The Spleen has an arguably much bigger role in Chinese Medicine than in Western medicine. Its role is seen as 'transforming and absorbing' food and drinks, extracting Grain Qi (Gu Qi) and food Essence out of them, and distributing them to other Zang Organs.
Along with the Heart, the Spleen also has the function of controlling Blood inside Blood vessels. As such if a patient has blood in their urine or their stools, this is considered as a Spleen Deficiency.
Lastly the Spleen also 'governs' muscles and limbs. This is mainly due to its role in extracting nutrients out of what we eat or drink and transporting them to muscles and limbs to nourish them. If that role is not fulfilled properly, this will be seen in one's muscles and limbs because some of the muscles strength is lost.
The Spleen is said to 'open' to the lips and mouth. Concretely this means that a Spleen Deficiency can be seen from the observation of a patient's appetite or from the color and shape of the lips. Someones who lost their appetite or who cannot taste food anymore will probably be diagnosed with a Spleen Deficiency.
The partially digested food from the Stomach is transformed into Grain Qi (Gu Qi) by the Spleen. It then gets transported upwards to the Lungs where it is mixed with inhaled Clean Air. The mixture is called Gathering Qi (Zong Qi), Pectoral Qi or Nature Air Qi which then gets transported to the Heart where it is used to make Blood.
The refined parts of food, called ‘Food Essences’ or nutrition in the Western terms, are transported by the Spleen to various parts of the body so that all the Organs, limbs, bones, hair, and tendons are nourished. Therefore, Spleen is considered to provide the material basis for the whole body. It functions as the root of Qi and Blood making. Therefore, in order to tonify Blood and Qi, we tonify the Spleen.
If the Spleen transforms and transports food Essence and Qi properly, then digestion, appetite, absorption and bowel movements is normal. Otherwise, there may be poor appetite, indigestion, abdominal distention or pain, anorexia, lassitude, and loose stools.
Another function of the Spleen is to separate, transport, and transform water in the body. The fluids ingested are divided into usable (the pure) and unusable (the dirty) groups. The usable ones are 'raised' and distributed to the Lungs. The unusable ones are sent to the Small Intestines to be separated further.
This process happens at the same time as the Spleen transforms, transports, and distributes food Essence and Qi. They have an impact on each other. An imbalance in one will influence the other. If the Spleen's transforming function is poor, the Fluids can congeal to create Phlegm or cause edema. Therefore, whenever the body has Dampness or Phlegm, the Spleen may be one of the reasons and is treated.
The Spleen Qi has the tendency to ascend. Not only it transports Grain Qi up to the Lungs, but it also raises and holds the Organs in their places. If Spleen Qi is Deficient, chronic diarrhea can happen, together with prolapse of different Organs such as the Bladder, Stomach, Uterus, Kidneys and Anus.
The clear Yang is also said to be raised by the Spleen to the head. If the Spleen is in excessive Dampness, the clear Yang fails to ascend and it can lead to fuzziness and heaviness of the head.
The Spleen is the root of Blood in the body. The Spleen Qi is also said to keep the Blood flowing in vessels. When the Spleen Qi is weak, Blood can flee its pathways and result in hemorrhages, vomiting of blood, stool blood, blood under the skin, menorrhagia, uterine bleeding and potential chronic bleeding.
If the food Essences (nutrition) are properly transported by the Spleen throughout the body, the muscle tone is good, the muscles are strong and the limbs have the strength to move. If the Spleen doesn't function smoothly, the muscles become thin or weak, and the limbs get slack and the person feels tired.
The Spleen has a connection with the mouth and lips because the food digestion process starts with the mouth. If the Spleen is strong, people have a good appetite and the mouth is able to distinguish the five tastes. On the other hand, if the Spleen is weak, it leads to poor appetite, the inability to distinguish tastes or a sticky, sweet taste in the mouth and pale, dry lips.
The Spleen condition, especially the Spleen Blood, could be judged by the lips' color and appearance. The lips are rosy and moist if the Spleen Qi and Spleen Blood are strong. The lips are pale if Spleen Blood is Deficient. The lips are dry if Spleen Yin is Deficient. If the Spleen has excessive Heat, the lips are likely to be red and dry and have a sweet taste.
The Spleen controls the saliva secretion as it controls the mouth. Saliva’s function is to moisten the mouth and to aid digestion by mixing the food with fluids to ease digestion.
Yi is translated as Thought or Idea. It is the intellectual function of the body which includes absorbing and remembering information, focusing, studying, thinking, and organizing ideas. If Spleen Qi is strong, it is easy to study, to think, and to concentrate. If not, thinking can be fuzzy, memorization can be weak, and concentration is poor.
The Spleen is affected by worry, brooding, obsession, sympathy, and nostalgia. Indulgence in or prolonged experience of any of the above emotions causes poor digestion, gas, bloating, ulcers, decreased appetite, and Stagnation of Qi.
The Spleen loathes Dampness. If the Spleen's ability to transform and transport Body Fluids fails to function properly, Dampness can accumulate and cause urinary problems, vaginal discharges, abdominal distension, and Phlegm. On the other hand, excessive Dampness in the body can damage the Spleen function. Also, Dampness causes problems to the rising of Spleen Qi, results in a dull headache and a feeling of heaviness and muzziness.
Post-Heaven Qi and Essence is acquired via food and drink and various forms of stimulation, such as exercise or study. While Pre-Heaven Qi and Essence is inherited from parents at the time of conception. As such they can be compared with a Chinese Medicine version of DNA. The Spleen is the origin of Qi and Blood in the body.