Gas exchange$

• Gas exchange


  1. O2 moves from the lungs to the bloodstream

  2. CO2 (a waste gas) moves from the blood to the lungs
• Gas exchange is essential to life
• Purpose of the respiratory system

  To perform gas exchange
• Pulmonary ventilation


  Provides air to the alveoli for gas exchange process
• Gas exchange at respiratory membrane

  1. Oxygen enters bloodstream

  2. Carbon dioxide exits
• Blood is oxygenated and carbon dioxide, the waste product of cellular respiration, is removed from the body through gas exchange
• Gas laws


  Help understand gas exchange
• Force


  Exerted from gas molecules on the surface they are based in, force is pressure in this situation
• In most scenarios, gas molecules are present in a mixture with many other molecules
• Partial pressure (Px)


  The pressure of a single gas in a mixture of gases
• Dalton's law states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the gases in the mixture
• Gas exchange


  • Ventilation (air moving in and out of lungs)
  • Perfusion (flow of blood in pulmonary capillaries)
• For efficient gas exchange, ventilation and perfusion must have a compatible volume
• Factors like regional gravity effects, blocked alveolar ducts, or disease


  Can cause ventilation and perfusion to be imbalanced
• Sufficient ventilation


  Partial pressure of O2 remains high in alveoli
• Lacking ventilation in lungs


  Partial pressure of O2 slowly drops in alveoli
• Greater partial pressure of CO2 in alveoli

  Bronchioles increase diameter
• Decreased level of O2 in blood supply

  Bronchioles increase diameter, allowing CO2 to be exhaled at greater rate
• Greater partial pressure of O2 in alveoli

  Pulmonary arterioles dilate, increasing blood flow
• External respiration


  Gas exchange in alveoli, exchange of gases in external environment
• Internal respiration


  Gas exchange at body tissues, exchange of gases in internal environment
• Processes involved in gas exchange


  • Ventilation
  • Inspiration
  • Expiration
  • Perfusion
  • Diffusion
• The respiratory membrane is highly permeable to gases, the respiratory and blood capillary membranes are very thin, and there is a large surface area throughout the lungs to maximise diffusion of gases
• Primary function of respiratory system

  Take in oxygen, release CO2
• Gas exchange between alveolar spaces and capillaries


  1. Oxygen moves from alveoli to blood

  2. Carbon dioxide moves from blood to alveoli
• Bronchioles


  Tiny branch of air tubes in the lungs