The stomach is an important organ in the digestive system. After food has been chewed in the mouth and swallowed, it enters the stomach via the oesophagus. The stomach produces strong acid. This kills many harmful microorganisms that might have been swallowed along with the food. It also contains special chemicals called enzymes.
The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital digestive organ. In the digestive system the stomach is involved in the second phase of digestion, following mastication (chewing).
Conditions and diseases. The stomach can have many different conditions and diseases that can cause pain, discomfort, digestion problems and even death. One of the most common stomach problems is upset stomach or dyspepsia.