Any type of hernia occurs when a part of an organ pokes through a tear that appears in the muscles near it. In the hiatal hernia's case, the upper side of the stomach gets in the chest through an opening in the diaphragm called the hiatus. The diaphragm is the muscle that separates the thoracic cavity from the abdomen, and the hiatus is an orifice in the diaphragm through which the esophagus passes in order to reach the stomach.
When hiatal hernia appears,