The Liver's main function in Chinese Medicine is to ensure the smooth flow of Qi throughout the body and to store Blood. It also fulfills a strong role in our emotional well-being by housing the Ethereal Soul (Hun-魂) and being affected by anger.
The Liver is often referred as the body's 'general' in Chinese Medicine because it is in charge of deciding on countermeasures if the external environment changes. For instance, an Organ might be 'under attack' by an external pathogen and the Liver will decide to send more Qi their way. As such it has an important role in the Chinese Medicine version of the immune system.
Chinese Medicine believes that sometimes (when a person lies down for instance) Blood partially stops moving around the body and needs to be stored somewhere. The Liver fulfills that storage role and releases the Blood when it's needed again (when someone gets up, exercises, etc.).
The Liver 'opens' into the eyes, 'governs' the sinews and is 'reflected' in the nails. This means that a Chinese Medicine doctor has many clues to understand if a patient has a Liver Deficiency. Such patients may for instance have a jaundiced color in their eyes. Or they would have nails that are too thin and pale. Or, for the sinews part, they'd have difficulty bending or stretching.
The Liver stores Blood and regulates its smooth flow, just like a 'General' deploys his forces and gathers them back to rest. If this Liver function is normal, the skin and muscles will be well nourished by Blood at the appropriate time (e.g. during exercise) and be able to resist attacks of Exterior pathogenic factors. If this is impaired due to lacking of Blood, it leads to improper nourishment by Blood. This is often manifested in blurred vision and fatigue.
This function also directly affects our resistance to invading External factors, as proper distribution of Blood to the skin and muscles aids the body's ability to resist attacks by Exterior pathogenic factors. If impaired, the necessary nourishment of skin and muscles fails to occur, and the body becomes more susceptible to External Invasions.
The storage and regulation of the smooth flow of Blood directly affects women's menstruation. If this Liver function works properly, menstruation is normal. If Liver Blood is Deficient, there will be absence of period or scanty periods. If Liver Blood is in Excess or Hot, the periods may be heavy. If Liver Blood is Stagnant, the periods will be painful. This function is extremely important in women's health. Most gynecological problems are due to a malfunction of Liver Qi or Liver Blood.
Just as a tree spreads out freely in all directions, the Liver ensures the smooth flow of Qi throughout the body, in all Organs and in all directions. The impairment of this function is one of the most common patterns seen in practice. For instance it has a deep influence on our emotional state: if Liver Qi is obstructed, we may experience emotional swings, repressed anger and irritability.
A smooth flow of Liver Qi also assists the Stomach and the Spleen's digestive functions. If Liver Qi flows smoothly, the Stomach can ripen and rot food and Stomach Qi can descend. If imbalanced, Stomach Qi may ascend rather than descend, causing belching, nausea and vomiting, and the Spleen Qi may descend rather than ascend, resulting in chronic diarrhea and abdominal distension.
Finally, the smooth flow of Liver Qi affects the flow of bile. If Liver Qi flows smoothly, bile is secreted properly and digestion is good. If Liver Qi is Stagnant, one may experience a bitter taste in the mouth, belching, an inability to digest fats or jaundice.
The state of our sinews (including tendons, cartilages and ligaments of the limbs) affects our capacity for movement and physical activities. Liver Blood moistens and nourishes our sinews. This ensures smooth movement of the joints and good muscle action. If Liver Blood is Deficient, malnutrition of the sinews results, causing stiffness, rigidity, joint pain, spasms or tremors of the hands and feet.
Our finger and toe nails are the 'excretion' of the sinews, and, as such, they are under the direct influence of the Liver. If there is Damp, Heat or Stagnation in the Liver, the nails are yellowish with ridges. If there is Deficiency of Liver Blood, the nails are brittle, soft, thin, pale, dry and break easily. When Liver Blood is plentiful, the nails are hard, pink and moist.
The eyes are the sense Organ connected to the Liver. Strong Liver Blood moistens and nourishes the eyes to provide good vision. Inversely if Liver Blood is Deficient, then dryness, blurred vision, night blindness, myopia, color blindness and 'floaters' in the eyes may result. If there is Heat in the Liver, the eyes may be bloodshot, red or swollen and feel painful or burning. If there is Internal Liver Wind, the eyeballs may turn upwards and move involuntarily. In addition, as tears are the Body Fluids of the eyes, Excessive tearing or a Deficiency of tears both show an imbalance of the Liver.
While the Liver is the main Organ connected with the eyes, others help determine their state. In particular, the Essence of the Kidneys nourishes the eyes, so that many chronic eye diseases are related to the decline of Kidney Essence. The Heart plays an important role too: it houses Shen, or Spirit, which is reflected in the brightness of the eyes and Heart Fire can cause pain and redness of the eye.
The Ethereal Soul, called Hun (魂) in Chinese, is Yang in nature (as opposed to the Corporeal Soul which is Yin) and at death survives the body. It is said to influence our capacity to plan our life and find a sense of direction by affecting our dreams, visions, purpose, projects, inspiration and creativity.
Hun is rooted and nourished by Liver Yin and Blood. It is most active at night during sleep and helps determine our quality of sleep. If Liver Blood or Liver Yin is weak, it is said that the Ethereal Soul is not 'rooted' in Blood and Yin, so much so that it may even leave the body temporarily at night. In that case one may experience insomnia, a dream-disturbed sleep and a feeling of floating before sleep. Similarly we can experience a lack of direction in life and an inability to plan or envision what to do.
'Anger' should here be understood in a broad sense: it includes frustration, resentment, repressed anger and rage. As with any other emotion, the relationship between an emotion and the Organ is mutual: a state of anger causes a Liver pathology and, vice versa, a Liver pathology may cause the person to become irritable.
For instance anger, especially when it is repressed, causes Stagnation of Liver Qi. And vice-versa, a stagnation of Liver Qi in someone who is not previously angry will lead to a feeling of lingering anger.
This refers to the fact that a healthy Liver function can confer on a person resoluteness, a strong spirit and lots of courage. These mental attributes depend on the state of Liver Qi and Gallbladder Qi. In fact, the strongest manifestation of Liver Qi Deficiency (a quite unusual pattern) is on someone's character: they will be timide, lack any resolve, lack courage and will be highly indecisive.
The Liver is said to influence us on the capacity to plan our life smoothly and wisely. In disease, a Liver disharmony can manifest with an inability to plan our life and a lack of direction. This function is particularly a function of the Ethereal Soul.
Indeed, the Liver regulates the volume of Blood needed by the body according to physical activities. During movement and exercise, the Blood flows to the muscles and sinews; at rest, it flows back to the Liver.
The smooth flow of Liver Qi is another manifestation of the regulating and balancing function of the Liver as the smooth flow of its Qi regulates all movements of Qi in every part of the body.
Finally, the regulating and balancing function of the Liver has an important emotional aspect. The Liver, and particularly the Ethereal Soul (housed in the Liver), is responsible for a balanced emotional life.
Internal Wind can be likened to the nervous system. It is always related to the Liver as it typically comes with symptoms of convulsions and tremors which are explained in Chinese medicine as "shaking" of the sinews, , which are an extension of the Liver.
Internal Wind can be stirred up by climatic Wind, which affects the Liver and its regulating and harmonizing functions. It is not uncommon for Liver-related symptoms (like headaches and stiffness of the neck) to appear after being exposed for a while to windy weather.
Equally, Wind can be agitated Internally in the Liver from three factors: extreme Heat, Liver Yang Rising and Liver Blood Deficiency. This typically happens to older people and manifests in symptoms of tremors, facial tics and convulsions or, in the most severe cases, paralysis.
Although physiologically situated on the right side, the Liver is related to the left side of the body. This is because in the original Five Element System, when the Spleen was placed in the middle of the other Elements, the Liver was placed on the left side of the cycle. Thus, any left-sided symptoms, such as pains on the left side of the head, abdomen and tongue, especially reflect the Liver, while the right side reflects the Lungs.