The abdomen and chest are separated by a sheetlike muscle called the
esophagus passes through an opening (the hiatus) in
the diaphragm to connect to the stomach. A hiatal hernia occurs when part of
the stomach bulges out of the abdomen, through the hiatus, and into the chest.
When this happens, the
lower esophageal sphincter (LES) may move above the
Normally, pressure from the diaphragm muscle helps keep the LES valve
closed. When a hiatal hernia occurs, the valve is pushed above the diaphragm so
the diaphragm muscle can no longer help keep the valve closed. If the valve
stomach acid and juices from backing up into the
esophagus, symptoms of
heartburn may occur.