human gas exchange system

• Breathing


  The movement of air into and out of the lungs
• Respiration


  The chemical reaction that happens in every cell to release energy in form of ATP
• Ventilation


  The scientific term for breathing
• Gaseous exchange/Gas exchange


  The diffusion of oxygen from the air in the alveoli into the blood and carbon dioxide in the other direction
• Key organs in the gas exchange system

  • Lungs
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
• Ventilation


  1. External intercostal muscles contract

  2. Internal intercostal muscles relax

  3. Diaphragm contracts

  4. Causes decrease in lung pressure

  5. Air flows into lungs
• Expiration/Exhalation


  1. External intercostal muscles relax

  2. Internal intercostal muscles contract

  3. Diaphragm relaxes

  4. Causes increase in lung pressure

  5. Air flows out of lungs
• Alveoli


  • Large surface area
  • Short diffusion distance
  • Concentration gradients
• There are about 300 million alveoli in the left and right lungs
• Alveoli are made up of a single layer of thin epithelial cells
• Alveoli are surrounded by a network of capillaries
• Oxygen diffuses from alveoli into blood


  Carbon dioxide diffuses from blood into alveoli