Gas Exchange at the Alveoli

• • Oxygen enters the blood from the air
• • Carbon dioxide leaves the blood and enters the air
• What does the term gas exchange refer to?

  the exchange of gases between the air and the blood; this occurs in the alveoli of the lungs
• Gas exchange occurs by the process of diffusion:

  The movement of particles from an area of high concentration to an area of low concentration
• After diffusing into the blood oxygen binds to haemoglobin within red blood cells to form oxyhaemoglobin:

  oxygen + haemoglobin → oxyhaemoglobin
• • Haemoglobin can also bind to carbon dioxide, aiding the transport of carbon dioxide to the lungs