Exchanging substances

• where does gas exchange happen

  lungs
• what is the job of the lungs

  transfer oxygen to the blood and remove waste co2 from it
• what is alveoli 


  millions of little air sacs in the lungs
• what is alveoli specialised to do

  maximise the diffusion of 02 and CO2
• adaptations of alveoli

  enormous surface area, moist lining, thin walls , good blood supply
• what does villi do 


  provide really big surface area so digested food is absorbed quickly into the blood
• what does villi have

  single layer of surface cells, very good blood supply to assist quick absorption