Composition of meridian system
The system of meridians is mainly composed of the twelve regular meridians, twelve meridian branches, fifteen collaterals, twelve meridian tendons, twelve skin areas and eight extraordinary vessels (see Table 1-1).
The twelve meridians are the trunk parts of the meridian system and "are connected with the viscera internally and limbs and skeleton externally" to transport qi and blood to the viscera, limbs and skeleton. The twelve meridian branches are the branches of the twelve meridians to reinforce the connection between the zang and fu organs externally and internally related and the meridians distributing over the head and face in external and internal relation. The fifteen collaterals stem from the twelve meridians and the conception and governor vessels as well as the spleen for reinforcement of the connection of the meridians with internal and external relationship on the four limbs as well as the association of the anterior, posterior and lateral parts of the trunk of the body.
The twelve meridian tendons stem from the twelve meridians for nourishing and governing the musculature and joints as well as for reinforcing the connection with the three yin meridians and three yang meridians at the same side. The twelve skin areas refer to the collaterals stemming from the twelve meridians and distributing over the skin areas. The system of the twelve meridians (excluding the collaterals of the conception and governor vessels as well as the major collateral of the spleen) extends with the distribution of the trunk parts of the twelve meridians and is the
base for the twelve meridians "to transport qi and blood, nourish yin and yang, moisten tendons and bones as well as smooth the joints". The eight extraordinary vessels distribute among the twelve meridians and function to connect and regulate qi and blood in the twelve meridians. So the twelve meridians form the core of the meridian system and the other parts in the meridian system function to connect, replenish and regulate the twelve meridians.
