Home > Basic Principles > Body's Organs from a TCM Perspective> The Five Yin organs(zang organs)
I. Liver | II. Heart | III Spleen | IV. Lungs | V. Kidneys

Physiological Functions of the Five Yin Organs


In western physiology, the liver is responsible for a number of important body functions, including the production and excretion of bile, which is used to break down fat and the detoxification of blood. However, according to TCM, the liver's functions are different. They include control of the central nervous system, the autonomic nervous system (the part of the nervous system over which a person does not have voluntary control), and the circulatory system. In addition, the liver is responsible for vision.
"The liver rules flowing and spreading."
In TCM, the liver promotes flowing and spreading movements. By stimulating flow, the liver adjusts and ensures the smooth movement of qi, blood and body fluids, and spreads these substances to the entire body. There are three functional aspects of the liver's "flowing and spreading" activity: regulating qi, regulating emotions and enhancing the digestive properties of the spleen.

Regulating qi movement

The activities of the organs and meridians are dependent on qi movement. The flow and spread of qi throughout the body are in turn dependent on the regulatory functions of the liver. If the liver is not functioning properly, qi flow is interrupted, which can lead to disharmony and imbalance. When this becomes marked,, disease and other health problems ensue.

Regulating emotions

The liver balances emotions. Normal emotional health depends on the harmony of qi and blood. When the liver keeps qi flowing smoothly, a relaxed internal, emotional environment is created. If liver disharmony results in stagnant liver qi, emotional disturbances like depression and anger can occur.

Enhancing the digestive power of spleen

The liver's flowing and spreading functions also adjust the digestive functions of spleen. If the liver is not functioning properly, the movement of spleen qi is not smooth. Consequently, the transformation and transportation of digested food will be affected, leading to abdominal pain, nausea, belching, diarrhea and other complications.

"The liver stores the blood."
The liver is also responsible for storing and regulating blood flow. When a person moves or exercises, the blood leaves the liver and goes to the part of body that needs it. The blood returns to the liver to be stored, when a person rests. If a person has insufficient blood available for storage in the liver, their eyes will not be adequately nourished and will become rough and dry. Dizziness can also occur.

"The liver opens into the eyes."
The eyes have a close relationship with the liver; because, they are connected to the liver meridian. The ability to see depends on the nourishment of the eyes from blood stored in the liver, and many liver disorders are reflected in the eyes. For example, insufficient liver blood can lead to blurred vision. "Dampness and heat" of the liver and gall bladder, a condition known in western medicine as jaundice, manifests as yellow eyes.

"The liver rules the tendons and is manifested in the nails."
The proper movement of tendons, which attach muscle to bone, is closely related to liver function. If the blood stored in the liver is insufficient and incapable of nourishing the tendons, symptoms like spasms, numbness of limbs and difficulty bending or stretching occur. Fingernail and toenail health is also dependent on the nourishment of blood from the liver. If the liver blood is sufficient, nails will appear pink and moist. If it is insufficient, the nails will become thin, brittle and pale.


In TCM, the functions of the heart are different from those of the anatomical heart, as it is understood in western medicine. The heart organ represents a group of physiological functions. In addition to regulating the cardiovascular system, it is responsible for maintaining the nervous system's functions.

"The heart rules the blood and blood vessels"
The heart is the functional unit for regulating blood flow. Blood is transported inside the blood vessels around the entire body when the heart pumps. The heart, blood and blood vessels are united by their common activities. In TCM, this functional relationship is known as the "ruling" of the heart.

Heart qi refers to the pumping actions of the heart. If heart qi is abundant and sufficient, the heart pumps at a normal pace, transporting blood smoothly inside the blood vessels, the pulse is regular and strong, and the face will look brilliant. As a result, the body is able to obtain from blood the nutrients needed to sustain life. On the other hand, if heart qi is deficient, blood cannot maintain an efficient flow in the blood vessels, and the pulse is weak. The individual looks pale, and the tongue also appears pale and white. Without healthy ruling of the heart, individuals will experience palpitations, chest discomfort and pain.

"The heart rules the spirit"
In TCM, the heart stores the "spirit". In general, the "spirit" refers to an individual's vitality, which is reflected in the eyes, speech, reactions and overall appearance. Specifically, the "spirit" refers to a person's mental, cognitive and intellectual abilities. The heart takes charge of mental activities by mastering other organs and their physiological functions. If the "spirit ruling" is good, the individual will be wise and have a clear and fast mind. If there is heart disharmony, signs like forgetfulness, poor self esteem, and slow thought processes or reactions occur.

"Sweat is the fluid of the heart."
Sweat comes from body fluids, which are an essential and integral part of blood. Blood is ruled by the heart and is the main fluid of this organ. Because sweat comes from the same origin as blood, in TCM over-sweating is considered an exploitation of qi and heart blood, leading to symptoms such as palpitations. As a result, people who sweat abnormally usually have a heart deficiency. If such sweating is spontaneous, the disharmony belongs to a deficiency of heart yang. If it takes place at night, the disharmony belongs to a deficiency of heart yin.

"The heart opens into the tongue. The heart's brilliance is manifested in the face."

In TCM, both the tongue and face are windows for the heart and blood. The heart "opens into the tongue" because they are connected. By observing the tongue and looking for the "heart's brilliance to be manifested in the face," a lot can be learned about how the heart is functioning. For example, if heart function is normal, individuals will have bright, healthy red cheeks and the tongue will appear pink. If there is blood stasis (where blood is not able to flow smoothly through the blood vessels), the face and tongue will appear purple. A healthy blood supply is also essential for providing nutrients for hair growth, because in TCM, hair is thought to be the "remains of blood." If hair growth is affected, it may indicate a problem with the heart and blood.
Click here to read more about the Heart Meridian.


In western physiology, the spleen is a large, vascular, lymphatic organ. It acts as a reservoir and filters the blood. It also plays a role in making blood early on in life. In TCM, the spleen does not perform these functions. It assists with digestion, blood coagulation and fluid metabolism in the body.

"The spleen rules transformation and transportation."
Since the spleen is the primary organ responsible for digestion, its main function is to transform food into essence used for qi and blood transformation. Once the ingested food and liquids get into the body, the spleen extracts a pure nutritive essence from them. This pure nutritive essence is used for the production of qi, blood and body fluids, which the spleen then transports throughout the body. Liquids extracted as pure nutritive essence are sent upwards to the lung for dissemination and redistribution. However, some will descend to the kidney and bladder to be excreted as urine.

If the transformation and transportation functions of the spleen are harmonious, there will be abundant nutritive essence for qi and blood, but if the spleen is in disharmony, its digestive powers will be affected. As a result, abdominal distention, pain, diarrhea or malaise occurs.
"The spleen rules ascending pure essence."
After transforming food into nutritive essence, the spleen sends it upwards to the heart and lungs where it is transformed into qi and blood for nourishment of the whole body. Food not transformed into nutritive essence becomes an impure substance. While the spleen ascends pure essence, the stomach, (the spleen's corresponding exterior organ), will descend the impure substances inside the digestive tract. By ascending the pure nutritive essence and descending the impure substances, a balance in the digestive system is created.

"The spleen governs the blood."
Not only does the spleen transform food essence, it also governs the movement of blood by keeping it flowing in its proper pathways in the blood vessels. When spleen qi is sufficient, there is adequate production of qi and blood, and blood is, therefore, kept inside the blood vessels. If the spleen's functions are in disharmony, the blood escapes from its normal pathways, leading to symptoms such as bloody vomit, blood in the stool, blood under the skin, blood in urine, or menorrhagia (excessive menstrual bleeding).

"The spleen rules the muscles and flesh. It opens into the mouth and its brilliance is manifested in the lips."

In TCM, the movements of the muscles and the four limbs depend on the power of the spleen. When spleen qi is sufficient, the limbs and muscles are healthy and strong because they are nourished by the blood and qi. If spleen qi is deficient, however, the muscles become weak and an individual may feel tired and have general malaise.

The lips and mouth are also affected by the spleen's health. If spleen function is harmonious, the mouth can distinguish the five tastes (sweet, salty, sour, bitter and pungent (spicy)), and the lips appear red and moist. If the spleen is weak, the mouth cannot distinguish the different tastes and the lips will be pale.
Click here to read more about the Spleen Meridian.


In western physiology, the lungs are responsible for air exchange. In addition to performing respiration in TCM, the lungs' regulate fluid metabolism, blood circulation, the autonomic nervous system and the immune system.

"The lungs rule qi and administer respiration. "
The lungs are where qi exchange and regulation occurs. During inhalation, the lungs take in natural air qi (one type of qi referring to the atmospheric air), propelling it downward where it meets other types of qi. The different types of qi combine to produce normal qi (qi present in the body). During exhalation, the lung expels the "impure" air not useful to the body. If the lungs are healthy, qi will enter the body smoothly and respiration will be even and regular. If there is lung disharmony, respiration is weakened and normal qi production is affected, leading to qi deficiency.

"The lungs direct movement in a disseminating, descending and liquefying manner."
The lungs disseminate substances in an ascending and outward direction. For example, impure air is expelled in this manner, and body fluids and food nutritive essence are directed towards the skin and hair. By regulating sweat secretion, the lungs disseminate protective qi (qi mainly responsible for immunity) to the skin and the pores.

The lungs also demonstrate descending and liquefying properties. They take in natural air qi during respiration and liquefy the fluids in the airway. The lungs then descend these substances downwards along with food essence transformed by the spleen. The descending function is necessary to maintain a normal respiratory tract.

The disseminating, descending and liquefying properties of the lungs are essential for good health. If disharmony occurs, individuals may suffer from coughing, wheezing, chest discomfort, abnormal sweating or congestion from phlegm.

"The lungs move and adjust the water channels"
The lungs are responsible for the transformation and movement of water in the body. They move water in the same directions as qi. The lungs' disseminating properties enable water vapor to ascend and scatter to the skin pores. This is the process of normal sweating. The lungs also liquefy and cause water vapor to descend to the kidneys, where the liquefied waste is excreted as urine.

"The lungs collect blood vessels and rule regulation."
As mentioned before, the lungs rule qi. By regulating qi movement, which is necessary for blood circulation to occur, the lungs intercept all blood and blood vessels. After qi exchange occurs during breathing, the qi moves the blood throughout the body. Qi movement also regulates the distribution of body fluids. Since qi is essential for all physiological functions in the body, the lungs' ability to 'rule and regulate qi" is an important function.

"The lungs open into the nose and their brilliance is manifested in the body hair. The lungs also connect to the throat."
The skin and body hair share a close relationship with the lungs. Together with the sweat glands, they are often referred to as the "exterior" of the body in TCM. The lungs are the interior organs that rule this exterior. By controlling the skin, sweat glands and body hair, the lungs regulate the sweating process. In addition, they maintain healthy movement and dissemination of protective qi over the skin. Protective qi is important for guarding the body against "illness evils" (factors causing illness including wind, fire, dampness, dryness, cold and summer heat). If these particular lung functions are weakened, too much spontaneous sweating occurs, and the protective qi will become weak as well. As a result, the body will have lower resistance to illness and may easily get colds, influenza, or other respiratory problems.

The nose is considered the opening of the lungs and the exit for qi in the body. If lung dysfunction occurs, the nose is affected. For example, disordered flow of lung qi leads to a watery nasal discharge, congestion, a loss of sense of smell and sneezing. The throat and vocal cords are also connected to the lungs. Sometimes lung deficiency produces a coarse or low voice.
Click here to read more about the Lung Meridian.


In western physiology, the kidneys are a vital excretory organ whose main function is to create urine to help the body get rid of toxins and unwanted water. TCM practitioners view the kidneys as a very important organ that not only regulates the urinary system but also exercises control over the reproductive, endocrine and nervous systems.

"The kidneys store Jing"
In TCM, Jing is an essential substance, closely associated with life. It is the substance needed for reproduction, growth development and maturation. The kidneys are the organs responsible for human development, because they store Jing. For example, conception is made possible by the power of Jing, growth to maturity is the blossoming of Jing, and aging reflects the weakening of Jing. As time passes, Jing decreases, causing both vitality and kidney qi to decline. This decline is the normal aging process.
"The kidneys rule water."
The kidneys rule water by regulating its distribution and excretion, traditionally described as the vaporizing power of the kidneys. The kidneys can differentiate between clean water, which is recycled and used by the body, from turbid water that is turned into urine. The separation of these two is the vaporization process.

The kidneys play an important role in water movement and balance of the whole body. Fluids and food are received by the stomach where separation begins. The unusable portions of food and fluid are sent to the intestines as waste where pure fluids (mainly water) are extracted from them. The pure fluids go to the spleen, which then sends them in a vaporized state upward to the lungs. The lungs circulate and disseminate the clear part of the fluids throughout the body. Whatever has become impure through use is liquefied by the lungs and sent downward to the kidneys. In the kidneys, the impure fluids are further separated into "clean" and "turbid" parts. The clean part is vaporized into a mist and sent upwards to the lungs, where it rejoins the cycle. The final impure portion goes to the bladder, where it is stored and finally excreted as urine.

"The kidneys rule the grasping of qi."
Although respiratory functions mainly depend on the lungs, deep and normal breathing is controlled by the "grasping" function of the kidneys. By grasping qi, the kidneys enable the "natural air qi" of the lungs to penetrate deeply during the inhalation process. If there is kidney disharmony, respiratory problems such as shallow breathing or wheezing on exertion can occur. Some types of asthma are related to disordered grasping of qi by the kidneys. "The kidneys rule the bones and produce bone marrow. The kidneys manifest in the head hair."
Stored in the kidneys, Jing is the substance responsible for producing bone marrow, which in turn, creates and supports bone growth. Therefore, bone development and repair depends on the nourishment of kidney Jing. Deficiency of Jing in children can lead to soft bones or incomplete closure of the skull bones. Teeth are made up of bone so dental problems can also indicate a kidney deficiency.

Head hair depends on blood for its nourishment. The kidneys play a role in transforming stored Jing into blood. If Jing and blood are abundant, the hair will appear bright, shiny and healthy. On the other hand, hair loss or other hair disorders can indicate a kidney deficiency or blood deficiency.

"The kidneys open into the ears and genital organs."

Good hearing comes with abundant kidney Jing, while a deficiency causes hearing problems like deafness or ringing in the ears (tinnitus). Genital and urinary tract disorders such as urinary frequency or dripping urine (incontinence) are also signs of kidney disharmony.
Click here to read more about the Kidney Meridian.