Gallbladder

The gallbladder is attached to the liver with which it is externally-internally related. Its main function is to store bile and continuously excrete it to the intestines to aid digestion. When the function of the gallbladder is normal, its qi descends. Since the bile is bitter in taste and yellow in colour, upward perversion of gallbladder qi may give rise to a bitter taste in the mouth, vomiting of bitter fluid, and failure to aid the stomach and spleen in digestion, resulting in abdominal distention and loose stools.

Since the function of the gallbladder is closely related to the liver's function of maintaining the free flow of qi, it is said that the liver and gallbladder together have the function of maintaining the free flow of qi. Similarly, the relation of the liver to emotional changes is shared by the gallbladder, and this is often taken into account in the clinic when treating symptoms such as fear and palpitations, insomnia and dream-disturbed sleep.

Although the gallbladder is one of the six fu organs, unlike the other five it stores bile and does not receive water or food. For this reason it is also classified as one of the "extraordinary fu organs."

Stomach

The stomach is located in the epigastrium. It connects with the oesophagus above, and with the small intestine below. Its upper outlet is the cardia, called Shangwan, and its lower outlet is the pylorus known as Xiawan. Between Shangwan and Xiawan is Zhongwan. These three areas together make up the epigastrium. The Stomach Meridian is connected with the spleen with which it is externally-internally related.

The main function of the stomach is to receive and decompose food. Food enters the mouth, passes through the oesophagus, and is received by the stomach where it is decomposed and transmitted down to the small intestine. Its essential substances are transported and transformed by the spleen to supply the whole body. The stomach and spleen, therefore, act in conjunction and are the main organs carrying out the functions of digestion and absorption. Together they are known as the "acquired foundation."

When the function of the stomach is normal, its qi descends. If the descending function is disturbed, there will be lack of appetite, distending pain in the epigastrium, nausea and vomiting.

Small Intestine

The small intestine is located in the abdomen. Its upper end connects with the stomach, and its lower end with the large intestine. The Small Intestine Meridian communicates with the heart with which it is externally-internally related. Its main functions are reception and digestion. It receives and further digests the food from the stomach, separates the clear from the turbid, and absorbs essential substance and part of the water from the food, transmitting the residue of the food to the large intestine, and of the water to the bladder.

Since the small intestine has the function of separating the clear from the turbid, dysfunction may not only influence digestion, but also give rise to an abnormal bowel movement and disturbance of urination.

Large Intestine

The large intestine is located in the abdomen. Its upper end connects with the small intestine via the ileocecum, and its lower end is the anus. The Large Intestine Meridian communicates with the lung with which it is externally-internally related. The main function of the large intestine is to receive the waste material sent down from the small intestine, absorb its fluid content, and form the remainder into faeces to be excreted. Pathological changes of the large intestine will lead to dysfunction in this transportation function, resulting in loose stools or constipation.

Bladder

The bladder is located in the lower abdomen. Its meridian connects with the kidney with which it is extemally-internally related. The main function of the bladder is the temporary storage of urine, which is discharged from the body through qi activity when a sufficient quantity has been accumulated. This function of the bladder is performed with the assistance of the kidney qi. Disease of the bladder will lead to symptoms such as anuria, urgency of micturition and dysuria. Failure of the bladder to control urine may lead to frequency of micturition, incontinence of urine and enuresis.

Sanjiao

The sanjiao is located "separately from the zang-fu organs and inside the body." It is divided into three parts: the upper, middle and lower jiao. Its meridian connects with the pericardium with which it is externally-internally related. Its main functions are to govern various forms of qi, and serve as the passage for the flow of yuanqi and body fluid. Yuanqi originates in the kidney, but requires the sanjiao as its pathway for distribution in order to stimulate and promote the functional activities of the zang-fu organs and tissues of the whole body. The chapter "Sixty-sixth question" of Classics on Medical Problems, therefore, says: "The sanjiao is the ambassador of yuanqi. It circulates the three qi and distributes them to the five zang and six fu organs."

The digestion, absorption, distribution and excretion of food and water are performed by the joint efforts of various zang-fu organs, including the sanjiao. The chapter "The thirty-first question" in the book of Classics on Medical Problems says: "The sanjiao is the passage of water and food." It is also mentioned in the eighth chapter of Plain Questions: "The sanjiao is the irrigation official who builds waterways."

The upper, middle and lower jiao combine with their related zang-fu organs, and each functions differently in order to carry out the digestion, absorption, distribution and excretion of water and food. The upper jiao dominates dispersion and distribution. In other words, in combination with the distributing function of the heart and lung, the upper jiao distributes the essential qi of water and food to the whole body in order to warm and nourish the skin and muscles, tendons and bones, and regulate the skin and pores. This function is described in the eighteenth chapter of Miraculous Pivot: "The upper jiao is like a fog." Here "fog" is used to describe the all-pervading vapour-like state of the clear and light essential qi of water and food.

The middle jiao dominates digestion of water and food. It refers to the functions of the spleen and stomach in digesting food, absorbing essential substance, evaporating body fluid, and transforming nutrient substance into nutrient blood. This function is described in the same chapter of Miraculous Pivot: "The middle jiao looks like a froth of bubbles", referring to the appearance of the decomposed state of digested food.

The lower jiao dominates the separation of the clear from the turbid and the discharge of fluid and wastes from the body. This process mainly involves the urinary function of the kidney and bladder, and the defaecation function of the large intestine. The same chapter also states: "The lower jiao looks like a drainage ditch." In other words, the turbid water continuously flows downward to be discharged. If the water passage in the lower jiao is obstructed, there may be urinary retention, dysuria and oedema.

Clinically, the terms upper, middle and lower jiao are often applied to generalise the functions of the internal organs of the chest and abdominal cavity. Above the diaphragm is the upper jiao which includes the heart and lung; between the diaphragm and umbilicus is the middle jiao which includes the spleen and stomach; and below the umbilicus is the lower jiao which includes the kidney, intestines and bladder.