Final answer:
When stomach acid passes the Cardiac sphincter, it moves into the esophagus, leading to acid reflux or heartburn.
Step-by-step explanation:
If stomach acid moves up past the Cardiac sphincter, it ends up in the esophagus. The Cardiac sphincter, also known as the gastro-esophageal sphincter, is a ring-like muscle located at the stomach end of the esophagus. Under normal conditions, this sphincter allows food to pass from the esophagus into the stomach and prevents the acidic contents from traveling in the opposite direction.
When the sphincter fails to close properly, a condition known as acid reflux or heartburn occurs, allowing stomach acid to escape into the esophagus, causing discomfort and potential damage to the esophageal lining.