Stomach — This muscular pouch lies on the left side in the upper abdomen. It is the continuation of the esophagus. Find the esophagus and locate where it pierces the diaphragm to join the stomach. This is the cardiac end of the stomach. The fundus is the dilated anterior portion; the body is the main portion, while the pyloric region is the most posterior. This end joins the duodenum.
The cardiac sphincter controls the entrance of food into the stomach from the esophagus. The pyloric sphincter at the posterior end regulates the release of partially digested food (chyme) into the duodenum. Look along the inner walls of the stomach and note the rugae, or folds which help to churn and mix the food with digestive juices.