The Small Intestine, located in the mid-abdomen, is a long luminal organ whose upper end connects with the Stomach at the pylorus, and whose lower end connects with the Large Intestine at the ileocecal junction. The Small Intestine and Xin Meridians connect, creating an external–internal relation between them. The Small Intestine receives chyme from the Stomach and separates useful lucid material from turbid waste. It belongs to Fire in the Five Elements Theory.
The physiological functions of the small intestine
The Small Intestine receives the Stomach’s chyme and further digests it, assisted by Pancreatic juice transported by Pi. Pi then distributes the final Essence and useful water to all parts of the body, and transmits the waste to the Large Intestine for excretion as feces or to the Bladder as urine. The Basic Questions says, “The Small Intestine is the official in charge of receiving like a container, transforming and transporting” . A dysfunctional Small Intestine presents as anorexia, pain and distension in the abdomen, loose stools, and constipation.
The Small Intestine transforms, transports, absorbs, and separates useful lucid material from turbid waste. During the process it absorbs a great amount of water as directed by Pi-controlled water metabolism, and separates nutrients with the assistance of Shen-Yang and Heat. Should abnormal function of the Small Intestine occur, water and undigested food exit the body as diarrhea with scanty urine. This “dysfunction of the Pi controlling the water” is correctly treated by adjusting the relationship between the Small Intestine and Pi.
The meridians of Xin （心） and the Small Intestine are connected and the relationship can be noted in certain pathological situations. When Xin （心） has excess Fire, the Heat may be transmitted down to the Small Intestine through the meridians, resulting in dysphoria, a bitter taste, tongue ulcers, or oliguria. When the Small Intestine has excess Fire, Heat rising to Xin （心） through the meridians may result in fidgeting, a red tongue, and so on.
While Xin （心）-Qi helps the Small Intestine perform its separating function, the closest link between the two organs exists at the Spirit level. Here sufficient Small Intestine-Qi supports Xin （心）, promoting mental clarity and sound judgment. Like the Gall Bladder, the Small Intestine also helps one to make the right choices in life.
For example, Irritable bowel syndrome (IBS) is a disorder that leads to abdominal pain and cramping, changes in bowel movements, and other symptoms. IBS is not the same as inflammatory bowel disease (IBD). It is also known as gastrointestinal neurosis, and as the name implies, is easily influenced by emotional factors. Due to its complex syndrome, such as Liver depression with Spleen deficiency, stagnation of dampness refers to Qi stagnation, Spleen and Stomach weakness, Yang deficiency of the Spleen and Kidney, etc. We suggest that the Small Intestine-Taiyang meridian–Zang Xiang system be used and a differential treatment be followed. It is to adjust the balance within the system.