The meridians are channels in which qi and blood flow; they form a network which communicates with the internal organs and the limbs, and connects the upper part of the body to the lower one and the inside of the body to the outside.

The meridians that run lengthwise and deep within the body are called jing, and those running crosswise and close to the surface of the body are called luo (or collaterals) and are branches of the longitudinal meridians.

The following meridians (jing) run through every human body:

  • 12 principal meridians – the pathways in which qi and blood flow, distributed symmetrically on the right and left side of the body, and associated with the zang-fu organs:
    • 3 yin meridians of the hand: lung meridian, pericardium meridian, heart meridian
    • 3 yin meridians of the foot: spleen meridian, liver meridian, kidney meridian
    • 3 yang meridians of the hand: large intestine meridian, triple burner meridian, small intestine meridian
    • 3 yang meridians of the foot: stomach meridian, gallbladder meridian, urinary bladder meridian

The yin meridians correspond to the zang organs and are distributed on the inner side of the upper and lower limbs, the chest and the abdomen; the yang meridians correspond to the fu organs and are distributed on the outer side of the upper and lower limbs, the head and the torso.

  • 8 extra meridians – they are not directly associated with any internal organ, they are distributed among the main meridians, crossing them and intersecting with them:
    • Du Mai (also called governing vessel)
    • Ren Mai (also called conception vessel)
    • Chong Mai
    • Dai Mai
    • Yinqiao Mai
    • Yangqiao Mai
    • Yinwei Mai
    • Yangwei Mai

The function of these meridians is to help communication between the principal meridians and regulate the flow of qi and blood in them: the surplus qi and blood in the principal meridians flow into and are stored in the extra meridians; any insufficiency of qi and blood in the principal meridians is supplemented by the qi and blood stored in the extra meridians. The extra meridians are closely related to the liver, kidneys, uterus, brain and marrow.

  • 12 divergent meridians – they are extensions of the 12 principal meridians and run deeper into the body, thus enhancing communication between yin-yang meridians and ensuring coordination between the body’s exterior and interior

Collaterals (luo) are grouped into:

      –      large collaterals – which extend from the principal meridians and from the Du and Ren meridians; they are 15 in total
      –      superficial collaterals (beneath the skin)
      –      minute collaterals

There are also:

– 12 musculo-tendinous regions – muscular portions along the routes of the principal meridians, which connect bones and joints of the body and maintain mobility

– 12 cutaneous regions – superficial portions of the body that respond to the functions of the principal meridians