functions

• nose


  humidifies and warms the air as it passes over membranes

  air enters through the mouth and nose
• nasal cavity


  Filters, warms and moistens air before entering lungs

  Acts as resonating chamber for speech sounds
• pharynx


  Air travels through before being diverted into trachea
• epiglottis


  Covers oesophagus during inhalation which diverts air into trachea

  Covers larynx when swallowing preventing food from entering
• larynx


  Contains the vocal cords which are mucous membranes that vibrate as air passes over them
• trachea


  Carries the air into and out of the lungs

  Epithelial lining produces mucus which traps dust and debris

  Cilia beats to move mucus and trapped particles upwards
• bronchioles


  control the flow of air in the lungs

  Expand when body needs more oxygen
• visceral pleura


  covers the surface of the lungs
• parietal pleura 


  lines the inside of the chest
• pleural fluid


  Holds lungs against the inside of the chest wall

  Allows lungs to slide along chest wall when breathing

  reduces friction between chest wall and lungs
• alveoli


  Where gas exchange occurs

  Gases move between the blood in capillaries and air in alveoli

  Allows a net flow of oxygen to pass from airways to blood and carbon dioxide to pass from blood to airways