The gastrointestinal system is the network of organs that allows a person to consume and digest food, extract nutrients, and expel waste. Also known as the gastrointestinal (or GI) tract, the system includes all bodily structures between the mouth and the anus, plus organs that aid in digestion. If it were to be stretched out, the human gastrointestinal system would be nearly 30 feet (9 meters) long.
From the mouth, the upper gastrointestinal system includes the esophagus, stomach, and the duodenum. The mouth is aided in digesting food by the salivary glands and the tongue. The esophagus is commonly thought of as the throat, leading to the stomach. The stomach secrets a number of enzymes, proteases and acids, that partially digests food before sending it to the intestines. Less than an hour after eating, about half of stomach contents are emptied into the intestines. The duodenum, also known as the Ligament of Treitz, is the division between the stomach and the small intestine.
The lower gastrointestinal tract consists of the small and large intestines. The small intestine can be subdivided into the duodenum, jejunum, and ileum, while the large intestine can be divided into the cecum, colon, rectum, and anal canal. The small intestine is responsible for absorbing digested foods and passing them into the bloodstream. The large intestine, the last part of the gastrointestinal system, absorbs water and stores the remaining waste, feces, before evacuation. The entire process from eating to defecating can take between 12 and 50 hours, depending on the individual.