The idea that the spleen governs the muscles and the four limbs means that the muscles and the four limbs depend on the nutrients transported and transformed by the spleen to nourish. With the normal function of the spleen, sufficient qi and blood will be transformed from food nutrients; with sufficient nourishment, both the muscles and the limbs will become strong. If he function of the spleen is abnormal, the absorption of food nutrients will be reduced, leading to insufficient production of qi and blood and bringing on malnutrition of the muscles and the limbs with the symptoms of emaciation, lassitude of the limbs or even atrophy of the limbs.

The mouth is the starting point of the digestive canal. Since digestion is governed by the spleen, the mouth is the orifice into which the spleen opens. The idea that the spleen opens into the mouth means that the functional states of the spleen can be observed from the manifestations on the mouth. If the spleen is normal in function, the appetite and taste in the mouth will be normal; if the spleen is abnormal in function, it will lead to anorexia, no taste in the mouth, or greasy and sweet taste in the mouth.

   

The spleen opens into the mouth and the lips are the external parts of the mouth. So the functional states of the spleen can be observed from the color and shape of the lips. If the spleen is normal in function, qi and blood will be sufficient, and the lips will be ruddy and lustrous; if the spleen is abnormal in function, qi and blood will become scanty, and the lips will be pale, lusterless or even sallow.