gaseous exchange

• what is gaseous exchange

  the exchange of oxygen and carbon dioxide by the process of diffusion
• what is diffusion

  the movement of gas from an area of high concentration to an area of low concentration
• what is the difference between the concentrations

  diffusion gradient
• what is PO2

  partial pressure of oxygen
• what is PCO2

  partial pressure of carbon dioxide
• at rest - external respiration

  exchange of gases at the lungs between deoxygenated blood that arrive in the capillaries and the oxygen rich atmospheric air in the alveoli
• what happens to oxygen

  at rest - external respiration

  moves from high pp in alveoli to low pp in capillary blood down the diffusion gradient
• what happens to CO2

  at rest - external respiration

  moves from high pp in capillary blood to low pp in alveoli down the diffusion gradient
• at rest - internal respiration

  exchange of gases at the muscle cells between the oxygenated blood that arrive in the capillaries and the CO2 producing muscle cells between

  Haemoglobin molecules dissociate O2 as they pass the cells
• what happens to O2

  at rest - internal respiration

  moves from high pp in capillary blood to low pp of muscle cell down the diffusion gradient
• what happens to CO2

  at rest - internal respiration

  moves from high pp in muscle cell to low pp in capillary blood down the diffusion gradient
• during exercise - external respiration

  muscle tissues use greater volume of O2 and produce greater volume of CO2

  Deoxygenated blood that returns to the heart has a lower PO2 and higher CO2 than at rest
• what happens to O2

  during exercise - external respiration

  O2 diffusion gradient gets steeper and O2 diffuses from high PO2 into the alveoli to lower PO2 in capillary blood
• what happens to CO2

  during exercise - external respiration

  CO2 diffusion gradient gets steeper and CO2 diffuses from high PCO2 in capillary blood to lower PCO2 in the alveoli
• during exercise - internal respiration

  the more the intense exercise the more muscle tissues demand for oxygen increases

  therefore the more intense the exercise the lower the PO2 and higher the PO2 in muscle tissue
• what happens to O2

  during exercise - internal respiration

  O2 diffusion gradient gets steeper and O2 diffuses from high PO2 into capillary blood to lower PO2 in muscle cells
• what happens to CO2

  during exercise - internal respiration

  CO2 diffusion gradient gets steeper and CO2 diffuses from high PCO2 in muscle cells to lower PCO2 in capillary blood
• what is external respiration

  exchange O2 and CO2 between the lungs and blood
• what is internal respiration

  exchange of O2 and CO2 between blood and muscle cells (tissue)
• why does external respiration occur

  the pp of gases in the alveoli differs from those in the atmosphere

  humidification of inhaled air
• what is partial pressure

  high levels of oxygen in the atmosphere
• factors that influence external respiration

  surface area and structure of the respiratory membrane

  partial pressure gradients

  matching alveolar airflow to pulmonary capillary blood flow