The spleen and the stomach are all located in the abdomen and pertain to the middle energizer, together governing the digestion and absorption of food and serving as the source of qi, blood and body fluid. That is why the spleen and the stomach are regarded as the "acquired base of life" in all the classics of TCM, the theory about which is known as "the theory of the spleen and the stomach".

The physiological relationship between the spleen and the stomach covers the following three aspects.

The spleen governs transportation and transformation while the stomach controls reception and digestion. This is what the coordination of the spleen and stomach in reception and transportation means. After being taken into the stomach, food is primarily digested in the stomach, making it possible for the transportation and transformation of the spleen; after being further digested in the spleen, food nutrients are absorbed by the spleen to meet the need of the stomach for further reception. Only when reception and transportation are well coordinated can normal digestion and absorption of food be ensured.

Spleen-qi governs the elevation of the lucid while stomach-qi controls the descent of the turbid, both of which restrict and assist each other. Through elevating the lucid the spleen transports food nutrients up to the heart and the lung; through descending the turbid the stomach moves the waste of food downwards. Without the descent of stomach-qi the waste of food will stagnate in the middle energizer, food nutrients cannot be transported to the other parts of the body and spleen-qi cannot rise; without the ascent of spleen-qi food nutrients cannot be transported upwards, leading to mixture of the lucid and the turbid in the abdomen and failure of stomach-qi to descend. Only when the ascent of spleen-qi and descent of stomach-qi coordinate with each other can digestion be normally carried on. That is why TCM holds that "ascent ensures normal function of the spleen and descent harmonizes the function of the stomach".

The spleen prefers dryness and dislikes dampness while the stomach prefers moisture and dislikes dryness. Mutual promotion between dryness and dampness indicates that the spleen and stomach physiologically promote each other. The preference and aversion of the spleen are just opposite to those of the stomach. The spleen is a zang-organ and pertains to yin in nature. It transports, transforms and elevates the lucid with the assistance of dryness of yang-qi. Dampness pertains to pathogenic factor of yin in nature, tending to encumbering the spleen and affecting the functions of the spleen to transport and transform food and elevate the lucid. That is why the spleen prefers dryness and dislikes dampness. 

The stomach is a fu-organ and pertains to yang in nature. With the moisture of yin-fluid the stomach digests and descends food. Dryness is a pathogenic factor of yang in nature, tending to damage stomach-fluid and affecting the functions of the spleen to digest and descend food. That is why the stomach prefers moisture and dislikes dryness. Physiologically yin-fluid in the spleen is beneficial to the digestion and downward transmission of food. Besides, dryness of yang-qi in the stomach is helpful to the spleen to transport and transform food and elevate the lucid. So the spleen and the stomach promote each other with dryness and dampness, playing a very important role in the digestion of food and absorption of food nutrients.

Since the spleen and the stomach are closely related to each other in physiology, clinically spleen disorder and stomach disorder tend to affect each other, frequently leading to spleen disorder involving the stomach and stomach disorder involving the spleen, consequently bringing on the symptoms of anorexia, stomach distension, abdominal distension, vomiting, belching and diarrhea, etc.