The Six Fu Organs: What Are the Roles of the Gallbladder, Stomach, Small Intestine, and Large Intestine?

The Six Fu organs refer to the gallbladder, stomach, small intestine, large intestine, bladder, and San Jiao (Triple Burner). Among them, the stomach, small intestine, large intestine, and bladder are known as the “transformation Fu” because they are responsible for the conduction and transformation of substances.

The physiological function of the Six Fu organs: The common physiological function of the Six Fu organs is to “transform substances”, which means they receive, store, and transform food and fluids. When food enters the mouth, it travels down the esophagus to the stomach, where it is processed and then passed to the small intestine. In the small intestine, the clear (essence and fluids) is absorbed by the spleen and transported to the lungs, where it is distributed throughout the body to meet the needs of the organs and meridians for life activities; the turbid (waste) is sent to the large intestine, where it is formed into feces and expelled from the body; waste fluids are transformed by the kidneys into urine, which is then excreted through the bladder.

The physiological characteristics of the Six Fu organs: The common physiological characteristics of the Six Fu organs are “draining but not storing” and “solid but not full”. Because they receive and transform food and fluids, and excrete waste, it is said: “The Six Fu organs transform substances but do not store them, hence they are solid but cannot be full. This is because when food enters, the stomach is full and the intestines are empty. When food descends, the intestines are full and the stomach is empty.” (from Su Wen: On the Distinction of the Five Organs) Each Fu must timely empty its contents to maintain smoothness and coordinated function, hence the saying, “The Six Fu organs function through smoothness and descend in order.”

When the Qi of the Six Fu organs is smooth, they transform but do not store, hence it is said, “The Six Fu organs function through smoothness”; when the Qi of the Six Fu organs descends, they conduct and transform substances, draining but not storing, hence it is said, “The Six Fu organs descend in order.” The emphasis on “smooth” and “descend” is crucial; if either is excessive or insufficient, it indicates a pathological condition.

The Six Fu Organs: What Are the Roles of the Gallbladder, Stomach, Small Intestine, and Large Intestine?

“Gallbladder: Known by Several Names, the Official of Central Justice”

The gallbladder is the foremost of the Six Fu organs and belongs to the extraordinary organs (the reasons will be explained later). It is shaped like a pouch, resembling a gourd, and is attached to the liver’s small lobe. The gallbladder is yang and belongs to wood, corresponding with the liver. It stores and excretes bile and is responsible for decision-making.

The Six Fu Organs: What Are the Roles of the Gallbladder, Stomach, Small Intestine, and Large Intestine?

The gallbladder is a hollow organ that stores bile, which is a pure, clear, bitter, yellow-green fluid, hence it is referred to as the “central essence Fu” and the “central clear Fu”.

The gallbladder governs decision-making, thus in the Huangdi Neijing, it is also given an official title—”the Official of Central Justice”. The Su Wen: On the Secret of Ling Lan states: “The gallbladder is the Official of Central Justice, from which decisions are made.”

The anatomical structure of the gallbladder is similar to that of other Fu organs, hence it is one of the Six Fu. However, due to its physiological characteristic of storing essence, it also belongs to one of the extraordinary organs.

1. Storage and Excretion of Bile

Bile, also known as “essence fluid” or “clear fluid”, originates from the liver. “The residual Qi of the liver leaks into the gallbladder, where it accumulates and forms essence.” Bile is formed and secreted by the liver, then stored and concentrated in the gallbladder, and through the gallbladder’s excretory function, it enters the small intestine. Bile “is formed by the transformation of the liver’s wood Qi; after eating, the small intestine fills, pressing the gallbladder to release its fluid into the small intestine to dissolve food and facilitate the passage of waste. If bile is insufficient, the essence is not differentiated, leading to pale and clean stools without yellow color.” The liver and gallbladder both belong to the wood element, one yin and one yang, complementing each other. “The gallbladder is the Fu of the liver, belonging to wood, governing the elevation of clear and the descent of turbid, facilitating the middle earth.” Thus, the gallbladder also has the function of excretion, but its excretion relies on the liver’s Qi to perform its duties.

The bile stored in the gallbladder is excreted due to the liver’s excretory function, entering the intestines to promote the digestion of food. If the liver and gallbladder functions are abnormal, the secretion and excretion of bile are obstructed, which can affect the digestive function of the spleen and stomach, leading to symptoms such as loss of appetite, abdominal distension, and diarrhea. If damp-heat accumulates in the liver and gallbladder, causing the liver to lose its excretory function, bile overflows and saturates the skin, resulting in jaundice, characterized by yellowing of the eyes, skin, and urine. The gallbladder Qi descends in order; if gallbladder Qi is obstructed, Qi may rebel upwards, leading to symptoms such as bitter taste in the mouth and vomiting of yellow-green bitter fluid.

2. Governing Decision-Making

The gallbladder governs decision-making, referring to its role in the mental and cognitive processes of judgment and decision-making. The gallbladder’s role in decision-making is crucial for defending against and eliminating the adverse effects of certain mental stimuli (such as great fear) to maintain and control the normal flow of Qi and blood, ensuring the coordination of the organs. Thus, it is said: “The gallbladder is the Official of Central Justice, from which decisions are made.” Mental and psychological activities are related to the gallbladder’s decision-making function; the gallbladder assists the liver’s excretion to regulate emotions. When the liver and gallbladder work in harmony, emotions are stable. A person with strong gallbladder Qi is less affected by intense mental stimuli and recovers quickly. Therefore, it is said that strong gallbladder Qi prevents evil influences. Conversely, a person with weak gallbladder Qi is more susceptible to adverse effects from mental stimuli, leading to conditions such as timidity, fearfulness, insomnia, and vivid dreams, which can often be treated by addressing the gallbladder. Thus, it is said: “The gallbladder is attached to the liver, complementing each other; even if the liver Qi is strong, it cannot function without the gallbladder. When the liver and gallbladder work together, courage is achieved.”

The gallbladder’s decision-making function is also significant in preventing adverse effects from emotional stimuli on the body. Clinically, we often see patients who say they are particularly timid, startled by others’ words, and experience irritability and poor sleep, with a yellow greasy tongue coating, indicating gallbladder deficiency with phlegm-heat. Treatment with modified Huanglian Wendan Decoction has shown excellent results. Professor Ma Shuran from Beijing University of Chinese Medicine once shared a case:

A Korean student presented with a dark complexion, a yellow greasy tongue with black coating, and complained of frequent timidity and fear. He was afraid to sleep before 2 AM, as he would wake up at 2 AM regardless of when he fell asleep, seeing a ghost in black clothing on the balcony. According to the theory of the twelve meridians, from 11 PM to 1 AM is the time of the gallbladder meridian, and from 1 AM to 3 AM is the time of the liver meridian. Therefore, waking during this time indicates a disturbance in the functions of the liver and gallbladder meridians. A modified Huanglian Wendan Decoction was prescribed, and after a week, the hallucinations disappeared, and he was able to sleep peacefully.

“Stomach: The Granary Official”

The stomach is the organ in the abdominal cavity that holds food. It is responsible for receiving and digesting food and is known as the granary of food essence and the sea of Qi and blood. The stomach functions in smooth descent, complementing the spleen, and they are often referred to as the foundation of postnatal life. The stomach and spleen reside in the middle earth, but the stomach is dry and yang, while the spleen is damp and yin.

1. The Stomach Governs the Reception of Food

Reception refers to the act of accepting and containing. The stomach’s role in reception means it accepts and contains food. When food enters the mouth, it travels down the esophagus and is temporarily stored in the stomach; this process is called reception, hence the stomach is referred to as the “granary official”, “great granary”, and “sea of food essence”. “What a person receives as Qi is food; what is poured into is the stomach. The stomach is the sea of food essence.”

“The stomach governs reception, thus it is the granary of the five grains.” The physiological activities of the body and the transformation of Qi, blood, and fluids depend on the nutrition from food, which is why the stomach is also called the sea of food essence and Qi. The stomach’s function of reception is the foundation of its function of digestion, and if the stomach is diseased, its reception function will be affected, leading to symptoms such as poor appetite, food aversion, and abdominal distension.

The strength of the stomach’s reception function depends on the vigor of the stomach Qi, which reflects the ability to eat or not. If one can eat, the stomach’s reception function is strong; if one cannot eat, the stomach’s reception function is weak.

2. The Stomach Governs the Digestion of Food

Digestion refers to the initial breakdown of food in the stomach, forming chyme. The stomach’s role in digestion means it digests food into chyme. “The middle jiao is in the stomach, neither rising nor descending, governing the digestion of food.” The stomach receives food from the mouth and retains it for a short time to undergo initial digestion, relying on the stomach’s digestive function to transform food into chyme. After initial digestion, the essence of the food is transported by the spleen to nourish the body, while undigested chyme descends into the small intestine, continuously renewing the digestive process of the stomach. If the stomach’s digestive function is weak, symptoms such as stomach pain and belching of foul-smelling food may occur.

The stomach’s functions of reception and digestion must be coordinated with the spleen’s transport function to be successful. Thus, it is said: “The spleen is the earth; the earth assists the stomach Qi in digesting food. If the spleen Qi does not circulate, the food in the stomach cannot be digested.” The spleen and stomach work closely together: “The stomach governs reception, and the spleen governs transport; one receives and one transports,” allowing food to be transformed into essence, generating Qi and blood to nourish the entire body. Therefore, the spleen and stomach are referred to as the foundation of postnatal life and the source of Qi and blood transformation. The digestion and absorption of food are crucial for life and health. Hence, it is said: “Humans rely on food; without food, one dies.”

The digestion and absorption of food is a complex physiological process that requires not only the stomach’s reception and digestion functions but also the spleen’s transport function and the small intestine’s separation of clear and turbid substances. Traditional Chinese medicine often summarizes the normal digestive and absorption functions of the body as “stomach Qi”. It is believed that “the stomach Qi is fundamental to life”; even stating, “With stomach Qi, there is life; without stomach Qi, there is death,” emphasizes the importance of stomach Qi in maintaining life activities. For example, the Su Wen: On the Discussion of Normal Qi states: “The normal Qi of a healthy person is derived from the stomach; the stomach is the normal Qi of a healthy person. If a person lacks stomach Qi, it is called ‘reversal’, and reversal leads to death.” In clinical practice, diagnosing and treating diseases often involves “observing stomach Qi” and “protecting stomach Qi” as important principles. As stated in the Jingyue Quanshu: On Various Symptoms of the Spleen and Stomach, “To diagnose a disease, one must first observe stomach Qi; to treat a disease, one must always consider stomach Qi. If stomach Qi is intact, there is no need to worry about other issues.” This illustrates the importance of stomach Qi for the human body.

3. The Stomach Governs Smooth Descent, Leading to Harmony

Smooth descent refers to the physiological characteristic of the stomach to facilitate the downward movement of food. The stomach’s function of smooth descent means it has the physiological property of facilitating the downward movement of food. After food is received and digested in the stomach and retained for a certain period, it must descend into the small intestine, where clear and turbid substances are separated. The clear is transported by the spleen to nourish the body, while the turbid continues to descend into the large intestine, forming waste to be expelled from the body. Therefore, the stomach’s function of smooth descent is related to the entire process of digestion, absorption, and excretion of food. Additionally, the stomach Qi governs descent, while the spleen Qi governs elevation; these functions are complementary. The stomach Qi descends, allowing food to timely move into the small intestine for separation of clear and turbid; the spleen Qi ascends, timely distributing the essence of food throughout the body. The orderly ascent and descent of the spleen and stomach work together to complete the digestion and absorption of food.

If the stomach’s function of smooth descent is abnormal, it is referred to as the stomach losing harmony and descent, or stomach Qi rebelling upwards. If the stomach loses harmony and descent, food may remain in the stomach, affecting its reception and digestion, leading to symptoms such as abdominal distension or pain, bad breath, and constipation. This is due to food stagnation; if it does not flow, it causes pain, and prolonged food stagnation can lead to heat symptoms. Clinically, treatments such as modified Baohe Pills, Mu Xiang Binglang Pills, and Zhi Shi Da Zhi Pills are often used to regulate digestion and clear heat. If stomach Qi does not descend but instead rebels upwards, symptoms such as nausea, vomiting, hiccups, and warm Qi may occur. Hiccups refer to the upward rush of stomach Qi, causing spasms of the diaphragm, resulting in a rapid and short sound. Belching refers to gas rising from the stomach to the throat, producing a long and soft sound, which is the result of food stagnation rising to the throat with a sour and rotten odor. Whether it is warm Qi, hiccups, or nausea and vomiting, they all indicate stomach Qi rebelling upwards. Traditional Chinese medicine often employs methods to harmonize the stomach and descend rebellious Qi, commonly using tangerine peel and bamboo shavings decoction or Xuanfu flower and Heshou stone decoction for treatment.

“Small Intestine: The Official of Reception and Transformation”

The small intestine is located in the abdomen, connecting to the pylorus above and the large intestine below, including the ileum, jejunum, and duodenum. It is responsible for receiving, transforming substances, and separating clear from turbid. It is related to the heart, belongs to fire, and is yang.

1. The Small Intestine Governs Reception and Transformation

The small intestine’s role in reception and transformation refers to its function of receiving and transforming food. Reception means accepting and containing, while transformation refers to the digestion and conversion of food. The small intestine’s function of reception and transformation is reflected in two aspects: first, the small intestine receives the food that has undergone initial digestion in the stomach, acting as a container; second, the food must remain in the small intestine for a certain period for further digestion and absorption, transforming food into nutrients that can be utilized by the body. The essence is absorbed, while the waste is sent to the large intestine, which is the “transformation” function. In pathology, if the small intestine’s reception function is disordered, the transformation ceases, leading to stagnation and pain, manifesting as abdominal pain. If the transformation function is abnormal, it can lead to digestive and absorption disorders, resulting in symptoms such as abdominal distension, diarrhea, and loose stools.

2. The Small Intestine Governs Separation of Clear and Turbid

Secretion refers to the process of separating. Separation means distinguishing. Clear refers to the essence, while turbid refers to metabolic waste. The separation of clear and turbid means that the small intestine, while further digesting the food received from the stomach, also distinguishes between the essence and the waste. The essence, including the fluids generated from beverages and the nutrients from food, is absorbed and then transported by the spleen to the heart and lungs, nourishing the entire body. The turbid is sent to the large intestine through the ileocecal valve to form feces, which are expelled through the anus. The remaining water is transformed by the kidneys and enters the bladder, forming urine, which is expelled through the urethra. “The bladder and kidneys are interrelated, both governing water; water enters the small intestine, descends to the bladder, and is excreted as urine and feces.” Because the small intestine participates in the body’s water metabolism during the separation of clear and turbid, it is said that “the small intestine governs fluids”. Therefore, Zhang Jingyue stated: “The small intestine is located below the stomach, receiving the food essence and separating clear from turbid; water and fluids are thus absorbed, while waste is expelled. The spleen Qi rises, and the small intestine Qi descends, hence the transformation occurs here.”

When the small intestine’s function of separating clear and turbid is normal, fluids and waste each follow their path, and urination and defecation are normal. If the small intestine’s function is disordered, clear and turbid are not distinguished, leading to mixed water and waste, resulting in symptoms such as diarrhea. Since “the small intestine governs fluids”, the small intestine’s function of separating clear and turbid not only affects bowel movements but also impacts urination, manifesting as reduced urination. Therefore, in the early stages of diarrhea, the method of “promoting urination to solidify bowel movements” is often used for treatment.

The small intestine’s functions of reception and transformation, as well as separation of clear and turbid, are the most critical stages in the entire digestive process. During this process, chyme is further digested, transforming food into clear (essence containing fluids) and turbid (waste containing fluids) components. The former relies on the spleen’s transport to be absorbed, while the latter descends into the large intestine. The small intestine’s digestive and absorption functions are often categorized under the spleen and stomach’s reception and transport functions in the theory of organ systems. The spleen and stomach’s reception and transport functions encompass all aspects of modern digestive physiology and part of nutritional physiology. Thus, it is said: “Humans receive food; the spleen transforms the essence upwards, while the small intestine transforms waste downwards into the large intestine.” The phrase “the spleen transforms the essence upwards” refers to the small intestine’s function of digestion and absorption. Therefore, conditions of poor digestion and absorption in the small intestine fall under the category of spleen dysfunction, and treatment is often based on the spleen and stomach.

“Large Intestine: The Official of Conduction”

The large intestine is located in the abdomen, connecting to the small intestine at the ileocecal junction and ending at the anus, including the colon and rectum. It is responsible for conducting waste and absorbing fluids.

1. Conducting Waste

The large intestine’s conduction function refers to its role in receiving the waste from the small intestine, forming feces, and expelling them through the anus. The large intestine receives the waste from the small intestine, absorbs the remaining water and nutrients, forming feces to be expelled, representing the final stage of the digestive process, hence it is called the “conducting Fu” or “conducting official”. Therefore, the primary function of the large intestine is to conduct waste and excrete feces. The conduction function of the large intestine is closely related to the stomach’s smooth descent, the spleen’s transport, the lung’s descending function, and the kidney’s storage.

If the large intestine is diseased, conduction becomes abnormal, primarily manifesting as changes in the quality and quantity of feces and alterations in bowel habits. If the large intestine’s conduction is abnormal, it can lead to constipation or diarrhea. If damp-heat accumulates in the large intestine, causing Qi stagnation, symptoms such as abdominal pain, urgency, and dysentery with pus and blood may occur.

2. Absorbing Fluids

After the large intestine receives the waste and remaining fluids from the small intestine, it reabsorbs some of the water, allowing the waste to form feces for excretion. The large intestine’s function of reabsorbing fluids is involved in regulating the body’s water metabolism, referred to as “the large intestine governs fluids”. Therefore, the large intestine’s pathology is often related to fluid metabolism. For instance, if the large intestine is deficient and cold, it may struggle to absorb fluids, leading to mixed waste and symptoms such as borborygmi, abdominal pain, and diarrhea. If the large intestine is hot and dry, it may fail to retain moisture, leading to constipation.

Why is it said that “the small intestine governs fluids, and the large intestine governs moisture”? First, we need to clarify how traditional Chinese medicine understands the concepts of “moisture” and “fluid” from a morphological perspective. Traditional Chinese medicine believes that moisture is relatively clear and thin, containing fewer nutrients, while fluid is thicker and richer in nutrients. In the nutrients absorbed by the large and small intestines, the small intestine is the primary site for absorbing essence, hence the nutrients absorbed by the small intestine are more abundant, making the fluid it absorbs thicker, thus it is said that the small intestine governs fluids. Conversely, the large intestine conducts waste, and the fluids it absorbs contain fewer nutrients, making them thinner, hence it is said that the large intestine governs moisture.

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