The Meridians are aligned to the ancient Chinese Five Rhythm system.
Water controls Kidney and Bladder
Wood controls Liver and Gallbladder
Fire controls four: Small Intestine, Triple Warmer, Heart and Circulation Sex (or Peridcardium)
Earth controls Spleen and Stomach
Metal controls Lung and Large Intestine
Working with the elements can assist with working on more than one meridian at a time. For example, working to balance the Water element can help with the kidney and bladder meridians and the organs as well.