In anatomy, what is the name of the gap in the diaphragm through which the esophagus passes?

The gap in the diaphragm through which the esophagus passes is called the esophageal hiatus.

This oval opening lies in the muscular diaphragm, around the level of the tenth thoracic vertebra, or T10. The esophagus travels through it on the way from the thorax to the stomach. The opening also transmits the anterior and posterior vagal trunks, branches of the left gastric vessels, and lymphatic vessels.

The diaphragm’s crural fibers help form a functional valve-like sling around the esophagus. During inspiration, their contraction can help limit upward movement of stomach contents, working with the lower esophageal sphincter to reduce reflux.

The nearby openings are easy to confuse. The aortic hiatus, usually at T12, carries the aorta and thoracic duct; the caval opening, around T8, carries the inferior vena cava. A hiatal hernia occurs when part of the stomach pushes through the esophageal hiatus, potentially contributing to reflux symptoms.