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• Stimulat


  Bacteria and viruses
• Bacteria and viruses


  • Cause cough, bronchitis and pneumonia
• Asbestos


  Asbestos dust is a carcinogenic compound that can cause lung cancer
• Ama


  Haze, dust and pollen
• Haze and dust


  • Produced from motor vehicle exhaust, open burning and forest fires
  • Deposited on the lungs and respiratory tract, causing difficulty in breathing
• Pollen


  • Allergens that cause asthma attacks in asthma patients
• These are tiny solid particles suspended in the air
• The anthers of flowers release pollen into the air which are then carried by wind over long distances
• Emphysema


  A condition in which the alveoli are damaged as a result of exposure to harmful substances
• Emphysema


  • The alveolus loses elasticity and expands
  • The cell wall of the alveolus is damaged
  • The surface area of the alveolus becomes smaller
  • Gas exchange through the alveolar wall becomes less efficient
  • The damage to the alveoli is permanent and the ability to breathe cannot be restored
• Lung cancer


  Cancer cells can spread to other organs in the body
• Bronchitis


  Inflammation of the bronchiole tubes
• Smoking


  • Harmful to the respiratory system
  • Cigarette smoke contains thousands of toxic chemicals that can damage the tissues of the lungs
  • Increases the risk of lung diseases, pneumonia and inflammation of the throat compared to a non-smoker
  • Passive smoking is also harmful but less so than active smoking
• Smoking is the leading cause of lung cancer
• Smoking damages the ability of the respiratory system in carrying out its functions
• Cigarette smoke contains tar, a brown-red substance, heat and acidic gases that damage the lungs
• Experiment 2.2: To study the effects of smoking on the human respiratory system

  1. Manipulated variable: Presence of cigarette smoke

  2. Responding variable: Colour of cotton wool and litmus solution at the end of the experiment

  3. Constant variable: Rate of suction of air by the air pump
• The thermometer reading and the colour of the cotton wool and litmus solution are recorded
• The air pump is then switched on and the changes in the thermometer reading and the cotton wool colour and litmus solution are observed and recorded
• Alveolar structure


  • Thin walls to allow easy diffusion of gases
  • Moist walls to dissolve respiratory gases before diffusion
  • Dense network of blood capillaries surrounding each alveolus to facilitate rapid transport of respiratory gases
• Haemoglobin


  Transports oxygen in the blood
• Oxygen is transported in the blood in the form of oxyhaemoglobin
• Carbon monoxide competes with oxygen to bind to haemoglobin, forming carboxyhaemoglobin which is a stable compound
• Carbon monoxide causes the heart, brain and body to become starved of oxygen as there is a shortage of haemoglobin in the blood
• Lack of oxygen can cause breathing difficulties, shortness of breath, dizziness, headaches and fatigue
• Cigarette tar


  • A sticky brown substance containing carcinogens which can cause lung cancer
  • Deposits in the lungs and blackens them
  • Damages the lungs by narrowing the bronchioles and destroying the cells in the air passages, including the bronchi and alveoli
  • Increases the production of mucus and phlegm in the lungs