The theory of the zang-fu organ systems is linked to the theory of
vital substances and the theory of the five phases of transformation
(wu xing). Each zang-fu organ system is associated with a particular
phase of the transformation and transportation of the various vital
substances.
There
are five zang-fu organ systems, each system consisting of one zang
organ and one fu organ. This chart demonstrates characteristics of zang
and fu organs.
| Zang Organs | Fu Organs |
| Yin | Yang |
| Relatively solid internal structures | Hollow structures |
| Involved in transformation and storage of vital substances | Involved in the transportation of partially transformed substances |
Each zang organ is associated with a fu organ, creating five yin-yang organ systems. Each of these organ systems corresponds with one of the five phases of transformation. This is shown below.
| Zang | Fu | Phase |
| Spleen | Stomach | Earth |
| Lung | Large intestine | Metal |
| Kidney | Bladder | Water |
| Liver | Gall bladder | Wood |
| Heart | Small intenstine | Fire |
The harmony of yin and yang, and therefore good health, is manifested in the harmonious interaction between the zang and fu organ systems. When there is disharmony within or between any of the zang fu organ systems, there will be signs and symptoms that correspond with the zang or fu system affected. These signs and symptoms create patterns that can help guide the practitioner to a diagnosis and the appropriate treatment strategy.