6.7 - Mechanism of breathing

• What's the process in which air is moved in and out of lungs ?

  Ventilation
• What's inspiration ?

  Atmosphere air pressure is greater than in the lungs so air is forced into the lungs
• What's expiration ?

  Pressure in lungs is greater than in the atmosphere so air is forced out
• Why is ventilation important ?

  Maintains steep diffusion gradients across the alveolar epithelium
• What does contraction of the internal intercostal muscles lead to ?

  Expiration
• What does the contraction of the external intercostal muscles lead to ?

  Inspiration
• 5 steps of inspiration ?

  External intercostals contract and internals relax, ribs pulled up and out increasing volume of thorax, diaphragm contracts so it flattens, increased thorax volume reduces pressure in lungs, atmospheric pressure greater than pulmonary so air is forced into lungs
• 5 steps of expiration ?

  Internal intercostals contract and externals relax, ribs pulled down and in decreasing volume of thorax, diaphragm relaxes so pushed up into dome, decreased thoracic volume increases pulmonary pressure, pulmonary pressure greater than atmospheric so air is forced out of lungs
• What substance does ventilation require for muscle contraction ?

  ATP
• What 2 gradients does oxygen move down during ventilation ?

  Diffusion and pressure