The meridians spread out through the entire body connecting all the tissues and organs of the body binding it together as an organic unit. They regulate normal functioning of the body, and diagnostically reflect pathology or illness. Meridians are also referred to as Vessels, Chings, or Channels.

In acupuncture we generally consider that there are 72 channels of therapeutic importance:

12 Primary Meridians
12 Tendinomuscular Meridians
12 Transversal Lo Vessels
12 Longitudinal Lo Vessels
12 Distinct (Divergent) Meridians
8 Extra (Ancestral) Vessels
3 Extra Longitudinal Lo Vessels
1 Huato Channel
The most important and essential ones for the circulation of Qi, and for most therapeutic applications are the twelve Primary Meridians and two of the Extra Vessels. The twelve Primary Meridians are also known as the twelve Chings.