The complicated physiological generation and metabolism of Body Fluid is performed by mutual actions of several viscera. The formation of Body Fluid is a purification process performed in stages, which separates the fluid into pure and impure fractions.
Body Fluid is produced first by digestion of the Stomach and the action of the Spleen, and undergoes its separation into pure and impure liquid. The pure portion of the fluid is transported to the Lung to be dispersed throughout the body and descended to the Kidney. The Small Intestine receives the impure portion and further refines it to recover another pure fraction. The impure fraction is sent to the Bladder. The Large Intestine receives the waste portion and absorbs part of the fluid while letting the balance become part of the fecal material to be removed from the body. The Kidney also purifies the fluid descended by the Lung, misting the Lung with the pure fraction and sending the waste fluid to the Bladder. Finally, the Bladder receives fluids from the Small Intestine and Kidney and recovers any remaining pure fluid to vaporize it and send it up while the waste portion is destined to leave the body as urine.
The Basic Questions says, “Fluids enter the Stomach and are separated. A pure part flows up from the Spleen to the Lung, which directs the pure part to the water circulation and then the impure down to the Bladder” .
Body Fluid distribution and excretion are mainly accomplished through the San Jiao () passages by the Lung’s dispersing and descending actions, the Spleen’s transportation function, the transforming and steaming processes of Kidney-Qi, and the dredging capability of Liver-Qi. The Lung’s dispersing action sends Body Fluid to nourish and moisten the crevices under the skin, and then the metabolized fluid is excreted out of the body through the pores as sweat.
The Kidney, in particular Kidney-Yang, controls many stages of fluid transformation. Kidney-Qi plays an important role in the overall equilibrium and metabolism of Body Fluid.
The body discharges fluid as urine, sweat, moist exhalation, and water in feces. Actually, Qi, Blood, and many viscera influence Body Fluid metabolism and may potentially cause some problems, such as the deficiency or disturbance of Body Fluid circulation or the accumulation of water, etc.