The lungs

• Lungs are in the thorax

  1. thorax top part
  2. separated form the lower part of the body by the diaphragm
  3. the lungs are sponges and are protected by the ribcage they’re surrounded by the pleural membranes
  4. the air that you breathe in goes through the trachea this splits into two tubes called bronchi one going to each lung
  5. the bronchi split into smaller tubes called bronchioles
  6. end up at bags called alveoli where gas exchange takes place
• Alveoli


  Carry out gas exchange
• Lungs


  • Contain alveoli
  • Surrounded by a network of blood capillaries
  • Where gas exchange happens
• Gas exchange in alveoli


  1. Blood passing next to the alveoli returned to the lungs from the rest of the body so contains lots of CO2 and very little O2

  2. Oxygen diffuses out the alveolus (high concentration) into the blood (low concentration)

  3. CO2 diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out
• Gas exchange in body cells

  1. Oxygen is released from the red blood cells and diffuses into the body cells

  2. Carbon dioxide diffuses out of the body cells into the blood then carried back to the lungs
• Breaths per minute= number of breathes/ number of minutes