I 8 10 Eggs At 12

Mnemonic

Count the letters in the structure to get the vertebral level:

• T8 - vena cava, 8 letters. In the central tendon, so it is held open
• T10 - oesophagus, 10 letters. In the right crus muscle, which pinches it
• T12 - aortic hiatus, 12 letters. Behind the diaphragm, so it is not pierced at all

Or “I ate ten eggs at twelve”: 8 vena cava, 10 oesophagus, 12 aorta.

The functional consequence follows the anatomy: the caval opening is in tendon so it widens on inspiration and venous return increases, while the oesophageal opening is in muscle so it narrows, which is part of the antireflux mechanism.

Expansion

Read it as I ate ten eggs at twelve:

• 8 - Inferior vena cava, at T8, through the central tendon
• 10 - Oesophagus, at T10, through the right crus of the diaphragm
• 12 - Aorta, at T12, behind the median arcuate ligament

The letter-count trick reinforces it in British spelling: oesophagus has ten letters and aortic hiatus has twelve.

Note that the three openings differ in nature. The caval opening is a true hole in the central tendon, the oesophageal hiatus is a muscular sling in the right crus, and the aortic hiatus is not really in the diaphragm at all; the aorta passes behind it. That is why the aorta is not compressed during inspiration while the inferior vena cava is actively held open.