GCSE AQA Biology 3 The Breathing System

GCSE AQA Biology 3 The Breathing System

1. The lungs

   • Are in the thorax - top part of your body
     • Separated from lower part of body (abdomen) by diaphragm
   • Lungs are big, pink sponges - protected by ribcage
   • Air breathed in goes into trachea which splits into 2 tubes called bronchi...
     • ...which are split into smaller tubes called bronchioles which end at alveoli (where gas exchange happens)

2. Ventilation is...

   • ...breathing in
     • 1) Intercostal muscles & diaphragm contract
       • Muscles between ribs pull ribcage & sternum up & out, diaphragm flattens out
       • 2) Thorax volume increases
         • 3) Pressure decreases, drawing air in
   • ...breathing out
     • 1) Intercostal muscles & diaphragm relax
       • Ribcage and sternum drop in & down
       • 2) Thorax volume decreases
         • 3) Pressure increases, forcing air out

3. Artificial ventilators

   • Machines that move air into/out of lungs - help people who can't breathe by themselves
     • In the past, they used to be giant case (iron lung) - air was pumped out of case so pressure dropped, lungs expanded & air was drawn in
       • Air pumped in had opposite effect, air was forced out of lungs
         • Could interfere with blood flow to lower body
     • Nowadays, ventilators work by pumping air into lungs - expands ribcage, when they stop pumping ribcage relaxes, pushing air out
       • Don't interfere with blood flow but can cause damage (e.g. burst alveoli)