What are the circular muscles that act as valves at the entrance and exit of the stomach called?

The circular muscles that function as valves at the entrance and exit of the stomach are known as sphincters. These muscles play a crucial role in controlling the passage of food and digestive contents from the esophagus into the stomach and from the stomach into the small intestine. At the entrance of the stomach, the lower esophageal sphincter prevents the backflow of stomach contents into the esophagus, helping to maintain a one-way flow of food. At the exit, the pyloric sphincter regulates the emptying of partially digested food into the small intestine.

Sphincters are essential for the proper functioning of the digestive system, contributing to the regulation of digestion and protecting the esophagus and intestines from harmful stomach acids and contents. Understanding the role of sphincters is important in the context of gastrointestinal health and disorders.