Physiological Functions of the Liver
1) Domination of the Conducting and Dispersing
The literal sense of this phrase "The liver dominates the conducting and dispensing," indicates a comprehensive physiological function within the dredging, smoothing, flowing, and dispersing of life activity within the body. Ancient physicians likened this function to that of trees in the natural world. The trees and plants would begin to sprout in nature when they are supplemented by spring-wind containing a warmer energy. Then the flora will freely develop their branches and leaves. So, the liver is like the trees in the spring, which are in full bloom and bursting with life, and who's features make people vigorous and vital.
The physiological function of the liver in dominating the conducting and dispersing encompass a vast scope: On one the hand, it displays the physiological state of the softness and unfolding in the liver itself, while on the other hand, it relates to the unobstructed functional activity of qi in the human body. The metabolism of various kinds of material are accomplished through the process of "ascending, descending, exiting, and entering" of the liver qi. When it is functioning normally, the qi mechanism is smooth and regular, the qi and blood harmonious, the meridians unobstructed, the activities of the viscera and organs coordinated, and consequently, all types of nutrients will be transformed. The waste material and water will be excreted freely. If this function is impaired, the functional activity of qi will be blocked, resulting in abnormal manifestations
of emotion, digestion and circulation of the qi, blood, and water. Also, as this continues, pathological changes of stagnation of the liver, the liver-fire, and the liver-wind will occur. The liver's function in dominating the conducting and dispersing, within its physiological activity is shown as follows.
a. Regulating emotional activities
The emotional changes of the human being are normal responses to the brain signifying stimulation of the external world. Traditional Chinese medicine believes that emotional activity is also very much related to the function of the liver in dominating conducting and dispersing, which in this case is governed by the heart. If this liver function is normal, the activity of the qi will be smooth, the emotional life happy, the mind at ease, the qi and blood harmonious, and the five zang-viscera in coordination. Conversely, if it is not, the functional activity of the qi will be in imbalance. Abnormality of the mental and emotional activities may result in the following two aspects. First, when the function of the liver in conducting and dispersing is weakened, there appears stagnation of the functional activity of qi in the body. Simultaneously, this is accompanied by such symptoms as emotional depression, unhappiness, moodiness, excessive worry, belching, sentimental sighing, etc. This is known as "stagnation of liver-qi. " Secondly, hyperactivity of the
liver in conducting and dispersing causes emotional excitement, and such symptoms as headaches with distending sensations in the head, flushed face, irascibility, exasperation, agitation, difficulty failing asleep, etc. These are called "hyperactivity of the liver-fire. "Additionally, the function of the liver in regulating emotional activities is closely related to the liver storage of blood. This is also called "the liver stores blood, which houses the etherial soul. " when liver-blood is ample, and the liver's body adequately nourished, its function of conducting and dispersing will be normal. The liver will have the capability to
regulate emotional activity. If liver-blood is impaired, the function will be abnormal, and excessive dreams will disturb sleep, one will be frightened, insomnia may result, and sleep-walking may occur.
Failure of the liver in dominating the conduction and dispersing activity can cause disturbances of emotional activity as well. The stimulation of the seven emotional factors,in particular, anger, or persistent and repeated harmful stimulations, can actually lead to pathological changes of stagnation of liver-qi, or qi stagnation and blood stasis. This is the reason why it is said in traditional Chinese medicine that "The liver favors a smooth flow of qi and has an aversion to stagnancy," and "Excessive anger injures the liver. "
b. Aiding digestion and absorption
Digestive functions of the human body involve physio-biochemical processes of receiving and decomposing the diet, and of distributing and absorbing the essential substances of drink and food. These physiological activities are performed mainly by the spleen and stomach, but also require the action of the liver in its roles of dominating the conducting and dispersing. This allows for the digestive processes to proceed normally.Dr. Tang Rongchuan said: "Alimentary qi goes into the stomach, which depends on the conducting and dispersing function of liver-qi, allowing food and drink to be digested and absorbed. " (from Treatise on Blood Syndromes. )
In summary, this function is mainly manifested in the following two aspects: First,the liver promotes secretion and excretion of the bile; and second, it maintains the normal ascending and descending functions of spleen-qi and stomach-qi The gall bladder is attached behind the right lobe of the liver, and stores the bile which has the active function of digesting the diet. The secretion and excretion of the bile rely on the surplus liver-qi.This is a refined liquid, which collects in the gall-bladder, formed by the liver's function of conducting and dispersing. When the liver functions normally, the functional activity of the qi is smooth, the gallbladder tract is unobstructed, and the bile can be discharged into the digestive tract to perform the function of aiding digestion. If this function is not performed, the secretion and excretion of the bile will be abnormal, and characterized by
jaundice, bitter taste in the mouth, vomiting of yellow fluid, distending pain in the lateral costal region, and diminished food intake. This shows that the secretion and excretion of the bile represents an important part of the function of the liver in dominating the conduction and dispersion.
In addition, the function of the liver in aiding digestion is manifested in the coordination of the ascending and descending functions of the spleen and stomach. Both the spleen and stomach are located in the middle-jiao. The spleen dominates ascending,while the stomach dominates descending, and only when the spleen cooperates harmoniously with the stomach can the digestive process be normal. This functioning of the spleen and stomach, however, is closely related not only to their physiological functions,but also the functional activity of the liver in dominating conduction and dispersion. As a result of this relationship, the normal functioning of the liver is an important factor that ensures the coordination of the spleen and stomach in ascending and descending, thus maintaining vigorous digestive functions. Failure of the liver in the conducting and dispersing functions not only influences secretion and excretion of the bile, but also causes disturbance of the spleen and stomach in the ascending and descending functions.If the spleen fails to send up the clear, there may be dizziness and vertigo in the upper,and diarrhea in the lower. If the stomach fails to send down the turbid, there may be hiccup, eructation, and belching in the upper, abdominal pain and distension in the middle,and constipation in the lower. The former condition is called "disharmony between the liver and spleen" and the latter, "the hyperactive liver-qi attacking the stomach. " Both
of them are generally termed "hyperactive liver-wood overacting on spleen-earth. " In treating these cases, therapeutic principles of "soothing the liver and regulating qi" and "harmonizing the spleen and stomach" should be used.
c. Promoting the qi, blood, and water flowing normally.
The qi, blood, and water are in a constantly flowing state, which is closely related to the physiological function of the liver, in addition to being related to the physiological activities of the heart, lung, spleen and kidney. For example, the normal flowing of the qi relies upon the function of the liver in dominating the conducting and dispersing of qi, which exerts a direct influence on the smooth flowing of qi. When this function of the liver is normal, the qi flows smoothly, and the ascending, descending,existing, and entering functions of qi will be normal. If the function is abnormal, the flow of qi is obstructed, leading to pathological changes of qi stagnation and distension and pain in the hypochondrium, chest, and breasts. In clinical treatment, the therapeutic principal of smoothing the liver and regulating qi often is adopted and has proven to be very effective.
The qi is the motive power in the circulation of blood. Its flow leads to the circulation of blood, while its stagnation causes blood stasis. The qi also relates to the function of the liver in conducting and dispersing qi, in addition to heart-qi's propelling force,lung-qi aiding the heart in promoting blood circulation, the function ot the spleen m commanding blood, etc. If these functions are normal, the blood circulation is unobstructed.If they are not, there may be syndromes characterized by blood stasis, and symptoms such as parching pain in the hypochondria and chest, mass and unstable gathering in the abdomen, irregular menstruation, etc.
The function of the liver plays an active role in promoting water metabolism and maintaining balance, which is manifested in its regulation of the functional activity of the triple-jiao, thus keeping water-passages unobstructed. A malfunction of liver-qi may cause disturbance of the flow of qi, and obstruct water passages of the triple-jiao. As a result, disorders in distribution and excretion of water-fluid occur, and the qi stagnation may lead to blood stasis. This in turn blocks the pathway of the vessels, and hinders the functional activities of qi, causing accumulation of water-dampness in certain regions the body, fluid-retention, and phlegm. Mixture of phlegm and qi turns into subcutaneous nodule and scrofula. If water-dampness accumulates in the chest and abdomen, hydrothorax and ascites may occur.
These three aspects 0f the liver in dominating the conducting and dispersing are closely inter-related. For example, the impairment of emotional activities may affect the secretion and excretion of the bile, and affect the digestive functions of the spleen and stomach. Disturbance of the bile in secretion and excretion also can cause dysfunction of the digestive system. Emotional disturbance may affect the circulation of the qi, blood, and water, which in turn will affect emotional activity. Thus, these three different aspects can not be considered in isolation. Only a comprehensive approach can be used in clinical practice to fully understand the function of the liver.
2) Storing Blood
In controlling the storage of blood, the liver is capable of retaining blood and regulating its volume in circulation. Blood is manufactured from the essential substances of drink and food, after their digestion and absorption by the spleen and stomach. After their formation, one part is moving in the whole body to supply nourishment for the viscera, tissues, and all organs, and the other part flows into the liver to be stored, so as to supply the demand for emergency situations.
Under general conditions, the blood volume of the viscera, tissues, and organs of the body is relatively constant. However, it must be able to adapt to such changes as the functional state of the body and the influence of the climatic changes. For example, when a person is at rest or asleep, the amount of blood needs to be relatively decreased, and the partial blood flows back to the liver to be stored. When the body is performing physical labor, the amount of blood needs to be increased, and the liver will expel the blood it has stored, to increase the volume of blood in circulation, thus satisfying the demand by the body's activities. Thus, Wang Bing said in explanation in the Plain Questions, "When the body moves about, the blood is distributed into the meridians, and when the body is at rest, and the blood flows back to the liver where it is stored. " Since the liver has the physiological function of retaining and regulating blood, there is a saying, "The liver is the sea of blood. " This is why the physiological activities of the various parts of the body are in close relation with the liver.
If the liver is diseased, its function of blood-storing will be abnormal, which not only leads to the disorder of the blood, but also affects the physiological functions of other viscera, tissues, and organs. Malfunctioning of the liver in storing blood is manifested in two pathological changes. First, the storage of blood may be insufficient, and the amount of blood distributed to various parts of the body decreased, thus making the liver unable to satisfy the body's physiological demand, causing numbness of limbs, scanty menstruation, and even amenorrhea. Secondly, the liver may fail to store the blood, causing hemorrhage syndromes, such symptoms as hematemesis, hemoptysis, epistaxis, metrorrhagia and metrostaxis, etc.
In addition,it is said in the visceral manifestation theory that "The liver stores the etherial soul. " The etherial soul is born of the vitality. However, both take the blood as their material basis. The heart dominates the blood vessels which house the mind, while the liver stores the blood which houses the etherial soul. If the blood-storing function of the liver is normal, the etherial soul can be housed . If liver-blood is insufficient, and heart-blood is impaired, the etherial soul cannot be housed, and there will be fright, dream-disturbed sleep, somnambulism, somniloquy, and hallucination.
As the mentioned above, the liver stores blood, and dominates the conducting and dispersing functions. Yet there is an inter-dependant and inter-restraining relationship between these two functions. In physiology, domination of the liver in the conducting and dispersing functions regulates the functional activity of the qi, and the flow of qi leads to the circulation of blood, which flows back to the liver to be stored. If liver-blood is ample, yin-blood of liver can control liver-yang to avoid an over-active state. In pathology, these two functions often affect each other. For example, failure of the liver in storing blood may lead to insufficiency of liver-blood, and the liver will lack the nourishment of blood. This leads to a disturbance of the liver's conducting and dispersing functions, characterized by irascibility, restlessness of mind, mental depression, dream-disturbed sleep, dull pain in the chest and lateral costal region, irregular menstruation, etc.
