The kidney is considered a water element. It regulates water metabolism & reception of qi. Fluid that nourishes & moistens the body is known as kidney yin. When the kidney receives fluid the qi of kidney yang divides it into to two types, clear & turbid. Clear fluid is sent upward through San Jiao to moisten the lung where it is distributed to the body, while turbid fluid is sent downward for expulsion by the bladder. While the lung qi controls respiration, kidney qi coordinates inhalation.