The spleen and the stomach are the primary organs of digestion in Chinese Medicine. The Spleen is responsible for taking in the food, breaking it down and processing it, as well as distributing the nutrients. The Stomach is considered the “Sea of Grain and Water” and it is responsible for turning digested food into nutrients and absorbing them.
When digestion is working properly, the Spleen Qi (energy or life force) is flowing freely. It facilitates the overall digestive process. Spleen function is ascending in nature — the pushing action of the Spleen Qi is necessary to move the nutrients up into heart and lungs and is also responsible for holding all organs in place, while the descending action of the Stomach Qi serves to absorb nutrients and move the leftover waste down to the intestines where it is separated out and further absorbed or excreted from the body as liquid or solid waste. Stomach Qi can be thought of as “feeding” the other organs the nutrients they need to perform their special tasks.
When the Spleen Qi in your body is deficient, your digestion will most likely be sluggish with incomplete bowel movements, gas, bloating, and possible secondary symptoms of fatigue, foggy brain, heaviness in the limbs, and worry and over-thinking. If the Spleen Qi is not strong enough to push things forward, accumulation and stagnation will result in the Stomach, and also possibly in the Liver.
When your Stomach Qi is “rebelling”, the energy is moving up when it should be going down and through your digestive system. It is considered an excess condition and associated with fire, hence the burning sensation which comes with acid reflux, or the total upheaval of your system, i.e., vomiting.
Professor J.R. Worsley described the Stomach organ as being similar to a bakery. It receives all of the various ingredients and, if mixed and baked properly, will create a delicious cake. The Spleen on the other hand is like a fleet of trucks/drivers, working 24/7, that transport the cakes to the buyers/stores. Within our body, the Spleen organ transports and distributes the proper amount of nourishment to every cell and every level — physical and non-physical. We can easily imagine what would happen if the truck driver failed to show up for work or got lost making deliveries. Regardless of the quality and quantity of the food itself, if the transporter failed to deliver, some people would still starve while others might feel stuffed with far more than they need. 
So, if you have any issues with digestion, then it is most likely an issue with the function of the spleen and/or stomach.