Concept of Body Fluid
Body fluid is a basic substance that makes up the body and maintains life activities. The main component of body fluid is water, also including nutrient substance. Body fluid is also a component of blood when it flows inside the vessels. However, body fluid also flows outside the vessels in the viscera and the body. If secreting or excreting from the five sensory organs and the nine orifices, body fluid becomes urine, sweating, tears, snivel, saliva and drool, etc.
Body fluid can be divided into two parts; thin fluid and thick fluid which are different from each other in property, location and functions. Generally speaking, thin fluid flows quickly and is distributed in the skin, muscles and orifices to moisten the related parts of the body. The thick fluid relatively flows slowly and is distributed in the viscera, cerebral marrow and joints to nourish the related parts of the body.
Though different in texture and distribution, both the thin and thick fluids come from food and water transformed by the spleen and stomach, functionally flowing inside and outside the vessels to permeate and supplement each other. Physiologically they are not strictly separated from each other; pathologically "impairment of the thin fluid" is relatively light while "loss of the thick fluid" is relatively serious.