Digestion is a complicated process that involves several structures and organs, including your mouth, esophagus, intestines and stomach. Collectively, the organs and structures that aid in digestion are referred to as the gastrointestinal, or GI, tract. Each part of your GI tract has an individualized role to play in digestion. The churning of your stomach ensures that partially digested food is broken down into absorbable nutrients.
Digestion takes two forms -- chemical and mechanical. Chemical digestion refers to the breakdown of food into absorbable nutrients by digestive juices and enzymes. Mechanical digestion is the physical breakdown of food through chewing, grinding, and muscular or rhythmic contractions. When your stomach churns, it’s using both types of digestion to make sure that partially digested food is small enough to enter the cells of your GI tract, blood and lymph tissue.
Your stomach produces a variety of digestive secretions that play a powerful role in chemical digestion. Among these digestive juices are hydrochloric acid, enzymes, mucus, gastrin and intrinsic factor, which is necessary for proper vitamin B-12 absorption. It is not enough for these digestive juices to just be present in the stomach, however; they must be thoroughly mixed with the partially digested food in your stomach. The churning of your stomach allows adequate mixing.
The churning of your stomach doesn’t just mix partially digested food with digestive juices. It also helps physically break down your food. According to “Nutrition and You” by Joan Salge Blake, this churning and mixing lasts for hours until the food is diminished enough to travel into the small intestine.
Once the stomach has transformed your food into a fairly liquefied state, the digested food is ready to move into the small intestine. The churning of your stomach helps to push this liquid material, called chyme, toward the lower part of your stomach. Once the chyme reaches the pyloric sphincter -- the muscular band that separates the stomach from the small intestine -- the muscles relax to let the chyme slowly enter the small intestine.