6. What is the stomach?
The stomach receives food from the esophagus. As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. Your stomach is a sac-like organ with strong muscular walls located on the left side of the upper abdomen. In addition to holding food, it serves as the mixer and grinder of food. Its main function is to help digest the food you eat. The other main function of the stomach is to store food until the gastrointestinal tract (gut) is ready to receive it. You can eat a meal faster than your intestines can digest it. Your stomach makes acid and powerful enzymes that break the food down and change it to a liquid or paste. From there, food moves to your small intestine.
Digestion involves breaking food down into its most basic parts. It can then be absorbed through the wall of the gut into the bloodstream and transported around the body. The wall of the stomach has several layers. The inner layers contain special glands. These glands release enzymes, hormones, acid, and other substances. These secretions form gastric juice, the liquid found in the stomach. The stomach secretes acid and enzymes that digest food. The stomach muscles contract periodically, churning food to enhance digestion. The pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.