The 12 Meridian
The Meridians are directional pathways of the energy flow of Qi through the body, it could be said that the Qi flows through each different pathway(Meridians) in a peak flow at specific times during the day – in essence a 24 hour human body clock of qi flow. To the experienced practitioner or TCM therapist this can be used for diagnosis.

The twelve meridians are named according to their corresponding organs, limb positions and yin and yang properties. They include three arm yin meridians (lung, pericardium, heart), three arm yang meridians (large intestine, triple burner, small intestine), three leg yang meridians (stomach, gall bladder, bladder), and three leg yin meridians (spleen, liver, kidney). The triple burner and the pericardium do not refer to anatomical structures. They are functional units in TCM. It should also be noted, the organs mentioned here have a much broader meaning in TCM then what is typically thought of their functions in western medicine. Since the twelve meridians make up the majority of the Meridian System, they are known as the regular or principal channels.

Distribution of the twelve meridians in the body
The twelve Meridians have lateral and symmetrical distribution on the head, face, trunk and limbs. The six yin meridians are distributed on the inner side of the limbs and on the chest and abdomen. The six yang Meridians are distributed on the outer side of the limbs and on the head, face and trunk.

As shown in the diagram, the order and arrangement of the three yang meridians for both arms and legs are as follows: a) Yang Ming (meaning sunlight yang) has an anterior position. b) Shao Yang (meaning lesser yang) has a middle position. c) Tai Yang (meaning greater yang) has a posterior position. The three names have described the variation of yang qi. They can also be interpreted as describing the variation of sunlight received. Since most animals’ backs receive the greatest amount of sunlight, the back or posterior region is usually named as the Tai Yang position. Similarly, the position of Shao Yang and Yang Ming are located at more anterior regions where less sunlight is received.

The order and arrangement of the three yin meridians are as follows: a) Tai Yin (meaning greater yin) has an anterior position. b) Jue Yin (meaning absolute yin) has a middle position. c) Shao Yin (meaning lesser yin) has a posterior position. Again, the three names have described the variation of yin Qi and the degree of darkness at that position. The following figure has illustrated the general distribution of Meridians on the limbs.

The twelve meridians follow specific time schedules and pathways. The Huang Di Nei Jing (The Yellow Emperor’s Classic of Internal Medicine) says, " The three yins of the arm go from the organs to the hands. The three yangs of the arm go from the hands to the head. The three yangs of the legs go from the head to the feet. The three yins of the legs go from the feet to the abdomen." Qi is continuously circulating through the meridians in a daily cycle.