The Stomach is one of the six fu, paired with the Spleen in the Earth phase, and between them the two carry most of what Chinese medicine says about nourishment. The classical epithet for it is the sea of grain and water, and the division of labour with the Spleen is precise: the Stomach receives and rots down what is eaten, the Spleen transforms the result and moves it on.
Two further points make the Stomach more central than that description suggests. The first is the doctrine that the Stomach and Spleen together are the root of the postnatal, the source of all the qi and blood the body makes for itself after birth, as against the prenatal endowment stored by the Kidney. A tradition that regards the inherited portion as finite naturally puts great weight on the acquired one.
The second is the direction of movement. The Stomach qi is described as descending and the Spleen qi as ascending, and that opposed pair is one of the most frequently invoked ideas in the whole system, because the tradition explains a great deal by reference to a movement that has reversed.
The western scheme associates the stomach with Cancer and with the Moon, recorded separately. Neither account is a statement about gastric physiology and nothing here is guidance.