This article is very well written. Below are some summarized points; for detailed arguments, please refer to the original text[1].
Generation of Ying and Wei Qi
Ying Qi (Nutritive Qi) and Wei Qi (Defensive Qi) originate from food and drink, as well as the essential qi of the five zang organs and Yuan Qi (Original Qi). First, the essential qi of the five zang organs and Yuan Qi receive the essence from food and drink, which is then transformed into Ying and Wei Qi. These further nourish the zang organs and replenish Yuan Qi, forming a continuous cycle.
Distribution and Circulation of Ying and Wei Qi
Ying Qi flows within the meridians and completes fifty cycles around the body, while Wei Qi circulates outside the meridians. They often travel together in minor conjunctions (“small meetings”). After each completes fifty cycles along the meridians, they reunite in a major conjunction (“great meeting”).
Wei Qi circulates through the body during the day and through the internal organs and body at night.
Functions of Ying and Wei Qi
The term “Jing Qi” (Meridian Qi) commonly refers to Ying Qi. The so-called “meridians” are actually the pathways along which Ying Qi flows. All functions of the meridians depend on Ying Qi, including nourishing the internal organs and physical structures, connecting the interior with the exterior and upper with lower parts of the body, and regulating overall balance. Under certain conditions, Ying Qi can transform into blood.
Wei Qi has functions of warming, moistening, filling, controlling movement, and defending against external pathogens.
Ying Qi governs sensation, while Wei Qi governs movement; both are related to mental and conscious activities.
Ying and Wei Qi jointly regulate the body’s sleep-wake rhythm.
Relationship among Zong Qi, Ying Qi, and Wei Qi
Zong Qi (Gathering Qi) essentially consists of accumulated Ying and Wei Qi gathered in the chest.
References
Discussion on Ying Qi, Wei Qi, and Zong Qi _ Sun Chenyao.pdf (1.5 MB)