“In traditional Chinese medical theory, the human body is regarded as a microcosm of the universe. The external world, blood, saliva and five vital organs are viewed as “yin”; qi (breath, also a source of vitality) and six bodily organs are “yang.”

It is believed that illness is caused by the disorder of yin and yang in the human body. The categorization of five vital organs, namely hsin (heart), kan (liver), pi (spleen), fe (lung) and shen (kidneys), and six bodily organs in Chinese medicine is not only based on the names of these organs but also on their physical function. For example, “heart” means the organ pumping blood through the body in modern medicine, whereas it may be referred to the circulatory system and nervous system as a whole in Chinese medicine apart from a single organ.

For instance, the heart is in charge of growth and similar to the sun, so it stands for “fire.” The lung controls retrieval and collection, also “metal” in five natural elements. The spleen is in charge of development, also “earth”; the liver manages vitality, also “wood”; the kidneys, controlling storage by nourishing the body and discharging waste liquid, are called “organ of water” and belong to “water” in five natural elements.

The function and activity of five vital organs in the human body re closely related, rather than separated in operation. These organs interact with each other in a very complex process of developing and restraining each other, which can be explained by the notion of the “five vital organs circle”.

For example, “wood develops fire” means that the liver (wood) cultivates heart (fire). In other words, if the liver functions well in blood storage, it will help the heart enhance good circulation. Since fire develops earth, the heart (fire) keeps the spleen (earth) warm; if the heart enhances good circulation, it will nourish the spleen and helps it in the development, movement, creation and management of blood. Since earth develops metal, the spleen (earth) contributes to the good function of the lung (metal); if the spleen is able to keep the development of qi in normal and produce qi and blood, the lung can manage both qi and respiration well with the nutrition transited from the spleen.