01 · A muscular mixing chamber
The stomach
After you swallow, food travels down the esophagus into the stomach — a stretchy, J-shaped muscular organ in the upper abdomen. Its walls contract in rhythmic waves to churn and mix food with gastric juices.
Those juices include acid and the enzyme pepsin, which begins breaking proteins into smaller pieces. Over a few hours, a meal is turned into a thick liquid called chyme, which the stomach releases a little at a time into the small intestine.
- Holds and mixes food after a meal
- Begins protein digestion with pepsin
- Releases chyme gradually into the small intestine

