I have read that there are 12 primary and 8 extra meridians in the body, are the 8 extra the 8 gates, and how would one open the 8 gates, is there a specific system or does practicing qigong eventually lead to controlling them. Can one detect the 8 gates in their body when practicing qigong. Moreover, if the 8 extra meridians are the 8 gates, then what are the 12 primary meridians?