- Box 1 is the upper esophagus sphincter
- Box 2 is the lower esophagus sphincter
The upper esophageal sphincter (UES) is a muscular ring at the upper esophagus, preventing air entry during breathing and relaxing for swallowing.
The lower esophageal sphincter (LES) is located at the esophagus-stomach junction, acting as a valve to prevent gastric reflux.
The UES regulates airflow and facilitates swallowing, while the LES safeguards against stomach content reflux into the esophagus.
Both sphincters contribute to respiratory and digestive functions, with the UES ensuring proper air passage and the LES maintaining a barrier between the stomach and esophagus to prevent acid backflow and protect esophageal tissues.