The stomach is an organ of digestion. It has a saclike shape and is located between the esophagus and the intestines. The human stomach is a muscular, elastic, pear-shaped bag, lying crosswise in the abdominal cavity beneath the diaphragm. It changes size and shape according to is position of the body and the amount of food inside. The stomach is about 12 inches (30.5 cm) long and is 6 inches. (15.2 cm) wide at its widest point. The stomach's capacity is about 1 qt (0.94 liters) in an adult.
Food enters the stomach from the esophagus. The connection between the stomach and the esophagus is called the cardiac sphinter. The cardiac sphincter prevents food from passing back to the esophagus. Heart burn is the sensation when stomach juices (gastric juice) is allowed to seep through the sphincter into the esophagus. Once the food enters the stomach, gastric juices are used to break down the food. Some substances are absorbed muscle lining of the stomach. The other end of the stomach empties into the duodenum. The duodenum is the first section of the small intestine. The pyloric sphincter separates the stomach from the duodenum.
The stomach is composed of five layers. Starting from the inside and working our way out, the innermost layer is called the mucosa. Stomach acid and digestive juices are made in the mucosa layer. The next layer is called the submucosa. The submucosa is surrounded by the muscularis, a layer of muscle that moves and mixes the stomach contents. The next two layers, the subserosa and the serosa are the wrapping for the stomach. The serosa is the outermost layer of the stomach.
