pathway of air

• pathway of air

  1. nose/mouth
  2. trachea
  3. bronci
  4. bronchioles
  5. alveoli
• 1. oxygen that has been breathed in passes through the alveoli and into the red blood cells in the capillaries
  2. in capillaries, oxygen binds with hydrogen to form oxyhaemoglobin and is carried around the body
  3. haemoglobin carries carbon dioxide from the body to the capillaries
  4. the carbon dioxide in the capillaries passes through the alveoli and is breathed out
• • gas exchange happens in the lungs by diffusion
  • carbon dioxide and oxygen move down a concentration gradient from high to low
  • there is a high concentration of oxygen in the alveoli so it diffuses into the blood capillaries where the oxygen concentration is lower