What Is the General Structure of the Gastrointestinal Tract?
For most of its length, the GI tract is a long hollow tube lined by different types of cells. The walls of the tube are composed of glands, nerves and muscles. Structurally, the cell type, muscle thickness, glandular elements, and nervous supply differ in the various functional regions, as does the diameter and shape of the tube. The esophagus is a rather straight tube that is lined with muscles that force food down the neck and through the chest towards the stomach. In a medium-sized dog it is about 15 to 18 inches long and an inch in diameter when collapsed. It is divided into cervical (neck), thoracic (chest), and abdominal portions. The stomach is a large sac-like dilatation of the GI track and is made up of several distinct areas. The inlet or opening from the esophagus into the stomach is called the cardia. The exit or outlet of the stomach that leads to the small intestine is the pylorus. The stomach is shaped somewhat like a large lopsided kidney bean that lies across the front
