The human body is a unified organic whole, composed of various organs such as the viscera and meridians. The functional activities of each organ, tissue, and system are not independent but are components of a holistic activity. They not only exist in a relationship of mutual restriction, interdependence, and mutual use in physiological functions; they also communicate through the meridians, transmitting various information among the organs. Under the circulation of qi, blood, and body fluids throughout the body, a highly coordinated and unified whole is formed.
The Relationship Between the Five Organs
The relationship between the organs has traditionally been explained by the interactions of the Five Elements (Wu Xing) in terms of generation and restriction. However, through the observations and studies of physicians over the ages, the relationship between the organs has transcended the scope of the Five Elements, and is now explained based on the physiological functions of each organ.
1.1 Heart and Lung
The relationship between the heart and lungs primarily involves the heart governing blood and the lungs governing qi, as well as the heart’s role in circulating blood and the lungs’ role in respiration. “All blood belongs to the heart,” and “all qi belongs to the lungs”; thus, the relationship between the heart’s governance of blood and the lungs’ governance of qi is essentially one of mutual dependence and utility between qi and blood.
The lungs govern the dispersal and descending of qi and can promote the heart’s function of circulating blood, making them a necessary condition for the normal operation of blood, in accordance with the general principle that “qi is the commander of blood.” Conversely, only with normal blood circulation can the lung’s respiratory function be maintained, hence the saying “the heart is expelled through the lungs,” which also aligns with the general principle that qi resides in blood. The central link connecting the heart’s pulsation and the lung’s respiration is primarily the “Zong Qi” (Ancestral Qi) accumulated in the chest. Since Zong Qi has the physiological function of traversing the heart meridian and governing respiration, it strengthens the coordination and balance between blood circulation and respiration. Therefore, whether it is lung qi deficiency or lung failure to disperse, both can affect the heart’s function of circulating blood, leading to abnormal blood flow, stagnation, and symptoms such as chest tightness, changes in heart rate, and even pathological phenomena like cyanosis of the lips and purplish tongue due to blood stasis. Conversely, if there is insufficient heart qi or heart yang deficiency, or if there is obstruction in the heart meridian leading to abnormal blood flow, it can also affect the lung’s dispersal and descending functions, resulting in cough, shortness of breath, and other pathological phenomena of lung qi rebellion. This illustrates the pathological mutual influence between the heart and lungs.
1.2 Heart and Spleen
The heart governs blood, while the spleen regulates blood and is the source of the generation of qi and blood. Therefore, the relationship between the heart and spleen is particularly close. When the spleen’s transportation function is normal, its ability to generate blood is vigorous. When blood is abundant, the heart can govern it. If the spleen qi is robust and its function of regulating blood is normal, then blood flows within the vessels and does not leak outside. Thus, the relationship between the heart and spleen is primarily reflected in the generation and circulation of blood. Pathologically, the heart and spleen often influence each other; for example, excessive thinking can not only deplete heart blood but also affect the spleen’s transportation function. If the spleen qi is weak and its transportation fails, then the generation of qi and blood will lack a source, leading to blood deficiency and the heart being unable to govern. If the spleen fails to regulate blood, causing blood to flow erratically, it can also result in insufficient heart blood. All these conditions can lead to pathological changes characterized by dizziness, palpitations, insomnia, vivid dreams, abdominal distension, poor appetite, fatigue, and a pale complexion, known as “deficiency of both heart and spleen.”
1.3 Heart and Liver
The heart governs blood, while the liver stores blood. The blood in the body is generated in the spleen, stored in the liver, and circulated throughout the body via the heart. When the heart’s function of circulating blood is normal, blood flow is normal, and the liver can store blood; if the liver fails to store blood, the heart cannot govern, and blood circulation will inevitably be abnormal. Due to the close relationship between the heart and liver in terms of blood circulation, “heart and liver blood deficiency” often occurs clinically.
The heart governs the spirit, while the liver governs the smooth flow of emotions. Although the heart governs mental activities, it is also closely related to the liver’s function of smooth flow. Emotional disturbances can lead to excessive fire damaging yin, thus clinically, heart and liver yin deficiency and heart and liver fire excess often influence each other or occur simultaneously.
1.4 Heart and Kidney
In the Five Elements, the heart is associated with fire and is located above, representing yang; the kidney is associated with water and is located below, representing yin. According to the theory of the rise and fall of yin and yang, what is below should rise, and what is above should descend. “When the rising has risen and the descending has descended, the descending is heaven; when the descending has risen and the rising has descended, the rising is earth. The heavenly qi descends, and the earthly qi rises” (from the “Suwen: Discussion on Subtlety”), illustrates the rise and fall of yin and yang, water and fire from the cosmic perspective. Therefore, theoretically, heart fire must descend to the kidney, and kidney water must ascend to the heart, so that the physiological functions between the heart and kidney can be coordinated, referred to as “heart-kidney intersection,” or “water and fire harmonized.” Conversely, if heart fire cannot descend to the kidney and is overly vigorous, and kidney water cannot ascend to the heart and becomes stagnant, then the physiological functions between the heart and kidney will lose coordination, leading to a series of pathological phenomena known as “heart-kidney disconnection,” or “water and fire disharmony.” For example, clinical manifestations primarily characterized by insomnia, palpitations, anxiety, and weakness in the lower back and knees, or symptoms such as nocturnal emissions in men and dream intercourse in women, often belong to “heart-kidney disconnection.”
Additionally, since there is also a close relationship between the yin and yang of the heart and kidney, when either the heart or kidney is affected, they can influence each other. For instance, kidney yang deficiency leading to water overflowing can ascend to the heart, resulting in symptoms such as edema and palpitations, known as “water qi invading the heart”; heart yin deficiency can also draw from kidney yin, leading to symptoms of yin deficiency and excess fire.
1.5 Lung and Spleen
The close relationship between the lungs and spleen primarily involves the generation of qi and the distribution and metabolism of body fluids. The generation of qi in the body mainly relies on the respiratory function of the lungs and the transportation function of the spleen. The clear qi inhaled by the lungs and the essence of food and drink transformed by the spleen and stomach are the main material basis for the formation of qi. Therefore, the strength of the lung’s respiratory function and the spleen’s transportation function is closely related to the abundance or deficiency of qi.
In terms of the distribution and metabolism of body fluids, it mainly involves the lung’s dispersal and descending, regulating the water pathways, and the spleen’s transportation of body fluids. The lung’s dispersal and descending, along with regulating the water pathways, assist the spleen’s function of transporting body fluids, thus preventing the generation of internal dampness; while the spleen’s transportation of body fluids and dispersing essence to the lungs is not only a prerequisite for the lung’s regulation of water pathways but also provides necessary nourishment for the lung’s physiological functions. Therefore, there exists a mutually beneficial relationship between the two in the distribution and metabolism of body fluids.
The pathological mutual influence between the lungs and spleen mainly involves insufficient qi generation and abnormal metabolism of body fluids. For example, when spleen qi is deficient, it can often lead to insufficient lung qi; if the spleen fails to function properly, leading to fluid metabolism disorders and stagnation of body fluids, it can result in phlegm accumulation and affect the lung’s dispersal and descending, leading to clinical manifestations such as wheezing, cough, and excessive phlegm. Thus, it is said that “the spleen is the source of phlegm, and the lungs are the container of phlegm.” Of course, chronic lung disease can also affect the spleen, leading to dysfunction of the spleen’s transportation function or spleen qi deficiency, resulting in symptoms such as poor appetite, abdominal distension, loose stools, and even edema, known as “upper disease affecting the middle,” which is also the theoretical basis for the treatment method of “nurturing earth to generate metal.”
1.6 Lung and Liver
The relationship between the lungs and liver primarily manifests in the regulation of qi dynamics. The lungs govern descending, while the liver governs ascending; their mutual coordination is an important link for the smooth flow of qi throughout the body. If the liver ascends excessively or the lungs descend insufficiently, it can lead to qi fire rebellion, resulting in symptoms such as cough with upward qi, and even hemoptysis, known as “liver fire invading the lungs.” Conversely, if the lungs fail to clear and disperse, with internal heat and dryness, it can also affect the liver, leading to liver dysfunction and poor smooth flow, resulting in symptoms such as cough accompanied by chest and rib pain, dizziness, headache, and flushed face and eyes.
1.7 Lung and Kidney
The relationship between the lungs and kidneys primarily involves the metabolism of body fluids and respiratory movements. The kidneys are the main organ of water, while the lungs are the “upper source of water”; the lung’s dispersal and descending and regulation of water pathways depend on the kidney’s vaporization and qi transformation. Conversely, the kidney’s function of governing water also relies on the lung’s dispersal and descending and regulation of water pathways. Therefore, if the lungs fail to disperse and regulate the water pathways, it will inevitably affect the kidneys, leading to reduced urination and even edema; if the kidney’s qi transformation is impaired, leading to poor closure, it can result in water retention and even lead to symptoms such as wheezing and cough, making it difficult to lie flat. “The root is in the kidney, and the end is in the lung; both are water accumulation” (from the “Suwen: Discussion on Water and Heat”).
The lungs govern exhalation, while the kidneys govern inhalation; the lung’s respiratory function requires the kidney’s inhalation function to assist. When kidney qi is abundant, the inhaled qi can descend through the lung’s dispersal and be absorbed by the kidneys, hence the saying “the lungs are the master of qi, and the kidneys are the root of qi.” If the kidney’s essence is insufficient, unable to absorb properly, qi will float upwards; or if lung qi is chronically deficient, leading to kidney involvement, it can result in the kidneys being unable to absorb qi, leading to symptoms such as shortness of breath upon exertion.
Additionally, the yin fluids between the lungs and kidneys also mutually nourish each other; kidney yin is the root of all body fluids, so lung yin deficiency can damage kidney yin. Conversely, kidney yin deficiency cannot nourish lung yin. Therefore, lung and kidney yin deficiency often occur simultaneously, presenting symptoms such as rosy cheeks, tidal fever, night sweats, dry cough with a hoarse voice, and weakness in the lower back and knees.
1.8 Liver and Spleen
The liver stores blood and governs smooth flow, while the spleen regulates blood, governs transportation, and is the source of qi and blood generation. The relationship between the liver and spleen primarily lies in the mutual influence between the liver’s smooth flow function and the spleen’s transportation function. The spleen’s transportation relies on the liver’s smooth flow; when the liver’s smooth flow function is normal, the spleen’s transportation function is robust. If the liver fails to smooth flow, it will affect the spleen’s transportation function, leading to pathological manifestations of “liver-spleen disharmony,” which can present as mental depression, chest and rib fullness, abdominal distension and pain, and diarrhea with loose stools.
Secondly, the liver and spleen also have a close relationship in terms of blood generation, storage, and circulation. When the spleen functions well, it generates blood, and blood does not leak outside the vessels, allowing the liver to store it. If the spleen is deficient and lacks a source for generating qi and blood, or if the spleen fails to regulate blood, leading to excessive blood loss, it can result in liver blood deficiency.
Additionally, if there is damp-heat stagnation in the spleen and stomach, leading to bile heat leakage, it can result in jaundice. Thus, pathologically, liver disease can affect the spleen, and spleen disease can also affect the liver; the liver and spleen often influence each other in pathological changes.
1.9 Liver and Kidney
The relationship between the liver and kidneys is extremely close, often referred to as “liver and kidney sharing the same origin.” The liver stores blood, while the kidneys store essence. The relationship between blood storage and essence storage is essentially one of mutual nourishment and transformation between essence and blood. The generation of blood relies on the qi transformation of essence in the kidneys; the abundance of essence in the kidneys also relies on the nourishment of blood. Therefore, it is said that essence can generate blood, and blood can transform into essence, referred to as “essence and blood sharing the same origin.” Pathologically, changes in essence and blood often influence each other. For instance, kidney essence deficiency can lead to liver blood deficiency; conversely, liver blood deficiency can also cause kidney essence deficiency.
Moreover, the liver’s function of smooth flow and the kidney’s function of storage have a mutually restrictive and complementary relationship, primarily reflected in the physiological functions of menstruation in women and ejaculation in men. If there is an imbalance between the two, it can lead to irregular menstrual cycles in women, excessive menstrual flow, or amenorrhea; in men, it can lead to nocturnal emissions or inability to ejaculate.
Since the liver and kidneys share the same origin, the relationship between the yin and yang of the liver and kidneys is extremely close. The yin and yang of the liver and kidneys are interconnected, mutually restrictive, and balanced; thus, pathologically, they often influence each other. For example, kidney yin deficiency can lead to liver yin deficiency, causing yang to be unrestrained and resulting in liver yang hyperactivity, known as “water not containing wood”; conversely, liver yin deficiency can lead to kidney yin deficiency, resulting in hyperactivity of the fire.
1.10 Spleen and Kidney
The spleen is the foundation of the acquired, while the kidneys are the foundation of the congenital. The healthy function of the spleen relies on the warmth provided by kidney yang, hence the saying “spleen yang is rooted in kidney yang.” The essence in the kidneys also relies on the nourishment and cultivation of the essence from food and drink to continuously fill and mature. Therefore, the spleen and kidneys have a physiological relationship of acquired and congenital, mutually supporting and promoting each other. Pathologically, they often influence each other, being mutually causal. For instance, if kidney yang is insufficient and cannot warm the spleen yang, it can lead to symptoms such as abdominal cold pain, clear diarrhea, or edema. If spleen yang is chronically deficient, it can further damage kidney yang, leading to the syndrome of spleen and kidney yang deficiency.