Answer:
Three important structures pass through the diaphragm: the esophagus, and the two main blood vessels of the lower half of the body, the inferior vena cava, and the descending aorta. This is the opening for the inferior vena cava, the vena caval foramen. This is the opening for the esophagus, the esophageal hiatus.
How the esophagus pass through the diaphragm:
It originates at the level of the sixth cervical vertebra, posterior to the cricoid cartilage. In the thorax, the esophagus passes behind the aortic arch and the left main stem bronchus, enters the abdomen through the esophageal hiatus of the diaphragm, and terminates in the fundus of the stomach.