can be used. LI N Exercise 2 Answer all questions in sections A, B and C. O Section A Choose the most correct answer and write its letter in the box provided. R 1. Which of the following is not the function of the respiratory system? (a) Transportation of oxygen gas in the tissues FO (b) Removal of temperature and fluid from the body (c) Gaseous exchange in the body (d) Talking, screaming and singing 136 SCIENCE AND TECHNOLOGY STD 7.indd 136 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE 2. Gaseous exchange takes place in the __________. (a) larynx (b) nose (c) trachea (d) alveoli 3. The hair and mucus found in the nose help __________. (a) in exchange of air (b) to trap microorganisms and dust (c) to transport air to the lungs LY (d) to cool the air that enters the body through the nose 4. When air is removed from the lungs, the muscles in the ribs N __________. (a) relax O (b) expand (c) contract (d) break down SE 5. Breathing takes place in two stages, namely exchanging gases in the lungs and __________. (a) taking in air to and from the blood U (b) Passing it to the larynx (c) taking air to and from the lungs (d) shrinking of the lungs and chest E Section B N 6. Write TRUE for a correct statement and FALSE for an incorrect statement in the space provided. LI (a) A cough accompanied with blood is a symptom of asthma. __________ N (b) Cigarette smoke and industrial chemicals cause lung cancer. __________ O (c) Pollen and perfume odours are among the substances that cause asthma. __________ R (d) Adhering to good health practices and cleanliness is important for respiratory health. __________ FO (e) Using chemicals is safe for the respiratory system. __________ (f) The rate of breathing changes during physical exercise. __________ 137 SCIENCE AND TECHNOLOGY STD 7.indd 137 26/07/2021 12:01  FOR ONLINE USE ONLY DO NOT DUPLICATE Section C 7. Explain three differences between the air that enters the body and the one that leaves it during breathing. 8. By using diagrams, describe how breathing takes place in the body. 9. Explain two disorders of the respiratory system including their causes. 10. Explain the importance of breathing in living things. 11. By using a diagram, explain how gaseous exchange takes place in LY the alveolus. 12. Explain three factors which can change the rate of breathing. N Vocabulary Alveolus very small air sacs in the lungs where gaseous exchange O occurs Anaemia a condition in which a person lacks enough healthy red Diaphragm tissues SE blood cells to carry adequate oxygen gas in the body the sheet of muscles that separates the chest from the U stomach Diffusion the process of passing air from a region of higher concentration to a region of lower concentration E Exhalation the process of taking out air from the lungs Hair a slender thread like an outgrowth in the nose that traps N dusts and microorganisms Inhalation the process taking in air to the lungs LI Larynx a voice box, an organ located at the top of the neck and it is involved in breathing, swallowing and voice production N Mucus a slippery secretion that is moist and traps dusts and O microorganisms Pharynx an opening above the trachea which receives air from the nose and passes it to the trachea R Respiration the process by which the body generates energy from the food FO Trachea a long tube which starts from the end of the pharynx to the lungs 138 SCIENCE AND TECHNOLOGY STD 7.indd 138 26/07/2021 12:01