The transportation and metabolism of body fluid are complicated, involving the physiological activities of several viscera. Body fluid, produced by the spleen and the stomach to absorb water and nutrients from food, is transported to the heart and the lung by the spleen to start its metabolic process. The viscera concerned with the metabolism of body fluid mainly include the spleen, the lung and the kidney as well as the heart, the liver, the bladder, the large intestine and the triple energizer.
The spleen, the lung and the kidney play a key role in the transportation and distribution of body fluid. The spleen, governing transportation and transformation, transports body fluid to the heart and the lung; the lung, governing the regulation of water passage, transports body fluid to the whole body and down into the kidney; the kidney, governing water and separating the clear from the turbid, again transports body fluid that is steamed and qi-transformed during the formation of urine into the heart and the lung. In propelling the circulation of blood, the heart also promotes the flow of body fluid.
In this way body fluid is transported to the whole body to nourish the five zang-organs and the six fu-organs. After being used, the rest of water and the waste metabolic materials are excreted out of the body through certain routes. The excretion of body fluid involves the lung, the kidney, the bladder and the large intestine. Lung-qi governing dispersion, depturation and descent, excretes the fluid from the skin and respiratory tract and excretes the fluid together with feces from the large intestine.
Kidney-qi, governing water, transforms the fluid into urine to be excreted as urine from the bladder. Among these different routes, urination and sweating are the major ones for the excretion of the fluid. Only part of the fluid is excreted through defecation and respiration.
Besides, the liver and the triple energizer also play a certain role in the distribution and excretion of body fluid. Liver-qi, governing dredging and dispersing, promotes the flow and metabolism of body fluid by means of regulating the activity of qi; the triple energizer, serving as a water passage, directs body fluid to flow downward through it to the kidney. In the whole process of the flow and metabolism of body fluid, the triple energizer, connecting the upper with the lower, participates in the whole process of the production, distribution and excretion of body fluid.
To be specific, the upper energizer participates in the distribution of body fluid as implied in the idea that "the upper energizer is like fog"; the middle energizer participates in the absorption of body fluid as implied in the idea that "the middle energizer is like maceration"; the lower energizer participates in the excretion of body fluid as implied in the idea that "the lower energizer is like a sewer".
On the whole, the flow and metabolism of body fluid involve several viscera, but the lung, the spleen and the kidney are the most important ones. So the dysfunction or hypofunction of these three organs will affect the flow and metabolism of body fluid, leading to phlegm, retention of fluid and edema.