How does heartburn occur?

Heartburn occurs when the sphincter separating the esophagus from the stomach is weak. When this sphincter is weak and does not keep the acid in the stomach, but instead allows the acid to travel up to the esophagus, this can cause a symptom called heartburn.

The epicenter of the heartburn problem is the juncture between the stomach and the esophagus, the gastroesophageal sphincter. During normal digestion this band of muscle relaxes to allow swallowed food to enter from the esophagus into the stomach and contract when it is done. The stomach contains gastric juices, hydrochloric acid and enzymes that begin the process of digestion. When the sphincter pressure is lax, it causes the backflow of acid into the esophagus. It can cause burning pain or worse, damage sensitive tissue not accustomed to coming into contact with caustic stomach contents.