The theory of channels and collaterals is an important component of the theoretical system in traditional Chinese medicine. It covers the physiological functions and pathological changes of the channels and collaterals, their interrelations with the zang-fu organs, and is essential in guiding clinical practice, especially acupuncture treatment.
Energy that flows through the body - breath, food, light, darkness etc. moves and spreads in the body through channels called meridians and smaller channels known as collateral's. The system of channels and collaterals constitutes the twelve main channels (meridians), the eight extra channels, the fifteen collaterals, the twelve divergent channels, the musculo-tendinous and cutaneous regions of the twelve main channels.
There are twelve major meridians that run on each side of the body, one side mirroring the other. Each meridian corresponds to an internal organ. And each organ, with its own physiological and invisible energy functions, is not only dependent on the other organ systems but also on the greater meridian network.
(1) Physiologically, the channels and collaterals are considered to be a series of connecting passages through which qi and blood circulate to regulate the functions of the zang-fu organs, tissues, and sense organs. These passages also conduct the sensations and reactions (deqi) of acupuncture treatment.
The five zang and six fu organs, four limbs, nine orifices, skin muscles, vessels, and tendons, although having their respective physiological functions, also maintain the harmonization and uniqueness of interior, exterior, upper, and lower parts of the body as a united and organic entity. This interconnection and organic combination relies upon the function of the channels and collaterals system.
All the tissues and organs of the human body need the nourishment of qi and blood in order to keep their normal physiological activities. The distribution and circulation of qi and blood throughout the body to nourish the zang-fu, tissues, and organs and to resist exogenous pathological factors depends on the transportation and conduction of the channels and collaterals. The channels and collaterals are the passages through which blood and qi flow to nourish yin and yang, to moisten tendons and bones, and to lubricate the joints.
(2) Pathologically, channels and collaterals are the pathways through which the exogenous pathological factors are transmitted and their channels reflected. When pathogenic factors invade the skin and the pores are open they enter the collaterals. When the collaterals become full, the pathogenic factors will move into the channels. When the channels are full, the pathogenic factors transmit to and reside in the zang and fu organs.
The interior and exterior, upper and lower parts of the body form an integrated entity through the connecting network of channels and collaterals. So under pathological conditions every part of the body will affect the rest via the channels and collaterals. The channels and collaterals are not only the passages of disease transmission, but can also reflect pathological changes. Namely, the diseases of the zang-fu organs can be reflected on the body surface, especially in certain areas or at certain points, through the transmission of channels and collaterals.
(3) In diagnosis, channels and collaterals have certain running courses that connect with the zang-fu organs. They also reflect pathological changes on the body surface. Therefore clinical diagnosis can be made according to symptoms that are related to those courses and their respective zang-fu organs.
(4) In treatment, the theory of channels and collaterals is extensively used in clinical treatment for different branches of traditional Chinese medicine. Treatments using traditional medicinal herbs are based on their main actions vis-a-vis related zang-fu organs and channels. In the practice of acupuncture, the theory of channels and collaterals is the basis of all treatment and clinical practice. Point selection and prescription combinations are all made on this basis. By stimulating a certain point or area on the body surface the physiological functions of the channels and collaterals are aroused. This action is achieved by propagating sensation through the channels. Without this sensation it is hard to achieve a therapeutic effect.