gas exchange

• how does a gas exchange take place in the lungs?

  1. air passes into the lungs through the trachea
  2. rings of cartilage prevent the trachea from collapsing during inhalation
  3. trachea splits into 2 smaller tubes called bronchi
  4. the bronchi divides into many smaller tubes called bronchioles
  5. they end in tiny air sacs called alveoli
• what are alveolis?


  where gases diffuse in and out of the bloodstream
• how are alveolis adapted to gas exchange?

  • O2 in the air diffuses into the bloodstream/ CO2 diffuses out of the bloodstream back into the air
  • millions of alveoli means that lungs have a large SA
  • has very thin walls so shorter diffusion pathway
  • has a good blood supply
  • once O2 diffuses into blood it is rapidly removed ensuring the conc gradient is as steep as possible
• does breathing increase the rate of diffusion?

  yes
• how does breathing increase the rate of diffusion?

  • brings fresh O2 into the alveoli and takes away CO2
  • increases the conc gradient that increases rate of diffusion