Biology - Respiration

• Respiratory System

  1. Intake of oxygen

  2. Removal of carbon dioxide

  3. Gas exchange
• Respiratory System pathway


  • nose
  • throat
  • larynx
  • windpipe
  • bronchi
  • bronchioles
  • alveoli
• Specialised cells in respiratory system


  • Goblet cell (produces mucus)
  • Ciliated epithelial cell (waft mucus towards throat)
• Antagonistic Muscles


  Muscles that work as a pair
• Ventilation


  Movement of air in and out of the lungs
• Inhalation

  1. External intercostal muscles contract

  2. Ribcage moves upwards and outwards

  3. Diaphragm contracts and flattens

  4. Volume of thoracic cavity increases

  5. Air pressure decreases

  6. Air rushes/moves into lungs
• Exhalation

  1. External intercostal muscles relax

  2. Ribcage moves downwards and inwards

  3. Diaphragm relaxes and curves

  4. Volume of thoracic cavity decreases

  5. Air pressure increases

  6. Air rushes/moves out of lungs
• Gas Exchange


  • Movement of gases in and out of blood
  • Gases involved: carbon dioxide, oxygen
• One lung has 300 million alveoli
• Characteristics of Alveoli


  • Thin wall (one cell thick for shorter diffusion distance)
  • Moist inner surface to dissolve gases before diffusion
  • Surrounded by capillaries
• Composition of inhaled and exhaled air

  • Oxygen - inhaled 21%, exhaled 16%
  • Carbon dioxide - inhaled 0.04%, exhaled 4%
  • Nitrogen - inhaled 78%, exhaled 78%
  • Water vapour - normal, more
• Lung Diseases


  • Asthma
  • Emphysema
  • Smoker's Cough
  • Lung Cancer
  • Carbon Monoxide poisoning
• Asthma


  • Muscles in airway tightens, narrowing it
  • Difficulty in breathing
  • Caused by dust particles
  • Treatment - inhaler
• Emphysema


  • Walls of alveoli are damaged reducing surface area for gas exchange
  • Caused by smoking
  • No treatment
• Smoker's Cough


  • Cilia is paralysed (stops functioning)
  • Unable to sweep mucus out of airway
  • Cough to expel mucus
• Lung Cancer


  Abnormal growth of cell in lungs caused by tobacco
• Carbon Monoxide poisoning

  • Haemoglobin in red blood cells bind with carbon monoxide instead of oxygen
  • Caused by burning fossil fuels, heaters, vehicles