The lungs

• the lungs are in the thorax

  • the thorax is at the top of your body
  • it's separated by the diaphragm
  • the lungs protect the ribcage, they're surrounded by peural membranes
  • the air you breathe in goes through the trachea, then slits into 2 tubes called bronchi - 1 going into each lung
  • the bronchi splits progressively into smaller tubes called bronchioles
  • the bronchioles finally end at small bags called alveoli where the gas exchange takes place
• Alveoli


  • Carry out gas exchange in the body
  • Millions of sacs in the lungs surrounded by a network of blood capillaries - where gas exchange happens
• Gas exchange in the alveoli


  1. Blood passing the alveoli has just returned to the lungs from the rest of the body, so it contains a lot of CO2 and very little O2

  2. Oxygen diffuses out of the alveolus into the blood

  3. Carbon dioxide diffuses out of the blood into the alveolus to get breathed out
• Oxygen and carbon dioxide transport in the body

  1. Blood then reaches body cells and the oxygen is released from the red blood cells

  2. Carbon dioxide diffuses out of the body cells into the blood, and then it is carried back to the lungs