<P> The stomach (from ancient Greek στόμαχος, stomachos, stoma means mouth) 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). </P> <P> In humans and many other animals, the stomach is located between the oesophagus and the small intestine . It secretes digestive enzymes and gastric acid to aid in food digestion . The pyloric sphincter controls the passage of partially digested food (chyme) from the stomach into the duodenum where peristalsis takes over to move this through the rest of the intestines . </P> <P> In humans, the stomach lies between the oesophagus and the duodenum (the first part of the small intestine). It is in the left upper part of the abdominal cavity . The top of the stomach lies against the diaphragm . Lying behind the stomach is the pancreas . A large double fold of visceral peritoneum called the greater omentum hangs down from the greater curvature of the stomach . Two sphincters keep the contents of the stomach contained; the lower oesophageal sphincter (found in the cardiac region), at the junction of the oesophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum . </P> <P> The stomach is surrounded by parasympathetic (stimulant) and sympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles . </P>

Where is the esophageal section of the stomach found