The gross anatomical organization of the digestive tract is shown in Figure 1. It includes the oral cavity with its salivary glands, the esophagus, the stomach, small intestine, and the large intestine and the rectum and anus of humans. Figure1 also illustrates the anatomical relationships between the stomach, liver, pancreas, gallbladder, and the common bile duct.
Fig1. Diagram of the human digestive system from the port-of-entry oral cavity to the exit at the anus. The total length of the digestive system in an adult is ~27 feet, or 4.5× the average height of 6 ft of an adult. The esophagus is ~10 inches in length. The small intestine is ~22–23 feet in length and the large intestine (the colon) is ~5 feet in length.
The digestive tube or alimentary canal in humans is an ~8-meter-long muscular tube extending from the lips to the anus. Figure 1 identifies the individual components of the alimentary canal; each part makes an essential contribution to the overall process of making ingested food ultimately available as relatively small molecules, e.g., amino acids, glucose, glycerol, fatty acids, etc., for all the cells of the body. The operations within the digestive tube are supplemented by several accessory organs, including the teeth, tongue, salivary glands, and pancreas, and liver secretions.
