The meridians and collaterals include the major trunks and minor branches. The meridian vessels have clearly defined pathways that penetrate deep into the body; the network vessels are their branches. The Gateway to Medicine states: “The meridians represent the main pathways and their ramifications are the collaterals.” There are two types of meridians: the twelve meridians and the eight extraordinary meridians.
Concerning the difference between the meridians and the extraordinary collaterals, The Salvation General Compendium states: There are ordinary and extraordinary meridians. The regular meridians are the twelve meridians. The eight extraordinary meridians are so named because they do not conform to the norm. Qi and blood constantly flow through the twelve meridians and, when abundant, overflow into the extraordinary meridians.
Let's discuss details of how each meridian works!