Final answer:
The esophageal hiatus is the opening in the diaphragm through which the esophagus penetrates to enter the abdomen.
Step-by-step explanation:
The point at which the esophagus penetrates the diaphragm is called the esophageal hiatus. The esophagus is a muscular tube approximately 25 cm (10 in) in length, running posterior to the trachea and enters the abdomen through this opening. The esophageal hiatus is one of three primary openings in the diaphragm, the others being the caval opening for the inferior vena cava and the aortic hiatus for the aorta, thoracic duct, and azygous vein.