Lesser diaphragmatic apertures
The lesser diaphragmatic apertures allow the passage of smaller structures from the thoracic cavity to abdominal cavity across the diaphragm. They are very much smaller than the other diaphragmatic apertures:
- two in the right crus of the diaphragm - transmit greater and lesser right splanchnic nerve
- three in the left crus of the diaphragm - transmit greater and lesser left splanchnic nerves as well as the hemiazygos vein
- under the medial arcuate ligament - usually transmit the sympathetic trunks
- under the lateral arcuate ligament - subcostal nerve and vessels
- left phrenic nerve pierces the dome of the left hemidiaphragm
A small interval exists between the sternal and costal parts of the diaphragm where the muscular fibers of the diaphragm are deficient and are replaced by areolar tissue and through which the superior epigastric branch of the internal mammary artery and some lymphatics from the abdominal wall and convex surface of the liver pass through.