The Physiological Functions of Meridians and Collaterals
The functional activities of the meridians is called "meridian-qi," which manifest in the linking up of the exterior with the interior and the upper with the lower meridians, and in connecting the viscera with organs, in transporting qi and blood, in nourishing the viscera and tissues, responding, conducting and regulating the functions of every part of the body and so on.

1£®Linking up the Exterior with the Interior and the Upper with the ower, Connecting the Viscera and organs.

The human body consists of five zang-viscera and six-viscera, four extremities and joints, five sense organs and nine orifices, skins, muscles, endons, vessels and bones. Though there are differences in each ones' physical functions, they cooperatively act in their organic integral activities to create an organic whole from the interior and exterior and the upper and the lower portions of the body. This kind of organic combination and mutual communication is dependent on the connecting and linking-up functions of meridians and collaterals.

The twelve regular meridians and their branches crisscross, enter into the interior of the body and reemerge at the exterior; they run up and own, connect to the viscera and each other. The eight extra meridians connect with the regular meridians. The twelve meridian tendon regions, and skin areas connect with the tendons, vessels, skins and muscles. and they organically connect to each of the viscera, tissues and organs to form a coordinative integral whole in which the exterior and the interior and the upper and the lower are closely related. The connection and link of the viscera with the organs and tissues through the meridians and collaterals is shown in the following four aspects:

1) The Connection of the Viscera with the Extremities
This is mainly carried out by the twelve regular meridians. The twelve regular meridians connect with and pertain to the five-zang and six-fu viscera. Once affected, their meridian-qi scatters and gathers in the tendon regions, then distributes on the skin areas. Therefore the skin, tendons and muscles are connected with the internal viscera through meridians. Chapter 33 in the Spirit Pivot says: "The twelve regular meridians connect internally with the viscera, and externally with the joints, limbs and other superficial tissues of the body."

2) The Connection of the Viscera with the Five Sense Organs and Nine Orifices
The eyes, ears, nose, mouth, tongue, anterior privates; and anus are places where meridians pass through. Additionally, most meridians pertain to and connect with the viscera internally, thus, the five sense organs and nine orifices connect with internal viscera through the connection meridian. For example, the Heart Meridian of the Hand-Shaoyin pertains to the heart and connects with the small intestine, then goes upward to connect with the "ocular connectors." Its divergent collateral runs up to the tongue. The Liver Meridian of Foot-Jueyin pertains to the liver and connects with the gallbladder, then goes upward to connect with "ocular connectors." The Stomach Meridian of Foot-Yangming pertains to the stomach and connects with the spleen, enters the upper gum and curves around the lips.

3) The Connections Between the Viscera
Each of the twelve regular meridians separately pertains to and connects with one of the zang-viscera or fu-viscera, thus strengthening the connections of the viscera which are exteriorly-interiorly related. Moreover, some of meridians also connect together several viscera. For example, the divergent meridian of the stomach travels upwards to communicate with the heart; the spleen meridian enters into the heart; the divergent meridian of the gallbladder passes through the heart; the kidney meridian joins the heart; the heart meridian travels upward to the lung; the kidney meridian enters into the lung; the liver meridian enters into the lung; the small intestine meridian reaches the stomach; the liver meridian curves around the stomach; the lung meridian goes along the upper orifice the stomach; the kidney meridian passes through the liver and so on, thus instituting various relationships among the viscera.

4) The Connections Between Meridians
The connections of yin with yang meridians and the exterior with the interior meridians are in fixed order and exhibit a cyclical flow. The twelve regular meridians crisscross with the eight extra meridians; and the eight extra meridians connect with one another, thus establishing various communications between meridians. For example, the three yang meridians of the hand and foot converge on Dazhui acupoint of Du Meridian. Yangqiao and Du Meridians assemble in Fengfu acupoint, so Du Meridian is called "the of yang meridians." The three yin meridians of the foot and Yinwei, Chong Meridians converge in Ren Meridian, and the three yin meridians of foot extend upward to connect with the three yin meridians of the hand. Therefore the Ren Meridian is called "the sea of yin meridians." The Chong Meridian anteriorly merges into Ren Meridian in the chest, and posteriorly communicates with the Du Meridian, while the Du and Ren Meridians connect with the twelve regular meridians. Meanwhile, the Chong Meridian of "the up branches pass into the nasopharynx and pour into yang meridians; the down branches merge into Shaoyang Meridian and pour into three yin meridians,' (Chapter 80 in Spirit Pivot). The qi and blood which flow from all the twelve regular meridians, as well as the Du, Ren, Chong Meridians, emerge from uterus together. Therefore the Chong Meridian is also called "the sea of the twelve regular meridians."