2.8. Structures Associated with the Diaphragm
The Three Structures Associated with the Diaphragm
The diaphragm has lots of structures passing through or around it, but at the minute you only need to remember three of these. Each structure crosses the diaphragm at a particular vertebral level. Make sure you remember the info here - these facts are often incorporated into exam questions!
*The oesophageal hiatus is formed between various stretching muscles and ligaments of the diaphragm. However, it does not pierce the muscle or central tendon of the diaphragm. The only structure to pierce the diaphragm is the inferior vena cava.
The thoracic aorta: passes behind the diaphragm at T12, via the aortic hiatus.
The oesophagus: passes between ligamentous layers (the right crus and the left crus) of the diaphragm at T10, via the oesophageal hiatus*.
The inferior vena cava (IVC): pierces the substance of the central tendon of the diaphragm at T8, via the vena caval foramen.
The diagram shown here has been sketched from a position below the diaphragm, so this is the inferior surface of the diaphragm.
It's easy to confuse the vertebral levels at which the structures cross the diaphragm. In an exam, don't panic - think about it logically and remember the key vertebral levels here: T8, T10 and T12. Let's match them up. The IVC is a big vein that runs slightly to the right of the midline and is closely associated with the liver (on the right). Because we know that the diaphragm is higher on the right, it is reasonable to think that the IVC pierces the central tendon of the diaphragm at a high vertebral level (T8). What about the oesophagus...what's it leading into? The stomach, which sits quite high up in the abdomen, but remember it's on the left - and the diaphragm is lower on the left. - let's go for T10. The abdominal aorta is by far the most posterior of the structures here and it has to give off the subcostal artery...which lies at T12!