Pericardium

膻中 shānzhōng (chest centre) or 心包 xīnbāo (heart wrapper), is the solid, yin organ (藏 záng) related to the ministerial fire phase. It acts as a protective layer between the heart and the outside world.

It is compared to a minister and envoy who reports to the ruler and issues their edicts to the populace, so that the ruler is not exposed to harm and remains joyful.

Its yin–yang property is considered reversing yin (厥陰 or 厥阴 juéyīn).