20.5: Esophagus and Stomach
- Page ID
- 53820
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Above: After the oral cavity and pharynx, the gastrointestinal tract (alimentary canal) is next comprised of the esophagus, stomach, and small intestine (duodenum, jejunum, and ileum).
The Esophagus
Sphincters, typically composed of a circular muscle, regulate the movement of digesting materials through the alimentary canal. The first sphincter the bolus passes through is the upper esophageal sphincter at the pharynx-esophageal transition. This sphincter prevents air from entering the esophagus and prevents reflux of materials within the esophagus into the pharynx. A lower esophageal sphincter is present where the esophagus meets the stomach. The lower esophageal sphincter relaxes to let a bolus into the stomach and contracts to prevent regurgitation of stomach contents into the esophagus.
Above: Histology of the esophagus, magnified by 10x.