The Pericardium is also called the "heart protector," and, for clinical purposes, is considered a yin organ paired with the yang organ San Jiao. In general theory, the Pericardium is not distinguished from the Heart. It is also the first line of defence against the Heart from External Pathogenic Influences. The Pericardium has a meridian named for it, which reflects the health of the organ. In terms of the Five Elements, these organs are both associated with the fire element. In treatment, it is often best to approach heart problems via the Pericardium, rather than directly. The peak time for the Pericardium is from 7-9pm
Zang - fu is the general term for the organs of the human body, and includes the six zang organs, the six fu organs and the extraordinary fu organs.
Since the pericardium is a protective membrane of the heart, the " extraordinary fu " organs pertain respectively to the other fu organs, it is generally called five zang and six fu organs.
For this reason, there are established standards by which we determine the hardness and crispness of the zang organs, the size of the fu organs, the quantity of food consumed, the length of the vessels, the clarity and turbidity of the blood, the quantity of qi in the body..