Chapter 5: Gas Exchange

• The Gaseous Exchange System

  The Diagram

  
• Ventilation 


  Differences in air pressure caused by breathing

  Intercostal muscles (external and internal) and diaphragm
• Inhalation (Breathing in)


  External intercostal muscles contract

  Internal intercostal muscles relax

  Raise ribs upwards and outwards

  The diaphragm contracts and flattens
• Pressure when inhaling

  The volume inside thorax increases → pressure inside thorax decreases

  Atmospheric pressure > pressure inside thorax

  Air moves into the lungs

  Lungs inflate
• Exhalation (Breathing out)

  External intercostal muscles relax

  Internal intercostal muscle contract

  Lower ribs downwards and inwards

  Muscle in the diaphragm relaxes

  The diaphragm bulges up due to pressure from organs below
• Pressure when exhaling

  The volume inside thorax decreases → pressure inside thorax increases

  The pressure inside thorax > atmospheric pressure

  Air forced out of lungs
• Gas Exchange in Unicellular Oxygen

  Rely on Diffusion alone
• Diffusion definition

  Net movement of molecules or ions, from a place with a higher concentration to a place with a lower concentration down a concentration gradient as a result of random movement
• Gas Exchange in larger organisms

  Require a Gas exchange system

  Gas exchange takes place in alveoli
• How does Gas Exchange happen

  When air is inhaled close inhalationThe action of breathing in., oxygen diffuses from the alveoli into the blood to be used for respiration by the body's cells.