The meridians are channels through which energy, or qi (pronounced “Chee”) and blood flow. They run very deeply through the body and reach the internal organs, bones, muscles, tissues, and skin. Generally, most meridians run longitudinally through the body, while their branches, called collaterals, run superficially and transversely. The whole system is a complex network that provides nourishment to every part of the body.
There are 12 main channels which are mirrored on either side of the body. Most of these are named after the organ with which they physically connect: the lung, large intestine, stomach, spleen, and so on. Two other important channels run along the midline of the body and are frequently used in treatments. Other groups of meridians called Extra and Divergent Channels supplement this vast invisible network.
The qi flows through the main channels in a cyclic pattern in an order with a specific direction: from the lung, to the large intestine, stomach, spleen, heart, small intestine, bladder, kidney, pericardium, triple burner (this meridian is named after an area of the body, not an organ), gall bladder, and finally the liver. Then, the cycle resumes again with the lung.
The meridians have several functions: they help transport the qi and blood of the body to provide nourishment, and they regulate the yin and yang energies to maintain equilibrium. The meridians also help the body to resist pathogens and they reflect signs of illness. For instance, if a person has a pathogenic flare-up in the liver channel, he or she may develop and eye infection, since the liver meridian opens into the eyes. A person with digestive problems may experience pain when a point along an intestinal meridian is pressed. Meridians also transmit the needle sensation, (that electrical feeling when the needle is inserted or manipulated) which signifies the “arrival of qi” to the area. This has an important therapeutic effect. The acupoints are places along the meridians where the qi is accessible. Manipluating the needles at these points can regulate an energetic deficiency or excess in order to bring about balance. This is the essence of acupuncture therapy.