Final answer:
A hiatal hernia is a condition in which the stomach protrudes through the esophageal hiatus into the chest. It is caused by the shortening of the esophagus due to repeated muscle contractions. Symptoms include heartburn and acid reflux.
Step-by-step explanation:
A hiatal hernia is when the stomach herniates through the hiatus of the diaphragm into the chest. This condition results from continued shortening of the esophagus due to repeated muscle contractions. The esophagus is a muscular tube that connects the pharynx to the stomach and passes through an opening called the esophageal hiatus in the diaphragm. When the muscles of the esophagus contract, it propel food towards the stomach. However, in cases of a hiatal hernia, the stomach is displaced and protrudes into the chest through the esophageal hiatus, leading to symptoms like heartburn and acid reflux.