Final answer:
The epigastric region contains the upper portions of the stomach, including the cardia, fundus, and part of the body, responsible for initial digestion. The esophagus and parts of the liver and duodenum also extend into the epigastric area.
Step-by-step explanation:
The epigastric region is primarily associated with the upper central portion of the abdomen, which is located just below the breastbone. An organ unique to this region is the stomach, specifically the upper portions such as the cardia, fundus, and part of the body. The stomach in the epigastric region is responsible for the initial stages of digestion, churning and mixing food with gastric juices due to its muscularis layer, which includes an inner oblique smooth muscle for this vigorous action.
In addition to these parts of the stomach, the esophagus terminates in the epigastric region as it connects to the stomach at the gastroesophageal junction. The liver also extends into the epigastric area, particularly the left lobe of the liver. The duodenum, as well, starts at the pyloric sphincter of the stomach and extends into the region, marking the beginning of the small intestine.