Pericardium and Sanjiao: Ministerial Fire, the Envoy, and the Waterway Membrane Network
Pericardial Network
Section titled “Pericardial Network”The center of the chest (dan zhong) is “the official of the minister and envoy, from which joy and pleasure emerge.” It is described as the palace wall protecting the Heart. Because the Hand Jueyin vessel emerges from and belongs to the pericardium, the pericardial network is also called the Hand Heart-Master. Added to the Five Zang in this older scheme, it functions as a sixth zang.
Tang Zonghai explains the dan region as the anterior thoracic diaphragm and membrane extending around the flanks and spine, separating clearer from turbid influences. The pericardial network lies within this membranous region. It assists the Heart in distributing commands and therefore occupies the central chest. It belongs to Ministerial Fire and also governs Blood; when Blood supports Fire, Fire is harmonized rather than blazing, which is why this system is linked with joy. Worry in the Heart is interpreted as failure of Pericardial Fire to diffuse; excessive joy as excessive Pericardial Fire.
Sanjiao
Section titled “Sanjiao”Hua Tuo is quoted as saying: “The Sanjiao is the three-origin qi of the human body. It governs the nutritive and defensive, Qi and Blood, interior and exterior, inside and outside, above and below, left and right throughout the whole body. Therefore the eleven zang-fu are said to depend on Shaoyang.”
The Sanjiao is “the official of drainage, from which the waterways emerge.” In this interpretation it is identified with the membranous partitions and fatty-membrane network of the body. The omental network connects with the Bladder, allowing water to seep through the membranes into the Bladder, hence the metaphor of the drainage official.
The source of the Sanjiao is said to be rooted in the Kidney system. Between the two Kidneys, a fatty membrane runs along the spine and is called the origin of the jiao. From this system, membranous fat extends to the anterior diaphragm, ascends through the chest into the pericardial network, connects with the Lung system and throat, and externally reaches the arms, chest, and interstices—this is the Upper Jiao. Membranous fat extending toward the Small Intestine and outward to the waist and abdominal interstices is the Middle Jiao. Membranous and omental structures connecting posteriorly with the Large Intestine, anteriorly with the Bladder, and centrally with the reproductive chamber, then extending outward to the buttocks, lower legs, and lower abdomen, are described as the Lower Jiao.
Water that is drunk seeps through the Sanjiao into the Bladder; when drainage is free, the waterways remain open. When the Sanjiao is obstructed, the waterways close and swelling may appear externally. A classical passage states that Sanjiao disease may cause fullness of qi in the abdomen, particular firmness in the lower abdomen, urinary difficulty and urgency; when fluids overflow and remain, edema results.