Humans

• The intercostal muscles and diaphragm are responsible for changing the pressure in the thorax, allowing the lungs to move
• Alveoli are adapted for gas exchange by the large surface area, good blood supply, and short diffusion distance for oxygen
• Tar in cigarettes damages cilia, meaning mucus and phlegm build up in the trachea
• Carbon monoxide reduces the amount of oxygen red blood cells can carry, increasing blood pressure and increasing risk of coronary heart disease
• What is the primary function of the lungs in the thorax?

  To get oxygen into the bloodstream and remove carbon dioxide
• How is the thorax separated from the lower part of the body?

  By a muscle called the diaphragm
• What surrounds the lungs?

  The pleural membranes
• What protects the lungs?

  The ribcage
• Where do the intercostal muscles run?


  Between the ribs
• What is the pathway of air when you breathe in?

  It goes through the trachea, which splits into bronchi
• What do the bronchi split into?

  Progressively smaller tubes called bronchioles
• Where does gas exchange take place in the lungs?

  In the alveoli
• What happens to your breathing rate when you exercise?

  • Breathing rate increases
  • Muscles require more oxygen
  • More carbon dioxide is produced
• How can you investigate the effect of exercise on breathing rate?

  1. Sit still for five minutes
  2. Count breaths for one minute
  3. Exercise for four minutes
  4. Count breaths for one minute after exercise
  5. Repeat and calculate mean results
• Why does exercise increase breathing rate?

  Because muscles respire more and need more oxygen
• What variables should be controlled during the breathing rate experiment?

  • Time spent exercising (using a stopwatch)
  • Temperature of the room (using air conditioning or thermometer)
• How can you investigate the release of carbon dioxide in your breath?

  1. Use limewater to test for CO2
  2. Breathe into two boiling tubes with limewater
  3. Observe color change in boiling tube B
• What happens to limewater in the presence of carbon dioxide?

  It turns cloudy
• What does the clear limewater in boiling tube A indicate?

  That the air drawn in contains very little carbon dioxide
• What does the cloudy limewater in boiling tube B indicate?

  That carbon dioxide was produced during respiration
• What is the significance of the experiment with limewater?

  • Demonstrates that CO2 is released when we breathe
  • Confirms that exhaled air contains CO2 from respiration