The Meridians, the Primo Vascular System and the Brain

In classical acupuncture there are 12 major meridians and 2 midline meridians. The 12 major meridians are further divided into 6 yang (downward flowing) and 6 yin (upward flowing) meridians that are paired based on whether the associated organs are considered 'hollow' or 'solid'. This pairing creates a looping, longitudinal circuit that is continuously flowing Chi up and down the body. These meridians have superficial aspects that allow them to be needled (acupoints)