When speaking of yin and yang of every organ, the function is yang, the substance yin. When speaking of yin and yang of the channels and collaterals, the channels may be divided into channels belonging to yin and channels belonging to yang. Collaterals can also be classified as yin collaterals and yang collaterals. When speaking of yin and yang of the twelve channels, three are yang channels of the hand and three yin channel of the hand, three yang channels of the foot and three yin channels of the foot. Yin and yang are always in the state of dynamic balance.
Physiological function is based on substance.
Without substance, including the essence of life, blood, constructive energy and body fluid, there would be no source for functions. But the metabolism of substance must depend on the performance of function. If yin and yang of the human body separate from each other and can not aid each other, life will come to an end. For example, preponderance of yang leads to hyperfunction of the organism and heat manifestations, while preponderance of yin hypofunction of the organism or endogenous cold. Deficiency of yang brings on symptoms of external cold, while deficiency of yin as the result of exhausted vital essence leads to endogenous heat.