form 3 science , Chapter 1

Science Form 3

Unit 1 Respiration

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Unit 1 Respiration 1.1 Human Breathing Mechanism 1.2 Transport of Oxygen in the Human Body 1.3 The Importance of a Healthy Respiratory System

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1.1

HUMAN BREATHING MECHANISM yschow@smkbpj(a)

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A. Human Respiratory System 1. Living organisms must be able to take oxygen from the air and get rid of carbon dioxide to the air. 2. Gas exchange takes place through a gas exchange surface, also known as a respiratory surface. 3. Breathing is also known as external respiration. yschow@smkbpj(a)

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4. Breathing consists of two stages: a. Inhalation - during which air is taken into the lungs. b. Exhalation - during which air passes out of the lungs. 5. The breathing system or the human respiratory system consists of the following structures or organs: a. The nasal cavity b. Trachea c. Bronchus (plural: bronchi) d. Bronchiole

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e. Lungs i. Alveolus (plural: alveoli) f. Rib cage g. Diaphragm h. The intercostal muscles i. Internal intercostal muscles, ii. External intercostal muscles.

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6. Flow of air into the lungs a. Air is breathed in through the nose and enters the nostrils. b. The nostril leads to the nasal cavity where the air is warmed up and moistened. i. Hairs and sticky mucus trap particles inside the nasal cavity. c. The air then enters the trachea. yschow@smkbpj(a)

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d. The trachea branches into two bronchi. i. Each bronchus leads directly into a lung. ii. The bronchus branches into many smaller tubes called bronchioles

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e. The air then passes through the bronchiole and comes to alveoli i. The human lungs have millions of alveoli ii. The wall of the alveolus is only one-cell thick. iii. It is thin , moist and is surrounded by a network of capillaries. iv. The exchange of respiratory gases, oxygen and carbon dioxide, occurs between the alveolus and capillaries.

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C. The Breathing Mechanism 1. The breathing mechanism is the physical changes which occur in the respiratory system during breathing. 2. This mechanism involves a. inhalation (breathing in), b. exhalation (breathing out). yschow@smkbpj(a)

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3. During inhalation a. Both the intercostal muscles and the diaphragm contract. b. The diaphragm moves downwards , increasing the volume of the thoracic (chest) cavity. c. The intercostal muscles pull the ribs up , expanding the rib cage and further increasing the volume of the thoracic cavity. d. These actions lower the air pressure in the alveoli. e. Air from the outside then rushes in through the nasal cavities, trachea and lungs. The lungs yschow@smkbpj(a) expand.

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4. During exhalation a. the intercostal muscles relax causing the rib cage to move downwards and inwards. b. the muscles of the diaphragm relax and the diaphragm curves upwards and returns to its original dome shape. c. These actions return the thoracic cavity to its original volume. d. The air pressure inside the lungs is now higher than the atmospheric pressure outside. e. The lungs contract and the air is forced out through the respiratory tract. yschow@smkbpj(a)

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A model representing how diaphragm works in the human respiratory system. i.

The bell jar represents the thoracic cavity. ii. The glass rod represents the trachea. iii. The balloons lungs. represent the lungs iv. The rubber sheet represents the diaphragm. yschow@smkbpj(a)

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When the rubber sheet is pulled downwards: i. The volume of the bell jar increases. ii. The air pressure inside becomes lower than the atmospheric pressure outside. iii. This condition allows the air outside to enter the glass tube, causing the balloons to expand. iv. This action represents the process of inhalation. yschow@smkbpj(a)

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When the rubber sheet is pushed upwards: i.

The volume of the bell jar decreases.

ii. The air pressure inside the bell jar becomes higher than the atmospheric pressure outside. iii. The air inside the balloons is forced out through the glass tube. This causes the balloons to deflate. iv. This action represents the process of exhalation. yschow@smkbpj(a)

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Composition of inhaled air and exhaled air:

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0.03

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78

78

less

more

Variable

37 oC yschow@smkbpj(a)

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Comparison between inhalation and exhalation:

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1.2

TRANSPORT OF OXYGEN IN THE HUMAN BODY yschow@smkbpj(a)

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A. Diffusion of Oxygen from the Alveolus to the capillaries

1. Diffusion is the movement of molecules from a region where they are highly concentrated to a region where they are less concentrated.

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2. The following characteristics enable oxygen to diffuse through the walls of the alveoli easily and efficiently. a. The alveoli have very large surface areas and thin walls (only one-cell thick). b. The inner surfaces of the alveoli are always moist. c. The outer surfaces of the alveoli are surrounded by a network of blood capillaries. These capillaries also have very thin walls (only one-cell thick). yschow@smkbpj(a)

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3. Inhaled air is rich in oxygen. 4. The oxygen concentration in the alveolus is therefore higher than the oxygen concentration in the deoxygenated blood in the capillaries. 5. The difference in oxygen concentration makes the oxygen diffuse easily into the blood capillaries. a. Oxygen in the alveolus diffuses through the wall into the blood. b. Carbon dioxide and water vapour diffuse from the blood into the alveolus. yschow@smkbpj(a)

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B. Oxygen Transport 1. Through the breathing process, oxygen from the air flows into our bloodstream. 2. The heart then pumps the oxygenated blood to supply oxygen to the body cells. a. Body cells need oxygen for cell respiration. b. Cell respiration is the oxidation of food to release energy.

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3. Heamoglobin a. It is the special carrier and it transports oxygen from the lungs to all parts of the body. b. b. Haemoglobin is a blood pigment. c. It contains haem (or heme) (the part which is made up of ferum ) and globin (the protein part). d. As the oxygen concentration is high in the alveolus, oxygen diffuses into the capillaries. yschow@smkbpj(a)

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e. Oxygen then combines with haemoglobin in the red blood cells and forms oxyhaemoglobin. f. Blood with oxyhaemoglobin is bright red in colour. g. It is carried to the heart to be distributed to all the cells of the body.

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C. Diffusion of Oxygen from the Capillaries to the Body cells. 1. Oxygenated blood is sent to all the cells in the body by a vast network of blood vessels. a. When blood reaches the body cells, oxyhaemoglobin is broken down into haemoglobin and oxygen. b. The oxygen then diffuses through the walls of the capillaries into the cells. c. Oxygen is then used to oxidise food to release carbon dioxide during cell respiration. yschow@smkbpj(a)

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1.3

THE IMPORTANCE OF A HEALTHY RESPIRATORY SYSTEM yschow@smkbpj(a)

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A. Healthy Respiratory System 1. Our respiratory system is protected by a layer of cilia and glands which secrete mucus. 2. Our lungs are in direct contact with the air we breathe. 3. The pollutants in the air can cause damage to our respiratory system. yschow@smkbpj(a)

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B. Effects of Harmful Substances 1. Nicotine in cigarettes a. Stimulates the production of cells in the trachea and lungs and leads to lung cancer. b. Narrows and hardens the blood vessels. This affects blood flow and causes heart attacks. c. Leads to addiction as nicotine is a drug. yschow@smkbpj(a)

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2. Tar in tobacco a. blackens the lungs. b. The walls of the lungs thicken and this makes respiration difficult. c. Tar is carcinogenic and can cause lung cancer.

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3. Nitrogen dioxide in cigarette smoke and from motor vehicles and industries a. dissolves in the mucus layer on the walls of the trachea and alveolus. b. It forms an acid which can destroy lung tissues. c. In big towns, the reddish-brown layer in the atmosphere is due to the presence of nitrogen dioxide. yschow@smkbpj(a)

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Nitrogen dioxide, NO2, is a brownish-red gas at room temperature. Nitrogen dioxide is a poisonous gas

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4. Sulphur dioxide a. Sulphur dioxide is acidic. b. It is released when fuels which contain sulphur are burnt. c. Cigarette smoke and smoke from factories have a high sulphur dioxide content. d. Sulphur dioxide is very soluble in the alveoli. It forms an acid which destroys the lungs. yschow@smkbpj(a)

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5. Carbon monoxide a. Carbon monoxide is a toxic gas which is produced when organic fuels are burnt. b. Most of the carbon monoxide in the atmosphere comes from vehicles and factories which use charcoal, petrol and diesel as fuel. c. Carbon monoxide combines with haemoglobin inthe red blood cells and prevents oxygen from combining with haemoglobin. d. Our cells become deprived of oxygen and this results in death. yschow@smkbpj(a)

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6. Dust and dirt a. Dust and dirt are released to the atmosphere by factories and motor vehicles. b. The presence of dust and dirt in our lungs hinders the exchange of gases.

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C. Diseases of the Respiratory System 1.

Asthma

a.

The primary cause of asthma is due to airborne irritants such as pollutants and dust.

b. It may also caused by genetic factors and food allergy . c. Asthma is a condition in which the tubes of the lungs become inflamed. d. This is because the air tubes are narrower and partially blocked. e. More and thicker mucus is secreted into the tubes. yschow@smkbpj(a)

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2. Influenza a. This disease is caused b. by viruses which attack the mucus membranes in the respiratory system. b. The influenza virus spreads through tiny droplets in the air. Blocked noses, teary eyes, giddiness, headaches, aches in the limbs, coughs and fever are some of the symptoms of the disease. yschow@smkbpj(a)

Sneeze

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3. Pneumonia a. Pneumonia is caused by bacteria, viruses and chemical substances in polluted air. b. The trachea and alveolus are attacked by bacteria or viruses. The lungs are filled with pus and fluid and the patient will suffer from chest pains, fever and coughs. yschow@smkbpj(a)

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4. Tuberculosis (TB) a. This disease is caused by bacterial infection (Mycobacterium tuberculosis) which are carried by water droplets and dust in the air. b. Infection occurs when the water droplets and dust are inhaled by other people. c. The patient suffers prolonged coughs and spits out blood in the end stages. yschow@smkbpj(a)

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5. Bronchitis a. Bronchitis is caused by viral infections. b. Bronchitis makes a person cough and produce a lot of mucus. c. The bronchus becomes swollen and the patient feels pain in the chest. feels pain in the chest. d. Bronchitis causes colds and phlegm. e. This disease makes respiration and gaseous exchange difficult. Patients who smoke find it hard to recover. yschow@smkbpj(a)

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6. Emphysema a. This disease is linked to smokers and people who work in dusty areas such as in mines and quarries. b. The alveoli expand and burst. c. The lungs become less elastic. d. The thickened layer of scar prevents oxygen from diffusing into the blood. As a result the patient experiences breathing difficulties. yschow@smkbpj(a)

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7. Lung cancer a. Many cancer cases are a result of smoking cigarettes. b. Air polluted with carcinogens from factories and vehicle emissions, dust and asbestos also cause cancer. c. Lung cancer is difficult to cure. d. It is important that we keep away from these pollutants. e. Lung cancer is not contagious and cannot spread from a patient to other people. yschow@smkbpj(a)

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D. Improving Air Quality 1. Pollution is mainly caused by irresponsible human behaviour and improperly planned activities. 2. We must be responsible for preserving and conserving air quality. 3. Air pollution interferes with the respiratory process. It can cause respiratory diseases which can be fatal. yschow@smkbpj(a)

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Chemicals found in cigarette

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HOW CAN YOU IMPROVE AIR QUALITY?

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Walk or cycle instead of using your car.

Use public transport instead of taking the car

Service your vehicle regularly - this can reduce pollution and make it cheaper to run. yschow@smkbpj(a)

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Stop open burning

Opening up the windows to allow indoor air circulation

Don’t Smoke

Car pool

Bring In Some Nature yschow@smkbpj(a)

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