The Lungs

 Key Adaptions for gas exchange:

• Presence of surfactant - alveoli are covered with a thin layer of pulmonary surfactant (a protein/lipid liquid that reduces surface tension in alveoli)

This makes it easier for oxygen and carbon dioxide to diffuse in/out of the lungs

• High surface area - many bronchioles, providing a very large surface area for gas exchange, extensive capillary bed surround each fo the alveoli

Increase overall SA and the efficiency of gas exchange

• Diaphragm and intercostal muscles - controls the movement of air by expanding and contracting to create pressure gradients

• Thin respiratory membrane - one cell thick membranes line the alveoli and capillaries enhancing gas exchange

  Ventilation

  Inspiration: pressure in the chest is less than the atmospheric pressure, air will move into the lungs

  Expiration: pressure in the chest is greater than the atmospheric pressure, air will move out of the lungs

  Respiratory muscles function to alter the pressure in the chest

  Antagonistic muscle pairs: when one muscle contracts, the other relaxes

  Inhalation

  Diaphragm - contracts

  External intercostal muscles - contract

  Volume of the lungs - increases

  Pressures of the lungs - decreases

  Air enters the lungs

  Exhalation

  Diaphragm - relaxes

  External intercostal muscles - relaxes

  Volume of the lungs - decreases

  Pressure of the lungs - decreases

  Air leaves the lungs

  During long or forced exhalations, the internal intercostal muscles also contract

  Additional abdominal muscles also contract to push the diaphragm upward

  Measurement of lung volumes

  Techniques for measuring ventilation rate or lung tidal volume:

  • Observation - count number of breaths per second

  • Chest belt and pressure meter - recording rise and fall of the chest

  • Spirometer - records the volume of gas expelled per breath

  Detects the change

   

   

  Ventilation rate: the number of breaths per minutes

  Greater frequency of breaths allows for a more continuous exchange of gases

  Tidal volume: the total volume of air that moves in or out of the lungs with each breath

  Deeper breathes = more gas exchange in the lungs

  Vital capacity: the maximum amount of air you can inhale and exhale in one breath

  Expiratory reserve: extra air you breath in or out after normal inhalation or exhalation

  Total lung capacity: the maximum volume of air your lungs can hold

  Residual volume: the volume of air that remains in your air after exhaling

   

  Effects of exercise on ventilation:

  • Increased ventilation rate

  • Increased tidal volume

  • Over time, consistent training will also increase vital capacity and expiratory reserve