About the Stomach & Duodendum

The stomach, part of your digestive system, is a J-shaped organ located in the upper abdomen, under your ribs. The upper part of the stomach connects to the esophagus, and the lower part leads into the duodenum, the first part of your small intestine. Food and fluids enter your stomach from the esophagus by passing through the lower esophageal sphincter.

The stomach has several important functions:

  • As a storage bin. Your stomach stores swallowed food and liquid—this requires the muscle of the upper part of your stomach to relax and accept large volumes of swallowed material. The upper portion holds a meal and releases it a little at a time into the lower portion for further digestion.

    When your stomach is empty, it has a volume of less than one fourth of a cup, but it can expand to hold more than 8 cups of food after a large meal.
     
  • As a food mixer. The wall of your stomach is lined with three layers of strong muscles, which churn and mix food into smaller and smaller pieces.
     
  • As a digestive tub. Glands, which line the wall of your stomach, produce gastric juices, rich in acid and enzymes. The glands produce about 3 quarts of digestive juices each day. These help break down food into a thick, creamy fluid called chyme.
     
  • As a sterilizing system. In addition to breaking down food, gastric juices also help kill bacteria that might be in the food you eat.


Once the thick liquid called chyme is well mixed, muscle contractions propel it through the pylorus and into the first section of your small intestine (duodenum). The pylorus is a walnut-sized tube of muscle at the outlet of the stomach, which keeps chyme in the stomach until it reaches the right consistency to pass into the duodenum.

The pylorus releases less than an eighth of an ounce of chyme at a time, holding back the rest for more mixing. After chyme is squirted into the small intestine, digestion of food continues so the body can absorb the nutrients into the bloodstream.

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Last modified on: 30 June 2015

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