In TCM, the internal organs of the human body are divided into three groups: "five zang-organs', "six fu-organs" and "extraordinary fu-organs". The five zang-organs include the heart, the liver, the spleen, the lungs and the kidneys. Preserving vital substances is their common characteristic. The six fu.-organs contain the gallbladder, the stomach, the large intestine, the small intestine, the urinary bladder and the triple-jiao. Their common characteristic is transmitting and digesting water and food. The extraordinary fu-organs refer to the brain, the medulla, the bone, the blood vessel, the gallbladder and the woman's uterus- six organs or tissues in all. Although also called "fu', "extraordinary fu-organs" are different from those of "the six fu-organs" mentioned above in function. So they are "extraordinary" .

     The Theory of ZangFu-Organs is one concerning the studies of the physiological functions and pathological changes of every organ of the human body, and their interrelationships. The formation of this theory is closely related to the following three factors. The. First is ancient anatomical knowledge. For instance, Jingshui Pian, a chapter on the fluid in the channels in the book Miraculous Pivot, says.. "When an eight-chi-tall adult stands upright before you, you can take his full height. When he dies, you can observe the details of his body through an autopsy. So you can get a general idea of whether his internal organs are solid or fragile, whether his Fu-organs are large or small, whether there is a lot of or a little food within his stomach, and whether his blood Vessels are long or short, and so on and so forth. " This shows that as early as 2 000 BC before TCM had already begun to perform autopsies on human body. The second factor is the observation of physiological and pathological phenomena. For example, if one catches cold because his skin has been affected by cold, he will have the signs and symptoms of a disorder of the respiratory system such as nasal obstruction, rhinorrhea and coughing. That is why TCM believes that the skin and hair have something to do with the nose and lungs, that is to say, with the respiratory system. The third factor is the summary of long term medical experiences. For instance, quite a few medicines which have the function of reinforcing the vital energy or essence of the kidney can accelerate the healing of the bone. This brings about the saying that the condition of the kidney determines the condition of the bone.

     It is needed to point out especially that in TCM the names of the internal organs are basically the same as those used in western medicine, but not all concepts are the same. For example, the functions of an organ in TCM may contain the functions of many organs in western medicine. Meanwhile, the function of an organ in western medicine may be contained in the functions of several organs in TCM. This is because in TCM zang or fu is not only an anatomic unit, but also a concept of physiology and pathology, and the latter is more important. For instance, the heart in TCM does refer to the same anatomic entity as in western medicine. In addition, however, it also refers to some of the functions of the nervous system, especially some of those of the brain. The difference in concepts between TCM and western medicine is mainly due to the difference in the way of looking at things. TCM gathers its knowledge of the internal organs mainly from repeated practice and observation, whereas western medicine bases its knowledge mainly on repeated autopsies, experiments and summaries.  Hence, in learning the theory of TCM concerning zangfu-organs you should, first of all, have a clear idea of what it is all about, and then make further inquiries and studies of it through the step-by-step adoption of modern technical knowledge and method so as to bring to light its essence.