The zang-fu theory explains the physiological function, pathological changes, and mutual relationships of every zang and fu organ. In traditional Chinese medicine the zang and fu organs are not simply anatomical substances, but more importantly represent the generalization of the physiology and pathology of certain systems of the human body. Zang and fu consist of the five zang and six fu organs.

The five zang organs:
heart (including the pericardium)
lung
spleen
liver
kidney

The six fu organs:
gall bladder
stomach
large intestine
small intestine
urinary bladder
sanjiao (three areas of the body cavity).

Zang and fu are classified by the different features of their functions. The five zang organs mainly manufacture and store essence: qi, blood, and body fluid. The six fu organs mainly receive and digest food, absorb nutrient substances, transmit and excrete wastes.

As the Suwen says: The five zang organs store up essential qi and regulate its outflow. The six fu organs transform and transport substances without storing them and for this reason they may be over-filled but cannot be filled to capacity.

There is another category of organs called the extraordinary fu organs which include the brain, marrow, bone, vessels, gall bladder, and uterus. They are named fu but their functions are similar to that of the five zang organs. Since their physiological functions and pathological changes are closely connected with the zang-fu organs they will be discussed below under the specific zang or fu organ.