Major openings of the diaphragm: lateral view

Case Discussion

Other than a few minor openings, there are 3 major openings in the diaphragm:

A:  The caval opening is at the level of T8, thereby making it the most superior of the major openings. It passes through the right leaflet of the central tendon of the diaphragm which makes its margins aponeurotic. The caval opening is transversed by the inferior vena cava and branches from the right phrenic nerve. Dilation of the caval opening during inspiration along with increased intra-abdominal pressure, increase cardiac venous return. 

B: The oesophageal opening is at the level of T10 and is situated to the left of the muscular part of the diaphragm. The opening contains the oesophagus and vagal trunks. The opening resembles an elliptical shape. The perioesophageal areolar tissue and the phreno-oesophageal ligament allow for the oesophagus to have free movement during deglutition and respiration while limiting the superior displacement of the oesophagus.

C:  The aortic opening is at the level of T12 and is situated most posteroinferiorly relative to the aforementioned openings. Calling it an opening in the diaphragm is a misnomer, as its contents pass posterior to the muscle of the diaphragm. The contents include the aorta, thoracic duct, and the azygos vein. The hemiazygos vein passes through the aortic hiatus or through its own minor opening in the left crus.