The heart has an "exterior" (biao) and "interior" (li) relationship with the small intestine.

Dominating Blood and Vessels, and Facial Complexion

The heart dominates the blood and vessels indicating its function of promoting blood circulation. In the Suwen, it says, "... The heart is in charge of the blood vessels ...." The vessels are the pathways of blood circulation while the heart is the motive power of blood circulation. Only if there is ample heart qi can the blood circulate incessantly in the vessels to nourish the whole body. The heart, blood, and vessels are interrelated. Because of the rich distribution of blood vessels in the facial region, the color and luster of the complexion usually reflects the sufficiency or insufficiency of the blood supply and heart qi. If the heart blood supply is sufficient, then the pulse beats normally and forcefully and the facial complexion is rosy with luster. If the heart qi is insufficient, the vessels will be empty, the pulse feeble and weak or irregular and the facial complexion pale. Insufficient heart qi may lead to blood stagnation manifested by a blue complexion. So in the Suwen is says, "The heart is the root of live, ... its luster is manifested in the face, it fills up the blood vessels ..."

Controlling the Mind

Mind here indicates spirit, consciousness, and thinking. Traditional Chinese medicine considers that mind refers to the five zang organs, especially the heart. So in the Lingshu it says, "The organ that is responsible for the performance of activities is the heart." This means the process of thinking is accomplished by the heart. Blood is the main foundation for mental activities, thus the function of heart controlling the mind is closely related to the function of heart dominating the blood and the vessels. If there is plenty of heart blood, the mind is clear, thinking is nimble, and one is full of vim and vigor. If heart blood is insufficient, it will lead to the pathological changes of heart-mind manifested by palpitation, insomnia, dream disturbed sleep, poor memory, restlessness, etc. If heat in the blood disturbs the heart-mind, there will be delirium, coma, etc.

Opening into the Tongue

One of the branches of the heart channel directly connects with the tongue. So physiologically the tongue has a close relationship with the heart. The qi and the heart blood all flow up to the tongue in order to assist its normal physiological functions. If there is a pathological change in the heart, it will be reflected in the changes of the tongue. For example, an insufficient supply of heart blood may be manifested by pale tongue proper; heart fire flaring up is reflected by red tongue proper, or even by ulcers of the tongue; blood stagnation in the vessels in presented by a purple tongue or purpura; pathogenic heat invading the pericardium or pathogenic phlegm obstructing the heart orifice, will produce coma, delirium, and stiffness of the tongue. Thus it is said, "The heart opens to the tongue," or "The tongue is the sprout of the heart."

Pericardium

The pericardium is called xinbaoluo in Chinese. Structurally it is a membrane surrounding the heart, and physiologically it protects the heart. When exogenous pathogenic factors attack the heart, the pericardium is affected first. The Lingshu notes, "Therefore the pathogenic factors that intend to attack the heart must first attack the pericardium." Clinically the symptoms of pathogenic invasion of the pericardium are the same as if the heart was ill. If pathogenic heat attacks the heart, the symptoms are unconsciousness, delirium, etc. If pathogenic phlegm causes mental confusion, unconsciousness or mental disorder, it is known as "pathogenic phlegm obstructing the heart orifice."