This muscular tube transports food from the mouth to the stomach in wave-like contractions of the smooth muscle. It passes through the diaphragm to meet with the stomach, releasing food into the stomach via the lower esophageal sphincter.
The stomach has many muscular layers; these layers work together to churn food received from the esophagus, further breaking down the food into a semi-liquid form known as chyme. The mucosa and submucosa, which form the stomach’s inner lining, secrete gastric juices to aid digestion. The layers of stomach muscle contract and expand in order to mix and expel the stomach contents, while the outer layer of the stomach is smooth, allowing ease of movement.
The liver produces bile, which assists in the breakdown of partially digested food. The bile is sent from the liver to the gall bladder, where it is stored and concentrated ready for release into the duodenum.
Pancreatic enzymes are responsible for much of the digestive process carried out in the duodenum. The pancreatic enzymes and bile enter the duodenum through a common opening, the duodenal ampulla.
The small intestine consists of the duodenum, jejunum and ileum. The large intestine consists of the cecum, colon, rectum and anus. Most of the absorption of nutrients takes pike in the small intestine, while the colon extracts water and bile salts. All that then remains is feces which is sent on to the rectum for periodic evacuation via the anus.